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1.
Two metallic 240Pu sources were certified as reference standards of spontaneous-fission activity and neutron flux. The certification results were used to determine the ratio T αT s&f
of the alpha-decay and spontaneousfission half-lives of 240Pu. The ratio was found to be (5.68+-0.11)·10 −8, which corresponds to T s&f
=(1.16+0.02)·1011 yr for an assumed value T α=6563+7yr.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 57–58, February, 1995. 相似文献
2.
The law of corresponding states is studied for the coefficients of shear η* S and volume η* V viscosities of classical liquids (Ar, Kr, Xe, O 2, N 2, CH 4); the analytical expressions are derived on the basis of kinetic equations for one- and two-particle distribution functions. The reduced iso-frequency coefficients Φ(| r|) and g(| r|) for liquid Ar, Kr, Xe, O 2, N 2, and CH 4 are numerically calculated in a wide range of variations at the reduced temperatures T* and densities ρ*, which satisfy the law of corresponding states, at a definite choice of the intermolecular interaction potential η S * and radial distribution function η V *. 相似文献
3.
We have recently conjectured within the framework of the approximate mean-field formalism a cooling process on adiabatic demagnetization of antiferromagnetic systems from accessible initial paramagnetic states of entropy S
i
, applied external uniform constant magnetic field strength H
i
, and temperature T
i
, to paramagnetic final states of coordinates S
f
S
i
, H
f
H
c
, and T
f
< T
c
(0) or TT
c
(0). Here T
c
(0) is the spontaneous critical ordering temperature of the system in the absence of magnetic field, and H
c
is its critical internal magnetic field strength arising from the relevant fundamental interactions between its constituent particles or spins, which prevents it at all temperatures from undergoing its ordering transformation. In the present work, the above conjecture acquires solid foundation through the exact formalism at very low temperatures of the paramagnetic phase of magnetized, anisotropic, spin –12 systems subject to antiferromagnetic Ising interactions.Work performed under the auspices of U.S. ERDA. 相似文献
4.
According to the phenomenological model of nucleation of a fatigue macrocrack, the process is considered as a two-parameter
process. The process is described by the local stress or strain range and a certain linear parameter of the material. We propose
the corresponding parameters, namely, the local stress range Δσ
y
*
and the characteristic size d
* of the prefracture zone. The formation of this zone is caused by the anomaly of the yield strength of the material in subsurface
layers, the microstructure, the loading amplitude, the cyclic strain hardening, and the environment. The quantity d
* is a constant of the material, which is independent of the geometry of notch and specimen. the boundary of the prefracture
zone is considered as a macrobarrier that determines the growth of microstructurally short and physically small cracks. The
moment when a physically small crack oversteps the boundary of the prefracture zone is defined by the quantitative criterion
( a
0= d
*) of the initial size a
0 of a macrocrack in the material. The proposed dependences of (Δσ
y
*
, N
i
), N
i
) and ( d
*, N
i
) can be regarded as a basis for the determination of characteristics of resistance of the material to the nucleation of a
fatigue macrocrack.
Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv,
Vol. 34, No. 1, pp. 7–21, January–February, 1998. 相似文献
5.
Coprecipitation of 233U, 239Pu, 241Am, 152Eu, 90Sr, 90Y, and 60Co on chitosans of various molecular weights (MW) was studied. Low-molecular-weight chitosan (LMWC) with MW of 5 kDa (5 ×
10 3 g mol −1) proved to be a more effective coprecipitant than high-molecular-weight chitosan (HMWC) with MW of 700 kDa (7 × 10 5 g mol −1). With HMWC, the degree of coprecipitation (α) was 80% for 152Eu and 90Y, 99% for 233U and 241Am, and 85% for 239Pu. For 60Co, α monotonically increased with an increase in the chitosan concentration in solution and reached 40% at [HMWC] = 5 g l −1. For 90Sr, α did not exceed 3% in the entire examined range of chitosan concentrations. With LMWC, the α values for An, 152Eu, and 90Y differed insignificantly (92–99%). For 60Co and 90Sr, α increased to 40% in the range of chitosan concentrations from 0 to 1 g l −1. The presence of inorganic salts in solution considerably decreases α of UO 22+ with chitosans but does not noticeably affect the behavior of Am, Pu, and Eu. The effect of salts on the efficiency of 233UO 2/2+ coprecipitation on HMWC decreases in the order Na 2SO 4 > NaCl > Na 2CO 3 > NaNO 3 > Na 3PO 4. Based on the results obtained, a procedure suitable for expedition conditions was developed for preconcentration of Pu from
seawater on chitosan, with simultaneous separation of Pu from U, for radioecological monitoring of natural waters. The specific
activity of Pu in samples of near-bottom seawater of gulfs of the Novaya Zemlya archipelago was (150–170) ± 20 mBq m −3. The results are well consistent with the published data. 相似文献
6.
The parameters of interatomic interaction in diamonds of 12C and 13C isotopes are determined. The parameters are determined by two methods, namely, from the elastic modulus (potential no. 1) and from the sublimation energy at T = 0 K (potential no. 2). Based on these parameters, the Debye model is used to calculate the isobaric temperature dependences of the thermoelastic properties for isotopically different diamonds, namely, the coefficient of thermal expansion (CTE), the density, the elastic modulus B T , and the specific heat capacity. It is demonstrated that the best agreement with the experimentally obtained dependences of the foregoing parameters is obtained when potential no. 1 is used in calculations. The values of CTE, density, and heat capacity increase in the case of transition from 12C diamond to 13C diamond. It is demonstrated that the inequality B T ( 12C) < B T ( 13C) is valid at T = 0 K, which is associated with the reduction of interatomic spacing in the case of transition from 12C diamond to 13C diamond. However, as the temperature increases, the volumetric isotopic effect in diamond decreases. It is found that the B T ( T) dependences for 12C and 13C diamonds intersect at a temperature below the Debye temperature. Therefore, at high temperatures, the elastic modulus for light-isotope diamond comes to exceed that for heavy-isotope diamond, B T ( 12C) > B T ( 13C). Experimental results are given which confirm this effect. The variation of the properties of isotopically different diamonds with increasing pressure is discussed. 相似文献
7.
In this work release isentropes of shocked porous molybdenum were investigated. Samples with an initial porosity m = ρ 0/ρ = 1.4 and 3.1 were studied to achieve near-critical entropy states of metal after shock compression. Compressed samples
were expanded into helium with different initial pressures. The brightness temperature of the metal and the helium shock wave
velocity were measured with a fast multichannel pyrometer. The helium shock wave velocity was used to determine the final
pressure ( PS) of expansion of the metal and the velocity of metal expansion ( WS). Location of peculiarities on the PS– WS and PS– TP curves of the isentropes gives the location of their entrance into the two-phase region. Estimation of the molybdenum critical
temperature and pressure was carried out on the basis of the experimental data.
Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A. 相似文献
8.
The kinetics of decomposition of -goethite were investigated, under vacuum conditions, in the temperature range 170–250° C. The experimental thermogravimetric traces were interpreted according to the shrinking core model for cylindrical particles. The Arrhenius plot of InK (kinetic constant) against 1/ T yielded an activation energy of 119±9 kJ mol –1 at 210° C. The highest specific area, S
BET=118.4±5.5 m 2 g –1, of the reaction product -hematite, was obtained by decompsition at 225° C. Information about the formation of micropores and their evolution with temperature was also obtained. 相似文献
9.
The Knudsen effusion method with mass-spectrometric analysis of evaporation products is used to determine the composition and pressure of saturated vapor over liquid lithium in the temperature range from 627 to 893 K. The Li(l) = Li(g), 2Li(l) = Li 2(g), and Li 2(g) = 2Li(g) reactions are investigated. The measured values of partial pressure for Li and Li 2are used to calculate the values of enthalpy for these reactions at 0 K by the second,
r
H
0
0(II), and third,
r
H
0
0(III), laws of thermodynamics:
r
H
0
0(II) = 157.9 ± 0.5, 214.2 ± 0.6, and 101.4 ± 1.1 kJ/mol, and
r
H
0
0(III) = 157.5 ± 0.3, 213.9 ± 0.3, and 101.1 ± 0.6 kJ/mol, respectively. 相似文献
10.
Abstract The effect of the reagent ratio, reaction time and power of the reagent on the product composition in chlorination of [60]fullerene was studied. Chlorofullerenes C 60Cl 6, C 60Cl 8, C 60Cl 10, C 60Cl 12, C 60Cl 14, and C 60Cl 26 were synthesized and characterized by chemical analysis, FTIR, 13C NMR, and MALDI TOF mass spectrometry. The experimental data supported the coexistence of several isomers of C 60Cl n ( n = 8, 10, 12, 14, 26); the mixtures were not separated so far. Semiempirical calculations (AM1, PM3) were used to analyze the addition patterns and resulted in the most favorable structures of C 60Cl 8–26. Chlorination of C 70 under various conditions invariably yielded C 70Cl 10. 相似文献
11.
The method of polarization resistance is extensively used for the determination of the rate of corrosion. At the same time, the accuracy of measurements of the corrosion rate performed with industrial corrosion meters is often not estimated. By using an indicator, we find the accuracy of the measurements of the corrosion rate for 20 steel placed in 1N H 2SO 4 and 0.01N Na 2SO 4 solutions and for 12Kh18N10T steel placed in 1N and 10N H 2SO 4 solutions.Kiev Polytechnic Institute, Kiev. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 31, No. 3. pp. 22–27, May–June, 1995. 相似文献
12.
In this paper a c-sample slippage analogue of the Wilcoxon [11] test is considered. Given a sample of size n for each of c populations, the test rejects the hypothesis that the c populations are identical when max 1≤i≤c σ k r ik > λ, where r i1, …, r in are the ranks of the observations from the i-th population in the combined sample of size cn. The small and large sample distributions of the test statistic are derived. Tables of the exact distribution are given for c = 2(1)5, n = 2(1)5. Tables of critical values are given for c = 2(1)6, n = 2(1)8 for values of α = 0.001, 0.005, 0.01, 0.025, 0.05, 0.10, and 0.20. 相似文献
13.
The deterioration of ambient air quality is one of the emerging environmental problems in developing countries of South Asia. Unplanned urbanization, population growth, degradation of vegetation cover and industrial and vehicular emissions, particularly in urban areas, have resulted in substantial rise in the level of air pollutants and emission sources. This study focused on monitoring of different cities as per traffic volume and flow. Air quality monitoring was conducted on hourly basis to determine the major parameters; i.e. PM10, NOx, SO2, CO by using fixed station for 8 h from 1:30 pm to 9:30 pm. All the measuring values were then compared with the National Environment Quality Standards (NEQS) and Air Quality Index (AQI). Results revealed that the concentration of PM10 at the selected areas of these cities ranged from 156 to 390 μg/m3, CO ranged from 1.18 to 6.01 mg/m3, and NOx ranged from 32.65 to 129.47 μg/m3. It was evident that all these concentration had been higher than the permissible limits of NEQS, whereas only SO2 was found within the permissible limits (15.60–110.52 μg/m3). Air Quality Index (AQI) of all the designated points of cities was also assessed, and most of the vehicular and commercial areas had shown unhealthy and severe conditions ranging from 191 to 320, respectively. 相似文献
15.
We present results of a theoretical and experimental investigation of submerged gas jets in the range of density variations (
j/
e=0.05–10).Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 4, pp. 715–720, April, 1979. 相似文献
16.
The present study was undertaken with a view to an accelerated testing method which would permit prediction of standard compressive
strength of cement within 24 hours at most. Test specimens were 11.3×11.3 mm dry cement cylindrical compacts (average porosity
22.6% and 26.8%) cured, for 24 hours at 21°C or for 3 hours at 100°C, in distilled water or in a super-satured lime solution.
A linear relation was established between the cement and the compact strength for all the four curing regimes studied. The
24 hour curing in distilled water at 21°C, however, was considered preferable, permitting strength prediction within ±11.5
kg per sq.cm at 95% confidence level. Further study on cements with a wider range of properties will be needed, however, before
the method can be recommended as a substitute for current standard procedures.
Résumé On a entrepris cette étude en vue d'obtenir une méthode d'essais accélérés qui permettrait de prédire dans un délai de24 heures au plus la résistance normale en compression du ciment. Les éprouvettes étaient des agglomérés de ciment sec (porosité
moyenne: 22,6 et 22,−%) conservés24 heures à21°C ou3 heures à100°C, dans de l'eau distillée ou dans une solution de chaux sursaturée. On a établi une relation linéaire entre le ciment et
la résistance à l'état compacté pour les4 régimes de conservation étudiés. Il est apparu que la conservation de24 heures en eau distillée à21°C était préférable, permettant de prédire la résistance à+ou −11,5 kg/cm2 près pour une crédibilité de 95%. D'autres études sur les ciments portant sur une gamme plus large de propriétés seraient
cependant nécessaires avant que la méthode puisse être recommandée comme un substitut des méthodes normales ordinaires.
相似文献
17.
We investigated systems of steel 20 with nickel and zinc coating in a 3% NaCl solution, distilled water, and a 45 · 10 −3% H 2SO 4 + 0.14 H 2O 2 + 5 · 10 −6% K 2Cr 2O 7 solution using capillary probes filled with these environments. After their use, errors in measurements in the volume of
the electrolyte are absent. The low conductance of the electrolyte and the dissolution of the metal in the active state are
necessary conditions for adequate measurements of local electrode potentials. It is established that the accuracy of local
microelectrochemical measurements in an electrolyte drop is higher than that in an electrolyte film.
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 3, pp. 126–129, May–June, 2008. 相似文献
18.
The cubic MnCo 2O 4 was prepared by calcining MnCO 3-2CoCO 3?1.5H 2O above 600 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometer. The result showed that high-crystallized MnCo 2O 4 with cubic structure [space group Fd-3m(227)] was obtained when the precursor was calcined above 600 °C in air for 6 h. Magnetic characterization indicated that cubic MnCo 2O 4 behaved weak magnetic behavior at room temperature. The thermal process of the precursor in air experienced three steps, which are: first, the dehydration of 1.5 water molecules, then the decomposition of MnCO 3-2CoCO 3 into cubic MnO 2 and cubic Co 3O 4, and at last the reaction of MnO 2 with Co 3O 4 into cubic MnCo 2O 4. Based on the KAS equation, the values of the activation energies associated with the thermal process of MnCO 3-2CoCO 3?1.5H 2O were determined. 相似文献
19.
The present recommendation defines a method for measuring the time-dependent strain in hardened concrete specimens that are
either load-free or are subjected to a uniform compressive force kept constant over a long period. It states the definitions
of autogenous shrinkage and drying shrinkage, basic creep and drying creep, instantaneous strain at a given age, and recovery.
It gives the specifications for testing and measuring devices and describes, in an appendix, three types of apparatus for
creep tests. The present recommendation applies to the case of concretes containing light, normal, and heavy aggregates, when
the maximum size of these aggregates does not exceed 50 mm.
The draft of this document has been prepared by the members of Subcommittee 4: Standardized Test Methods for Creep and Shrinkage:
Paul Acker (Chairman), Z.P. Bažant, J. C. Chern, C. Huet, F.H. Wittmann. Also consulted were: F. Alou, G. Fagerlund, T.C.
Hansen, M. Mamillan, P. Schwesinger, F. Ulm.
The text presented hereunder is a draft for general consideration. Comments should be sent to the TC Chairman, Prof. Zdeněk
P. Bažant, Northwestern University, WP Murphy Professor of Civil Engineering, 2145 Sheridan Road, A131, Evanston, IL 60208,
USA, Fax: +1 847 467 1078, e-mail: z-bazant@nwu.edu before April 1, 1999.
TC MEMBERSHIP: Chairman: Zdeněk P. Bažant, USA; Secretary: Bernard Espion, Belgium; Members: Paul Acker, France; Luis Agullo, Spain; Michel Auperin, France; Ignacio Carol, Spain; Domingo J. Carreira, USA; Jose M.
R. Catarino, Portugal; Jenn-Chuan Chern, Taiwan; Mario A. Chiorino, Italy; John W. Dougill, UK; Christian Huet, Switzerland;
Terje Kanstad, Norway; Jin-Keun Kim, Korea; Vladimir Kristek, Czech Republic; Harold S. Muller, Germany; Byung Hwan Oh, Korea;
Josko Ozbolt, Germany; Stuart Reid, Australia; H. W. Reinhardt, Germany; Peter Schwesinger, Germany; Bretislav Teply, Czech
Republic; Heinrich Trost, Germany; Tatsuya Tsubaki, Japan; R. F. Warner, Australia; Folker H. Wittmann, Switzerland; Yunping
Xi, USA; J. F. Young, USA. 相似文献
20.
A well-defined condition, determining the values of the aperture angles of a fusing wedge, is presented for exact solutions of the single-phase problem of a fusing wedge that were obtained earlier and are written for these values. The critical orientation of the fusing wedge to the axis of fusion when the written solution degenerates is indicated.Notation , ,
n
,
n
,
n
A
1, A
2, B
auxiliary variables
-
P
n
, Q
n
, S
n
, T
n
polynomials
-
k, m, n, i
natural numbers
- ,
k
angles between the normals to the surfaces forming the fusing wedge
-
z
the axis in a Cartesian coordinate system
-
U
temperature at points of the body infinitely remote from the fusing boundary
Voronezh Institute of Technology, Voronezh, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 6, pp. 750–753, June, 1994. 相似文献
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