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1.
Results of numerical calculations of the flow in a double-diaphragm shock tube with a tailored contact surface are reported.
The calculations were carried out using a model of an ideal shock tube allowing for the real properties of the driver gas
at high pressures and equilibrium thermodynamics of the processes behind the shock waves at Mach numbers M
s1 of the shock wave in the working gas varying in the range 5–25. Flow regimes with a tailored contact surface were obtained
for Mach numbers M
s1=6.3, 11, and 15 using the double-diaphragm shock tube at the Ioffe Physicotechnical Institute. Under these conditions, the
parameters of the working gas were kept constant for more than 1 ms. The calculated data were compared with the experimental
results and it was shown that the calculated data may be used to determine the section lengths in a double-diaphragm shock
tube and to estimate its operating time. The calculated values of the initial pressure in the sections of the tube were substantially
lower than those achieved experimentally. Measurements were made of the static pressure along the axis of a conical nozzle
during the expansion of hydrogen (initial temperature T
0=293 K) and shock-heated nitrogen (T
0=4000 K). It is found that the expansion of hydrogen is accompanied by deactivation of the rotational degrees of freedom,
and that partial freezing of the vibrational degrees of freedom takes place in the nitrogen stream.
Zh. Tekh. Fiz. 67, 88–95 (November 1997) 相似文献
2.
E. E. Baranov A. M. Emel’yanov W. V. Lundin V. N. Petrov V. I. Sakharov I. T. Serenkov N. A. Sobolev A. N. Titkov E. I. Shek N. M. Shmidt 《Technical Physics》2006,51(12):1600-1603
The evolution of the structure organization of MOCVD-grown AlGaN/GaN superlattices subjected to erbium ion implantation with an energy of 1 MeV and dose of 3 × 1015 cm?2 and subsequent annealing is correlated with their photoluminescent properties. The structure organization is quantitatively estimated using parameter Δ (degree of violation of local symmetry), which is found via multifractal analysis of surface morphology patterns obtained with atomic force microscopy. It is shown that the implantation not only causes Ga segregation on the surface, but also changes the structure organization, which shows up in the finer grain structure compared with the starting one and disordering, as well as in an increase in Δ. As the annealing temperature rises from 700 to 800°C, Δ declines, indicating that the structure organization is improved, and the intensity of the dominating photoluminescence peak due to Er3+ ions (1.542 μm) grows. With a further increase in the annealing temperature to 1050°C, the structure organization degrades, domains get larger, voids 100–200 nm deep form, and the photoluminescence intensity drops. The formation of voids during high-temperature annealing is also substantiated by data for 230-keV proton scattering. It is thus established that the improvement of the superlattice structure organization activates erbium and causes the erbium-ion-related luminescence intensity to grow. 相似文献
3.
The use of molar refractions is insufficient to describe the retention volumes and thermodynamic functions of solutions in nonpolar stationary phases. The heats of dissolution of monofunctional derivatives of the alkanes are proportional to the polarizability and inversely proportional to the sixth power of the van der Waals' radius of the interacting particles. The heat of dissolution of substances being analyzed, with the same number of carbon atoms, in aromatic solvents depends on the conditions of contact between the molecules of the substances being analyzed and the benzene rings of the solvent. The order of the heats of dissolution of substances being analyzed in different nonpolar solvents does not remain the same, indicating that the theory of regular solutions cannot be applied to these systems. To determine the order of the heats of dissolution of isomers in nonpolar stationary phases it is necessary to take account of the electron density distribution in the molecules of the reacting substances and the probability of molecular arrangement for the most favorable interaction. 相似文献
4.
Garcia Ruano JL Alemparte C Martin Castro AM Adams H Rodriguez Ramos JH 《The Journal of organic chemistry》2000,65(23):7938-7943
The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles. 相似文献
5.
V. G. Pimenov E. E. Sheveleva A. M. Sakharov 《Russian Journal of Physical Chemistry B, Focus on Physics》2012,6(7):786-792
Experience of constructing an original installation for supercritical drying of polymer gels and operating it are described in detail. A particular attention is paid to the preparation of anhydrous carbon monoxide. The effectiveness of the designed equipment in producing aerogel samples of different chemical natures is demonstrated. 相似文献
6.
EI Rodriguez Martinez CI Barriga-Paulino MI Zapata CC Chinchilla AM López-Jiménez CM Gómez 《BMC neuroscience》2012,13(1):104-23
ABSTRACT: BACKGROUND: The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). RESULTS: The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0--20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. CONCLUSIONS: The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages. 相似文献
7.
8.
V. A. Viktorov N. P. Mende A. B. Podlaskin P. A. Popov V. A. Sakharov 《Technical Physics》2010,55(6):795-798
A method is proposed for identifying the aerodynamic characteristics of a model the flow about which varies considerably in
the course of motion. In this method, the trajectory of the model is split into sections with different types of the flow
and then similar data from these sections are collected into groups and processed. The aerodynamic characteristics are identified
by the method of successive approximation using a differential correction algorithm. The accuracy of the results is analyzed. 相似文献
9.
S. V. Bobashev Yu. P. Golovachov N. P. Mende P. A. Popov B. I. Reznikov V. A. Sakharov A. A. Schmidt A. S. Chernyshev S. Z. Sapozhnikov V. Yu. Mityakov A. V. Mityakov 《Technical Physics》2008,53(12):1634-1635
The surface temperature of a model body of revolution placed in a pulsed supersonic nitrogen flow is measured with the help of a gradient heat flux sensor. From the measured temperature, a heat flux toward the surface of the body is determined. The steady flow of a viscous transcalent gas about the body is numerically calculated. The results of the numerical calculation and measuring data are in good agreement. 相似文献
10.
Fujiwara M Akimune H van Den Berg AM Cribier M Daito I Ejiri H Fujimura H Fujita Y Goodman CD Hara K Harakeh MN Ihara F Ishikawa T Janecke J Kawabata T Raghavan RS Schwarz K Tanaka M Yamanaka T Yosoi M Zegers RG 《Physical review letters》2000,85(21):4442-4445
Discrete Gamow-Teller (GT) transitions 176Yb-->176Lu at low excitation energies have been measured via the ( 3He,t) reaction at 450 MeV and at 0 degrees. For 176Yb, two low-lying states are observed, setting low thresholds Q(nu) = 301 and 445 keV for neutrino ( nu) capture. Capture rates estimated from the measured GT strengths, the simple two-state excitation structure, and the low Q(nu) in Yb-Lu indicate that Yb-based nu detectors are well suited for a direct measurement of the sub-MeV solar electron-neutrino ( nu(e)) spectrum including pp neutrinos. 相似文献