Laser-Monitor-Assisted Investigation of the Regions of Closure of Current on the Electrodes of an Atmospheric-Pressure Low-Current Carbon Arc

The results are given of observations of regions of closure of current on the electrodes of an atmospheric-pressure low-current carbon arc, performed using a laser monitor immediately during the time of burning of the arc. It is found that the time of existence of a cathode crater on a graphite cathode is 0.2–0.3 s. An analysis of images of the region of closure of current on a pyrographite cathode reveals evidence of melting of pyrographite. A comparison of images of the region of closure of current on the electrodes of a carbon arc with the available literature data on the conditions of closure of current on the anode and cathode enables one to establish the origins of the various details of images of the region of closure of current on the cathode and anode of a low-current carbon arc. The results of this comparison further lead one to conclude that a low-current electric arc is an arc with liquid cathode and anode spots, and that the melting process is a stabilizing factor as regards the current density in those spots.     

Estimation of thermal coefficients of magneto-optical media

Previously we described a method for estimating the thermal conductivity of magneto-optic recording media. The method relies on identifying the laser power that brings the maximum temperature of the TbFeCo layer to as high as the Curie temperature. We extensively use a similar method to estimate the heat capacity of a dielectric layer, a TbFeCo layer, and an aluminum alloy layer of magneto-optic recording media. Measurements are conducted on static disks with a beam of light focused on a TbFeCo layer. The method has the advantage of thermal diffusion depending on a multilayer structure and irradiation time.     

An experimental investigation of modes of flow under conditions of evaporation of liquid on a vertical heating surface

An experimental investigation is performed of the effect of temperature head on the flow of evaporating film of liquid, defined by the wetting line or by ribs, on a vertical heating surface. The experiments are performed under conditions of evaporation of R11 Freon in a medium of own vapor on a vertical copper plate, including the presence of ribbing. The visualization of flow is performed. Analysis is made of the effect of the evaporation intensity in the neighborhood of liquid-vapor-wall contact line on the conditions of film discontinuity and on the pattern of resultant streamer flow. It is demonstrated that, rather than spreading, the liquid in the case of streamer flow on the heating surface contracts downstream even for a close-to-zero equilibrium wetting angle. This is due to intense evaporation of liquid in the region of liquid-vapor-wall contact line, where the liquid film exhibits a minimal thickness, to the variation of curvature of the interface in this region, and to the emergence of thermal contact angle. The dependence of thermal contact angle on temperature head is determined. Dynamic measurements are performed of the local thickness of flowing films of liquid using a capacitance meter, and spectral analysis is performed of waves which arise because of instability of film flow on the evaporating film surface.     

Reduction of the dependence of the frequency of a passive resonant surface acoustic wave sensor with magnetic coupling on the angle of rotation of the shaft

The effect of connecting a rotating ring joint on the frequency of a passive contactless surface acoustic wave resonant sensor with the combined use of a model based on connected transmission lines and its equivalent electric circuit with lumped elements is analyzed. The considerable reduction in the dependence of the frequency of the sensor on the angle of rotation of the shaft and the reduction in the error of measurements carried out on the shaft when both rotating ring joints are completely symmetrically connected are demonstrated.     

A mechanism of nucleation during thermal decomposition of solids

A microscopic model based on the appearance, diffusion, and aggregation of point defects allows to calculate the time of appearance of the first nucleus on a surface during a reaction between a solid and a gas. Calculated distributions of these times of appearance of the first nucleus are qualitatively compared to experimental ones, previously determined. The appearance of the point defects seems to be the most influential step on the time of appearance of the first nucleus. Moreover the comparison between experimental and calculated distributions allows to conclude that the frequency of appearance of the defects is higher on the edges than on the faces of the single crystal.     

Two modes of bulk boiling of superheated liquid on a wire

Based on the results of qualitative analysis, the dynamics of a microlayer of liquid in two steady-state modes of motion of evaporation front propagating in a moderately superheated layer of liquid on a wire are described. Relations are suggested for the calculation of the front velocity depending on the degree of super-heating of liquid and on the heat flux density on the heating surface, as well as the condition of transition from nucleate to explosion boiling     

An experimental investigation of a method of determining the flash point of petroleum products

The results of experimental investigations of a method of determining the flash point of petroleum products, carried out on motor oils, are presented. It is established that a change in the volume of the petroleum product has no effect on the flash point, but a change in the rate of heating has a considerable influence on this parameter.     

Effects of recording-erasure dynamics of storage capacity of a wavelength-multiplexed reflection-type photorefractive hologram

We investigate the effects of the recording-erasure dynamics on the storage capacity of a wavelengthmultiplexed reflection-type photorefractive hologram by using a coupled-recording-wave approach. A closed-form expression for the diffraction efficiency for on-Bragg incidence is derived. The dependence of the equalized diffraction efficiency on the number of recordable holograms is analyzed. The result shows that the storage capacity of a reflection-type hologram is of the same order of a transmission-type hologram but higher than the previous predictions based on an uncoupled-recording-wave theory.     

Influence of N-alkanes on contact angle and flotability of quartz

Measurements of time dependence of the contact angle were carried out for water drops on a quartz surface in the presence of saturated hydrocarbon vapour as well as on a quartz surface previously wetted with a hydrocarbon. The results obtained were compared with theoretically calculated values on the basis of the modified Young equation and the literature data for the surface free energy components of quartz covered with a monolayer water film. On the basis of the measurements and calculations it was found that the values of the contact angle in the studied systems depend on the kind and thickness of hydrocarbon film present on the quartz surface, as well as on the thickness of water film present on this surface. Changes of the contact angle with the hydrocarbon film thickness are characterized by the maximum and minimum values. This allows previously obtained results of the quartz flotation activity changes in the presence of the aliphatic hydrocarbon films to be explained.     

Measurements of mechanical properties of alpine skis in the laboratory

A few years ago Ian McMillan, the editor of the magazine SKIING, UK requested NEL to carry out tests on a batch of skis. For some time his magazine had been publishing information from a German testing laboratory on the mechanical properties of skis but he had decided to try to organise his own tests in the hope of giving his readers better information on different types of skis in a manner easier for them to understand. The author was asked to try to set up the tests because of personal interest in skiing so a meeting was arranged with Ian McMillan and his technical advisor, Gustaf Fischnaller. an Austrian who now runs a ski school at Glenshee, in Scotland. He has seen ski tests being carried out in Austria and could describe the test methods. After extensive discussion, a decision was taken on a range of tests designed to provide information on how the skis would behave on snow.     

The flow of ideas and timing of evaluation as determinants of knowledge creation

There are different perspectives on the study of knowledge inorganizations, developed in economics, sociology, anthropologyand organization theory. Several authors followed Schumpeter'sidea that innovations are new combinations of existing knowledgeand incremental learning. Kogut and Zander further developedthis idea and defined knowledge as a portfolio of options, andemphasized the importance of combinative capacities in knowledgecreation. In a similar vein, Garud and Nayyar developed a notionof the transformative capacitiy of a firm in analyzing technologicalinnovations. This paper follows in this tradition by pointingat the effects of different organizational structures on theflow of ideas and on the possibility of combining proposalsin organizations. Communication structures, span of controland timing of evaluation are shown, using computer simulations,to have a large impact on the degree to which commonalitiesand complementarities among ideas and proposals can be detectedand on the eventual combination of ideas for knowledge creation.Implications for organizational design are discussed.     

风量对空气源热泵换热器结霜影响的分析

关于风量变化对结霜量影响的研究目前一直存在一定的分歧。本文通过对前人仿真方法和结论的分析，在保证翅片表面温度低于0℃的条件下，用凝水量来反映结霜量的大小，从而将动态模型简化为稳态模型，并在风量变化的同时考虑环境参数的变化以及换热器结构的变化。仿真结果表明风量对结霜量的影响与环境参数密切相关。干球温度的变化虽然影响结霜量的大小，但结霜量最大时对应的风量却不受空气干球温度的影响，临界风量随着相对湿度的增加而增加。另外换热器回路等结构参数也会一定程度地改变风量的影响作用。     

Fem prediction of the influence of warm prestressing on fracture toughness of heat-resistant steel

We present a procedure of prediction of the influence of warm prestressing combined with cycling on the brittle strength of steel 15Kh2MFA. Using a finite-element method, the effect of the combined warm prestressing on the stress-strain state at a fatigue crack tip is studied in an elastic-plastic statement. Electron microscopic observations of fracture surfaces have revealed that fracture is initiated at some distance from the fatigue crack front. Based on the pattern of influence of the plastic prestrain level on the cleavage stress of steel 15Kh2MFA and the experimental CID value, a method is put forward for finite-element modeling of the stress-strain state at a crack tip during the specimen fracture. Using the results of the finite-element modeling, the relevant curves have been plotted and an approximating formula has been proposed to represent the influence of the combined warm prestress level on the fracture toughness of steel 15Kh2MFA.     

Electrocrystallization of zinc on copper single crystal planes under the influence of an asymmetric alternating current

Zinc electrodeposited from a sulphate bath on to copper single crystal planes revealed a layer-type growth on copper (111) and (100) planes and ridge-type growth on the (110) plane at low d.c. densities. Dendritic growth appeared at higher d.c. densities on all the planes. Superimposition of a.c. on d.c. during electrocrystallization produced hexagonal pyramids on the copper (111) plane, which were transformed into hexagonal dendrites under suitable a.c. to d.c. ratios. The influence of a.c. on the degree of epitaxy of zinc on copper and the mechanism of the dendrite initiation are discussed.     

传感器温漂对磁悬浮转子控制精度的影响

传感器温漂对磁悬浮转子的控制精度有很大的影响．磁悬浮转子在运转时有较大的温升．磁悬浮转子的结构设计对其工作温度的高低及其分布有很大影响．本文研究了磁悬浮转子实际工作温度场的不均匀性,对涡流传感器的温度特性进行了实验测试,对传感器的布置形式对磁悬浮转子精度的影响进行了分析．研究了磁悬浮转子结构形式、结构参数、传感器的个数及其测试方式等对磁悬浮转子控制精度的影响程度和变化规律．在上述研究的基础上得出了减少传感器温漂对磁悬浮转子控制精度影响的结构设计原则．     

A simplified model for the assessment of the impact probability of fragments

A model was developed for the assessment of fragment impact probability on a target vessel, following the collapse and fragmentation of a primary vessel due to internal pressure. The model provides the probability of impact of a fragment with defined shape, mass and initial velocity on a target of a known shape and at a given position with respect to the source point. The model is based on the ballistic analysis of the fragment trajectory and on the determination of impact probabilities by the analysis of initial direction of fragment flight. The model was validated using available literature data.     

The Effect of Inelastic Collisions of Molecules of a Diatomic Gas with Rotational Degrees of Freedom

The problem on Barnett slip of gas along a plane surface is solved within the suggested kinetic model for a diatomic gas with rotational degrees of freedom of molecules, which takes into account transitions from rotational degrees of freedom to translational and vice versa. The Barnett slip coefficient is obtained in the form of a function dependent on the frequency of inelastic collisions of gas molecules and on the coefficient of accommodation of tangential momentum.     

Effect of systematic errors in spectral photometric data on the accuracy of determination of optical parameters of dielectric thin films

The determination of optical parameters of thin films from experimental data is a typical task in the field of optical-coating technology. The optical characterization of a single layer deposited on a substrate with known optical parameters is widely used for this purpose. Results of optical characterization are dependent on not only the choice of the thin-film model but also on the quality of experimental data. The theoretical results presented highlight the effect of systematic errors in measurement data on the determination of thin-film parameters. Application of these theoretical results is illustrated by the analysis of experimental data for magnesium fluoride thin films.     

Method of determination of palladium concentration for C-Pd nanostructural films as a function of film thickness,roughness and topography

In this paper a method of determination of Pd in a carbon-palladium film (C-Pd film) deposited on a quartz substrate is presented. This method is based on energy dispersive X-ray spectroscopy (EDX) and all experiments were performed using a scanning electron microscope (SEM) equipped with EDX system. Qualitative and quantitative analyses were carried out for C-Pd films prepared by PVD method in different technological conditions. It was shown that results of the experiments depended on the structural model, film thickness and electron beam energy used for Pd content calculation. This method enabled us to conclude on the homogeneity of palladium distribution in the whole volume of carbonaceous matrix, depending on the parameters of PVD process. Additionally, these studies showed that a different palladium concentration in C-Pd films had a significant impact on their topography and morphology.     

Evaluation of two mutliscale models for the simulation of cross-die forming of Dual Phase (DP) steels

Two micro-macro modelling approaches, one based on crystal plasticity and the other on a Mori-Tanaka mean-field model, are presented and used for the simulation of forming operations on dual phase (DP) steels. The material parameters are determined based on bending-unbending experiments while deep-drawing with a cross-shaped die is simulated based on user-defined material laws (UMAT) in the ABAQUS finite element code. It is demonstrated that accurate predictions would require a combination of both modelling approaches.