The most commonly found fingermarks at crime scenes are latent and, thus, an efficient method for detecting latent fingermarks is very important. However, traditional developing techniques have drawbacks such as low d...The most commonly found fingermarks at crime scenes are latent and, thus, an efficient method for detecting latent fingermarks is very important. However, traditional developing techniques have drawbacks such as low detection sensitivity, high background interference, complicated operation, and high toxicity. To tackle this challenge, we employed fluorescent NaYF4：Yb, Er upconversion nanoparticles （UCNPs）, which can fluoresce visible light when excited by 980 nm human-safe near-infrared light, to stain the latent fingermarks on various substrate surfaces. The UCNPs were successfully used as a novel fluorescent label for the detection of latent fingermarks with high sensitivity, low background, high efficiency, and low toxicity on various substrates including non-infiltrating materials （glass, marble, aluminum alloy sheets, stainless steel sheets, aluminum foils, and plastic cards）, semi-infiltrating materials （floor leathers, ceramic tiles, wood floor, and painted wood）, and infiltrating materials such as various types of papers. This work shows that UCNPs are a versatile fluorescent label for the facile detection of fingermarks on virtually any material, enabling their practical applications in forensic sciences.展开更多
柔性直流电网(voltage source converter-based high voltage DC,VSC-HVDC)对直流线路保护提出了高速动性和高可靠性的要求。首先,推导了柔直电网直流线路发生区内、外故障时线模故障分量电压行波的解析表达式,该解析表达式包含行波传...柔性直流电网(voltage source converter-based high voltage DC,VSC-HVDC)对直流线路保护提出了高速动性和高可靠性的要求。首先,推导了柔直电网直流线路发生区内、外故障时线模故障分量电压行波的解析表达式,该解析表达式包含行波传播项和直流线路边界项。理论证明了:线路发生区内故障时,线模故障分量电压行波传播项指数系数大于区外故障时的指数系数,且该指数系数不受过渡电阻影响。之后,引入Levenberg-Marquart(LM)算法提取指数系数构造了高灵敏度、高可靠性的单端快速保护方法及保护方案。最后,仿真验证了推导分析的正确性,验证了提取出的指数系数能有效反映故障位置,且其保护方案能快速可靠地识别不同距离、不同类型的故障,具有较高的耐过渡电阻能力。保护方案无需高采样频率。展开更多
Atomic spin gyroscope (ASG) based on comagnetometer is a high sensitive and compact gyroscope for future inertial navigation applications. The start-up time was several hours of the demonstrated ASGs based on 3He-K or...Atomic spin gyroscope (ASG) based on comagnetometer is a high sensitive and compact gyroscope for future inertial navigation applications. The start-up time was several hours of the demonstrated ASGs based on 3He-K or21 Ne-Rb-K comagnetometer, and only a few inertial navigation applications allow such a long time for preparation. We report the demonstration of an ASG based on 129Xe-Cs comagnetometer, which decreases the start-up time to 10 minutes and decreases the operation temperature by 40% as well. By operating this ASG in spin exchange relaxation free regime, a sensitivity of 7×10 -5 °/(s Hz1/2) was achieved.展开更多
基金This work is supported by the National Natural Science Foundation of China （No. 21205139）, the Application and Innovation Project of Chinese Ministry of Public Security （No. 2012YYCXXJXY127）, and the Program for Liaoning Excellent Talents in University （No. LJQ2014130）. MYY is thankful for the grant support from the National Natural Science Foundation of China （Nos. 20804037 and 21172194） and National High Technology Research and Development Program 863 （No. 2013AA102507）. YZ, PHQ and CBM would like to thank the financial support from National Institutes of Health （No. EB015190）, National Natural Science Foundation （No. CMMI-1234957 and DMR-0847758）, Department of Defense Peer Reviewed Medical Research Program （No. W81XWH-12-1-0384）, Oklahoma Center for the Advancement of Science and Technology （No. HR14-160） and Oklahoma Center for Adult Stem Cell Research （No. 434003）.
文摘The most commonly found fingermarks at crime scenes are latent and, thus, an efficient method for detecting latent fingermarks is very important. However, traditional developing techniques have drawbacks such as low detection sensitivity, high background interference, complicated operation, and high toxicity. To tackle this challenge, we employed fluorescent NaYF4：Yb, Er upconversion nanoparticles （UCNPs）, which can fluoresce visible light when excited by 980 nm human-safe near-infrared light, to stain the latent fingermarks on various substrate surfaces. The UCNPs were successfully used as a novel fluorescent label for the detection of latent fingermarks with high sensitivity, low background, high efficiency, and low toxicity on various substrates including non-infiltrating materials （glass, marble, aluminum alloy sheets, stainless steel sheets, aluminum foils, and plastic cards）, semi-infiltrating materials （floor leathers, ceramic tiles, wood floor, and painted wood）, and infiltrating materials such as various types of papers. This work shows that UCNPs are a versatile fluorescent label for the facile detection of fingermarks on virtually any material, enabling their practical applications in forensic sciences.
文摘柔性直流电网(voltage source converter-based high voltage DC,VSC-HVDC)对直流线路保护提出了高速动性和高可靠性的要求。首先,推导了柔直电网直流线路发生区内、外故障时线模故障分量电压行波的解析表达式,该解析表达式包含行波传播项和直流线路边界项。理论证明了:线路发生区内故障时,线模故障分量电压行波传播项指数系数大于区外故障时的指数系数,且该指数系数不受过渡电阻影响。之后,引入Levenberg-Marquart(LM)算法提取指数系数构造了高灵敏度、高可靠性的单端快速保护方法及保护方案。最后,仿真验证了推导分析的正确性,验证了提取出的指数系数能有效反映故障位置,且其保护方案能快速可靠地识别不同距离、不同类型的故障,具有较高的耐过渡电阻能力。保护方案无需高采样频率。
基金supported by the National Natural Science Foundation of China (60825305, 61121003)the National Basic Research Program of China (2009CB724002)the Defense Industrial Technology Development Program of China (B2120110002)
文摘Atomic spin gyroscope (ASG) based on comagnetometer is a high sensitive and compact gyroscope for future inertial navigation applications. The start-up time was several hours of the demonstrated ASGs based on 3He-K or21 Ne-Rb-K comagnetometer, and only a few inertial navigation applications allow such a long time for preparation. We report the demonstration of an ASG based on 129Xe-Cs comagnetometer, which decreases the start-up time to 10 minutes and decreases the operation temperature by 40% as well. By operating this ASG in spin exchange relaxation free regime, a sensitivity of 7×10 -5 °/(s Hz1/2) was achieved.
