JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

some Results on Embedding Spaces of Sobolev Type into Lorentz Spaces

Jiang Ming

1993, 2(2): 103-108.

[Abstract](375) [PDF 272KB](3)

Abstract:
Lorentz spaces L^s,lprovide a deeper insight into integrable functions than L^sspaces do. Various results of the embedding of the following anisotropic spaces B_p,._p^and Ⅳ_pin- to L^s,ltogether with a counterexample are obtained.

On Uniform Domains

Yang Weiqi, You Ying

1993, 2(2): 109-116.

[Abstract](165)

Abstract:
A characteristic parameter α_Dof a domain D in Rⁿis introduced. D is unifonm if and only if α_D<∞. And α_D=1 if D is a ball or a half space. It is proved that the decomposability and the uniformity of a domain in Rⁿare still equivalent. Some problems on uniform domains and decomposition domains are discussed.

Finite Travelling Wave Solutions for a Semilinear System of Parabolic Type

Wang Shu, Li Wantong, Ye Qixiao

1993, 2(2): 117-126.

[Abstract](178)

Abstract:
Aict f Finjte rmvedrig wave （M） so1uhons fOr the fOllowhg sechear syttem （I）{u_t-u_xx+u^mv^p=0 u_t-v_xx+u^q=0 -∞ 0,p,q>0,m≥0 are studied. SolutiOns to （I） of the fOrm u （x, t）=lt（ct--x）, v（x, t）=v （cl--X） are called W soIutiOns if there exjstS a fwite ', such that u（{）=v（j）=0 for t<{,':=ct--x. It is proVed that if Pq+nl l. The asmpptohc weve profileS near the front as well as far from it are also determined. If I)q ^m= l. the exjstence of travebe wave soluhons to （I） is proved. The plnof in Esqniruis's paper（1990） for the one m=0 co be sdriplified by using the methOd develOped in thjs paper.

Shape Optimization With Sensitivity Analysis in Local Domain

Zuo Zhengxing, Cai Ping

1993, 2(2): 127-133.

[Abstract](172)

Abstract:
For complicated geometries, it is ineflicient to integrate over the entire domain. A new approach for optimization is presented here, based on sensitivity analysis of local do- main and deformation of full domain. Accurate results of design sensitivity analysis are ob- tained with this approach in shape optimization. This method is shown to be efficient when used in optimization programs and results in less distortion of the mesh.

Chromatic Adaptation to Complex Field

Li Wei

1993, 2(2): 134-140.

[Abstract](270)

Abstract:
Chromatic adaptation of human eyes to complex field is investigated using binocular asymmetric matching method. The results show that the leve of chromatic adapta- tion mainly depends on the average color of adapting field, whereas no obvious change oc- curs when the number of hues and their color differences vary in a complex field. The shifts of perceived color evoked by chromatic adaptation in CIE 1976 L U V color space are approximately proportional to the average color difference between the adapting field and reference field.

The Synthesis of Some Novel Pyrimidine Compounds

Zhou Song, Xu Hongyao, Ji Siming, Yu Congxuan, Liu Jingyong

1993, 2(2): 141-145.

[Abstract](151)

Abstract:
Four novel pyridimine compounds were prepared. The yield of the intermediates was improved with new method making use of Pd(Ⅱ) catalyst and cuprous acetylide which were proved to be practital in the formation of the acetylide which were proved to be practical in the formation of the acetylides. Their nonlinear optical properties were briefly studied.

Synthesis of N,N′-Bis(2-Nitro Benzodifuroxanyl)-1,3,5-Trinitro-2,6- Diaminobenzene

Wang Naixing, Chen Boren, Ou Yuxiang

1993, 2(2): 146-148.

[Abstract](284)

Abstract:
N, N’-bis (2-nitro benzodifuroxanyl)-1, 3, 5-trinitro-2, 6-diaminobenzene has been synthesized from 1, 3-dianimobenzene and trinitrotrichloro benzene. The molecular structure of this compound has been determined by elemental analysis. IR. ′HNMR, and M. S. spectroscopies.

A Study on the Preparation PMMA of Ultrafines

Gong Weihong, Zhou Xinwo

1993, 2(2): 149-152.

[Abstract](294)

Abstract:
Polymethylmethacrylate (PMMA) cltrafines have been prepared applying the meth- od of emulsion dispersion. Their sizes aie determined by size analysis apparatus SA-CP3. Factors affecting particle diameter and its distribution, which include PMMA conoentration, pH value and water amount, were discussed by a series of comparaison experiments. The influential principle was found, PMMA ultafines having a median diameter of 5.71μm were obtained, the ratio of the particles whose median diameters are under 10μm is 65.%. This method can be applied to the preparation of other oil-soluble polymer ultrafines, it has the advantages of simple, quick and easy to be controlled. It is possible to make it in- dustrialized in the future.

Establishment of the Basic Theory of Fuze Safety Systems

Fan Ningjun, Ma Baohua

1993, 2(2): 153-160.

[Abstract](186)

Abstract:
Presents a series of new concepts and design ideas about the fuze safety system, establishing thereby a proposed theory and relevant mathematical descriptions. The basic the- ory indicates that any fuze safety system is a physical system comprising finite safety ele- ments each of which can independently affect the system's states, and the arming process is a dynamic one in which the extent of safety of the system changes only gradually. The theory and method can be used to analyse the arming process and to guide the development of fuze safety systems.

Finite-Difference Time-Domain Methodin the Study of Eigenvalues of Coaxial Cavities

Wang Chi, Gao Benqing, Deng Ciping

1993, 2(2): 161-169.

[Abstract](200)

Abstract:
Aprogram applying an algorithm of finite-difference time-domain method is established that can be used to calculate the resonant frequencies of cavities of arbitrary modes, coupled with the discrete Fourier transform. Several coaxial resonators including the empty coaxial cavity, re-enrant coaxial cavity and partially stepped resonator are studied with this method, especially the spurious mode resonant frequencies of coaxial cavi- ties. The numerical results thus obtained are shown to be in excellent agreement with those obtainable through rigorous theoretical solutions and experiment results.

On the Describing Functions of PWM Pneumatic High-Speed On-Off Valves

Yang Shuxing, Wang Shulan, Lin Xiangzhu, Cao Fan, Cao Fan

1993, 2(2): 170-176.

[Abstract](200)

Abstract:
High-speed on-off valves are widey used in PWM electropneumatic servo sys- tems and their characteristics are generally described by their on and off delay time. This paper focuses on establishing the relationships between their on-off switching behaviors and their frequency response characteristics. A method is proposed by which the frequency response characteristics of an analog PWM high-speed on-off valve can be calculated for inputs whose periods are certain multiples of the carrier period, based on its switching be- haviors. Thus, a simple and direct describing function for a PWM high-speed on-off valve is established.

1993 Vol. 2, No. 2