共查询到20条相似文献,搜索用时 78 毫秒
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针对混响室低频混响时间测量的偏差大这一问题,提出对随机噪声信号进行限幅或改用一系列单频信号发生器作稳定激发可显著改善测量结果的偏差。 相似文献
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结合混响室在多功能剧院的应用实例,列举出混响室在剧院中的设置位置及容积的改变,剖析混响室的结构特点,并通过测试数据分析,说明利用混响室改变容积对剧院室内混响时间的调节作用,并对设置混响室引起的声学参数变化进行了分析。 相似文献
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混响时间设计的新趋势 总被引:2,自引:0,他引:2
混响时间设计的新趋势曹孝振(建设部建筑设计院)室内混响时间的听感与混响时间的长短有关,但在混响时间相似或相同的情况下,其听感却有很大的差别,这是众所周知的事,其原因是下列三个因素和它们的综合效应所造成的。(1)早期衰减时间(EDT)在室内混响时间相同... 相似文献
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介绍了声望VS302USB双通道声学分析仪及混响时间计算软件的应用,给出了使用该系统测量混响时间的系统组成及详细的操作过程,对使用中的相关问题进行了归纳总结. 相似文献
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为研究混响室搅拌器位置对测试区域场均匀性影响,采用基于矩量法的电磁仿真软件FEKO对混响室仿真模型进行数值计算,通过与遗传算法相结合对混响室搅拌器位置进行优化,得到了搅拌器位置的最优解以及相应的表征混响室测试区域场均匀性的电场标准偏差值.研究表明:搅拌器位置影响测试区域场均匀性,当搅拌器位置处于最优配置时,测试区域各轴向电场标准偏差较初始状态分别下降了47.4%、20.1%、57.1%,总标准偏差下降了44.0%,测试区域场均匀性较优化前有所提高,提高了混响室用于电磁兼容测试时的准确度. 相似文献
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混响室桨叶夹角对场均匀性影响的仿真及测量 总被引:2,自引:0,他引:2
用HFSS10.0对混响室进行仿真,研究了搅拌器的夹角对场均匀性的影响。首先阐述了混响室的特点及其场均匀性校准的原理和方法,然后根据实际混响室的尺寸,用HFSS10.0进行建模,通过仿真得出搅拌器在不同夹角情况下的场均匀性。最后根据仿真结果,对混响室的场均匀性进行测量,验证了合理的设计搅拌器会改善混响室的场均匀性,降低最低可用频率。 相似文献
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关于室内混响时间的计算问题 总被引:3,自引:0,他引:3
室内混响时间的计算公式只是在“理想”状况下实用,由于室内空间结构、吸声材料和使用环境的复杂性,因此在利用公式进行计算中,要特别注意一些“量”的修正,才能使计算值比较准确。 相似文献
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Admittance (ac) measurements were carried out to determine the interface trap density (Dit) as a function of energy E in the Si bandgap at interfaces of Si with different insulating oxides (Al2O3, ZrO2, HfO2). The results are compared to those of the conventional thermal SiO2/Si interface. The results show that a significant portion of the interface trap density in the as-deposited and de-hydrogenated samples is related to the amphoteric Si dangling bond defects (Pb0 -centers). The Dit is much enhanced for the Al-containing insulators as compared to Si/SiO2 but can be reduced by annealing in O2. As to annealing in H2, efficient passivation of Pb0 centers by hydrogen is achieved for Si/ZrO2 and Si/HfO2 interfaces, yet it fails for Si/Al-containing oxide entities. Among the insulators studied, the results suggest HfO2 to be the best choice of an alternative insulator. 相似文献
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Tanaka H. Uchida H. Ajioka T. Hirashita N. 《Electron Devices, IEEE Transactions on》1993,40(12):2231-2236
The effect of surface roughness of Si3N4 films on time-dependent dielectric breakdown (TDDB) characteristics of SiO2/Si3N4/SiO2 (ONO) stacked films was investigated. The surface roughness of Si3N 4 films-was found to become higher with increasing deposition temperature and to cause the degradation of TDDB characteristics of ONO films in DRAMs. A local thinning of ONO films, evaluated from the TDDB characteristics, agreed with the surface roughness measured by atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM). Dependence of time to breakdown of ONO films on the deposition conditions was interpreted by electric field intensification due to the surface roughness of Si3N4 films 相似文献
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高频激励方式由于其允许高注入功率密度和优越的调制性能正在取代CO2激光器的直流激励方式。本文根据放电各物理过程的特征时间,讨论了DC,AC,RF和微波激励方式的特点。 相似文献
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V.V. Afanasev Y.G. Fedorenko A. Stesmans 《Materials Science in Semiconductor Processing》2004,7(4-6):191
The energy distribution of extended and localized electron states at the Ge/HfO2 interface is determined by combining the internal photoemission of electrons and holes from Ge into the Hf oxide and AC capacitance/conductance measurements. The inferred offsets of the conduction and valence band at the interface, i.e., 2.0 ± 0.1 and 3.0 ± 0.1 eV, respectively, suggest the possibility to apply the deposited HfO2 layer as a suitable insulator on Ge. The post-deposition annealing of the Ge/HfO2 structures in oxygen results in 1 eV reduction of the valence band offset, which is attributed to the growth of a GeO2 interlayer. However, this treatment enables one to substantially reduce the density of Ge/HfO2 interface traps, approaching ≈1×1012 cm−2 eV−1 near the Ge midgap. 相似文献
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采用铌铁矿前驱体两步法制备了Pb(Zn1/3Nb2/3)0.2(Hf1-xTix)0.8O3(PZNH1-xTx)钙钛矿压电陶瓷,研究了铪钛比对陶瓷相结构、电学性能和能量收集特性的影响。结果表明,当x=0.52时,陶瓷样品位于准同型相界,具有最优综合压电性能:居里温度TC=287 ℃,品质因数FOM≈14 753×10-15 m2/N,压电电荷常数d33=492 pC/N。由该组成材料构建的悬臂梁型压电能量收集器输出功率密度高达4.16 μW/mm3,所转化的电能可成功点亮138盏并联的LED灯。结果表明,PZNHT陶瓷在压电能量收集领域具有良好的应用潜力。 相似文献
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H. Yamamoto 《Microelectronics Reliability》1996,36(2):151-168
A (linear or circular) connected-(r1, s1)-or-(r2, s2)-or-. .-or-(rk, sk)-out-of-(m, n): F lattice system is the (linear or circular) (m, n)-lattice system if the system fails whenever all components in a connected-(r1, s1)-submatrix or all components in a connected-(r2, s2)-submatrix or . . or all components in a connected-(rk, sk)-submatrix fail. This paper presents a recursive algorithm for the reliability of the (linear or circular) connected-(r1, s1)-or-(r2, s2)or-. .-or-(rk,sk)-out- of-(m, n):F lattice system. The recursive algorithm requires
time and
time in the linear case and the circular case, respectively Furthermore, we can reduce the more computing time in the statistically independent and identically distributed case or considering some special systems. Especially, the closed formula is given for the reliability of the linear connected-(2, 1)-or-(1, 2)-out-of-(m, 2): F lattice system in the statistically independent and identically distributed case. 相似文献
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《Quantum Electronics, IEEE Journal of》2007,43(2):157-167
The continuous-wave laser operation of Nd-doped tetragonal NaLa(WO 4)2 crystal is studied at room temperature by optical pumping in the spectral region overlapping AlGaAs diode laser emission. This crystal has inhomogeneously broadened optical bands. From the room-temperature spectroscopic parameters determined it is found that the optimum Nd concentration for the 4F3/2rarr4IJ laser channels must be in the 3-5 at.% range. For J=11/2 and 13/2 channels (lambdaap1.06 and 1.3 mum) the most favourable polarization configuration is parallel to the crystallographic c axis, while for J=9/2 little polarization dependence of the laser efficiency is predicted. Laser operation was achieved with a 3.35 at.% Nd-doped sample grown by the Czochralski method. The laser operation was tested in an hemispherical optical cavity pumped by a Ti:sapphire laser. Stimulated emission at lambda=1056 nm was achieved for a wide spectral pumping range, lambda=790-820 nm. Stimulated Raman scattering was achieved in the picosecond regime with an efficiency similar to that of monoclinic KY(WO4)2 reference compound 相似文献
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TiO_2/SiO_2、ZrO_2/SiO_2多层介质膜光学损耗及激光损伤研究 总被引:9,自引:0,他引:9
以TiO_2/SiO_2及ZrO_2/SiO_2多层介质膜为例,测试了不同工艺条件及不同膜系结构下薄膜样品的光学损耗及激光损伤阈值,同时对实验结果作了初步的分析讨论. 相似文献
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《压电与声光》2001,23(5):370-372
系统地研究了xPb(Y1/2Nb1/2)O3-(1-x)Pb(Zr1/2Ti/2)O3三元系铁电陶瓷材料,测量并计算了不同组分时的压电常数(d33)、介电常数(εT33/ε0)、机电耦合系数(kp、k31)、以及弹性柔顺系数(sK11、sE12、sK33),对0.07Pb(Y1/2Nb1/2)O3-0.93Pb(Z[1/2Ti1/2)O3材料,D33为327×10-12C/N,介电常数εT33/ε0为1350,机电耦合系数kp大于0.6,弹性常数SE11和SE33均大于17×10-12m2/N.实现发现,当x大于0.55时,xPb(Y1/2Nb1/2)O3-(1-x)Pb(Zr1/2T11/2)O3不再是铁电材料. 相似文献