A translation-invariant based adaptive threshold denoising method formechanical impact signal is proposed. Compared with traditional wavelet denoising methods, itsuppresses pseudo-Gibbs phenomena in the neighborhood o...A translation-invariant based adaptive threshold denoising method formechanical impact signal is proposed. Compared with traditional wavelet denoising methods, itsuppresses pseudo-Gibbs phenomena in the neighborhood of signal discontinuities. To remedy thedrawbacks of conventional threshold functions, a new improved threshold function is introduced. Itpossesses more advantages than others. Moreover, based on utilizing characteristics of signal, aadaptive threshold selection procedure for impact signal is proposed. It is data-driven andlevel-dependent, therefore, it is more rational than other threshold estimation methods. Theproposed method is compared to alternative existing methods, and its superiority is revealed bysimulation and real data examples.展开更多
An effective and simple way to develop equations from impact strain signals was proposed.Little research has been performed in this area,but this equation is very important for evaluating input signals in finite eleme...An effective and simple way to develop equations from impact strain signals was proposed.Little research has been performed in this area,but this equation is very important for evaluating input signals in finite element analysis impact tests and for obtaining additional information on material deformation and fracture processes under impact loading.For this purpose,dynamic impact responses were examined through signals obtained from a strain gauge installed on an impact striker connected to a data acquisition system.Aluminium 6061-T6 was used to extract strain responses on the striker during Charpy impact testing.Statistical analysis was performed using the I-kaz method,and curve fitting equations based on the equation for vibration response under a non-periodic force were used to evaluate the Charpy impact signals.The I-kaz coefficients and curve fitting equations were then compared and discussed with related parameters,such as velocities and thicknesses.Velocity and thickness were found to be related to the strain signal patterns,curve fitting equations and I-kaz coefficients.The equations developed using this method had R2 values greater than 97.7%.Finally,the constructed equations were determined to be suitable for evaluating Charpy impact strain signal patterns and obtaining additional information on fracture processes under impact loading.展开更多
This paper examines safety impacts of a Pedestrian Countdown Signal (PCS) installed on a busy downtown intersection in San Diego, California. Crossing episodes of over 5000 pedestrians were videotaped and analyzed usi...This paper examines safety impacts of a Pedestrian Countdown Signal (PCS) installed on a busy downtown intersection in San Diego, California. Crossing episodes of over 5000 pedestrians were videotaped and analyzed using multivariate statistical methods. Details of timing of pedestrian crossing as well as information about vehicular traffic and signal timing were carefully coded for each pedestrian. Significant safety benefits of the PCS system were found on the long crossings over a street with high vehicular volumes: most pedestrians were able to effectively increase their walking speed to complete their crossing without committing the exit violation—even if they have already committed the entry violation. However, on the short crossing with light vehicular traffic, PCS was generally ineffective in preventing the entry violations from becoming exit violations. Over there, many pedestrians felt safe enough to walk over a short crossing with no apparent vehicular traffic in sight instead of waiting for a green signal. The length of crossing and volume of interfering vehicular traffic were consistently found the most significant variables affecting the crossing violation rates of different categories of pedestrians. Crossing violation rates were the highest for runners, bicyclists and older males. Crossing violation characteristics were found to be consistent over time.展开更多
甜味是食物摄入的重要驱动因素,是最受欢迎的味觉之一。目前,甜味信号的传导通路与影响甜味感觉的机制已有初步了解,人体甜味感觉至少由两类信号通路表达,一类由味觉受体第一家族成员2(taste receptor family 1 member 2,T1R2)和味觉受...甜味是食物摄入的重要驱动因素,是最受欢迎的味觉之一。目前,甜味信号的传导通路与影响甜味感觉的机制已有初步了解,人体甜味感觉至少由两类信号通路表达,一类由味觉受体第一家族成员2(taste receptor family 1 member 2,T1R2)和味觉受体第一家族成员3(taste receptor family 1 member 3,T1R3)形成的异源二聚体介导;另一类由钠-葡萄糖共转运蛋白与葡萄糖转运蛋白介导。本文综述了T1R2/T1R3异源二聚体结构以及甜味信号传导机制,探讨了苦味、酸味、鲜味、抗甜物质、香气化合物、唾液、肥胖、年龄等体内、外因素对甜味感知的影响;并指出了当前研究的不足之处:目前使用的无热量甜味剂(noncaloric sweeteners,NCSs)在减轻肥胖和糖尿病方面收效甚微,其他四味对甜味感觉的交叉互作研究较少,抗甜物质的调节机制在受体水平上的分子基础仍不清楚,甜味研究中使用啮齿动物代替人类具有一定的局限性。本文旨在理解甜味物质如何从复杂的基质中发挥作用,为今后NCSs食品的开发与应用提供理论支持与思路借鉴。展开更多
This study assesses the potential impacts of climate change on water resources and the effect of statistical bias correction on the projected climate change signal in hydrological variables over the Upper Senegal Basi...This study assesses the potential impacts of climate change on water resources and the effect of statistical bias correction on the projected climate change signal in hydrological variables over the Upper Senegal Basin (West Africa). Original and bias corrected climate data from the regional climate model REMO were used as input for the Max Planck Institute for Meteorology-Hydrology Model (MPI-HM) to simulate river discharge, runoff, soil moisture and evapotranspiration. The results during the historical period (1971-2000) show that using the bias corrected input yields a better representation of the mean river flow regimes and the 10th and 90th percentiles of river flow at the outlet of the Upper Senegal Basin (USB). The Nash-Sutcliffe efficiency coefficient is 0.92 using the bias corrected input, which demonstrates the ability of the model in simulating river flow. The percent bias of 3.88% indicates a slight overestimation of the river flow by the model using the corrected input. The evaluation demonstrates the ability of the bias correction and its necessity for the simulation of historical river regimes. As for the potential changes of hydrological variables by the end of 21st century (2071-2100), a general decrease of river discharge, runoff, actual evapotranspiration, soil moisture is found under two Representative Concentration Pathways (RCP4.5 and RCP8.5) in all simulations. The decrease is higher under RCP8.5 with uncorrected data in the northern basin. However, there are some localized increases in some parts of the basin (e.g. Guinean Highlands). The projected climate change signal of these above variables has the same spatial pattern and tendency for the uncorrected and bias corrected data although the magnitude of the corrected signal is somewhat lower than that uncorrected. Furthermore, the available water resources are projected to substantially decrease by more than -50% in the majority of the basin (especially in driest and hottest northern basin with RCP8.5 scenario) for all data, except the Guinean highlands where no change is projected. The comparison of simulations driven with uncorrected and bias corrected input reveals that the bias correction does not substantially change the signal of future changes of hydrological variables for both scenarios over the USB even though there are differences in magnitude and deviations in some parts of the basin.展开更多
A system for simulating and analyzing the Doppler signal of air-target fuse is established by constructing two parts： Doppler signal testing with simulation and Doppler signal analysis. The first part establishes the...A system for simulating and analyzing the Doppler signal of air-target fuse is established by constructing two parts： Doppler signal testing with simulation and Doppler signal analysis. The first part establishes the near-field target characteristic model where the Doppler spectrum in different encounter condition is obtained. The second part mainly deals with a general purpose hardware platform to obtain and process the Doppler signal as well as a software to estimate the Doppler spectrum. The model and the result of Doppler spectrum analysis were verified by experiments.展开更多
文摘A translation-invariant based adaptive threshold denoising method formechanical impact signal is proposed. Compared with traditional wavelet denoising methods, itsuppresses pseudo-Gibbs phenomena in the neighborhood of signal discontinuities. To remedy thedrawbacks of conventional threshold functions, a new improved threshold function is introduced. Itpossesses more advantages than others. Moreover, based on utilizing characteristics of signal, aadaptive threshold selection procedure for impact signal is proposed. It is data-driven andlevel-dependent, therefore, it is more rational than other threshold estimation methods. Theproposed method is compared to alternative existing methods, and its superiority is revealed bysimulation and real data examples.
基金Universiti Kebangsaan Malaysia grant UKM-KK-03-FRGS 0118-2010Universiti Teknikal Malaysia Melaka for supporting these research activities
文摘An effective and simple way to develop equations from impact strain signals was proposed.Little research has been performed in this area,but this equation is very important for evaluating input signals in finite element analysis impact tests and for obtaining additional information on material deformation and fracture processes under impact loading.For this purpose,dynamic impact responses were examined through signals obtained from a strain gauge installed on an impact striker connected to a data acquisition system.Aluminium 6061-T6 was used to extract strain responses on the striker during Charpy impact testing.Statistical analysis was performed using the I-kaz method,and curve fitting equations based on the equation for vibration response under a non-periodic force were used to evaluate the Charpy impact signals.The I-kaz coefficients and curve fitting equations were then compared and discussed with related parameters,such as velocities and thicknesses.Velocity and thickness were found to be related to the strain signal patterns,curve fitting equations and I-kaz coefficients.The equations developed using this method had R2 values greater than 97.7%.Finally,the constructed equations were determined to be suitable for evaluating Charpy impact strain signal patterns and obtaining additional information on fracture processes under impact loading.
文摘This paper examines safety impacts of a Pedestrian Countdown Signal (PCS) installed on a busy downtown intersection in San Diego, California. Crossing episodes of over 5000 pedestrians were videotaped and analyzed using multivariate statistical methods. Details of timing of pedestrian crossing as well as information about vehicular traffic and signal timing were carefully coded for each pedestrian. Significant safety benefits of the PCS system were found on the long crossings over a street with high vehicular volumes: most pedestrians were able to effectively increase their walking speed to complete their crossing without committing the exit violation—even if they have already committed the entry violation. However, on the short crossing with light vehicular traffic, PCS was generally ineffective in preventing the entry violations from becoming exit violations. Over there, many pedestrians felt safe enough to walk over a short crossing with no apparent vehicular traffic in sight instead of waiting for a green signal. The length of crossing and volume of interfering vehicular traffic were consistently found the most significant variables affecting the crossing violation rates of different categories of pedestrians. Crossing violation rates were the highest for runners, bicyclists and older males. Crossing violation characteristics were found to be consistent over time.
文摘甜味是食物摄入的重要驱动因素,是最受欢迎的味觉之一。目前,甜味信号的传导通路与影响甜味感觉的机制已有初步了解,人体甜味感觉至少由两类信号通路表达,一类由味觉受体第一家族成员2(taste receptor family 1 member 2,T1R2)和味觉受体第一家族成员3(taste receptor family 1 member 3,T1R3)形成的异源二聚体介导;另一类由钠-葡萄糖共转运蛋白与葡萄糖转运蛋白介导。本文综述了T1R2/T1R3异源二聚体结构以及甜味信号传导机制,探讨了苦味、酸味、鲜味、抗甜物质、香气化合物、唾液、肥胖、年龄等体内、外因素对甜味感知的影响;并指出了当前研究的不足之处:目前使用的无热量甜味剂(noncaloric sweeteners,NCSs)在减轻肥胖和糖尿病方面收效甚微,其他四味对甜味感觉的交叉互作研究较少,抗甜物质的调节机制在受体水平上的分子基础仍不清楚,甜味研究中使用啮齿动物代替人类具有一定的局限性。本文旨在理解甜味物质如何从复杂的基质中发挥作用,为今后NCSs食品的开发与应用提供理论支持与思路借鉴。
文摘This study assesses the potential impacts of climate change on water resources and the effect of statistical bias correction on the projected climate change signal in hydrological variables over the Upper Senegal Basin (West Africa). Original and bias corrected climate data from the regional climate model REMO were used as input for the Max Planck Institute for Meteorology-Hydrology Model (MPI-HM) to simulate river discharge, runoff, soil moisture and evapotranspiration. The results during the historical period (1971-2000) show that using the bias corrected input yields a better representation of the mean river flow regimes and the 10th and 90th percentiles of river flow at the outlet of the Upper Senegal Basin (USB). The Nash-Sutcliffe efficiency coefficient is 0.92 using the bias corrected input, which demonstrates the ability of the model in simulating river flow. The percent bias of 3.88% indicates a slight overestimation of the river flow by the model using the corrected input. The evaluation demonstrates the ability of the bias correction and its necessity for the simulation of historical river regimes. As for the potential changes of hydrological variables by the end of 21st century (2071-2100), a general decrease of river discharge, runoff, actual evapotranspiration, soil moisture is found under two Representative Concentration Pathways (RCP4.5 and RCP8.5) in all simulations. The decrease is higher under RCP8.5 with uncorrected data in the northern basin. However, there are some localized increases in some parts of the basin (e.g. Guinean Highlands). The projected climate change signal of these above variables has the same spatial pattern and tendency for the uncorrected and bias corrected data although the magnitude of the corrected signal is somewhat lower than that uncorrected. Furthermore, the available water resources are projected to substantially decrease by more than -50% in the majority of the basin (especially in driest and hottest northern basin with RCP8.5 scenario) for all data, except the Guinean highlands where no change is projected. The comparison of simulations driven with uncorrected and bias corrected input reveals that the bias correction does not substantially change the signal of future changes of hydrological variables for both scenarios over the USB even though there are differences in magnitude and deviations in some parts of the basin.
文摘A system for simulating and analyzing the Doppler signal of air-target fuse is established by constructing two parts： Doppler signal testing with simulation and Doppler signal analysis. The first part establishes the near-field target characteristic model where the Doppler spectrum in different encounter condition is obtained. The second part mainly deals with a general purpose hardware platform to obtain and process the Doppler signal as well as a software to estimate the Doppler spectrum. The model and the result of Doppler spectrum analysis were verified by experiments.
