Methods for increasing noise suppression of digital averaging devices based on adaptation of weighting functions to signal frequency and phase

We present an analysis of noise suppression of averaging devices with rough adaptation of the width of the weighting functions to the period of the signal. We propose a method for increasing noise suppression, based on taking into account the phase of the signal.Translated from Izmeritel'naya Tekhnika, No. 10, pp. 55–58, October, 1995.     

Image restoration by transformation of signal-dependent noise to signal-independent noise

A transformation to convert signal-dependent noise corrupting an image to additive Gaussian signal-independent noise is derived in this paper. Wiener filtering techniques using a Markovian covariance model for the image signal are applied to the transformed data followed by an inverse transformation to restore the degraded image. An ad hoc technique using contrast manipulation to adaptively convert signal-dependent noise to signal-independent noise is also described. The results of the computer simulations designed to evaluate the performance of these techniques are also presented.     

Relevance of liquid state to solid state properties

We outline in this talk the beginning of a new programme to study physical properties of crystalline solids. It is based on considering the latter, a broken symmetry phase, in terms of the higher symmetry liquid phase. The solid is a calculable perturbation on the fluid. This is exactly opposite to the standard approach which relates mechanical properties to the behaviour of defects (mainly dislocations) etc., in an otherwise perfect crystalline solid. However, most other broken symmetry phases (e.g. ferromagnets) are discussed starting from a symmetric Hamiltonian or a free energy functional, and earlier work by one of the authors shows that the liquid-solid transition is well described, qualitatively and quantitatively, by this approach. On the other hand, defect theories of melting have a long record of nonsuccess. In the first part of the talk, the density wave theory of freezing will be outlined, and it will be shown how properties such as Debye Waller factor, entropy change of freezing etc. can be calculated with no or one free parameter. The problem of calculating shear elastic constants and dislocation core structures as well as energies in terms only of observable liquid state properties will be set up, and results presented. The method will be contrasted with zero temperature ‘atomistic’ models which obscure the essential dependence on structure and flounder in a mass of detail. The concluding part will describe further proposed applications, some suggestive experimental results extant in the literature, and some speculations. Only a summary is presented.     

设置高架路声屏障降低城区交通噪声

针对城市交通噪声的声学特性 ,根据建筑声学原理 ,从噪声源控制、传播途径控制和接收者防护三个方面 ,阐述在高架路上设置隔声屏障的必要性及技术手段 ,并通过实例具体说明运算方法、设计要求和注意事项     

Experimental investigation of the evolution of probability distribution in self-sustained oscillators with additive noise

The breakage of a probability distribution characteristic of noise-modulated self-sustained oscillations in nonlinear oscillators with one or one-and-a-half degrees of freedom has been experimentally studied as dependent on the increasing intensity of additive noise.     

离心泵作透平流体诱发外场噪声特性及贡献分析

以某离心泵作透平为研究对象,对流体诱发的外场噪声特性进行了数值计算和试验研究。在典型流量下,采用雷诺时均方法获取壁面偶极子声源,并利用FEM/AML方法求解出叶轮和壳体偶极子源作用的流动噪声,基于声振耦合法计算出流体激励结构振动产生的外场流激噪声,分析不同性质噪声源的频谱特性,同时评估外场声源在各个频段下的贡献量。借助模态试验对透平壳体结构的模态参数进行了识别。结果表明,计算与试验振型近似,固有频率平均相对误差小于4.60%。结构的影响使得外场五阶叶频处声压最高,二阶叶频处次之。壳体偶极子作用的流激噪声对外场噪声的贡献最大,其次是壳体偶极子作用的流动噪声,叶轮偶极子作用的流激噪声对外场噪声贡献最小。研究结果为低噪声叶轮机械设计提供了一定的参考。     

一种计算航船对近海海洋环境噪声贡献的算法

为了研究浅海中低频段的海洋环境噪声,文章构建了一种计算航船对近海海洋环境噪声贡献的算法,利用某海域航船信息,结合实际水文参数,对该海域的航运噪声进行了仿真计算。航船信息通过访问船舶自动识别系统数据库获取。主要关注50~400 Hz的中低频段,将仿真计算结果和实验数据进行对比,验证了算法的可靠性,并进行了误差分析。利用该算法可获取接收点处航船噪声的水平方向分布特点,并可初步定量分析航船噪声对海洋环境噪声的贡献。     

变流器气动噪声分析与噪声控制研究

为控制某型号变流器噪声,文章对该变流器产品开展柜体内气动噪声仿真研究,并与试验结果对标,验证仿真方法可靠性,并协助进一步诊断噪声问题。仿真研究结果表明:机柜内部气动噪声源主要集中在风机附近区域,由风机叶片旋转引起的离散声源。风机噪声频谱在叶片通过频率及其他谐频出现明显峰值。文中对不同降噪方案进行仿真分析,对比了不同材料及不同厚度方案的降噪效果,并通过试验进行了验证。结果表明,使用吸声材料方案使出口总声压级降低 12.2 dB(A)。仿真分析法的降噪优化量与试验结果相近,该方法可应用于后续新产品的降噪设计。     

Relevance of free-surface temperature to thermal and kinetic factors in melt spinning

The relationship between the free-surface temperature history and the thermal and kinetic factors involved in melt spinning has been examined using a thermokinetic model for rapid solidification. Results show that the relationship is quite substantial. Measurement of the free surface temperature history can lead to the estimation of some of the factors involved which are otherwise very difficult to measure. Once these factors are determined, the real situation in rapid solidification can be modelled.Nomenclature A Pre-exponential coefficient for the nucleation rate expression - C _p Specifie heat with C ₁ and C _s representing that for liquid and solid, respectively - D The pre-basial constant for the crystal growth kinetic model - The thickness of the solidifying slab - G ^* Activation barrier for homogeneous nucleation - G Gibbs free energy change for an atom jumping from liquid to solid - Atomic jump frequency - h Heat transfer coefficient - I Nucleation rate with I _s and I _t representing the steady state and transient nucleation rate, respectively - k Boltzmann's constant - K Heat conduction coefficient with K ₁ and K _s representing that for liquid and solid, respectively - L Latent heat - n The power index of the crystal growth kinetic model - N ^* Number of atoms in the critical nucleus - Density of the material with ₁ and _s representing that for liquid and solid, respectively - t Time coordinate - T ₁ Initial temperature of the cooling substrate - T ₂ Initial liquid temperature - T _I Interface temperature - T _m Melting point - T _n Nucleation temperature - T Undercooling: T=T _m-T _I - t _s The time at the onset of solidification - V Interface velocity - x Space coordinate     

Correction to the noise temperature of a waveguide thermal noise generator due to nonuniform heating of the channel

The correction to the noise temperature of waveguide thermal noise generators due to nonuniformity of the heating of the waveguide line is considered. It is shown that, for a simplified model of a thermal noise generator, the minimum values of the corrections in a copper waveguide with dimensions of 2.4×1.2 mm and a waveguide of stainless steel with dimensions of 3.6×1.8 mm amount to 0.05 K and 0.15 K respectively, for a length of the nonuniformly heated part of the waveguide line of 80 mm. Translated from Izmeritel'naya Tekhnika No. 5, pp. 46–49, May, 1998.     

Robustness of homodyne tomography to phase-insensitive noise

Abstract

We study the effects of phase-insensitive noise on homodyne measurements of a radiation density matrix. We prove that this noise has an effect equivalent to a non-unit quantum efficiency at detectors. The overall effective quantum efficiency η_? of the measurement is evaluated in terms of the quantum efficiency at detectors and of the average number of noise photons added to the radiation field. For pure Gaussian-displacement noise, we show that half a photon of noise is enough to prevent the homodyne measurement of the density matrix.     

On the Relevance of Mean Field to Continuum Damage Mechanics

Damage theory is, by its very essence, a mean-field theory. In this note, we argue that considering the effective interaction kernel between an additional micro-crack, and the effective equivalent damaged matrix, the power-law decay of the influence function (or Green's function) becomes more and more long-ranged as the tangent modulus vanishes. Moreover, the reloaded region becomes a narrower and narrower `cone', so that the damage in this cone becomes closer and closer to the so-called global load sharing rule used, for instance, to study a fiber bundle. This constitutes a formal justification of the relevance of such a mean-field approach as the peak stress is approached.     

Application of the moment condition to noise simulation and to stability analysis

It is well-known that low frequency noises (flicker FM and random walk FM) are not stationary; it is not possible to define either the mean value or the (true) variance. Therefore, the use of a stationary approach yields convergence problems unless a low cut-off frequency is introduced, the physical meaning of which is not clear. The moment condition explains the link between insensitivity to drifts and convergence for low frequency noises in a stationary approach. This condition may be summarized by the following consideration: the divergence effect of a low frequency noise for the lowest frequencies induces a false drift with random drift coefficients; the lower the low cut-off frequency, the higher the variance of the coefficients of this drift. These variances may be known by theoretical calculations. The order of the drift is directly linked to the power law of the noise. The moment condition is demonstrated and applied for creating new estimators (new variances) and for simulating low frequency noises with a very low cut-off frequency.     

Measurement of magnetostriction and vibration with regard to transformer noise

A simple technique of measuring the dynamic magnetostriction in silicon-iron using displacement transducers is discussed. The importance of stress and harmonics of magnetostriction is shown by considering the effects of improving the stress sensitivity of steel and reducing core vibration by a suitable bonding technique which can also reduce transformer noise.     

Structure dynamics control approach to supply chain planning and adaptation

Many of the existing methods and models of supply chain planning and control consider only one supply chain structure and assume it's more or less static in nature. In practice, supply chains have a multi-structural semantics and those multiple interrelated structures (organisational, functional, informational, financial, topological, technological, product, and energy structures) are dynamic and subject to many planned and disturbance-based changes. These changes are tackled by control activities which make planning an adaptive process. Although the supply chain optimal planning domain for static structures has been extensively investigated, the domain of planning and control of supply chains with structure dynamics merits more systematic and critical attention. In this study, an original form of supply chain representation as a dynamic system with changing multi-structural characteristics is developed. The structure dynamics control is a dynamic interpretation of the supply chain (re)synthesis process and aims at both advancing the supply chain (re)planning domain and enlarging the scope of the supply chain analysis domain that is currently rather limited. The developed approach is based on an optimal program control theory, active modelling objects, and structural–mathematical concept blended with mathematical programming. In this paper, we describe its basic features and exemplify possible applications and extensions regarding real planning and control problems faced by international supply chains in recent years.     

Explicit and implicit processes in behavioural adaptation to road width

The finding that drivers may react to safety interventions in a way that is contrary to what was intended is the phenomenon of behavioural adaptation. This phenomenon has been demonstrated across various safety interventions and has serious implications for road safety programs the world over. The present research used a driving simulator to assess behavioural adaptation in drivers' speed and lateral displacement in response to manipulations of road width. Of interest was whether behavioural adaptation would occur and whether we could determine whether it was the result of explicit, conscious decisions or implicit perceptual processes. The results supported an implicit, zero perceived risk model of behavioural adaptation with reduced speeds on a narrowed road accompanied by increased ratings of risk and a marked inability of the participants to identify that any change in road width had occurred.     

Rigor and Relevance of IJV Exit Research

• International Joint Ventures (IJVs) are a well acknowledged and frequently implemented organizational mode, especially with regard to international market entry strategies, yet they are also prone to conflicts of interests, drawbacks, inefficiencies, and enduring losses. Past research has consequently been dominated by studies that have attempted to identify success factors for managing IJVs based mainly upon archive data. Success or failure is frequently defined on the basis that IJVs have ‘disappeared’ from the data-set. The term IJV-‘exit’ has become the byword for closing down ineffective, failing IJVs while neglecting the fact that such a disappearance may indicate success if, for instance, the initial objectives of partners have been achieved.
• Beyond such misconceptions, there is no stock-take of what is known about the different types, measures, contexts, and determinants of IJV exit to take research to the next stage. This paper fills this research gap by comprehensively analyzing the IJV exit literature as an integral part of IJV research, while focusing on studies that either apply IJV termination or IJV longevity as a measure of IJV exit. A systematic overview of the contexts and determinants that influence IJV exit is provided. Furthermore, the rigor and relevance of the existing IJV exit literature is evaluated in terms of its methodological, conceptual and theoretical foundation, and major implications for directing future research are proposed.