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排序方式: 共有953条查询结果,搜索用时 15 毫秒
1.
Ponnusamy Nandha Kumar Shangavi Subramanian Uthirapathy Vijayalakshmi Sanjeevi Kannan 《Journal of the American Ceramic Society》2020,103(6):3528-3540
Structurally stable β-Ca3(PO4)2/t-ZrO2 composite mixtures with the aid of Dy3+ stabilizer were accomplished at 1500°C. The precursors comprising Ca2+, P5+, Zr4+, and Dy3+ have been varied to obtain five different combinations. The results revealed the fact that complete phase transformation of calcium-deficient apatite to β-Ca3(PO4)2 occurred only at 1300°C, whereas the evidence of t-ZrO2 crystallization is obvious at 900°C. The dual occupancy of Dy3+ at β-Ca3(PO4)2 and t-ZrO2 structures was evident; however, Dy3+ initially prefers to occupy β-Ca3(PO4)2 lattice until its saturation limit and thereafter accommodates at the lattice site of ZrO2. The typical absorption and emission behavior of Dy3+ were noticed in all the systems and, moreover, the surrounding symmetry of Dy3+ domains has been determined from the luminescence study. All the systems ensured paramagnetic response that is generally contributed by the presence of Dy3+. A gradual increment in the phase content of t-ZrO2 in the composite mixtures ensured a significant improvement in the hardness and Young's modulus of the investigated compositions. 相似文献
2.
In this paper, we present a method for blind separation of co-channel BPSK signals arriving at an antenna array. This method consists of two parts: the maximum likelihood constellation estimation and assignment. We show that at high SNR, the maximum likelihood constellation estimation is well approximated by the smallest distance clustering algorithm, which we proposed earlier on heuristic grounds. We observe that both these methods for estimating the constellation vectors perform very well at high SNR and nearly attain Cramer-Rao bounds. Using this fact and noting that the assignment algorithm causes negligible error at high SNR, we derive upper bounds on the probability of bit error for the above method at high SNR. These upper bounds fall very rapidly with increasing SNR, showing that our constellation estimation-assignment approach is very efficient. Simulation results are given to demonstrate the usefulness of the bounds 相似文献
3.
M. D. Kannan Sa. K. Narayandass C. Balasubramanian D. Mangalaraj 《Journal of Materials Science》1992,27(18):5040-5044
Aluminium-neodymium oxide-aluminium thin film capacitors have been prepared by thermal evaporation and the d.c. conduction properties of these films have been studied. The thicknesses of the films have been determined by a multiple beam interferometer. The current-voltage power-law dependence showed that the conduction in these films is space-charge limited. The linear dependence of the current density on the square root of the applied field confirmed the exponential trap distribution. The trap density has been found to be of the order of 1026 m–3. It has also been observed that the Schottky type of conduction is predominant in the high-field region and the height of the Schottky barrier has been determined. It is seen that the conduction mechanism is an activated process with the activation energy decreasing with increasing field. 相似文献
4.
A family of energy/economic/environmental (E3) models is presented as a mechanism for analysing national policy issues. The family consists of discrete models which are designed to be run in an integrated manner. The outputs of certain models provide the inputs to the next. This structure allows the analyst to readily incorporate an understanding of regional factors such as local energy prices, concerns over air quality, water availability, or attitudes towards construction of new energy facilities, into national assessments of energy policies. This paper reviews the analytic framework within which energy policy issues are currently addressed. The initial family of E3 models is described with the emphasis on the data linkages and feedback which are provided when these models are run sequentially. The ongoing MITRE research programme with the E3 family of models is presented and plans and opportunities for future work are outlined. 相似文献
5.
A new finite element crack growth algorithm has been developed to simulate dynamic fracture. In this algorithm, pseudo elements with very high initial density are placed below the crack plane and the density is reduced to zero in a gradual manner as the crack passes the element. A number of linear elastic and elasto-viscoplastic problems have been carried out to test the new algorithm. The results are compared with some of the existing crack growth models. 相似文献
6.
Research in object-oriented manufacturing simulations:an assessment of the state of the art 总被引:1,自引:0,他引:1
S. Narayanan D.A. Bodner T. Govindaraj L.F. Mcginnis C.M. Mitchell U. Sreekanth 《IIE Transactions》1998,30(9):795-810
Object-oriented programming (OOP) has been revolutionizing software development and maintenance. When applied to simulation of manufacturing systems, OOP also provides an opportunity for developing new ways of thinking and modeling. In this paper, we identify existing large-scale, persistent OOP-based research efforts focusing on manufacturing system simulation, and present an integrating framework for discussing the associated modeling abstractions, implementation strategies, common themes, and distinctive features. The goal is to identify the fundamental research and application issues, assess the current state of the art, and identify key research needs. 相似文献
7.
A nonlinear SOR-type algorithm is established to find the intersection of a finite number of closed convex sets in a Hilbert space. 相似文献
8.
Valve trays are becoming popular in the chemical process industries owing to their flexibility to handle a wide range of vapor
throughputs. Using the rigorous rate based model, the importance of the non-equilibrium approach is demonstrated for a typical
extractive distillation process in a Glitsch V-1 valve tray column. Simulation results based on an in-house developed code
indicated that the rate based model predictions for a valve tray column operation showed significant differences relative
to the equilibrium model. Even small errors in product purities translated into nonoptimal feed stage locations and inaccurate
number of stages required. The counter-intuitive effect of high reflux ratio on separation is explained. 相似文献
9.
A series of monomers were prepared by reacting (meth)acryloyl chloride with 2,4‐dihydroxybenzophenone, 2,4‐dihydroxybenzaldehyde, and 2,4‐dihydroxyacetophenone, respectively. The monomers were polymerized in dimethylformamide (DMF) at 70°C using benzoyl peroxide as an initiator. Polymer–metal complexes were obtained from DMF solutions of polymers with an aqueous solution of metal ions. The polymers and polymer–metal complexes were characterized by elemental analysis and spectral studies. The IR spectra of these complexes suggest that the metals are coordinated through the oxygen of the carbonyl group and the oxygen of the phenolic–OH group. The electronic spectra, electron paramagnetic resonance (EPR) spectra, and magnetic moments of polychelates showed an octahedral and square planar structure for Ni(II) and Cu(II) complexes, respectively. X‐ray diffraction studies revealed that polychelates are highly crystalline. The thermal and electrical properties, catalytic activity, and structure–property relationships are discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2083–2090, 2003 相似文献
10.
Phosphatidic acid (PtdOH) and lysophosphatidic acid (lysoPtdOH) have been shown to enhance T-lymphocyte function. However,
the FA preference and influence of acyl-CoA binding proteins on lysoPtdOH and PtdOH biosynthesis are not known. Therefore,
we determined glycerol-3-phosphate acyltransferase (GPAT) and lysophosphatidic acid acyltransferase (LAT) activity in rat
T-lymphocyte and liver membrane preparations in the presence of palmitoyl-CoA and oleoyl-CoA with or without BSA. We found
two different properties of GPAT and LAT in whole T-lymphocyte membrane preparations relative to liver. First, T-lymphocyte
basal GPAT and LAT activities were similar, whereas in liver membranes LAT activity was 10-fold higher than GPAT. Second,
T-lymphocyte LAT, but not GPAT, activity was inducible (fivefold) by the addition of albumin in the presence of palmitoyl-CoA
but not oleoyl-CoA. In contrast, albumin stimulated GPAT, but not LAT, activity in liver membranes in the presence of palmitoyl-CoA.
These results show, for the first time, that T-lymphocyte LAT activity can be increased by the presence of an acyl-CoA binding
protein, which may indicate a new important control mechanism for regulating intracellular lysoPtdOH and PtdOH levels in T-lymphocytes. 相似文献