JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Effects of Inlet/Outlet Ducts on Acoustic Attenuation Characteristics of Circular Expansion Chambers

ZHANG Hong-bo, GE Yun-shan, JI Zhen-lin, ZHANG Wen-ping, SONG Yan-rong, HAN Xiu-kun, ZHANG Xue-min

2006, 15(3): 253-257.

[Abstract](195)

Abstract:
The effect of coaxial, offset and extended inlet/outlet on the acoustic attenuation characteristics of circular expansion chambers are studied by the three-dimensional finite element method. The numerical results of transmission loss are compared with experiment results to verify the necessary of using three-dimensional methods. Maps of acoustic pressure level distribution inside of chambers and inlet/outlet ducts are given at a frequency to demonstrate the difference of acoustic wave propagation behavior caused by locations of inlet/outlet ducts. For the chambers of the same length, the chamber with extended inlet/outlet duct has higher attenuation ability than coaxial and offset inlet/outlet duct over middle frequencies.

Vibration Characteristic of Anchoring System of Bolt and Elastic Wave Propagation Law

WANG Cheng, LI Yi, NING Jian-guo, LIN Hua-chang

2006, 15(3): 258-262.

[Abstract](219)

Abstract:
Based on one-dimension wave theory, the propagation law of elastic wave along the rock bolt, rock medium and their coupling system are researched, and the attenuation law and propagation mechanism of wave in the anchoring system are obtained. Meanwhile, the studies on end reflection and dynamic response under load are also carried out experimentally, the relationship between anchoring length and excited wave length is obtained when the end reflection of bolt emerges, and it is concluded that under the condition of bolt loaded, as the load increases, the reflection of the upper interface of anchoring segment weakens while the end reflection strengthens relatively, hence the energy attenuation increases. These results provide some important theory basis for measuring the effective anchoring length of bolt, judging the bonding quality of anchoring end and surrounding rock, and estimating the utmost load force of bolt.

Development of Simulation Tool Orienting Production Engineering

ZHAO Ning, NING Ru-xin, TANG Cheng-tong, LIANG Fu-jun

2006, 15(3): 263-268.

[Abstract](186)

Abstract:
A simulation tool named BITSIM orienting production engineering is developed in order to improve enterprise's productivity and making up the scarcity of computer application. The architecture of BITSIM is presented first. Hierarchical technique, control strategy based on multi-agent and simulation output analysis are depicted in detail then. In the end, an application example is taken out to prove that this system could be used to analyzing different hypothetical situation and configuring the auxiliary manufacturing system before production.

Key Techniques for the Development of Web-Based PDM System

WANG Li-juan, ZHANG Xu, NING Ru-xin

2006, 15(3): 269-272.

[Abstract](84)

Abstract:
Some key techniques for the development of web-based product data management (PDM) system are introduced. The four-tiered B/S architecture of a PDM system—BITPDM is introduced first, followed by its design and implementation, including virtual data vault, flexible coding system, document management, product structure and configuration management, workflow/process and product maturity management. BITPDM can facilitate the activities from new product introduction phase to manufacturing, and manage the product data and their dynamic changing history. Based on Microsoft.NET, XML, web service and SOAP techniques, BITPDM realizes the integration and efficient management of product information.

Investigation into the Interaction of Centrifugal Compressor Impeller and Vaneless Diffuser

YANG Ce, ZHANG Dian-zuo, MA Chao-chen, HU Liao-ping

2006, 15(3): 273-277.

[Abstract](88)

Abstract:
Centrifugal compressors with parallel-wall and contracting wall vaneless diffuser are designed by using centrifugal compressor computer-aided integrated design system. The internal flow fields of the compressor are calculated by solving three-dimensional Navier-Stokes equation. Four aspects are investigated and calculation results show that the total efficiencies and total pressure ratios of the compressor with contracting wall vaneless diffuser is higher than that of the compressor with parallel-wall. The jet and wake don't mix rapidly inside vaneless diffuser. The outlet blade lean angle doesn't affect the compressor performance. The greater the mass flow rate through impeller, the more uneven the velocity distribution at impeller outlet is.

Integrated Optimal Model of Structure and Control of the Single Arm Manipulator

ZHU Deng-lin, JIANG Tao, WEI Jun-hua, WANG An-lin, WANG Shi-gang

2006, 15(3): 278-282.

[Abstract](163)

Abstract:
The integrated optimal design of mechanical and control system is discussed in terms of the performance requirement and configuration for the single arm flexible manipulator. By combination of dynamics of flexible structure and control theory, a PD feedback control system, which minimizes the settling time, has been designed. Then, the viable region of poles of the PD closed-loop control system is decided according to overshoot and the settling time, and an integrated optimal model of structure and control of single arm manipulator is presented. Finally, the parameters of structure and control system are simultaneously optimized with respect to objective function including the moment of inertia and the control effort of system.

Simulation Study on Heat Value Control System of Natural Gas Used for Color TV Tubes Production

ZHENG Bin

2006, 15(3): 283-287.

[Abstract](150)

Abstract:
In order to know the character of the heat value control system, determine the influence of natural gas quality and flow on the heat value, and learn how to adjust the parameters of control system, the model of the whole system is established, and simulation of the system is adopted in Matlab/Simulink. The simulation result shows that the feedback system with feed-forward block controls the heat value very well, and the simulation result can effectively guide the engineering design of the heat value control system, and the efficiency of engineering is improved.

Research on the Defects Restraining Ability of Power Supply Transacting Electrocircuit

GAO Jun, CHEN Chuan-bo

2006, 15(3): 288-291.

[Abstract](80)

Abstract:
Adopting the mechanism model and the system identification method, the power supply transacting electrocircuit (integrate manostat) is analyzed, and the restraining ability and the response for power supply transacting electrocircuit to overcome various battery defects are studied. The effects of the power supply yawp on the normal functions of the radio fuze are investigated. The research indicate that the shortcomings of the integration manostat as battery defects can be regarded as steady noise, and the restraining ability of the integration manostat to battery defects isn't less than 50?dB.

Design of Optimal Diffusion Layers for SPN Block Ciphers

CUI Ling-guo, CAO Yuan-da

2006, 15(3): 292-295.

[Abstract](210)

Abstract:
The diffusion layers in substitution-permutation network(SPN) block ciphers are almost invertible linear transformations, which is optimal if the branch number reaches the maximum value. The method of constructing involutory optimal diffusion layers is proposed based on the Cauchy matrix, which can decrease the cost of implementation. The analysis to experimental results indicates that the diffusion layer ensures the security of the SPN block cipher against differential cryptanalysis(DC) and linear cryptanalysis(LC), and decreases half the cost of implementation.

Data Caching for XML Query

SU Fei, CI Lin-lin, ZHU Li-ping, ZHAO Xin-xin

2006, 15(3): 296-299.

[Abstract](191)

Abstract:
In order to apply the technique of data cache to extensible markup language (XML) database system, the XML-cache system to support data cache for XQuery is presented. According to the character of XML, the queries with nesting are normalized to facilitate the following operation. Based on the idea of incomplete tree, using the document type definition (DTD) schema tree and conditions from normalized XQuery, the results of previous queries are maintained to answer new queries, at the same time, the remainder queries are sent to XML database at the back. The results of experiment show all applications supported by XML database can use this technique to cache data for future use.

New Strategy of IPACS Design and Energy Management for Spacecrafts

ZHANG Jing-rui

2006, 15(3): 300-305.

[Abstract](180)

Abstract:
The design problem of an integrated power and attitude control system (IPACS) for spacecrafts is investigated. A Lyapunov-typed IPACS controller is designed for a spacecraft equipped with 4 flywheels (3 orthogonal +1 skew). This controller keeps in the nonlinear properties of original systems, so the control result can be more precise. A control law of the flywheels is also proposed to accomplish the attitude control and energy storage simultaneously. Aiming at the limitations existing in the power conversion characteristic and the wheel's motor, a new strategy of energy management is proposed. The strategy can not only make the charged/discharged energy reaching balance in each orbital period, but also sufficiently utilize the power provided by the solar arrays. Therefore, the size and mass of solar arrays can be decreased, and the cost of spacecraft can be economized. A simulation example illustrates the validity of the designed IPACS.

Experimental Study on Wax Protective Coating for Wet Deep Silicon Etching Processes

JIANG Jian-liang, ULRICH Hilleringmann

2006, 15(3): 306-310.

[Abstract](215)

Abstract:
In order to protect the finished structures on the front side during deep silicon wet etching processes, the wax coating for double-sided etching process on the wafer is studied to separate the aforementioned structures from the strong aqueous bases. By way of heating and vacuumization, the air bubbles are expelled from the coating to extend the protection duration. The air pressure in the sealed chamber is 0.026?7?Pa, and the temperature of the heated wafer is 300?℃. Two kinds of the wax are used, and the corresponding photos of the etched wafer and the protection times are given. In 75?℃ 10%KOH solution, the protection duration is more than 8?h.

Iterative Demodulation and Decoding Scheme with 16 QAM

LIU Lin-nan, KUANG Jing-ming, LI Ming, FEI Ze-song

2006, 15(3): 311-315.

[Abstract](183)

Abstract:
Iterative demodulation and decoding scheme is analyzed and modulation labeling is considered to be one of the crucial factors to this scheme. By analyzing the existent mapping design criterion, four aspects are found as the key techniques for choosing a label mapping. Based on this discovery, a novel mapping design criterion is proposed and two label mappings are searched according to it. Simulation results show that the performance of BICM-ID using the novel mappings is better than the former ones. The extrinsic information transfer (EXIT) chart is introduced and it is used to evaluate the proposed mapping design criteria.

Channel Coding Techniques for VHF-Mobile Radio System and Its DSP Implementation

XIAO Guo-jun, HUANG Hong-kai, LIU Jia-kang, KUANG Jing-ming

2006, 15(3): 316-319.

[Abstract](182)

Abstract:
Two variable channel-coding schemes with unequal error protection (UEP) are proposed in terms of speech transmission over VHF-mobile radio system. These channel coding are separately based on rate-compatible punctured convolution (RCPC) code scheme and rate-compatible punctured turbo (RCPT) code scheme. With optimum puncturing designation and suitable scheme of rate matching, these two UEP schemes can achieve intra-class unequal error protection, which makes the protection for source bits with different importance more accurate. Its real time implementation based on a TMS320C6416 digital signal processor is also presented. The experimental results suggest that this method have reasonable system complexity and short processing delay.

Semi-Blind Channel Estimation Algorithm for OFDM Systems

XUE Yan-ming, SU Guang-chuan

2006, 15(3): 320-322.

[Abstract](184)

Abstract:
A semi-blind channel estimation algorithm based on subspace approach for orthogonal frequency division multiplexing(OFDM) systems over the frequency-selective channel is proposed. A linear precoding is applied on each block before the IFFT operation and a low-rank structure is created in the received signal. Then subspace properties can be exploited to identify the channel up to a scalar ambiguity. The residual scalar ambiguities eliminated by inserting pilots into data stream. Simulation results illustrate the performance of the proposed semi-blind algorithm.

Design and Implementation of a High-Speed Multi-Channel Data Acquisition System

HUANG Mo, LONG Teng

2006, 15(3): 323-326.

[Abstract](204)

Abstract:
A data acquisition system (DAS) to implement high-speed, real-time and multi-channel data acquisition and store is presented. The control of the system is implemented by the combination of complex programable logic device (CPLD) and digital signal processing (DSP), the bulk buffer of the system is implemented by the combination of CPLD, DSP, and synchronous dynamic random access memory (SDRAM), and the data transfer is implemented by the combination of DSP, first in first out (FIFO), universal serial bus (USB) and USB hub. The system could not only work independently in single-channel mode, but also implement high-speed real-time multi-channel data acquisition system (MCDAS) by the combination of multiple single-channels. The sampling rate and data storage capacity of each channel could reach up to 100 million sampling per second and 256?MB respectively.

Segmentation of Vessels by Morphological Filters and Dynamic Thresholding

YUAN Hui-jing, XIAO Jie, WANG Yong-tian, LIU Yue

2006, 15(3): 327-330.

[Abstract](99)

Abstract:
A method of segmenting vessels by morphological filters and dynamic thresholding for digital subtraction angiography (DSA) images is presented. The first step is to reduce the noise and enhance the details of image by using morphological operators. The second is to segment vessels by dynamic thresholding combined with global thresholding based on the properties of DSA images. Artificial images and actual images have been tested. Experiment results show that the proposed method is efficient and is of great potential for the segmentation of vessels in medical images.

Digital Demodulation Algorithm for Multi-Tone FM Signal in New Type Track Circuit

ZHU Lin-xiao, WU Si-liang

2006, 15(3): 331-335.

[Abstract](134)

Abstract:
The multi-tone frequency modulation (FM) signal transferred through track circuit in automatic train control (ATC) system is analyzed. A digital filter with ideal sloping shape in frequency domain is designed for frequency discrimination. With this filter, the FM signal is converted into AM-FM signal by frequency-to-amplitude conversion. The modulating signal is finally extracted from the envelope of the AM-FM signal. Simulations show that the digital demodulation method could accurately recover the modulating signal in low signal noise ratio (SNR) circumstance, and has good performance in suppressing interference of harmonics of traction current frequency. The feasibility of the proposed method is proved in a hardware system based on SHARC DSP.

Synthesis and Characterization of Vanadium Substituted Dawson-Type Heteropoly Acid (Mo, As)

ZHANG Jing, LI Juan, YU Li-qiong, WEI Xian-yin, LIU Li-ping, HUANG Ru-dan

2006, 15(3): 336-339.

[Abstract](74)

Abstract:
Five novel vanadium substituted series of Dawson-type heteropoly acid H₇[As₂Mo17VO62]·10H₂O（l）,H₈[As₂Mo16V₂O62]·7H₂O（2）, H₉[As₂Mo15V₃O62]·8H₂O（3）,H₈[As₂Mo14V₄O62H₂]·7H₂O（4）, H₉[As₂Mo13V₅O62H₂]·10H₂O（5） were prepared respectively in aqueous solution. When magnetic stirring and pH meter monitoring, all reactants mixed and controled different pH, then the mixture was refluxed for 10?h, later extracted by aether when it cooled, finally, it could be recrystaled by 0.5% sulphuic acid solution, then yielded productions that we need. Compounds （1）-（5） were characterized by elemental analysis,thermogravimetic analysis （TGA）, infrared spectroscopy （IR）, ultraviolet and visible spectroscopy（UV-Vis）, X-ray powder diffraction analysis, 51V nuclear magnetic resonance （ 51V NMR） structure analysis. The study indicates that these compounds possess Dawson structures. 51V NMR spectra reveals that V atom is polar-site substituted indeed.

Two New Coordination Polymers: [M（phen）（e,a-cis-1,4-chdc）（H₂O）]_n（M=Mn and Cu; phen=1,10-phenanthroline; chdc=cyclohexanedicarboxylate）

HU Chang-wen, WANG Chun-xiu, LI Hui, NIU Xue-li, PAN Wan-long, GONG Yun

2006, 15(3): 340-343.

[Abstract](228)

Abstract:
Two new coordination polymers, [M（phen）（e,a-cis-1,4-chdc）（H₂O）]_n（M=Mn （1）; M=Cu （2）; chdc=cyclohexanedicarboxylic acid; phen=1,10-phenanthroline）, were prepared under hydrothermal conditions and characterized by IR spectra and single crystal X-ray diffraction analysis. X-ray crystal structural analyses reveal that polymer 1 and 2 are isomorphic and belong to the monoclinic system. C20H20MnN₂O₅, P₂（1）/c, a=1.023?5（2） nm, b=0.891?34（19） nm, c=2.046?6（4） mm, β=99.820（3）°, Z=4 for 1; and C20H20CuN₂O₅, P2（1）/c, a=1.000?2（3） nm, b=0.894?9（2） nm, c= 2.027?0（5） nm, β=99.694（3）°, Z=4 for 2. In the structures of 1 and 2, the 1,4-chdc ligand only possesses e,a-cis conformation although there are both cis- and trans-conformations in the raw material.

PVDF-Based Micro Inorganic Fillers-Containing Polymer Electrolyte Membranes

BAI Ying, WU Feng, WU Chuan

2006, 15(3): 344-347.

[Abstract](74)

Abstract:
Polymer electrolyte membranes based on poly （vinylidene fluoride-co-hexafluoropropylene）（PVDF-HFP） with and without different types of micro inorganic fillers were prepared by phase-inversion process. Morphologies, porosities and electrochemical properties of the as-prepared membranes were investigated by means of scanning electronic microscopy （SEM）, PC （propylene carbonate） uptake and alternating current （AC） impedance technique. Compared with other membranes, the membrane with micro SiO₂filler shows a dense morphology so that its PC uptake is the highest, namely, 339%. The membrane filled with micro TiO₂exhibits good electrochemical performances: the ion conductivity is as high as 1.1×10 -3?S/cm at 18?℃, which can meet the demand of lithium ion batteries. Moreover, its initial charge-discharge efficiency exceeds 89%. The composite membranes with micro SiO₂, TiO₂and Al₂O₃are more suitable for the utilization in lithium ion batteries due to better cycleability, whereas the battery assembled with the blank membrane containing no inorganic fillers encounters a short circuit after the 5th cycle.

Synthesis and Characterization of a Novel Organic-Inorganic Hybrid Compound [Ni（DMF）₆]₃[PMo（12）O（40）]₂

GONG Yun, HU Chang-wen, LI Hui, LI Yang-guang, Wang Yong-hui

2006, 15(3): 348-351.

[Abstract](75)

Abstract:
The title compound [Ni（DMF）₆]₃[PMo12O40]₂（DMF=N,N′-dimethyllformamide） was synthesized and structurally characterized by elemental analysis, IR, UV and single crystal X-ray diffraction. It crystallized in the trigonal system, space group R-3, a=1.591?7（2） nm, b=1.591?7（2） nm, c=3.226?9（7） nm, α=90.00°, β=90.00 °, γ=120.00°, V=7.080（2） nm3, Z=3 and R₁=0.083?7. It consists of two Keggin polyoxometalates [PMo12O40] 3- linked together with three [Ni（DMF）₆] 2+ cations through hydrogen bonding interaction.

Dendrimer Templates for the Formation of Silver Nanoparticles

LI Guo-ping, LUO Yun-jun, XU Hou-cai, TAN Hui-min

2006, 15(3): 352-356.

[Abstract](80)

Abstract:
In order to control the size and shape of Ag nanoparticles obtained by using poly(amidoamine) (PAMAM) dendrimer as template, the complexation between Ag+ ions and dendrimer studied extensively by UV-Vis spectroscopy and FTIR. After the Ag+/PAMAM demdrimer being reduced by direct chemical reduction, Ag (0) nanoparticles was formed, whose structure and characterization were studied by UV-Vis spectroscopy, transmission electron microscopy (TEM) and electron diffraction (ED) respectively. The results reveal that Ag nanoparticles is a kind of face center cubic crystal and its average size is 4.5?nm. The solubility and stability of the solution containing Ag nanoparticles also indicate that dendrimer is a good kind of template, as well as a protective agent.

Measurement of Solubilities of o-Phenylphenol in Petroleum Ether and DDP in Acetone+Water Solution

WANG Li-sheng, LONG Bing-wen, XIONG You-qing, WU Jun-sheng, KANG Hui-bao

2006, 15(3): 357-359.

[Abstract](179)

Abstract:
[(6-oxide-6H-dibenze(c,e)(1,2)oxaphosphorin-6-yl)methyl]-butanedioic acid (DDP) was prepared and characterized. Solubilities of o-phenylphenol(OPP) in petroleum ether and DDP in acetone+water solution were measured by a gravimetrical method. The solubility data of OPP were well correlated using Francis equation. For the solubility of DDP in acetone aqueous solution, it was found that at each fixed temperature there existed a maximum when the acetone mass fraction in the solvent reached a certain concentration. The experiment shows that the fraction is approximately 0.6. The solubility data would be helpful for their industrial crystallization process.

Simulation of Polymer Melt Flow Fields in Intermeshing Co-Rotating Three-Screw Extruders

HU Dong-dong, CHEN Jin-nan

2006, 15(3): 360-365.

[Abstract](165)

Abstract:
Three-dimension isothermal flows of polymer melt in the kneading blocks of triangularly-arranged and parallelly-arranged intermeshing co-rotating three-screw extruders are simulated using the finite element package POLYFLOW. Based on the velocity fields calculated, the particle trajectories in both machines are visualized using particle tracking technique. The numerical results indicate that the flow patterns in three-screw extruders are similar to those in twin-screw extruders. The triangularly-arranged three-screw extruder has the largest pumping capacity and also the highest extrusion stability in terms of flowrate fluctuation with screw rotation. The instantaneous mixing and cumulative residence time distribution (RTD) characteristics are also analyzed and compared with traditional intermeshing co-rotating twin-screw extruders. It is shown that the start section of the cumulative RTD curve for the triangularly-arranged machine has a small shoulder, which is attributed to the faster flow in the central region of this type of extruder.

Adsorption of Anthraquinone Dyes from Aqueous Solutions by Penicillium Terrestre

XIN Bao-ping, LIU Xiao-mei

2006, 15(3): 366-370.

[Abstract](78)

Abstract:
Penicillium terrestre was used for removing four anthraquinone dyes from aqueous solution. The experiments were performed in Erlenmeyer flasks and spore suspension was used for inoculation. The results show that the mechanism of dye removal by penicillium terrestre is biosorption and the growing pellets exhibit higher adsorptive capacity than the resting or dead ones. The maximum removals of disperse blue 2BLN, reactive brilliant blue KN-R, acid anthraquinone blue and bromamine acid at the concentration of 120?mg/L by biosorption of growing pellets are 100%, 100%, 96% and 91%, respectively. The 100.0% and 91.4% KN-R removals are achieved respectively at the much higher concentration of 250 and 400?mg/L. 2.5?g/L glucose is sufficient for 100% KN-R removal by growing pellets. Salinity (NaCl) increase from 0 to 2% (W/V) moderately accelerates both mycelium growth and KN-R removal.

Mode Ⅰ Plane Crack Interacting with an Interfacial Crack Along a Circular Inhomogeneity

WANG Rui, MA Jian-jun, LIU Zheng-guang

2006, 15(3): 371-373.

[Abstract](188)

Abstract:
The elastic interaction of the modeⅠplane crack with an interfacial crack along a circular inhomogeneity is dealt with. The dislocation density and the stress intensity factors (SIFs) of the mode I plane crack are obtained numerically. A new kind of dislocation equilibrium equation about the plane crack is applied. The influence of some material parameters on the dislocation density and SIFs are analyzed.

Gelfand-Naimark Theorem of Commutative Hopf C^*-Algebras

LIU Ming, JIANG Li-ning

2006, 15(3): 374-378.

[Abstract](135)

Abstract:
Let A be a commutative C*-algebra. By the Gelfand-Naimark theorem, there exists a locally compact space G such that A is isomorphic to C₀（G）, the C*-algebra of all complex continuous functions on G vanishing at infinity. The result is generalized to the case of Hopf C*-algebra, where G is altered by a locally compact group. Using the isomorphic representation, the counit ε and the antipode S of a commutative Hopf C*-algebra are proposed.

2006 Vol. 15, No. 3