传声器校准用活塞发生器的研究进展

简要介绍了传声器校准用活塞发生器的基本原理和技术关键,综述了传声器校准用活塞发生器整体设计、活塞位移测量、影响因素修正、初始条件确定等方面的研究进展,对活塞发生器发展趋势进行了探讨.     

In situ electrocatalytic oxidation of acid violet 12 dye effluent

Electrochemical treatment of organic pollutants is a promising treatment technique for substances which are recalcitrant to biodegradation. Experiments were carried out to treat acid violet 12 dye house effluent using electrochemical technique for removal color and COD reduction covering wide range in operating conditions. Ruthenium/lead/tin oxide coated titanium and stainless steel were used as anode and cathode, respectively. The influence of effluent initial concentration, pH, supporting electrolyte and the electrode material on rate of degradation has been critically examined. The results indicate that the electrochemical method can be used to treat dye house effluents.     

Study on the Spatial Resolution of Imaging Technique for Absorption Loss Measurement of Optical Coatings

The uniformity of optical coatings becomes more and more important as large diameter optical devices are widely used. Absorption loss in optical components, particularly in optical coatings, is a limiting factor in high-power laser applications. This article analyzes the main factors, which affect the spatial resolution of three techniques for surface absorption loss measurement, including the photothermal deflection technique, the surface thermal lens technique, and the photothermal detuning technique. The influence of the size of the heating and probe beam on the photothermal detuning technique is studied in detail. Experiments are conducted to study the photothermal signal of the photothermal detuning technique for absorption measurement of the optical coating point by point. The results show that the main factors, which affect the spatial resolution of imaging measurements for absorption loss of coatings, are the heating beam size and the step accuracy of the sample translation stage. The heating and probe beam sizes has a significant impact on the application of the photothermal detuning technique. Experimental result shows that the photothermal detuning technique can be used for imaging of absorption loss measurements of optical coatings. The results provide theoretical and experimental supports for further application of the photothermal detuning technique.     

Evaluation of micro-mechanical properties of nonlinear cementitious composite using large-displacement transient nanoindentation analysis

Nanoindentation technique is employed for evaluation of mechanical properties of homogeneous materials at micro-level. Many engineering materials, especially cement and concrete composites, which are extensively used as building materials, exhibit phase heterogeneity and are highly porous. The presence of pores highly influences the response obtained from nanoindentation tests. In this study, mechanical properties of Calcium-Silicate-Hydrate (C-S-H), the primary binding agent in cementitious composites, are investigated using a simulated nanoindentation technique. The influence of presence of pores and its geometrical distribution on the non-linear response of C-S-H phases and the stress distribution are critically analysed.     

Allocation of test times in multi-state systems for reliability growth testing

This paper generalizes a reliability growth test allocation problem to series-parallel multi-state systems. An algorithm, which determines the testing time for each system element in order to maximize the entire system reliability when total testing resources are limited, is suggested. The algorithm can handle both repairable and non-repairable multi-state systems. The Crow/AMSAA reliability growth model is used to evaluate the influence of testing time on the reliability of the elements composing the system. System reliability is defined as the ability of the system to satisfy variable demand represented by a cumulative demand curve. To evaluate multi-state system reliability, a universal generating function technique is applied. A Genetic Algorithm (GA) is used as an optimization technique. The basic GA procedures adapted to the given problem are presented. Examples of the determination of reliability growth test plans are demonstrated.     

Untersuchungen zum Ermüdungs-Rißwachstumsverhalten des austenitischen Stahles X 6CrNi 18 11 (1.4948)

Investigations of the Fatigue Crack Growth Behaviour of the Austenitic Stainless Steel X 6CrNi 18 11 (1.4948) The fatigue crack growth behaviour of the heat resistant austenitic stainless steel X 6CrNi 18 11 (material number 1.4948), which is used as the structural material for the primary and secondary heat transfer systems of the liquid metal fast breeder reactor SNR 300, is described. The parameters under consideration are the temperature in the range from 308 K up to 973 K, the frequency from 0.5 Hz up to 20 Hz, the stress ratio R as well as the heat-to-heat variation. The minimum ligament size criterion as well as the influence of the test technique on crack propagation are discussed. For the various test parameters the constants C and n of the Paris equation are calculated. The test results demonstrate a small influence of the heat-to-heat variation on the crack growth. At low stress ratios and at room temperature the influence of frequency is very small. A strong influence of the stress ratio R on the crack growth rate is observed. For higher R-values and high temperatures a distinct influence of the frequency on the fatigue crack propagation is shown.     

基于动态子结构的空间螺旋弹性传热管振动特性研究

弹性传热元件振动的诱发与控制是流体诱导振动强化换热技术的关键,对弹性传热元件固有振动特性的研究至关重要。弹性传热元件一般是多根弯曲管束,通过连接体胀接后悬臂支撑,其结构的复杂性导致直接求解其固有振动特性的困难。依据动态子结构理论,通过超单元技术求解各子结构的刚度矩阵和质量矩阵,并利用固定界面模态坐标综合法数值计算了空间螺旋管束的固有振动特性,分析了不同结构参数对其振动特性的影响。结果表明,空间锥形螺旋管束的振动主要表现为轴向振动;锥度、截面直径等参数对其振动特性的影响较大,管壁厚度、螺旋节距等参数对其振动特性影响较小。     

Simulation of optical fiber growth in three dimensions

We have carried out 3-dimensional molecular dynamics simulations of a crystal growth technique known as laser heated pedestal growth. Previously, we simulated this technique in 2 dimensions and our current work is an attempt to extend those simulations to the more realistic 3D case. We demonstrate that such 3D simulations are feasible in a study of the influence of the growth speed and the influence of the laser heating on various aspects of the fiber growth. Although much more realistic than the 2D study, the moderate system sizes used in this study and other crude representations of the experimental process still prevent us from making quantitative comparisons with the latter.     

Microencapsulation I. Phase Separation or Coacervation

Phase separation or coacervation is one of the oldest and perhaps the most widely used method of microencapsulation. This paper discusses phase separation or coacervation as a technique of preparing microcapsules. The basic differences between simple and complex coacervation are described and the various factors which influence simple and complex coacervation are discussed. Schematic ternary phase diagrams involved in the phase separation or coacervation processes are included and the basic schemes describing the process of microencapsulation are outlined.     

用神经网络技术实现的光纤位移传感器

描述了一种智能型位移光纤位移传感器，它用差动比值法减小漂移和不同的反射介质的影响，用人工神经网络技术减小非线性误差。实验结果表明，使用这些技术后，各方面指标都远远优于传统方法。     

Admixtures in cement: a study of dosage rates on early hydration

The authors have shown from earlier work that the electrical response of cement paste to an alternating electrical field can be used as a technique for monitoring hydration and phenomena such as setting and hardening. This paper demonstrates an area in which the technique could prove effective, by showing the influence of a range of commercial admixtures on electrical response. It is clearly indicated that admixtures have a definite effect on the response characteristics.     

Uncertainty analysis based on sensitivity applied to angle-ply composite structures

This article describes a finite element-based formulation for the statistical analysis of the response of stochastic structural composite systems whose material properties are described by random fields. A first-order technique is used to obtain the second-order statistics for the structural response considering means and variances of the displacement and stress fields of plate or shell composite structures. Propagation of uncertainties depends on sensitivities taken as measurement of variation effects. The adjoint variable method is used to obtain the sensitivity matrix. This method is appropriated for composite structures due to the large number of random input parameters. Dominant effects on the stochastic characteristics are studied analyzing the influence of different random parameters. In particular, a study of the anisotropy influence on uncertainties propagation of angle-ply composites is carried out based on the proposed approach.     

Photothermal measurements on optical thin films

An overview of the application of the photothermal technique for optical as well as thermophysical characterizations of thin films is given. The peculiarities of this technique are discussed in some detail, and selected important results are pointed out. Emphasis is placed on the influence of both residual absorption and randomly distributed inhomogeneities in thin films on their laser-damage resistance.     

Effect of drying technique on some physical properties of cross-linked high amylose/pectin mixtures

Polymers mixtures as well as cross-linking reactions are approaches that have been used successfully to modulate the polymers characteristics in order to improve the control over drug release rate. High amylose and pectin are polysaccharides frequently used to prepare drug delivery systems. Since the drying technique can strongly influence the properties of such systems, the aim of this work was to characterize high amylose/pectin mixtures cross-linked with sodium trimetaphosphate and dried by different techniques – oven and lyophilization. The results showed that samples dried by lyophilization presented reduced particle size, higher porosity and higher swelling ability than the samples dried in oven. Besides, lower thermal stability and different diffraction patterns showed by the former particles should reflect the structural changes as a function of drying technique.     

飞秒脉冲光谱测量对时域波形重建的影响

利用光谱相位还原直接电场重建法对飞秒脉冲激光时域波形进行重建,分析了光谱测量波长示值误差和光谱辐照度示值误差对于飞秒脉冲光谱测量的影响。使用低压汞灯对光谱仪波长校准,根据校准结果,对测量光谱蓝移和红移,通过数值模拟研究波长示值误差对重建脉冲波形的影响;利用光谱辐射照度标准装置对光谱仪光谱辐照度校准,通过增加白噪声模拟分析和各种常用反射片实验测量研究光谱辐照度示值误差对重建脉冲波形的影响。结果表明,光谱测量波长示值误差和光谱辐照度示值误差对于飞秒脉冲光谱测量的相对标准差在1%之内。     

中间相沥青基碳电极材料的制备工艺优化与性能

以煤焦油沥青为原料,采用"中间相调制-化学活化"工艺制备了超级电容器用活性碳电极材料,考察了中间相调制温度对活性碳晶体结构、孔径分布、电容量特性的影响,并分析了中间相沥青的调制过程及不同实验条件对活性碳晶体结构、孔径分布、电容量特性的影响。结果表明,中间相沥青调制温度主要集中在190～492.5℃,随中间相调制温度升高,活性碳电极材料的振实密度明显增大,在500℃条件下制备的活性碳材料具有最高的比电容量,达到103F/g,较高的调制温度能提升活性碳中碳的边缘层含量,从而提高材料的面积比电容量。     

A review of factors influencing defect detection in infrared thermography: Applications to coated materials

Infrared thermography is a technique that is used to nondestructively inspect parts for the presence of subsurface defects. The technique normally consists of applying heat to one surface of the part and observing the thermal response, using heat-sensing devices such as infrared cameras, as the part cools. Internal defects such as voids modify the thermal response and produce local hot or cold spots on the specimen surface. For the detection of subsurface defects, the sensitivity of the technique to different parameters such as defect depth, material properties, and heating methods has not been established due in part to the complex nature of the heat/flaw interaction. A finite element model is used here to examine the influence of these parameters on defect dectability. The model shows that the defect detectability decreases with increasing defect depth beneath the surface, and that the technique is most sensitive to the inspection of low thermal diffusivity coatings bonded to high thermal diffusivity substrates. The results also show that the heat pulse duration should be made as short as possible to maximize defect detectability.     

Studying the Mechanical Behaviour of Asphalt Mixture with the Grid Method

Abstract: The aim of this work is to analyse the strain fields that take place in several asphalt mixture specimens subjected to compression tests. The grid technique is used for this purpose. The main features of this strain measurement technique are first described. The obtained results are then discussed. They show that very strong heterogeneities take place in the strain fields. They are due to the very different mechanical properties of the constituents. Various testing conditions are also investigated because they directly influence the quality of the measurements and the ability of the grid technique to detect small strain amplitudes with a good spatial resolution, this last feature being crucial here because of the very nature of the material under test.     

Modelling of Wideband Concentric Ring Frequency Selective Surface for5GDevices

Frequency selective surfaces (FSSs) play an important role in wireless systems as these can be used as filters, in isolating the unwanted radiation, in microstrip patch antennas for improving the performance of these antennas and in other 5G applications. The analysis and design of the double concentric ring frequency selective surface (DCRFSS) is presented in this research. In the sub-6 GHz 5G FR1 spectrum, a computational synthesis technique for creating DCRFSS based spatial filters is proposed. The analytical tools presented in this study can be used to gain a better understanding of filtering processes and for constructing the spatial filters. Variation of the loop sizes, angles of incidence, and polarization of the concentric rings are the factors which influence the transmission coefficient as per the thorough investigation performed in this paper. A novel synthesis approach based on mathematical equations that may be used to determine the physical parameters of DCRFSS-based spatial filters is presented. The proposed synthesis technique is validated by comparing results from high frequency structure simulator (HFSS), Ansys electronic desktop circuit editor, and an experimental setup. Furthermore, the findings acquired from a unit cell are expanded to a 2 × 2 array, which shows identical performance and therefore proves its stability.     

Experimental features affecting the transparency of YAG ceramics

This article focuses on the importance of the ceramic production process for the final transparency and overall optical quality of materials to be used as laser hosts. YAG-based ceramics are prepared starting from commercial powders. The materials are prepared by reactive sintering in a clean atmosphere and under high vacuum. Nd or Yb are selected as active elements as the more appropriate for high energy and high peak power lasers. The powder type and treatment and the solvent removal technique are described in detail as well as the experimental conditions adopted during shaping. The influence of the pre-sintering and sintering cycles on the reaction among the involved oxides and on the microstructure after sintering is shown. The optical characterization is also reported.