为获取运行中的特高压交流输电线路无线电干扰水平及其特性,在特高压交流试验示范工程沿线的湖北枣阳建立了一处电磁环境长期观测站,对历时1 a得到的14.4万组有效数据进行了统计分析,获取了我国特高压交流输电线路无线电干扰的主要特性...为获取运行中的特高压交流输电线路无线电干扰水平及其特性,在特高压交流试验示范工程沿线的湖北枣阳建立了一处电磁环境长期观测站,对历时1 a得到的14.4万组有效数据进行了统计分析,获取了我国特高压交流输电线路无线电干扰的主要特性。研究表明:1 000 kV特高压交流输电线路无线电干扰好天气和雨天的长期测试数据基本符合正态分布,频谱特性和横向分布规律与CISPR研究结果基本一致,得到了无线电干扰不同天气条件下的统计值和累积概率曲线。0.5 MHz无线电干扰全天候80%、95%值分别为55.06、65.37 d B,好天气平均值为48.22 d B。采用CISPR激发函数法计算我国特高压交流单回路无线电干扰时,大雨到好天气下平均值的差值可取中值20.5 d B。展开更多
为获取实际运行的特高压交流同塔双回输电线路可听噪声水平及其特性,并对BPA公式修正方法进行评估,通过在1 000 kV淮南—上海特高压同塔双回输电线路沿线的安徽芜湖建立一处电磁环境长期观测站,对可听噪声开展了10个月的长期测试,获取...为获取实际运行的特高压交流同塔双回输电线路可听噪声水平及其特性,并对BPA公式修正方法进行评估,通过在1 000 kV淮南—上海特高压同塔双回输电线路沿线的安徽芜湖建立一处电磁环境长期观测站,对可听噪声开展了10个月的长期测试,获取了不同天气下的可听噪声典型频谱,并对雨天可听噪声测试数据进行了统计分析。研究表明:芜湖观测站3个测点测得的雨天可听噪声基本符合正态分布,边相导线投影外20 m可听噪声A声级与其8 k Hz分量的相关性较好。边相导线投影外10、20 m处的雨天可听噪声实测L50值分别为49.83、49.58 d B,与BPA公式计算值减2 d B修正后的预测结果较相符。展开更多
Over the last 33 years,a network of climate stations has been set up at high altitude mountain permafrost sites from Plateau Mountain near Claresholm,Alberta,north to Sheldon Lake on the North Canol Road in the Yukon....Over the last 33 years,a network of climate stations has been set up at high altitude mountain permafrost sites from Plateau Mountain near Claresholm,Alberta,north to Sheldon Lake on the North Canol Road in the Yukon.Taken together with the data from the US National Weather Service and the Canadian Atmospheric Environment Service,the results indicate a cooling of mean annual air temperature south of Calgary,no significant change in Calgary,a slight warming at Jasper,and a major warming at Summit Lake,west of Fort Nelson.In contrast,the south eastern and central Yukon show only a minor warming trend that lies well within the limits of a sixty-year record measured by the Canadian Atmospheric Environment Service.Along the Mackenzie valley and on the North Slope of Alaska,the mean annual air temperature is rising.Permafrost is aggrading on Plateau Mountain,degrading at Summit Lake,and appears to be stable in southern Yukon and southern Alaska.This is in contrast to the warming occurring on the Arctic coastal plain and along the Mackenzie valley.It therefore appears that changes in climate vary considera-bly from place to place,and even where warming may occur,it may not continue indefinitely.There has been a northward shift of the arctic front due to a weakening of air pressure in the Yukon and Alaska relative to the continental tropical(cT) and maritime polar(mT) air masses to the south.Any actual changes that may be occurring appear to undergo amplification along the Mackenzie valley and Arctic coastal plain and reduction by buffering in the interior Yukon and Alaskan mountains,a result of mi-cro-environmental factors.Continued,careful monitoring of the climate is required and needs to be expanded in the National Parks in the mountains in order to provide data on the changes that may be taking place.Such measurements can provide a sound basis for interpreting ecological and other climate-related data.The existing climate models are not working satisfactorily because we do not know enough about the causes and proces展开更多
This work studies a proportional hazards model for survival data with ＂long-term survivors＂, in which covariates are subject to linear measurement error. It is well known that the naive estimators from both partial ...This work studies a proportional hazards model for survival data with ＂long-term survivors＂, in which covariates are subject to linear measurement error. It is well known that the naive estimators from both partial and full likelihood methods are inconsistent under this measurement error model. For measurement error models, methods of unbiased estimating function and corrected likelihood have been proposed in the literature. In this paper, we apply the corrected partial and full likelihood approaches to estimate the model and obtain statistical inference from survival data with long-term survivors. The asymptotic properties of the estimators are established. Simulation results illustrate that the proposed approaches provide useful tools for the models considered.展开更多
The multi-point simultaneous long-term measurement of CO_(2) concentration in seawater can provide more-valuable data for further understanding of the spatial and temporal distribution of CO_(2).Thus,the requirement f...The multi-point simultaneous long-term measurement of CO_(2) concentration in seawater can provide more-valuable data for further understanding of the spatial and temporal distribution of CO_(2).Thus,the requirement for a low-cost sensor with high precision,low power consumption,and a small size is becoming urgent.In this work,an in-situ sensor for CO_(2) detection in seawater,based on a permeable membrane and non-dispersive infrared(NDIR)technology,is developed.The sensor has a small size(Ф66 mm×124 mm),light weight(0.7 kg in air),low power consumption(<0.9 W),low cost(<US$1000),and high-pressure tolerance(<200 m).After laboratory performance tests,the sensor was found to have a measurement range of(0–2000)×10^(-6),and the gas linear correlation R^(2) is 0.99,with a precision of about 0.98%at a sampling rate of 1 s.A comparison measurement was carried out with a commercial sensor in a pool for 7 days,and the results showed a consistent trend.Further,the newly developed sensor was deployed in Qingdao nearshore water for 35 days.The results proved that the sensor could measure the dynamic changes of CO_(2) concentration in seawater continuously,and had the potential to carry out long-term observations on an oceanic platform.It is hoped that the sensor could be applied to field ocean observations in near future.展开更多
Drift phenomenon has been known as the drawback of sensors and causes inaccuracy on the long-term measurement. In general,there are two methods to reduce the drift problem.One is to tune the parameters of the fabricat...Drift phenomenon has been known as the drawback of sensors and causes inaccuracy on the long-term measurement. In general,there are two methods to reduce the drift problem.One is to tune the parameters of the fabrication process to improve the properties of the front-ended device.Another is to compensate the drift phenomenon by adding extra drift compensation circuit or software in the back-ended readout circuit.In this study,a drift calibration method for the potentiometric sensor was presented and the drift calibration method was performed by using the circuit.According to experimental results,the drift phenomenon of the SnO_2 pH electrode was reduced by the drift calibration device.展开更多
文摘为获取运行中的特高压交流输电线路无线电干扰水平及其特性,在特高压交流试验示范工程沿线的湖北枣阳建立了一处电磁环境长期观测站,对历时1 a得到的14.4万组有效数据进行了统计分析,获取了我国特高压交流输电线路无线电干扰的主要特性。研究表明:1 000 kV特高压交流输电线路无线电干扰好天气和雨天的长期测试数据基本符合正态分布,频谱特性和横向分布规律与CISPR研究结果基本一致,得到了无线电干扰不同天气条件下的统计值和累积概率曲线。0.5 MHz无线电干扰全天候80%、95%值分别为55.06、65.37 d B,好天气平均值为48.22 d B。采用CISPR激发函数法计算我国特高压交流单回路无线电干扰时,大雨到好天气下平均值的差值可取中值20.5 d B。
文摘为获取实际运行的特高压交流同塔双回输电线路可听噪声水平及其特性,并对BPA公式修正方法进行评估,通过在1 000 kV淮南—上海特高压同塔双回输电线路沿线的安徽芜湖建立一处电磁环境长期观测站,对可听噪声开展了10个月的长期测试,获取了不同天气下的可听噪声典型频谱,并对雨天可听噪声测试数据进行了统计分析。研究表明:芜湖观测站3个测点测得的雨天可听噪声基本符合正态分布,边相导线投影外20 m可听噪声A声级与其8 k Hz分量的相关性较好。边相导线投影外10、20 m处的雨天可听噪声实测L50值分别为49.83、49.58 d B,与BPA公式计算值减2 d B修正后的预测结果较相符。
基金Roger J. E. Brown of the Building Research Division, National Research Council of Canada funded the original studyby the Geological Survey of Canada (Alan Heginbottom and Sharon Smith)NSERC Operating Grant A-7483
文摘Over the last 33 years,a network of climate stations has been set up at high altitude mountain permafrost sites from Plateau Mountain near Claresholm,Alberta,north to Sheldon Lake on the North Canol Road in the Yukon.Taken together with the data from the US National Weather Service and the Canadian Atmospheric Environment Service,the results indicate a cooling of mean annual air temperature south of Calgary,no significant change in Calgary,a slight warming at Jasper,and a major warming at Summit Lake,west of Fort Nelson.In contrast,the south eastern and central Yukon show only a minor warming trend that lies well within the limits of a sixty-year record measured by the Canadian Atmospheric Environment Service.Along the Mackenzie valley and on the North Slope of Alaska,the mean annual air temperature is rising.Permafrost is aggrading on Plateau Mountain,degrading at Summit Lake,and appears to be stable in southern Yukon and southern Alaska.This is in contrast to the warming occurring on the Arctic coastal plain and along the Mackenzie valley.It therefore appears that changes in climate vary considera-bly from place to place,and even where warming may occur,it may not continue indefinitely.There has been a northward shift of the arctic front due to a weakening of air pressure in the Yukon and Alaska relative to the continental tropical(cT) and maritime polar(mT) air masses to the south.Any actual changes that may be occurring appear to undergo amplification along the Mackenzie valley and Arctic coastal plain and reduction by buffering in the interior Yukon and Alaskan mountains,a result of mi-cro-environmental factors.Continued,careful monitoring of the climate is required and needs to be expanded in the National Parks in the mountains in order to provide data on the changes that may be taking place.Such measurements can provide a sound basis for interpreting ecological and other climate-related data.The existing climate models are not working satisfactorily because we do not know enough about the causes and proces
基金supported by the National Nature Science Foundation of China under Grant No.10871084Macquarie University Safety Net grant
文摘This work studies a proportional hazards model for survival data with ＂long-term survivors＂, in which covariates are subject to linear measurement error. It is well known that the naive estimators from both partial and full likelihood methods are inconsistent under this measurement error model. For measurement error models, methods of unbiased estimating function and corrected likelihood have been proposed in the literature. In this paper, we apply the corrected partial and full likelihood approaches to estimate the model and obtain statistical inference from survival data with long-term survivors. The asymptotic properties of the estimators are established. Simulation results illustrate that the proposed approaches provide useful tools for the models considered.
基金Supported by the National Nature Science Foundation of China(No.41527901)the Provincial Key Research and Development Program of Shandong,China(No.2019JZZY010417)the Special Program of Shandong Province for Qingdao Pilot National Laboratory of Marine Science and Technology(No.2021QNLM020002).
文摘The multi-point simultaneous long-term measurement of CO_(2) concentration in seawater can provide more-valuable data for further understanding of the spatial and temporal distribution of CO_(2).Thus,the requirement for a low-cost sensor with high precision,low power consumption,and a small size is becoming urgent.In this work,an in-situ sensor for CO_(2) detection in seawater,based on a permeable membrane and non-dispersive infrared(NDIR)technology,is developed.The sensor has a small size(Ф66 mm×124 mm),light weight(0.7 kg in air),low power consumption(<0.9 W),low cost(<US$1000),and high-pressure tolerance(<200 m).After laboratory performance tests,the sensor was found to have a measurement range of(0–2000)×10^(-6),and the gas linear correlation R^(2) is 0.99,with a precision of about 0.98%at a sampling rate of 1 s.A comparison measurement was carried out with a commercial sensor in a pool for 7 days,and the results showed a consistent trend.Further,the newly developed sensor was deployed in Qingdao nearshore water for 35 days.The results proved that the sensor could measure the dynamic changes of CO_(2) concentration in seawater continuously,and had the potential to carry out long-term observations on an oceanic platform.It is hoped that the sensor could be applied to field ocean observations in near future.
文摘Drift phenomenon has been known as the drawback of sensors and causes inaccuracy on the long-term measurement. In general,there are two methods to reduce the drift problem.One is to tune the parameters of the fabrication process to improve the properties of the front-ended device.Another is to compensate the drift phenomenon by adding extra drift compensation circuit or software in the back-ended readout circuit.In this study,a drift calibration method for the potentiometric sensor was presented and the drift calibration method was performed by using the circuit.According to experimental results,the drift phenomenon of the SnO_2 pH electrode was reduced by the drift calibration device.
