剧场室内声学缺陷的改善措施研究与应用

室内声环境作为剧场室内环境质量的重要指标之一,对剧场的实际使用效果和品质起到了关键性作用,受到了越来越多的关注。以具体项目为例,通过对剧场平面、立面及侧墙进行二维声线分析及体形优化设计,分析建筑的声学缺陷来源,提出改善措施,并通过声学仿真模拟验证体形优化设计的效果。可为形体规则的室内剧场提供音质设计方法,并为类似音质问题提供解决思路。

流线型多功能厅室内音质设计研究

随着流线型多功能厅的体量增加,其室内音质效果越来越受到关注。以具体项目为例,在建筑体形流线已经固定的情况下,通过对多功能厅内装饰界面进行二维声线分析及界面优化设计,分析建筑的声学缺陷来源,提出改善措施,并通过声学仿真模拟验证装饰界面优化设计的效果。通过研究,可为流线型多功能厅的室内音质设计提供方法。

A New Low Voltage RF CMOS Mixer Design

A new architecture of CMOS low voltage downconve rsion mixer is presented.With 1.452GHz LO input and 1.45GHz RF input,simulation results show that the conversion gain is 15dB,IIP3 is -4.5dBm,NF is 17dB,the maximum transient power dissipation is 9.3mW,and DC power dissipation is 9.2mW.The mixer’s noise and linearity analyses are also presented.

海口湾演艺中心剧场的声学改造设计

介绍海口湾演艺中心剧场的声学改造设计,重点阐述体型的优化、声学相关室内用材的选用及布置,竣工测试结果表明满足声学设计要求。

A Cross-Reference Method for Nonlinear Time Series Analysis in Semi-Blind Case

In this paper, we propose a cross reference method for nonlinear time series analyzing in semi blind case, that is, the dynamic equations modeling the time series are known but the corresponding parameters are not. The tasks of noise reduction and parameter estimation which were fulfilled separately before are combined iteratively. With the positive interaction between the two processing modules, the method is somewhat superior. Some prior work can be viewed as special cases of this general framework. The simulations for noise reduction and parameter estimation of contaminated chaotic time series show improved performance of our method compared with previous work.

Design and optimization of vector coil sensor suited to magnetometric resistivity method

Magnetometric resistivity(MMR)method is a new way to detect dam leakage.The coil sensor is generally used to collect data in geophysical exploration methods.Given the characteristics of accurate vector data requirements and high sensitivity requirement,a three-component MMR air-core coil sensor is designed.Through the analysis of sensor sensitivity and coil structure parameters,the coil structure and turn number are designed.By analyzing the noise source of the sensor,a suitable amplifier is selected to reduce the background noise of the system.Through the analysis of the three-component non-orthogonal angles,the parameters of the non-orthogonal angles of the coils are corrected.Finally,a three-component MMR induction magnetic field sensor is designed.The volume of the sensor is controlled at 0.027 m 3.The background noise of X、Y and Z are 5.030435 nV/Hz@380 Hz and magnetic field sensitivities are 0.18995 pT/Hz@380 Hz.The three channels have good consistency,and the three-component nonorthogonal angles correction error of three components is controlled within 0.2%.

Analysis of SNR for Acoustic Vector Sensor Linear Array in Volume and Surface-generated Noise Fields

Acoustic vector sensor consists of pressure and particle velocity sensors,which measure the three-dimensional acoustic particle velocity,as well as the pressure at one location at the same time.By preserving the amplitude and phase information of the pressure and particle velocity,they possess a number of advantages over traditional scalar sensors.Signal-to-noise ratio (SNR) gain (which is often called array gain) is one of such advantages and is always interested by all of us.But it is not unchangeable if the spatial correlation of the noise field varies.Much more important,it is difficult to be given if the noise becomes complex.In this paper,spatial correlation of the vector field of isotropic volume-noise and surface-generated noise has been introduced briefly.Based on the results,the combined SNR output of a vector linear array is investigated and the maximum gain is given in the specified noise.Computer simulation shows that the output of one array in the same noise is not the same in different gestures.And then we find the best gesture through SNR calculation and obtain the biggest gain,which has important meaning to guide how to deploy an array in practice.We also should use the array with respect to the characteristics of the real ambient noise,especially in anisotropic noise field.

Optimal design of butterfly-shaped linear ultrasonic motor using finite element method and response surface methodology

A new method for optimizing a butterfly-shaped linear ultrasonic motor was proposed to maximize its mechanical output. The finite element analysis technology and response surface methodology were combined together to realize the optimal design of the butterfly-shaped linear ultrasonic motor. First, the operation principle of the motor was introduced. Second, the finite element parameterized model of the stator of the motor was built using ANSYS parametric design language and some structure parameters of the stator were selected as design variables. Third, the sample points were selected in design variable space using latin hypercube Design. Through modal analysis and harmonic response analysis of the stator based on these sample points, the target responses were obtained. These sample points and response values were combined together to build a response surface model. Finally, the simplex method was used to find the optimal solution. The experimental results showed that many aspects of the design requirements of the butterfly-shaped linear ultrasonic motor have been fulfilled. The prototype motor fabricated based on the optimal design result exhibited considerably high dynamic performance, such as no-load speed of 873 ram/s, maximal thrust of 27.5 N, maximal efficiency of 43%, and thrust-weight ratio of 45.8.

Resistin might not be a risk factor for carotid artery atherosclerosis in elderly Chinese males

Objective To investigate the correlation between the serum resistin level and carotid artery atherosclerosis in elderly Chinese males. Methods The study enrolled 235 elderly Chinese males [median age 76 （range 60-97） years] scheduled for ultrasound examination of carotid artery plaque and determination of carotid artery intima-media thickness （CIMT）. They were divided into carotid atherosclerotic plaque （CAP） and carotid atherosclerotic plaque-free （CAP-free） groups according to the ultrasound results. Their clinical profiles were col-lected, and the serum resistin and other blood biochemistry levels were determined.Results The CAP group was older and had a thicker mean CIMT than the CAP-free group. However, there was no difference in the serum resistin level between the groups. CIMT was positively correlated with age （r = 0.299,P〈 0.001）. The serum resistin level was not correlated with CIMT, even after controlling for age. Multiple linear regression analysis revealed that age （β = 0.001,P〈 0.001） and body mass index （β = 0.002,P= 0.015） were significantly and posi-tively correlated with the mean CIMT. Only age [odds ratio （OR）： 1.159; 95% confidence interval （CI）： 1.078-1.183,P〈 0.001] was associ-ated with the presence of carotid artery atherosclerotic plaque. The serum resistin level was not correlated with the mean CIMT or associated with the presence of carotid artery atherosclerotic plaque.Conclusion The results suggest that resistin might not be a risk factor for atherosclerosis in elderly Chinese males.

High Efficiency Stereo Audio Compression Method Using Polar Coordinate Principle Component Analysis for Wireless Communications

High efficiency audio compression is the basic technology in audio involved multimedia communications. Downmixing and parametric coding is efficient coding scheme with wide applications in some up-to-date audio codecs such as Parametric Stereo (PS) in EAAC+ and MPEG-Surround. Principle Component Analysis (PCA) stereo coding followed this idea to map two channels to one channel with maximum energy and parameterize the secondary channel. This paper investigates the conventional PCA method performance under general stereo model with multiple sound sources and different directions, and then proposes a Polar Coordinate based PCA (PC-PCA) stereo coding method. It has been proved that when multiple sound sources exist with different directions, PC-PCA is better than the conventional PCA method when Mean to Standard deviation Ratio (MSR) is large. A stereo codec based on PC-PCA is proposed to validate the performance improvement of proposed method. Objective and subjective tests show the proposed method achieves a comparative quality and saves 50% parameter bit rate comparing with conventional PCA method, and obtains a 4-8 MUSHRA scores improvement comparing with state-of-the-art stereo codec at the same parameter bit rate.

Preparation and characterization of Al/B/Fe_2O_3 nanothermites

A sol-gel synthetic approach combined with an ultrasonic method was utilized to prepare Al/B/Fe2O3 nanothermites.The structure and properties of the prepared nanothermites were characterized by thermogravimetric analysis,differential scanning calorimetry,scanning electron microscopy,X-ray diffraction,and an impact sensitivity test.The results verified that the nano-aluminum and the micro-boron were uniformly dispersed in the pores of the iron oxide gel.The heat of the prepared Al/B/Fe2O3 nanothermites was 1.3 times that of the simple physically mixed sample.In addition,the heat of the combustion test showed that these materials were indeed energetic.Small-scale safe experiments also showed that the prepared materials through sol-gel were relatively insensitive to standard impact.