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981.
This paper presents an ionic smoke sensor working without a radioactive ionization source. The presence of smoke particles reduces significantly the effective corona discharge threshold of air by a factor greater than 5. The smoke sensor consists of a wire under an intermediate continuous voltage which generates a current only in presence of smoke. The sensor electric consumption is therefore very low and can operate for a long time. Results of a prototype operating under 600 V with a 25-μm-diameter wire are shown. 相似文献
982.
A mathematical formalism related to the approximate as well as the accurate interferometric data reduction schemes is briefly outlined and subsequently applied in the reconstruction of the assumed (Luneburg) axisymmetric refractive index distribution. The presented comparative analysis confirms the generally held opinion that the approximate methods (“straight-line” and Kokubun-Iga approaches) may provide quite reasonable results in the examination of refractively inhomogeneous disturbances characterized by weak gradient and moderate index variation. On the other hand, the accurate scheme for transverse interferometric data interpretation and reduction, based on the close-form correlation between the fringe shift and the deflection function, [1] remains the only method for reliable reconstruction of strongly refracting index profiles, independently of magnitude of refraction and ambiguity of the fringes. This fact is of considerable importance for transverse interferometry of fibers (preform rods) and/or GRIN-rod lenses characterized by high numerical apertures. 相似文献
983.
Abstract This article presents experimental results demonstrating the performance of an erbium-doped silica fiber as a remote temperature sensor in the interval from 20°C to 200°C. The sensor is based on the change in the fluorescence intensity ratio of two spectral bands as a function of temperature. The green fluorescence signal was generated by up-conversion processes in the erbium-doped fiber pumped at 975 nm. A radiometric analysis was applied to the erbium-doped fiber to evaluate its performance as a temperature sensor, and the results from this analysis were compared against other rare-earth-doped fiber sensors that utilize the intensity ratio technique. 相似文献
984.
时间延迟积分型面阵CMOS图像传感器MTF速度失配模型研究 总被引:3,自引:2,他引:1
研究了时间延迟积分型面阵互补金属氧化物半导体(CMOS)图像传感器调制传递函数(MTF)速度失配特性,在分析累加级数、像素尺寸、镜头放大倍数、行周期及电机运动速度失配等影响因素的基础上,建立了MTF速度失配模型。基于现场可编程门阵列(FPGA)开发板,搭建面阵CMOS图像传感器实现线阵时间延时积分(TDI)的CMOS测试系统。实验结果表明,在光强为3lx,速度失配M(ΔV/V)<2,8级时间延迟积分与面阵成像相比,MTF值提高50%;当累加级数为8级,速度失配满足M(ΔV/V)=2的速度失配容限时,奈奎斯特频率处的MTF值下降10%,当速度失配达到M(ΔV/V)=10时,MTF值下降35%。 相似文献
985.
We analyze an N-policy of a discrete time Geo/G/1 queue with disasters. We obtain the probability generating functions of the queue length, the sojourn time, and regeneration cycles such as the idle period and the busy period. We apply the queue to a power saving scheme in wireless sensor networks under unreliable network connections where data packets are lost by external attacks or shocks. We present various numerical experiments for application to power consumption control in wireless sensor networks. We investigate the characteristics of the optimal N-policy that minimizes power consumption and derive practical insights on the operation of the N-policy in wireless sensor networks. 相似文献
986.
This paper addresses two versions of a lifetime maximization problem for target coverage with wireless directional sensor networks. The sensors used in these networks have a maximum sensing range and a limited sensing angle. In the first problem version, predefined sensing directions are assumed to be given, whereas sensing directions can be freely devised in the second problem version. In that case, a polynomial-time algorithm is provided for building sensing directions that allow to maximize the network lifetime. A column generation algorithm is proposed for both problem versions, the subproblem being addressed with a hybrid approach based on a genetic algorithm, and an integer linear programming formulation. Numerical results show that addressing the second problem version allows for significant improvements in terms of network lifetime while the computational effort is comparable for both problem versions. 相似文献
987.
本文介绍了两种热电偶冷端温度补偿电路在物理实验测量中的应用及校准方法,对热电偶的工作原理、冷端温度补偿必要性作了说明,并详细介绍了冷端温度补偿过程. 相似文献
988.
In this study, we have successfully synthesized a novel coumarin-based dendrons derivative CD and its chemical structure was characterized by 1H NMR, 13C NMR and ESI-HR-MS. The sensor CD showed an obvious “on-off” fluorescence quenching response toward Cu2+ with a maximum quenching efficiency of 99.8%. The CD-Cu2+ complex showed an “off-on” fluorescence enhancement response toward PPi over many competitive anions. The detection limit of the sensor CD was 0.29?×?10?6?M to Cu2+ and 2.39?×?10?9?M to PPi. In addition, the sensor CD showed a 1:1 binding stoichiometry to Cu2+ and the sensor CD-Cu2+ showed a 2:1 binding stoichiometry to PPi in CH3CN/HEPES buffer medium (9:1 v/v, pH?=?7.2). The stable pH range of sensor CD to Cu2+ and CD-Cu2+ to PPi was from 3 to 8. 相似文献
989.
A new oligothiophene-based sensor 3 TH for monitoring Hg2+ has been designed and synthesized based on the intramolecular charge transfer (ICT) mechanism. The 3 TH shows the significant specificity toward Hg2+ through “naked-eye” colorimetric detection as well as via ratiometric fluorescence enhancement response with low detection limit of 62 nM. In addition, sensor 3 TH shows high selectivity and sensitivity for Hg2+ with fast response in a suitable pH range. Moreover, the 3 TH-based test strips was used to conveniently detect Hg2+ ions in water. Furthermore, considering its good ‘‘turn-on’’ fluorescent sensing behavior and low cell cytotoxicity, 3 TH was successfully applied to detect and image Hg2+ in real water samples and living cells, which shows great potentials for application in environmental and biological systems. 相似文献
990.
《Tetrahedron》2019,75(30):3982-3992
A novel colorimetric and fluorometric dual-channel sensor DA with a favorable optical property and high specificity via a facile synthesis for Cu2+ was developed. DA showed a remarkably rapid response and high selectivity for Cu2+ over other metal ions with low detection limit of 15.1 nM. The sensing mechanism of DA for Cu2+ was based on the chelation-enhanced fluorescence quenching (CHEQ) mechanism, and further confirmed by optical measurements, FTIR, HRMS and DFT calculations. Importantly, DA for sensing Cu2+ possessed excellent sensing performances including colorimetric and fluorometric dual-mode detection, fast response, good reversibility, wide pH response range and strong anti-interference ability. Moreover, the DA could be not only applied to quantitatively detect Cu2+ in environmental water, food and drink samples, but also show highly colorimetric detection of Cu2+ on test strips and silica, indicating its possibility to be utilized as a convenient and low-cost sensor for environment and food monitoring. 相似文献