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Experiment Shows (experiment + shows)
Selected AbstractsAcquiring knowledge with limited experienceEXPERT SYSTEMS, Issue 3 2007Der-Chiang Li Abstract: From computational learning theory, sample size in machine learning problems indeed affects the learning performance. Since only few samples can be obtained in the early stages of a system and fewer exemplars usually lead to a low learning accuracy, this research compares different machine learning methods through their classification accuracies to improve small-data-set learning. Techniques used in this paper include the mega-trend diffusion technique, a backpropagation neural network, a support vector machine, and decision trees to explore the machine learning issue with two real medical data sets concerning cancer. The result of the experiment shows that the mega-trend diffusion technique and backpropagation approaches are effective methods of small-data-set learning. [source] Developmental, metabolic and immunological costs of flea infestation in the common voleFUNCTIONAL ECOLOGY, Issue 6 2008Godefroy Devevey Summary 1Parasites use resources from their hosts, which can indirectly affect a number of host functions because of trade-offs in resource allocation. In order to get a comprehensive view of the costs imposed by blood sucking parasites to their hosts, it is important to monitor multiple components of the development and physiology of parasitized hosts over long time periods. 2The effect of infestation by fleas on body mass, body length growth, haematocrit, resistance to oxidative stress, resting metabolic rate and humoral immune response were experimentally evaluated. During a 3-month period, male common voles, Microtus arvalis, were either parasitized by rat fleas (Nosopsyllus fasciatus), which are naturally occurring generalist ectoparasites of voles, or reared without fleas. Then voles were challenged twice by injecting Keyhole Limpet Haemocyanin (KLH) to assess whether the presence of fleas affects the ability of voles to produce antibodies against a novel antigen. During the immune challenge we measured the evolution of body mass, haematocrit, resistance to oxidative stress and antibody production. 3Flea infestation negatively influenced the growth of voles. Moreover, parasitized voles had reduced haematocrit, higher resting metabolic rate and lower production of antibodies against the KLH. Resistance to oxidative stress was not influenced by the presence of fleas. 4During the immune challenge with KLH, body mass decreased in both groups, while the resistance to oxidative stress remained stable. In contrast, the haematocrit decreased only in parasitized voles. 5Our experiment shows that infestation by a haematophageous parasite negatively affects multiple traits like growth, energy consumption and immune response. Fleas may severely reduce the survival probability and reproductive success of their host in natural conditions. [source] Thermal performance of a packed bed reactor for a high-temperature chemical heat pumpINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2001Yukitaka Kato Abstract The thermal performance of a chemical heat pump that uses the reaction system of calcium oxide/lead oxide/carbon dioxide, which is developed for utilization of high-temperature heat above 800°C, is studied experimentally. The thermal performance of a packed-bed reactor of a calcium oxide/carbon dioxide reaction system, which stores and transforms a high-temperature heat source in the heat pump operation, is examined under various heat pump operation conditions. The energy analysis based on the experiment shows that it is possible to utilize high-temperature heat with this heat pump. This heat pump can store heat above 850°C and then transform it into a heat above 900°C under an approximate atmospheric pressure. An applied system that combines the heat pump and a high-temperature process is proposed for high-efficiency heat utilization. The scale of the heat pump in the combined system is estimated from the experimental results. Copyright © 2001 John Wiley & Sons, Ltd. [source] Life history and fitness consequences of ectoparasitesJOURNAL OF ANIMAL ECOLOGY, Issue 2 2004Patrick S. Fitze Summary 1For iteroparous organisms life-history theory predicts a trade-off between current and future reproduction, and therefore the evolution of host responses to current parasite infestation that will maximize lifetime reproductive success. The parasite-induced variation in reproductive success is thus not the net result of parasite infestation alone, but the parasite-mediated outcome of optimal resource allocation among current and future reproductive events. Understanding the importance of parasites for the evolution of host life history therefore requires an experimental investigation of the effects of parasites over the host's life span. Such studies are currently scant. 2We manipulated the load of an ectoparasite, the hen flea (Ceratophyllus gallinae), in the nests of its most common host, the great tit (Parus major), over a period of 4 years and recorded, the components of current and future reproductive success including survival, divorce, breeding dispersal and various reproductive parameters. Finally we assessed, for females only as paternity of males was unknown, the lifetime reproductive success as a close correlate of Darwinian fitness. 3For current reproduction, our experiment demonstrates that parasites reduce current reproductive success via an increase in the probability of nest failure during incubation and the nestling period. In the presence of fleas, clutch size and the number of fledglings were reduced while the incubation and the nestling period were prolonged. Thus parasitism led to an increase in parental effort but nevertheless reduced current reproductive success. 4For future reproduction, the experiment shows that females breeding in infested nests dispersed over longer distances between breeding attempts. The divorce rate following infestation, the probability of breeding locally in the future and residual reproductive success were not affected significantly by ectoparasites. The study thus suggests that hen fleas play a minor role in shaping the trade-off between current and future reproduction. 5Lifetime reproductive success of females, measured as the total number of locally recruiting offspring over the 4 experimental years, was reduced significantly by ectoparasites. The negative effect of parasites arose by a reduction of the number of fledglings per breeding attempt rather than by a reduction of the number of breeding attempts. [source] Traditional versus unobserved components methods to forecast quarterly national account aggregatesJOURNAL OF FORECASTING, Issue 2 2007Gustavo A. Marrero Abstract We aim to assess the ability of two alternative forecasting procedures to predict quarterly national account (QNA) aggregates. The application of Box,Jenkins techniques to observed data constitutes the basis of traditional ARIMA and transfer function methods (BJ methods). The alternative procedure exploits the information of unobserved high- and low-frequency components of time series (UC methods). An informal examination of empirical evidence suggests that the relationships between QNA aggregates and coincident indicators are often clearly different for diverse frequencies. Under these circumstances, a Monte Carlo experiment shows that UC methods significantly improve the forecasting accuracy of BJ procedures if coincident indicators play an important role in such predictions. Otherwise (i.e., under univariate procedures), BJ methods tend to be more accurate than the UC alternative, although the differences are small. We illustrate these findings with several applications from the Spanish economy with regard to industrial production, private consumption, business investment and exports.,,Copyright © 2007 John Wiley & Sons, Ltd. [source] Aggregation of Fillers Blended into Random Elastomeric Networks: Theory and Comparison with ExperimentsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2006Mustafa M. Demir Abstract Summary: A theoretical model describing aggregation of filler particles in amorphous elastomers is proposed. The model is based on a counting technique originally used in genome analysis to characterize the size and distribution of overlapping segments randomly placed on a DNA molecule. In the present model, the particles are first assumed to aggregate randomly upon mixing into the elastomer and their sizes are calculated. The sizes and distributions of aggregates are also studied in the presence of attractive interparticle forces. Results of the proposed model are compared with experimental data on silica-filled end-linked poly(dimethylsiloxane) networks. Comparison of the theory and experiment shows that the random aggregation assumption where no attractive forces exist between the particles is not valid and a significant attraction between the silica particles is needed in the theory to justify the experimental data obtained using atomic force microscopy. For filler content below 1.45 vol.-%, the model agrees, qualitatively, with experiment and shows the increase in cluster size with increasing amount of filler. It also explains the increase in the dispersion of aggregate sizes with increasing amount of filler. Clustering of the primary silica particles in an imaginary volume of poly(dimethylsiloxane) network. [source] Enhancement of magnetoimpedance effect in Co-based amorphous ribbon with a meander structurePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2010Lei Chen Abstract A model for the enhanced giant magnetoimpedance (GMI) effect in field-annealed Co-based ribbon with a meander structure is developed. Three different kinds of ribbon are fabricated by a MEMS method and the field dependence of the GMI effect is measured at 10,MHz. Good agreement between theory and experiment shows the validity of this model. A larger change of inductance L in the meander structure results in the increasing of impedance Z and the enhanced GMI effect. [source] Sintering of porous siliconPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003G. Müller Abstract In this paper we study the dynamics of pore coarsening in porous silicon during annealing. We model the sintering of pores with two-dimensional and three-dimensional simulations. We compare our simulations with transmission and scanning electron micrographs of experimentally annealed porous silicon samples. Simulations and experiments yield lognormally distributed pore sizes. The quantitative agreement between simulation and experiment shows that minimization of the inner surface energy is the driving force for morphological changes in PS during annealing. Surface diffusion is the dominant mechanism in the reorganization of Si-atoms in PS. [source] Focusing on Customer Time in Field Service: A Normative ApproachPRODUCTION AND OPERATIONS MANAGEMENT, Issue 2 2007Aruna Apte Although customer convenience should be rightfully considered a central element in field services, the customer experience suggests that service enterprises rarely take the customer's preferred time into account in making operational and scheduling decisions. In this paper we present the results of our exploratory research into two interrelated topics: the explicit inclusion of customer time in nonemergency field service delivery decisions and the analysis of trade-off between the customer's convenience and field service provider's cost. Based on prior research in service quality we identify and illustrate two time-based performance metrics that are particularly appropriate for assessing service quality in nonemergency field services: performance and conformance quality. To determine vehicle routes, we develop a hybrid heuristic derived from the existing and proven heuristic methods. A numerical example closely patterned after real-life data is generated and used within a computational experiment to investigate alternate policies for promise time windows. Our experiment shows that over a reasonable range of customer cost parameters the policy of shorter promise time windows reduces the combined total cost incurred by the provider and the customers and should be considered a preferred policy by the field service provider. Managerial implications of this result are discussed. [source] Robust Estimation and Outlier Detection for Overdispersed Multinomial Models of Count DataAMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 2 2004Walter R. Mebane Jr. We develop a robust estimator,the hyperbolic tangent (tanh) estimator,for overdispersed multinomial regression models of count data. The tanh estimator provides accurate estimates and reliable inferences even when the specified model is not good for as much as half of the data. Seriously ill-fitted counts,outliers,are identified as part of the estimation. A Monte Carlo sampling experiment shows that the tanh estimator produces good results at practical sample sizes even when ten percent of the data are generated by a significantly different process. The experiment shows that, with contaminated data, estimation fails using four other estimators: the nonrobust maximum likelihood estimator, the additive logistic model and two SUR models. Using the tanh estimator to analyze data from Florida for the 2000 presidential election matches well-known features of the election that the other four estimators fail to capture. In an analysis of data from the 1993 Polish parliamentary election, the tanh estimator gives sharper inferences than does a previously proposed heteroskedastic SUR model. [source] Transfer Price Negotiation in the Presence of Unequal Bargaining Power: The Effect of a Peer Evaluation Scheme on Inter-divisional Profit DistributionAUSTRALIAN ACCOUNTING REVIEW, Issue 3 2009Mandy M. Cheng This study examines how managers balance economic incentives and inter-divisional equity considerations during transfer price negotiations. Our experiment shows that both buyers and sellers are willing to give up a significant amount of their profits to pursue a more equitable outcome (one that results in greater inter-divisional profit equalisation). We also find that incorporating peer evaluation schemes into negotiators' formal incentive plans has both economic and social-psychological impacts on negotiation behaviour, resulting in even greater inter-divisional profit equalisation. While this outcome may seem ,fairer' to the individual managers, from the firms' perspective profit equalisation can obscure divisional performance, potentially leading to resource allocation inefficiencies. [source] ECCD Experiments Using the Upgraded Launching System in Heliotron JCONTRIBUTIONS TO PLASMA PHYSICS, Issue 6-7 2010K. Nagasaki Abstract Electron cyclotron current drive (ECCD) experiments have been made in Heliotron J by using an upgraded EC launching system. A focused Gaussian beam is injected with the parallel refractive index, N||, ranging from -0.05 to 0.6. Ray tracing calculation shows that the EC power is more localized than that in the previous launching system. In the initial ECCD experiment, the EC injection angle has been successfully scanned as designed. Comparison between perpendicular and oblique launching experiments shows that for standard configuration, the EC current of 1 kA is driven at N|| , 0.3 in the Fisch-Boozer direction, and the bootstrap current flows up to 1 kA. A large increase in electron cyclotron emission (ECE) signals has been observed when the EC current was driven (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reciprocal relationships and potential feedbacks between biodiversity and disturbanceECOLOGY LETTERS, Issue 9 2007A. Randall Hughes Abstract Two major foci of ecological research involve reciprocal views of the relationship between biodiversity and disturbance: disturbance determines community diversity or diversity determines realized disturbance severity. Here, we present an initial attempt to synthesize these two approaches in order to understand whether feedbacks occur, and what their effects on patterns of diversity might be. Our review of published experiments shows that (i) disturbance severity can be both a cause and a consequence of local diversity in a wide range of ecosystems and (ii) shapes of the unidirectional relationships between diversity and disturbance can be quite variable. To explore how feedbacks between diversity and disturbance might operate to alter expected patterns of diversity in nature, we develop and then evaluate a conceptual model that decomposes the relationships into component parts, considering sequentially the effect of diversity on disturbance severity, and the effect of realized disturbance on diversity loss, subsequent recruitment, and competitive exclusion. Our model suggests that feedbacks can increase mean values of richness, decrease variability, and alter the patterns of correlation between diversity and disturbance in nature. We close by offering ideas for future research to help fill gaps in our understanding of reciprocal relationships among ecological variables like diversity and disturbance. [source] Heat conduction in granular materialsAICHE JOURNAL, Issue 5 2001Watson L. Vargas Heat transfer in particulate systems is important to a vast array of industries, yet is poorly understood even in the simplest case,conduction through the solid phase. This is due in part to the stress and contact heterogeneities inherent to these systems. Heat conduction in a packet bed of cylinders is investigated both experimentally and computationally. A novel model is developed based on the Discrete Element Method, which not only sheds light on fundamental issues in heat conduction in particles, but also provides a valuable test bed for existing theories. By explicitly modeling individual particles within the bulk material, bed heterogeneities are directly included, and dynamic temperature distributions are obtained at the particle level. Comparison with experiments shows that this model yields a quantitatively accurate temperature field without the need for adjustable parameters or detailed microstructural information. This simple system may also provide insight into such phenomena as reactor hot spot formation and spontaneous combustion of bulk reactive materials. [source] Feeding trials in organic food quality and health researchJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 2 2010Alberta Velimirov Abstract Feeding experiments comparing organically and conventionally produced food are performed to assess the overall impact on the animals' health as a model for the effects experienced by the human consumers. These experiments are based on systems research and characterized by their focus on production methods, whole food testing and procedures in accordance with the terms of organic farming. A short review of such experiments shows that the majority of these tests revealed effects of the organically produced feed on health parameters such as reproductive performance and immune responses. Systems research is not just about simple cause,effect chains, but rather about the pluralism of interactions in biological networks; therefore, the interpretation of the outcome of whole food experiments is difficult. Furthermore, the test diets of organic and conventional origin can be constituted in different ways, compensating for or maintaining existing differences in nutrient and energy contents. The science-based results suggest positive influences from organic feeds, but there is still a need for confirmation in animals and, finally, in humans. For this purpose animal feeding trials with feed from different production systems should be conducted, with the aims to define health indicators and to establish biomarkers as a basis for future dietary intervention studies in humans. Copyright © 2009 Society of Chemical Industry [source] The ,ghosts' that pester studies on learning in mosquitoes: guidelines to chase them offMEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2006W. J. ALONSO Abstract The identification of memory and learning in medically important mosquito species has been of epidemiological interest mainly because of the implications of learning on the pattern of contact between vectors and hosts. Empirical results either showing or suggesting the existence of cognitive abilities in mosquitoes have been reported in a number of experimental studies, mainly based on the observation of individual fidelity towards subsets of specific resources, such as hosts, resting sites or breeding sites. A closer inspection of the design of these experiments shows that, with the exception of recent studies providing stronger evidence of learning in the genus Culex (Diptera: Culicidae), methodological shortcomings still hinder the possibility of eliminating alternative interpretations for these findings, in some cases because the experiments were not specifically designed to identify the phenomenon, but mostly because of a lack of appropriate controls or replication. By highlighting these limitations, while acknowledging the practical difficulties that are inherent to the field, we aim to help expel from future research the ,ghosts' that still preclude the achievement of more definite conclusions about the prevalence of memory and learning in this group of insects. [source] | ||||||||||||||||||||||