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891.
New concepts for the study of incompressible plane or axisymmetric flows are analysed by the stream tube method. Flows without eddies and pure vortex flows are considered in a transformed domain where the mapped streamlines are rectilinear or circular. The transformation between the physical domain and the computational domain is an unknown of the problem. In order to solve the non-linear set of relevant equations, we present a new algorithm based on a trust region technique which is effective for non-convex optimization problems. Experimental results show that the new algorithm is more robust compared to the Newton-Raphson method. 相似文献
892.
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896.
The Commission of European Communities (CEC) has put in place an interlocking set of initiatives aimed at enhancing the skillsbase European industry will require in order to sustain a competitive posture. One of these programs, COMETT II, is aimed at continuing education for small and medium enterprises. Another program, TEMPUS, aims to increase links between western and eastern Europe, and strongly focuses on academic interchanges and updating undergraduates/postgraduate curricula. DSP-forum, a COMETT II partnership between several European industrial firms and educational establishments, which primarily concentrates on short industrial training courses at a multiplicity of sites is discussed. Eleven partners in seven countries are currently involved with DSP-forum. Four additional partners presently complete the network of cooperating groups under TEMPUS sponsorship (primarily for development and validation of courseware and labware suitable for supporting remote interactive learning of DSP topics) 相似文献
897.
T Christensen E B Jensen F Junker H Dalb?ge F Abildgaard J J Led 《Acta chemica Scandinavica (Copenhagen, Denmark : 1989)》1992,46(1):97-99
Biosynthetic human growth hormone specifically 13C-labelled in the carbonyl positions of all 26 leucine residues has been obtained by recombinant DNA techniques using 13C-labelled leucine and an E. coli strain that requires leucine. It is shown that, on the whole, the labelling is specific with no significant mislabelling as would have been the case had the 13C-labelled leucine been metabolized. 相似文献
898.
This investigation presents the preparation of CeN0.222O0.667F1.333 by a solid-state reaction from a mixture of CeN:CeF3:CeO2 = 1:2:1.5 and its structural investigation. The samples were annealed at 900°C in platinum tubes for different times. The basic structure found by powder neutron diffraction is anion-excess fluorite-related. The unit cell is an orthorhombic distortion of the cubic fluorite cell and has the space group Abm2. The lattice constants are a = 577.71(2) pm, B = 572.76(5) pm, and c = 573.32(6) pm. The structure refined by Rietveld analysis shows that [1:0:2]- defect clusters are present. In samples prepared by longer annealing times an ordering of these clusters to larger aggregates, i.e., toward the vernier phases, was observed. This was deduced from full profile analysis without refining a structural model by comparing the instrumental resolution curves of several models. 相似文献
899.
T. A. Butina 《Journal of Applied Mechanics and Technical Physics》1992,33(1):20-23
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 1, pp. 23–26, January–February, 1992. 相似文献
900.
Rabinzohn P.D. Usagawa T. Mizuta H. Yamaguchi K. 《Electron Devices, IEEE Transactions on》1991,38(2):222-231
The bipolar/FET characteristics of the 2DEG-HBT are analyzed extensively by a two-dimensional numerical simulator based on a drift-diffusion model. For bipolar operations at high collector current densities, it is confirmed that the cutoff frequency f T is determined mainly by the collector transit time of holes and by the charging time of the extrinsic base-collector capacitance C bcEXT. The charging times of the emitter and base regions and the base transit time are shown to be negligible. A high cutoff frequency F T (88 GHz) and current gain h FE (760) are obtained for an emitter size of 1×10 μm2, and undoped collector thickness of 150 nm, and a collector current density J c of 105 A/cm2. The FET operation of the same 2DEG-HBT structure shows a threshold voltage V th of 0.74 V, the transconductance G mmax of 80 mS/mm, and maximum cutoff frequency F Tmax of 15 GHz. The dependence of the device performance on material parameters is analyzed extensively from a device design point of view 相似文献