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991.
A. M. Hay J. A. Snyman 《International journal for numerical methods in engineering》2004,59(1):131-152
In this paper the problem of determining a manipulator design so that its workspace corresponds to a prescribed workspace is considered. Two different strategies, resulting in two different types of optimization problem are considered. The first strategy attempts to obtain a good overall approximation to the prescribed workspace and results in an unconstrained optimization problem. The second strategy entails designing a manipulator so that its workspace fully encloses the prescribed workspace and results in a constrained optimization problem. Two specific formulations of the constrained problem are proposed. The first constrained problem simply aims to fit the manipulator workspace as exactly as possible to the prescribed workspace, while still ensuring that the prescribed workspace is fully enclosed. The second constrained optimization formulation is used to design a manipulator, the workspace of which fully encloses the prescribed workspace, but which is also well‐conditioned throughout the workspace with respect to some performance measure. The particular manipulator used to illustrate and evaluate these formulations is a simple 2‐dof planar parallel manipulator, and the final formulation is also applied to a 3‐dof planar parallel manipulator. Although the manipulators studied here are simple, the objective of this study is to obtain a robust numerical methodology which can be extended to more practical and complex manipulators. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
992.
993.
N. A. Ashurbekov K. O. Iminov V. S. Kobzeva O. V. Kobzev 《Technical Physics Letters》2007,33(6):517-520
The spatial structure of visible emission from plasma of a transverse nanosecond pulsed electric discharge in a gas-filled diode with a hollow (slit) cathode has been experimentally studied. A relation is established between the regime of electron energy relaxation and the plasma-beam discharge structure formation. High values of the electron emission coefficient are observed in the experiment, which cannot be explained using the notion of electron emission from a cathode bombarded by fast heavy particles. 相似文献
994.
V. N. Perevezentsev M. Yu. Shcherban’ M. Yu. Murashkin R. Z. Valiev 《Technical Physics Letters》2007,33(8):648-650
The structure and mechanical properties of nanocrystalline aluminum alloy 1570 obtained by means of severe plastic deformation have been studied. Being tested in a temperature range from 300 to 400°C, the alloy exhibits high-strain-rate superplasticity. At 400°C, the superplasticity is manifested in a very broad range of strain rates, extending from 5 × 10?3 to 1 s?1. 相似文献
995.
Broadband chaotic oscillations were monitored in a depressed potential collector of a traveling-wave oscillator (TWO). This signal appears due to the oscillations of a virtual cathode, which is formed in the spent electron beam under the action of retarding fields existing in the multistage depressed collector. 相似文献
996.
V. V. Mamutin O. V. Bondarenko A. P. Vasil’ev A. G. Gladyshev A. Yu. Egorov N. V. Kryzhanovskaya V. S. Mikhrin V. M. Ustinov 《Technical Physics Letters》2007,33(5):384-387
The optical properties of heterostructures comprising InAs/InGaAsN quantum wells in strain-compensated GaAsN/InGaAsN superlattices have been studied. It is demonstrated that, using such superlattices of various design and thickness and with additional InAs monolayer spacers, it is possible to control the wavelength of room-temperature emission from InGaAsN quantum wells within 1.3–1.6 μm without deteriorating the output radiation characteristics, which opens additional prospects for the development of lasers on GaAs substrates for telecommunication applications. 相似文献
997.
M. I. Danielyan K. S. Kulakov S. L. Kulakov V. L. Tumanov M. E. Kompan 《Technical Physics Letters》2007,33(7):597-599
A considerable (~1.4-fold) increase in the average output power of a chemical current source has been achieved by means of a periodic pulsed manipulation of the load. A scheme used for the pulse-train loading is presented and mechanisms ensuring an increase in the average output power of the current source are considered. 相似文献
998.
A. Aryshev S. Araki P. Karataev T. Naito N. Terunuma J. Urakawa 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2007,580(3):1544-1551
A fast room temperature microwave detection system based on the Schottky Barrier-diode detector was created at the KEK ATF (Accelerator Test Facility). It was tested using Coherent Synchrotron Radiation (CSR) generated by the 1.28 GeV electron beam in the damping ring. The speed performance of the detection system was checked by observing the CSR from a multi-bunch (2.8 ns bunch separation time) beam. The theoretical estimations of CSR power yield from an edge of bending magnet as well as new injection tuning method are presented. A very high sensitivity of CSR power yield to the longitudinal electron distribution in a bunch is discussed. 相似文献
999.
V. Yu. Karpov 《Materials Science》2007,43(5):746-749
We developed a new type of porous materials with anisotropic structure based on a large number of metals. It is shown that
these material, called gasars, have properties different from the properties of the other porous materials. Thus, the strength
of gasars is much higher than the strength of powder materials with the same porosity and their impact toughness is readily
regulated by the sizes of the pores. The internal structures of gasars and possible versions of the types of pores in these
materials are strongly diversified, which makes the spectrum of their possible applications very wide. We discuss some specific
directions of the potential applications of gasars. The results of measurements of the thermal conductivity of gasars and
monolithic specimens are presented. It is shown that, for a certain level of porosity, the specific thermal conductivity of
gasars is higher than for monolithic materials. We also make some basic conclusions concerning the characteristics of new
porous materials.
__________
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 5, pp. 125–127, September–October, 2007. 相似文献
1000.
Ér. V. Kal’yanov 《Technical Physics Letters》2007,33(6):451-453
A new simple model of a system with chaotic dynamics, based on the equations of bistable systems, is considered. The possibility of converting harmonic signals into chaotic oscillations, which represent intermittent irregular and switching quasi-regular motions, is demonstrated by numerical methods. The mechanism of chaotization is analyzed using the results of numerical calculations. 相似文献