共查询到20条相似文献,搜索用时 46 毫秒
1.
E. I. Asinovskii V. M. Batenin I. I. Klimovskii V. V. Markovets 《High Temperature》2001,39(5):739-752
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. 相似文献
2.
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. 相似文献
3.
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. 相似文献
4.
G. V. Shuvalov 《Measurement Techniques》2009,52(10):1119-1121
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. 相似文献
5.
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 相似文献
6.
Bronisław Jańczuk Emil Chibowski Tomasz Białopiotrowicz 《Journal of Materials Science》1990,25(2):1353-1356
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. 相似文献
7.
J A Mackinnon 《Strain》1991,27(1):11-14
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. 相似文献
8.
O. M. Shteinberg 《Measurement Techniques》2012,54(12):1388-1395
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. 相似文献
9.
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. 相似文献
10.
The Effect of Inelastic Collisions of Molecules of a Diatomic Gas with Rotational Degrees of Freedom
A. B. Poddoskin 《High Temperature》2005,43(6):947-950
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. 相似文献
11.
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. 相似文献
12.
O. I. Balyts'kyi 《Materials Science》1998,34(4):574-583
We present two methods for the investigation of the influence of hydrogen on the propagation rate of a crack and behavior
of fracture of high-strength steels. The method for investigation of the influence of electrolytic hydrogenation on a subcritical
growth of a crack in high-strength steels is based on the use of simple beam specimens of a certain geometry and on the application
of lateral loading in such a way that the stress intensity factor can be constant at the tip of a preliminary induced crack.
The method is of great importance for the performance of comparative experiments in evaluating the influence of active media
and structural anisotropy of specimens made of high-strength steels with limited sizes on their corrosion crack resistance.
Typical examples of the application of the method to investigation of the role of electrolytic hydrogenation in subcritical
propagation of cracks and their branching in highstrength steels are given. The method for investigation of heat release under
strain and fracture of hydrogenated specimens involves the use of microcalorimetric devices, which allow one to study the
influence of hydrogenation on peculiarities of the kinetics of elastic and plastic strains of high-strength steels. We illustrate
the efficiency of the method proposed by plotting the “load-elongation” curves and corresponding (in time) characteristics
of heat release power in the process of strain and fracture of specimens made of a high-strength steel.
Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv,
Vol. 34, No. 4, pp. 113–120, July–August, 1998 相似文献
13.
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. 相似文献
14.
S. A. Zhdanok I. F. Buyakov A. V. Krauklis K. O. Borisevich 《Journal of Engineering Physics and Thermophysics》2009,82(3):407-413
Results of experimental investigations on the formation of carbon nanostructures in a reactor as a result of the decomposition
of hydrocarbons in a low-temperature plasma are presented. The influence of the internal geometry of the reactor, the temperature
regimes, and the relative content of a reagent and an oxidizer in the working mixture on the formation of carbon nanostructures
has been investigated. It was established that ordered carbon structures are formed on the surface of a metal containing iron
and nickel. Data on the production rate of the process and the content of the structured carbon in the material obtained are
presented. 相似文献
15.
The influence of reactant characteristics on morphological development through the stages of combustion synthesis was investigated using a titanium-carbon system. The effect of the characteristics of a variety of carbons (carbon blacks, graphites, and cokes) and a variety of titanium powders on the density and microstructure of combusted and uncombusted sample compacts was studied. The size of the titanium particles had a relatively small influence on the density of the final (TiC) product but had a significant effect on its microstructure. The structure of the carbon blacks (as judged by the n-dibutyl phthalate absorption number, DBP) had a direct influence on the density of the uncombusted and combusted samples: low-structure carbon blacks resulted in higher densities for both cases. Products made with natural graphites had higher densities than those made with synthetic graphites. The surface area of carbon and graphite reactant powders had less influence on the density of the product than on its network morphology. Cored structures in TiC products made from certain carbon and graphite powders were observed and are explained in terms of their ash (oxide) content. 相似文献
16.
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。 相似文献
17.
This paper describes a specific influence of crystailographic texture on tensile properties of the titanium alloy VT6 under superplastic flow conditions. The texture effect has been examined on alloy states with identical microstructures but with different preferred grain orientations. Tests over wide temperature and strain-rate intervals have shown that the formation of a strong texture as a result of pretreatment of a titanium alloy leads to a decrease in flow stress, an increase in plasticity and a shift of the optimum strain-rate region to higher rates. Data on the effect of texture on the anisotropy of properties of the VT6 alloy are also presented. The present results suggest that the influence of preferred orientation on the characteristics of superplastic flow is a general phenomenon for finegrained superplastic materials. 相似文献
18.
P. V. Yasnii Yu. I. Pyndus V. B. Glad’o I. B. Okipnyi I. V. Shul’gan 《Strength of Materials》2011,43(2):113-121
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. 相似文献
19.
We examine the effect of a change in phase of the reflected electromagnetic wave when measuring a surface profile using a
scanning white-light interference microscope and a phase-shifting coherent light interference microscope. We present the results
of experiments measuring the thickness of an aluminum coating deposited on a silicon wafer, without any phase shift correction
and with phase shift correction, calculated from handbook data and from the results of ellipsometric measurements. We compare
with the results of measurements on the same object on an atomic force microscope. 相似文献
20.
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. 相似文献