An Intelligent Framework of Oral Examination System under Network Environment and Its Application

Weifeng MA,Xiaoyong SUN 보안공학연구지원센터 2014 International Journal of Multimedia and Ubiquitous Vol.9 No.12

As a crucial step in the process of teaching and training, examination, especially oral examination, is characterized with such defects as excessive subjectivity, difficult organization, low efficiency and heavy pressure. Thus, network technology and computer technology are employed to further promote the informationization of traditional oral examination. Through analyzing the existing problems of traditional oral examination and the feasibility of oral examination under network environment, this paper puts forward a universal framework and management model for oral examination under network environment and designed an oral examination system based on digital voice technology, artificial intelligence and software engineering. The research findings have been applied to mandarin Chinese test. So far Over 10 organization users have adopted the system and more than 300,000 examinees have been tested. Viewed from the practice, expected effects have been achieved.

Stability Evaluation of Highway Cut Slope Based on Remote Monitoring of Axial Force of Anchor and Displacement

( Weifeng Sun ),( Changgen Yan ),( Wei Xu ),( Jiangbo Xu ),( Han Bao ),( Yongli Xie ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

During the construction and operation period of highway cut slope, to evaluate the stability of the slope, it is of great necessity to monitor the responses of the slope and its reinforced structures. Compared with the traditional manual monitoring methods of slope, remote monitoring has become the development trend to obtain a timely feedback of potential hazards. This paper presents a case of highway cut slope based on remote monitoring of axial force of anchor and displacement, and the stability of the slope was evaluated. Reinforcement meters and deep displacement sensors were respectively used to monitor the axial forces of anchors and relative displacements of the slope in the In-situ test, and a network cloud platform was used to remotely manage the monitoring data. The results indicate that the axial forces of anchors varies slowly with the increasing of monitoring time within a limited range under the seasonal temperature change, and the displacements tends to be stable except in the winter, indicating the slope is stable and the monitoring is effective. For a highway cut slope with a long length, to remote monitoring the slope with an economical and effective way, it is suggested to install a small number of sensors on the sensitive positions.

An Optimal ODAM-Based Broadcast Algorithm for Vehicular Ad-Hoc Networks

( Weifeng Sun ),( Feng Xia ),( Jianhua Ma ),( Tong Fu ),( Yu Sun ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.12

Broadcast routing has become an important research field for vehicular ad-hoc networks (VANETs) recently. However, the packet delivery rate is generally low in existing VANET broadcast routing protocols. Therefore, the design of an appropriate broadcast protocol based on the features of VANET has become a crucial part of the development of VANET. This paper analyzes the disadvantage of existing broadcast routing protocols in VANETs, and proposes an improved algorithm (namely ODAM-C) based on the ODAM (Optimized Dissemination of Alarm Messages) protocol. The ODAM-C algorithm improves the packet delivery rate by two mechanisms based on the forwarding features of ODAM. The first distance-based mechanism reduces the possibility of packet loss by considering the angles between source nodes, forwarding nodes and receiving nodes. The second mechanism increases the redundancy of forwarding nodes to guarantee the packet success delivery ratio. We show by analysis and simulations that the proposed algorithm can improve packet delivery rate for vehicular networks compared against two widely-used existing protocols.

ILBA: An Improved Bat Algorithm with Inertia Weight Factor and Lévy Flight

Ma weifeng,Shi Hao,Sun Xiaoyong 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.10

Aiming at such shortcomings of traditional Bat algorithm as low precision convergence, premature convergence, slow convergence, an improved BA based on inertia weight factor and Lévy flight (ILBA) has been proposed, which has made two modifications on update equations of bat flying position in BA, using inertia weight factor to keep the flight inertia of bat individual, adaptively adjust the exploitation mechanism of the algorithm in different iteration periods, make the algorithm achieve better convergence precision and altering the strategy about position update of bats from Brownian random walks into Lévy flights strategy to effectively avoid local optimism of the algorithm and guarantee its exploration mechanism while taking advantage of heavy-tailed effect of Lévy flight to speed up the convergence. By means of 4 typical test functions simulation, the results show that ILBA boasts faster convergence and superior optimal performance compared to traditional BA and LBA.

Integrated expression and general optimisation method of bucket shape line of backhoe hydraulic excavator

Haoran Sun,Zhigui Ren,Junli Wang,Weifeng Wei,Yongyong Liang,Minghao Feng 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.6

The bucket shape of a hydraulic excavator influences its excavating performance and is determined by its shape line. In this study, the inner surface line projected on the symmetrical plane of the bucket was adopted as the bucket shape line, and the value ranges of the main parameters for the shape line were investigated. By considering the centre of the arc at the bucket bottom as the origin, the Cartesian coordinate system was established, and the integrated equation of the bucket line was derived based on the geometric constraints related to the shape line. A general optimisation model of the bucket line was established using the integrated equation. The effects of four design variables on the optimisation goal were determined using the bucket of a 21 T excavator as an example, and the optimal shape line of the bucket was obtained using a genetic algorithm. The results indicated that the cutting angle decreased by 9.92 % in comparison with that before optimisation, which was beneficial in decreasing the digging resistance. Additionally, the aspect ratio decreased by 5.75 %, thereby reducing the bucket weight. Thus, the integrated expression and the optimisation of shape lines provide a general method and theoretical basis for optimising the bucket shape.

A Voltage-fed Single-stage PFC Full-bridge Converter with Asymmetric Phase-shifted Control for Battery Chargers

Qinsong Qian,Weifeng Sun,Taizhi Zhang,Shengli Lu 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

A novel voltage-fed single-stage power factor correction (PFC) full-bridge converter based on asymmetric phase-shifted control for battery chargers is proposed in this paper. The attractive feature of the proposed converter is that it can operate in a wide output voltage range without an output low-frequency ripple, which is indispensable in battery charger applications. Meanwhile, the converter can maintain a high power factor and a controllable dc bus voltage over a wide output voltage range. In this paper, the realization of PFC and the operation principle of asymmetric phase-shifted control are given. A small-signal analysis of the proposed single-stage power factor correction (PFC) full-bridge converter is performed. Experimental results obtained from a 1kW experimental prototype are given to validate the feasibility of the proposed converter. The PF is higher than 0.97 over the entire output voltage range with the proposed control strategy.

A Voltage-fed Single-stage PFC Full-bridge Converter with Asymmetric Phase-shifted Control for Battery Chargers

Qian, Qinsong,Sun, Weifeng,Zhang, Taizhi,Lu, Shengli The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

A novel voltage-fed single-stage power factor correction (PFC) full-bridge converter based on asymmetric phase-shifted control for battery chargers is proposed in this paper. The attractive feature of the proposed converter is that it can operate in a wide output voltage range without an output low-frequency ripple, which is indispensable in battery charger applications. Meanwhile, the converter can maintain a high power factor and a controllable dc bus voltage over a wide output voltage range. In this paper, the realization of PFC and the operation principle of asymmetric phase-shifted control are given. A small-signal analysis of the proposed single-stage power factor correction (PFC) full-bridge converter is performed. Experimental results obtained from a 1kW experimental prototype are given to validate the feasibility of the proposed converter. The PF is higher than 0.97 over the entire output voltage range with the proposed control strategy.

A High-efficiency Method to Suppress Transformer Core Imbalance in Digitally Controlled Phase-shifted Full-bridge Converter

Yu, Juzheng,Qian, Qinsong,Sun, Weifeng,Zhang, Taizhi,Lu, Shengli The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

A high-efficiency method is proposed to suppress magnetic core imbalance in phase-shifted full-bridge (PSFB) converters. Compared with conventional solutions, such as controlling peak current mode (PCM) or adding DC blocking capacitance, the proposed method has several advantages, such as lower power loss and smaller size, because the additional current sensor or blocking capacitor is removed. A time domain model of the secondary side is built to analyze the relationship between transformer core imbalance and cathode voltage of secondary side rectifiers. An approximate control algorithm is designed to achieve asymmetric phase control, which reduces the effects of imbalance. A 60 V/15 A prototype is built to verify the proposed method. Experimental results show that the numerical difference of primary side peak currents between two adjacent cycles is suppressed from 2 A to approximately 0 A. Meanwhile, compared with the PCM solution, the efficiency of the PSFB converter is slightly improved from 93% to 93.2%.

A Novel Compensator for Eliminating DC Magnetizing Current Bias in Hybrid Modulated Dual Active Bridge Converters

Yunpeng Yao,Shen Xu,Weifeng Sun,Shengli Lu 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

This paper proposes a compensator to eliminate the DC bias of inductor current. This method utilizes an average-current sensing technique to detect the DC bias of inductor current. A small signal model of the DC bias compensation loop is derived. It is shown that the DC bias has a one-pole relationship with the duty cycle of the left side leading lag. By considering the pole produced by the dual active bridge (DAB) converter and the pole produced by the average-current sensing module, a one-pole-one-zero digital compensation method is given. By using this method, the DC bias is eliminated, and the stability of the compensation loop is ensured. The performance of the proposed compensator is verified with a 1.2-㎾ DAB converter prototype.

A Pattern-based Query Strategy in Wireless Sensor Network

( Yanhong Ding ),( Tie Qiu ),( Weifeng Sun ),( He Jiang ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.6

Pattern-based query processing has not attracted much attention in wireless sensor network though its counterpart has been studied extensively in data stream. The methods used for data stream usually consume large memory and much energy. This conflicts with the fact that wireless sensor networks are heavily constrained by their hardware resources. In this paper, we use piece wise representation to represent sensor nodes` collected data to save sensor nodes` memory and to reduce the energy consumption for query. After getting data stream`s and patterns` approximated line segments, we record each line`s slope. We do similar matching on slope sequences. We compute the dynamic time warping distance between slope sequences. If the distance is less than user defined threshold, we say that the subsequence is similar to the pattern. We do experiments on STM32W108 processor to evaluate our strategy`s performance compared with naive method. The results show that our strategy`s matching precision is less than that of naive method, but our method`s energy consumption is much better than that of naive approach. The strategy proposed in this paper can be used in wireless sensor network to process pattern-based queries.