In this paper, the AMSAA-BISE model with missing data is discussed. The ML estimates of model parameters and current MTBF are given, and the chi-squared test and a plot for cumulative number of failures versus cumulat...In this paper, the AMSAA-BISE model with missing data is discussed. The ML estimates of model parameters and current MTBF are given, and the chi-squared test and a plot for cumulative number of failures versus cumulative testing time are used to test the goodness of fit for the model. This paper concludes with a numerical example to verify the model.展开更多
La（O,F）BiSe2 is a layered superconductor and has the same crystal structure with La（O,F）BiS2. We investigate the electronic structure of La（O,F）BiSe2 using the angle-resolved photoemission spectroscopy. Two elec...La（O,F）BiSe2 is a layered superconductor and has the same crystal structure with La（O,F）BiS2. We investigate the electronic structure of La（O,F）BiSe2 using the angle-resolved photoemission spectroscopy. Two electron-like Fermi surfaces around X（π, 0） are observed, corresponding to the electron doping of 0.23 per Bi site. We clearly resolve anisotropic band splitting along both Г-X and M-X due to the cooperative effects of large spin-orbit coupling and interlayer coupling. Moreover, we observe an almost non-dispersive electronic state around -0.2 eV between the electron-like bands. This state vanishes after in-situ K evaporation, indicating that it could be the localized surface state caused by defects on the cleaved surface.展开更多
BiSe with intrinsic low thermal conductivity has considered as a promising thermoelectric(TE)material at nearly room temperature.To improve its low thermoelectric figure of merit(zT),in this work,Sb and Te isovalent c...BiSe with intrinsic low thermal conductivity has considered as a promising thermoelectric(TE)material at nearly room temperature.To improve its low thermoelectric figure of merit(zT),in this work,Sb and Te isovalent co-alloying was performed and significantly optimized its TE property with weakly anisotropic characteristic.After substituting Sb on Bi sites,the carrier concentration is suppressed by introduction of Sbsingle bond Se site defects,which contributes to the increased absolute value of Seebeck coefficient(|S|).Further co-alloying Te on Se of the optimized composition Bi_(0.7)Sb_(0.3)Se,the carrier concentration increased without affecting the|S|due to the enhanced effective mass,which leads to a highest power factor of 12.8μW/(cm·K^(2))at 423 K.As a result,a maximum zT of∼0.54 is achieved for Bi_(0.7)Sb_(0.3)Se_(0.7)Te_(0.3) along the pressing direction and the average zT(zTave)(from 300 K to 623 K)are drastically improved from 0.24 for pristine BiSe sample to 0.45.Moreover,an energy conversion efficiency∼4.0%is achieved for a single leg TE device of Bi_(0.7)Sb_(0.3)Se_(0.7)Te_(0.3)when applied the temperature difference of 339 K,indicating the potential TE application.展开更多
An advanced reliability growth model, i. e. exponential model, was presented to estimate the model parameters for multi-systems, which was synchronously tested, synchronously censored, and synchronously improved. In t...An advanced reliability growth model, i. e. exponential model, was presented to estimate the model parameters for multi-systems, which was synchronously tested, synchronously censored, and synchronously improved. In the presented method, the data during the reliability growth process were taken into consideration sufficiently, including the failure numbers, safety numbers and failure time at each censored time. If the multi-systems were synchronously improved for many times, and the reliability growth of each system fitted AMSAA （Army Material Systems Analysis Activity） model, the failure time of each system could be considered rationally as an exponential distribution between two adjoining censored times. The nonparametric method was employed to obtain the reliability at each censored time of the synchronous multisystems. The point estimations of the model parameters, a and b, were given by the least square method. The confidence interval for the parameter b was given as well. An engineering illustration was used to compare the result of the presented method with those of the available models. The result shows that the presented exponential growth model fits AMSAA-BISE （ Army Material Systems Analysis Activity-Beijing Institute of Structure and Environment） model rather well, and two models are suitable to estimate the reliability growth for the synchronously developed multi-systems.展开更多
近年来,大批量煤矿开采已经严重破坏到矿区周围的生态环境,而新时代我国注重绿色发展,这就需要对矿区生态条件进行修复。修复生态可从分析研究该区域的植被覆盖度开始。NDVI时间序列数据是目前最常用的数据源之一,其在全球气候环境变化...近年来,大批量煤矿开采已经严重破坏到矿区周围的生态环境,而新时代我国注重绿色发展,这就需要对矿区生态条件进行修复。修复生态可从分析研究该区域的植被覆盖度开始。NDVI时间序列数据是目前最常用的数据源之一,其在全球气候环境变化、植被覆盖动态变化检测、植被信息提取等方面具有广泛应用。但由于传感器、云层覆盖等因素影响,NDVI时序数据比一般数据更容易出现噪声,因此时序数据去噪显得至关重要。文章以宝日希勒矿区为研究区,从目视判别时序曲线、对比去噪样本点的去噪均方根误差、以及变化检测结果精度分析三个角度,在matlab编程软件以及ENVI软件的帮助下,实现这三种去噪算法,并对比分析这3种方法的优点和缺点。研究结果表明:1) 3种去噪算法都有效地对原始NDVI时序数据进行了去噪,且效果明显;2) 不同的去噪方法均存在着过度拟合的现象;3) 对于文章所选的NDVI最大合成数据而言,B-W去噪效果最好,其次是去噪效果一般的BISE算法,S-G算法的去噪效果最差。In recent years, large-scale coal mining has seriously damaged the ecological environment around the mining area. In the new era, China pays attention to green development, which requires the restoration of the ecological conditions of the mining area. Ecological restoration can start from analyzing the vegetation coverage of the area. NDVI time series data is one of the most commonly used data sources at present. It has been widely used in global climate and environmental change, dynamic change detection of vegetation cover, vegetation information extraction and so on. However, due to the influence of sensors, cloud cover and other factors, NDVI time series data are prone to noise, so data denoising is very important. Taking Baorixile mining area as the research area, this paper realizes these three denoising algorithms under Matlab programming software from three angles: visual discrimination of time series curve, comparison of denoising root mean square error of denoising sample points, and accuracy analysis of change detection results, and compares and analyzes the advantages and disadvantages of these three methods. The results show that: 1) The three smoothing algorithms all effectively denoise the original NDVI time series data, and the effect is obvious;2) Ecological restoration can start from analyzing the vegetation coverage of the area;3) For the NDVI maximum synthetic data selected in this paper, B-W has the best denoising effect, followed by bise algorithm, and finally S-G algorithm has the worst denoising effect.展开更多
文摘In this paper, the AMSAA-BISE model with missing data is discussed. The ML estimates of model parameters and current MTBF are given, and the chi-squared test and a plot for cumulative number of failures versus cumulative testing time are used to test the goodness of fit for the model. This paper concludes with a numerical example to verify the model.
基金Supported by the National Basic Research Program of China under Grant Nos 2015CB921300,2013CB921700 and 2016YFA0300404the National Natural Science Foundation of China under Grant Nos 11474340,11234014,U1532267 and 11674327the Chinese Academy of Sciences under Grant No XDB07000000
文摘La（O,F）BiSe2 is a layered superconductor and has the same crystal structure with La（O,F）BiS2. We investigate the electronic structure of La（O,F）BiSe2 using the angle-resolved photoemission spectroscopy. Two electron-like Fermi surfaces around X（π, 0） are observed, corresponding to the electron doping of 0.23 per Bi site. We clearly resolve anisotropic band splitting along both Г-X and M-X due to the cooperative effects of large spin-orbit coupling and interlayer coupling. Moreover, we observe an almost non-dispersive electronic state around -0.2 eV between the electron-like bands. This state vanishes after in-situ K evaporation, indicating that it could be the localized surface state caused by defects on the cleaved surface.
基金This work was supported by the National Natural Science Foundation of China(No.52372210 and No.52072248)Natural Science Foundation of Guangdong Province of China(No.2023A1515010122 and No.2021A1515012128)Technology plan project of Shenzhen(No.20220810154601001).
文摘BiSe with intrinsic low thermal conductivity has considered as a promising thermoelectric(TE)material at nearly room temperature.To improve its low thermoelectric figure of merit(zT),in this work,Sb and Te isovalent co-alloying was performed and significantly optimized its TE property with weakly anisotropic characteristic.After substituting Sb on Bi sites,the carrier concentration is suppressed by introduction of Sbsingle bond Se site defects,which contributes to the increased absolute value of Seebeck coefficient(|S|).Further co-alloying Te on Se of the optimized composition Bi_(0.7)Sb_(0.3)Se,the carrier concentration increased without affecting the|S|due to the enhanced effective mass,which leads to a highest power factor of 12.8μW/(cm·K^(2))at 423 K.As a result,a maximum zT of∼0.54 is achieved for Bi_(0.7)Sb_(0.3)Se_(0.7)Te_(0.3) along the pressing direction and the average zT(zTave)(from 300 K to 623 K)are drastically improved from 0.24 for pristine BiSe sample to 0.45.Moreover,an energy conversion efficiency∼4.0%is achieved for a single leg TE device of Bi_(0.7)Sb_(0.3)Se_(0.7)Te_(0.3)when applied the temperature difference of 339 K,indicating the potential TE application.
文摘An advanced reliability growth model, i. e. exponential model, was presented to estimate the model parameters for multi-systems, which was synchronously tested, synchronously censored, and synchronously improved. In the presented method, the data during the reliability growth process were taken into consideration sufficiently, including the failure numbers, safety numbers and failure time at each censored time. If the multi-systems were synchronously improved for many times, and the reliability growth of each system fitted AMSAA （Army Material Systems Analysis Activity） model, the failure time of each system could be considered rationally as an exponential distribution between two adjoining censored times. The nonparametric method was employed to obtain the reliability at each censored time of the synchronous multisystems. The point estimations of the model parameters, a and b, were given by the least square method. The confidence interval for the parameter b was given as well. An engineering illustration was used to compare the result of the presented method with those of the available models. The result shows that the presented exponential growth model fits AMSAA-BISE （ Army Material Systems Analysis Activity-Beijing Institute of Structure and Environment） model rather well, and two models are suitable to estimate the reliability growth for the synchronously developed multi-systems.
文摘近年来,大批量煤矿开采已经严重破坏到矿区周围的生态环境,而新时代我国注重绿色发展,这就需要对矿区生态条件进行修复。修复生态可从分析研究该区域的植被覆盖度开始。NDVI时间序列数据是目前最常用的数据源之一,其在全球气候环境变化、植被覆盖动态变化检测、植被信息提取等方面具有广泛应用。但由于传感器、云层覆盖等因素影响,NDVI时序数据比一般数据更容易出现噪声,因此时序数据去噪显得至关重要。文章以宝日希勒矿区为研究区,从目视判别时序曲线、对比去噪样本点的去噪均方根误差、以及变化检测结果精度分析三个角度,在matlab编程软件以及ENVI软件的帮助下,实现这三种去噪算法,并对比分析这3种方法的优点和缺点。研究结果表明:1) 3种去噪算法都有效地对原始NDVI时序数据进行了去噪,且效果明显;2) 不同的去噪方法均存在着过度拟合的现象;3) 对于文章所选的NDVI最大合成数据而言,B-W去噪效果最好,其次是去噪效果一般的BISE算法,S-G算法的去噪效果最差。In recent years, large-scale coal mining has seriously damaged the ecological environment around the mining area. In the new era, China pays attention to green development, which requires the restoration of the ecological conditions of the mining area. Ecological restoration can start from analyzing the vegetation coverage of the area. NDVI time series data is one of the most commonly used data sources at present. It has been widely used in global climate and environmental change, dynamic change detection of vegetation cover, vegetation information extraction and so on. However, due to the influence of sensors, cloud cover and other factors, NDVI time series data are prone to noise, so data denoising is very important. Taking Baorixile mining area as the research area, this paper realizes these three denoising algorithms under Matlab programming software from three angles: visual discrimination of time series curve, comparison of denoising root mean square error of denoising sample points, and accuracy analysis of change detection results, and compares and analyzes the advantages and disadvantages of these three methods. The results show that: 1) The three smoothing algorithms all effectively denoise the original NDVI time series data, and the effect is obvious;2) Ecological restoration can start from analyzing the vegetation coverage of the area;3) For the NDVI maximum synthetic data selected in this paper, B-W has the best denoising effect, followed by bise algorithm, and finally S-G algorithm has the worst denoising effect.
