牙嵌式自由轮差速器消声环的设计与强度分析

消声环是牙嵌式自由轮差速器降噪减震的重要零部件。在差速器的工作过程中,主动环与从动环频繁的接合、分离容易导致消声环齿的断裂。消声环齿的强度是牙嵌式自由轮差速器设计过程中需要重点考虑的因素。本文根据牙嵌式自由轮差速器的结构与工作原理,对牙嵌式自由轮差速器消声环进行设计。通过Solidworks进行建模,并用Ansys Workbench进行仿真分析,对不同齿形及齿数的消声环强度进行计算,选择出合理的消声环齿形和齿数。

基于光纤环声发射的装甲车侧传动故障诊断

装甲车侧传动部件应用环境十分恶劣,传统的电传感器使用比较困难。利用光纤环声发射传感器检测某型装甲车侧传动齿轮在运行过程中的声发射信号,使用共振解调算法,找出运转过程中因异常的啮合冲击而产生的异常故障频率。实验设置了完好齿圈、齿圈齿面磨损2个齿圈作为对照,故障齿圈共振解调后的频谱图上能够检出故障频率,与完好齿圈形成区分。基于光纤环的装甲车侧传动故障频率检测,能够抗电磁干扰,附加质量小,能够适应齿轮箱复杂和恶劣的测量环境,具有一定的应用价值。

开口圆环类声子晶体传播禁带特性研究

为衰减中低频振动噪声,本文设计了一种非严格对称的开口圆环类声子晶体结构,基于有限元法和弹性波理论分析了其禁带特性和各方向的振动衰减性能;结合系统的振动模态解释了带隙打开和关闭的原因,并分析了几何参数对带隙宽度的影响规律。结果表明:由于晶体的非严格对称,仅ΓX方向的传输损耗和禁带特性吻合,且衰减性能优于MΓ方向,禁带内平均衰减27.8 dB,同比提升了5.5 dB。禁带内几乎没有产生位移变形量,而通带因无法抑制弹性波传播导致变形量显著增大;芯体的水平和旋转运动是带隙起始、截止的明显标志。以钨为芯体,能获得起始频率和带宽均为500 Hz的低频带隙,增大芯体的材料密度、填充率和晶格尺寸有助于获得较低频率的完整带隙。

河南省人民政府办公厅关于河南省2009年度城市环境综合整治定量考核结果的通报

豫政办[2010]64号各市、县人民政府,省人民政府有关部门:根据《河南省人民政府办公厅关于认真贯彻"十一五"城市环境综合整治定量考核指标实施细则和全国城市环境综合整治定量考核管理工作规定进一步加强我省城市环境综合整治工作的通知》(豫政办[2006]64号)和环境保护部的有关要求,各省辖市、县级市政府以城市环境综合整治定量考核为载体。

此Ring是“钟声”吗?——谈《新视野大学英语·教师用书》中的误译一例

《新视野大学英语.读写教程》第一册第八单元的课文中写到音乐家瓦格纳的一次创作过程,句中出现的"Ring"一词,在《教师用书》等参考书中被译为"钟声",是译者在未能准确了解其文化背景下作出的误译。其正确的译法实则为尼伯龙根的"指环"。

独山子炼油厂对生产装置岗位噪声的防治

近年来,该厂对生产装置岗位噪声的防治,由原来对机泵设备加设消声罩,转换为在机泵房内增设隔声室。隔声室的效果主要与其结构有关。本文列举了设计合理的隔声室的特点,对炼厂生产装置岗位的噪声防治有指导价值。

SPEECH ENHANCEMENT METHOD FOR LPC AUTOREGRESSIVE MODEL AND SYSTEM IMPLEMENTATION OF COMMAND WORD RECOGNITION USED IN NOISY ENVIRONMENT

At present, almost all the systems and products for speech recognition are working in quiet environment and their performances are degraded or even can′t work when they are operated in high noisy environment. In this paper, after analyzing the features of speech and noise, a speech enhancement method for LPC autoregressive model for command words recognition used in noisy environment is proposed, and an experimental system is realized. In different background noisy environments, we conduct experiments about SNR, basic accuracy, noise resistant ability and system environment adaptability with different microphones. The experimental results show that the system has good recognition performance in high noisy environments. The system can resist many kinds of noises and meet the needs of application areas on the whole such as military, traffic, marketplace and factory etc.

Research on Aircraft Noise Evaluation System

The evaluation system of aircraft noise and environment noise should be integrated, because aircraft noise belongs to environment noise. At the same time, there should be some difference in the evaluation system of aircraft noise. For solving this contradiction, this article puts forward a new evaluation system of aircraft noise. This new system unifies the evaluation of aircraft noise and other environment noise effectively, and adds a new evaluation index single event noise exposure level. The system not only considers the characteristics of aircraft noise, which is different from other traffic noise, but also adds aircraft noise to other traffic noise, which can reflect sound environment around airport really. This system has practical worthiness and theory significance.

Limit Properties of One Dimensional Periodic Hopping Model

One dimensional periodic hopping model is useful to understand the motion of microscopic particles in thermal noise environment. In this research, by formal calculation and based on detailed balance, the explicit expressions of the limits of mean velocity and diffusion constant of this model as the number of internal mechanochemical sates tend to infinity are obtained.These results will be helpful to understand the limit of the one dimensional hopping model.At the same time, the work can be used to get more useful results in continuous form from the corresponding ones obtained by discrete models.

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.

Acoustic pressure simulation and experiment design in seafloor mining environment

Since the suspended sediments have severe influence on acoustic radiated field of transducer, it is significant for sonar system to analyze the influence of suspended sediments on acoustic pressure in the seafloor mining environment. Based on the KZK （Khokhlov-Zabolotkaya-Kuznetsov） equation, the method of sound field analysis in turbid water is proposed. Firstly, based on the analysis of absorption in clean water and viscous absorption of suspended sediments, the sound attenuation coefficient as a function of frequency in the mining environment is calculated. Then, based on the solution of KZK equation in frequency domain, the axial sound pressure of transducer in clear water as well as turbid water is simulated using MATLAB. Simulation results show that the influence of the suspended sediments on the pressure of near field is negligible. With the increase of distance, the axial sound pressures of transducer decay rapidly. Suspended sediments seriously affect the pressure in far-field. To verify the validity of this numerical method, experiment is designed and the axial sound pressure of transducer with a frequency of 200 kHz and a beam width of 7.5~ is measured in simulated mining experiment. The results show that the simulation results agree well with the experiments, and the KZK equation can be used to calculate the sound field in turbid water.

Entanglement Dynamics of Two Qubits Coupled to a Noise Environment

We study the time evolution of two two-state systems （two qubits） initially in the pure entangled states or the maximally entangled mixed states interacting with the individual environmental noise. It is shown that due to environment noise, all quantum entangled states are very fragile and become a classical mixed state in a short-time limit. But the environment can affect entanglement in very different ways. The type of decoherence process for certain entangled states belongs to amplitude damping, while the others belong to dephasing decoherenee.

Epoxidation of Cyclohexene with Oxygen in Ultrasound Airlift Loop Reactor

Epoxidation of cyclohexene to cyclohexene oxide was studied in a new type reactor—the ultrasound airlift loop reactor. The influences of ultrasound intensity, molar ratio of isobutyraldehyde to cyclohexene and oxy-gen gas flow rate on the conversion of cyclohexene and selectivity of cyclohexene oxide were investigated and dis-cussed, and the optimal operation condition was found, under which 95.2% conversion of cyclohexene and 90.7% selectivity of cyclohexene oxide were achieved. The ultrasonic airlift loop reactor utilizes the synergistic effect of sonochemsitry and higher oxygen transfer rate. Possible reaction mechanisms were outlined and the reason of ul-trasound promotion of epoxidation reactionwas analyzed.

An Array Extension Method in a Noisy Environment

An array extension method in a noisy environment was proposed to improve angular resolution and array gain. The proposed method combines the FOC （fourth-order cumulants） technique with the ETAM （extended towed array measurements） method to extend array aperture and suppress Gaussian noise, First, successive measurements of a virtual uniform linear array were constructed by applying lburth-order cumulants to measurements of uniform linear array; Gaussian noise in these measurements was also eliminated. Then, the array was extended by compensating phase differences using the ETAM method, Finally, the synthetic aperture was extended further by the fourth-order cumulants technique. The proposed FOC-ETAM-FOC method not only improves angular resolution and array gain, but also effectively suppresses Gaussian noise. Furthermore, it inherits the advantages of the ETAM method. Simulation results showed that the FOC-ETAM-FOC method achieved better angular resolution and array gain than the ETAM method. Furthermore this method outperforms the ETAM method in Gaussian noise environment.

A Low Jitter Design of Ring Oscillators in 1.25GHz Serdes

A new configuration for delay cells used in voltage controlled oscillators is presented. A jitter comparison between the source-coupled differential delay cell and the proposed CMOS inverter based delay cell is given. A new method to optimize loop parameters based on low-jitter in PLL is also introduced. A low-jitter 1.25GHz Serdes is implemented in a 0.35μm standard 2P3M CMOS process. The result shows that the RJ （random jitter） RMS of 1.25GHz data rate series output is 2. 3ps （0. 0015UI） and RJ （1 sigma） is 0. 0035UI. A phase noise measurement shows - 120dBc/Hz@100kHz at 1111100000 clock-pattern data out.

VOICE ACTIVITY DETECTION UNDER RAYLEIGH DISTRIBUTION

This paper presents an improved Voice Activity Detection （VAD） algorithm which uses the Signal-to-Noise Ratio （SNR） measure. We assume that noise Power Spectral Density （PSD） in each spectral bin follows a Rayleigh distribution. Rayleigh distributions with its asymmetric tail characteristics give a better description of the noise PSD distribution than Gaussian distribution. Under this asstlmption, a new threshold updating expression is derived. Since the analytical integral of the false alarm probability, the threshold updating expression can be represented without the inverse complementary error function and low computational complexity is achieved in our system. Experimental results show that the proposed VAD outperforms or at least is comparable with the VAD scheme presented by Davis under several noise environments and has a lower computational complexity.

Roller Profile Online Measurement Based on Ultrasonic Circulation Pulse-echo Technology

In order to meet the high precision requirement of wide steel strip in industry field, a novel online measurement of roller profile based on sonic circulation and pulse-echo technology was introduced. All kinds of the factors influencing the accuracy of roller profile online measurement were analyzed in detail and error compensation analysis of system was accordingly presented. In order to reduce count error, field program gate array(FPGA) was introduced and a highprecision data acquisition system was designed based on digital phase-shift technology. Experiments indicate that the standard deviation of measure data was 7.27 μm, which showed the feasibility and validity of the proposed method, and realized the roll profile measurement with high precision.

A 5-GHz frequency synthesizer with constant bandwidth for low IF ZigBee transceiver applications

A fully integrated integer-N frequency synthesizer is implemented.The synthesizer is designed for low intermediate frequency （IF）ZigBee transceiver applications.Techniques used to make the loop bandwidth constant across the whole output frequency range of the voltage controlled oscillator（VCO）are adopted to maintain phase noise optimization and loop stability.In-phase and quadrature（IQ）signals are generated by a 1/2 frequency divider at the output of the VCO.The synthesizer is fabricated in 0.18 μm radio frequency（RF） complementary metal oxide semiconductor transistor （CMOS）technology.The chip area is 1.7 mm2.The synthesizer is measured on wafer.It consumes totally 28.8 mW excluding output buffers from a supply voltage of 1.8 V.The measured phase noise is -110 and -122 dBc/Hz at the offset of 1 and 3 MHz from a 2.405 GHz carrier,respectively.The measured reference spur at a 2 MHz offset from a 2.405 GHz carrier is-48.2 dBc.The measured setting time of the synthesizer is about 160 μs.