TDOA中几种时延估计算法的比较

在现有的传声器阵列声源定位方法中,基于声达时间差(TDOA)估计定位法计算量较小,定位精度较高,同时也易于实现实时系统,是目前声源定位法中常用的方法。采用该方法最重要的就是进行时间延迟估计(TDE),其精确性直接影响到定位的准确与否。概括了基于传声器阵列的声达时间差(TDOA)估计定位法中几种时间延迟估计的算法,给出了部分算法的仿真结果,分析了每种算法中存在的优缺点并同时指出了需进一步研究的问题。     

基于BP神经网络的双耳声源定位算法

为了提高复杂声学环境中双耳声源定位性能,本文利用多种双耳空间特征参数,提出了基于神经网络方法的鲁棒双耳声源定位算法。本文将不同声学环境下双耳声信号对应的互相关函数、耳间强度差等空间定位线索,作为输入特征,用于训练BP神经网络。在混响和噪声环境下,与传统双耳定位算法相比,本文基于BP神经网络的双耳定位算法的定位性能有显著提高,特别是低信噪比条件下,定位正确率提高更为显著。     

TDOA声源定位中阵列阵型对误差的影响

在麦克风阵列声源定位中,不同阵列阵型及声源频率高低均对定位结果产生影响,探讨上述不同变量对定位结果产生误差的定量分析。使用到达时间差测量(TDOA)算法,运用16个麦克风分别组成十字型、同心圆、方型、L型、Y型阵列,探讨不同形状的麦克风阵列在不同频率声源下所产生的定位误差,并在Matlab上进行仿真分析,尝试得到较为准确的声源定位结果,提出一种误差最小的用于麦克风阵列声源定位的同心圆阵列阵型。     

一种用于低空声源目标超视距被动声定位的新方法

该文提出了一种用于低空声源目标超视距被动声定位的新算法.该算法根据低空声源目标的声信号在定位反射点的基础上定位目标点,能有效降低声信号超视距传播误差的影响,提高定位精度,为雷达进一步跟踪和定位提供重要信息.仿真结果表明在时延估计精确的情况下,该方法对隐蔽于山后的低空声源目标的位置有较好的估计效果.     

基于可见光通信的BP神经网络室内定位算法

提出一种基于可见光通信的BP神经网络室内定位算法,首先通过MDS-MAP算法和最小二乘法获得全网节点的相对坐标,再利用信源节点的坐标信息得到网络内所有节点的绝对坐标,最后通过单隐层BP神经网络优化定位结果。仿真结果表明,该算法比MDS-MAP算法和MDS-MAP(P)算法的相对定位误差小,应用于室内定位可以得到更高的定位精度。     

基于BP神经网络模型的RSSI测距方法研究

针对传统信号传播路径损耗模型接收的信号强度指示(received signal strength indication, RSSI)测距误差较大, 提出了基于反向传播(back propagation, BP)神经网络模型的RSSI测距方法.首先, 研究分析传统信号传播路径损耗模型及测距误差; 其次, 利用BP神经网络构建新的路径损耗模型, 并将该模型应用到RSSI测距中, 对基于BP神经网络模型的RSSI测距方法进行研究; 最后, 通过实验和MATLAB仿真对测距方法进行验证.仿真结果表明:BP神经网络模型的RSSI测距误差比传统信号传播路径损耗模型的RSSI测距误差要小.     

基于广义S变换的声发射信号分析及定位

针对声发射信号分析和声源定位问题,提出了基于广义S变换的声发射信号分析方法和三维空间定位方法,推导出了广义S变换的实现过程,使用广义S逆变换对信号进行去噪重构.为保证各传感器时差的准确性,本文利用广义S变换分析声发射信号,提取其主频带能量序列曲线上峰值所对应的时间进行时差计算,然后结合三维空间定位方法对声发射源进行精确定位.仿真实验结果表明该算法能够实现声发射信号的特征提取和准确定位,且误差小,可靠性好.     

基于RBF神经网络的被动声定位算法研究

提出了基于RBF神经网络的被动声定位算法.该算法根据TDOA定位原理,以四元十字阵作为定位模型,利用RBF神经网络较快的学习特性和逼近任意非线性映像的能力,实现对声源的快速准确定位,并与WLS算法、Chan算法、Taylor算法作对比分析.仿真结果表明,该算法定位精度高,鲁棒性好,性能优于其他算法.     

用于视频监控的特定声实时定位系统

设计了一种用于视频监控的具有较强抗干扰能力的特定声定位实时系统。本系统利用广义互相关算法(GCC)估计声音到达2个传声器的时间差(TDoA),以此计算声源的方向角。本系统具有特定声检测功能,只有特定声出现时才输出定位结果,提高了系统的抗干扰能力。实验证明,该系统能够实时地对枪声进行定位,当枪声在±30°范围的时候,室内测试的定位误差在±3°以内;室外测试定位误差在±5°以内。     

基于NARX神经网络的组合导航系统设计

针对捷联组合导航系统在定位信号无法获取的情况下定位误差大和BP神经网络定位的波动问题提出了基于NARX神经网络的导航算法。该方法在输入端加入输出输入量的时间序列,在定位信号可以获取时间段内对神经网络进行训练,不可获取时使用NARX预测的数据对系统进行补偿,提高定位精度。实验结果表明在30s的失锁时间内NARX神经网络定位精度在3m以内,迭代次数小于15次且数据波动较小,可以准确的预测导航位置。     

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.     

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.     

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.     

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.     

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.     

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.     

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     

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正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its