柴油发电机组噪声控制研究

柴油发电机组噪声强,发热量大。针对此,采用隔声、吸声、消声、通风散热等具体措施。实践证明：方案设计合理,达到了预期的降噪效果,符合工业企业噪声排放标准。     

滚筒洗衣机噪声分析

本文具体针对全自动滚筒洗衣机,研究其在脱水状态下以每分钟1200转运转时所产生噪声的成因,接着提出三个改进方案,然后重新研究改进方案产生的噪声大小,以此验证改进方案的有效性。本文采用CFD软件FLUENT对所有模型进行模拟仿真分析。因为是搅拌模型,所以具体计算时采用动参考系法(MRF)进行计算。通过研究发现加强筋结构会造成涡流气流,是导致噪声问题的主要成因。在各个改进方案中,填充外围第四和第五圈栅格的方案被验证为最佳方案,既起到减噪效果又能节省填充材料。     

变速器异响故障分析

对微型发动机的变速器异响故障的现象进行了分析,对主要影响因素进行了研究。通过采取措施降低了变速器异响故障率。     

浅谈齿轮产生噪声的因素

阐述了齿轮在现代工业生产中的优缺点。论述了齿轮传动过程中产生的噪声不仅受载荷变化、动力装置等外在因素的影响,而是由齿形精度、齿轮啮合刚性的周期变化、齿轮传动误差、安装误差、材料、结构及润滑等因素决定的。     

NLMS算法在有源降噪系统中的应用

本文分析了自适应算法的原理,研究了最小均方（LMS）算法和归一化最小均方（NLMS）算法的区别,给出了有源噪声控制的仿真系统,并进行了仿真实验,在输入信号变化较大时,NLMS算法也能够维持稳定,并比LMS的收敛速度快.     

Direction-Based Adaptive Switching Filter for Removing High-Density Impulse Noise

A direction-based adaptive switching(DBAS) filter is presented for the removal of high-density impulse noise in images. The extrema detection and 28-directional detection are employed to discriminate the pixels as noisy or noise-free. If a pixel is classified as noisy, it will be replaced by a median or a mean value within an adaptive filter window with respect to different noise densities. Simulation results show that the miss-detection ratio and false-alarm ratio are both very low even at noise level as high as 90%. At the same time, better results are obtained in terms of the qualitative and quantitative measures. The peak signal-to-noise ratios increase by nearly 1 dB compared with other existing algorithms. In addition, the computation time is around 10 s for test images with resolutions of 512×512since the proposed approach has low complexity.     

Analysis,design and implementation of SiGe wideband dual-feedback low noise amplifier

A wideband dual-feedback low noise amplifier(LNA) was analyzed, designed and implemented using SiGe heterojunction bipolar transistor(HBT) technology. The design analysis in terms of gain, input and output matching, noise and poles for the amplifier was presented in detail. The area of the complete chip die, including bonding pads and seal ring, was 655 μm×495 μm. The on-wafer measurements on the fabricated wideband LNA sample demonstrated good performance: a small-signal power gain of 33 dB with 3-dB bandwidth at 3.3 GHz was achieved;the input and output return losses were better than-10 dB from 100 MHz to 4 GHz and to 6 GHz, respectively; the noise figure was lower than 4.25 dB from 100 MHz to 6 GHz; with a 5 V supply, the values of OP1 dB and OIP3 were1.7 dBm and 11 dBm at 3-dB bandwidth, respectively.     

Matlab仿真在舰艇水下辐射噪声数值预报教学中的应用

搭建一种基于Matlab仿真的多极子声源和螺旋桨辐射噪声动态可视化教学演示平台。该平台能够动态显示单个和多个多极子声源辐射声场、墙面反射下的多极源辐射声场、有限长导管中的多极源辐射声场、螺旋桨促动盘辐射声场、真实螺旋桨脉动力源辐射声场及其线谱谱级值,是舰艇水下辐射噪声四大类噪声源数值分析平台之一。借助该平台,研究生学员可以直观、动态地了解简单和复杂声源的辐射噪声空间分布特征及其声波的传播规律,并能直接分析不同声源参数对辐射声场的影响作用。教学实践表明,该平台可以有效弥补动力工程专业学员噪声背景知识较少的不足,加深了学员对舰艇水下辐射噪声的理解,也调动了学员借助专业噪声分析软件预报方案设计阶段舰艇水下辐射噪声性能的积极性,为进一步深入研究低噪声舰艇设计奠定了基础。     

西安市农村人口城镇化的环境噪声评价研究

在模糊数学理论下,设计了噪声的模糊综合评价法.根据最大隶属度原则,建立模糊矩阵,对西安市环境噪声的监测数据进行分析模拟,并与实际监测值进行比对,具有较高的一致性,同时分析了西安市农村人口逐步城镇化后,环境噪声污染的原因、现状及特征.根据城市噪声环境区域划分及计算分析得知,0,1区域噪声污染将加重,而2,3,4区域噪声污染明显减轻.     

探析压控振荡器研究现状与原理

压控振荡器是频率综合器最为重要的组成部分,振荡器性能的好坏直接决定了频率综合器的性能。本文介绍了压控振荡器研究现状,压控振荡器电路的基本原理。