给定箱容积的扬声器频响范围的积分极值

文章以效率的频率加权积分形式导出低频扬声器性能的限值。这个结果是关于效率、截止频率及箱容积间协调关系的一个可供选择的表达式。     

On the communication complexity of zero-knowledge proofs

The fact that there are zero-knowledge proofs for all languages in NP (see [15], [6], and [5]) has, potentially, enormous implications to cryptography. For cryptographers, the issue is no longer “which languages in NP have zeroknowledge proofs” but rather “which languages in NP have practical zeroknowledge proofs.” Thus, the concrete complexity of zero-knowledge proofs for different languages must be established. In this paper we study the concrete complexity of the known general methods for constructing zero-knowledge proofs. We establish that circuit-based methods, which can be applied in either the GMR or the BCC model, have the potential of producing proofs which can be used in practice. Then we introduce several techniques which greatly reduce the concrete complexity of circuit-based proofs, and we show that these techniques lead to zero-knowledge proofs of knowledge. Finally, we show how to combine the techniques of Kilian, Micali, and Ostrovsky, for designing zero-knowledge proofs with only two envelopes, with some of our techniques for reducing the number of bits which the prover must commit to. Supported in part by NSA Grant No. MDA90488-H-2006. Supported in part by NSF Grant No. CCR-8909657.     

油底壳放油塞座焊接夹具设计和装配要点

根据油底壳放油塞座焊缝是环形焊缝特点,通过设计焊接夹具结构,由原来的人工转动焊枪焊接改为被焊接零件自动旋转焊接,焊接速度可提高2~3倍,焊缝质量显著提高,油底壳放油塞座焊缝漏油返修率由原来的0.5%,降为0.05%,效果明显,创造了很好的效益。焊接夹具结构装配时,必须保证放油塞座定位块中心与立式微型直流减速电动机旋转中心一致,这样才能保证焊接夹具在大批量生产时正常使用保证焊接质量和焊接速度。     

重介工艺在太原选煤厂的应用

太选重介工艺投入运行后，不能充分发挥其洗选优势，针对生产中存的问题，提出解决方案，最终使得重介工艺逐步完善，在太选的洗煤生产中发挥了极其重要的作用。     

空气滤清器的效率及发动机磨损的试验研究

对CA6102汽油机进行的强化快速加灰试验表明，发动机的磨损与空气滤清器的效率有很大的关系。通过严密的理论推导，得出了不同粉尘浓度条件下发动机的磨损与空气滤清器滤清效率的经验公式。根据此经验公式，不仅定性且可定量地从空气滤清器的角度来分析研究发动机的磨损，同时给出了典型路面条件下空气滤清效率的合理限值。此经验公式对研究发动机的磨损、设计及评价发动机空气滤清器，有一定的指导意义。     

YBCO超导薄膜侧馈H天线实验研究

利用ＹＢＣＯ／ＹＳＺ超导薄膜制做了侧馈的Ｈ天线，实验表明，与相同的银膜侧馈Ｈ天线相比，相对效率在ｘ极化方向上提高了９．３ｄＢ，在ｙ极化方向上提高了１３．６ｄＢ。     

同轴HPGe探测器的全能峰效率测量及效率曲线斜率的经验公式

采用~(60)Co和~(152)Eu放射源,测定了灵敏体积为31.6,118.0和221.0cm~8的同轴HPGe探测器的全能峰绝对效率与121.8—1408keV能区内γ射线的能量关系,并用最小二乘法对效率曲线进行了较好的拟合。在极大的灵敏体积范围内,验证了锗探测器效率曲线斜率与其灵敏体积关系的经验公式:S=alogV+b,采用本公式可在小于3％的相对误差范围内,对已知灵敏体积的同轴HPGe探测器的全能峰效率随γ射线能量的变化作出估价。     

A revised ideal model for AlGaAs/GaAs quantum well solar cells

Quantum well solar cells (QWSCs) are heterostructure devices intended to achieve higher efficiencies than conventional cells. This paper extends a previous model for QWSC current-voltage characteristics by revising the equations for the absorbed flux and by introducing expressions to calculate radiative recombination coefficients and well effective densities-of-states. This revised model is in agreement with previous experimental results for AlGaAs/GaAs. Since the revised model incorporates detailed balance calculations, its predictions are consistent with the efficiency restrictions of this theory. The revised model, however, does predict efficiency enhancements for QWSCs in some configurations if non-radiative recombination is dominant, even in such a poor QWSC material as AlGaAs/GaAs.     

Thermal rating and design of woodstoves: A new approach

The paper is divided into two parts. In the first part, the results of tests on 13 stoves currently being marketed in India, compared with two traditional stoves, are presented. The bulk of the tests (about 140) pertain to variation of efficiency against fuel burning rate. Also, a few tests on the variation of chimney heights (18 tests) and damper position (20 tests) were conducted. The levels of efficiency were quite low on account of improper dimensioning of the stoves. Except for two stoves, all recorded consistently low efficiency figures. In the second part of the paper, the results of tests on combustion chambers of different sizes, ranging from a diameter of 180 mm to 500 mm, are presented in the form of design equations. The optimum length to diameter ratio is about 0.35, and optimum height of the ash chamber is 0.2 times the height of combustion chamber. A new approach to the sizing of combustion chambers is presented.     

Fractional Aerosol Filtration Efficiency of In-Duct Ventilation Air Cleaners

The filtration efficiency of ventilation air cleaners is highly particle-size dependent over the 0.01 to 3 μm diameter size range. Current standardized test methods, which determine only overall efficiencies for ambient aerosol or other test aerosols, provide data of limited utility. Because particles in this range are respirable and can remain airborne for prolonged time periods, measurement of air cleaner fractional efficiency is required for application to indoor air quality issues. The objectives of this work have been to 1) develop a test apparatus and procedure to quantify the fractional filtration efficiency of air cleaners over the 0.01 to 3 μm diameter size range and 2) quantify the fractional efficiency of several induct air cleaners typical of those used in residential and office ventilation systems. Results show that efficiency is highly dependent on particle size, flow rate, and dust load present on the air cleaner. A minimum in efficiency was often observed in the 0.1 to 0.5 μm diameter size range. The presence of a dust load frequently increased an air cleaner's efficiency; however, some air cleaners showed little change or a decrease in efficiency with dust loading. The common furnace filter had fractional efficiency values of less than 10% over much of the measurement size range.