定向多节点DF协同通信系统中断概率及功率分配研究

对基于定向天线的多节点DF协同通信系统进行研究,应用协作域的方法推导其中断概率,同时证明了机会中继条件下中断概率最优,并通过数值仿真得出最优功率分配因子范围。仿真结果表明多中继参与的情况下应根据实际场景选择其数量,在同等数量中继节点且功率受限的条件下,机会中继方案能获得更优的中断概率及更简单的功率分配方法。因此在多中继节点DF定向协同通信系统中,可以采用机会中继方案以实现最优的系统性能。     

协作认知无线电网络频谱检测性能分析

阴影热点区域环境复杂,信号传输损耗更大,协作中继转播功能能够提高通信性能.文章对阴影衰落信道上多中继认知无线电系统的联合频谱检测概率进行了分析,计算基于解码转发机制的中继器的成功解码概率;分析中继器对于一级和二级用户的中断概率的影响.误警率为0.1和0.05条件下的检测概率、一级系统和二级系统的中断概率等性能的仿真结果表明:中继器协作检测可以提高检测性能;协作中继转播可以在保证授权用户所需中断概率条件下降低认知用户的中断概率;结合联合频谱检测和协作中继转播,能提高系统通信性能,提高频谱使用效率.     

低信噪比下增强型解码转发协作的性能分析

研究了接收节点将其译码状态反馈给其他节点这一增强性手段对解码转发协作的性能改善情况.推导了低信噪比条件下,增量中继、选择中继的中断概率和吞吐量表达式,给出了中断概率的三阶近似式.结合增量中继、选择中继的各自优点,提出了一种联合中继模式.理论分析和数值仿真表明,提出的联合中继模式在中断概率和吞吐量2个方面性能优越.     

无线紫外光通信组网链路性能分析

为了分析紫外光非视距通信组网链路性能,采用单次散射大气信道传输模型,对紫外光非视距通信的全向发送全向接收和定向发送全向接收两类工作模式进行了理论分析,并在链状和网格状的拓扑结构下分别进行了计算机仿真实验,对比分析了两类工作模式下网络的吞吐量、时延、抖动率、丢包率等性能.结果表明,在紫外无线光Mesh网络的通信中,采用定...     

多中继AF协作系统功率分配研究

功率分配是协作通信中一个重要的研究方向,文章分析了放大转发（AF）协作方式下,基于正交信道的多协作中继系统模型,在此基础上推导了系统中断概率。并以最小化系统中断概率为目标,给出系统功率分配约束表达式,进一步分析了功率分配与中继节点位置的关系,计算求得单中继和两中继情况系统最优功率分配系数。系统仿真表明最优功率分配相对常规的等功率分配,系统性能明显提升。     

双向协作系统的中继选择和功率分配策略

针对瑞利衰落信道下双向多中继协作通信系统,为了降低中断概率,提出了一种基于最小化中断概率的中继选择策略和功率分配方案。首先联合考虑两条链路的中继节点处信噪比和信道增益实现双链路中继选择,然后推导出一种新的最优中继下双向放大转发协作中断概率的近似表达式上界,并利用凸优化求解得到使中断概率最小的最优功率分配解。仿真结果表明,与现有策略相比,提出的策略能够明显降低系统中断概率和误码率,显著提高系统性能。     

Nakagami衰落信道下合作分集的无线家庭网络性能分析

提出在未来无线家庭网中采用合作分集的思想,通信时利用处于空闲状态的终端用户对所发送信息进行中继发送,保证整个网络误码率性能、中断概率以及发送功率达到最佳折衷.在Nakagami平衰落信道条件下研究了再生中继和非再生中继两种合作方式下的中断概率和误码率性能,给出误码率和中断概率的解析表达式,并用matlaab进行仿真,仿真结果表明,在低信噪比条件下再生中继大大优于非再生中继方式,但高信噪比条件下两者性能接近.     

多跳协同中继网络下物理层安全传输方案

针对多跳中继传输系统的信息安全传输问题,提出了一种基于全双工模式下多节点协作干扰(FD-MCJ)的物理层安全传输方案。该方案利用通信网络中的中继节点发送干扰信号恶化窃听节点的接收性能,同时中继节点根据信道状态信息(Channel State Information, CSI)自适应的选择两种情况下的安全传输方案。本文首先利用泊松点过程对窃听节点位置进行安全建模;然后,根据CSI可用程度,给出不同的安全传输具体方案,在考虑系统的跳数、天线间自干扰以及发射功率和干扰功率等因素下,推导FD-MCJ方案下系统保密中断概率的闭式解;最后,数值分析和蒙特卡洛仿真表明,理论推导的正确性以及多跳中继系统中采用全双工多节点协作干扰方案能够有效提升系统安全性能。      

协同通信中双向多中继网络的中断概率分析

针对频率非选择性瑞利衰落信道条件下,研究了双向多中继协同通信系统的中断概率性能.首先基于模型的信号传输过程分析了系统的信道容量.然后根据单条链路接收信噪比的累积分布函数,推导了系统中断概率的闭合上界表达式;根据接收端采取最大比合并时的接收信噪比最大,计算了信噪比最大时的概率密度函数,推导了系统中断概率的闭合下界表达式.最后,结合具体的数值仿真对不同参数下的系统中断概率分别进行了详细的分析比较.仿真实验验证了理论推导的结果,并且还表明了双向多中继模型的中断概率优于双向单中继模型.     

多中继与多用户选择的中继系统安全性能分析

为了考察使用多中继选择与多用户选择的放大转发（AF）中继系统的物理层安全性能,推导了其在瑞利衰落信道上和联合发送天线选择/接收最大比合并天线分集下的非零安全容量概率和安全中断概率的精确表达式以及在高信噪比下的渐近安全中断概率解析表达式。AF中继系统的非零安全容量概率和安全中断概率的数值计算和仿真结果相吻合,验证了以上理论分析的正确性;分析结果表明,其安全分集增益为源节点发射天线数、最优中继节点接收天线数、中继节点数的三者乘积与最优中继节点发射天线数、最优用户接收天线数、用户数三者乘积之间的最小值,且与窃听信道无关。     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

中国建立EB级存储实验室,致力云计算应用(英文)

正With the support of 863 programs,Sugon Information Industry Co.,Ltd.,set up a dawning EB-class storage laboratory to address massive data storage requirements and largescale cloud computing demonstration applications.The Dawning EB-class cloud storage system adopts advanced fault-tolerant architecture,efficient data fault-tolerant algorithms with user authentication and data encryption policies to deal with the"lost""wrong"and"stolen"problems of data for ensuring the reliability and safety of the EB-class storage system in the public network application environments.The Dawning EB-class Storage Laboratory taking advan-