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931.
A vehicle guidance system has been developed using ultrasonic sensing. The ultrasonic technology is presented in this paper with reference to how it links in with the complete system. The ultrasonic unit is based on electrostatic transducer technology and comprises a separate linear array and curved divergent transmitter which gives it an effective field of view of 60° and a range of more than 5 m. The unit has been designed primarily for use on an unmanned vehicle travelling over rough, unknown terrain. 相似文献
932.
This paper discusses a nonlinear programming problem which arises when the optimum scheduling of an electric power system is being considered. A realistic, moderately large text example is described in detail; and the solution of this example by a recent method based on quadratic programming is also reported. 相似文献
934.
D.J. Walton S.S. Phull D. Colton P. Richards A. Chyla T. Javed L. Clarke J.P. Lorimer T.J. Mason 《Ultrasonics sonochemistry》1994,1(1)
This paper describes the previously unreported electrogenerated chemiluminescence (ECL) from the electro-oxidation of several aryl carboxylates at a platinum flag electrode in aqueous, methanolic and acetonitrile solutions using tetramethylammonium hydroxides as a supporting electrolyte. In most cases electrochemiluminescence was markedly enhanced by simultaneous irradiation with ultrasound during electrolysis. Increase in electrochemiluminescence intensity with electrolysis current and carboxylate concentration was observed. Addition of a radical scavenger or purging of the solution with oxygen lowers ECL emission intensity. In contrast the presence of oxygen enhances the intensity of sonoluminescence, which is a concurrent but weaker process occurring under ultrasonic irradiation alone. Ring-substituted phenylacetates almost always produced less electrochemiluminescence than the unsubstituted parent molecule, though within the substituents studied chloro-substituted phenylacetates produced more ECL intensity than either methoxy- or nitro-substituted derivatives. 相似文献
935.
Ultrasonic velocity and attenuation are measured at 1 MHz in several kinds of wood as a function of the moisture content U. The results are interpreted in terms of water absorption mechanism of woods. The velocity decreases rapidly with increasing U up to a critical value U1 at which the curve shows a sharp bend, and the decrease is very slow for U>U1. This critical point U1 is in the range 20–50% depending on the species of wood and is regarded as the fibre saturation point of the wood, the moisture content at which the wood substance is saturated with absorbed water. Ultrasonic measurements thus provide us with an accurate way to determine the fibre saturation point. The attenuation curve also shows a critical change at U = U2, which is slightly lower than U1. The attenuation shows no change from U = 0 up to U2, but begins to increase rapidly thereafter. This point U2 indicates the moisture content at which free water begins to enter the vacant space of wood cells. 相似文献
936.
Huang Wu Wenjie Fei Xiangdong Xu Pinfang Xu Lin Fei Guiming Yu Ziwei Li Xin Wang 《Chinese Journal of Lasers》1992,1(2):141-147
By making the power broadening experiments,we have observed and analyzedthe phenomena of power broadening and the central frequency shif of fluorescence for the ura-nium transition 0-169000.38cm~(-1) for the first time. 相似文献
937.
Summary Evidence is given that in Y1−Ba2−Cu3−O7 single crystals a critical state is developed on increasing (or decreasing) the applied fieldH
0, only whenH
0 is parallel to the crystalc-axis. An ?irreversibility? line in the (H, T)-plane can be drawn where the irreversibility of the second-harmonic response sets in.
In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching. 相似文献
938.
Acoustic non-linearity parameter B/A is calculated for five binary liquid mixtures using Tong and Dong equation along with
the Flory’s statistical theory. Similar to other excess thermodynamical quantities an excess non-linearity parameter (B/A)E is defined for binary liquid mixtures. The interactions in the liquid mixtures are explained on the basis of the excess non-linearity
parameter. 相似文献
939.
本文讨论一般含1-因子连通图的n次幂中边不交1-因子的个数.从而证明了L.Nebesky(1984)猜想对含1-因子图成立. 相似文献
940.
A型超声探测纵向分辨力的测量方法改进 总被引:1,自引:0,他引:1
按《医学影像物理学实验》教材给出的A型超声探测的纵向分辨力的测量方法,第二个界面的回波难以显示,因而给测量带来困难.本文将水盘内两玻片在探头轴线位置上“一前一后”放置改为“相对探头轴线左右错开”放置,测量结果的重复性好而且直观. 相似文献