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Xun Sun,김현수,양승덕,김철규,윤준용 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.6
Butterfly valves are used widely as flow controllers in many industrial applications. In order to design and select an appropriate valvefor a particular application, it is important to predict correctly its flow coefficient. The flow coefficient of a valve can be affected by anumber of factors. This study presents a numerical investigation of the effect of friction on the flow coefficient of a triple eccentric butterflyvalve with various valve opening degrees. Since the Reynolds number and cavitation can affect the flow coefficient under certainconditions, these effects are discussed and analyzed based on previously reported experimental data before studying the effects of friction. Under the test conditions recommended in IEC 60534-2-3, it is found that the effects of the Reynolds number and cavitation are quitesmall and can be ignored. The flow coefficients obtained from numerical simulations that take into account friction are found to be ingood agreement with the experimentally determined ones. The differences in the flow coefficients obtained from numerical simulationsthat consider friction and those that ignore it are discussed. There is a maximum difference of 17 % for a fully open valve. The resultsshow that increases in the roughness height significantly increase the frictional pressure drop. The effect of the roughness height on thefrictional pressure drop and total pressure drop can be fitted well using fitting functions for fixed opening degree. It is found that the effectof the roughness can cause the determined flow coefficient to be different from the actual value. Thus, the measured flow coefficientsand pressure drops for such valves can be determined with accuracy through experimental techniques and numerical simulationsthat account for the effect of roughness.
LMI Stability Criterion with Less Variables for Time-delay Systems
Xun-Lin Zhu,Tao Li,Chong Lin,Lei Guo,Guang-Hong Yang 제어·로봇·시스템학회 2009 International Journal of Control, Automation, and Vol.7 No.4
Slack variables approach is an important technique for tackling the delay-dependent stability problem for systems with time-varying delay. In this paper, a new delay-dependent stability criterion is presented without introducing any slack variable. The technique is based on a simply integral inequal-ity. The result is shown to be equivalent to some existing ones but includes the least number of vari-ables. Thus, redundant selection and computation can be avoided so that the computational burden can be largely reduced. Numerical examples are given to illustrate the effectiveness of the proposed stabil-ity conditions.
A Practical Video Fragment Identification System
Xun Jin,Jongweon Kim 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.6
In this paper, we present a practical identification approach of video fragment for digital video files. Before analyzing the video content, we must decode it based on its encoding format first. In order to effectively identify the format of a fragment, a format classification is performed before the format identification. The methods of format classification and identification are discriminative subspace clustering (DiSC) and the K-nearest neighbor (KNN).Because of losing the meta-information, we add a maximum similar header (MSH) to the front of the fragment to recover the video content. We adopt a simple key frame detection method using standard deviation and mean value. Motion vectors of macro blocks are utilized to classify the video features for effectively identifying the video. Several edges of frames are accumulated and compose a video feature. The experimental results show the evaluations of the video format classification and identification, fragment recovery, and content identification.
Xun-an Ning,Chongyang Yang,Yujie Wang,Zuoyi Yang,Jingyu Wang,Ruijing Li 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.4
A strict aerobic Acinetobacter baumanniiYNWH 226, isolated from an activated sludge reactortreating textile wastewater, was able to grow on Congo redas the sole carbon source under aerobic conditions. Thedecolorization and TOC reduction efficiency were 99.1 and93.72%, respectively. The effects of the Congo redconcentration were studied. The environmental factors (i.e.,pH, temperature and agitation speed) on the biodegradationof Congo red in aqueous phase were studied and evaluatedusing response surface methodology. The results indicatedthat when the Congo red concentration was 100 mg/L, theoptimal decolorization conditions were as follows: 37°C,pH 7.0 and 180 rpm. The single A. baumannii YNWH 226was able to form aromatic amines by reductive breakage ofthe azo bond and then oxidize them into non-toxicmetabolites.
A Unifi ed Theory for Distortion Analysis of Thin-Walled Hollow Sections
Xun Xu,Huawen Ye,De-Yi Zhang,Shizhong Qiang 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.3
A novel unifi ed theory for distortion analysis of thin-walled hollow section has been proposed based on the Hellinger– Reissner variational principle to account for distortional shear deformation eff ects. Based on the proposed theory, a fi nite segment model has been developed and the method for determining the distortion functions of the cross-section has been proposed. The rationality of approaches for determining distortional shear stress has been analysed and it is concluded that Bredt’s pure distortion does not exist in the single-cell hollow section. Comparisons and analyses have been performed between the proposed theoretical model and the existing four groups of theories in distortion analysis of thin-walled hollow section. Eff ects of distortional warping shear stress on the shear deformation has been investigated and the results indicate that the distortional shear deformation eff ect results in a decrease of the distortional warping stresses and shear stresses but an increase of the transverse bending stresses. The numerical study indicates that the distortional shear deformation eff ects can be ignored and the fi rst derivative of the distortion angle can be employed as the distortional warping function for the conventional hollow sections of bridge structures.
Audio Fragment Identification System
Xun Jin,Jongweon Kim 보안공학연구지원센터 2014 International Journal of Multimedia and Ubiquitous Vol.9 No.12
Audio identification technologies are becoming of increasing interest for copyright protection and digital forensic. In this paper, we propose an audio fragment identification system for efficient audio identifying applications in practice. To identify an audio file fragment, we have to decode it according to its format. Thus, we precede format classification of audio fragment using Support Vector Machine in advance. After identify the format, fragment recovery is implemented by adding a maximum similar frame header in front of the fragment. Then we extract a chroma feature from the decoded audio data to achieve audio identification. The experimental results show the evaluations of the format classification, fragment recovery and audio identification.
Optimized Identification Method for Digital Music Pieces in BitTorrent
Xun Jin,Jongweon Kim 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.1
In this paper, we propose a methodology for identification of MP3 audio pieces downloaded by BitTorrent client program using cross-correlation of 12 chroma features extracted from audio signal. To prevent illegal distribution of copyrighted audio files from spreading over the internet, the file pieces split by torrent file must be detected as accurately as possible. In order to improve the probability of successfully identifying the audio pieces, we use Peak In Piece Position (PIPP) method which means the maximum peak appeared in a range corresponding to piece position and length is selected to reduce the probability of misidentification. The experimental results show probabilities of successfully identification of the pieces with different piece properties, comparisons between the proposed algorithms and conventional algorithm in terms of precisions and robustness of the proposed algorithms.