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Ruoyu Zhang,Changxi Feng,Ruoyu Zhang,Guangchao You,Rui Liu 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.1
In order to investigate mechanical properties of L-shaped column composed of concrete-filled square steel tubes (LCFT column) under eccentric compression, LCFT columns were designed and tested. Through two eccentric compression experiments, the failure mode, the curves of loading-displacement for the whole member and the curves of deflection for mono column (single limb of LCFT column) were obtained. Nonlinear finite element analysis was also employed in this investigation, in which thickness of tube flange, connecting plate thickness and diameter of the hole on connecting plate were discussed. According to results of eccentric compression test and finite element analysis, analytical method of bearing capacity of LCFT columns is proposed based on the yielding criterion of the cross-sectional edge stresses. Results of analytical method, finite element analysis and eccentric compression experiment are resistant with each other, and the accuracy of the analytical method in this paper is verified.
A Computational Study on the Supersonic Flow Characteristics in a Pintle Nozzle
Ruoyu Deng,Heuy-Dong Kim(김희동) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12
Typical solid rocket motors (SRM) have advantage of their inherent simplicity and reliability, but they do not have the capability to change thrust profile like other propulsion system. Pintle technology is one of the means to achieve variable and programmable thrust. Dynamic characteristics of a pintle nozzle were studied numerically based on dynamic characteristics of pintle nozzle. A two-dimensional axisymmetric numerical simulation has been carried for thrust performance during the pintle moving process. To validate the ability of the numerical model, numerical results were compared with the experiment results. The chamber pressure distribution shows quite good match with the experimental result. Aiming to optimum dynamic performance, different pintle speeds should be researched. The period of chamber pressure and thrust variation becomes longer when the pintle speed decreases. There is a delay between of thrust variation and pintle movement. The result will provide the reference to the further development of shock vector control.
Combining Adaptive Filtering and IF Flows to Detect DDoS Attacks within a Router
( Ruoyu Yan ),( Qinghua Zheng ),( Haifei Li ) 한국인터넷정보학회 2010 KSII Transactions on Internet and Information Syst Vol.4 No.3
Traffic matrix-based anomaly detection and DDoS attacks detection in networks are research focus in the network security and traffic measurement community. In this paper, firstly, a new type of unidirectional flow called IF flow is proposed. Merits and features of IF flows are analyzed in detail and then two efficient methods are introduced in our DDoS attacks detection and evaluation scheme. The first method uses residual variance ratio to detect DDoS attacks after Recursive Least Square (RLS) filter is applied to predict IF flows. The second method uses generalized likelihood ratio (GLR) statistical test to detect DDoS attacks after a Kalman filter is applied to estimate IF flows. Based on the two complementary methods, an evaluation formula is proposed to assess the seriousness of current DDoS attacks on router ports. Furthermore, the sensitivity of three types of traffic (IF flow, input link and output link) to DDoS attacks is analyzed and compared. Experiments show that IF flow has more power to expose anomaly than the other two types of traffic. Finally, two proposed methods are compared in terms of detection rate, processing speed, etc., and also compared in detail with Principal Component Analysis (PCA) and Cumulative Sum (CUSUM) methods. The results demonstrate that adaptive filter methods have higher detection rate, lower false alarm rate and smaller detection lag time.
A Visualization System of Brain MR image based on VTK
( Ruoyu Du ),( Hyo Jong Lee ) 한국정보처리학회 2012 한국정보처리학회 학술대회논문집 Vol.19 No.1
VTK is a free but professional development platform for images three-dimensional (3D) reconstruction and processing. It is powerful, open-source, and users can customize their own needs by self-development of great flexibility. To give the doctors more and detailed information by simulate dissection to the 3-D brain MRI image after reconstruction. A Visualization System (VS) is proposed to achieve 3D brain reconstruction and virtual dissection functions. Based on the free VTK visualization development platform and Visual Studio 2010 IDE development tools, through C++ language, using real people’s MRI brain dataset, we realized the images 3D reconstruction and also its applications and extensions correspondingly. The display effect of the reconstructed 3D image is well and intuitive. With the related operations such as measurement, virtual dissection and so on, the good results we desired could be achieved.
Simplification of LIDAR Data for Building Extraction Based on Quad-tree Structure
( Ruoyu Du ),( Hyo Jong Lee ) 한국정보처리학회 2011 한국정보처리학회 학술대회논문집 Vol.18 No.2
LiDAR data is very large, which contains an amount of redundant information. The information not only takes up a lot of storage space but also brings much inconvenience to the LIDAR data transmission and application. Therefore, a simplified method was proposed for LiDAR data based on quad-tree structure in this paper. The boundary contour lines of the buildings are displayed as building extraction. Experimental results show that the method is efficient for point’s simplification according to the rule of mapping.
Numerical Visualization of the Pseudo-Shock Waves using LES
Ruoyu Deng,Heuy Dong Kim 한국가시화정보학회 2015 한국가시화정보학회 학술발표대회 논문집 Vol.2015 No.12
Pseudo-shock waves in the divergent part of a Laval nozzle with rectangular cross section have been investigated through numerical methods using large-eddy simulation (LES). LES studies have been done for the complex flow phenomena of three-dimensional pseudo-shock waves. The LES results have been validated against experimental wall-pressure measurements. It shows good agreement with experimental results. Pseudo-shock length and corner separation have been studied in three-dimensional LES model. Comparison of centerline pressure measurement and 3D visualization measurement has been discussed for the corner separation position. It has been concluded that the pseudo-shock length should be measured by using 3D visualization measurement.
A CFD study on the Counterflow Thrust Vector Control
Ruoyu Deng,Heuy Dong Kim 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5
Counterflow thrust vector control (TVC) has been preferably employed to control the thrust direction of propulsive systems due to the simple design and low cost. The main objective of this study has been to produce a detailed understanding on the TVC performance of the circular type counterflow concepts by CFD method. Numerical results have been compared with the previous experimental results in circular models. The CFD results using k-ε realizable turbulence model have showed quite good match with the experimental results. A portion of the flow in the circular type is split from primary jet and go through the suction passage. TVC performance is adversely affected because of the space utilization rate. For a given NPRp, the jet attachment point moves upstream as secondary suction pressure goes down.
Numerical Study on the Performance of Scramjet Isolator
Ruoyu Deng,Heuy Dong Kim 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5
As one of the most promising propulsive systems in the future, the scramjet engine has drawn the attention of many researches. Detailed flow features concerned with the isolator play an important role in the scramjet system. The 2D numerical method has been used for the inlet-isolator with wind tunnel. In order to validate the ability of the numerical model, numerical results are compared with the experimental results. Overall pressure distributions show quite good match with the experimental results. Different back pressures have been researched for maximum pressure rising. According to the results, pressure profiles of inlet section are exactly the same in different back pressures, and the shock train is pushed toward the isolator entrance as the back pressure increases. The maximum back pressure without inlet unstart goes up rapidly and then keep constant when the isolator length increases. The optimal isolator length (L/Hth) is 8.7 in this model.