Table of Content

30 August 2017, Volume 23 Issue 4

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Mixed pedestrian gait classification under 3D inertial sensor parameters characterization

CAI Chunyan1, ZHANG Jinyi1,2,3, LI Jianyu1, WANG Wei2, ZHANG Honghui2

2017, 23(4):  491-500.  doi:10.12066/j.issn.1007-2861.1659

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In pedestrian gait classification research, the traditional method based on the micro-electro-mechanical system (MEMS) inertial sensor technique focuses on distinguishing a single pedestrian gait, and ignoring transition gait between two single gaits. It leads to poor classification accuracy of mixed gaits such as walking, running, halting, and even causes loss of time. As a result, positioning error of pedestrian dead reckoning becomes large. This paper analyzes gait characteristics based on kinesiology, and collects raw data of pedestrian using a 9-axis MEMS sensor. 3D inertial sensor parameters are then selected to be applied to the subsequent classification algorithm. Because the Naive Bayes algorithm has low accuracy to distinguish reverse transition gaits, the improved algorithm based on the Naive Bayes algorithm judges continuity of two adjacent windows to realize mixed gait classification. Experimental results show that the proposed mixed pedestrian gait classification method with 3D inertial sensor parameters characterization can distinguish a variety of single gaits and transition gaits from mixed gaits. It can also improve the overall classification accuracy by 14.46% as compared with the method of combining sample entropy and wavelet energy. Therefore, the proposed method has a good theoretical and practical value in gait classification.

Modeling atmospheric refractive index structure constant of microwave in horizontal airflow

CANG Lei1,2, ZHAO Hengkai1,2, ZHENG Guoxin1,2

2017, 23(4):  501-509.  doi:10.12066/j.issn.1007-2861.1715

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Electromagnetic waves propagating in the atmosphere are influenced by atmospheric turbulence. The structure constant of atmospheric refractive index are generally used to describe turbulence intensity. This paper studies effects of the water vapor pressure in air on atmospheric refractive index in the 2.4 GHz microwave band. A turbulence kinetic energy (TKE) closure scheme is chosen and the structure constant of temperate and humidity is calculated with a turbulent dissipation rate. Then the normalization formulas for dry air are revised at the microwave frequency of 2.4 GHz, and a model of the structure constant of atmospheric refractive index is built in the microwave band in a horizontal airflow. In addition, the model is applied to calculate the atmospheric refractive index structure constant of microwave based on the meteorological parameter actually measured in a tunnel environment. The result indicates that humidity has a more obvious effect on refractive index structure constant in the 2.4 GHz microwave band than temperature.

Hard-decision decoding algorithm with low complexity based on check-sum updating for LDPC codes

WU Yimeng, SHI Zhidong, DENG Bin

2017, 23(4):  510-516.  doi:10.12066/j.issn.1007-2861.1674

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To reduce computational complexity of hard-decision decoding algorithms of low-density parity-check (LDPC) codes and improve decoding performance, a check-sums algorithm is proposed. It requires less computation, and is applicable to all existing harddecision algorithms. The algorithm is applied to a multi-threshold bit flipping (MTBF) algorithm whose computation complexity is similar to the bit flipping (BF) algorithm, and further improvement is made. The results show that the proposed algorithm can achieve a 0.15 dB performance gain after 5 iterations with lower computational complexity and better decoding performance.

90° THz polarization rotator based on chiral metamaterials

XU Kaikai, XIAO Zhongyin, LIU Dejun, TANG Jingyao, MA Xiaolong, WANG Zihua

2017, 23(4):  517-523.  doi:10.12066/j.issn.1007-2861.1679

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This paper proposes a novel chiral structure consisting of double L resonators fabricated on both sides of the dielectric substrate. Simulation results reveal that the structure can achieve broadband and multi-band 90° polarization rotation of x-polarization wave in a THz band. In particular, the chiral structure can realize 90° polarization rotation for x-polarized and y-polarized waves at 2.56 THz. Meanwhile, ellipticity of the linear polarization wave is about 0°. The physical mechanism of linearly polarized wave conversion based on electric fields is analyzed. The structure can also be used to design 90° polarization polarizer in other bands, for instance, microwave and near infrared regions.

Using available information as privileged information in SVM+

DONG Yong, SUN Guangling, LIU Zhi

2017, 23(4):  524-534.  doi:10.12066/j.issn.1007-2861.1675

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In machine learning, some information is only available during learning phase. Learning using privileged information (LUPI) can provide an effective solution to the problem. Such information is called privileged information. To deal with the issue that only partial privileged information of training data is available, this paper presents an intuitive but effective strategy called extended support vector machine+ (eSVM+). Specifically, for data without privileged information, available information is used as privileged information simultaneously and further cooperate it into the SVM+ formulation. In addition, for a regular supervised learning paradigm, a similar idea is adopted that all training data are both available and privileged. Naturally, it is extended SVM (eSVM), and also a special aspect of SVM+. Experimental results show that the proposed strategy can boost generalization performance of the classifier on two benchmark expression databases, BU-3DFE and Bosphorus.

A compact multiband mobile phone antenna for 4G communication

SONG Pan, XIE Yanan, PAN Dengke, LIU Zhikun, GENG Li

2017, 23(4):  535-542.  doi:10.12066/j.issn.1007-2861.1676

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A novel compact multiband mobile phone antenna for 4G communication is proposed. Using meandered monopoles and multiple branches, the antenna can resonate in multiple bands. The antenna is compact in size 32 mm×15 mm×0.8 mm. It consists of two meandered monopoles both having a length of about 1/4 wavelength. The C-shaped strip resonates at 2 GHz and the F-shaped strip at 900 MHz. The antenna is directly fed by a 50 Ω matching transmission line. The two strips co-radiate by combining and coupling to each other to achieve bandwidth of 810 971 MHz and 14 952 786 MHz, covering GSM 850/900/DCS/PCS/UMTS/ LTE 2300/2500 and meeting the requirements of mobile phone antenna for 4G communication. A prototype is fabricated and tested, showing general agreement between simulation and measurement results.

Angle sensor with two cascading abrupt-taper based on interferometer and single mode optical fiber

ZHOU Yumeng, ZHAO Chunliu, SHI Feifei, LI Yi, DONG Xinyong

2017, 23(4):  543-548.  doi:10.12066/j.issn.1007-2861.1714

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This paper proposes a simple-fabricated and high sensitive angle sensor based on single mode optical fiber. The sensor consists of two cascading abrupt-tapers with different sizes, fabricated with CO₂ laser. The cladding modes are excited in the first taper and interfered with the core mode in the second taper. When an angle applied on the sensor, length between the two tapers changes. At the same time, the first taper is bent, affecting the ratios and effective indices of the core mode, and the cladding modes excited by the first taper. As a consequence, the interference pattern has a shift. By monitoring the shift, angle measurement is achieved. Experimental results show that the sensor has a good linear relation in a certain measurement range. Sensitivity of the angle measurement is as high as 601.8 nm/(°) between 0.057 5° and 0.075 0°.

Synthesis and performance characterization of Ag nanoplates transformed from Ag nanobars

JIN Jing, LI Jiacheng, ZHAO Yining, YAN Jiamei, LIU Can, SHI Weimin

2017, 23(4):  549-554.  doi:10.12066/j.issn.1007-2861.1719

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Ag triangular nanoplates were obtained by introducing sodium citrate, H₂O₂ and NaBH₄ in the Ag nanobars precursor solution. X-ray diffraction (XRD), transmission electron microscope (TEM) and ultraviolet visible-near infrared (UV-Vis-NIR) spectra were used to characterize the samples. The results indicate that Ag triangular nanoplates have a face centered cubic (fcc) structure, and their edge length is about 100 nm. Morphologies of Ag nanoplates dependes on the different amounts of Ag nanobars precursor solution. From UV-Vis-NIR spectra, Ag triangular nanoplates have a strong surface plasmon resonance (SPR) peak at about 830 nm. Because of the excellent infrared absorption property, Ag triangular nanoplates can be used for top electrode of silicon film solar cell in the future.

Arnoldi-PIO algorithm for PageRank

GU Chuanqing1, NIE Ying1, WANG Jinbo2

2017, 23(4):  555-562.  doi:10.12066/j.issn.1007-2861.1867

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The PageRank algorithm plays an important role in determining the importance of Web pages. The power-inner-outer (PIO) method is a two-step splitting iteration framework that combines the inner-outer scheme with the classical power method to accelerate the computation of PageRank algorithm. This paper proposes an Arnoldi-PIO algorithm, which is a PIO iteration algorithm modified with the thick restarted Arnoldi method. Description and convergence of the proposed algorithm are discussed in details. Numerical results show efficiency and convergence behaviors of the algorithm.

Bacterial biofilm growth dynamical modeling and numerical simulation based on multiple-phase field theory

ZHANG Shumei1, XU Xiangrong1, XU Hao2, ZHOU Tao1, LI Shuang1, LI Yan1

2017, 23(4):  563-574.  doi:10.12066/j.issn.1007-2861.1690

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Bacteria biofilms are widespread in nature and industrial environments. A bacteria biofilm is regarded as an incompressible viscous fluid composed of multiplecomponents. The theory of multiple-phase field, material continuity equation, momentum conservation equation, field control equations and biological reaction dynamic equation are combined to model bacterial biofilm growth dynamics. A numerical solution of the multiplecomponent bacterial biofilm growth dynamical model is used to describe the growth of bacteria, the law of nutriment’s consumption, and extracellular polymers in static and dynamic environments.

Intelligent welding control system based on real-time process management

ZENG Jundong1, FENG Wenchao1, XU Sheng2, FU Jingqi1

2017, 23(4):  575-582.  doi:10.12066/j.issn.1007-2861.1931

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For information isolated island and loose management caused by artificial control in the welding process in ship building and boilers production, a digital control system is designed for welding, including data acquisition, production management and quality evaluation. The system is controlled comprehensively in real-time via internet. The design covers production of the welding process and quantitative evaluation of welding quality. The results show that the digital controlled welding system can effectively reduced efficiency caused by manual control, improving welding quality.

Hadamard-type inequalities for a class of (α ,m)-convex functions

LI Yujiao1, DU Tingsong1,2

2017, 23(4):  583-589.  doi:10.12066/j.issn.1007-2861.1716

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This paper proposes an integral identity. Based on the identity, some results of Hadamard inequalities are established for functions with the q-th power of the second derivative’s absolute value (α,m)-convex. Some specific applied examples are presented.

Triaxial test of high strength geocell reinforced soil

PENG Aixin, ZHANG Mengxi, ZHU Huachao

2017, 23(4):  590-599.  doi:10.12066/j.issn.1007-2861.1721

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Strength and deformation characteristics of geocell reinforced soil were studied in a triaxial test. Factors that affected strength and their variation pattern were investigated under different reinforcement conditions. With the same amount of reinforcement, choice of reasonable and economical reinforcement forms was analyzed. The following results are obtained. Strength and anti-deformation capacity of the soil are clearly intensified with reinforcement. Strength is far more improved by increasing the height of geocell than reducing the node spacing when the confining pressure is constant. With the same amount of reinforcement, using large cell height and low reinforced layers is more reasonable. Analysis of the reinforcement effect coefficient and strength shows that the coefficient is reduced with the increasing of confining pressure. Cohesive strength and angle of internal friction of the soil are improved by geocell reinforcement. The improvement of cohesive strength is more significant.

Simulation of non-Gaussian fluctuating wind pressure based on LPZ spectral analysis

JIANG Lei, LI Chunxiang, DENG Ying

2017, 23(4):  600-608.  doi:10.12066/j.issn.1007-2861.1852

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This paper presents an algorithm based on linear prediction and Z-transform(LPZ) spectral analysis to simulate non-Gaussian fluctuating wind pressure. The Gaussian process is converted into a non-Gaussian white noise process by Johnson translator system. The non-Gaussian white noise process is then filtered with LPZ spectral analysis to obtain fluctuating wind pressure. The univariate non-Gaussian random signals and non-Gaussian fluctuating wind pressure are simulated using the algorithm. By comparing the statistical parameters including skewness, kurtosis and power spectral density of the non-Gaussian white noise process and fluctuating wind pressure with their target values, it is confirmed that the algorithm based on LZP spectral analysis can effectively simulate non-Gaussian fluctuating wind pressure.

Analytical solution of bending of viscoelastic timber beam reinforced with fiber reinforced polymer sheet

OUYANG Yu, JIANG Yong, ZHOU Lei

2017, 23(4):  609-622.  doi:10.12066/j.issn.1007-2861.1664

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Regarding timber beam as a viscoelastic medium with a standard linear solid constitutive relation, and assuming bonding tightly between the fiber reinforced polymer (FRP) sheet and timber beam, the creep behavior of linear bending of the timber beam reinforced with FRP sheet is studied. Based on the established governing equation for bending deformation of the viscoelastic rectangular cross-section timber beam reinforced with FRP sheet, ananalytical solution of bending of the simply-supported FRP-reinforced viscoelastic timber beam subject to step uniform load is presented by using Laplace transform. The material parameters of the standard linear solid constitutive relation for Douglas-fir (DF) timber are determined with existing experimental data. The influences of volume fraction of aramid FRP (AFRP) sheet and span-depth ratio of beam on the bending behavior of the simply-supported DF timber beam reinforced with AFRP sheet is analyzed numerically. It is shown that creep deflections of the DF timber beam can be effectively decreased by AFRP sheet reinforcement. With development of creep of the DF timber beam, the neutral axis of the DF timber beam reinforced with AFRP sheet moves to the edge of the timber beam of bonding AFRP sheet. Furthermore, with increase of the span-depth ratio of DF timber beam and volume fraction of AFRP sheet, maximum compressive and tensional stresses of the AFRP-reinforced DF timber beam decrease.

Stability of lipase in the process of catalytic interesterification reaction

LI Cheng1, WANG Shengjie2, JI Min3, OOI Chengkeat3, WONG Sookhan3, WENG Xinchu2

2017, 23(4):  623-627.  doi:10.12066/j.issn.1007-2861.1692

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Lipase is a kind of enzyme that can catalyze interesterification in a non-aqueous system. Stability of lipase is important in practical applications because of its effection of the production cost and efficiency. To understand the influence of different factors on catalytic stability of lipase, the effects of temperature, time, solvents and acyl donor on stability of lipase interesterification are studied. The results show that the effects of temperature and solvent polarity on catalytic stability of lipase are significant. But the effects of time and acyl donor are not obvious.

Analysis of different parts of Morinda using XRD and thermoanalysis-mass spectrometry techniques

YANG Dezhong, JIN Guiying, LIN Shengwen

2017, 23(4):  628-635.  doi:10.12066/j.issn.1007-2861.1693

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This paper studies the different parts of Morinda with X-ray diffraction (XRD) and thermoanalysis-mass spectrometry techniques. The results show that different parts of Morinda have different XRD characteristics and thermoanalytic characteristics. The two methods can be used for identification of different parts of Chinese herbal medicine.

Sorting TOPSIS of interval data for micro-CHP in buildings

RUAN Hongquan1,2, GAO Xin1, TAN Lijun3

2017, 23(4):  636-646.  doi:10.12066/j.issn.1007-2861.1712

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Micro-combined heat and power (micro-CHP) helps to improve energy efficiency and protect environment, thus becoming a trend in the building energy supply. In the planning stage of a micro-CHP project, evaluation of the design scheme is a key to success. To apply interval data criteria of the scheme to technique for order preference by similarity to an ideal solution (TOPSIS), the distance range and relative closeness are calculated using the interval ideal solution. An acceptability function is defined to in sort schemes. An example of 4 alternatives suitable for small buildings is presented to show feasibility and practicability of the method.