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141.
Donetsk Scientific-Research Institute of Ferrous Metallurgy (DonNIIchermet). Ministry of Metallurgy of the USSR. Translated from Metallurg, No. 4, pp. 37–39, April, 1990. 相似文献
142.
S. S. Moiseev V. A. Petrov S. V. Stepanov 《International Journal of Thermophysics》1990,11(3):587-596
Radiation transfer in highly scattering ceramics is described by a diffusion approximation based on the asymptotic relation of the radiant flux and the radiant energy density in material depth. In this approximation, a calculation of the effective absorption coefficient k and the radiation diffusion coefficient D is based on the measurement of normal-hemispherical transmission of specimens shaped as various-thickness disks. Taken into account are radiation field, twodimensionality, and the radiation boundary reflection effect. The optical property measurements have been performed on the experimental apparatus based on an integrating sphere, a collimated radiation source, and a twochannel data acquisition and processing system. Results of the measurements of k and D for the silica ceramic are given at room temperature. 相似文献
143.
A. N. Alekseev S. B. Aleksandrov A. É. Byrnaz L. É. Velikovskii I. É. Velikovskii D. M. Krasovitskii M. V. Pavlenko S. I. Petrov Yu. V. Pogorel’skii I. A. Sokolov M. A. Sokolov M. V. Stepanov A. G. Tkachenko A. P. Shkurko V. P. Chalyi 《Technical Physics Letters》2005,31(10):864-867
The results of the optimization of the ammonia MBE technology of AlN/AlGaN/GaN/AlGaN heterostructures for high-power microwave field-effect transistors (FETs) are presented. The creation of technological systems of the EPN type for the deposition of group III nitrides by ammonia MBE, in combination with the development of optimum growth and postgrowth processes, make it possible to obtain AlN/AlGaN/GaN/AlGaN based heterostructures for high-power microwave FETs with the output static characteristics on the world best level. One of the main fields of application of the semiconductor heterostructures based on group III nitrides is the technology of high electron mobility transistors (HEMTs). Most investigations in this field have been devoted to the classical GaN/AlGaN structures with a single heterojunction. An alternative approach based on the use of double heterostructures with improved two-dimensional electron gas (2DEG) confinement offers a number of advantages, but such structures are usually characterized by a lower carrier mobility as compared to that in the single-junction structures. We succeeded in optimizing the double heterostructure parameters and growth conditions so as to obtain conducting channels with a 2DEG carrier mobility of 1450, 1350, and 1000 cm2/(V s) and a sheet electron density of 1.3 × 1013, 1.6 × 1013, and 2.0 × 1013 cm?2, respectively. Experimental HEMTs with 1-μm-long gates based on the obtained multilayer heterostructure with a doped upper barrier layer exhibit stable current-voltage characteristics with maximum saturation current densities of about 1 A/mm and a transconductance of up to 180 mS/mm. 相似文献
144.
The problems involved in further improving the system of metrological facilities in the manufacture and operation of water meters are formulated. 相似文献
145.
Restriction fragment length polymorphism (RFLP) of the apolipoprotein B locus was investigated in the population of Tomsk. The frequencies of alleles and haplotypes of polymorphic restriction sites XbaI, MspI, and EcoRI were determined. The parameters of linkage disequilibrium and polymorphism information content (PIC) were estimated. Comparative data on various regions of the world are shown. 相似文献
146.
147.
The behavior of multi- and single-wavelength distributed feedback fiber lasers is simulated in a comprehensive dynamic model. The evolution of the spatial distribution of gain, saturation-induced gain gratings, and spontaneous emission is taken into account. Stability and relative intensity noise (RIN) of the different laser types and laser modes are compared, and the effect of varying degree of pump RIN and quenching of spontaneous emission lifetimes is analyzed 相似文献
148.
Metal-nanoparticle-containing composite layers were synthesized by implantation of 60 keV Ag+ ions into a soda-lime silicate glass to a dose of 3×1016 ion/cm2 at an ion beam current density of 3 μA/cm2 and a substrate temperature of 35°C. The results of implantation depend on the temperature effects developed in the glass targets of various thicknesses. Data on the silver distribution profile and the nucleation and growth of metal nanoparticles in depth of the implanted layers were obtained from the optical reflection spectra. It is demonstrated that even small variations in the surface temperature of the ion-bombarded glass substrate lead to significant changes in the conditions of nanoparticle formation in the sample. 相似文献
149.
A. Shah E.v Stepanov A. Hiltner E. Baer M. Klein 《International Journal of Fracture》1997,84(2):159-173
Correlation in mechanisms and kinetics of step-wise fatigue crack propagation in polyethylene pipe specimens of different
geometries is studied experimentally. It is shown that crack propagation in a non-standard specimen cut from a real pipe and
conserving the pipe geometry can be effectively simulated using a standard compact tension specimen. Good correlation in both
kinetics of step-wise crack propagation and fractography between the specimens is achieved if experimental conditions are
chosen to assure equal values of (a) stress intensity factor and (b) stress intensity factor gradient at the initial notch
tips. These results extend previous technique of fatigue accelerating slow crack growth used to predict lifetime of polyethylene
pipes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
150.