地网对垂直偶极子天线辐射特性的影响

研究地网对垂直偶板子天线辐射特性的影响。建立了该天线的仿真模型，采用基于矩量法的仿真软件计算了铺设地网后垂直偶板子天线增益、输入阻抗、最大辐射仰角、3dB波瓣宽度等辐射特性。结果表明，地网中心偏离天线振子正下方0．75λ时能显著提高天线的增益，改变地网大小和铺设密度也能在一定程度上提高天线的增益。     

Influence of the rheological properties on the steel fibre distribution and orientation in self-compacting concrete

The interest in potential applications produced with self-compacting fibre reinforced concrete continues to grow, but in practice, problems associated with an uneven distribution and orientation of fibres in the concrete structure occur. It is not clear what exactly influences uneven distribution of fibres in self-compacting concrete (SCC) mixtures, especially during the casting and how different factors influence fibre orientation. The objective of this work was to investigate how rheological properties influence the steel fibre distribution in self-compacting concrete. This work also focuses on the investigation of steel fibre spatial orientation dependence on rheological properties of SCC, while keeping other casting parameters and the proportions of mixture components constant. Mixtures with three different rheological properties were chosen based on slump flow, slump flow time t₅₀₀ and static segregation values. The steel fibre orientation, volumetric concentration and spatial distribution values were determined in separate beam sections using three different non-destructive testing methods: electromagnetic induction, image analysis and computed tomography (CT scan). The comparison of the results is presented. The results show how different rheological properties of SCC affect the steel fibre orientation and distribution for the case of beams produced with the flow-induced casting method.     

噪声对心血管功能的影响

文章从实验研究、流行病学调查以及应激反应的理论等方面对噪声引起的心血管功能变化进行了简要的回顾与讨论。对动物和人的研究表明，在长期噪声暴露条件下产生了心、脑血管的功能调节障碍，出现脑血管和冠状血管收缩、脑的血流量减少和心肌缺血。噪声作为一种应激源还会引起各种与应激有关的激素增高，从而出现一系列全身反应，特别是心血管系统的反应。根据流行病学调查资料，获得了具有说服力的证据，在长期噪声曝露的人群中，心血管疾病的发病率均明显升高（包括高血压、心律不齐、心肮缺血、病理性心脏变形及眼底血管硬化等）。以上研究提示，噪声与心血管疾病的发生具有因果关系。     

Influence of colored noise on particle combustion

The influence of external noise with nonzero correlation time (colored noise) on the combustion of a single particle is investigated. An equation for the steady-state thermal regimes of the reaction is derived. Spontaneous ignition of a particle is considered.A. M. Gor'kii Ural State University, Ekaterinburg. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 63, No. 2, pp. 60, August, 1992.     

Influence of orientation of bar on its mass

The influence of vertical gradients of gravity, air density and temperature, magnetic induction, as well as air convection on the measured mass of an extended specimen is theoretically estimated. An experiment designed to compare the mass of a vertically oriented nonmagnetic titanium bar to the same bar when oriented in the horizontal plane is described. Possible factors responsible for the discrepancy between the experimental results obtained and the theoretical estimates presented are discussed. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 22–24, May, 1998.     

Influence of uniaxial elastic stress on power spectrum and pulseheight distribution of surface Barkhausen noise in pipeline steel

Barkhausen noise (BN) measurements were made on a half-section of a pipe under tensile and compressive isostress. The RMS BN voltage was found to increase with increasing tensile stress and to decrease with increasing compressive stress. Pulse-height distribution analysis and power density spectral analyses were performed on the BN data. These analyses revealed that the BN events with large amplitudes occur in the presence of tensile stress, while events with small amplitude occur under compressive stress. The power of the BN spectrum increased or decreased, respectively, with increasing tension and compression. While the exact mechanism responsible for the shift in BN pulse height distribution is not yet clear, the authors suggest that it may be related to stress-induced changes in domain size, magnetization distribution, and/or the clustering behavior of domain walls     

Statistical continuum theory for the effective conductivity of fiber filled polymer composites: Effect of orientation distribution and aspect ratio

Effective conductivity of polymer composites, filled with conducting fibers such as carbon nanotubes, is studied using statistical continuum theory. The fiber orientation distribution in the matrix plays a very important role on their effective properties. To take into account their orientation, shape and distribution, two-point and three-point probability distribution functions are used. The effect of fibers orientation is illustrated by comparing the effective conductivity of microstructures with oriented and non-oriented fibers. The randomly oriented fibers result in an isotropic effective conductivity. The increased fiber orientation distribution can lead to higher anisotropy in conductivity. The effect of fiber’s aspect ratio on the effective conductivity is studied by comparing microstructures with varying degrees of fiber orientation distribution. Results show that the increase in anisotropy leads to higher conductivity in the maximum fiber orientation distribution direction and lower conductivity in the transverse direction. These results are in agreement with various models from the literature that show the increase of the aspect ratio of fibers improves the electrical and thermal conductivity.     

Signal to noise ratio of superconducting tunnel junction detectors

The optimal signal to noise ratio for detectors based on superconducting tunnel junctions (STJ) is compared for the cases of a detector consisting of one single STJ, as well as of series and of parallel connections of STJs. A single STJ exhibits the best signal to noise ratio if the signal charge is independent of detector area. If signal charge increases in proprotion to the detector area, a parallel or a series connection of STJs would provide the optimum signal to noise ratio. The signal to noise ratio is deduced as function of junction parameters.     

Influence of crystal orientation on ECAP of aluminum single crystals

A single crystal of high purity aluminum, oriented with the {1 1 1} slip plane and the 1 1 0 slip direction rotated by 20° in a clockwise sense from the theoretical shear plane and the shear direction, was processed by equal-channel angular pressing (ECAP) through a single pass. This configuration was designated the 20° orientation and the results are compared with earlier data obtained on a similar high purity aluminum single crystal in the 0° orientation with the (1 1 1) slip plane and the 1 1 0 slip direction lying parallel to the shear plane and the shear direction. The results show that in both orientations the long axes of the subgrains lie parallel to the slip traces of the primary slip system and the average subgrain widths are 1.3 μm. However, the shearing characteristics are different because the 0° specimen exhibited a conventional B-type rolling texture whereas the 20° specimen deformed by slip on the primary slip system and this system rotated by 40° in a counter-clockwise sense as the specimen passed through the shear zone of the ECAP die.     

Influence of water-cement ratio on micro-cracking of ordinary concrete

The influence of the water/cement ratio on fracture toughness of ordinary concrete has been investigated. The stress intensity factorK _IIc and fracture energyJ _IIc has been tested (Mode II, shearing). The concrete structure was examined by SEM and the influence of water/cement ratio on concrete cracking has been established.     

噪声概率快速估计的自适应椒盐噪声消除算法

提出一种可识别噪声概率自动调节滤波窗口的自适应椒盐噪声消除算法。对非理想椒盐噪声污染图像随机区域进行变窗口中值滤波,将结果与滤波前比对获得噪声点数,滤波区域即按此点数排序。然后取每种滤波窗口下的中间三组数据,该数据平均加权获取图像噪声概率初估计,对初估计平均加权即得图像噪声概率。滤波前首先采用阈值法排除明显噪声点,剩余像素中再以离窗口中心像素距离平方的倒数为权值估计中心像素。最后由噪声概率按照T-S模糊规则对不同模型的输出估计值进行融合。实验证明,与传统中值滤波等算法相比,该算法具有噪声自动估计和自适应窗口调节能力,滤波后标准均方差可减少20%以上,速度可提高一倍多。     

Influence of noise on measurement errors in laser interference refractometers

The influence of noise in the optical and electronic channels of laser interference refractometers is subjected to a comparative analysis for several of the best-known methods used to measure the fractional part of an interference order.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 26–27, August, 1995.     

船舶近场声辐射特性初探

为了修正目前国内所普遍采用的船舶辐射噪声测量方法,建立了一个具有一定空间分布的船舶辐射噪声源模型。利用渡数积分方法仿真计算了该模型在自由场条件下的近程声场,并分析了近场辐射噪声的基本规律。仿真结果与国外文献提供的船舶水下辐射噪声近场特性吻合,验证了所建模型的正确性。     

Influence of fibre orientation on acoustic emission from filament wound pipes

The effect of the winding angle of filament wound pipes internally pressurized was investigated by means of the acoustic emission technique. The acoustic emission results were correlated with the theoretical data of the state of stress at the matrix-fibre boundary. The experimental results showed that acoustic emission strongly depended on fibre orientation. Acoustic emission signals were mainly caused by two types of failure of the composite: debonding on the matrix-fibre interface and transverse cracks in the lamina. The influence of fibre rotation on the acoustic emission behaviour was also taken into account. It is stated that the significant start of acoustic emission is due to cohesive cracking at the matrix-fibre boundary when the normal stress, to the fibre overreached the critical value of 11.5 MPa for all considered fibre orientations.     

Influence of noise on the noise-immunity indices of laser interference refractometers

The influence of noise on the resultant error probabilities in the detection of integral interference orders by various methods of the kind most frequently used in laser refractometry is investigated. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 46–49, March, 1996.