Magnetic Field‐Enhanced Thermoelectric Performance in Dirac Semimetal Cd3As2 Crystals with Different Carrier Concentrations

The magneto‐thermoelectric figure of merit (ZT) in crystals of the topological Dirac semimetal Cd₃As₂ with different carrier concentrations is studied. The ZTs for all the crystals increase with the temperature and show maxima at high temperatures. Meanwhile, the temperatures corresponding to the ZT maxima increase with the carrier concentration. The limit to the improvement in ZT(T) at high temperature could be related to the unusual large enhancement in thermal conductivity at elevated temperatures. The bipolar effect and Dirac liquid behavior are presented as processes possibly responsible for the peculiar behavior of the thermal conductivity. Applying a transverse magnetic field initially leads to a dramatic enhancement and, subsequently, to a slight reduction in ZT for all the crystals. The maximum ZT achieved in a magnetic field increases with the carrier concentration and reaches 1.24 at 450 K in a magnetic field of 9 T for the crystal with the highest carrier concentration. It is expected that this work will be beneficial to the current interests in optimizing the thermoelectric properties of quantum topological materials.     

SnO2‐C60 Pyrrolidine Tris‐Acid (CPTA) as the Electron Transport Layer for Highly Efficient and Stable Planar Sn‐Based Perovskite Solar Cells

For solar cell applications, Sn‐based hybrid perovskites have drawn particular interest due to their environmental friendliness. Here, a thin layer of C₆₀ pyrrolidine tris‐acid (CPTA) is found essential for achieving high efficiency with planar solar cells of Sn‐based perovskites. As a result, a power conversion efficiency of 7.40% is achieved for {en}FASnI₃ solar cells with a planar n–i–p architecture, and the device exhibits excellent stability in air. For the first time, highly efficient Sn‐based hybrid perovskite solar cells on n–i–p architecture are achieved. A V_oc of 0.72 V is highlighted as the highest V_oc ever reported for FASnI₃ solar cells.     

Ka and Q band propagation experiments in Toulouse using ASTRA 3B and ALPHASAT satellites

From January 2008 to March 2011, ONERA operated in Toulouse, France, a beacon receiver able to collect the 19.7‐GHz beacon signal of the HotBird 6 satellite. In March 2011, the radio frequency chain was modified to be able to receive the 20.2‐GHz ASTRA 3B beacon to benefit from a higher Equivalent Isotropically Radiated Power of the satellite. Since June 2015, a second beacon receiver has been installed and is able to record the 39.4‐GHz beacon signal of the Alphasat satellite. The objective of this paper is to present the results of the first 2 years of measurements (June 2015 to May 2017) of the Q‐band Alphasat propagation experiment in Toulouse, as well as concurrent measurements collected at Ka‐band with ASTRA 3B. First of all, the propagation experiments are briefly described. Second, the results of the statistical analysis are highlighted. Finally, a deep analysis of the performances of the 2 frequency scaling prediction methods recommended in ITU‐R P.618‐13 is performed.     

Downlink Dimensioning for the HSDPA Standard

We present an analytic derivation of downlink dimensioning for a wireless network employing the High Speed Downlink Packet Access (HSDPA) standard [Moulsley, Conference Publication No. 477, IEE 2001], currently being developed by the 3rd Generation Partnership Project (3GPP) [http://www.3gpp.org] as part of the next stage in the evolution of the WCDMA standard. We determine the maximum possible cell radius such that the probability of outage, P_out, at the cells worst location does not exceed a preset value under full load condition. The results of the paper are presented in the form of curves obtained by numerical integration of integral expressions. The results can be used, for instance, to find the increase in cell radius achievable by a certain reduction in the threshold value of the Signal to Interference plus Noise Ratio (SINR) defining outage.Parts of this work were presented at the 2002 IEEE Wireless Personal Multimedia Communications conference (WPMC), Hawaii.Dan Avidor was born in Tel Aviv, Israel, on October 18, 1936. He received the B.Sc. degree in electrical engineering from the Technion-Israel Institute of Technology, Haifa, Israel, in 1958 and the M.Sc. and Ph.D. degrees in engineering from the University of California, Los Angeles, (UCLA) in 1970 and 1981, respectively. After completing his studies for the Ph.D. degree, he returned to Israel, where he served as a Research and Development Department Head in the Israeli defense forces. He is currently a Distinguished Member of Technical Staff in the Wireless Research Laboratory, Bell Labs, Lucent Technologies, NJ, USA. His current research interests are in adaptive arrays, signal processing, and simulation techniques for wireless systems.Sayandev Mukherjee (M92) was born in Bangalore, India in 1970. He received the Bachelor of Technology degree in electrical engineering from the Indian Institute of Technology, Kanpur, India, in 1991, and the M.S. and Ph.D. degrees in electrical engineering from Cornell University, Ithaca, NY, in 1994 and 1997, respectively. Since 1996, he has been a Member of Technical Staff in the Wireless Research Laboratory, Bell Labs, Lucent Technologies, NJ, USA. His research interests include stochastic models, wireless system simulations, and intelligent resource allocation in wireless systems.     

基于统计模型的三维场景重建补洞算法

提出了一种新的处理距离图像(即点云数据)算法。算法提取已经获得的表面数据的特性．计算各个被测的特征值,建立马尔可夫统计模型,描述整个表面的数学特征,进而利用最大似然概率预测丢失位置的数据值,得到被测物体表面的完整的数据描述。使用该算法恢复由于障碍物和表面小良反射特性产生的空洞,具有良好的视觉效果．与测量获得的表面数据具有统一的几何特征。     

掺Er3 铅卤碲酸盐玻璃的光谱特性研究

分别以TeO2-PbCl2、ZnO-Na2O和TeO2-ZnO-Na2O为基质制备了掺Er3+铅卤碲酸盐(EDTPb)玻璃和碲酸盐(EDT)玻璃.差热分析(DTA)结果表明,EDTPb玻璃具有更高的热稳定性.应用McCum-ber原理计算的结果表明4 mol%PbCl2的加入可使EDT玻璃在1.53 μm处的发射截面提高6.7%,其峰值达8.79×10-21cm2,而有效宽度从65.8 nm增加到72.3 nm,因此,PbCl2的加入明显改善了玻璃的发光特性.同时应用Judd-Ofelt理论对2种玻璃中Er3+的自发跃迁几率、荧光分支比和能级寿命等光谱特性进行了计算.     

Y2O3:Eu电致发光膜的制备与结构表征

采用电子束蒸发和射频磁控溅射技术沉积了Y2 O3 :Eu电致发光薄膜 ,对膜进行了不同温度的大气热处理。用原子力显微镜 (AFM)观察了Y2 O3 :Eu膜的表面形貌 ,用X射线 (XRD)分析了Y2 O3 :Eu膜的结构 ,并对两种Y2 O3 :Eu膜的微结构和表面形貌进行了比较。结果表明 ,射频磁控溅射Y2 O3 :Eu膜与电子束蒸发Y2 O3 :Eu膜相比 ,结构更致密 ,表面更平滑 ,而且 ,在 90 0°C高温热处理后 ,溅射膜呈现单斜晶系结构 ,具有该结构的Y2 O3 :Eu膜适宜于作电致发光膜。     

三维微流道系统技术研究

采用LTCC技术,可以获得替代采用硅或其他技术制作的微功能结构,简化工艺,降低成本.重点研究了内嵌三维(3D)微流道系统LTCC多层基板成型中的关键技术:热压和烧结,并进行工艺优化.利用优化的热压、烧结工艺参数,可制备出完好的3D微流道系统LTCC多层基板;通过实验验证,LTCC内嵌三维微流道系统取得了良好的散热效果.     

基于针孔阵列的多光束共焦三维测量系统

提出了一种基于 5 0 0× 5 0 0的针孔阵列的多光束共焦三维测量系统 ,该系统具有测量视场大 ,测量速度快 ,系统结构简单等特点     

嵌入式Linux下S3C2410的调色板彩色显示

嵌入式应用中,由于计算能力以及硬件资源的限制,常需要降低颜色深度,以获得较高的分辨率,因此调色板彩色显示是一种很重要的手段。在此以ARM9核的S3C2410芯片为例,探讨分析调色板的概念及配置方法,通过修改驱动程序,实现了调色板彩色显示,给出了编程实例,总结了实现方法。试验表明,当LCD分辨率较高时,采用调色板彩色显示,解决了屏幕抖动和不连贯现象的发生。