中国弹弦乐器柳琴的声功率级测试

柳琴是民乐队中重要的弹奏乐器之一.介绍了在混响室内对4弦29品柳琴声功率级的测量研究工作.两位资深乐师用各自的柳琴在混响室中分别以pp、mp、f和ff 4种力度演奏3个代表性的单音g、d2与g3以及音阶和乐曲.采用4个通道同步测试技术,测量柳琴分别演奏上述内容时混响室内4个传声器位置处的1/3倍频带声压级,通过平均和计算,获得柳琴在不同演奏力度下演奏不同内容时的典型平均声功率级和动态范围.考虑到与人主观听音感受的关系,建议采用柳琴在f力度下演奏音阶时的平均声功率级作为其声功率级的代表数值.     

中国传统弹奏乐器扬琴的声功率测试

扬琴是具有悠久历史的中国弹奏乐器,在民族乐队中占有重要的位置.但是迄今为止,其声功率级尚未予以测定.文中介绍了在混响室内采用多通道测试技术测量扬琴声功率及其动态范围的方法,获得了扬琴在不同演奏力度下演奏单音、音阶和乐曲时的典型声功率数值.文中建议扬琴的声功率用其以f力度演奏音阶时所辐射的声功率及其频谱来标识,扬琴声功率的动态范围用其以不同力度演奏音阶时所辐射的声功率的动态范围来标识.     

声强法在电动机噪声测试中的应用

分析了声强测量的特点、优点和有关声强测量的基本原理,并与通常的声压测量进行了比较.研究了基于双通道FFT分析仪的虚拟式声强测量系统的原理与组成.分别采用声强法和声压法对电动机辐射空气噪声声功率进行了测定.结果表明,采用声强测量技术对电机噪声进行测量分析,能够在工业现场准确地评价电机噪声声功率级,克服了传统的采用声压法测量易受环境影响而要进行数值修正的问题以及声功率测量必须在特定声学环境里测量的问题.该方法在噪声测量中有一定的优越性.     

关于纺织机械噪声评价标准的探讨

机器噪声的污染问题,日益受到世界各国的重视和关注,现在国际上对机器噪声的测量,主要采用声功率级。但用这种声功率级的评价指标尚有某些不足之处,本文拟在声功率级基础上,提出“机器噪声相对声功率系数”的概念,作为评价、比较、改进机器噪声及综合质量的补充指标,以弥补声功率级的不足。     

利用声场指数确定机床辐射声功率级测量精度的实验研究

文章对声强测量中的声场指数和有关判据进行了阐述，以Ｃ６１６Ａ－１型精密车床为对象，选择三种不同的测量条件进行了声功率级的测定．结果分析表明：采用双传声器互谱声强法测量噪声源声功率时，只要按照ＩＳＯ９６１４－１中规定的判据进一行测量，就可以达到预期精度的结果，同时还可以优化测量条件．     

透镜式聚焦压电换能器超声功率测试分析

从声学原理出发推导了作用于锥面反射靶的超声功率和辐射压力之间的关系,在此基础上设计了一种新型超声功率计,该超声功率计采用反射靶加吸收靶的结构形式,避免了反射声束之间的相互干扰.用校正螺母对该功率计进行了校准和误差分析,并采用3个不同角度的反射靶对该声功率计进行了验证.理论分析和实验表明:在0~200W的测量范围内,采用3个不同角度的反射靶测量结果基本吻合,最大相对误差为10%左右;被测量的透镜式聚焦压电换能器的电功率、声功率随着驱动电压的升高而增大,且声功率增加逐渐变缓,呈一定的非线性.     

造型机声功率级与测量方法

用声压级作为造型机的测试标准,仪器简单方便易行,但受环境影响较大。而声功率级则不受环境影响,在各种环境中几乎都是个不变量,故声功率级可以对不同机器发射的噪声进行比较,以采取不同的控噪措施。声功率级的测量,应在理想的环境中进行,但目前我国一般机器制造厂尚无此条件。我们参照IS03744～IS03746,在车间现场进行测量、并按规定的方法,对测量结果加以适当修正。我们在测量实践中,系统地分析了影响测量的因素,提出了措施建议。     

琵琶演奏中的美学要求

琵琶演奏具有独特的美学效果,演奏时需做到点与线、线与点的完美结合;需表现出音韵美,还要展现出形神兼备的表演状态。笔者通过四个方面进行阐述,探讨了琵琶演奏中独特的美学要求,亦表现了琵琶这种乐器在演奏艺术上独特的音乐与文化价值。     

通过测量组织体模瞬时温升描述HIFU声场特征

 针对高声压下高强度聚焦超声（High Intensity Focused Ultrsound,HIFU）声场测量难题,提出通过测量组织体模中瞬时温升来描述HIFU声场特征的方法。采用水听器测量声功率为5W的HIFU声场分布;采用热电偶测量声功率为40、70、100、150、200W,辐照时间1s下HIFU作用于组织体模时的焦域温场分布,由瞬时温升■与■αi p2i 成正相关关系,得到在考虑声吸收系数改变和非线性条件下HIFU声场分布特征。结果显示,水听器测量得到的HIFU焦域径向-6dB宽度和轴向-6dB宽度,远小于通过热电偶检测得到的不同高功率下HIFU焦域径向和轴向大小;高功率下,随声功率增加,焦域径向-6dB宽度、轴向-6dB宽度逐渐增大,且温场分布图的峰值部分较尖,反映出能量比较集中。用热电偶测量组织体模焦域瞬时温升,能反映在考虑声吸收系数改变和非线性条件下HIFU声场分布特征。     

扫描声强法测量四极子声源声功率时参数确定

以四极子声源为例,建立了以矩形测量面锯齿形为扫描路径扫描声强法测量机器声功率的误差函数的数学模型,分析了声功率测量时矩形测量面大小、扫描测量面到声源的距离、扫描线密度误差的影响.根据声功率测量误差仿真曲线,给出了测量机器声功率时矩形测量面尺寸、测量面距声源距离、扫描线密度的确定方法.依此方法确定矩形测量面几何参数,提高了测量效率,为快速准确地测量声源的声功率奠定了基础.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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