JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Pulse Signal Recovery Method Based on Sparse Representation

Jiangmei Zhang, Haibo Ji, Qingping Zhu, Hongsen He, Kunpeng Wang

2018, 27(2): 161-168. doi:10.15918/j.jbit1004-0579.201827.0201

[Abstract](712) [PDF 6186KB](586)

Abstract:
Pulse signal recovery is to extract useful amplitude and time information from the pulse signal contaminated by noise. It is a great challenge to precisely recover the pulse signal in loud background noise. The conventional approaches, which are mostly based on the distribution of the pulse energy spectrum, do not well determine the locations and shapes of the pulses. In this paper, we propose a time domain method to reconstruct pulse signals. In the proposed approach, a sparse representation model is established to deal with the issue of the pulse signal recovery under noise conditions. The corresponding problem based on the sparse optimization model is solved by a matching pursuit algorithm. Simulations and experiments validate the effectiveness of the proposed approach on pulse signal recovery.

Two-Dimensional Direction Finding via Sequential Sparse Representations

Yougen Xu, Ying Lu, Yulin Huang, Zhiwen Liu

2018, 27(2): 169-175. doi:10.15918/j.jbit1004-0579.201827.0202

[Abstract](619) [PDF 634KB](419)

Abstract:
The problem of two-dimensional direction finding is approached by using a multi-layer L-shaped array. The proposed method is based on two sequential sparse representations, fulfilling respectively the estimation of elevation angles, and azimuth angles. For the estimation of elevation angles, the weighted sub-array smoothing technique for perfect data decorrelation is used to produce a covariance vector suitable for exact sparse representation, related only to the elevation angles. The estimates of elevation angles are then obtained by sparse restoration associated with this elevation angle dependent covariance vector. The estimates of elevation angles are further incorporated with weighted sub-array smoothing to yield a second covariance vector for precise sparse representation related to both elevation angles,and azimuth angles. The estimates of azimuth angles, automatically paired with the estimates of elevation angles, are finally obtained by sparse restoration associated with this latter elevation-azimuth angle related covariance vector. Simulation results are included to illustrate the performance of the proposed method.

Log Likelihood Ratio-Based Relaying for Distributed Turbo Codes

Peiyao Yang, Hai Li, Shujuan Hou

2018, 27(2): 176-181. doi:10.15918/j.jbit1004-0579.201827.0203

[Abstract](724) [PDF 583KB](359)

Abstract:
A distributed turbo codes(DTC) scheme with log likelihood ratio (LLR)-based threshold at the relay for a two-hop relay networks is proposed. Different from traditional DTC schemes,the retransmission scheme at the relay, where imperfect decoding occurs, is considered in the proposed scheme. By employing a LLR-based threshold at the relay in the proposed scheme, the reliability of decoder-LLRs can be measured. As a result, only reliable symbols will be forwarded to the destination and a maximum ratio combiner (MRC) is used to combine signals received from both the source and the relay. In order to obtain the optimal threshold at the relay, an equivalent model of decoder-LLRs is investigated, so as to derive the expression of the bit error probability (BEP) of the proposed scheme under binary phase shift keying (BPSK) modulation.Simulation results demonstrate that the proposed scheme can effectively mitigate error propagation at the relay and also outperforms other existing methods.

Curvature Compensated CMOS Bandgap Reference with Novel Process Variation Calibration Technique

Jiancheng Zhang, Mao Ye, Yiqiang Zhao, Gongyuan Zhao

2018, 27(2): 182-188. doi:10.15918/j.jbit1004-0579.201827.0204

[Abstract](711) [PDF 1066KB](787)

Abstract:
A low temperature coefficient (TC) bandgap reference (BGR) with novel process variation calibration technique is proposed in this paper. This proposed calibration technique compensating both TC and output value of BGR achieves fine adjustment step towards the reference voltage, while keeping optimal TC by utilizing large resistance to help layout match. The high-order curvature compensation realized by poly and p-diffusion resistors is introduced into the design to guarantee the temperature characteristic. Implemented in 180.nm technology, the proposed BGR has been simulated to have a power supply rejection ratio (PSRR) of 91.dB@100.Hz. The calibration technique covers output voltage scope of 0.49 V-0.56 V with TC of 9.45×10^-6/℃-9.56×10^-6/℃ over the temperature range of -40℃-120℃. The designed BGR provides a reference voltage of 500.mV,with measured TC of 10.1×10^-6/℃.

Energy Optimization Oriented Three-Way Clustering Algorithm for Cloud Tasks

Chunmao Jiang, Yibing Li, Zhicong Li

2018, 27(2): 189-197. doi:10.15918/j.jbit1004-0579.201827.0205

[Abstract](563) [PDF 365KB](386)

Abstract:
Cloud computing has developed as an important information technology paradigm which can provide on-demand services. Meanwhile, its energy consumption problem has attracted a growing attention both from academic and industrial communities. In this paper, from the perspective of cloud tasks, the relationship between cloud tasks and cloud platform energy consumption is established and analyzed on the basis of the multidimensional attributes of cloud tasks. Furthermore, a three-way clustering algorithm of cloud tasks is proposed for saving energy. In the algorithm,first,the cloud tasks are classified into three categories according to the content properties of the cloud tasks and resources respectively. Next, cloud tasks and cloud resources are clustered according to their computation characteristics (e.g. computation-intensive, data-intensive). Subsequently, greedy scheduling is performed. The simulation results show that the proposed algorithm can significantly reduce the energy cost and improve resources utilization, compared with the general greedy scheduling algorithm.

Different Frequency Synchronization Theory and Its Frequency Measurement Practice Teaching Innovation Based on Lissajous Figure Method

Xin Geng, Songlin Li, Guangming Huang, Baoqiang Du, Jianhua Chen

2018, 27(2): 198-205. doi:10.15918/j.jbit1004-0579.201827.0206

[Abstract](669) [PDF 1927KB](1250)

Abstract:
According to the requirement of multi-parameter time and frequency measurement without frequency normalization, a different frequency synchronization theory is proposed based on Lissajous figure method and the variation law of Lissajous figure which are used in practice teaching of frequency measurement. The theory can achieve high-precision transmission and comparison of time and frequency and precise locking and tracking of phase and frequency, improve the level of scientific research on time and frequency for postgraduate, and promote practice teaching innovation of time frequency measurement for undergraduate. Utilizing the ratio of horizontal and vertical inflection point of the Lissajous figure, the nominal frequency of the measured signal is precisely calculated. The frequency deviation between the measured frequency and its nominal frequency can be obtained by combining the turning cycle of the Lissajous figure. By observing the phase relationship between the frequency standard signal and the measured signal, the accurate measurement of the frequency is implemented. Experimental results show that the direct measurement and comparison better than the 10^-11order of magnitude with common frequency source can be finished between any signal frequencies. The frequency measurement method based on the theory has the advantage of simple operation, quick measurement speed, small error, low noise and high measurement precision. It plays an important role in time synchronization, communications, metrology, scientific research, educational technology practice and equipment and other fields.

Network Sorting Algorithm of Multi-Frequency Signal with Adaptive SNR

Xinyong Yu, Ying Guo, Kunfeng Zhang, Lei Li, Hongguang Li

2018, 27(2): 206-212. doi:10.15918/j.jbit1004-0579.201827.0207

[Abstract](584) [PDF 2278KB](393)

Abstract:
An signal noise ratio (SNR) adaptive sorting algorithm using the time-frequency (TF) sparsity of frequency-hopping (FH) signal is proposed in this paper. Firstly, the Gabor transformation is used as TF transformation in the system and a sorting model is established under undetermined condition; then the SNR adaptive pivot threshold setting method is used to find the TF single source. The mixed matrix is estimated according to the TF matrix of single source. Lastly, signal sorting is realized through improved subspace projection combined with relative power deviation of source. Theoretical analysis and simulation results show that this algorithm has good effectiveness and performance.

Multi-Object Tracking Based on Segmentation and Collision Avoidance

Meng Zhao, Junhui Wang, Maoyong Cao, Peirui Bai, Hongyan Gu, Mingtao Pei

2018, 27(2): 213-219. doi:10.15918/j.jbit1004-0579.201827.0208

[Abstract](734) [PDF 3625KB](319)

Abstract:
An approach to track multiple objects in crowded scenes with long-term partial occlusions is proposed. Tracking-by-detection is a successful strategy to address the task of tracking multiple objects in unconstrained scenarios, but an obvious shortcoming of this method is that most information available in image sequences is simply ignored due to thresholding weak detection responses and applying non-maximum suppression. This paper proposes a multi-label conditional random field(CRF) model which integrates the superpixel information and detection responses into a unified energy optimization framework to handle the task of tracking multiple targets. A key characteristic of the model is that the pairwise potential is constructed to enforce collision avoidance between objects, which can offer the advantage to improve the tracking performance in crowded scenes. Experiments on standard benchmark databases demonstrate that the proposed algorithm significantly outperforms the state-of-the-art tracking-by-detection methods.

Anti-Windup Control Strategy of Drive System for Humanoid Robot Arm Joint

Xiaofei Zhang, Qinjun Du, Chuanming Song, Yi Cheng

2018, 27(2): 220-229. doi:10.15918/j.jbit1004-0579.201827.0209

[Abstract](516) [PDF 1584KB](520)

Abstract:
To address the problems of torque limit and controller saturation in the control of robot arm joint, an anti-windup control strategy is proposed for a humanoid robot arm, which is based on the integral state prediction under the direct torque control system of brushless DC motor. First, the arm joint of the humanoid robot is modelled. Then the speed controller model and the influence of the initial value of the integral element on the system are analyzed. On the basis of the traditional anti-windup controller, an integral state estimator is set up. Under the condition of different load torques and the given speed, the integral steady-state value is estimated. Therefore the accumulation of the speed error terminates when the integrator reaches saturation. Then the predicted integral steady-state value is used as the initial value of the regulator to enter the linear region to make the system achieve the purpose of anti-windup. The simulation results demonstrate that the control strategy for the humanoid robot arm joint based on integral state prediction can play the role of anti-windup and suppress the overshoot of the system effectively. The system has a good dynamic performance.

Efficient Activation Method of Hardware Trojan Based on Greedy Algorithm

Yingjian Yan, Xin Chuan

2018, 27(2): 230-236. doi:10.15918/j.jbit1004-0579.201827.0210

[Abstract](715) [PDF 319KB](344)

Abstract:
To generate test vector sets that can efficiently activate hardware Trojans and improve probability of the hardware Trojan activation, an efficient hardware Trojan activation method is proposed based on greedy algorithm for combinatorial hardware Trojans. Based on the greedy algorithm and the recursive construction method in the combination test, the method formulates appropriate and useful greedy strategy and generates test vector sets with different combinatorial correlation coefficients to activate hardware Trojans in target circuits. The experiment was carried out based on advanced encryption standard (AES) hardware encryption circuit,different combinatorial hardware Trojans were implanted in AES as target circuits, the experiment of detecting hardware Trojans in target circuits was performed by applying the proposed method and different combinatorial hardware Trojans in target circuits were activated successfully many times in the experiment. The experimental results show that the test vector sets generated using the proposed method could effectively activate combinatorial hardware Trojans, improve the probability of the hardware Trojan being activated, and also be applied to practice.

Super-Resolution Image Reconstruction Based on an Improved Maximum a Posteriori Algorithm

Fangbiao Li, Xin He, Zhonghui Wei, Zhiya Mu, Muyu Li

2018, 27(2): 237-240. doi:10.15918/j.jbit1004-0579.201827.0211

[Abstract](529) [PDF 909KB](323)

Abstract:
A maximum a posteriori (MAP) algorithm is proposed to improve the accuracy of super resolution (SR) reconstruction in traditional methods. The algorithm applies both joints image registration and SR reconstruction in the framework, but separates them in the process of iteratiion.Firstly, we estimate the shifting parameters through two low resolution (LR) images and use the parameters to reconstruct initial HR images. Then, we update the shifting parameters using HR images. The aforementioned steps are repeated until the ideal HR images are obtained.The metrics such as PSNR and SSIM are used to fully evaluate the quality of the reconstructed image. Experimental results indicate that the proposed method can enhance image resolution efficiently.

Estimation of Thermal Imaging System Operating Range Based on Background Radiation

Tingzhu Bai, Long Shao, Heng He, Peishan Song

2018, 27(2): 241-249. doi:10.15918/j.jbit1004-0579.201827.0212

[Abstract](638) [PDF 1477KB](392)

Abstract:
Traditional operating range prediction methods assume that the atmospheric radiances in a target path and a background path are equal. But they are different in a real-world environment. To solve this problem, the influence of atmospheric radiance on operating range prediction is analyzed in this paper. Range estimation model in thermal imaging based on background radiation (REBR) is proposed. Infrared image radiometric calibration is used to calculate the background radiation of a system entrance pupil. The result shows that,compared with traditional operating range prediction methods, the REBR method is more suitable for the actual atmospheric transmission process and the physical process of infrared imaging.

Design of Synchronous Drive Mechanism of Opposed-Piston Hydraulic-Output Engine

Hanzheng Wang, Changlu Zhao, Fujun Zhang, Zhe Zuo, Yi Lu

2018, 27(2): 250-256. doi:10.15918/j.jbit1004-0579.201827.0213

[Abstract](495) [PDF 2919KB](360)

Abstract:
In order to improve the thermal power conversion capacity of the internal combustion engine, combined with existing opposed-piston two-stroke engine(OP2S) and hydraulic free piston engine(HFPE), the integral structure for a new type of opposed-piston hydraulic-output (OPHO) engine has been designed, an operating principle has been introduced, the composition of its synchronous drive mechanism has been carefully analyzed, and a mathematical model has been built. In addition, the kinematics models of both the mechanism and the conventional crank-link mechanism have been established by utilizing MATLAB, and the movement rules of the pivotal moving components have been obtained. According to the simulation results, the piston movement of this new type of opposed-piston hydraulic-output engine reveals a prominent asymmetry compared to the conventional crank-link engine. Under a fixed engine revolving speed, the compression time of the opposed-piston hydraulic-output engine is shortened while the expanding time is lengthened, thus the gas turbulence intensity is strengthened around the top dead center (TDC) position. Meanwhile, the piston obtains a longer isometric process compared to conventional engines, which could be benefitial to enhance the combustion efficiency.

Slope Terrain Locomotion Control of a Quadruped Robot Based on Biological Reflex CPG Model

Zhuo Ge, Qingsheng Luo, Baoling Han, Qi Na

2018, 27(2): 257-266. doi:10.15918/j.jbit1004-0579.201827.0214

[Abstract](1036) [PDF 2966KB](383)

Abstract:
Inspired by the neuronal principles underlying the tetrapod locomotion, this paper proposed a biomimetic vestibular reflex central pattern generator(CPG) model to improve motion performance and terrain adaptive ability of a quadruped robot in complex situations,which is on the basis of central pattern generator (CPG)model constructed by modified Hopf oscillators. The presented reflex model was modified in the light of the particular joint configuration of the quadruped robot and the trot gait pattern. Focusing on slop locomotion of the quadruped robot with trot gaits,the co-simulations of the ADAMS virtual prototype,CPG mathematical expressions with vestibular reflex and Simulink control model were conducted. The simulation results demonstrated that the presented CPG controller with vestibular reflex was more efficient and stable for the quadruped robot trotting on slopes,compared with the different trotting control models.

Combined Size and Shape Optimization of Structures with DOE, RSM and GA

Jie Song, Hongliang Hua, Zhenqiang Liao, Tao Wang, Ming Qiu

2018, 27(2): 267-275. doi:10.15918/j.jbit1004-0579.201827.0215

[Abstract](520) [PDF 2819KB](397)

Abstract:
In this paper, size and shape optimization problem of a machine gun system is addressed with an efficient hybrid method, in which a novel and flexible mesh morphing technique is employed to achieve fast parameterization and modification of complexity structure without going back to CAD for reconstruction of geometric models or to finite element analysis (FEA) for remodeling. Design of experiments (DOE) and response surface method (RSM) are applied to approximate the constitutive parameters of a machine gun system based on experimental tests. Further FEA, secondary development technique and genetic algorithm (GA) are introduced to find all the optimal solutions in one go and the optimal design of the demonstrated machine gun system is obtained. Results of the rigid-flexible coupling dynamic analysis and exterior ballistics calculation validate the proposed methodology, which is relatively time-saving, reliable and has the potential to solve similar problems.

Simulation-Based Construction of Three-Dimensional Process Model for Punching Cartridge Cases

Zhifang Wei, Yechang Hu, Wu Lyu, Jianzhong Gao

2018, 27(2): 276-284. doi:10.15918/j.jbit1004-0579.201827.0216

[Abstract](439) [PDF 4518KB](392)

Abstract:
A method of constructing three-dimensional process model for the punching cartridge cases is presented based on DEFORM simulation analysis. Using DEFORM software, the finite element simulation models for the punching and forming process of cartridge cases are established, and the corresponding simulation result model of each intermediate procedure is obtained by continuously performing the forming process simulation. The simulation model cannot annotate size and process information due to poor interface between DEFORM software and CAD software. Thus, a 3D annotation module is developed with secondary development technology of UG NX software. Consequently, the final process model with dimension and process information is obtained. Then, with the current 3D process management system, the 3D punching and forming process design of cartridge cases can be completed further. An example is also provided to illustrate that the relative error between the simulation process model and the physical model is less than 2%, which proves the validity and reliability of the proposed method in this study.

Optimization of Crosswalk Width Based on Bi-Directional Pedestrian Crossing Time at Signalized Intersections

Ningbo Cao, Yongheng Chen, Zhaowei Qu, Liying Zhao, Yanfei Li, Qiujie Yang

2018, 27(2): 285-292. doi:10.15918/j.jbit1004-0579.201827.0217

[Abstract](510) [PDF 511KB](389)

Abstract:
The effects of the interactions between bi-directional pedestrians on the crossing time and the crosswalk width are studied. Firstly, the crossing process of bi-directional pedestrians is analyzed. The total crosswalk time is divided into a discharge time and a crossing time. The interactions between bi-directional pedestrians are quantified with the drag force theory. Then, a model is developed to study the crossing time based on the kinetic energy theory and momentum theory. Subsequently, the related parameters of the proposed model are calibrated with observed information. The relationships among crosswalk width, signal time, pedestrian volume and level of service are simulated with the proposed model. The results are verified and compared with other models. The proposed model has an absolute value of relative error of 9.38%, which is smaller than that of the Alhajyaseen model (15.26%) and Highway Capacity Manual (HCM) model (12.42%). Finally, suggested crosswalk widths at different conditions are successfully estimated with the proposed crossing time model.

Combustion Properties of Metal Particles as Components of Modified Double-Base Propellants

Xiaofei Qi, Hongyan Li, Ning Yan, Ying Wang, Xueli Chen

2018, 27(2): 293-301. doi:10.15918/j.jbit1004-0579.201827.0218

[Abstract](564) [PDF 6841KB](1861)

Abstract:
Metal particles such as aluminum (Al), magnesium (Mg), boron (B) and nickel (Ni), as well as Mg/Al alloy (Mg/Al3/4) are currently the most widely used ingredients in modified double-base propellants. In this contribution, the combustion properties of the metal species are studied by means of the high-speed photography technique and the non-contact wavelet-based measurement of flame temperature distribution. The combustion process of the Al, Mg and Mg/Al samples shows both gas phase reaction and surface oxidation, which yield volatile and nonvolatile products, corresponding to the oxide and suboxide respectively. However, the combustion of B and Ni shows only gas phase reaction, due to their high melting point as well as high enthalpy of vaporization. In addition to the experiments, a hypothetical combustion model has been proposed to clarify the combustion characteristics of metal species in modified double-base propellants.

Dynamic Mechanical Characteristics and Damage Evolution Model of Granite

Shuaifeng Wu, Yingqi Wei, Hong Cai, Bei Jia, Dianshu Liu

2018, 27(2): 302-311. doi:10.15918/j.jbit1004-0579.201827.0219

[Abstract](512) [PDF 2880KB](320)

Abstract:
By using the technique of the split Hopkinson pressure bar (SHPB), impact tests at different stress wavelengths(0.8-2.0 m) and strain rates (20-120 s^-1) were conducted to study the dynamic mechanical properties and damage accumulation evolution law of granite. Test results show that the dynamic compressive strength and strain rate of granite have a significantly exponential correlation; the relationship between peak strain and strain rate is approximately linear, and the increase of wavelengths generally makes the level of peak strain uplift. The multiple-impacts test at a low strain rate indicates that at the same wavelength, the cumulative damage of granite shows an exponential increasing form with the increase of strain rate; when keeping the increase of strain rate constant and increasing the stress wavelength, the damage accumulation effect of granite is intensified and still shows an exponential increasing form; under the effect of multiple impacts, the damage development trend of granite is similar overall, but the increase rate is accelerating. Therefore the damage evolution model was established on the basis of the exponential function while the physical meaning of parameters in the model was determined. The model can reflect the effect of the wave parameters and multiple impacts. The validity of the model and the physical meaning of the parameters were verified by the test, which further offer a reference for correlational research and engineering application for the granite.

Ameliorating Effect and Potential Mechanism of Camellia Oil on Constipated Mice

Liangshun Cao, Tianyu Liu, Chunhui Cai, Yan Li, Chongming Wu

2018, 27(2): 312-318. doi:10.15918/j.jbit1004-0579.201827.0220

[Abstract](643) [PDF 766KB](795)

Abstract:
Constipation is a global epidemic. To evaluate the ameliorating effect of camellia oil on constipation, two slow transit costive mice models were established by water deprivation or sucralfate gavage. Administration of camellia oil (4.0 and 8.0 mL/kg/day) significantly shortened the defecation time, increased defecation mass and fecal water content, with efficacies comparable to that of hemp seed oil. Intestinal propulsion test showed that camellia oil significantly enhanced the propelling rates of the charcoal powder in the intestine. Meanwhile, camellia oil also significantly decreased the serum levels of nitric oxide (NO), nitric oxide synthase (NOS) and vasoactive intestinal peptide (VIP) and increased serum substance P in costive animals. These results suggested that camellia oil can largely relieve slow transit constipation and enhance the gastrointestinal motility through modulation of serum gastrointestinal motility key factors such as NO, NOS and VIP and substance P.

2018 Vol. 27, No. 2