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排序方式: 共有306条查询结果,搜索用时 13 毫秒
1.
In the framework of joint effort between the Nuclear Energy Agency (NEA) of OECD, the United States Department of Energy (US DOE), and the Commissariat a l'Energie Atomique (CEA), France a coupled three-dimensional (3D) thermal-hydraulics/neutron kinetics benchmark for VVER-1000 was defined. The benchmark consists of calculation of a pump start-up experiment labelled V1000CT-1 (Phase 1), as well as a vessel mixing experiment and main steam line break (MSLB) transient labelled V1000CT-2 (Phase 2), respectively. The reference nuclear plant is Kozloduy-6 in Bulgaria. The overall objective is to assess computer codes used in the analysis of VVER-1000 reactivity transients. A specific objective is to assess the vessel mixing models used in system codes. Plant data are available for code validation consisting of one experiment of pump start-up (V1000CT-1) and one experiment of steam generator isolation (V1000CT-2). The validated codes can be used to calculate asymmetric MSLB transients involving similar mixing patterns. This paper summarizes a comparison of CATHARE and TRAC-PF1 system code results for V1000CT-1, Exercise 1, which is a full plant point kinetics simulation of a reactor coolant system (RCS) pump start-up experiment. The reference plant data include integral and sector average parameters. The comparison is made from the point of view of vessel mixing and full system simulation. CATHARE used a six-sector multiple 1D vessel thermal-hydraulic model with cross flows and TRAC used a six-sector, 18-channel coarse-mesh 3D vessel model. Good agreement in terms of integral parameters and inter-loop mixing is observed. 相似文献
2.
Lubomir V. Kolev 《Reliable Computing》2006,12(3):193-202
Recently, a direct method for outer solution of linear parametric systems has been suggested for the general case where the
elements of the system are nonlinear functions of independent interval parameters. In this paper, an improvement of the method
is introduced which may lead to a narrower outer solution. 相似文献
3.
Glass-infiltrated alumina is now commonly used as a core material in dental restorations. If the veneer layer, which covers the core, is broken or damaged through use, a direct contact between the core and the opposing restorative material or human enamel can occur. The wear behavior in simulated contacts with human enamel has already been studied. In the present work, we have investigated the wear mechanisms of glass-infiltrated alumina in contact with a high-purity alumina as an opposing ceramic restoration. Wear tests were performed in a pin-on-disk tribometer under conditions that roughly resemble those in the oral environment. The wear rates of the alumina balls and the glass-infiltrated disks sliding in water increased linearly with load. No wear transition (i.e., a sudden increase in wear) was observed as either the load or the sliding distance was increased. Examination of the wear debris in the SEM suggested the presence of wear particles that are often attributed to the formation of hydrated aluminum oxide through tribochemical reactions between water and alumina. While tribochemical wear was the dominating wear mechanism for the alumina balls, microfracture and delamination governed the wear behavior of the glass-infiltrated alumina disks. Examination of the surface layers formed on the disk wear tracks confirmed the presence of amorphous hydrated alumina on the wear track. It is suggested that these reaction products smear on the wear track filling the pores produced by microfracture and delamination. The high wear resistance of glass-infiltrated alumina is attributed to the presence of hydrated alumina in the third body layer that accommodates the interfacial shear stresses and the high strength due to strong bonding between the glass phase and alumina grains. Based on the observed wear resistance of glass-infiltrated alumina in the present study, this material should be evaluated for applications in addition to dental restorations. 相似文献
4.
The characterisitics of the development of helium porosity in bcc and fcc alloys and structural steel after irradiation with
40-keV He+ up to dose 5⋅1020 m−2 at 20°C and subsequent annealing at 650°C for 1 h and 5 h are studied by transmission electron microscopy. It it found that
under these conditions smaller bubbles with high density are formed in bcc than in fcc materials. It is shown that for an
annealing time of 5 h higher porosity is formed in all materials, except nickel, than with 1 h annealing. This is due to the
inflow of thermal vacancies from the free surface. The data obtained are discussed from the standpoint of the formation of
various helium-containing complexes, their thermal stability, and the diffusion mobility of the matrix atoms.
__________
Translated from Atomnaya Energiya, Vol. 99, No. 2, pp. 115–120, August 2005. 相似文献
5.
In this paper the problem of finding the set of all real solutions to a system of n non-linear equations contained in a given n-dimensional box (the global solution problem) is considered. A new method for solving the global solution problem is suggested. It is based on a transformation of the original system into a larger system of separable form. The global solution of the latter system is then found in a most efficient manner by a new interval method which exploits the separabily property. Numerical examples illustrating the efficiency of the method suggested are provided. 相似文献
6.
The tribological performance of DLC coatings under oil-lubricated fretting conditions 总被引:1,自引:0,他引:1
Whether or not the process of fretting occurs is to a large extent dependent on the coefficient of friction, because the coefficient of friction directly affects the amount of shear stress. As a result, the key factor when it comes to reducing the amount of fretting damage is to reduce the coefficient of friction. Various surface coatings, and especially hard, diamond-like carbon (DLC) coatings, are known to be able to produce surfaces with a low level of friction. Despite some such attempts in the past, which did not result in major improvements, the developments and improvements in DLC coatings in recent years suggest the need for a re-evaluation of these coatings for fretting applications. Another way to reduce the amount of friction in mechanical components is to apply lubricants, and recent studies on the lubrication of DLC coatings suggest that this combination could be very successful in preventing failures under boundary-lubrication conditions. Therefore, in this work we present the results of friction and wear measurements from three types of fretting contacts: steel/steel, steel/DLC and DLC/DLC. Boundary oil-lubrication conditions were investigated and a wide range of displacement amplitudes, i.e., from 25 to 500 μm, were selected to assess the fretting and sliding behaviours. The results show a significant difference between the fretting and sliding regimes. In the fretting regime, the DLC-containing contacts, and especially the self-mated DLC/DLC contacts, performed much better than the steel/steel contacts, and significantly reduced both the wear (a 3–10 times reduction with steel/DLC and DLC/DLC) and the friction (a more-than-two-times reduction with DLC/DLC). In the sliding regime, the lubrication effects governed the tribological performance, making the results for all three material combinations very similar. 相似文献
7.
Falgout R. D. Friedhoff S. Kolev Tz. V. MacLachlan S. P. Schroder J. B. Vandewalle S. 《Computing and Visualization in Science》2017,18(4-5):123-143
Computing and Visualization in Science - We consider the comparison of multigrid methods for parabolic partial differential equations that allow space–time concurrency. With current trends in... 相似文献
8.
T. Koutzarova S. Kolev I. Nedkov K. Krezhov D. Kovacheva B. Blagoev C. Ghelev C. Henrist R. Cloots A. Zaleski 《Journal of Superconductivity and Novel Magnetism》2012,25(8):2631-2635
We studied the magnetic properties of nanosized Ba2Mg2Fe12O22 powder obtained by citrate auto-combustion synthesis. The powder consists of agglomerates with mean crystallite size of 100?nm. The magnetic properties of the powder were investigated at 4.2?K and at room temperature. The values measured of the magnetization M at a magnetic field of 60?kOe are 22.78?emu/g and 30.47?emu/g at room temperature and 4.2?K, respectively. The magnetic phase transition at 183 K is related to the ferromagnetic-to-spiral spin order and is a precondition for this material??s exhibiting multiferroic properties. 相似文献
9.
B. A. Kalin A. G. Bogachev I. I. Chernov S. I. Korshunov I. V. Reutov 《Atomic Energy》1992,73(3):723-729
Moscow Engineering Physics Institute. Translated from Atomnaya Énergiya, Vol. 73, No. 3, pp. 203–209, September, 1992. 相似文献
10.
Lubomir V. Kolev 《Reliable Computing》2007,13(6):445-466
A method for determining the positive definiteness margin of interval matrices is suggested. It is based on the use of outer
interval bounds on the solution set of an interval eigenvalue problem. Three algorithms of the method are developed. It is
shown that their numerical complexity is polynomial. Numerical examples illustrating the applicability of the method suggested
are provided. 相似文献