1 446座交响音乐厅音质设计与评价

介绍了长沙1 446座交响音乐厅的音质设计指标及技术措施,运用计算机模拟和声学缩尺模型两种方法对交响音乐厅进行了音质辅助设计,音乐厅竣工后也进行了现场音质测试。计算机模拟、缩尺模型试验与实测结果均表明交响音乐厅的音质效果是令人满意的。最后采用灰色关联度分析方法对交响音乐厅进行了音质评价,评价结果与现场演出的主观反馈也是一致的,这也说明交响音乐厅的音质设计是相当成功的。     

音乐厅建声设计技术的传承与发展

综述了国内外音乐厅设计与建设的发展历史和过程,介绍了国内外近四十个音乐厅的建设与设计概况及规模体形、主要音质指标和主观音质评价等级等.文中还着重介绍了音乐厅音质设计的三大方面和六点关键技术及我国音乐厅建声设计技术的传承与发展概况.     

两个水景剧院的建声设计与音质模拟

概述了建于远香湖湖畔的上海嘉定保利大剧院和建于小东海与鹿回头湾交汇处的三亚半岛音乐厅两个水景剧院的建筑概况,重点介绍了保利剧院1500座歌剧厅和半岛音乐厅1300座歌剧厅的音质设计思想、技术指标及建声措施,并对两个水景剧场进行了厅堂音质计算机模拟分析,同时还完成了保利1500座歌剧厅1：10声学缩尺模型试验,最后依据计算机空满场模拟结果对两个剧场的音质进行了初步评估。     

最佳混响时间

在厅堂的音质设计中,混响时间是建声设计的重要指标,确定出各类厅堂的最佳混响时间是决定音质效果的重要因素。文中推荐了音乐厅、语言用厅、影剧院、娱乐场所、体育馆等的最佳混响时间。     

音乐厅音质设计进展及问题探讨

音乐厅音质设计是室内声学中颇受关注的热点,大量研究成果显示了它的深入和进展,对当前国内大量兴建的音乐厅设计颇具参考价值。文章对下列四个方面展开了讨论:(1)音乐厅的明晰度、响度以及低音比的考量,(2)音乐厅体型选择以及座掎包饰程度的选定(3)耦合空间选用与实用中存在的问题,(4)空间感参量中的环绕感(listener envelopment,LEV)与視在声源宽度(apparent source width,ASW)在音质设计实施中的一些问题。     

世界著名的音乐厅

顾名思义音乐厅是欣赏音乐的地方,首先音乐厅要有良好的音质,除此之外,还要有很好的人文环境。音乐厅建筑的内环境与各时期的音乐作品和它们代表的思想、感情和风格之间以及与相应时期的音乐厅建筑之间有着浓密的亲缘关系,已共同体现对某些艺术的追求。下面介绍几个在这些方面都很有特点的典型音乐厅。     

厅堂音质空间感主观评价方法的实验研究

厅堂的空间感（Spatial Impression）作为音乐厅音质的重要评价参量现已得到广泛认同。通过近期的研究实践，介绍了厅堂音质空间感的主观评价方法，其中包括在消声室内构建多通路的声场模拟系统，主观音质评价实验中成对判断的具体步骤，相应的心理尺度计算，以及数据统计方法。最后给出了典型的实际测量结果。     

音乐厅中后期反射声对空间感的影响

空间感是音乐厅音质中很重要的主观感觉.起初人们对空间感的研究主要集中在与早期侧向反射声有关的空间响应上,近年的研究结果使人们更多地了解到后期反射声也对空间感有所影响.文章将主要介绍音乐厅中后期反射声对空间感主要是听者环绕感(LEV)的影响.     

音乐厅中后期反射声对空间感的影响

空间感是音乐厅音质中很重要的主观感觉。起初人们对空间感的研究主要集中在与早期侧向反射声有关的空间响应上，近年的研究结果使人们更多地了解到后期反射声也对空间感有所影响。文章将主要介绍音乐厅中后期反射声对空间感主要是听者环绕感（LEV）的影响。     

音乐厅舞台音质与声学设计

舞台音质对音乐厅演出效果起重要作用。为了使全乐队演出协调,乐师们要求听好自己的和来自其他演员的声音。因此,为使所有器乐和歌声达到适当平衡,以取得良好的合奏效果,将涉及到舞台设施、乐器特征以及如何把声音合适地反射给乐师们。此外,根据乐师主观意见选用恰当的客观声学参量很重要,同时还要考虑用怎样的建筑措施使之实现。这项研究历史较短,不少问题有待探索。文章对此作了综述与评论。     

大中型报告厅的建筑声学改造技术研究

对大中型报告厅的室内音质缺陷和相应声学改造原则进行了初步分析和探讨。通过对工程实践的总结,得出了6种适用于大中型报告厅声学改造的技术措施,确保了在声学改造时,既不降低原有的室内美学品质,又满足室内声学的要求。同时,部分声学改造技术已应用在重庆市渝州宾馆中华厅的声学改造实例中,改造后的混响时间、声场不均匀度均得到了明显改善,良好的声学效果也表明了该技术措施的适用性。     

Nondestructive Measurement of Hall Coefficient for Materials Characterization

The Hall effect is widely exploited in NDE for measuring unknown weak magnetic fields using a small piece of conducting material of known high Hall coefficient. The Hall effect could be also exploited in NDE for measuring the unknown weak Hall coefficient of conducting materials using a strong applied magnetic field, but such measurements are fraught with difficulties because of the need to cut the specimen into a small piece similar to a Hall sensor, which of course is inherently destructive. This paper tries to answer the question how the need for destructive cutting in order to produce a measurable Hall voltage could be avoided. The underlying problem is that the Hall effect produces a Hall current that is normal to the conduction current but does not directly perturb the electric potential distribution unless the Hall current is intercepted by the boundaries of the specimen. This study investigated the feasibility of using alternating current potential drop techniques for nondestructive Hall coefficient measurement in plates. Specifically, the directional four-point square-electrode configuration is investigated with superimposed external magnetic field. Two methods are suggested to make Hall coefficient measurements in large plates without destructive machining. At low frequencies constraining the bias magnetic field can replace destructively constraining the dimensions of the specimen. At sufficiently high inspection frequencies the magnetic field of the Hall current induces a strong enough Hall electric field that produces measurable potential differences between points lying on the path followed by the Hall current even when it is not intercepted by either the edge of the specimen or the edge of the magnetic field. Both techniques are investigated first analytically to illuminate the underlying physics and then by numerical simulations to make useful quantitative predictions.     

Mechanical Analogue of a Majorana Bound State

The discovery of topologically nontrivial electronic systems has opened a new age in condensed matter research. From topological insulators to topological superconductors and Weyl semimetals, it is now understood that some of the most remarkable and robust phases in electronic systems (e.g., quantum Hall or anomalous quantum Hall) are the result of topological protection. These powerful ideas have recently begun to be explored also in bosonic systems. Topologically protected acoustic, mechanical, and optical edge states have been demonstrated in a number of systems that recreate the requisite topological conditions. Such states that propagate without backscattering could find important applications in communications and energy technologies. Here, a topologically bound mechanical state, a different class of nonpropagating protected state that cannot be destroyed by local perturbations, is demonstrated. It is in particular a mechanical analogue of the well‐known Majorana bound states (MBSs) of electronic topological superconductor systems. The topological binding is implemented by creating a Kekulé distortion vortex on a 2D mechanical honeycomb superlattice that can be mapped to a magnetic flux vortex in a topological superconductor.     

Hall effect and magnetoresistance in extrinsic piezoelectric semiconductors

The Hall effect and transverse magnetoresistance in extrinsic piezoelectric semiconductors such as InSb are investigated according to the scattering processes of carriers in semiconductors. These scattering processes contain the acoustic phonon scattering, the piezoelectric scattering, and the ionized-impurity scattering. The energy band structure of carriers in semiconductors is assumed to be nonparabolic. Results show that Hall angle, Hall coefficient, and transverse magnetoresistance depend strongly on the dc magnetic field and carrier density due to the energy-dependent relaxation time. Comparison with experimental data is made. It is also found that the magnetoresistance in degenerate InSb oscillates with the dc magnetic field due to the scattering of carriers with impurities in semiconductors.     

X-ray topography of piezoelectric La(3)Ta(14)Ga(5.5)O(14) crystal grown by Czochralski Method.

We performed synchrotron X-ray topography on a La(3)Ta0(0.5)Ga (5.5)O(14) (LTG) crystal grown by the Czochralski method. Since a synchrotron X-ray source can provide high-energy X-rays, one can detect bulk structures by X-ray topography. LTG is one of the most attractive piezoelectric crystals along with La(3)Ga(5)SiO(14) (LGS) because of its excellent acoustic properties (temperature compensation of acoustic losses). Since LTG single crystals can be grown from a stoichiometric melt, it was expected that single crystals with better quality than the LGS crystal, which cannot be grown from a stoichiometric system but only from a congruent melt, can be obtained. However, 60 keV X-ray topography revealed that the LTG crystal quality was not as high as the LGS crystal quality. The crystal quality of the central region was lower than that of the surrounding region.     

非线性声波方程的几种解法对比

在医学诊疗领域及微、介观损伤的无损检测行业中,经常需要对介质的材料非线性系数进行表征,以得到局部区域更加精细的力学性能变化.文章在简述各向同性固体和理想流体介质中的非线性声波方程的基础上,证实了它们具有相同的形式,这表明它们的解也应具有相同的形式和性质.介绍了求解非线性声波方程的五种方法,包括有限差分、有限元、摄动法、...     

一种二分迭代实时声线修正算法

为提高对水下目标的定位精度,提出并实现了一种二分迭代实时声线修正算法。首先通过二分迭代法快速搜索出水下声源所发出的定位声信号传播声线的初始掠射角,然后以该初始掠射角对应的唯一声线为基础,根据斯涅耳(Snell)声线折射定理计算得到声源与水下接收阵元的距离值,最终利用与声线相符的三路测距值进行交汇解算,完成实时声线修正定位。湖上试验结果表明,该算法简单易行、运算速度快,能够满足实时修正处理的要求,在复杂水文条件下提高了水声定位系统的定位精度。该算法具有良好的工程实用性和通用性,可推广应用于同类水声跟踪定位系统。     

X-ray Topography of Piezoelectric La/sub 3/Ta/sub 0.5/Ga/sub 5.5/O/sub 14/ Crystal Grown by Czochralski Method

We performed synchrotron X-ray topography on a La₃Ta_0.5Ga_5.5O₁₄ (LTG) crystal grown by the Czochralski method. Since a synchrotron X-ray source can provide high-energy X-rays, one can detect bulk structures by X-ray topography. LTG is one of the most attractive piezoelectric crystals along with La₃Ga₅SiO₁₄ (LGS) because of its excellent acoustic properties (temperature compensation of acoustic losses). Since LTG single crystals can be grown from a stoichiometric melt, it was expected that single crystals with better quality than the LGS crystal, which cannot be grown from a stoichiometric system but only from a congruent melt, can be obtained. However, 60 keV X-ray topography revealed that the LTG crystal quality was not as high as the LGS crystal quality. The crystal quality of the central region was lower than that of the surrounding region.     

Hall effect in polycrystalline semiconductors

A phenomenological theory of the Hall effect in polycrystalline semiconductors is elaborated which makes it possible to interpret reasonably the experimental results obtained from Hall effect measurements. The theory is based on the analysis of the Hall effect in the individual grains and intergrain domains forming the polycrystalline semiconductor. Explicit calculations of the expressions for the Hall constant, Hall scattering coefficient and Hall and conductivity mobilities are performed for wide-gap n-type semiconductors. It is shown that the models of Volger and of Berger are special limiting cases of the theory presented and that the model of Petritz can be extended to the problems of the Hall constant and the Hall mobility in a simple way.The expressions presented for the Hall constant, the Hall scattering coefficient and the Hall mobility represent generalized expressions from which the corresponding expressions for single-crystal semiconductors can be derived.     

Hall conductivity of a moving magnetic-field-induced spin-density wave

The influence of the motion of a magnetic-field-induced spin-density-wave (FISDW) on the quantum Hall effect in a quasi-one-dimensional conductor is studied theoretically. In the ideal case, when the pinning and the damping of the FISDW can be neglected, it is found that the counterflow of the FISDW precisely cancels the quantum Hall current, so that the resultant Hall conductivity is zero. In real systems, the Hall conductivity should vanish at the high frequencies where the dynamics of the FISDW is dominated by inertia, and the pinning and the damping can be neglected.This work was partially supported by the NSF Grant No. DMR 89-06958.