The Influence of the Atmosphere on the Wavelength of the He-Ne Laser and the Solution of Corrections of the Laser Interferometer

A simple approximation of the wavelength of single frequency He-Ne laser as a function of temperature, pressure and relative humidity is presented. This approximation is suitable for the simple application in the portable laser interferometer. Comparison with the Owens and Edlén formulae is also presented and it is shown that the linear correction limits its accuracy.     

表面活性剂在处理太安表面静电中的应用

通过实验检验表面活性剂对太安表面静电积累的降解效果,测定表面活性剂对太安基本性质的影响,分析比较对表面活性剂的优化选择。     

Method of including the anisotropy of the optical properties of the surface and the nonunidimensionality of the system in determining the effective radiation

Based on the method of successive substitutions, an integral equation is derived in which multiple reflections are explicitly identified. This equation is used provide simple methods of estimating the local effective radiation of two-dimensional and three-dimensional systems of surfaces, with due regard for the anisotropy of their optical properties. A cylindrical cavity confined by the surface of a right circular cylinder with a side pyrometric hole is treated as an example. The results obtained by the suggested method are compared with the data of direct solution of an integral equation for the two-dimensional problem.     

Approximate determination of the magnitude of the critical size in the problem of the evolution of an impact

The evolution of a nonlinear dynamic system after the action of a localized effect (impact) is examined. A semiquantitative method is suggested for determining the critical size of the impact upon exceeding which the diffusional mode of decay in the system is replaced by a wave mode of propagation. The use of the proposed technique to evaluate the critical size of an impact in a realistic model of an oceanic ecological system is demonstrated.P. P. Shirshov Institute of Oceanology, Moscow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 4, pp. 398–404, April, 1994.     

Study of the Influence of the Source Quality on the Determination of the Shape Factor of Beta Spectra

We are developing metallic magnetic calorimeters for beta spectrometry with the aim of determining the shape factors of beta spectra. The beta emitter is enclosed inside the detector absorber and the absorber size is chosen such that the detection efficiency is close to 100% for the entire spectrum. The nature of the deposit of the beta emitter is critical for precise measurement. A dependence of the shape of the spectrum on the quality of the source has been observed, supposedly due to interactions between the electrons and the deposit itself. We chose for this comparative study a nuclide with an allowed transition whose theoretical spectrum is relatively well-known, ⁶³Ni, a pure beta emitter with an endpoint energy of 66.98?keV. Results of measurements of ⁶³Ni deposited with different techniques are presented and compared to each other and to the theoretical spectrum.     

Analysis of the effect of the shape of the radiation pattern on the accuracy of azimuth measurements by the monopulse method

The effect of the shape of the radiation pattern of the difference channel of a monopulse antenna on the accuracy of angular-coordinate measurements is estimated. The least root mean square deviation is obtained using a radiation pattern with a Chebyshev amplitude distribution. Of the practical amplitude distributions a “parabola on a pedestal” of 0.1–0.316 is preferable. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 53–54, April, 1998.     

感压膜片预张力对电容薄膜真空规输出特性的影响

电容薄膜真空规中感压膜片在安装时通常须先施加预张力,再固定.为研究感压膜片预张力对电容薄膜真空规输出特性的影响,以现有电容薄膜真空规为对象,基于COMSOL Multiphysics软件,建立有限元模型,得到了不同预张力下输出电容的仿真解,并与理论计算结果进行了比较,分析了预张力对输出电容的影响.同时分析了真空规线性度...     

On the positive definiteness of the operator of the micropolar elasticity

Summary The present paper is concerned with the static theory of anisotropic and inhomogeneous micropolar elastic solids. The operator of micropolar elasticity is considered and the positive definiteness of this operator for the first boundary value problem is proved. This fact leads to the existence of a generalized solution and to the applicability of the variational method [1] to this problem.     

Calculation of the Characteristics of the Initial Section of the Plasma Generator Channel

An equilibrium magnetogasdynamic model of plasma is used to calculate the flow and heating of gas in the initial section of the plasma generator channel. The gas is heated by an electric arc. The distribution of the electric field intensity, temperature, velocity, and pressure drop is obtained depending on changes in the current strength, gas flow rate, and the wall thickness of the electrode nozzle. It is found that axial zones of return flow are formed in the vicinity of the initial section of the channel. The calculation results are compared to the experimental data.     

On the sensitivity of the vibrational response of the human head

A parametric study based on finite element analysis is performed in order to investigate the sensitivity of the eigenfrequency spectrum of the human head system upon variation of its constitutive material properties. This study stems from the ever increasing medical interest connected to early diagnosis of brain edema and the lack of existing accurate and non-invasive diagnostic methods to achieve it. The present computational work aims to resolve the question of whether or not such a spectrum shifting is detectable with current experimental procedures. The human head is modeled as a prolate spheriod consisting of confocal shell representing the scalp-skull system, in contact with the subarachnoidal space which surrounds the brain. The skull is modeled as an isotropic elastic material whereas the brain is assumed to be a frequency dependent viscoelastic body.     

About the numerical simulation of the dynamics of granular media and the definition of the mean stress tensor

To define the stresses in a granular medium considered as a continuum, Weber has calculated a tensor at a point by averaging the contact forces in the vicinity. However this tensor is not symmetric. Besides, the Weber formula neglects the body forces, which does not allow it to describe dynamical problems. In the present work, it is proposed to use a general expression of the mean stress tensor based not only on the contact reactions but also on the body forces. It is proved that this tensor is automatically symmetric and invariant by translation. Next, the pertinence of this approach is illustrated by an analytical example. It can be clearly ascertained that accounting for the contribution of the gravity and inertia effects is essential to ensure the symmetry of the stress tensor, according to Cauchy theory. We then propose to extend this definition of the mean stress tensor to a space–time analysis. An average in time as well appears to be pertinent. Finally, numerical simulations with a large number of grains are performed using the software ‘MULTICOR' developed in our laboratories and based on the contact dynamics and the bipotential approach. The attention is particularly focused on the motion of ensiled matters.     

Increasing the Reliability of the Primary Processing of the Results of Measurements

A new approach is considered to processing the results of measurements. It is utilized as a basis for carrying out primary processing including the detection and elimination of anomalous measurements and also for cleansing results of additive noise components. The results are presented of an analysis of the efficiency of a method for multiplying estimates when cleansing the results of measurements of additive noise components.     

钟罩装置标准容积的数学模型研究与建立

在钟罩装置标准容积实测数据的基础上,通过描点图定性分析了钟罩罩体高度和半径的关系特性,提出采用傅里叶级数建立数学模型,借助Matlab获得理想的函数方程,并分析了其拟合标准差。实际应用中采用光栅尺测量钟罩下降的高度,运用定积分原理对函数进行积分获得钟罩下降任意高度时排出的气体容积值,在瞬时流量下限标准容积的相对扩展不确定度达到4×10^-4(k=2),相对以半径平均值为估计值的方法,降低了66.7%,同时可实现钟罩在检测过程中任意点的启停。     

转子与泵体间隙对转子泵性能影响的数值模拟

转子泵是一种容积式泵,由于其具有机构简单、使用寿命长、维护简单等优点,现在已经被广泛运用于生活污水、城市污泥、高黏度液体甚至是固液两相流的处理行业中。但是实际生产制造过程中,转子曲面与泵体之间的间隙依据经验设计,没有进行过具体的数据分析。在分析圆弧型三叶型凸轮转子泵线型的基础上,建立凸轮转子泵的二维模型,利用Fluent数值分析软件,分析不同转子与泵体间隙下,转子泵内部流场的分布状态,得到端面间隙对三叶型凸轮转子泵性能的影响规律。仿真结果分析表明:转子与泵体间隙对三叶圆弧型凸轮转子泵的容积效率有一定的影响。     

Understanding the role of the insulator in the performance of ZnO TFTs

The performance and stability of ZnO thin film transistors (TFTs) with three different insulators are examined. It is found that the on-state performance is significantly enhanced with AlN as gate insulator in comparison to SiO₂ or SiN. This behaviour is consistent with the excellent lattice match of AlN with ZnO which results in reduction of subthreshold slope. Despite enhanced on-state performance the shift in threshold voltage under gate bias stress however appears unmitigated. Stability in ZnO is primarily due to trapping within the bulk of the semiconductor and/or close to the interface.     

Fractal study of the fluctuation characteristic in the calibration of the cryogenic thermocouples

The accuracy of the temperature measurement depends strongly on the accuracy of the temperature sensor. The commonly used cryogenic thermocouples are calibrated by using a specially designed calibration system. The calibration is performed in the temperature range of from liquid nitrogen temperature (about 77 K) to the room temperature (300 K). The calibration results show that the accuracy is around several tens of mK, which meets the requirement of the experiments. However, it is found that the temperature fluctuation of the thermocouple is quite larger even if the temperature is well controlled, which indicates that the non-linear aspect characteristic plays a certain role in the calibration. The temperature fluctuation of the calibration process is analyzed by using the non-linear analysis method.     

Influence of the form of the phonon spectrum on the transition temperature of superconductors

The influence of the form of the phonon spectrum on the superconducting transition temperatureT _S under the usual pairing mechanism is investigated. The coupling constant , which determinesT _S in the two-phonon-peak and acoustic dispersion models, is calculated, and its dependence on the usual coupling constant and other parameters is determined. It is shown that the maximum possible value of is unity. An expression is derived forT _S ,making it possible to find the exact numerical value of the coefficient of the exponential function for any form of phonon spectrum.     

The Importance of the Purification Step and the Characterization of the Products in the Synthesis of Carbon Nanodots

In the synthesis of carbon nanodots (CNDs), the critical step of the purification from the starting materials and unwanted side products is faced. In the exciting race toward new and interesting CNDs, this problem is often underestimated, leading to false properties and erroneous reports. In fact, on many occasions, the properties described for novel CNDs derive from impurities not completely eliminated during the purification process. Dialysis, for instance, is not always helpful, especially if the side products are not soluble in water. In this Perspective, the importance of the purification and characterization steps, in order to obtain solid reports and reliable procedures, is emphasized.     

径向冲孔模设计

对盒体零件的冲孔工艺方案进行了分析,介绍了各种冲孔工艺方案的优缺点,从而确定了利用凸轮机构,实现了该零件的径向冲孔。介绍了该模具结构及工作过程,给出了零件的工艺计算方法,提出了模具的设计方法,为解决同类零件的冲孔提供了参考。