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Speed Only (speed + only)
Selected AbstractsNear-Term Travel Speed Prediction Utilizing Hilbert,Huang TransformCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 8 2009Khaled Hamad In this study, we propose an innovative methodology for such prediction. Because of the inherently direct derivation of travel time from speed data, the study was limited to the use of speed only as a single predictor. The proposed method is a hybrid one that combines the use of the empirical mode decomposition (EMD) and a multilayer feedforward neural network with backpropagation. The EMD is the key part of the Hilbert,Huang transform, which is a newly developed method at NASA for the analysis of nonstationary, nonlinear time series. The rationale for using the EMD is that because of the highly nonlinear and nonstationary nature of link speed series, by decomposing the time series into its basic components, more accurate forecasts would be obtained. We demonstrated the effectiveness of the proposed method by applying it to real-life loop detector data obtained from I-66 in Fairfax, Virginia. The prediction performance of the proposed method was found to be superior to previous forecasting techniques. Rigorous testing of the distribution of prediction errors revealed that the model produced unbiased predictions of speeds. The superiority of the proposed model was also verified during peak periods, midday, and night. In general, the method was accurate, computationally efficient, easy to implement in a field environment, and applicable to forecasting other traffic parameters. [source] The effects of morphology and substrate diameter on climbing and locomotor performance in male spidersFUNCTIONAL ECOLOGY, Issue 2 2010John Prenter Summary 1.,Spiders are the most sexually size dimorphic terrestrial animals and the evolution of this dimorphism is controversial. Patterns of sexual size dimorphism (SSD) in spiders have been related to individual performance and size. In 2002 Moya-Laraño, Halaj & Wise proposed the ,gravity hypothesis' to explain patterns of sexual size dimorphism in spiders whereby species building webs high in the vegetation are predicted to show greater SSD than those that build lower down. They advocated an advantage in climbing speed in smaller males searching for females in high places. The gravity hypothesis predicts a negative relationship between male size and climbing speed. In 2007 Brandt & Andrade questioned this interpretation and proposed that the pattern of SSD in spiders is better explained by an advantage for larger males of low-dwelling species to run faster along the ground. 2.,We induced male spiders to run a standard distance up vertical poles of different diameters to examine the predicted relationship between size and climbing speed. We tested two species of extremely size-dimorphic orb-web spiders, Argiope keyserlingi and Nephila plumipes, that differ in the height at which females tend to build webs, and one species of jumping spider, Jacksonoides queenslandica, with low levels of size dimorphism. We also examined morphological determinants of horizontal motility by inducing males to run along a raceway. 3.,Substrate diameter was consistently found to influence climbing performance. In N. plumipes, climbing speed was slowest on the widest diameter substrate. In A. keyserlingi, size-adjusted leg length and substrate diameter interacted to determine climbing speed, while in J. queenslandica, there was an interaction between body size and substrate diameter on climbing speed. In the effect of substrate diameter, we have identified a potential bias in previous tests of the gravity hypothesis. 4.,Our results do not support the prediction of the gravity hypothesis. There was no evidence of a negative relationship between body size and climbing speed in the two orb-web species with high levels of SSD. Our results are also not consistent with a recent modification of the gravity hypothesis that suggests a curvilinear relationship between climbing speed and size. 5.,Body size was positively associated with maximum running speed only in the cursorial hunter J. queenslandica. For this spider, results are more consistent with Brandt & Andrade's explanation for variation in SSD in spiders, that larger males are selected for superior running ability in low-dwelling species, rather than selection for smaller size for climbing to females in high-dwelling species. [source] Survival selection on escape performance and its underlying phenotypic traits: a case of many-to-one mappingJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2009F. STROBBE Abstract Selection often operates not directly on phenotypic traits but on performance which is important as several traits may contribute to a single performance measure (many-to-one mapping). Although largely ignored in the context of selection, this asks for studies that link all relevant phenotypes with performance and fitness. In an enclosure experiment, we studied links between phenotypic traits, swimming performance and survival in two Enallagma damselflies. Predatory dragonflies imposed survival selection for increased swimming propensity and speed only in E. annexum; probably E. aspersum was buffered by the former species' presence. Accordingly, more circular caudal lamellae, structures involved in generating thrust while swimming, were selected for only in E. annexum. Other phenotypic traits that contributed to swimming speed were apparently not under selection, probably because of many-to-one mapping (functional redundancy). Our results indicate that not only the phenotypic distributions of syntopic prey organisms but also many-to-one mapping should be considered when documenting phenotype,performance,fitness relationships. [source] Diversity in academic medicine no. 3 struggle for survival among leading diversity programsMOUNT SINAI JOURNAL OF MEDICINE: A JOURNAL OF PERSONALIZED AND TRANSLATIONAL MEDICINE, Issue 6 2008A. Hal Strelnick MD Abstract Since efforts to increase the diversity of academic medicine began shortly after the Civil War, the efforts have been characterized by a ceaseless struggle of old and new programs to survive. In the 40 years after the Civil War, the number of minority-serving institutions grew from 2 to 9, and then the number fell again to 2 in response to an adverse evaluation by the Carnegie Foundation for the Advancement of Teaching. For 50 years, the programs grew slowly, picking up speed only after the passage of landmark civil rights legislation in the 1960s. From 1987 through 2005, they expanded rapidly, fueled by such new federal programs as the Centers of Excellence and Health Careers Opportunity Programs. Encompassing majority-white institutions as well as minority-serving institutions, the number of Centers of Excellence grew to 34, and the number of Health Careers Opportunity Programs grew to 74. Then, in 2006, the federal government cut its funding abruptly and drastically, reducing the number of Centers of Excellence and Health Careers Opportunity Programs to 4 each. Several advocacy groups, supported by think tanks, have striven to restore federal funding to previous levels, so far to no avail. Meanwhile, the struggle to increase the representation of underrepresented minorities in the health professions is carried on by the surviving programs, including the remaining Centers of Excellence and Health Careers Opportunity Programs and new programs that, funded by state, local, and private agencies, have arisen from the ashes. Mt Sinai J Med 75:504,516, © 2008 Mount Sinai School of Medicine [source] Age- and gender-related changes in the temporal-spatial characteristics of forwards and backwards gaitsPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 3 2003Dr Yocheved Laufer Head Abstract Background and Purpose Backward walking is used increasingly as a rehabilitation technique for individuals with neurological and orthopaedic impairments. The purpose of the present study was to examine changes in the temporal-spatial characteristics of gait resulting from walking backwards as opposed to forwards, and to determine age and gender effects on these changes. Method Thirty young and 40 aged, independently functioning, subjects were asked to walk forwards and backwards across a computer-based walkway system, providing data on gait velocity, stride length, cadence, swing phase and double support phase. Subjects were divided into groups based on age (young and old) and gender, and each subject was tested under two walking conditions (forwards and backwards). Five temporal-spatial gait parameters were evaluated separately as a function of the three independent variables, with the walking condition repeated for each subject. Results Backwards ambulation is characterized by a slower velocity, shorter stride length and an increased double support phase in both young and older adults. These changes were significantly greater in the older subjects, among whom the swing phase was also decreased. Cadence, however, was not affected by direction of ambulation in either group. The female subjects had a shorter stride length in both movement directions, associated with reduced speed only in backwards ambulation. Conclusions Older individuals are capable of walking backwards for short distances. However, changes in gait characteristics typical to the reversal of movement direction are accentuated with age. These effects must be considered when planning to use backwards ambulation as a rehabilitation technique for older individuals. Copyright © 2003 Whurr Publishers Ltd. [source] | |||||||||||||