JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Simulation on damage effectiveness of hexagonal prism aimable warhead with multi-point synchronous initiations

LI Yuan, WEN Yu-quan

2014, 23(1): 1-7.

[Abstract](2582) [PDF 1343KB](105)

Abstract:
In order to study the impacts of warhead geometry and initiation pattern on the lethality of aimable warhead, multi-point synchronous initiated hexagonal prism and cylindrical warheads were compared through numerical simulation, combined with theoretical formulas of fragment deceleration and target plugging. Enhancements of fragment velocity, kinetic energy and density toward the target and target destructions were analyzed. The results show that hexagonal prism warhead can produce dense fragment beams and enhance average velocity and kinetic energy with asymmetric eight-point initiation by 24.13% and 54.52% respectively, which are higher than those of the isometric or same weight cylindrical warhead. The effective fragments are still relatively concentrated in an area of 8 m×2 m for the hexagonal prism warhead when the distance between warhead and target is 40 m.

Advanced optimal guidance law with maneuvering targets

WEN Qiu-qiu, XIA Qun-li, LI Ran

2014, 23(1): 8-15.

[Abstract](1459) [PDF 404KB](51)

Abstract:
Based on optimal theory, the advanced optimal guidance law (AOGL) is derived for the interception endgame of maneuvering targets in step mode. The guidance system dynamics, target maneuvering dynamics and acceleration, gravity acceleration are considered and their effects are dynamically cancelled out in guidance law. A four states Kalman filter is designed to estimate the required states for AOGL. Simulation results show the AOGL is less sensitive to errors caused by target maneuvering and guidance system lag, and it needs less missile acceleration in most time of guidance especially at the end of intercept than other guidance laws. Especially its acceleration is zero at the end of intercept when attacking maneuvering target.

Numerical investigation of cavity flow at subsonic and transonic speeds

LEI Juan-mian, ZHENG Zhi-wei, ZHOU Qi

2014, 23(1): 16-23.

[Abstract](1193) [PDF 855KB](32)

Abstract:
Based on finite volume method, subsonic and transonic flow in 3-D cavity of different length-to-depth ratios are numerically investigated by using Navier-Stokes equations withk-ωSST two-equation turbulence model and coupled implicit algorithm. The cavity streamline patterns and the static pressure coefficient distributions on the cavity floor are shown, and the flow characteristics of the cavity and the floor pressure coefficient distributions are analyzed. Numerical results demonstrate that the flow characteristics of the cavity at subsonic and transonic speeds are different from that of supersonic ones; length-to-depth ratio is the main factor that affects the flow characteristics of the cavity at subsonic and transonic speeds and causes changes of the cavity flow type; Mach number has a neglectable effect on the cavity flow fields at subsonic and transonic speeds and the cavity floor pressure distributions.

Experimental study on chatter of micro-miniature turn-milling

LIU Bing-bing, JIN Xin, ZHANG Zhi-jing, DENG Yong-jun

2014, 23(1): 24-28.

[Abstract](962) [PDF 1027KB](35)

Abstract:
A chatter experiment of micro-miniature turn-milling was carried out in this paper. In order to reduce the effect that the natural frequencies of workpieces brought to the chatter experiments of micro-miniature turn-milling, both positive and negative cone-shape workpieces were used. The chatter frequency of micro-miniature turn-milling process was obtained by the sampling and analyzing systems. Then by applying excitation experiments to the workpiece system and tool system respectively, the natural frequencies of these two systems were obtained. By comparing chatter frequency of micro-miniature turn-milling process with the natural frequencies of workpiece system and tool system, we found that chatter frequency of micro-miniature turn-milling was close to the natural frequency of the low stiffness vibration body in the machine tool system. The funding could be useful for optimizing the structure of machine-tool and designing the machining process.

Improving the design of reinforcing frames by simulating the arch and peltate venation structures

XING Deng-hai, CHEN Wu-yi

2014, 23(1): 29-36.

[Abstract](939) [PDF 1428KB](25)

Abstract:
Based on the analyses on arch and peltate venation structures, the design of reinforcing frames was improved. First, distribution rules of the arch structure were summarized. According to the load condition and the structure of the frame, a mechanical model of arch structure was developed, and two solutions for the model were analyzed and compared with each other. Through the analysis, application rules of arch structure for improving the design were obtained. Then, distribution rules of peltate venation structure were summarized. By using the same method, application rules of peltate venation structure for improving the design were also obtained. Finally, mechanical problem of the frame was described, and rib arrangement of the frame was redesigned. A parameter optimization for the widths of ribs in bionic arrangement was also carried out to accomplish the improving design. Comparison between bionic and conventional reinforcing frames shows that the weight is reduced by as much as 15.3%.

Analysis and experiment of cross-section flattening incoreless tube bending

JIA Mei-hui, TANG Cheng-tong, LIU Jian-hua

2014, 23(1): 37-41.

[Abstract](1615) [PDF 320KB](36)

Abstract:
In order to predict the flattening rate of the cross-section accurately during the tube bending, the generation principle, the solution and the influence factor of the cross-section flattening were studied. On the basis of the plane-stress and the assumption that the plastic volume is constant, three-dimensional strain formulas were established in consider of the cross-section flattening. Considering the wall-thickness change, the approximate calculation formulas of short axis flattening rate were deduced, with the outer diameter and the inner diameter as parameters. Because different materials have different cross-section flattening rates, a material correction factor was introduced to modify the formula based on experiments. Finally, the validity of the theoretical formulas was proved according to the calculation and the experiment results, which can provide a reference for the forming quality prediction in tube bending.

High resolution angular-displacement sensor based on whispering gallery mode resonance in bent optical fibers

YU Ying-yu, WANG Su-mei, LI Ben-ye, WU Hong-bin, CAO Zhi-tao

2014, 23(1): 42-46.

[Abstract](1934) [PDF 530KB](43)

Abstract:
A simple fiber sensor to measure angular displacement with high resolution, which is based on whispering gallery mode (WGM) resonance in bent optical fibers, is proposed. The sensor is composed of a single loop formed by loosely tying a knot using single mode fiber. To measure the transmission spectra, a tunable laser and an optic power meter are connected to the two ends of fiber loop, respectively. Significant WGM resonances occur over the investigated wavelength range for all the sensors with different bend radius. The angular-displacement sensitivity is studied in the range from -0.1°to 0.1°. The detection limit of 1.49×10^-7rad can be achieved for the detecting system with the resolution of 1pm. The simple loop-structure fiber sensor has potential application prospect in the field of architecture or bridge building with low detection limit and low cost.

Input-parallel output-parallel configuration of boost half bridge DC-DC converter with control strategy

SOOMRO Amir Mahmood, KHAHRO Shahnawaz Farhan, KHASKHELI Murad Ali, LIAO Xiao-zhong, FARHAN Manzoor

2014, 23(1): 47-52.

[Abstract](1285) [PDF 344KB](31)

Abstract:
The concept of connecting two boost half bridge DC-DC converter modules in input-parallel output-parallel configuration is presented. The input-parallel-output-parallel (IPOP) converter consists of multiple boost half bridge (BHB) DC-DC converter modules which are connected in parallel at the input and output side. This kind of converter is an attractive solution for high power applications. The correlation between input current sharing (ICS) and output current sharing (OCS) of the IPOP converter basic modules is described. Two loop control strategies, consisting of input current loop and output voltage loop, have been developed to achieve equal ICS and OCS in this present work. The control strategy for the IPOP configuration of boost half bridge DC-DC converter has been verified for different load conditions (half load and full load). The IPOP system proposed here is comprising of two modules but it can be extended to three or more. The performance of the proposed system along with the control strategy is verified by simulation in MATLAB using Simpower tool. Finally the satisfactory simulation results are obtained.

Robust power-on reset circuit with brown-out detection

ZHOU Bo, ZHANG Yan-jun, LIU Zhen-yu, LIU Da-ke

2014, 23(1): 53-57.

[Abstract](2571) [PDF 332KB](50)

Abstract:
An on-chip power-on reset circuit with a brown-out detection capability is implemented in a 0.18 μm CMOS. A pF-order capacitor is charged with a proportional-to-absolute-temperature (PTAT) current from a bandgap reference with limited loop bandwidth and slow start-up feature, to generate a reset signal with high robustness and wide-range supply rise time. An embedded brown-out detector based on complementary voltage-to-current (V-to-I) conversion and current comparison can accurately respond to the brown-out event with high robustness over process and temperature when the supply is lower than 1.5 V and the brown-out duration is longer than 0.1 ms. The presented design with embedded offset voltage cancellation consumes a quiescent current of 8.5 μA from a 1.8 V supply and works over ambient temperature of -40° to 120°.

Design of systolicB^Ncircuits in Galois fields based on quaternary logic

WU Hai-xia, QU Xiao-nan, HE Yi-han, ZHENG Rui-feng, ZHONG Shun-an

2014, 23(1): 58-62.

[Abstract](817) [PDF 318KB](26)

Abstract:
TheB^Noperation is known as an efficient basic operation in Galois fieldsGF(2^k), and various algorithms and implementations using binary logic signals have already been proposed. In order to reduce the circuit complexity and long latency ofB^Noperations, a novel algorithm and its systolic architecture are proposed based on multiple-value logic (MVL). In the very large scale integration (VLSI) realization, a kind of multiple-valued current-mode (MVCM) circuit structure is presented and in which the combination of dynamic source-coupled logic (SCL) and different-pair circuits (DPCs) is employed to improve the switching speed and reduce the power dissipation. The performance is evaluated by HSPICE simulation with 0.18 μm CMOS technology. The transistor numbers and the delay are superior to corresponding binary CMOS implementation. The combination of MVCM circuits and relevant algorithms based on MVL seems to be potential solution for high performance arithmetic operationsin Galois fieldsGF(2^k).

QRS waves detection algorithm based on positive-negative adaptive threshold method

SHANG Yu, LEI Sha-sha

2014, 23(1): 63-66.

[Abstract](802) [PDF 276KB](9)

Abstract:
In order to accurately detect the occasional negative R waves in electrocardiography (ECG) signals, the positive-negative adaptive threshold method is adopted to determine the positive R waves and the negative R waves, according to difference characteristics of ECG signals. The Q and S waves can then be accurately positioned based on the basic characteristics of QRS waves. Finally, the algorithm simulation is made based on the signals from MIT-BIH database with MATLAB. The experimental results show that the algorithm can improve the detection accuracy rate to 99.91% and overcome the problem of larger computation load for wavelet transform and other methods, so the algorithm is suitable for real-time detection.

Finite-element modeling and simulations of the intra-body communication used for biomedical monitoring

ZHANG Kai, SONG Yong, HAO Qun, HU Lan-xin, WANG Jing-wen, ZHANG Xiao-yu

2014, 23(1): 67-72.

[Abstract](1775) [PDF 1338KB](28)

Abstract:
The finite-element modeling and simulations of the intra-body communication (IBC) were investigated to provide a theoretical basis for biomedical monitoring. A finite-element model for the whole human body was developed to simulate the IBC. The simulation of galvanic coupling IBC and electrostatic coupling IBC were implemented along with different signal transmission paths, and their attenuations were calculated. Our study showed that the position near the signal electrode had higher potential than other positions in the two types of IBC, while the potential generally decreased along the axis of the body parts. Both signal attenuations of the two types IBC increased with increasing signal transmission distance, and the electrostatic coupling IBC had comparatively higher receiving potential than the galvanic coupling IBC. The results indicated that the proposed modeling method could be used for the research of biomedical monitoring based on IBC technology.

Systematic-bit-selection distributed turbo code with selective-relaying

HOU Shu-juan, LI Ling-yun, QIN Xue-fang

2014, 23(1): 73-77.

[Abstract](853) [PDF 340KB](15)

Abstract:
An improved distributed turbo coding (DTC) scheme, namely, systematic-bit-selection DTC, is proposed for a two-hop relay network implementing selective-relaying (SR). In the scheme, source broadcasts a punctured turbo code in order to increase the successful decoding rate of relay. The relay forwards systematic-bit to the destination in case of successful cyclic redundancy check (CRC). From the two versions of systematic-bit coming from relay and source respectively, the destination selects the one with higher signal-to-noise ratio (SNR) for turbo decoding. Simulation results show the improved bit error rate (BER) performance of our scheme.

Velocity estimation of moving targets with stepped-frequency radar based on Doppler frequency difference

WANG Hao-fei, REN Li-xiang

2014, 23(1): 78-82.

[Abstract](885) [PDF 334KB](20)

Abstract:
By analyzing the signal model of stepped-frequency waveform, a novel method for velocity measurement is proposed. The method is based on Doppler frequency difference which is achieved by using Hough transform. As the estimated velocity is inversely proportional to the frequency step size instead of the carrier frequency of the transmitted signal as the pulse-Doppler (PD) processing, the new algorithm can achieve much wider unambiguous velocity range. Furthermore, non-coherent integration of the sub-pulses with different carrier frequencies can be implemented by Hough transform to improve the anti-noise performance. Besides, field experimental results show that the high range resolution profile (HRRP) of a bullet with high speed can be reconstructed correctly without distortion.

Accuracy comparison of short-term oil price forecasting models

LI Wei-qi, MA Lin-wei, DAI Ya-ping, LI Dong-hai

2014, 23(1): 83-88.

[Abstract](875) [PDF 368KB](17)

Abstract:
A forecasting model of the monthly crude oil price is investigated using the data between 1988 and 2009 from U.S. Energy Information Administration. First generalized auto-regressive conditional heteroskedasticity (GARCH) is applied to a state space model, a hybrid model (SS-GARCH) is proposed. Afterwards by computing a special likelihood function with two weak assumptions, model parameters are estimated by means of a faster algorithm. Based on the SS-GARCH model with the identified parameters, oil prices of next three months are forecasted by applying a Kalman filter. Through comparing the results between the SS-GARCH model and an econometric structure model, the SS-GARCH method is shown that it improves the forecasting accuracy by decreasing the index of mean absolute error (RMSE) from 7.09 to 2.99, and also decreasing the index of MAE from 3.83 to 1.69. The results indicate that the SS-GARCH model can play a useful role in forecasting short-term crude oil prices.

New shape clustering method based on contour DFT descriptor and modified SOFM neural network

LIU Wei-yang, XU Xiang-min, MEI Jian-han, WANG Wei-kai

2014, 23(1): 89-95.

[Abstract](813) [PDF 734KB](15)

Abstract:
A contour shape descriptor based on discrete Fourier transform (DFT) and a K-means algorithm modified self-organizing feature map (SOFM) neural network are established for shape clustering. The given shape is first sampled uniformly in the polar coordinate. Then the discrete series is transformed to frequency domain and constructed to a shape characteristics vector. Firstly, sample set is roughly clustered using SOFM neural network to reduce the scale of samples. K-means algorithm is then applied to improve the performance of SOFM neural network and process the accurate clustering. K-means algorithm also increases the controllability of the clustering. The K-means algorithm modified SOFM neural network is used to cluster the shape characteristics vectors which is previously constructed. With leaf shapes as an example, the simulation results show that this method is effective to cluster the contour shapes.

Novel constrained multi-objective biogeography-based optimization algorithm for robot path planning

XU Zhi-dan, MO Hong-wei

2014, 23(1): 96-101.

[Abstract](911) [PDF 338KB](14)

Abstract:
A constrained multi-objective biogeography-based optimization algorithm (CMBOA) was proposed to solve robot path planning (RPP). For RPP, the length and smoothness of path were taken as the optimization objectives, and the distance from the obstacles was constraint. In CMBOA, a new migration operator with disturbance factor was designed and applied to the feasible population to generate many more non-dominated feasible individuals; meanwhile, some infeasible individuals nearby feasible region were recombined with the nearest feasible ones to approach the feasibility. Compared with classical multi-objective evolutionary algorithms, the current study indicates that CMBOA has better performance for RPP.

Fast motion estimation algorithm of video stabilization system

WU Hao, DENG Hong-bin

2014, 23(1): 102-107.

[Abstract](1337) [PDF 1046KB](24)

Abstract:
A real-time electronic image stabilization motion estimation method based on fast sub-block gray projection algorithm is proposed. In the method, each image is divided into a number of sub-blocks, and sub-blocks are sifted with their gray gradients. After removing sub-blocks whose gray gradients are lower than the given threshold, the calculation amount of projection is reduced and the motion estimation accuracy is improved. Then gray projection is done in each remained sub-block, and global motion vector of the image is calculated according to the local motion vectors of sub-blocks and the affine motion model. The drawbacks as the local motions reducing the global motion estimation accuracy and traditional gray projection algorithm could not deal with rotation are resolved well by this algorithm. The experiment results show that the algorithm is more accurate and efficient than the gray projection algorithm.

Text retrieval algorithm that decreases confusion

JIANG Yun-chen, LUO Sen-lin, HAN Lei, PAN Li-min

2014, 23(1): 108-116.

[Abstract](765) [PDF 437KB](17)

Abstract:
To overcome the problem that the confusion between texts limits the precision in text retrieval, a new text retrieval algorithm that decrease confusion (DCTR) is proposed. The algorithm constructs the searching template to represent the user's searching intention through positive and negative training. By using the prior probabilities in the template, the supported probability and anti-supported probability of each text in the text library can be estimated for discrimination. The searching result can be ranked according to similarities between retrieved texts and the template. The complexity of DCTR is close to term frequency and mversed document frequency (TF-IDF). Its distinguishing ability to confusable texts could be advanced and the performance of the result would be improved with increasing of training times.

Multimodal spontaneous affect recognition using neural networks learned with hints

ZHANG Xin, LÜ Kun

2014, 23(1): 117-125.

[Abstract](799) [PDF 1548KB](18)

Abstract:
A multimodal fusion classifier is presented based on neural networks (NNs) learned with hints for automatic spontaneous affect recognition. In case that different channels can provide complementary information, features are utilized from four behavioral cues: frontal-view facial expression, profile-view facial expression, shoulder movement, and vocalization (audio). NNs are used in both single cue processing and multimodal fusion. Coarse categories and quadrants in the activation-evaluation dimensional space are utilized respectively as the heuristic information (hints) of NNs during training, aiming at recognition of basic emotions. With the aid of hints, the weights in NNs could learn optimal feature groupings and the subtlety and complexity of spontaneous affective states could be better modeled. The proposed method requires low computation effort and reaches high recognition accuracy, even if the training data is insufficient. Experiment results on the Semaine naturalistic dataset demonstrate that our method is effective and promising.

Surface plasmon resonance sensor based on molecularly imprinted films for the detection of pentaerythritol tetranitrate (PETN)

ZHANG Qing-wen, BAO Han, ZHAO Feng-qin, BAO Si-miao, WEI Tian-xin, ZHANG Peng, CUI He

2014, 23(1): 126-130.

[Abstract](1888) [PDF 344KB](23)

Abstract:
A novel surface plasmon resonance (SPR) sensor based on molecularly imprinted films (MIFs) was developed for the detection of pentaerythritol tetranitrate (PETN). In this work, the thin MIFs were formed on a gold sensor chip through thermal co-polymerization of functional monomers (methacrylic acid, MAA) and crosslinking monomers (ethylene glycol dimethacrylate, EGDMA) in the presence of template molecules PETN. The template molecules PETN were subsequently removed from the MIFs simply by rinsing the MIFs with a mixture of acetonitrile and acetic acid 9:1 (v/v), thus the recognition sites were formed for specific detection of PETN. According to the mass coverage equation, the surface coverage of removed PETN from MIFs was about 10.8 ng/mm². The developed SPR sensor allowed for the detection of PETN at concentration down to 10^-10mol/L. A control experiment utilizing an analogue cyclotrimethylenetrinitramine (RDX) showed MIFs' good selectivity to PETN.

Separation of non-denatured proteins using semi-crosslinked polyacrylamide capillary gel electrophoresis

XU Jian-dong, HU Ding-yu, BAKTUR Rena, GENG Li-na, DENG Yu-lin

2014, 23(1): 131-137.

[Abstract](879) [PDF 413KB](12)

Abstract:
This work presents an approach to build a high-performance, low-viscous and replaceable separation matrix, semi-crosslinked polyacrylamide (semi-CPA) capillary gel electrophoresis. Non-denatured basic proteins, such as lysozyme, cytochrome C, ribonuclease A and trypsin were separated. The impacts of monomer and cross-linker concentrations on protein separation were studied, and the ability of dynamic capillary inner wall coating was demonstrated. The UV absorption interference by semi-CPA gel matrix was successfully overcome by a partial filling technique, which results in sensitivity 20 times higher than other protein separation method. The excellent separation ability, reproducibility and dynamic coating ability made semi-CPA an ideal separation media in both capillary electrophoresis and microfluidic chip separation scheme.

Promoting effect of licorice extract on induction ofβ-glucuronidase inPenicillium purpurogenumLi-3

LIU Gui-yan, WANG Dong, DAI Da-zhang, RASOOL Aamir, LI Chun

2014, 23(1): 138-142.

[Abstract](926) [PDF 760KB](33)

Abstract:
Penicillium purpurogenumLi-3, a fungus producingβ-glucuronidase (PGUS), can convert glycyrrhizin (GL) to glycyrrhetinic acid monoglucuronide (GAMG) when grown in medium with GL as the sole carbon source. In order to improve the conversion rate of GL and the yield of GAMG, licorice extract (LE) was added as an inducer to enhance the production of GAMG by the PGUS. In this work, the influence of LE on the conversion rate of GL to GAMG was studied. When thePenicillium purpurogenumLi-3 was grown in the medium containing LE and GL (concentration ratio of LE to GL was 2:3), the conversion rate of GL was 84.12% with 38.18% increase and the yield of GAMG was 80.47% with 37.18% increase, comparing with to the medium only containing GL at 48 h. The enzyme activity ofβ-glucuronidase was also enhanced from 22.4 U/mL to 82.3 U/mL, which increased up to about 3.67 fold. The results showed that LE could significantly improve the induced expression level of PGUS.

2014 Vol. 23, No. 1