《本期重点导读》

本期【声频工程】栏目刊登了钟祥璋、朱子根有关"灯芯绒吸声特性的实验研究"的文章,讲述了灯芯绒是一种常用的服装布料,又是建筑室内装饰常用的帘幕材料。主要考量用于帘幕时的吸声性能。选择两种绒面的灯芯绒试件,通过测量混响室吸声系数,采用平均吸声系数与降噪系数NRC的评价方法进行分析,探讨在实际使用时影响吸声性能的因素及工程应用。王海、林泰勇关于"Odeon软件Engineering模式计算结果的评价"一文,说     

吸声帘幕的吸声分析

吸声帘幕属于多孔有机纤维吸声材料.吸声帘幕具有防火性、可变吸声性、易安装、装饰性等基本特点.在很多实际工程中,都应用了吸声帘幕.通过实验对吸声帘幕的声学特性进行了研究.     

混响室法测定吸声系数计算误差分析

混响室法测定吸声系数常用赛宾公式来计算,在计算时必须分析其误差大小,使吸声系数的测定值更准确(准确的计算最好用艾润公式)。忽略吸声系数数值客观存在的计算误差,是造成混响时间计算与实测值误差的原因之一。     

声场计算机模拟中吸声系数的修正

计算机声场模拟中,房间表面的吸声性能通常采用混响室法吸声系数来表示.该吸声系数的测量方法是建立在扩散声场基础上得到的,而实际混响室中放置吸声材料后声场并非为扩散场,由此将导致吸声系数的测量误差,影响声场计算机模拟的准确性.通过对混响室声场的模拟计算,建立材料吸声系数与混响时问的关系,并对实测的吸声系数进行修正可提高声场计算机模拟的精度.     

FC穿孔板吸声性能研究

FC穿孔板是常用的吸声装饰材料,以高穿孔率的FC板与板后衬贴不同材料和空腔填充玻璃棉,组成6种吸声构造,分别对4种空腔深度进行混响室吸声测量,通过对吸声系数的分析,探讨板后衬贴材料及填充材料FC穿孔板的吸声效果。     

吸声泡沫玻璃的材料特性及其吸声性能的提高

吸声泡沫玻璃是一种无机多孔材料,它具有良好的防火和耐水性能。介绍了它的材料特性,根据测量的吸声系数分析了密度、板厚、空腔和吸湿对吸声的影响,并且采用板面钻孔和边缘留缝的方法提高其吸声性能。     

新型木丝板吸声性能的测试研究

介绍了一种新型木丝吸声板,该材料具有良好的物理特性和吸声性能。在不同安装条件下对该产品的吸声系数进行了实验室对比测试研究,并对进一步提高其吸声性能的方法进行了探讨,为声学工程的设计提供了实验数据。     

EASE3.0软件应用的可信度研究(二)

4室内材料吸声系数的赋值问题 建筑声学设计计算中，没有限定材料声学特性的取值方式。可以是吸声系数或吸声量。一般厅堂、剧场的观众席吸声性能的计算多数采用每座吸声量。但EASE软件不能直接统计厅堂中各部位的吸声量，只能识别吸声系数。实验测试的2个厅堂均为软座椅，其中沙坪剧院的座椅是专业厂家生产，其吸声性能有明确的数据。学院多功能厅的座椅无现成的数据，     

烧结FeCrAl纤维多孔材料的高温吸声性能

由于航空发动机扇涡轮腔体内为高温环境,需寻找一种吸声材料,此材料既有良好的吸声性能,还有耐高温抗氧化的特殊性能.实验选取FeCrAl纤维为原材料制备烧结纤维多孔材料,在100～500 ℃的测试温度范围内对各样品及梯度结构的吸声性能进行测试,研究温度和厚度对其吸声性能的影响.结果表明,随着温度的升高,吸声系数不再随频率的升高而增大.通过增加材料的厚度也可使吸声性能有较大提高.虽然温度对材料吸声性能影响很大,但梯度结构比单层材料的高温吸声性能好.     

多层微穿孔板的优化设计

影响微穿孔板吸声系数的结构参数很多,设计计算复杂,尤其是对多层微穿孔板复合结构的计算.针对3层及4层微穿孔板复合结构的吸声系数进行了计算,应用遗传算法对其结构参数进行了优化,在常用噪声频率范围内获得了非常饱满的吸声系数曲线,与双层微穿孔板复合结构相比,在吸声系数和吸声频带上都有了很显著的提高.     

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.     

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.     

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.     

Call for Papers

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