bluuebunny/crossref_metadata_2025 huggingface dataset:
Next-generation sequencing reveals cryptic mtDNA diversity of Plasmodium relictum in the Hawaiian Islands
Authors: JARVI S. I. , FARIAS M. E. , LAPOINTE D. A. , BELCAID M. , ATKINSON C. T.
Published: August 2013

Next-generation 454 sequencing techniques were used to re-examine diversity of mitochondrial cytochrome b lineages of avian malaria (Plasmodium relictum) in Hawaii. We document a minimum of 23 variant lineages of the parasite based on single nucleotide transitional changes, in addition to the previously reported single lineage (GRW4). A new, publicly available portal (Integroomer) was developed for initial parsing of 454 datasets. Mean variant prevalence and frequency was higher in low elevation Hawaii Amakihi (Hemignathus virens) with Avipoxvirus-like lesions (P = 0·001), suggesting that the variants may be biologically distinct. By contrast, variant prevalence and frequency did not differ significantly among mid-elevation Apapane (Himatione sanguinea) with or without lesions (P = 0·691). The low frequency and the lack of detection of variants independent of GRW4 suggest that multiple independent introductions of P. relictum to Hawaii are unlikely. Multiple variants may have been introduced in heteroplasmy with GRW4 or exist within the tandem repeat structure of the mitochondrial genome. The discovery of multiple mitochondrial lineages of P. relictum in Hawaii provides a measure of genetic diversity within a geographically isolated population of this parasite and suggests the origins and evolution of parasite diversity may be more complicated than previously recognized.
Echinococcus species from red foxes, corsac foxes, and wolves in Mongolia
Authors: ITO AKIRA , CHULUUNBAATAR GANTIGMAA , YANAGIDA TETSUYA , DAVAASUREN ANU , SUMIYA BATTULGA , ASAKAWA MITSUHIKO , KI TOSHIAKI , NAKAYA KAZUHIRO , DAVAAJAV ABMED , DORJSUREN TEMUULEN , NAKAO MINORU , SAKO YASUHITO
Published: August 2013

The small intestines of 420 wild canids (111 corsac foxes, 191 red foxes and 118 wolves) from Mongolia, were examined for adult worms of the genus Echinococcus. The Mongolian genotype of Echinococcus multilocularis was found in fifteen red foxes and four wolves, whereas two genotypes (G6/7 and G10) of Echinococcus canadensis were found in two and three wolves, respectively. No adult Echinococcus worms were found in the corsac foxes examined. The genotypes of E. multilocularis and E. canadensis are discussed in terms of host specificity and distribution in Mongolia. The importance of wolves in the completion of the life cycle of Echinococcus spp. is also discussed.
Plasmodium falciparumgametocytes: with a view to a kill
Authors: BUTTERWORTH ALICE S. , SKINNER-ADAMS TINA S. , GARDINER DON L. , TRENHOLME KATHARINE R.
Published: August 2013

Drugs that kill or inhibit the sexual stages ofPlasmodiumin order to prevent transmission are important components of malaria control programmes. Reducing gametocyte carriage is central to the control ofPlasmodium falciparumtransmission as infection can result in extended periods of gametocytaemia. Unfortunately the number of drugs with activity against gametocytes is limited. Primaquine is currently the only licensed drug with activity against the sexual stages of malaria parasites and its use is hampered by safety concerns. This shortcoming is likely the result of the technical challenges associated with gametocyte studies together with the focus of previous drug discovery campaigns on asexual parasite stages. However recent emphasis on malaria eradication has resulted in an upsurge of interest in identifying compounds with activity against gametocytes. This review examines the gametocytocidal properties of currently available drugs as well as those in the development pipeline and examines the prospects for discovery of new anti-gametocyte compounds.
Extraction of social information from gait in schizophrenia
Authors: Peterman J. S. , Christensen A. , Giese M. A. , Park S.
Published: August 2013

Background

The human face and body are rich sources of socio-emotional cues. Accurate recognition of these cues is central to adaptive social functioning. Past studies indicate that individuals with schizophrenia (SZ) show deficits in the perception of emotion from facial cues but the contribution of bodily cues to social perception in schizophrenia is undetermined. The present study examined the detection of social cues from human gait patterns presented by computer-generated volumetric walking figures.

Method

A total of 22 SZ and 20 age-matched healthy control participants (CO) viewed 1 s movies of a ‘digital’ walker's gait and subsequently made a forced-choice decision on the emotional state (angry or happy) or the gender of the walker presented at three intensity levels. Overall sensitivity to the social cues and bias were computed. For SZ, symptom severity was assessed.

Results

SZ were less sensitive than CO on both emotion and gender discrimination, regardless of intensity. While impaired overall, greater signal intensity did improve performance of SZ. Neither group differed in their response bias in either condition. The discrimination sensitivity of SZ was unrelated to their social functioning or symptoms but a bias toward perceiving gait as happy was associated with better social functioning.

Conclusions

These results suggest that SZ are impaired in extracting social information from gait but SZ benefited from increased signal intensity of social cues. Inaccurate perception of social cues in others may hinder adequate preparation for social interactions.
An experience sampling study of worry and rumination in psychosis
Authors: Hartley S. , Haddock G. , Vasconcelos e Sa D. , Emsley R. , Barrowclough C.
Published: August 2013

Background

Increasing research effort is being dedicated to investigating the links between emotional processes and psychosis, despite the traditional demarcation between the two. Particular focus has alighted upon two specific anxious and depressive processes, worry and rumination, given the potential for links with aspects of delusions and auditory hallucinations. This study rigorously explored the nature of these links in the context of the daily life of people currently experiencing psychosis.

Method

Experience sampling methodology (ESM) was used to assess the momentary links between worry and rumination on the one hand, and persecutory delusional ideation and auditory hallucinations on the other. Twenty-seven participants completed the 6-day experience sampling period, which required repeated self-reports on thought processes and experiences. Multilevel modelling was used to examine the links within the clustered data.

Results

We found that antecedent worry and rumination predicted delusional and hallucinatory experience, and the distress they elicited. Using interaction terms, we have shown that the links with momentary symptom severity were moderated by participants' trait beliefs about worry/rumination, such that they were reduced when negative beliefs about worry/rumination (meta-cognitions) were high.

Conclusions

The current findings offer an ecologically valid insight into the influence of worry and rumination on the experience of psychotic symptoms, and highlight possible avenues for future intervention strategies.
On the classification of mapping class actions on Thurston's asymmetric metric
Authors: LIU L. , PAPADOPOULOS A. , SU W. , THÉRET G.
Published: August 2013

We study the action of the elements of the mapping class group of a surface of finite type on the Teichmüller space of that surface equipped with Thurston's asymmetric metric. We classify such actions as elliptic, parabolic, hyperbolic and pseudo-hyperbolic, depending on whether the translation distance of such an element is zero or positive and whether the value of this translation distance is attained or not, and we relate these four types to Thurston's classification of mapping class elements. The study is parallel to the one made by Bers in the setting of Teichmüller space equipped with Teichmüller's metric, and to the one made by Daskalopoulos and Wentworth in the setting of Teichmüller space equipped with the Weil–Petersson metric.
The Rise of a Chinese House Church: The Organizational Weapon
Authors: Koesel Karrie J.
Published: August 2013

This article investigates the similarities between the organizational innovation of one underground Protestant house church in China and the rise of early communist parties. Much like the spread of communism, the organizational tactics of the church are designed to protect it in a hostile political environment. The different levels are insulated from each other, with limited knowledge of the members above and below. In this way, if anyone is raided by the authorities, the others can continue to function with little interruption. Thus, the highly touted “organizational weapon” developed by the Bolsheviks and recycled, for example, by the Chinese Communist Party in their struggle for power, has resurfaced many years later. However, this time it has been adopted by a religious “vanguard.”
Phylogenetic analysis and victim contact tracing of rabies virus from humans and dogs in Bali, Indonesia
Authors: MAHARDIKA G. N. K. , DIBIA N. , BUDAYANTI N. S. , SUSILAWATHI N. M. , SUBRATA K. , DARWINATA A. E. , WIGNALL F. S. , RICHT J. A. , VALDIVIA-GRANDA W. A. , SUDEWI A. A. R.
Published: August 2013

The emergence of human and animal rabies in Bali since November 2008 has attracted local, national and international interest. The potential origin and time of introduction of rabies virus to Bali is described. The nucleoprotein (N) gene of rabies virus from dog brain and human clinical specimens was sequenced using an automated DNA sequencer. Phylogenetic inference with Bayesian Markov Chain Monte Carlo (MCMC) analysis using the Bayesian Evolutionary Analysis by Sampling Trees (BEAST) v. 1.7.5 software confirmed that the outbreak of rabies in Bali was caused by an Indonesian lineage virus following a single introduction. The ancestor of Bali viruses was the descendant of a virus from Kalimantan. Contact tracing showed that the event most likely occurred in early 2008. The introduction of rabies into a large unvaccinated dog population in Bali clearly demonstrates the risk of disease transmission for government agencies and should lead to an increased preparedness and efforts for sustained risk reduction to prevent such events from occurring in future.
Variants of formal nearby cycles
Authors: Mieda Yoichi
Published: August 2013

In this paper, we introduce variants of formal nearby cycles for a locally noetherian formal scheme over a complete discrete valuation ring. If the formal scheme is locally algebraizable, then our nearby cycle gives a generalization of Berkovich’s formal nearby cycle. Our construction is entirely scheme theoretic, and does not require rigid geometry. Our theory is intended for applications to the local study of the cohomology of Rapoport–Zink spaces.
Agroecosystem resilience and farmers’ perceptions of climate change impacts on cocoa farms in Alto Beni, Bolivia
Authors: Jacobi Johanna , Schneider Monika , Bottazzi Patrick , Pillco Maria , Calizaya Patricia , Rist Stephan
Published: August 2013

Cocoa-based small-scale agriculture is the most important source of income for most farming families in the region of Alto Beni in the sub-humid foothills of the Andes. Cocoa is grown in cultivation systems of varying ecological complexity. The plantations are highly susceptible to climate change impacts. Local cocoa producers mention heat waves, droughts, floods and plant diseases as the main impacts affecting plants and working conditions, and they associate these impacts with global climate change. From a sustainable regional development point of view, cocoa farms need to become more resilient in order to cope with the climate change related effects that are putting cocoa-based livelihoods at risk. This study assesses agroecosystem resilience under three different cocoa cultivation systems (successional agroforestry, simple agroforestry and common practice monocultures). In a first step, farmers’ perceptions of climate change impacts were assessed and eight indicators of agroecological resilience were derived in a transdisciplinary process (focus groups and workshop) based on farmers’ and scientists’ knowledge. These indicators (soil organic matter, depth of Ah horizon, soil bulk density, tree species diversity, crop varieties diversity, ant species diversity, cocoa yields and infestation of cocoa trees with Moniliophthora perniciosa) were then surveyed on 15 cocoa farms and compared for the three different cultivation systems. Parts of the socio-economic aspects of resilience were covered by evaluating the role of cocoa cooperatives and organic certification in transitioning to more resilient cocoa farms (interviews with 15 cocoa farmers combined with five expert interviews). Agroecosystem resilience was higher under the two agroforestry systems than under common practice monoculture, especially under successional agroforestry. Both agroforestry systems achieved higher cocoa yields than common practice monoculture due to agroforestry farmers’ enhanced knowledge regarding cocoa cultivation. Knowledge sharing was promoted by local organizations facilitating organic certification. These organizations were thus found to enhance the social process of farmers’ integration into cooperatives and their reorientation toward organic principles and diversified agroforestry.
Health care cost containment in Denmark and Norway: a question of relative professional status?
Authors: Andersen Lotte B.
Published: August 2013

The demand for publicly subsidised health care services is insatiable, but the costs can be contained in different ways: formal rules can limit access to and the number of subsidised services, demand and supply can be regulated through the price mechanism, the relevant profession can contain the costs through state-sanctioned self-regulation, and other professions can contain the costs (e.g. through referrals). The use of these cost containment measures varies between countries, depending on demand and supply factors, but the relative professional status of the health professions may help explain why different countries use cost containment measures differently for different services. This article compares cost containment measures in Denmark and Norway because these countries vary with regard to the professional status of the medical profession relative to other health care providers, while other relevant variables are approximately similar. The investigation is based on formal agreements and rules, historical documents, existing analyses and an analysis of 360 newspaper articles. It shows that high relative professional status seems to help professions to avoid user fees, steer clear of regulation from other professions and regulate the services produced by others. This implies that relative professional status should be taken into consideration in analyses of health care cost containment.
Concurrent dual-band envelope tracking GaN PA design and its 2D shaping function characterization
Authors: Cidronali Alessandro , Giovannelli Niccolò , Mercanti Massimiliano , Maddio Stefano , Manes Gianfranco
Published: August 2013

This paper presents the design of a high-power dual-band power amplifier (PA) for envelope tracking (ET) operation and its characterization in concurrent dual-band ET operation modes. The design approach relies on the specific actual signal probability distribution and the prototype was conceived for the WCDMA 3GPP DL signals. The paper discusses the impact of the ET-shaping function influence on the linearity versus mean efficiency trade-off, for both single and concurrent dual-band cases. The technique was applied to a concurrent 870 and 2140 MHz ET-PA designed around a GaN HEMT device. The ET friendly design method led to performance very close to those observed at each single band. Over a bandwidth of 100 MHz and for PAR = 6.5 dB, the measured results reported a mean DE better than 71 and 54%, with a peak power higher than 55 and 54 dBm, at the two frequency bands, respectively. When evaluated in concurrent dual-band mode with two WDCMA signals at 6.5 dB PAR each, the ET-PA exhibited an estimated average total power of 49.5 dBm with 57.1% average drain efficiency.
Output feedback elliptical orbital rendezvous via state‐dependent Riccati differential equations
Authors: Cui Nai‐Gang , Zhou Bin , Duan Guang‐Ren
Published: August 2013

This article studies spacecraft rendezvous with the target spacecraft in an arbitrary elliptical orbit. Based on the linearised Tschauner–Hempel equations, state‐dependent Riccati differential equation (RDE)‐based approaches are proposed to solve the problem. An observer‐based output feedback controller is established. To implement the proposed controller, only some forward‐type RDEs need to be integrated online, indicating that the controllers can be implemented online as long as some positive‐definite initial conditions are given. Moreover, it is shown analytically that the closed‐loop system under the proposed feedback controller is exponentially asymptotically stable. Numerical examples show the effectiveness of the proposed approach.
Robust switched current control of converters
Authors: Cervantes Ilse , Mendoza‐Torres Angelica , Emadi Ali , Diaz‐Diaz Irwin A.
Published: August 2013

In this study, a robust current switching control of converters is proposed. It is proved that the controller is able to guarantee global current regulation, as well as the maximum voltage and current ripple, simultaneously. Such features make it ideal for implementing power‐management strategies and to be used along fuel cells. The control scheme is shown to be robust against model uncertainty and since it is based on the piece‐continuous model instead of average models, it is suitable for operation under a wide range of conditions. Moreover, its complexity does not increase with the number of cells. Experimental evidence of the advantages and features of the proposed control is presented in a two‐cell boost converter.
Delay‐dependent robust dissipative filtering of stochastic genetic regulatory networks with time‐varying delays
Authors: Li Yanjiang , Liu Guo‐ping
Published: August 2013

This study deals with the problem of delay‐dependent dissipative filtering for genetic regulatory networks (GRNs) with norm‐bounded parameter uncertainties and time‐varying delays. It is assumed that the non‐linear function describing the feedback regulation satisfies the sector‐bounded condition. Improved delay‐dependent stochastic stability and filter design method for stochastic GRNs are obtained by applying the delay fractioning technique, Jensen inequalities and introducing some proper slack matrix variables. The conservatism caused by either model transformation or bounding techniques is reduced. Sufficient conditions of the robust stability and filtering problems are proposed, respectively. The filter, which can guarantee the resulting error system to be asymptotically stable in the mean‐square sense and satisfy a prescribed performance level for all delays no larger than a given upper bound, are constructed. A numerical example is provided to demonstrate effectiveness of the proposed results in this study.
Robust stability analysis based on finite impulse response scaling for discrete‐time linear time‐invariant systems
Authors: Hosoe Yohei , Hagiwara Tomomichi
Published: August 2013

In this study, we discuss a dynamic scaling approach exploiting the separator‐type robust stability condition for discrete‐time linear time‐invariant systems. We confine ourselves to a class of what we call finite impulse response (FIR) separators, and establish a systematic and practical framework of searching for an FIR separator satisfying the separator‐type condition. The first step is to give explicit structure of FIR separators suitable for dealing with a given set of structured uncertainties. The second step is to give an explicit linear matrix inequality condition for the analysis. In particular, a minimal realisation of an augmented system to be dealt with in FIR scaling is derived, which is non‐trivial and is very important in reducing the computational load in the numerical computation. Effectiveness of the developed framework is demonstrated numerically, through comparison with the conventional static scaling and μ ‐analysis.
Field evaluation of an enhanced rear signalling system for heavy trucks
Authors: Schaudt William A. , Bowman Darrell S. , Baker Stephanie , Hanowski Richard J. , Flanigan Chris
Published: August 2013

In 2008, heavy trucks were found to be 3.2 times more likely than other vehicles to be struck from behind in two‐vehicle fatal crashes. The U.S. Federal Motor Carrier Safety Administration awarded a contract to the Virginia Tech Transportation Institute to perform Phase III of the Enhanced Rear Signalling for Heavy Trucks project which was directed at investigating methods to reduce or mitigate those crashes where a heavy truck has been struck from behind by another vehicle. The focus of this article is to discuss the dynamic evaluation of the final Enhanced Rear Signalling countermeasure system on public roadways of Virginia. Results indicated that the system was robust in real‐world driving situations. The system performed well at detecting rear‐end crash threats, activating a trailer‐positioned warning‐light system, drawing the gazes of distracted following‐vehicle drivers back to the forward roadway and resulted in minor following‐vehicle unintended consequences. An increase in false alarm rate was found for the warning light activation system during low‐speed, high‐traffic‐density scenarios and the propensity of these false alarms should be addressed prior to a field operational test.
Evaluation of automated electric transportation deployment strategies: integrated against isolated
Authors: Fishelson James , Freckleton Derek , Heaslip Kevin
Published: August 2013

This study considers deployment paths for automated vehicles, evaluating the new approach of an evolutionary process of isolated deployment. Here, isolated, fully automated systems are developed from the ground‐up in areas with the greatest need/opportunity; over time, such systems can expand and become interconnected. This is an alternative to the integrated deployment strategies developed by the automated highway systems (AHS) program. Tellingly, AHS never settled on a specific deployment strategy because of disagreements among many of its members, but much of the research did include an integrated approach, whereby the technology progresses over time from manual driving to full automation. This study compares the two approaches, arguing that integrated deployment is fundamentally hampered by institutional hurdles and the difficulty of encouraging the large‐scale adoption necessary to achieve the most significant benefits of automation, including increased lane capacity and vehicle speed. It proposes that a predominantly isolated approach, accomplished with protocols and standards to allow for eventual interoperability of systems, can offer a superior path forward. This is especially attractive for bus rapid transit applications and electrification via in‐motion power, as proposed by the Automated Electric Transportation program.
Video‐based traffic data collection system for multiple vehicle types
Authors: Li Shuguang , Yu Hongkai , Zhang Jingru , Yang Kaixin , Bin Ran
Published: August 2013

Traffic data of multiple vehicle types are important for pavement design, traffic operations and traffic control. A new video‐based traffic data collection system for multiple vehicle types is developed. By tracking and classifying every passing vehicle under mixed traffic conditions, the type and speed of every passing vehicle are recognised. Finally, the flows and mean speeds of multiple vehicle types are output. A colour image‐based adaptive background subtraction is proposed to obtain more accurate vehicle objects, and a series of processes like shadow removal and setting road detection region are used to improve the system robustness. In order to improve the accuracy of vehicle counting, the cross‐lane vehicles are detected and repeated counting for one vehicle is avoided. In order to reduce the classification errors, the space ratio of the blob and data fusion are used to reduce the classification errors caused by vehicle occlusions. This system was tested under four different weather conditions. The accuracy of vehicle counting was 97.4% and the error of vehicle classification was 8.3%. The correlation coefficient of speeds detected by this system and radar gun was 0.898 and the mean absolute error of speed detection by this system was only 2.3 km/h.
Speed impacts of an icy curve warning system
Authors: Veneziano David , Ye Zhirui , Turnbull Ian
Published: August 2013

Icy pavements can impair the ability of drivers to operate their vehicles safely. The California Department of Transportation has deployed an icy curve warning system (ICWS) on a five‐mile segment of SR 36 in Lassen County. This section of roadway has a history as a high‐crash location with fatal crashes, the vast majority of which occurred during icy pavement. The objective of this study was to evaluate operational effects of the ICWS, specifically on speeds during various conditions. The results of statistical analysis found that mean speeds were significantly different by greater than 5 mph when the system was on against off in general, as well as when examined by day and night. Mean speeds were significantly reduced by greater than 5 mph during wet weather (during day and night). The real interest of the evaluation was the system's impacts on reducing speeds during conditions when ice was present but unexpected (called clear, cold and not dry in this work). Statistical analysis found that mean speed reductions were significant by greater than 3 mph (but less than 5 mph) when the system was on both during the day and at night. Consequently, the ICWS appears to reduce speeds by approximately 3 mph in conditions where icy roads are unexpected.
Improved adaptive neuro fuzzy inference system car‐following behaviour model based on the driver–vehicle delay
Authors: Khodayari Alireza , Ghaffari Ali , Kazemi Reza , Alimardani Fatemeh , Braunstingl Reinhard
Published: August 2013

In the past decades, different forms of car‐following behaviour model have been intensively studied, proposed and implemented. These models are increasingly used by transportation experts to utilise for appropriate intelligent transportation systems. Unlike previous works, where the reaction delay is considered to be fixed, an improved adaptive neuro fuzzy inference system (ANFIS) model is proposed to simulate and predict the car‐following behaviour based on the reaction delay of the driver–vehicle unit. An idea is proposed to calculate the reaction delay. In this model, the reaction delay is used as an input and other inputs–outputs of the model are chosen with respect to this parameter. Using the real‐world data, the performance of the model is evaluated and compared with the responses of other existing ANFIS car‐following models. The simulation results show that the proposed model has a very close compatibility with the real‐world data and reflects the situation of the traffic flow in a more realistic way. Also, the comparison shows that the error of the proposed model is smaller than that in the other models.
Concept and development of a unified ontology for generating test and use‐case catalogues for assisted and automated vehicle guidance
Authors: Geyer Sebastian , Baltzer Marcel , Franz Benjamin , Hakuli Stephan , Kauer Michaela , Kienle Martin , Meier Sonja , Weißgerber Thomas , Bengler Klaus , Bruder Ralph , Flemisch Frank , Winner Hermann
Published: August 2013

Activities in the field of automated driving have produced a variety of development tools and methodologies over the past decades. The requirements the systems have to fulfil and thus also the development guidelines are often documented in different kinds of catalogues (use‐case catalogues, situation catalogues, scenario catalogues etc.). These catalogues cannot be directly applied for the development of partially and highly automated vehicle guidance concepts like conduct‐by‐wire (CbW) or H‐mode. One reason is that up to now, no consistent terminology known to the authors yet exists for vehicle automation within the community. Moreover, as the aim of the two project groups CbW and H‐mode is to make a comprehensive feasibility assessment of cooperative vehicle guidance, all interacting components of the overall system as well as all potential driving conditions a cooperative vehicle guidance system might have to cope with have to be analysed. This article focuses on two aspects. The first is a metaphor‐based terminology discussion leading to a proposal for a fundamental ontology. The second aspect is an outlook on the different catalogues that use the new terminology and that have been developed. The methodology introduced here is a fundamental contribution towards simplifying communication and the exchange of findings.
Velocity difference control based on dynamic tracking of safe following distance in the process of vehicle following
Authors: Pan Deng , Zheng Yingping
Published: August 2013

To improve the quality of vehicular following behaviour in safety and efficiency, a new method, which combines the velocity difference control with the dynamic tracking of safe following distance closely, is presented to realise the dynamic optimisation of the following vehicle's behaviour and the spatial interval between the preceding and following vehicles. The corresponding mathematical model is given in this study, as well as control system design and the control algorithms for the following vehicle to adjust its own behaviour scientifically. Different from other vehicle following models, the fitting function is used to calculate dynamic safe following distance, which should be kept by the following vehicle from the preceding vehicle. The safe following distance can be obtained in real time by the following vehicle at any velocity from 0 to 500 km/h for the evaluation and the scientific adjustment of its own behaviour. The simulation verifies the feasibility and validity of this method, which can ensure the safe, efficient and smooth (comfort) operation of the following vehicle in its following process.
Power oscillation damping using wind turbines with energy storage systems
Authors: Xu Guoyi , Xu Lie , Morrow John
Published: August 2013

Wind turbines are increasingly being expected to provide oscillation damping to the power system to which they are connected. In this study, power oscillation damping control of variable speed wind turbines is studied. An energy storage device with a bidirectional DC/DC converter connected to the DC link of a fully rated converter‐based wind turbine is proposed. As system oscillation is often induced by an AC fault, it is desirable for wind turbines to ride through the fault first and then provide a damping effect. During the fault period, the energy storage system (ESS) is controlled to assist the fault ride through process, and the line side converter (LSC) is controlled to provide AC voltage support in accordance with the grid code. Methods based on regulating the active power output of the ESS and modulation of reactive power output of the LSC are proposed so as to damp the oscillations of the power system. Matlab/Simulink simulations based on a simplified Irish power system demonstrate the performance of the ESS and LSC during fault periods and validate the damping effect of the proposed system.
Analysis of linear wave power generator model with real sea experimental results
Authors: Krishna Remya , Svensson Olle , Rahm Magnus , Kottayil Sasi K. , Waters Rafeal , Leijon Mats
Published: August 2013

This study presents the dynamic modelling of a linear permanent magnet generator for extracting energy from ocean waves. Translator position, calculated from measured generator voltage, is used as input for the simulation model. Instantaneous power from the simulation model has been compared with the measurements from the Lysekil research site. The power output from the model considering the air gap flux variation is precisely matching with the measured values before core saturation. The generator dynamic model is modified by including the saturation effect. Although a simple mathematical expression is considered for representing the saturation, the model gives accurate power spectrum close to the experimental results. The presented model is a first step towards the system model that can simulate the entire electric system including electric grid. As such, the generator model can be used for further analysis of the wave energy conversion system.
Decision support system for ranking photovoltaic technologies
Authors: Azzopardi Brian , Martínez‐Ceseña Eduardo A. , Mutale Joseph
Published: August 2013

The primary photovoltaic (PV) system investment decision‐making criteria are economics. These criteria are focused on system efficiency and cost, which is reasonable in the context of generous financial support schemes. However, when financial support is phased out, the PV market becomes technologically diversified. Environmental concerns and other qualitative issues become significant, whereas efficiency and costs may fail to describe PV systems properly. This study presents the first application of outranking techniques for PV technologies within an overall framework that includes qualitative, economic, technical and environmental criteria. The multi‐criteria analysis method, ELECTRE III, identifies optimal investment decisions from a pre‐determined set of investment alternatives. A case study based on a grid‐connected household PV system in the United Kingdom illustrates the methodology. The results suggest emerging excitronic PV technologies such as organic PV to lead the ranking when compared with inorganic technologies. These results have to be taken in the context of a number of assumptions and estimates as well as free market, no financial support schemes and promising future technology developments. The overall decision‐making framework provides comprehensive mathematical evaluations that assist PV owners, policy makers and the business community decide on technology, financial support schemes or business strategies.
Analysis of positive ramp limitation control strategies for reducing wind power fluctuations
Authors: Martín‐Martínez Sergio , Gómez‐Lázaro Emilio , Vigueras‐Rodríguez Antonio , Fuentes‐Moreno Juan Alvaro , Molina‐García Angel
Published: August 2013

Power fluctuations could have a remarkable impact on power system operation and costs, in accordance with the increasing production of wind power worldwide. In systems with weak interconnections, such as Iberian Peninsula Power System, these fluctuations could be a security issue. In order to characterise the worst effects on power systems of wind power fluctuations, most negative wind power ramp rates can be used. In this study, one‐year real data production of 17 wind farms, scattered over Spain, is analysed regarding the geographical smoothing effect on negative wind power ramp rates. Several control strategies are suggested to reduce the resulting aggregated negative ramps. For each strategy, the controlled power is compared with uncontrolled power output, studying the achieved reduction in negative ramps. The results give a comparison of such strategies, regarding energy losses and improvement for power system operation.
Statistical profiling of site wind resource speed and directional characteristics
Authors: Stephen Bruce , Galloway Stuart , McMillan David , Anderson Lucy , Ault Graham
Published: August 2013

Construction of a wind farm without a reliable plant margin forecast can jeopardise potential returns on investment from the outset. Meteorological and topological factors influence the wind characteristics across any site which in turn affects wind farm output, critical for localised generation, and also the dynamic loading of the turbine structure. The models developed in this study follow the generally advocated use of probability density estimation as a means of representing wind resource characteristics but, owing to differences, in characterisation that may be encountered, do not assume a single distribution form across all sites. A mixture modelling approach is adopted that removes the need for choosing distribution forms on a site by site basis. Advancing previous work constructing statistical distributions over congruent wind speed and direction observations of the wind resource characteristics at a given site, the proposed model, as a consequence of using a mixture distribution, captures both recurring regimes in the site behaviour along with their frequency of occurrence. Preliminary results using data sets from a diverse range of locations in Scotland demonstrate the variation in the forms of model learned; comparisons of the model with current and alternate practices are given through visualisation and resource assessment illustrations.
Multi‐objective expansion planning approach: distant wind farms and limited energy resources integration
Authors: Javadi Mohammad Sadegh , Saniei Mohsen , Mashhadi Habib Rajabi , Gutiérrez‐Alcaraz Guillermo
Published: August 2013

This study presents a multi‐objective framework to evaluate the integration of distant wind farms with associated transmission network upgrades on optimal power system planning. The presented approach also extends the technique to include the consideration of energy limitations associated with the installed hydro generation facilities. This study attempts to emphasise on the reliability implications rather than the production cost evaluation aspects. The decision making is based on hierarchal level II (HL‐II) Expected Energy Not Served as an entire power system reliability assurance, and capital cost plus annual operational cost as an economical index. Non‐dominated Sorting Genetic Algorithm is adopted to achieve the Pareto front of the aforementioned multi‐objective problem. A fuzzy satisfying method, designated as the distance metric, is used to represents a trade‐off between different objectives. To numerically evaluate the efficiency of the proposed method, simulation results on three case studies are provided. In spite of huge computation burden at HL‐II reliability assessment, the results indicate high efficiency of the proposed method.
Accommodating renewable generation through an aggregator‐focused method for inducing demand side response from electricity consumers
Authors: Boait Peter , Ardestani Babak Mahdavi , Snape Joseph Richard
Published: August 2013

The ability to influence electricity demand from domestic and small business consumers, so that it can be matched to intermittent renewable generation and distribution network constraints is a key capability of a smart grid. This involves signalling to consumers to indicate when electricity use is desirable or undesirable. However, simply signalling a time‐dependent price does not always achieve the required demand response and can result in unstable system behaviour. The authors propose a demand response scheme, in which an aggregator mediates between the consumer and the market and provides a signal to a ‘smart home’ control unit that manages the consumer's appliances, using a novel method for reconciliation of the consumer's needs and preferences with the incentives supplied by the signal. This method involves random allocation of demand within timeslots acceptable to the consumer with a bias depending on the signal provided. By simulating a population of domestic consumers using heat pumps and electric vehicles with properties consistent with UK national statistics, the authors show the method allows total demand to be predicted and shaped in a way that can simultaneously match renewable generation and satisfy network constraints, leading to benefits from reduced use of peaking plant and avoided network reinforcement.
Capacity credit of concentrating solar power
Authors: Usaola Julio
Published: August 2013

Concentrating solar power technology (CSP) will probably become increasingly present in power systems and will have to be included in generation adequacy studies. CSP has two special features which makes it different from other technologies: its daily and seasonal cycle and its possibility of storage. This study proposes a sequential Monte Carlo method, which includes series of possible trajectories of CSP production to find the capacity value of this technology. From the generated CSP production trajectories, values of loss of load probability, equivalent load carrying capacity and equivalent conventional power plant are calculated. Different hypotheses are considered, in order to study the effect of location of CSP plants, their storage capacity and demand profile on capacity credit. The study has a two fold objective: it intends to propose a way of including CSP in generation adequacy studies, and gives representative values of the contribution of this technology to overall power system reliability.
Wide‐area measurement signal‐based stabiliser for large‐scale photovoltaic plants with high variability and uncertainty
Authors: Shah Rakibuzzaman , Mithulananthan Nadarajah , Lee Kwang Y. , Bansal Ramesh C.
Published: August 2013

In this study, norm bounded linear quadratic Gaussian controller synthesis method is utilised to design a wide‐area measurement signal (WAMS)‐based power oscillation damping controller at photovoltaics (PV) plants. The uncertainties associated with the system are confined by the system matrices which are the affine functions of parameters belong to a convex polytopic region. A hybrid method based on Hankel singular value (HSV) and right‐half‐plane zeros (RHP‐zeros) is utilised to assess and select the optimal feedback signal for the PV wide‐area damping controller. First, the HSVs of the delayed subsystems are employed to preselect the candidate signals for damping the target mode. Then, the RHP‐zeros and the modal interaction measures of the candidate signals are evaluated. Finally, the signal with minimum variance in HSV and modal interaction over the wide range of operating conditions is selected as the optimal feedback signal for the controller design. The wide range of operating conditions is obtained by the probabilistic distribution of loads, synchronous generators and PVs. The approach has been tested on a large 16 machine, 68 bus test system as compared to geometric measures of controllability/observability method and has shown improved performance.
Improved distributed estimation method for environmental physical variables in static sensor networks
Authors: Mahmoud Magdi S. , Khalid Haris M. , Sabih Muhammad
Published: August 2013

In this study, an improved distributed estimation scheme for static sensor networks is developed. The scheme is developed for environmental time‐variant physical variables. The main contribution of this work is that the algorithm in Saber and Murray (2005), Carli et al. (2009) and Xiao et al. (2004) has been extended, and a filter has been designed with weights, such that the variance of the estimation errors is minimised, thereby improving the filter design considerably and characterising the performance limit of the filter, and thereby tracking a time‐varying signal. Moreover, certain parameter optimisation is alleviated with the application of a particular finite impulse response filter. Simulation results are showing the effectiveness of the developed estimation algorithm.
Low‐complexity distributed multiple description coding for wireless video sensor networks
Authors: Liu Wenhui , Vijayanagar Krishna R. , Kim Joohee
Published: August 2013

Quality‐of‐service‐guaranteed video communication in wireless video sensor networks (WVSNs) is extremely challenging because of the unique constraints of WVSN (e.g. limited resources of sensors and high error rates in wireless sensor networks) and the characteristics of video traffic (e.g. huge data rate and tight delay bounds). Distributed video coding (DVC) has emerged as a new video coding paradigm for video applications with resource‐limited encoders. However, current DVC architectures still have several technical limitations that prevent their widespread use in real‐world applications. A low‐complexity distributed multiple description coding method that combines the principles of multiple description coding and DVC has been proposed to further improve the error resilience of DVC, while maintaining low encoder complexity and good rate‐distortion performance in WVSN. Simulation results show that the proposed method is robust against transmission errors, while maintaining low encoder complexity and low system latency for resource‐limited applications in WVSNs.
Realisation of a cluster‐based protocol using fuzzy C‐means algorithm for wireless sensor networks
Authors: Hoang Duc Chinh , Kumar Rasjesh , Panda Sanjib Kumar
Published: August 2013

In this study, real‐time design and implementation of an energy‐efficient cluster‐based protocol for wireless sensor networks (WSNs) are presented. The formation of suitable clusters is of prime importance to balance energy usage by sensor nodes within each cluster of the cluster‐based WSNs. This leads to energy savings for the sensor nodes resulting in longer network lifetime. To obtain this objective, the fuzzy C‐means (FCM) clustering algorithm is incorporated in the protocol. The protocol is realised on a hardware test‐bed with the support of the embedded operating system, TinyOS. Experimental results obtained from a scale‐down laboratory based test‐bed with up to 50 sensor nodes are provided to illustrate the efficacy of the WSNs using the proposed protocol and compared with the well‐known cluster‐based protocols such as Low Energy Adaptive Clustering Hierarchy. It has been shown that the FCM protocol is able to achieve better organisation of the network and thus can extend its lifetime under varying operating conditions and with different number of nodes.
Sub‐optimum fast Bayesian techniques for joint leak detection and localisation
Authors: Roufarshbaf Hossein , Castro Joel , Schwaner Fred , Abedi Ali
Published: August 2013

A fast tree‐search algorithm for joint leak detection and localisation using surface‐borne ultrasonic acoustic signals is developed through a wireless sensor network. Owing to environmental noise and multipath fading of ultrasonic signals, false sensor observations are frequent in the observation data. The problem is modelled as a Bayesian inference model and the maximum a posteriori solution is approximated through a tree‐search structure. The algorithm initially divides the area into large cells and approximates the observation likelihood function over these large cells. In a tree structure, a large cell with high likelihood is divided into smaller cells and the tree is expanded until the required estimation precision is obtained. Simulation and experimental results reveal advantages of the proposed technique in terms of estimation error and convergence speed in comparison with other conventional Bayesian techniques such as particle filtering.