JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

A Note on Hamiltionian Decomposition of Cayley Digraphs on Dicyclic Groups

Wang Chengde

1993, 2(1): 1-4.

[Abstract](214)

Abstract:
For every dicyclic group,there is a generating set of two elements such that the corresponding Cayley digraph is Harmiltonian decomposable.

Existence of Many and Infinitely Many Periodic Solutions for Some Types of Differential Delay Equations

Ge Weigao

1993, 2(1): 5-14.

[Abstract](94)

Abstract:
J.Kaplan and J.Yorke's method is extended to establish the exis- tence of many and infinitely many periodic solutions for the DDEs (t) =±f(x(t-1))±f(x(t-2))and (t)=±f(x(t-1).

Synthesis of N,N'-bis(2,4-dinitrobenzofuroxan)-3,5-dinitro-2,6-diaminopyridine

Wang Naixing, Chen Boren, Ou Yuxiang

1993, 2(1): 15-18.

[Abstract](176)

Abstract:
N,N'-bis(2,4-dinitrobenzofuroxan)-3,5-dinitro-2,6-diaminopy- ridine has been synthesized from 2,6-diaminopyridine and trinitrodich- lorobenzene.For this compound,the structure has been determined by ele- mental analysis,IR,HNMR and MS spectroscopy.

Study on the Refractive-Index Structure Coefficient C_N²

Yan Jixiang, Zhou Renzhong, Yu Xin, Yao Jietai

1993, 2(1): 19-26.

[Abstract](204)

Abstract:
Based on the regularities of temperature fluctuation,the atmo- sphere below an altitude of 71km above ground is divided into 6 sublayers. For each of them the calculation formulae of temperature and pressure are derived.The calculated results at any altitude in the range under considera- tion agree well with the values laid down in the table of“U.S.Standard At- mosphere”.From this the formula for the refractive-index structure coeffi- cient C_N²,of much importance in the research of adaptive optics,is obtained for the corresponding altitudes.

Research on Estimation of Frequency Response Function

Zheng Muqiao, Li Li, Hu Sheping

1993, 2(1): 27-37.

[Abstract](171) [PDF 446KB](3)

Abstract:
Based on an investigation of existing methods for estimating fre- quency response functions（FRF）at home and abroad,two methods are ad- vanced.The one,denoted as H₁₂,avoids underestimates at resonances and overestimates at antiresonances,while the other,denoted as H_F,regards the noise ratio of output to input as varying with the frequency.Finally,a soft- ware for estimating frequency response functions is introduced.A modal test for a steel plate excited with a random signal is made,and frequency response function estimates are made,making use of the above software.The test re- sults conform well with the theoretical analysis.

Computer Aided Analysis of the Performances of a Tilting Pad Gas Journal Bearing

Zhou Yong, Li Zhenqing, Mao Qiande

1993, 2(1): 38-48.

[Abstract](271)

Abstract:
Tilting pad gas journal bearing is one of the most widely used types of aerodynamic bearings due to its inherent excellent stability in high speed applications.A practical method for analyzing and calculating the per- formances of such bearings is presented as well as its rotordynamics based on the computer aided technique.The method of calculation and the philosophy of programming with a microcomputer for the computer aided analysis are highlighted.

Laser Doppler Vibrometer Without Directional Ambiguity Using Rectangular Phase Grating

Deng Luogen, Liu Xunliang, Li Shaoying

1993, 2(1): 49-61.

[Abstract](192)

Abstract:
The two-phase detection method for directional discrimination in laser Doppler measurements is discussed.The diffraction efficiency of a sin- gle period rectangular phase grating is analysed and a kind of back-scattered laser Doppler vibrometer without directional ambiguity using the single peri- od rectangular phase grating as the beam-combiner described.The principles of this kind of vibrometer are explained in detail,and some experimental re- sults are given.In this kind of vibrometer,the rectangular phase grating, without the zero diffracted order and even orders,is used to eliminate use- less stray light and to combine the useful signal light.Differential electronics is employed to reject signal noise.Therefore,the signal-to-noise ratio of Doppler signals and the measurement accuracy of the instrument are im- proved and the range of application is expanded.

Mathematical Description of the Arming Process of a Fuze Safety System

Fan Ningjun, Ma Baohua, Ge Weigao

1993, 2(1): 62-73.

[Abstract](244)

Abstract:
By determining the state variables of a fuze safety system,some mathematical models——the system of ordinary differential and functional differential equations about the system's arming process are founded in a state space.Also,the arming states and restricted relations of the safety factors are described and some demonstrations are presented.

A Temperature-Autocompensated Detecting Circuit for the Capacitance Fuze

Deng Jiahao, Zhou Yong, Cheng Shouhao, Liu Hua, Shi Jusheng

1993, 2(1): 74-82.

[Abstract](164)

Abstract:
In view of drastic possible changes in fuze environment tempera- ture,a kind of temperature autocompensated detecting circuit for the capaci- tance fuze is proposed.It provides a steady detected output when the envi- ronment temperature varies from-50℃ to 65℃ and keeps a stable detecting sensitivity.Based on an analysis of the circuit,influence of the major param- eters of the oscillating circuit on the amplitude are explored.A few impor- tant controllable parameters affecting the circuit feature are found out.A parameter-control method is given in order to improve the circuit perfor- mance.

The Technology of Data Conversion Among Different DBMSs

Sun Shiyu, Song Hantao, Liang Yunrong

1993, 2(1): 83-89.

[Abstract](257)

Abstract:
In the application development of database,sharing information a- mong different DBMSs is an important and meaningful technical subject. This paper analyzes the schema definition and physical organization of popu- lar relational DBMSs and suggests the use of an intermediary schema.This technology provides many advantages such as powerful extensibility and ease in the integration of data conversions among different DBMSs etc.This pa- per introduces the data conversion system under DOS and XENIX operating systems.

Ordered Solidification Technique Under Low Pressures in the Loading of Molten Explosives

Xu Gengguang, Liu Derun, Wang Tingzeng, He Dechang

1993, 2(1): 90-97.

[Abstract](218)

Abstract:
In order to improve the quality of loading and make the ammuni- tion safe in use,a new loading technique of ordered solidification has been studied.The study shows that the adoption of this new technique makes the charge more compact and brings about a satisfactory supplement of liquid ex- plosives,thus increasing the charge density,which is most advantageous to the crimination of pores,cavities,gaps at the bottom and in loose struc- tures.The physical mechanical properties of the charge are hence greatly im- proved,and the sensitivity of the charge to environmental stimulations is much lowered.

Preparation of Superfine Fe₃O₄Cubic Powders

Liu Ying, Gao Wei, Wang Jianhua

1993, 2(1): 98-102.

[Abstract](165) [PDF 254KB](5)

Abstract:
A kind of superfine Fe₃O₄cubic powder has been prepared chemi- cally.Its formation is related with the concentration of Na⁺¹in the chemical reaction.Given the same particle size,a superfine Fe₃O₄cubic powder has a higher H（?） and lower σ,than one made up of spherical Fe_O₄.

1993 Vol. 2, No. 1