bluuebunny/crossref_metadata_2025 huggingface dataset:
Hovering of model insects: simulation by coupling equations of motion with Navier–Stokes equations
Authors: Wu Jiang Hao , Zhang Yan Lai , Sun Mao
Published: October 2009

When an insect hovers, the centre of mass of its body oscillates around a point in the air and its body angle oscillates around a mean value, because of the periodically varying aerodynamic and inertial forces of the flapping wings. In the present paper, hover flight including body oscillations is simulated by coupling the equations of motion with the Navier–Stokes equations. The equations are solved numerically; periodical solutions representing the hover flight are obtained by the shooting method. Two model insects are considered, a dronefly and a hawkmoth; the former has relatively high wingbeat frequency (n) and small wing mass to body mass ratio,whilst the latter has relatively low wingbeat frequency and large wing mass to body mass ratio. The main results are as follows. (i) The body mainly has a horizontal oscillation; oscillation in the vertical direction is about 1/6 of that in the horizontal direction and oscillation in pitch angle is relatively small. (ii) For the hawkmoth, the peak-to-peak values of the horizontal velocity, displacement and pitch angle are 0.11U (U is the mean velocity at the radius of gyration of the wing), 0.22c=4 mm(c is the mean chord length) and 4 deg., respectively. For the dronefly, the corresponding values are 0.02U, 0.05c=0.15 mm and 0.3 deg., much smaller than those of the hawkmoth. (iii) The horizontal motion of the body decreases the relative velocity of the wings by a small amount. As a result, a larger angle of attack of the wing, and hence a larger drag to lift ratio or larger aerodynamic power, is required for hovering,compared with the case of neglecting body oscillations. For the hawkmoth, the angle of attack is about 3.5 deg. larger and the specific power about 9%larger than that in the case of neglecting the body oscillations; for the dronefly, the corresponding values are 0.7 deg. and 2%. (iv) The horizontal oscillation of the body consists of two parts; one (due to wing aerodynamic force) is proportional to 1/cn2 and the other (due to wing inertial force) is proportional to wing mass to body mass ratio. For many insects, the values of 1/cn2 and wing mass to body mass ratio are much smaller than those of the hawkmoth, and the effects of body oscillation would be rather small; thus it is reasonable to neglect the body oscillations in studying their aerodynamics.
Cloning and regulation of expression of the Na+–Cl––taurine transporter in gill cells of freshwater Japanese eels
Authors: Chow S. C. , Ching L. Y. , Wong A. M. F. , Wong Chris K. C.
Published: October 2009

Our previous studies have demonstrated the hypertonic-induced expression of osmotic stress transcription factor and the regulatory volume increase (RVI)response in gill cells isolated from freshwater eels. In this study, we aimed to clone one of the organic osmolyte transporters, the Na+–Cl––taurine transporter (TauT),and to characterize its expression in anisosmotic conditions, using both in vivo and in vitro approaches. A cDNA clone encoding TauT was isolated from gill tissues of Japanese eels, Anguilla japonica. The deduced amino acid sequence shows 88–90% identity to other reported piscine TauT sequences. Our data indicated that TauT mRNA was detectable in both freshwater and seawater fish gills. The expression level of TauT mRNA increased in gills of seawater-acclimating fish. A high abundance of TauT protein was found to be localized in seawater gill chloride cells. Using primary gill cell culture, expression of the gene was induced when the ambient osmolarity was raised from 320 to 500 mosmol l–1. Hypertonic treatment of the culture caused an increase of F-actin distribution in the cell periphery. Treatment of the cells with colchicine or cytochalasin D significantly reduced TauT transcript level following hypertonic exposure. The inhibition of myosin light chain (MLC) kinase by ML-7 had a significant additive effect on hypertonic-induced TauT expression. Collectively, the data of this study reveal, for the first time, the regulation of TauT expression in gill cells of euryhaline fish. We have demonstrated the involvement of ionic strength, the cytoskeleton and MLC kinase in the regulation of TauT expression. The results shed light on the osmosensing and hyperosmotic adaption in fish gills.
Visual stimuli induced by self-motion and object-motion modify odour-guided flight of male moths (Manduca sexta L.)
Authors: Verspui Remko , Gray John R.
Published: October 2009

Animals rely on multimodal sensory integration for proper orientation within their environment. For example, odour-guided behaviours often require appropriate integration of concurrent visual cues. To gain a further understanding of mechanisms underlying sensory integration in odour-guided behaviour, our study examined the effects of visual stimuli induced by self-motion and object-motion on odour-guided flight in male M. sexta. By placing stationary objects (pillars) on either side of a female pheromone plume, moths produced self-induced visual motion during odour-guided flight. These flights showed a reduction in both ground and flight speeds and inter-turn interval when compared with flight tracks without stationary objects. Presentation of an approaching 20 cm disc, to simulate object-motion,resulted in interrupted odour-guided flight and changes in flight direction away from the pheromone source. Modifications of odour-guided flight behaviour in the presence of stationary objects suggest that visual information, in conjunction with olfactory cues, can be used to control the rate of counter-turning. We suggest that the behavioural responses to visual stimuli induced by object-motion indicate the presence of a neural circuit that relays visual information to initiate escape responses. These behavioural responses also suggest the presence of a sensory conflict requiring a trade-off between olfactory and visually driven behaviours. The mechanisms underlying olfactory and visual integration are discussed in the context of these behavioural responses.
Fiddler crabs accurately measure two-dimensional distance over three-dimensional terrain
Authors: Walls Michael L. , Layne John E.
Published: October 2009

Foraging fiddler crabs (Uca spp.) monitor the location of, and are able to return to, their burrows by employing path integration. This requires them to accurately measure both the directions and distances of their locomotory movements. Even though most fiddler crabs inhabit relatively flat terrain, they must cope with vertical features of their environment, such as sloping beaches, mounds and shells, which may represent significant obstacles. To determine whether fiddler crabs can successfully perform path integration among such three-dimensional obstacles, we tested their ability to measure distance while we imposed a vertical detour. By inserting a large hill in the homeward path of foraging crabs we show that fiddler crabs can cope with vertical detours: they accurately travel the correct horizontal distance,despite the fact that the shape of the hill forces them to change their gait from what would be used on flat ground. Our results demonstrate a flexible path integrator capable of measuring, and either integrating or discarding,the vertical dimension.
Reproductive and diurnal rhythms regulate vocal motor plasticity in a teleost fish
Authors: Rubow Tine K. , Bass Andrew H.
Published: October 2009

Seasonal and circadian rhythms control fundamental physiological processes including neural excitability and synaptic plasticity that can lead to the periodic modulation of motor behaviors like social vocalizations. Parental male midshipman fish produce three call types during the breeding season: long duration (min to >1 h) advertisement `hums', frequency and amplitude modulated agonistic `growls' (s), and very brief (ms) agonistic `grunts'produced either singly or repetitively as `grunt trains' for up to several minutes. Fictive grunts that establish the temporal properties of natural grunts are readily evoked and recorded in vivo from vocal occipital nerve roots at any time of day or year by electrical microstimulation in either the midbrain periaqueductal gray or a hindbrain vocal pre-pacemaker nucleus. Now, as shown here, the longer duration fictive growls and hums can also be elicited, but are restricted to the nocturnal reproductive season. A significant drop in call threshold accompanies the fictive growls and hums that are distinguished by their much longer duration and lower and more regular firing frequency. Lastly, the long duration fictive calls are dependent upon increased stimulation time and intensity and hence may result from activity-dependent changes in the vocal motor circuit that are themselves modulated by seasonal and circadian rhythms.
Energetic limitations on suction feeding performance in centrarchid fishes
Authors: Carroll Andrew M. , Wainwright Peter C.
Published: October 2009

Energetic analysis of ecologically relevant behaviors can be useful because animals are energetically limited by available muscle mass. In this study we hypothesized that two major determinants of suction feeding performance, the magnitudes of buccal volumetric expansion and subambient buccal pressure,would be correlated with, and limited by, available muscle mass. At least four individuals of three centrarchid species were studied: largemouth bass(Micropterus salmoides), bluegill (Lepomis macrochirus) and green sunfish (Lepomis cyanellus). Buccal pressure was measured directly via cannulation of the buccal cavity with a catheter-tipped pressure transducer. Buccal expansion was estimated from lateral high-speed video (500 or 1000 Hz) sequences and published data on internal kinematics of largemouth bass. These estimates were calibrated from silicone casts made of the buccal cavity post-mortem. Estimated work and power were found to be significantly correlated with muscle mass over all individuals. The slopes of these relationships, estimates of mass-specific muscle work and power, were found to be 11±2 J kg–1 and 300±75 W kg–1, respectively. These estimates are consistent with observations made of in vivo and in vitro muscle use and with digital particle image velocimetry measurements of water flow in feeding centrarchids. A direct trade-off between mean pressure and change in volume was observed, when the latter was normalized to muscle mass. We conclude that available muscle mass may be a useful metric of suction feeding performance,and that the ratio of muscle mass to buccal volume may be a useful predictor of subambient buccal pressure magnitude.
Mono-versusbiarticular muscle function in relation to speed and gait changes:in vivoanalysis of the goat triceps brachii
Authors: Carroll Andrew M. , Biewener Andrew A.
Published: October 2009

The roles of muscles that span a single joint (monoarticular) versus those that span two (biarticular) or more joints have been suggested to differ. Monoarticular muscles are argued to perform work at a joint, whereas biarticular muscles are argued to transfer energy while resisting moments across adjacent joints. To test these predictions, in vivo patterns of muscle activation, strain, and strain rate were compared using electromyography and sonomicrometry in two major elbow extensors, the long and lateral heads of the triceps brachii of goats (Capra hircus), across a range of speed (1–5 m s–1) and gait. Muscle recordings were synchronized to limb kinematics using high-speed digital video imaging (250 Hz). Measurements obtained from four goats(25–45 kg) showed that the monoarticular lateral head exhibited a stretch-shortening pattern (6.8±0.6% stretch and–10.6±2.7% shortening; mean ± s.e.m. for all speeds and gaits) after being activated, which parallels the flexion–extension pattern of the elbow. By contrast, the biarticular long head shortened through most of stance (–16.4±3.4%), despite elbow flexion in the first half and shoulder extension in the last half of stance. The magnitude of elbow flexion and shoulder extension increased with increasing speed (ANCOVA, P<0.05 and P<0.001), as did the magnitude and rate of active stretch of fascicles in the lateral head (P<0.001 for both). In all individuals, shortening fascicle strain rates increased with speed in the long head (P<0.001), and, in three of the four individuals, strain magnitude increased. Few independent effects of gait were found. In contrast to its expected function, the biarticular long head appears to produce positive work throughout stance, whereas the monoarticular lateral head appears to absorb work at the elbow. The biarticular anatomy of the long head may mitigate increases in muscle strain with speed in this muscle,because strain magnitude in the second phase of stance (when the shoulder extends) decreased with speed (P<0.05).
The involvement of SLC26 anion transporters in chloride uptake in zebrafish (Danio rerio) larvae
Authors: Bayaa M. , Vulesevic B. , Esbaugh A. , Braun M. , Ekker M. E. , Grosell M. , Perry S. F.
Published: October 2009

After demonstrating phylogenetic relatedness to orthologous mammalian genes, tools were developed to investigate the roles of three members (A3, A4 and A6c) of the SLC26 anion exchange gene family in Cl–uptake and HCO3 excretion in embryos and larvae of zebrafish(Danio rerio). Whole-mount in situ hybridization revealed the presence of SLC26 mRNA in gill primordia, mesonephros and heart(slc26a3 and a4 only) at 5–9 days postfertilization(d.p.f.). SLC26A3 protein was highly expressed in lateral line neuromasts and within the gill, was localized to a sub-population of epithelial cells, which often (but not always) coexpressed Na+/K+-ATPase. SLC26 mRNA levels increased with developmental age, peaking at 5–10 d.p.f.;the largest increases in rates of Cl– uptake(\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(J_{\mathrm{in}}^{\mathrm{Cl}^{-}}\) \end{document}) preceded the mRNA spike, occurring at 2–5 d.p.f. Raising zebrafish in water with a low [Cl–] caused marked increases in \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(J_{\mathrm{in}}^{\mathrm{Cl}^{-}}\) \end{document} at 3–10 d.p.f. and was associated with increased levels of SLC26 mRNA. Raising fish in water of high [Cl–] was without effect on \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(J_{\mathrm{in}}^{\mathrm{Cl}^{-}}\) \end{document} or SLC26 transcript abundance. Selective gene knockdown using morpholino antisense oligonucleotides demonstrated a significant role for SLC26A3 in Cl– uptake in larval fish raised in control water and roles for A3, A4 and A6c in fish raised in water with low [Cl–]. Prolonged (7 days) or acute (24 h) exposure of fish to elevated (2 or 5 mmol l–1) ambient [HCO3–] caused marked increases in Cl– uptake when determined in water of normal [HCO3–] that were accompanied by elevated levels of SLC26 mRNA. The increases in \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(J_{\mathrm{in}}^{\mathrm{Cl}^{-}}\) \end{document} associated with high ambient [HCO3–] were not observed in the SLC26 morphants (significant only at 5 mmol l–1HCO3– for A4 and 2 mmol l–1HCO3– for A6c). Net base excretion was markedly inhibited in the slc26a3 and a6c morphants thereby implicating these genes in Cl–/HCO3– exchange. The results suggest that under normal conditions, Cl– uptake in zebrafish larvae is mediated by SLC26A3 Cl–/HCO3– exchangers but under conditions necessitating higher rates of high affinity Cl–uptake, SlC26A4 and SLC26A6c may assume a greater role.
The vortex wake of blackcaps (Sylvia atricapillaL.) measured using high-speed digital particle image velocimetry (DPIV)
Authors: Johansson L. C. , Hedenström A.
Published: October 2009

Reconstructing the vortex wake of freely flying birds is challenging, but in the past few years, direct measurements of the wake circulation have become available for a number of species. Streamwise circulation has been measured at different positions along the span of the birds, but no measurements have been performed in the transverse plane. Recent findings from studies of bat wakes have pointed to the importance of transverse plane data for reconstructing the wake topology because important structures may be missed otherwise. We present results of high-speed DPIV measurements in the transverse plane behind freely flying blackcaps. We found novel wake structures previously not shown in birds, including wing root vortices of opposite as well as the same sign as the wing tip vortices. This suggests a more complex wake structure in birds than previously assumed and calls for more detailed studies of the flow over the wings and body, respectively. Based on measurements on birds with and without a tail we also tested hypotheses regarding the function of the tail during steady flight. We were unable to detect any differences in the wake pattern between birds with and without a tail. We conclude that the birds do not use their tail to exploit vortices shed at the wing root during the downstroke. Neither did we find support for the hypothesis that the tail should reduce the drag of the bird. The function of the tail during steady flight thus remains unclear and calls for further investigation in future studies.
Optimum parameters design for friction stir spot welding using a genetically optimized neural network system
Authors: Atharifar H
Published: October 2009

A method based on a genetically optimized neural network system (GONNS) is introduced to enhance the selection of the optimum parameters for the friction stir spot welding (FSSW) process. For a given FSSW setup, an artificial neural network (ANN) is designed with three process parameters as inputs and three process variables as outputs. The outputs of the ANN are selected as the weld's tensile force, plunging load, and process duration. Preliminary experimental results are utilized in order to train the ANN. After verifying the accuracy of the trained ANN, an optimization method based on the genetic algorithm heuristic search method is used to optimize the evaluation functions that are normalized functions of the ANN outputs. Eventually, the minimization of the evaluation functions yields the optimum ANN inputs (FSSW parameters) that are verified by additional experiments. Results affirm that the analytically obtained optimums of the FSSW parameters are valid and that, by utilizing these parameters, higher weld strength, lower plunging load, and shorter process duration are obtained.
Artificial neural network modelling of Nd:YAG laser microdrilling on titanium nitride—alumina composite
Authors: Biswas R , Kuar A S , Biswas S K , Mitra S
Published: October 2009

Selection of machining parameter combinations for obtaining optimum circularity at entry and exit and hole taper is a challenging task in laser microdrilling owing to the presence of a large number of process variables. There is no perfect combination of parameters that can simultaneously result in higher circularity at entry and exit and lower hole taper. The current paper attempts to develop a strategy for predicting machining parameter settings for the generation of the maximum circularity at entry and exit and minimum hole taper. An artificial neural network (ANN) is used for process modelling of laser microdrilling of titanium nitride—alumina composite and a feed-forward back-propagation network is developed to model the machining process. The model, after proper training, is capable of predicting the response parameters as a function of five different control parameters. Experimental results demonstrate that the machining model is suitable and the optimization strategy satisfies practical requirements. The developed model is found to be unique, powerful, and flexible.
Rehydration and ultrasonic-assisted decolouration of dry tilapia (Oreochromis niloticus) skin
Authors: Wang L , Yang B , Deng P , Zhang J
Published: October 2009

Skin is an important by-product during the processing of tilapia, which is a productive warm-water fish. The skin produced during the process is not well utilized at present due to the pigment, even though the production is large. In the current study, the rehydration conditions of dry tilapia skin were investigated. Through response surface methodology, lactic acid concentration, time, and temperature were shown to have significant effects on the rehydration ratio of dry tilapia skin. The optimal rehydration ratio was obtained by incubating the dry tilapia skin in 63.2 per cent (w/v) lactic acid at 29.8 °C for 7.0 h. The P and R2 values indicated that the response surface model had a good fit to the practical behaviour. H2O2 oxidation was an effective decolouration technique for tilapia skin. Furthermore, ultrasonic treatment could apparently accelerate the tilapia skin decolouration by H2O2. A combination of 6 per cent (w/v) H2O2 and 10 h (or 15 per cent H2O2 and 8 h) resulted in the formation of white skin. This research will favour application of tilapia skin in the food industry.
Study on steam turbine fault diagnosis and maintenance service grid system
Authors: Ding Y F , Sheng B Y
Published: October 2009

It is important to ensure the safe operation, quick fault diagnosis, and maintenance of steam turbines. This is a challenging problem since steam turbines tend to be geographically dispersed and it is difficult to offer a timely response to a facility that can be a considerable distance from the maintenance division. The manufacturing grid is resource sharing technology that could provide a solution to this problem. A framework to apply this concept to steam turbine fault diagnosis and maintenance operations is proposed in this paper. In the proposed manufacturing grid the fault type is identified by an artificial neural network algorithm and the maintenance solution is given on the basis case-based reasoning with the framework of rough set theory. A prototype system is developed on the basis of proposed methodologies to demonstrate their feasibility.
Neural network approach for the selection of processing parameters of aluminium—iron composite preforms during cold upsetting
Authors: Poshal G , Ganesan P
Published: October 2009

The powder forging process of die forging, sintering, and upsetting is a convenient way of reducing or eliminating the porosity from traditional powder metallurgy products. Forging of metal powder enhances the demanding high-tensile, impact, and fatigue strength of powder metallurgy products. In this research, a demonstration system has been developed that employs a neural network for advising aluminium—iron composite compositions and optimum process settings with desired properties at an early stage in the design of the component. The input comprises the desired mechanical properties, such as formability index, and the system employs these data as inputs in order to recommend suitable metal powder compositions and process settings such as the particle size, percentage of iron content, preform density, aspect ratio, and compact load. The training data were collected by the experimental set-up in the laboratory for the sintered aluminium—iron composite preforms. Comparison of predicted and experimental data has confirmed the accuracy of the neural network approach; therefore, a new way for recommending suitable metal powder compositions and process settings is explored.
Combination of isotropic and kinematic hardening to predict fracture and improve press formability of a door hinge
Authors: Nguyen D-T , Kim Y-S
Published: October 2009

To predict a fracture in the concentrated stress and strain area of a door hinge, the criterion for a ductile fracture, as developed by Oyane ( Journal of Mechanical Work. Technology,
Feature Article—Merging AI and OR to Solve High-Dimensional Stochastic Optimization Problems Using Approximate Dynamic Programming
Authors: Powell Warren B.
Published: October 2009

We consider the problem of optimizing over time hundreds or thousands of discrete entities that may be characterized by relatively complex attributes, in the presence of different forms of uncertainty. Such problems arise in a range of operational settings such as transportation and logistics, where the entities may be aircraft, locomotives, containers, or people. These problems can be formulated using dynamic programming but encounter the widely cited “curse of dimensionality.” Even deterministic formulations of these problems can produce math programs with millions of rows, far beyond anything being solved today. This paper shows how we can combine concepts from artificial intelligence and operations research to produce practical solution methods that scale to industrial-strength problems. Throughout, we emphasize concepts, techniques, and notation from artificial intelligence and operations research to show how these fields can be brought together for complex stochastic, dynamic problems.
Adaptive Auction Mechanism Design and the Incorporation of Prior Knowledge
Authors: Pardoe David , Stone Peter , Saar-Tsechansky Maytal , Keskin Tayfun , Tomak Kerem
Published: October 2009

Electronic auction markets are economic information systems that facilitate transactions between buyers and sellers. Whereas auction design has traditionally been an analytic process that relies on theory-driven assumptions such as bidders' rationality, bidders often exhibit unknown and variable behaviors. In this paper we present a data-driven adaptive auction mechanism that capitalizes on key properties of electronic auction markets, such as the large transaction volume, access to information, and the ability to dynamically alter the mechanism's design to acquire information about the benefits from different designs and adapt the auction mechanism online in response to actual bidders' behaviors. Our auction mechanism does not require an explicit representation of bidder behavior to infer about design profitability—a key limitation of prior approaches when they address complex auction settings. Our adaptive mechanism can also incorporate prior general knowledge of bidder behavior to enhance the search for effective designs. The data-driven adaptation and the capacity to use prior knowledge render our mechanisms particularly useful when there is uncertainty regarding bidders' behaviors or when bidders' behaviors change over time. Extensive empirical evaluations demonstrate that the adaptive mechanism outperforms any single fixed mechanism design under a variety of settings, including when bidders' strategies evolve in response to the seller's adaptation; our mechanism's performance is also more robust than that of alternatives when prior general information about bidders' behaviors differs from the encountered behaviors.
Least-Squares Support Vector Machine Approach to Viral Replication Origin Prediction
Authors: Cruz-Cano Raul , Chew David S. H. , Choi Kwok-Pui , Leung Ming-Ying
Published: October 2009

Replication of their DNA genomes is a central step in the reproduction of many viruses. Procedures to find replication origins, which are initiation sites of the DNA replication process, are therefore of great importance for controlling the growth and spread of such viruses. Existing computational methods for viral replication origin prediction have mostly been tested within the family of herpesviruses. This paper proposes a new approach by least-squares support vector machines (LS-SVMs) and tests its performance not only on the herpes family but also on a collection of caudoviruses coming from three viral families under the order of caudovirales. The LS-SVM approach provides sensitivities and positive predictive values superior or comparable to those given by the previous methods. When suitably combined with previous methods, the LS-SVM approach further improves the prediction accuracy for the herpesvirus replication origins. Furthermore, by recursive feature elimination, the LS-SVM has also helped find the most significant features of the data sets. The results suggest that the LS-SVMs will be a highly useful addition to the set of computational tools for viral replication origin prediction and illustrate the value of optimization-based computing techniques in biomedical applications.
On the Core and f-Nucleolus of Flow Games
Authors: Kern Walter , Paulusma Daniël
Published: October 2009

Using the ellipsoid method, both Deng et al. [Deng, X., Q. Fang, X. Sun. 2006. Finding nucleolus of flow game. Proc. 17th ACM-SIAM Sympos. Discrete Algorithms. ACM Press, New York, 124–131] and Potters et al. [Potters, J., H. Reijnierse, A. Biswas. 2006. The nucleolus of balanced simple flow networks. Games Econom. Behav. 54 205–225] show that the nucleolus of simple flow games (where all edge capacities are equal to one) can be computed in polynomial time. Our main result is a combinatorial method based on eliminating redundant s–t path constraints such that only a polynomial number of constraints remains. This leads to efficient algorithms for computing the core, nucleolus, and nucleon of simple flow games. Deng et al. also prove that computing the nucleolus for (general) flow games is NP-hard. We generalize this by proving that computing the f-nucleolus of flow games is NP-hard for all priority functions f that satisfy f(A) > 0 for all coalitions A with worth v(A) > 0 (so, including the priority functions corresponding to the nucleolus, nucleon, and per-capita nucleolus).
Equivalence of Convex Problem Geometry and Computational Complexity in the Separation Oracle Model
Authors: Freund Robert M. , Vera Jorge R.
Published: October 2009

Consider the supposedly simple problem of computing a point in a convex set that is conveyed by a separation oracle with no further information (e.g., no domain ball containing or intersecting the set, etc.). The authors' interest in this problem stems from fundamental issues involving the interplay of (i) the computational complexity of computing a point in the set, (ii) the geometry of the set, and (iii) the stability or conditioning of the set under perturbation. Under suitable definitions of these terms, the authors show herein that problem instances with favorable geometry have favorable computational complexity, validating conventional wisdom. The authors also show a converse of this implication by showing that there exist problem instances that require more computational effort to solve in certain families characterized by unfavorable geometry. This in turn leads, under certain assumptions, to a form of equivalence among computational complexity, geometry, and the conditioning of the set. The authors' measures of the geometry, relative to a given reference point, are based on the radius of a certain domain ball whose intersection with the set contains a certain inscribed ball.

The geometry of the set is then measured by the radius of the domain ball, the radius of the inscribed ball, and the ratio between these two radii, the latter of which is called the aspect ratio. The aspect ratio arises in the analysis of many algorithms for convex problems, and its importance in convex algorithm analysis has been well-known for several decades. However, the presence in our bound of terms involving only the radius of the domain ball and only the radius of the inscribed ball are a bit counterintuitive; nevertheless, we show that the computational complexity must involve these terms in addition to the aspect ratio, even when the aspect ratio itself is small. This lower-bound complexity analysis relies on simple features of the separation oracle model; if we instead assume that the set is conveyed by a self-concordant barrier function, then it is an open challenge to prove such a complexity lower-bound.
A Strongly Polynomial Algorithm for Controlled Queues
Authors: Zadorojniy Alexander , Even Guy , Shwartz Adam
Published: October 2009

We consider the problem of computing optimal policies of finite-state finite-action Markov decision processes (MDPs). A reduction to a continuum of constrained MDPs (CMDPs) is presented such that the optimal policies for these CMDPs constitute a path in a graph defined over the deterministic policies. This path contains, in particular, an optimal policy of the original MDP. We present an algorithm based on this new approach that finds this path, and thus an optimal policy. In the general case, this path might be exponentially long in the number of states and actions. We prove that the length of this path is polynomial if the MDP satisfies a coupling property. Thus we obtain a strongly polynomial algorithm for MDP s that satisfies the coupling property. We prove that discrete time versions of controlled M/M/1 queues induce MDP s that satisfy the coupling property. The only previously known polynomial algorithm for controlled M/M/1 queues in the expected average cost model is based on linear programming (and is not known to be strongly polynomial). Our algorithm works both for the discounted and expected average cost models, and the running time does not depend on the discount factor.
Global Facility Network Design with Transshipment and Responsive Pricing
Authors: Dong Lingxiu , Kouvelis Panos , Su Ping
Published: October 2009

This paper considers the facility network design problem for a global firm that sells to two markets: the domestic market and a foreign market. Although the firm has to invest in capital-intensive production facilities and produce outputs in the face of demand and exchange rate uncertainties, it can postpone the transshipment, localization, and distribution of the output until after uncertainties are resolved. The key network design decisions faced by the firm are in which of the two markets to locate the capital-intensive production facilities and what the corresponding output levels should be. We provide the complete characterization of the optimal global facility network configuration for two types of global firms: a newsvendor with exogenously given selling prices and a firm with the flexibility of pricing responsively after uncertainties are resolved. Our study's focus is on the impact of exchange rate uncertainty and responsive pricing on facility network decisions. Compared with a newsvendor facing demand uncertainty only, the introduction of exchange rate uncertainty or the use of responsive pricing can increase the attractiveness of centralized production. A responsive-pricing firm's optimal network design differs from that of a newsvendor firm as follows. (1) The firm's network preference is less susceptible to the increase of localization costs. (2) The firm is less likely to switch from a network of regional production to a network of centralized production in response to the increasing size of one market. (3) Demand and exchange rate uncertainties can have opposite effects on its optimal centralized output when the nature of the random shocks they introduce to the firm's demand function is different: under the linear demand function, the optimal centralized output increases in the demand volatility when demand shock is additive, but it may decrease in the exchange rate volatility because the corresponding price shock is multiplicative. Interestingly, common to both types of firms, their network preferences, although sensitive to costs and mean demand and exchange rate, are robust to the demand and exchange rate volatilities, suggesting that transshipment-enabled output substitutability between the two markets diminishes the impact of increasing market volatilities on the network design decision.
A Comparison of Traditional and Open-Access Policies for Appointment Scheduling
Authors: Robinson Lawrence W. , Chen Rachel R.
Published: October 2009

This paper compares two types of appointment-scheduling policies for single providers: traditional and open-access. Under traditional scheduling, each of a specified number of patients per day is booked well in advance, but may not show up for his or her appointment. Under open-access scheduling, a random number of patients call in the morning to make an appointment for that same day. Thus the number of patient arrivals will be random, for different reasons, under both policies. We find that the open-access schedule will significantly outperform the traditional schedule—in terms of a weighted average of patients' waiting time, the doctor's idle time, and the doctor's overtime—except when patient waiting time is held in little regard or when the probability of no-shows is quite small.
Dynamic Scheduling of Outpatient Appointments Under Patient No-Shows and Cancellations
Authors: Liu Nan , Ziya Serhan , Kulkarni Vidyadhar G.
Published: October 2009

This paper develops a framework and proposes heuristic dynamic policies for scheduling patient appointments, taking into account the fact that patients may cancel or not show up for their appointments. In a simulation study that considers a model clinic, which is created using data obtained from an actual clinic, we find that the heuristics proposed outperform all the other benchmark policies, particularly when the patient load is high compared with the regular capacity. Supporting earlier findings in the literature, we find that the open access policy, a recently proposed popular scheduling paradigm that calls for “meeting today's demand today,” can be a reasonable choice when the patient load is relatively low.
On the Pricing of Natural Gas Pipeline Capacity
Authors: Secomandi Nicola
Published: October 2009

Pipelines play a critical role in matching the supply and demand of natural gas. The pricing of their capacity is an important problem in practice for pipeline companies and the users of this capacity, which include shippers such as natural gas merchants, producers, and local distribution companies. This paper conducts a normative analysis of how pipeline capacity should be priced by each of these players. Although the trading value of this capacity should be relevant to merchants and its substitution and congestion values to shippers and pipelines, respectively, this analysis shows that all of these are equivalent values. Thus pipeline capacity should be priced at its trading value, a prediction that can be empirically investigated. This paper also conducts an empirical analysis of this prediction based on transacted prices of transport contracts for the capacity of the Tennessee Gas Pipeline, a major interstate pipeline in the United States, and finds support for it. This analysis suggests that the uncertainty in the evolution of natural gas prices is an important driver of operational performance in the pricing of pipeline capacity. The results of this paper have potential relevance for the pricing of the capacity of other commodity conversion assets.
Thermodynamics: Nano vs. macro
Authors: Wautelet Michel , Shirinyan Aram S.
Published: October 2009

Ordinary macroscopic thermodynamics is applied when the number of atoms in the studied systems is "large". Conditions where nanosystems are "large" with respect to thermodynamics definition are first discussed. In the thermodynamical regime, size and shape effects are known to be important. It has been known for a long time that the melting temperature of nanosystems decreases when their size decreases. A generalization of this leads to the conclusion that phase diagrams are also size- and shape-dependent. In nanosystems, the number of atoms is limited. This differs from classical thermodynamics, where the number of atoms is assumed to be unlimited. The consequences of this difference for the definition of phase diagrams are discussed. In particular, the liquidus and solidus lines have to be carefully defined. The structure of the two-phase nanoparticles also plays a role in the calculation of the phase diagrams.
Quasi-isothermal temperature-modulated differential scanning calorimetry (TMDSC) for the separation of reversible and irreversible thermodynamic changes in glass transition and melting ranges of flexible macromolecules
Authors: Wunderlich Bernhard
Published: October 2009

With standard differential scanning calorimetry (DSC), it is possible to derive calorimetric data for equilibrium or metastable samples. The introduction of temperature-modulated DSC (TMDSC) permits in its quasi-isothermal (non-scanning) mode (TMDC), long-time apparent heat capacity measurements of high precision (±1 %). For flexible molecules, heat capacity measurements from the various calorimetric methods could be combined in the ATHAS Data Bank, which now contains experimental data for over 200 materials. These data were linked to the vibrational and large-amplitude motion of the constituent atoms and molecules, to provide a base for the judgement of the thermal analyses, extending outside the range of equilibrium or metastability with an error of only 2-5 %. The TMDC together with DSC is now able to quantitatively assess the reversibility of thermal processes. A sufficient number of systems have been analyzed in this fashion to develop better understanding of macro-, micro-, and nanophases of flexible macromolecules. The new concepts discussed are: (1) multiple glass transitions due to possible rigid-amorphous fractions (RAFs) and glass transitions within crystals, both observed in semicrystalline macromolecules, and (2) locally reversibly melting on the surface of chain-folded crystals. The locally reversible melting decreases with crystal perfection and also disappears when the chains become rigid.
Trace gas adsorption thermodynamics at the air−water interface: Implications in atmospheric chemistry
Authors: Valsaraj Kalliat T.
Published: October 2009

The thermodynamics of adsorption of gaseous organic compounds such as polycyclic aromatic hydrocarbons (PAHs) on water films is reviewed and discussed. The various experimental methods available to determine the thermodynamic equilibrium constant and the structure–activity relationships to correlate and estimate the same are reviewed. The atmospheric implications of the adsorption and oxidation of PAHs at the air–water interface of thin films of water such as existing in fog droplets, ice films, and aerosols are also enumerated.
Thermodynamic study on phase transitions of poly(benzyl methacrylate) in ionic liquid solvents
Authors: Ueki Takeshi , Arai Asako Ayusawa , Kodama Koichi , Kaino Sayaka , Takada Noriko , Morita Takeshi , Nishikawa Keiko , Watanabe Masayoshi
Published: October 2009

The lower critical solution temperature (LCST) phase behavior of poly(benzyl methacrylate) (PBnMA) in room-temperature ionic liquids (ILs) was studied by considering the effect of the chemical structure of ILs on the phase separation temperature (T
c). It was found that the LCST behavior of PBnMA was observed in ILs containing [NTf2] anions and PF6 anions. T
c changed significantly with a small change in the chemical structures of the cations. High-sensitivity differential scanning calorimetry (DSC) was successfully performed for studying the LCST phase separation of PBnMA in two different imidazolium-based ILs. Endothermic peaks corresponding to the phase separation of PBnMA from the ILs were clearly observed at ca. 100 °C in the DSC thermograms. It was experimentally verified for the first time that the negative enthalpy and entropy change of mixing of PBnMA in ILs caused the LCST phase separations. The absolute values of the thermodynamic parameters for the phase transition of PBnMA in ILs obtained in this study were much lower than those reported in previous studies for aqueous polymer solutions that exhibit LCST phase behavior, such as poly(N-isopropylarylamide) and poly(vinyl methyl ether). Small changes in the thermodynamic parameters resulted in a large change in the phase separation temperature even by small changes in the chemical structure of the ILs and polymers. The microscopic desolvation process detected from the DSC measurements was inferred to have occurred before the macroscopic phase separation detected from turbidity measurements. The dependence of the endothermic peak temperatures on the DSC scan rate was observed even at slow scan rates. These results indicate that the phase separation of PBnMA from ILs is characterized by extremely slow kinetics.
Biological calorimetry and the thermodynamics of the origination and evolution of life
Authors: Hansen Lee D. , Criddle Richard S. , Battley Edwin H.
Published: October 2009

Calorimetric measurements on biological systems from small molecules to whole organisms lead to a new conception of the nature of live matter that has profound consequences for our understanding of biology. The data show that the differences in Gibbs energy (ΔG) and enthalpy (ΔH) are near zero or negative and the difference in entropy (ΔS) is near zero between a random mixture of molecules and live matter of the same composition. A constant input of energy is required to maintain ion gradients, ATP production, and the other functions of living matter, but because cells are organized in a spontaneous process, no energy input is required to maintain the structure or organization of cells. Thus, the origin of life and evolution of complex life forms occurs by thermodynamically spontaneous processes, carbon-based life should be common throughout the universe, and because there is no energy cost, evolution can occur relatively rapidly.
Study of heat capacity enhancement in some nanostructured materials
Authors: Tan Zhi-Cheng , Wang Lan , Shi Quan
Published: October 2009

Heat capacity properties of some nanostructured oxides, metals, and zeolites were studied, mainly with the aid of low-temperature adiabatic calorimetry. Obvious enhancement in the heat capacity of nanostructured materials to different degrees was observed as compared with the corresponding coarse-grained materials. The contributions of enhanced heat capacity of nanostructured materials toward properties such as density, thermal expansion, sample purity, surface effect, and size effect are discussed.
Thermochemistry of organic molecules: The way to understand energy–structure relationships
Authors: Roux María Victoria , Foces-Foces Concepción , Notario Rafael
Published: October 2009

The combination of experimental calorimetric measurements, particularly of the standard energies and enthalpies of combustion and formation, and theoretical examination of model molecules constitutes a powerful tool for the understanding of the conformational and chemical behavior of organic molecules. In this article, several examples are provided where the synergy between experiment and theory made possible the comprehension of various fundamental interactions in oxygen- and sulfur-containing six-membered heterocyclic compounds, the determination of the strain energy in two C8H8derivatives, dimethyl cubane-1,4-dicarboxylate and dimethyl cuneane-2,6-dicarboxylate, and the calculation of the enthalpies of formation of the parent compounds, cubane and cuneane, and the study of the energy–structure relationship in barbituric acid.