On the Exact Solution of the Multi-Period Portfolio Choice Problem for an Exponential Utility under Return Predictability In this paper we derive the exact solution of the multi-period portfolio choice problem for an exponential utility function under return predictability. It is assumed that the asset returns depend on predictable variables and that the joint random process of the asset returns and the predictable variables follow a vector autoregressive process. We prove that the optimal portfolio weights depend on the covariance matrices of the next two periods and the conditional mean vector of the next period. The case without predictable variables and the case of independent asset returns are partial cases of our solution.Furthermore, we provide an empirical study where the cumulative empirical distribution function of the investor's wealth is calculated using the exact solution. It is compared with the investment strategy obtained under the additional assumption that the asset returns are independently distributed. Investment analysis and portfolio choice theory are very important and challenging topics in finance and economics nowadays. Since Harry Markowitz (1952) presented his mean-variance paradigm portfolio theory has become a fundamental tool for understanding the interactions of systematic risk and reward.. It is well known that the mean-variance optimization problem of Markowitz (1952) is equivalent to the expected exponential utility optimization under the normality assumption (see Merton (1969) ). Unfortunately, his approach only gives an answer to the one-period portfolio selection problem in discrete time but it says nothing about the multi-period (long-run) setting.. Therefore, it is of importance to investigate the multi-period portfolio optimization problem which is of great relevance for an investor as well. The multi-period portfolio selection problem has been analyzed for different types of utility functions by, e.g., Mossin (1968) , Merton (1969 Merton ( , 1972 , Samuelson (1969) , Elton and Gruber (1974) , Brandt and Santa-Clara (2006) , Basak and Chabakauri (2010) .. The continuous case has already been solved for many types of utility functions in the one-and multi-period case by Merton (1969) Exact solutions in discrete time are even more difficult to obtain in the multi-period case. Mossin (1968) considers the case of one risk and one riskless asset. He derives conditions when the multi-period strategy becomes myopic or partial myopic. Frequently this can be achieved by demanding independent asset returns. However, the assumption of independence is unfortunately not fulfilled in many applications.. For an investor it would be very useful to have a closed-form solution of the discrete multiperiod portfolio problem. Moreover, it is desirable that the optimal portfolio weights can easily calculated at each period. Analytical solutions of the multi-period optimal portfolio choice problems are hard to obtain and they are only available for some partial cases which are often derived under very restrictive assumptions on the distribution of the asset returns.. For instance, a closed-form solution for the multi-period portfolio choice problem exists for the quadratic utility function under the assumption that the asset returns are independently distributed (see Li and Ng (2000) , Leippold et al. (2004) ).. In the present paper we consider an investor who invests into k risky assets and one riskless asset with an investment strategy based on the exponential utility function. Here W t denotes the investor's wealth at period t and α > 0 stands for the coefficient of absolute risk aversion (ARA), which is a constant over time for the exponential utility (CARA utility). The application of the exponential utility function is more plausible than the use of the quadratic utility since the first one is monotonically decreasing. That is why the exponential utility function is commonly used in portfolio selection theory. Moreover, the optimization of the expected exponential utility function leads to the well known mean-variance utility maximization problem and consequently its solution lays on the mean-variance efficient frontier.. We derive a closed-form solution of the multi-period portfolio choice problem with the exponential utility function (1) under the assumption that the asset returns depend on certain predictable variables. The joint process consists of the asset returns and the predictable variables and it is assumed to follow a vector autoregressive (VAR) process. This approach is very popular in finance and it is often used for modeling the asset returns (see, e.g., Campbell (1991 Campbell ( , 1996 , Barberis (2000) , Brandt (2010) ).. The rest of the paper is organized as follows. In Section 2, the main result of the paper is given. In Theorem 1 an analytical expression of the portfolio weights is provided for each period. In Corollary 1, the case without a predictable vector is considered while independent asset returns are treated in Corollary 2. In Section 3 a short empirical study is presented. The performance of the derived strategy is compared with the one for independent asset returns.. The comparison is performed in terms of the cumulative empirical distribution function of the investor's wealth at the end of the investment period. We find significant improvements if the dependence structure is taken into account. Section 4 contains a short summary.. 2 Multi-Period Portfolio Problem for an Exponential Although the first formulation of the multi-period portfolio choice problem was already provided by Markowitz (1952) , there are only a few results on closed-form solutions available in literature. They are mostly derived under the assumption that the asset returns are independently distributed. Merton (1969) discovered that the maximization of the exponential utility function for normally distributed returns is equivalent to the maximization of the mean-variance utility function. Ç anakoglu andÖzekici (2009) obtained a closed-form solution for the exponential utility function under the assumption that the asset returns are independent. In general, the derivation of an analytical solution of the multi-period portfolio choice problem with the exponential utility for discrete time was considered to be very difficult (see, e.g., Soyer and Tanyeri (2006) ).. In the present paper we derive an exact solution of the multi-period portfolio selection problem for an exponential utility function which is obtained under the assumption that the asset returns and the vector of predictable variables follow a vector autoregressive process of order 1. Under the assumption of independence the obtained expressions of the weights are proportional to the weights of the tangency portfolio obtained as a solution in the case of a single-period optimization problem. We show that only the coefficient of absolute risk aversion depends on the dynamics of the asset returns in this case. The weights of the optimal portfolio derived without a vector of predictable variables are obtained as a partial case of the suggested general solution. In an empirical study we compare the derived multi-period portfolio strategies for real data taking five developed stock market indices. A very good performance of the general solution is observed which always overperforms the weights derived under the additional assumption that the asset returns are independent.. The obtained results can be further extended by taking into account the uncertainties about the parameters of the data generating process. The analytical expressions of the weights can be used to derive the expected mean vector and the covariance matrix of the estimated weights which provide us the starting point for the detailed analysis of their distributional properties.. This problem is not treated in the present paper and it is left for future research.

O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O B I I O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Are judgments for action verbs and point-light human actions equivalent? Abstract The aim of the present study was to examine whether the ability to judge action words and the ability to judge human actions share common mechanisms. With this purpose in mind, we proposed both a lexical and an action decision task to twenty-four healthy participants. For both tasks, the participants had to judge whether the stimulus that was presented (a letter string or a point-light sequence) was valid or not (i.e. a word vs. a pseudo-word, an action vs. a pseudo-action). The data analysis showed that the action decision task has common characteristics with the lexical decision task. As for verbal material, judgements of pseudo-actions were slower than judgements for actions. Moreover, we demonstrated that the ability to judge an action verb was positively correlated with the ability to judge a point-light human action, whereas no significant correlation appeared between nouns and point-light judgements abilities. This dissociation supports the argument that the judgement of action words and the judgement of human actions share a common but specific basis through the involvement of motor representations. ''Embodied theory'' suggests that high-level cognitive processes are based on sensorimotor experience (Barsalou 1999; Wilson 2002) . In this context, a lot of works have shown that sensorimotor processes are involved during tasks implying semantic representations and/or processing (for a review, see Andres et al. 2008; Coello and BidetIldei 2012; Fischer and Zwaan 2008) . In the present study, we are particularly interested in the importance of motor processes in language understanding. In this framework, several studies have shown that language processing can influence ongoing motor performance (Boulenger et al. 2006; Gentilucci 2003; Glover and Dixon 2002; Nazir et al. 2008) . For example, processing action words interferes with the production of reaching movements when the two tasks occur at the same time (Boulenger et al. 2006) . Interestingly, it has been suggested that these effects are not the consequence of the conscious processing of the word . Indeed, presenting an action verb to a participant at a subliminal level during the preparation of a reaching movement was found to affect the kinematic parameters of the motor response. These findings demonstrate that action words can automatically influence motor processes even when the words are processed out of the consciousness. Interestingly, a recent study showed automatic bidirectional relationships between the production of an action word and the production of a human action (Liepelt et al. 2012) . When people have to open or close their hand, their response times increased when an incongruent action word was previously presented. In the same manner, when people have to pronounce action words, their response times were higher when an incongruent action was previously presented. This bidirectional effect was also sustained by cortical recordings in motor and language areas (Aravena et al. 2010; Ibanez et al. 2013) . Actually, Ibanez et al. (2013) have shown that language areas activity is affected when a current action is realized during the processing of action-related sentence and reciprocally, sentence processing affects motor cortical activity in premotor and primary motor cortex.. Studies of cerebral activations have equally provided arguments in favour of crosstalk between language and motor processes. Similar regions that include motor areas are activated when humans have to produce actions or have to pronounce action words (for a review, see Pulvermüller 2013) . However, this cerebral network could encompass a large cortico-subcortical network which is not restricted to somatotopically defined brain areas Ibanez et al. 2013) . Additional evidence comes from clinical reports that have shown a close link between movement disorders (e.g. Parkinson's disease, Huntington's disease, progressive supranuclear palsy) or lesions in the motor brain areas and language impairments when processing action words (Bak et al. 2001; Cardona et al. 2013; Cotelli et al. 2006; Peran et al. 2003 Peran et al. , 2004 . For example, when patients suffering from Parkinson's disease are off-dopa (i.e. without dopaminergic treatment), the presentation of a verb as a prime does not facilitate the subsequent judgment of an identical verb, but this facilitation occurs in healthy controls and on-dopa patients ). This effect confirmed that the integrity of the brain motor system is essential for action word processing (see also Cardona et al. 2013) .. In the present experiment, contrary to previous studies that investigated the influence of action words processing on action production, and reciprocally, we mainly focused on the hypothesis that both tasks share common sensorimotor representations and are based on similar mechanisms. Some studies have effectively suggested that understanding action words could be related to motor processing as well as to other functions that request motor representation, such as the visual judgments of human action (Aziz-Zadeh et al. 2006) . In this context, Springer and Prinz (2010) showed that semantic processing affects the ability to predict whether a static image shows a coherent continuation of a human action sequence that is partially occluded. Given that the ability to predict the result of a human action is linked with action simulation (Chary et al. 2004; Graf et al. 2007; Martel et al. 2011) , this effect suggests the existence of a relationship between action semantics and sensorimotor representations (see also Springer et al. 2012 ). In the same vein, Bidet-Ildei et al. (2011) clearly showed that the perceptual judgement of a human action can be facilitated by prior exposure to an action-related word. When participants had to discriminate a point-light running movement embedded in a mask, they were faster when they were previously exposed to the verb ''run'' in comparison with non-congruent action verb (i.e. throw) or neutral verb (i.e. think). Implication of motor representations is also sustained at a neurophysiological level by demonstrating that the superior temporal sulcus (STS), a cerebral area that is specifically activated during the observation of human movements, is also activated during the generation of sentences that implicate action verbs (Khader et al. 2010) .. Overall, the previous studies suggest that action-related language and action observation share common motor representations and are based on similar mechanisms. However, no study has thoroughly investigated this assumption, and this was the aim of the present work. More specifically, we aimed to test whether action word understanding and visual judgements of human actions share common mechanisms. For this purpose, the present study on healthy participants used two independent tasks, one implying the recognition of words (i.e. lexical decision task) and one implying the recognition of actions (i.e. action decision task). In the lexical decision task, the participants had to judge whether a letter string represented a valid French word. In the action decision task, the participants had to decide whether a point-light sequence represented a valid human action. Consequently, in both tasks, participants have to judge whether a set of signals (i.e. letters in the lexical decision tasks and point-light in the action decision task) represents or not something known (i.e. a word in the lexical decision task and an action in the action decision task). Therefore, from a methodological point of view, both tasks are very similar. If the action decision task shares common mechanisms with the lexical decision task, we should observe common characteristics on the processing of the two tasks. Specifically, both tasks should be perturbed (i.e. higher response time and/or less accuracy) by pseudo-material. Note that although the effect of pseudo-words is known in the language literature, no study has yet examined the effect of pseudo-action judgements. Moreover, correlational analyses between the lexical decision task and the action decision task should highlight the specific relationship between action words understanding and action observation. Specifically, we predict that the ability to judge action verbs should be related to the ability to judge point-light actions, whereas the ability to judge nouns (i.e. non-action words) should be unrelated to the ability to judge point-light actions. The present study aimed to determine whether pointlight actions judgements and action words judgements share specific common mechanisms by comparing the behavioural performances in tasks that involve judgments of point-light actions (action decision task) or judgments of letter strings (lexical decision task).. The following lines summarize the main findings. Evidence for a significant difference between the judgments of pseudo-stimuli and valid stimuli was found in the lexical and action decision tasks for both accuracy and response times. In both tasks, the performance was better when the stimuli were valid (words or point-light human action) that when they were non-valid (pseudowords and pseudo-actions). Concerning the lexical decision task, our results are in line with the literature in language, which shows that pseudo-words are more difficult to judge than words (Grainger and Jacobs 1996) . In the present study, we obtained similar effects on both correct responses and response times for actions and pseudo-actions judgments. Interestingly, our pseudo- Fig. 2 Mean accuracy (a) and response times (b) according to the stimulus category (nouns, verbs, action) and the stimulus type (valid, pseudo). The error bars indicate one standard error. An asterisk indicates a significant difference, with p \ 0.01. Graphs have been made from the inverse arcsine and log transformations for the accuracy and the response time, respectively actions displayed the human kinematics of action but had random location departures. Consequently, as with the pseudo-words, the pseudo-actions were very similar to the valid actions. This finding suggests that judgment of pseudo-words and judgment of pseudo-actions are subject to similar constraints.. However, the present experiment indicates that action and words are treated differently in some aspects. Specifically, correct responses are lower and response times higher for actions than words. Following the known neurophysiological dissociation between occipito-temporal and occipito-parietal visual streams (Goodale 1998) , the difference between words judgements and actions judgements could be related to a pure neurophysiological dissociation where words could be preferentially treated in the ventral stream (e.g. Dehaene et al. 2005) , whereas actions could be preferentially treated in the dorsal stream (e.g. Gilaie-Dotan et al. 2011) . Moreover, we can also advance a role of the task's difficulty. Indeed, the analysis of several dynamic points required in the action decision task is more attentional consuming than the analysis of static letters required in the lexical decision task. It is also possible that participants are more familiar with words judgements than point-light actions judgements. Finally, the difference could be related to the choice of our stimuli. Actually, we decided to use 2D presentation of words and actions. However, if 2D presentation of words is classical, humans are more frequently exposed to 3D than 2D human actions in daily life. This could potentially explain the difference obtained in accuracy and response times between the words and action judgements. Nevertheless, it is unlikely that 3D action presentation would affect our results because recognition of 2D point-light human movements is known to be very performant in humans (Johansson 1973 ) and predisposed at birth in vertebrates (Simion et al. 2008; Vallortigara et al. 2005) . This point should be assessed in future experiments.. Importantly, the correlation analysis reveals a significant relationship between the response times to the verbs and the response times to the point-light human actions. Note that no such relationship appears with nouns. To account for this relationship between action verbs and point-light judgements, we can envisage that motor activation is implicated in both tasks. Classically, the judgment of pointlight actions is known to engage the motor system (BidetIldei et al. 2010; Casile and Giese 2006) . For example, at the neurophysiological level, some experiments have shown that motor cerebral circuits, such as those observed in the dorsal premotor, supplementary motor, middle cingulate, somatosensory (BA3, BA2, and OP1), superior parietal, middle temporal cortex and cerebellum, are activated during the observation of human actions (mirror neuron system, e.g. Gazzola and Keysers 2009) . At the neuropsychological level, patients who present with motor deficits have difficulties judging human actions (e.g. Chary et al. 2004) . Finally, at the behavioural level, visual preferences for human movements are based on the same spatial-temporal regularities as action production (e.g. Bidet-Ildei et al. 2006) . Therefore, the specific correlation obtained in the present experiment between the judgments of action verbs and the judgments of point-light action is in favour to a common processing based on sensorimotor representations. Moreover, this finding is in line with the previous experiments that demonstrated that action word understanding is functionally related to the motor system (see Fadiga et al. 2009 for review; Fischer and Zwaan 2008; Jirak et al. 2010) . However, as previously demonstrated in the literature Khader et al. 2010; Marangolo et al. 2012) , in the current experiment, we show that action production is not essential to mediate the action-semantic relationship. Indeed, we provide evidence that a direct relationship exists between action observation and action word understanding, which suggests than motor representations are most essential than pure motor production in the action-language relationship.. Our interpretation between action recognition and action word recognition accords with the representational view of embodiment, which suggests that processing of actionrelated words is grounded by the activation of brain's motor areas representing motor actions . It is also in accordance with the recent works in neuropsychology that showed that action observation is sufficient to facilitate verb recovery in aphasic patients (Marangolo et al. 2010 (Marangolo et al. , 2012 . One explanation for this effect could be that both the judgments of action words and the visual judgments of point-light actions are based on a similar action simulation processing. This idea has been evoked in some works Marangolo et al. 2012) and is related to the theoretical viewpoint that postulates that action words can serve to implicitly prepare the individual for future actions, similar to action observation (Barsalou 2009; Willems et al. 2010) . This is finally in line with a recent study that demonstrated that the ability to imagine action is related to the ability to recognize point-light biological motions (Miller and Saygin 2013) . At a neurophysiological level, the STS or the extrastriate body area could constitute common structures both activated for action words and action observation processing. This neurophysiological hypothesis is in agreement with studies which demonstrate specific activations in these areas when human evoked human action verbs (Lin et al. 2011) or heard action sentences (de Vega et al. 2014 ). However, it should be assessed in the future experiments.. To conclude, the present experiment demonstrates for the first time, at a functional level, the existence of similar mechanisms between action words and action observation processing. Similar to pseudo-words, the judgements of pseudo-actions induce response times increase and accuracy decrease. Moreover, the correlational analysis shows a direct relationship between the treatment of action verbs and the treatment of human actions. Crucially, the ability to judge point-light human actions is specifically related to the ability to judge action verbs consistent with the existence of common processing between the two tasks. Altogether, these findings argue in favour of ''embodied theory'' suggesting that action observation and action words judgements share common properties through the involvement of common motor representations (Bidet-Ildei et al 2011; Khader et al. 2010

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O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 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O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O 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A survey on maritime fleet size and mix problems This paper presents a literature survey on the fleet size and mix problem in maritime transportation. Fluctuations in the shipping market and frequent mismatches between fleet capacities and demands highlight the relevance of the problem and call for more accurate decision support. After analyzing the available scientific literature on the problem and its variants and extensions, we summarize the state of the art and highlight the main contributions of past research. Furthermore, by identifying important real life aspects of the problem which past research has failed to capture, we uncover the main areas where more research will be needed. As the first decade of the third millennium ended with a worldwide financial and economic crisis, several countries experienced a decrease in their gross domestic product. In 2009 the world trade fell by 22.9% compared with the year before, the deepest fall in 70 years, and this strong downturn also affected seaborne volumes, which decreased by 4.5% (UNCTAD, 2010) . Looking beyond the recent downturn, maritime economics has always been characterized by a cyclic repetition of peaks and troughs in demand and freight rates. While the demand of maritime transportation reacts quickly to changes in freight rates, the supply adapts slowly to changes in demand, mostly because of the long lead time associated with the acquisition of new ships. Imbalances between supply and demand are therefore common. This can be illustrated by the fact that in 2009 the world fleet grew by 7% over the year before, a growth that continued also in the beginning of 2010, despite the reduction in trade volumes. The tonnage oversupply was the result of orders for new ships submitted before the downturn. One often sees that in a trough, the tonnage is renewed, while in a peak one tends to postpone the demolition of older ships. Illustrating this pattern, a 300 % increase in demolitions of old tonnage was observed during 2009 (UNCTAD, 2010) .. These dynamics are one of the main triggers of the wave-motions in freight rates which are typically referred to as shipping market cycles. They can be described as the overlapping of three different cycles (Stopford, 2009 ):. 1. long-term cycles, typically driven by major changes in the industries of seaborne commodities, 2. short-term cycles, which mainly follow the evolution of the world economy, and 3. seasonal cycles, characteristic of many seaborne commodity trades (e.g. agricultural ones).. Shipping companies operate in such an uncertain and changeable environment, and a crucial strategic decision is that of designing an optimal fleet of ships. In its basic version the maritime fleet size and mix problem (MFSMP) consists of deciding how many ships of each type to use in order to meet the demand. The objective is typically to minimize the total cost of setting up and operating a fleet of ship and usually the problem includes ship routing or deployment decisions to support the tonnage estimation.. An example of an objective function for a basic version of the MFSMP is given in (1), and consists of a fixed term associated with the acquisition of ships and a variable term associated to their operations. . Here, V is the set of available ship types and R v represents the set of routes r that a ship of type v can sail. In the first term of (1) C F v represents the cost of including a ship of type v in the fleet, while variable y v represents the number of ships of type v to include. In the second term, C V vr represents the cost of sailing route r with ships of type v and decision variable x vr represents the number of times route r is sailed by ships of type v.. To ensure feasibility of the fleet operations, constraints need to keep track of the consumption of resources associated with the ships. Constraints (2) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 provide an example, where Z vr is the time consumed every time a ship of type v sails route r, and Z represents the total amount of time available for each ship within the planning horizon. In some applications, other resources than time, such as the number of available ships of a type, may be modeled in a similar way.. Finally, constraints are needed to ensure that ship operations are performed to meet the demand. Constraints (3) represent an example of such constraints ensuring that each port (or region) i ∈ N is called at least D i times during the planning horizon. The parameter A ir is equal to 1 if route r calls port i, and is equal to 0 otherwise. Ships have to sail each route a number of times sufficient to meet the frequency requirement for each port. Alternatively, or in addition to constraints (3), one may want to control the amount of cargo shipped to each port. In this case, let D i be the demand of port i and Q v the capacity of a ship of type v. Constraints (3) could then be modified by multiplying the argument of the summation in the left-hand side by parameter Q v . The left-hand side would then represent the total amount of cargo shipped to port i. However, the type of ship operations is very much dependent on the specific problem and may vary substantially from one problem to another. Therefore, different or additional restrictions might be wanted.. Finally, a typical mathematical model includes restrictions on the variables domain, where variables of type y v are usually restricted to take integer values while the restrictions put on variables of type x vr depend on the specific problem.. In this paper we present a literature survey on the MFSMP and its variants and extensions. Based on the survey, we discuss the state of the art and point out possible directions for future research within the subject. The remainder of this paper is organized as follows. In Section 2 we give a more thorough motivation for the survey. The relevant literature is examined in Section 3. In Section 4 the state of the art is discussed and future research perspectives are pointed out. Concluding remarks are given in Section 5. Due to the changeable and stochastic behavior of the seaborne economy, decisions on the composition of the fleet of ships are crucial in maritime transportation. Furthermore, frequent tonnage imbalances call for better decision support systems. We surveyed the available literature on the maritime fleet size and mix problem and discussed the state of the art on the decision support for such problem. We pointed out the available methodologies and the characteristics of the problems they are devised for. Furthermore, we highlighted points of weakness, where the available methodologies fail to capture important real life aspects of the problem and suggested possible future research directions to enhance the state of the art.. The available research papers have been focusing on shipping systems which can be considered as static and not characterized by volatility. They 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 have also well addressed the start-up of new shipping systems. However, important aspects of real life problems deserve further attention. Future research should especially focus more on the renewal of the fleet where the continual adaption of the fleet to changes in the market situation is sought. Important characteristics of the problem to better take into account are the uncertain market behavior and the large number of alternative ways for the shipping companies to renew their fleet. Furthermore, open research questions can be found, such as the appropriate description of the operations of the ships and opportune methodologies to include and tackle uncertainty. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65

O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


On the use of neighbourhood-based non-parametric classifiers Alternative non-parametric classification schemes, which come from the use of different definitions of neighbourhood, are introduced. In particular, the Nearest Centroid Neighbourhood along with the neighbourhood relation derived from the Ž . Gabriel Graph and the RelatiÕe Neighbourhood Graph are used to define the corresponding k-Nearest Neighbour-like classifiers. Experimental results are reported to compare the performance of the approaches proposed here to the one obtained with the k-Nearest Neighbours rule. q 1997 Elsevier Science B.V. Classification is a problem consisting of implicitly or explicitly generating decision boundaries which can successfully distinguish the distinct classes usually in a d-dimensional feature space. So, classification in pattern recognition has traditionally been tackled through two alternative approaches; namely, Ž parametric and non-parametric Duda and Hart, . 1973 . While the parametric classifiers assume a Ž . known functional distribution of given samples, the non-parametric approaches do not assume any particular distribution of the set of prototypes.. Although the parametric approaches have theoretically been shown to be potentially capable of yielding optimal results, in practice, they often tend to Ž . Fundacio Caixa-Castello and AGF95-0712-C03-01 and TIC95-Ž . 676-C02-01 Spanish CICYT .. actually fail because of inappropriate assumptions of a priori distributions.. Among non-parametric methods, those which are based on sample-to-sample distances are particularly remarkable and, in particular, the family of k-Nearest Ž . Ž Neighbours k-NN techniques Duda and Hart, . 1973 is often used in practice. When applied to classification, these schemes require the classes to be represented by appropriate sets of prototypes and the decision rule is generally reduced to label each given sample with the class that contains most of its knearest neighbours. It is the conceptual simplicity of such a rule, along with its asymptotical trend towards the Bayes rule in terms of minimum classification error, that makes the k-NN approach particularly appealing in many practical situations. Nevertheless, when the number of prototypes in the training set is not large enough, the k-NN rule is no longer optimal. This problem becomes more relevant when having few prototypes compared to the intrinsic dimensionality of the feature space, which is a very usual practical situation. Toussaint, 1992 are used. This paper is organised as follows. Section 2 introduces the already mentioned neighbourhood definitions. The resulting classification rules as well as conceptual differences with respect to the k-NN rule are provided in Section 3. Furthermore, a comparative study of the application of different non-parametric classification approaches in some critical situ-Ž ations that is, few prototypes andror high dimen-. sionality of the feature space is presented in Section 4. Finally, Section 5 summarises the main results of the paper and gives some concluding remarks. Ø The ith neighbour, q , i 0 2, is such that the i centroid of this and previously selected neighbours, q , . . . ,q is the closest to p.. This definition gives rise to a neighbourhood in which both closeness and spatial distribution of neighbours are taken into account because of the centroid criterion. The application of the NCN instead of the NN has already been proven to be very Ž useful in some representation problems Chaudhuri, . Sklansky: Can you provide an intuitive explanation for these results. How do you explain the success of your results? Sanchez: We think that this better behaviour of thé surrounding approaches is because the classifiers take into account not only the proximity but also geometrical information of the neighbourhood of a sample.. Kamel: How do you explain the results of the first experiment, in which the Gabriel neighbours rule did best?. Sanchez: This can be explained by the distribution of the samples in this particular problem. And also by the characteristics of the overlap among classes. However, in all other real databases it is systematically the worst option. The reason why the Gabriel neighbours rule is systematically the worst is because there are too many neighbours in this kind of graph. But in the case of the artificial database in the first experiment, we have a distribution that is not so affected by the large number of Gabriel neighbours.. Raghavan: The rule that you use to decide which neighbours are close according to the Gabriel graph and the relative neighbourhood, was it based on the Euclidean distance, and have you tried to work with other ways of defining distance? The cityblock distance would be an alternative.. Sanchez: We have used only the Euclidean distance.. Raghavan: I think that when you change the way distances are defined, this neighbourhood will change in very dramatic ways. And I think that you have to ( )look at the interaction between your definitions and the distance function that is used.

O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


A Generalized Construction of OFDM M-QAM Sequences With Low Peak-to-Average Power Ratio A construction of 2 2n -QAM sequences is given and an upper bound of the peak-to-mean envelope power ratio (PMEPR) is determined. Some former works can be viewed as special cases of this construction. Multicarrier communications have recently attracted much attention in wireless applications. The orthogonal frequency division multiplexing (OFDM) has been employed in several wireless communication standards. Their popularity is mainly due to the robustness to multipath fading channels and the efficient hardware implementation employing fast Fourier transform (FFT) techniques. However, multicarrier communications have the major drawback of the high peak-to-average power ratio (PAPR) of transmitted signals. Please refer to Litsyn [9] for a general source on PAPR control.. A coding method for PAPR control in multicarrier communications is to use Golay complementary sequences [4] [5] for subcarriers such that the sequences provide low peak-to-mean envelope power ratio and Jedwab [2] , where they showed the sequences can be constructed as a coset of the first order ReedMuller codes by using algebraic normal forms. The research on Golay sequences has been flourished in the literature [3] , [12] . The reader is referred to Jedwab [6] for a comprehensive survey of Golay sequences.. The approaches above consider phase-shift keying (PSK) signal constellations. However, there are many OFDM systems utilizing quadrature amplitude modulation (QAM) constellations. Some constructions of 16-QAM and 64-QAM complementary sequences were presented sequentially by Chong et.. al [1] , Lee and Golomb [7] , and Li [8] . In 2001, Rößing and Tarokh [14] gave an upper bound of PMEPR of the set of 16-QAM sequences using 2 quaternary phase-shift keying (QPSK) Golay sequences. In 2003, Tarokh and Sadjadpour [18] generalized the results in [14] from 16-QAM to 2 2n -QAM sequences by using n QPSK Golay sequences, and determined an upper bound of the PMEPR of this set. Motivated by these works, we found that the former construction can be generalized in a new way, such that the family size is significantly enlarged while the upper bound of PMEPR changes insignificantly.. The rest of the paper is organized as follows. In Section 2, the mathematical model of the multicarrier communication, the basic concept of Golay sequences, and the main results in [14] and [18] are reviewed.. In Section 3, we give a construction of 2 2n -QAM sequences set A, and determine an upper bound of PMEPR(A). The construction in [14] and [18] can be viewed as a special case of our construction.. Section 4 is for discussions and conclusions of this construction. Note that Fact 1 in Section 2.3, the main result in [18] and in [14] , can be viewed as a special case of Theorem 1 by setting x = 2 and y = 1.. In the following, we discuss the case y > 1.. First, we consider the QPSK sequences subset S with PEP(s) δ for all s ∈ S. Obviously, there is a trade off between the size #(S) and the upper bound δ of the set S. Since δ = xy 2i which may be larger than 2, one can construct S i as a larger set than the Golay sequences set. There has been some research on how to enlarge the family size at the cost of increasing the PEP bound. The reader is referred to [13] and [15] for the construction of near-complementary sequences with PMEPR < δ, and [16] , [10] , and [17] for the construction of S with family size 2 cn and PEP upper bound c log n.. Since xy 2i is an exponential function with respect to i, there exists i 0 such that xy 2i N when i i 0 . This implies that the sequences in the set S i can be arbitrary.. If x = 2 and y = 1 + ǫ with a small number ǫ, compared with the set C presented in Fact 1, PMEPR(A) changes insignificantly by Corollary 2, while the size of the set A is significantly enlarged from the above results.. From Corollary 2, PMEPR(A) is bounded by 3 · PEP(S 1 ) if ǫ is small enough. An interesting idea is that if there exist x and y with xy 2 < 2 and S 0 is not an empty set, then one can obtain the bound PMEPR(A) < 6. Here the size #(S 0 ) and #(S 1 ) may be small, but #(S i ) would be very large for large enough i due to the comments above, which ensures that A is a set with great size.

O O O O O O O O O O O O O O O O O B O O O O O O O O O B I I I I O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O B O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


SPEECH ENHANCEMENT FOR ROBUST SPEECH RECOGNITION IN MOTORCYCLE ENVIRONMENT In the present work, we investigate the performance of a number of traditional and recent speech enhancement algorithms in the adverse non-stationary conditions, which are distinctive for motorcycles on the move. The performance of these algorithms is ranked in terms of the improvement they contribute to the speech recognition accuracy, when compared to the baseline performance, i.e. without speech enhancement. The experiments on the MoveOn motorcycle speech and noise database indicated that there is no equivalence between the ranking of algorithms based on the human perception of speech quality and the speech recognition performance. The Multi-band spectral subtraction method was observed to lead to the highest speech recognition performance. Technological advances in the Internet protocol (IP)-telephony domain have leaded to an increased interest to provide accessibility to the large domain of web application over the phone, with personal assistant-based dialogue systems offering higher comfort to the endusers 1, 2 . Higher demands with respect to efficiency, comfort and safety are imposed to those services that have transited from the controlled office/home environment to the mobile outdoors environment. On the route, driver distraction can become a significant problem, thus highly efficient human-machine interfaces and interaction are required to enable car or motorcycle drivers to interact with mobile systems and services in an easy, risk-free way.. Spoken language dialogue systems considerably improve driver's safety and userfriendliness of human-machine interfaces, due to their similarity to the conversational activity with another human, a parallel activity to which the driver is used to and it allows him to concentrate on his main activity, the driving itself. Driving quality, stress and strain situations and user acceptance when using speech and manual commands to acquire certain information on the route has previously been studied 3 , and the results have shown that, with speech input, the feeling of being distracted from driving is smaller, and road safety is improved, especially in the case of complex tasks. Although natural human-to-human interaction can be considered multimodal, as speech is usually. . The advantages of multi-channel speech enhancement can be successfully applied to the car environment, while in the motorcycle environment, due to processing power limitations, research is focused to one-channel speech enhancement. After more than three decades of advances on the one-channel speech enhancement problem, four distinct families of algorithms seem to have predominated in the literature: (i) the spectral subtractive algorithms 7 , (ii) the statistical model-based approaches 8, 9, 10 , (iii) the signal subspace approaches 11, 12 , and (iv) the enhancement approaches based on a special type of filtering 13 . As previously mentioned, the accuracy of the recognition task is also highly improved by using suitably trained speech models for the recognizer engine, including sufficient noise scenarios from the application domain. Dedicated speech corpora have previously been designed, recorded and annotated, starting with the car environment, and emerging with the motorcycle one. A European initiative, co-funding the design and implementation of speech databases in support of the development of multilingual speech recognition applications in the car environment, started in 1998 with the SPEECHDAT-CAR project 14 . The databases developed within this project were designed to include phonetically balanced speech for the needs of training generic speech recognition systems, but also domain-specific data, needed for adapting the acoustic models of speaker-independent automatic speech recognition systems to the automotive environment. Databases for ten European languages were collected within the SPEECHDAT-CAR project, with recordings from at least 300 speakers for each language, and seven characteristic environments (low speed, high speed, with audio equipment on, etc).. The CU-Move corpus consists of five domains, including digit strings, route navigation expressions, street and location sentences, phonetically balanced sentences and a route navigation dialog in a human Wizard-of-Oz like scenario, considering 500 speakers from United States of America and a natural conversational interaction 15 .. For the motorcycle environment, the SmartWeb motorbike corpus has been designed for a dialogue system dealing with open domains 16 . Recently, a domain specific (police domain) database, dealing with the extreme conditions of the motorcycle environment, has been developed in the MoveOn project 17 . In this database, the focus is the specificity of the domain, where the cognitive load of motorcyclists is quite high and the accuracy of recognition of spoken commands in the context of a template driven dialog, in the motorcycle environment, is of high priority.. In the present study, we investigate the applicability of various speech enhancement algorithms for the specifics of the motorcycle-on-the-move environment. These algorithms are ranked in terms of the improvement they bring to the speech recognition performance, when compared to the case when no speech enhancement is employed. The speech enhancement component that is in the focus of the present study is a crucial part of front-end of a spoken dialogue interaction system, which provides hands-free information support to the motorcyclists. This speech-based interface is part of a multimodal and multi-sensor interface developed in the context of the MoveOn project. Following, a brief overview of the MoveOn system, the speech enhancement methods evaluated, and the experimental setup and results are presented. Aiming at successful human-machine interaction in the motorcycle environment, we evaluated the recognition performance of a purposely-built speech front-end. Various speech enhancement techniques were assessed in an attempt to find the most appropriate pre-processing of the speech signal in the fast-varying noisy conditions. The experimental results demonstrated severe degradation of the speech recognition performance in the conditions of the motorcycle environment, compared to the clean-speech recordings conducted with the same hardware setup. The multi-band spectral subtraction method demonstrated the best performance among the eight evaluated techniques, when measured in terms of improvement of the speech recognition rate using a general-purpose acoustic model. In the case of using adapted acoustic models, the best performance was achieved by the speech enhancement method based on perceptually motivated Bayesian estimators (STSA-WCOSH) of the speech magnitude spectrum. Finally, the use of acoustic models that are adapted to the environmental conditions of the motorcycle on the move as well as the selection of an appropriate speech enhancement technique, proved to be essential for the successful interaction between the user and the dialogue system. The speech interaction interface described in Section 2 was tested with each of the speech enhancement techniques outlined in Section 3. Different environmental conditions and configuration settings of the speech recognition engine were considered for the evaluation experiments. In the following, we describe the speech data, the speech recognition engine and the experimental protocol utilized in the present evaluation.

B I O B I I O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


A Robust Speech Communication into Smart Info-Media System This paper introduces our developed noise robust speech communication techniques and describes its implementation to a smart info-media system, i.e., a small robot. Our designed speech communication system consists of automatic speech detection, recognition, and rejection. By using automatic speech detection and recognition, an observed speech waveform can be recognized without a manual trigger. In addition, using speech rejection, this system only accepts registered speech phrases and rejects any other words. In other words, although an arbitrary input speech waveform can be fed into this system and recognized, the system responds only to the registered speech phrases. The developed noise robust speech processing can reduce various noises in many environments. In addition to the design of noise robust speech recognition, the LSI design of this system has been introduced. By using the design of speech recognition application specific IC (ASIC), we can simultaneously realize low power consumption and real-time processing. This paper describes the LSI architecture of this system and its performances in some field experiments. In terms of current speech recognition accuracy, the system can realize 85-99% under 0-20 dB SNR and echo environments. Smart systems have been recognized as sophisticated, intelligent, and advanced systems. One of them, a smart humaninterface system, is embedded with a high accuracy speech recognition module. Such a smart info-media system can support the next generation products in the near future.. Speech recognition modules have been embedded into smart home electronics, smart mobiles, smart cars, and smart multi-media entertainment systems. By using speech recognition, a sophisticated human interface can be realized in any system and has compensated for a certain number of digital divide problems. The development of speech analysis and recognition has a long history, and thus some high performance speech recognition technologies have already been implemented [1] - [7] .. One current speech recognition system consists of a flame-based phonemes speech recognition and language model [2] - [7] . As another speech recognition approach, a phrase based speech recognition has been also explored [8] - [19] . Compared with the system with the flame-based phonemes speech recognition and language model, the phrase based speech recognition can provide higher recognition accuracy in various noise environments. On the other hand, it requires high calculation cost and many training databases for all target speech phrases. By using an efficient LSI design for a speech recognition system, the authors have been able to realize real-time speech recognition with low power consumption even although the total calculation cost becomes high [8] , [11] , [13] , [17] . As advanced technology using the above phrase based speech recognition techniques, a speech communication system has been proposed, and this paper presents an overview of this system and its performance. The speech communication system consists of voice activity detection (VAD) under noisy conditions, noise robust speech recognition, and noise robust speech rejection mechanism. The embedded speech communication module recognizes all target speech phrases with high recognition accuracy where non target speeches are automatically rejected. The smart robot system can answer only for the target speech phrases. In terms of recognition accuracy, the system can realize 85-99% under 0-20 dB SNR and echo environments.. In addition to these methods, this paper presents also the architecture of this speech communication system. The LSI hardware has been implemented into a small robot system as a smart info-media robot system. This system adds the whole speech communication system above, a speech synthesizer, and some controllers to intelligent home electronics. This paper introduced a speech communication system. It can provide high-accuracy speech recognition under noisy and echo conditions. The robust techniques are implemented into automatic speech detection, recognition, and rejection. In terms of current speech recognition accuracy, the system can realize 83-99% under 0-20 dB SNR and 150 msec echo environments.. The smart system has many meanings, and the advanced speech communication is regarded as a smart human interface system. The speech communication technology in this paper approaches human speech recognition ability from the viewpoint of the sound processing level. However, this technology needs to be integrated with intelligence processing and language processing levels. This will help to advance smart info-media systems.

O O O O O B I I O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O B I I O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


StarLogo under the Hood and in the Classroom StarLogo is a computer modeling tool that empowers students to understand the world through the design and creation of complex systems models. StarLogo enables students to program software creatures to interact with one another and their environment, and study the emergent patterns from these interactions. Building an easy-to-understand, yet powerful tool for students required a great deal of thought about the design of the programming language, environment, and its implementation. The salient features are StarLogo's great degree of transparency (the capability to see how a simulation is built), its support to let students create their own models (not just use models built by others), its efficient implementation (supporting simulations with thousands of independently executing creatures on desktop computers), and its flexible and simple user interface (which enables students to interact dynamically with their simulation during model testing and validation). The resulting platform provides a uniquely accessible tool that enables students to become full-fledged practitioners of modeling. In addition, we describe the powerful insights and deep scientific understanding that students have developed through the use of StarLogo.In the past 20 years a paradigm shift has been taking place in scientific research. A new approach to scientific inquiry has emerged that seeks to understand the intricacies of complex adaptive systems (CAS) by transcending separate disciplines and augmenting traditional experimental methods with the use of sophisticated tools for computer modeling. A growing group of scientists is adopting this approach to understand a range of such systems as varied as the human immune system and the global economy.Scientists now have more powerful theories and tools for explaining and predicting the behavior of self-organizing, emergent systems, ranging from natural selection and adaptation in local ecologies (e.g., Salthe, 1993) to economic supply chains (e.g., Roy, 1998). These and many other subjects studied by complexity scientists are introduced to students in middle and high schools. Teachers do not typically teach these subjects as StarLogo provides many unique benefits to students when used in the classroom. It can change the way that kids view both science and technology as well as the relationship between the two. By empowering kids to "take over the technology," StarLogo allows students to become creators, not just consumers of technology. It also helps students develop deep understanding of scientific concepts as they design, build and explore models of systems in which they are personally invested. Further, StarLogo provides an opportunity to engage students in what we deem "the real scientific method," the messy process of iteratively designing experiments, learning about systems, and subsequently modifying experiments.. While StarLogo has met with much success in many classrooms, there are still a lot of students left to reach. But we, too, are engaged in an iterative process of model building, where the StarLogo world is our model. As we learn from our own experiments in the classroom use of StarLogo, we modify the tool to better meet the needs of our audience. This means providing greater accessibility and applicability through the development of new tools and techniques. This spring, we once again enter the design phase for "StarLogo: The Next Generation," and will begin constructing the software and developing new workshops later on this year. In the past 20 years a paradigm shift has been taking place in scientific research. A new approach to scientific inquiry has emerged that seeks to understand the intricacies of complex adaptive systems (CAS) by transcending separate disciplines and augmenting traditional experimental methods with the use of sophisticated tools for computer modeling. A growing group of scientists is adopting this approach to understand a range of such systems as varied as the human immune system and the global economy.. Scientists now have more powerful theories and tools for explaining and predicting the behavior of self-organizing, emergent systems, ranging from natural selection and adaptation in local ecologies (e.g., Salthe, 1993) to economic supply chains (e.g., Roy, 1998) . These and many other subjects studied by complexity scientists are introduced to students in middle and high schools. Teachers do not typically teach these subjects as complex systems, but rather as systems that behave more mechanistically. Consequently, students frequently have difficulty understanding the complex dynamics of such systems.. For example, most teachers present the topic of ideal gases in physics class as a set of equations to be memorized. Instead, a teacher could present ideal gases as a particular example of a complex system and study it from the point of view of the interactions between gas molecules. Additionally, students tend to hold persistent misconceptions of how complex, adaptive systems work and develop incomplete models of these systems (Wilensky & Resnick, 1999) . Moreover, students rarely have the opportunity to understand how to link multiple models together to construct and test alternative representations of situations, something scientists typically do when using models (Frederiksen & White, 2000) .. Using simulations in the classroom can have many advantages. Not only do they allow students to explore systems as coherent bodies of knowledge instead of a disjoint collection of facts, but simulations allow them to explore systems at temporal and spatial scales that are not normally accessible to them in the classroom. Students can examine topics from molecular interactions to the evolution of new species which are difficult or impossible to explore experimentally without the aid of computers. Computer simulations in the classroom can be a pervasive glue that brings together experimental experiences to allow students to construct their own understandings of systems.. In this paper, we describe an approach to modeling, implemented using the StarLogo development environment, that makes it possible for students to study, hypothesize, construct, test, and evaluate their own models of complex systems. First, we show how StarLogo's approach to modeling is different than more traditional modeling environments. Then, we propose criteria that we believe to be important in designing such a modeling environment for students. Next, we introduce the StarLogo platform by way of an example model, and describe StarLogo's major actors: the turtles, the patches, and the observer. Viewed from a purely technological perspective, StarLogo has evolved over the past ten years from its origins running on a massively parallel supercomputer to one that runs on desktop computers of the kind found commonly in schools today. We describe, in a slightly more technical fashion, how StarLogo is structured internally as

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A first-order epistemic quantum computational semantics with relativistic-like epistemic effects Abstract. Quantum computation has suggested new forms of quantum logic, called quantum computational logics. In these logics wellformed formulas are supposed to denote pieces of quantum information: possible pure states of quantum systems that can store the information in question. At the same time, the logical connectives are interpreted as quantum logical gates: unitary operators that process quantum information in a reversible way, giving rise to quantum circuits. Quantum computational logics have been mainly studied as sentential logics (whose alphabet consists of atomic sentences and of logical connectives). In this article we propose a semantic characterization for a first-order epistemic quantum computational logic, whose language can express sentences like "Alice knows that everybody knows that she is pretty". One can prove that (unlike the case of logical connectives) both quantifiers and epistemic operators cannot be generally represented as (reversible) quantum logical gates. The "act of knowing" and the use of universal (or existential) assertions seem to involve some irreversible "theoretic jumps", which are similar to quantum measurements. Since all epistemic agents are characterized by specific epistemic domains (which contain all pieces of information accessible to them), the unrealistic phenomenon of logical omniscience is here avoided: knowing a given sentence does not imply knowing all its logical consequences. The theory of quantum computation has inspired the development of new forms of quantum logics that have been termed quantum computational logics. As is well known, the basic idea of the theory of quantum computers is using as a "positive resource" two characteristic concepts of quantum theory that had been for a long time described as "mysterious" and potentially paradoxical: superposition and entanglement. In quantum computation any piece of information is identified with a possible state of a quantum system (say, a photon-system) that can store and transmit the information in question. In the happiest situations a state corresponds to a maximal piece of information (about the system) that cannot be consistently extended to a richer knowledge. Such states are called pure. Due to the characteristic indeterminism of quantum theory, a pure state is at the same time a maximal and a logically incomplete piece of information that cannot decide some important properties of the corresponding physical system. Accordingly, from an intuitive point of view, one can say that any pure state describes a kind of cloud of potential properties that might become actual when a measurement is performed, giving rise to the so called collapse of the wave-function. The concept of superposition represents a mathematical realization of this intuitive idea. Any possible pure state of a quantum system S is identified with a unit-vector of an appropriate Hilbert space H S and can be represented as a superposition of other unit-vectors that belong to a basis of the space. By adopting a notation introduced by Dirac, it is customary to write:. where c i are complex numbers such that i |c i | 2 = 1. The physical interpretation is the following: the system S that is in state |ψ⟩ might satisfy the physical properties that are certain for the state |ϕ i ⟩ with probability-value |c i | 2 . Apparently, any pure state |ψ⟩ describes a parallel system of different pieces of quantum information (|ϕ i ⟩). Just this parallelism is responsible for the extraordinary efficiency and speed of quantum computers.. Another powerful resource of quantum computation is due to the use of some "strange" pure states, called entangled , that turn out to violate the classical principle of compositionality. A paradigmatic case of entanglement may concern a composite physical system S consisting of two subsystems S 1 and S 2 (say, a two-electron system). The observer has a maximal information about S, represented by a pure state |ψ⟩. What can be said about the states of the two subsystems? Due to the form of |ψ⟩ and to the quantum-theoretic rules that concern the mathematical description of composite physical systems, such states cannot be pure: they are represented by two identical mixed states, which codify a "maximal degree" of uncertainty. Consequently, the information about the global systems (S) cannot be reconstructed as a function of the pieces of information about its parts (S 1 , S 2 ). In such cases, information seems to flow from the whole to the parts (and not the other way around). Phenomena of this kind give rise to the so called holistic features of quantum theory. Interestingly enough, entangled states are currently used in teleportation-experiments and in quantum cryptography.. As expected, quantum computation cannot be identified with a "static" representation of pieces of information. What is important is the dynamic process of information that gives rise to quantum computations (performed by quantum circuits). Such process is mathematically realized by quantum logical gates (briefly, gates): special examples of unitary operators that transform pure states into pure states in a reversible way. Since in quantum theory the time-evolution of physical systems is mathematically described by unitary operators, one can say that quantum computations can be regarded as the time-evolution of some special quantum objects.. Quantum computational logics can be described as a logical abstraction from the theory of quantum circuits. The basic idea that underlies the semantic characterization of these logics can be sketched as follows:. • well formed formulas are supposed to denote pieces of quantum information: possible states of quantum systems that can store the information in question; • the logical connectives correspond to some gates that can process quantum information.. In this way, connectives turn out to have way a dynamic character, representing possible computation-actions. At the same time, any formula can be regarded as a synthetic logical description of a quantum circuit, which may have a characteristic parallel structure. Quantum computational logics have been mainly studied as sentential logics (whose alphabet consists of atomic sentences and of logical connectives). Different choices of the system of primitive connectives and of the basic semantic definitions give rise to different logics. We will refer here to a holistic version of the quantum computational semantics, where quantum entanglement is used as a "semantic resource": generally, the meaning of a compound expression determines the contextual meanings of its subexpressions (and not the other way around, as happens in the case of most compositional semantic approaches).. The logics characterized by this holistic semantics represent weak forms of quantum logic, where important classical properties of the "Boolean connectives" are generally violated. Like in fuzzy logics, conjunctions and disjunctions are not generally idempotent (according to the slogan "repetita iuvant!") and the non-contradiction principle is not valid. Furthermore, commutativity, associativity and distributivity for conjunctions and disjunctions do not generally hold.. In this article we propose a semantic characterization for a first-order epistemic quantum computational logic, whose language can express sentences like "Alice knows that everybody knows that she is pretty". As is well known, most semantic approaches to epistemic logics that can be found in the literature have been developed in the framework of a Kripke-style semantics. We will follow here a different approach, whose aim is representing both quantifiers and epistemic operators as "genuine" quantum concepts (living in a Hilbert-space environment). In this perspective, the following question arises: to what extent is it possible to interpret the quantifiers and the epistemic operators as special examples of quantum operations? Interestingly enough, these logical operators turn out to have a similar semantic behavior, giving rise to a kind of "reversibility-breaking": one can prove that (unlike the case of logical connectives) both quantifiers and epistemic operators cannot be generally represented as quantum logical gates (which are reversible unitary operations). The "act of knowing" and the use of universal (or existential) assertions seem to involve some irreversible "theoretic jumps", which are similar to quantum measurements (where the collapse of the wave-function comes into play).. A characteristic feature of the epistemic quantum computational semantics is the use of the notion of truth-perspective: each epistemic agent (say, Alice, Bob, ...) is supposed to be associated to a truth-perspective that is mathematically determined by the choice of a particular orthonormal basis of the two-dimensional Hilbert space C 2 . Truth-perspective changes give rise to some interesting relativistic-like epistemic effects: if Alice and Bob have different truth-perspectives, Alice might see a kind of deformation in Bob's logical behavior. Epistemic agents are also characterized by specific epistemic domains that contain all pieces of information accessible to them. Due to the limits of such domains the unrealistic phenomenon of logical omniscience is here avoided: Alice might know a given sentence without knowing all its logical consequences. As happens in the case of knowledge operators, quantifiers also can be interpreted as special examples of generally irreversible quantum operations. Unlike most semantic approaches, the models of the first-order quantum computational semantics do not refer to any domain of individuals dealt with as a closed set (in a classical sense). The interpretation of a universal formula does not require here any "ideal tests" that should be performed on all elements of a collection of objects (which might be infinite or indeterminate).

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