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Peak Periods (peak + period)
Selected AbstractsTemporal and spatial rainfall analysis across a humid tropical catchmentHYDROLOGICAL PROCESSES, Issue 3 2001P. Campling Abstract Temporal and spatial rainfall patterns were analysed to describe the distribution of daily rainfall across a medium-sized (379km2) tropical catchment. Investigations were carried out to assess whether a climatological variogram model was appropriate for mapping rainfall taking into consideration the changing rainfall characteristics through the wet season. Exploratory, frequency and moving average analyses of 30 years' daily precipitation data were used to describe the reliability and structure of the rainfall regime. Four phases in the wet season were distinguished, with the peak period (mid-August to mid-September) representing the wettest period. A low-cost rain gauge network of 36 plastic gauges with overflow reservoirs was installed and monitored to obtain spatially distributed rainfall data. Geostatistical techniques were used to develop global and wet season phase climatological variograms. The unscaled climatological variograms were cross-validated and compared using a range of rainfall events. Ordinary Kriging was used as the interpolation method. The global climatological variogram performed better, and was used to optimize the number and location of rain gauges in the network. The research showed that although distinct wet season phases could be established based on the temporal analysis of daily rainfall characteristics, the interpolation of daily rainfall across a medium-sized catchment based on spatial analysis was better served by using the global rather than the wet season phase climatological variogram model. Copyright © 2001 John Wiley & Sons, Ltd. [source] Information technology and its impact on stock returns and trading volumeINTERNATIONAL JOURNAL OF FINANCE & ECONOMICS, Issue 3 2010Uri Benzion Abstract This study investigates the impact of information technology on common stock returns and trading volume. By focusing mainly on the peak period of the hi-tech phenomenon, the findings imply that the market response to website launching is positive. During the event day and the two preceding days, the abnormal stock return and the abnormal trading volume both are positive and statistically significant. In particular, the impact is stronger for non-US firms than for domestic companies, for initial rather than subsequent site launches, for those sites that are launched on Monday rather than on other days of the week, and for innovative industries such as electronics and computers. As expected, while the launch of a website had a stronger effect at the beginning of the hi-tech phenomenon, the impact has diminished in later years. Copyright © 2009 John Wiley & Sons, Ltd. [source] Impact of interviewing by proxy in travel survey conducted by telephoneJOURNAL OF ADVANCED TRANSPORTATION, Issue 1 2002Daniel A. Badoe Telephone-interview surveys are a very efficient way of conducting large-scale travel surveys. Recent advancements in computer technology have made it possible to improve upon the quality of data collected by telephone surveys through computerization of the entire sample-control process, and through the direct recording of the collected data into a computer. Notwithstanding these technological advancements, potential sources of bias still exist, including the reliance on an adult member of the household to report the travel information of other household members. Travel data collected in a recent telephone interview survey in the Toronto region is used to examine this issue. The statistical tool used in the research was the Analysis of Variance (ANOVA) technique as implemented within the general linear model framework in SAS. The study-results indicate that reliance on informants to provide travel information for non-informant members of their respective households led to the underreporting of some categories of trips. These underreported trip categories were primarily segments of home-based discretionary trips, and non home-based trips. Since these latter two categories of trips are made primarily outside the morning peak period, estimated factors to adjust for their underreporting were time-period sensitive. Further, the number of vehicles available to the household, gender, and driver license status respectively were also found to be strongly associated with the underreporting of trips and thus were important considerations in the determination of adjustment factors. Work and school trips were found not to be underreported, a not surprising result giving the almost daily repetitiveness of trips made for these purposes and hence the ability of the informant to provide relatively more precise information on them. [source] Estimating time dependent O-D trip tables during peak periodsJOURNAL OF ADVANCED TRANSPORTATION, Issue 3 2000Srinivas S. Pulugurtha Intelligent transportation systems (ITS) have been used to alleviate congestion problems arising due to demand during peak periods. The success of ITS strategies relies heavily on two factors: 1) the ability to accurately estimate the temporal and spatial distribution of travel demand on the transportation network during peak periods, and, 2) providing real-time route guidance to users. This paper addresses the first factor. A model to estimate time dependent origin-destination (O-D) trip tables in urban areas during peak periods is proposed. The daily peak travel period is divided into several time slices to facilitate simulation and modeling. In urban areas, a majority of the trips during peak periods are work trips. For illustration purposes, only peak period work trips are considered in this paper. The proposed methodology is based on the arrival pattern of trips at a traffic analysis zone (TAZ) and the distribution of their travel times. The travel time matrix for the peak period, the O-D trip table for the peak period, and the number of trips expected to arrive at each TAZ at different work start times are inputs to the model. The model outputs are O-D trip tables for each time slice in the peak period. 1995 data for the Las Vegas metropolitan area are considered for testing and validating the model, and its application. The model is reasonably robust, but some lack of precision was observed. This is due to two possible reasons: 1) rounding-off, and, 2) low ratio of total number of trips to total number of O-D pair combinations. Hence, an attempt is made to study the effect of increasing this ratio on error estimates. The ratio is increased by multiplying each O-D pair trip element with a scaling factor. Better estimates were obtained. Computational issues involved with the simulation and modeling process are discussed. [source] Ethanol-Related Behaviors in Serotonin Transporter Knockout MiceALCOHOLISM, Issue 12 2006Janel M. Boyce-Rustay Background: Increasing evidence supports a role for 5-hydroxytryptamine (5-HT) and the 5-HT transporter (5-HTT) in modulating the neural and behavioral actions of ethanol (EtOH) and other drugs of abuse. Methods: We used a 5-HTT knockout (KO) mouse model to further study this relationship. 5-Hydroxytryptamine transporter KO mice were tested for the sedative/hypnotic, hypothermia-inducing, motor-incoordinating (via accelerating rotarod), and depression-related (via tail suspension test) effects of acute EtOH administration. Reward-related effects of EtOH were assessed in 5-HTT KO mice using the conditioned place preference (CPP) paradigm. 5-Hydroxytryptamine transporter KO mice were tested for voluntary consumption of EtOH in a modified 2-bottle choice test that measured the temporal organization of drinking over the circadian cycle via "lickometers." Results: Replicating previous findings, 5-HTT KO mice exhibited significantly increased sensitivity to EtOH-induced sedation/hypnosis relative to wild-type controls. Additionally, 5-HTT KO mice showed motor-coordination deficits at baseline and in response to EtOH. Hypothermic, pro-depressive,like, and reward-related effects of EtOH were no different across genotypes. Gross EtOH consumption was modestly reduced in 5-HTT KO mice, due to significantly lesser consumption during the peak period of drinking in the early dark phase. Conclusions: Data extend the finding that loss of 5-HTT gene function alters certain neural and behavioral effects of EtOH, with implications for better understanding the pathophysiology and treatment of alcoholism. [source] Constructing a 7-day ahead forecast model for grass pollen at north London, United KingdomCLINICAL & EXPERIMENTAL ALLERGY, Issue 10 2005M. Smith Summary Background A number of media outlets now issue medium-range (,7 day) weather forecasts on a regular basis. It is therefore logical that aerobiologists should attempt to produce medium-range forecasts for allergenic pollen that cover the same time period as the weather forecasts.Objective the objective of this study is to construct a medium-range (7 day) forecast model for grass pollen at north London.Method the forecast models were produced using regression analysis based on grass pollen and meteorological data from 1990 to 1999 and tested on data from 2000 and 2002. The modelling process was improved by dividing the grass pollen season into three periods; the pre-peak, peak and post-peak periods of grass pollen release. The forecast consisted of five regression models: two simple linear regression models predicting the start and end date of the peak period, and three multiple regression models forecasting daily average grass pollen counts in the pre-peak, peak and post-peak periods.Results overall, the forecast models achieved 62% accuracy in 2000 and 47% in 2002, reflecting the fact that the 2002 grass pollen season was of a higher magnitude than any of the other seasons included in the analysis.Conclusion this study has the potential to make a notable contribution to the field of aerobiology. Winter averages of the North Atlantic Oscillation were used to predict certain characteristics of the grass pollen season, which presents an important advance in aerobiological work. The ability to predict allergenic pollen counts for a period between five and seven days will benefit allergy sufferers. Furthermore, medium-range forecasts for allergenic pollen will be of assistance to the medical profession, including allergists planning treatment and physicians scheduling clinical trials. [source] Near-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] Greenhouse gas reduction potential of advanced traffic controlJOURNAL OF ADVANCED TRANSPORTATION, Issue 3 2000Abdulkader Alkadry Reducing greenhouse gas (GHG) emissions from transportation in the context of the climate change issue and the associated Kyoto Agreement of 1997 is a challenge. Since urban transportation is a major contributor to greenhouse gases, measures are required to reduce these emissions. Given that during peak periods, road vehicles propelled by petroleum fuel-based internal combustion engines produce a high level of GHG emissions due to stop and go operations, measures to improve traffic flow can play an effective mitigation role. This paper describes a simulation-based methodology and a case study for the quantification of GHG emission reduction owing to advanced traffic control systems. [source] Estimating time dependent O-D trip tables during peak periodsJOURNAL OF ADVANCED TRANSPORTATION, Issue 3 2000Srinivas S. Pulugurtha Intelligent transportation systems (ITS) have been used to alleviate congestion problems arising due to demand during peak periods. The success of ITS strategies relies heavily on two factors: 1) the ability to accurately estimate the temporal and spatial distribution of travel demand on the transportation network during peak periods, and, 2) providing real-time route guidance to users. This paper addresses the first factor. A model to estimate time dependent origin-destination (O-D) trip tables in urban areas during peak periods is proposed. The daily peak travel period is divided into several time slices to facilitate simulation and modeling. In urban areas, a majority of the trips during peak periods are work trips. For illustration purposes, only peak period work trips are considered in this paper. The proposed methodology is based on the arrival pattern of trips at a traffic analysis zone (TAZ) and the distribution of their travel times. The travel time matrix for the peak period, the O-D trip table for the peak period, and the number of trips expected to arrive at each TAZ at different work start times are inputs to the model. The model outputs are O-D trip tables for each time slice in the peak period. 1995 data for the Las Vegas metropolitan area are considered for testing and validating the model, and its application. The model is reasonably robust, but some lack of precision was observed. This is due to two possible reasons: 1) rounding-off, and, 2) low ratio of total number of trips to total number of O-D pair combinations. Hence, an attempt is made to study the effect of increasing this ratio on error estimates. The ratio is increased by multiplying each O-D pair trip element with a scaling factor. Better estimates were obtained. Computational issues involved with the simulation and modeling process are discussed. [source] Seasonality and host utilization of the invasive fruit fly, Bactrocera invadens (Dipt., Tephritidae) in central TanzaniaJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2006M. W. Mwatawala Abstract:, The temporal occurrence of the invasive and economically important pest fruit fly, Bactrocera invadens was studied in three agro-ecological areas of Morogoro Region, central Tanzania, during 2004,2005. Weekly and monthly trappings were carried out with methyl eugenol, protein bait and synthetic food attractant. Bactrocera invadens was permanently present at low and mid-altitudes (380,520 m a.s.l.) with peak periods coinciding with the fruiting season of mango (Mangifera indica) and guava (Psidium guajava). At high altitude (1650 m a.s.l.) its incidence was only temporal and apparently the result of dispersal from lower altitudes after the mango fruiting season. Rearing results showed mango, loquat (Eriobotrya japonica), guava and grapefruit (Citrus × paradisi) to be the favoured commercial host fruits. Other Citrus species, cucurbits, papaya (Carica papaya) and avocado (Persea americana) were less favoured. [source] QUANTIFYING MARKET POWER IN THE GERMAN WHOLESALE ELECTRICITY MARKET USING A DYNAMIC MULTI-REGIONAL DISPATCH MODEL,THE JOURNAL OF INDUSTRIAL ECONOMICS, Issue 4 2006FELIX MÜSGENS This paper quantifies the degree of market power in the German wholesale electricity market. A dispatch model simulates competitive marginal costs. In addition to common input factors like plant capacities, fuel prices and load structures, the model also incorporates international power exchange and dynamic effects like start-up costs and hydro storage plant dispatch. The simulated prices are subsequently used as a benchmark for observed electricity prices. The analysis reveals significant market power in the German electricity market, mainly exhibited during peak periods. Producer surplus is also increased significantly due to strategic behavior. [source] Conservation breeding for reintroductions: assessing survival in a captive flock of houbara bustardsANIMAL CONSERVATION, Issue 3 2001Yolanda van Heezik Conservation breeding for reintroduction is becoming a popular option for restoring threatened populations. Whereas post-release results are widely reported in the conservation literature, little empirical information is presented on the captive populations that often make such releases possible, even though fecundity, fertility and survival rates can have an impact on the outcome and cost of wild population re-establishment. We present results of survival analyses carried out on a captive population of houbara bustards to determine peak periods of mortality, and by identifying sources of variations in mortality to recognize the potential impact of management practices on productivity. There were two main mortality peaks: during incubation (53% survival of fertile eggs), and by 6 months post-hatching (75% survival of hatchlings). Management-related variables influencing survival of eggs and chicks included the year when laid, the cohort of females laying them, and possibly sex. Most post-hatching deaths were due to trauma and infectious diseases. Trauma-related deaths usually follow collisions with cages, and imply selection for the captive environment, an undesirable trend in populations maintained for reintroductions. Reducing losses during incubation would have the largest impact on production of birds for reintroduction, enabling the release of more birds, and reducing the overall costs of the project. 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