• Journal of KSNVE
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• v.10 no.5
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• pp.843-848
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• 2000

BEA(Boundary Element Analysis) based on Kirchhoff-Helmholtz integral equation is widely used in the prediction of sound radiation problems of vibrating structures. Accurate estimation of sound pressure distribution by BEA can be [possible if and only if dynamic behavior of the relating structure was described correctly. Another plausible method of sound radiation phenomena could be the NAH(Nearfield Acoustic Holography) method. NAH also based on the identical governing equation with BEA could be one of the best acoustic imaging schemes but it has disadvantages of the complexity of measurement and of the need of large amount of measuring points. In this paper, modal expansion method is presented for taking accurate dynamic data of the structures efficiently. This method makes use of vibration principle an arbitrary dynamic behavior of the structure is described by the summation of that structures mode shapes which can be calculated by FEA easily and accurately. Sound pressure field from a vibration flat plate is calculated using the combination of vibration signal on that flat plate from experiment, and of the natural mode shapes form FEA. When sound pressure field from vibration signal is calculated the importance of the phase information was emphasized.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.11
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• pp.599-609
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• 2000

The new design methodology of a hybrid fuzzy controller by means of the genetic algorithms is presented. First, a hybrid fuzzy controller(HFC) related to the optimal estimation of control parameters is proposed. The control input for the system in the HFC combined PID controller with fuzzy controller is a convex combination of the FLC's output and PID's output by a fuzzy variable, namely, membership function of weighting coefficient. Second, an auto-tuning algorithms utilizing the simplified reasoning method and genetic algorithms is presented to automatically improve the performance of hybrid fuzzy controller. Especially, in order to auto-tune scaling factors and PID parameters of HFC using GA, three kinds of estimation modes such as basic, contraction, and expansion mode are effectively utilized. The proposed HFC is evaluated and discussed to show applicability and superiority with the and of three representative processes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.66-76
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• 2003

The arbitrary V-notched crack problem is considered. The general expressions for the stress components on this problem are obtained as explicit series forms composed of independent unknown coefficients which are denoted by coefficients of eigenvector. For this results eigenvalue equation is performed first through introducing complex stress functions and applying the traction free boundary conditions. Next solving this equation, eigenvalues and corresponding eigenvectors are obtained respectively, and finally inserting these results into stress components, the general equations are obtained. These results are also shown to be applicable to the symmetric V-notched crack or straight crack. It can be shown that this solutions are composed of the linear combination of Mode I and Mode II solutions which are obtained from different characteristic equations, respectively. Through performing asymptotic analysis for stresses, the stress intensity factor is given as a closed form equipped with the unknown coefficients of eigenvector. In order to calculate the unknown coefficients. based on these general explicit equations, numerical programming using the overdetermined boundary collocation method which is algorithmed originally by Carpenter is also worked out. As this programming requires the input data, the commercial FE analysis for stresses is performed. From this study, for some V-notched problems, unknown coefficients can be calculated numerically and also fracture parameters are determined.

• YAKHAK HOEJI
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• v.49 no.6
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• pp.484-489
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• 2005

Streptococcus pmeumoniae is the leading cause of pneumonia and bacterial meningitis. The current polysaccharide vaccine has been reported ineffective in elderly adults and children less than 2 years of age. Thus, in recent many researchers have been focused on a different approach, DNA vaccine. In our laboratory we developed a Streptococcus pneumoniae DNA (SPDNA) vaccine. This SPDNA vaccine was formulated by inserting the region encoding part of the capsule in the S. pneumoniae into the LAMP-1. In present work, with use of the SPDNA vaccine we attempted to establish a certain methodology useful for evaluation of effectiveness and immunoresponse of a DNA vaccine. Results showed that the subcutaneous route was the most effective for production of antisera specific for S. pneumoniae in mice. By isotyping analyses, IgM, IgGl, IgG2a, and IgG2b were determined. In addition, INF-$\gamma$ and IL-4 were predominantly detected. Combination of those data resulted in a pattern of IgGl < IgG2a=IgG2b and INF$\gamma\>$ >IL-4, which indicates the inmmunity towards the Thl response predominantly; furthermore, the SPDNA vaccination induced resistance of the CD4+T lymphocyte-depleted mice against disseminated pneumococcal infection. These data appear to be possibly due to activation of CDS8+T cell-activation. Taken together, this methodology can be applied for evaluating efficacy and mode of action of a DNA vaccine as minimum critera.

• Steel and Composite Structures
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• v.24 no.4
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• pp.455-465
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• 2017

This paper presents a series of ultimate and fatigue experimental investigation on concrete-filled rectangular hollow section (CRHS) X joints with Perfobond Leister rib (PBR) under tension. A total of 15 specimens were fabricated, in which 12 specimens were tested under ultimate tension and 3 specimens were investigated in fatigue test. Different parameters including PBR stiffening, brace-to-chord ratio (${\beta}$) and inclined angle (${\theta}$) were considered in the test. Each joint was tested to failure under tension load. Obtained from test result, PBR was found to improve the tension strength and fatigue durability of CRHS joint substantially. Concrete dowel consisted by PBR and concrete inside the chord stiffened the joint, which leaded to a combination failure mode of punching shear and chord plastification of CRHS joint under tension. Finite element analysis validated the compound failure mode. Stress concentration on typical spot of CRHS joint was mitigated by PBR which was observed from fatigue test. Initial fatigue crack presented in CRHS joint with PBR also differentiated with the counterpart without PBR.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.446-453
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• 2000

The closed cycle diesel system is operated in closed circuit system where there is non air breathing with working fluid consisted of the combination of oxygen, argon and recycled exhaust gas for obtaining underwater or underground power sources. this study has been carried out to analysis the performance of closed cycle system by means of investigation on the combustion characteristics of diesel engine MTU8V183TE52 operating in open, semi-closed, and closed cycle modes. The combustion in closed mode starts a little bit earlier than in open cycle mode. The oxygen concentration and fuel consumption at 240kW closed cycle running are 21∼24% by volume and 77∼79kg/h, respectively. The maximum cylinder pressure and ignition delay time are investigated 110bar and 8.9degree. Also, The combustion simulation program has been studied to predict whether or not combustion. The results from numerical prediction for the basic, cylinder averaged quantities such as the cylinder pressure and the heat release showed excellent with the experimental data.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.513-517
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• 2006

Autonomous Underwater Vehicles plays specific role in underwater investigation. Generally, this kind of vehicles will move along a planned path for sea bottom or underwater installations inspections, search for mineral deposits along shelves, seeking lost items including bottom mines or for hydrographic measurements. A crucial barrier for it remains the possibility of precise determination of their underwater position. Commonly used radionavigation systems do not work in such circumstances or do not guarantee the required accuracies. In the paper some new solution is proposed on the assumption that it is possible to increase the precision by certain processing of a combination of measurements conducted by means of different techniques. Objective of the paper is the idea of navigation of AUV which consists of two phases: firstly a trip of AUV along pre-planned route and after that postprocessed transformation of collected data in post-processing mode. During the processing of collected data the modern adjustment methods have been applied, mainly estimation by means of least squares and M-estimation. Application of these methods should be associated with the measuring and geometric conditions of navigational tasks and thus suited for specific scientific and technical problems of underwater navigation. The first results of computer aided investigation will be presented and the basic scope of these application and possible development directions will be indicated also. The paper is prepared as an partial results of the works carried out within a framework of the research Project: 'Improvement of the Precise Underwater Vehicle Navigation Methods' financed by the Polish Ministry of Education and Science (No 0 T00A 012 25).

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1488-1489
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• 2006

Gas Discharge Tubes (GDTs) are widely used as surge protectors for communication applications due to their small internal capacitance. In these days, however, they are mostly used in combined configurations, because the activation voltage required to initiate the discharge process in the GDTs for sufficient amount of time can be large enough to damage surge-sensitive protected circuits. For GDTs with a considerably high initial over-voltage value, we should limit the peak voltage using a TVS or filter. As for ZnO varistors, even though their performance for voltage restriction is excellent their applications in high-frequency communication circuits have been limited because of higher internal capacitance when compared to the GDTs. In order to develop a surge protector for communication applications by taking advantages of these two devices, we built a combination circuit that connects a GDT and a ZnO varistor along with a choke coil in common and differential modes. We describe how the applied SPDs operate in protection process steps with the actual data obtained from the residual voltage measurements at each step. The experiment results show that the surge voltage restriction with the choke coil is more effective in differential mode than in common mode.

• Journal of Welding and Joining
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• v.16 no.3
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• pp.95-101
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• 1998

Waveforms of $CO_2$ gas shielded arc welding in short circuit transfer mode was studied with the waveform analysis program, which can calculate various waveform factors such as number of short circuit event, mean and standard deviation of short circuit time and arc time. The calculated values of these factors were correlated independently or in combination with the spatter generation rate to figure out the most reliable index for evaluating spatter generation and further for arc stability. As a result this study, it was confirmed that the spatter generation tends to decrease with the increase of short circuit frequency. Further to this, it was also found that as the short circuit frequency increases the short circuit event becomes more uniform resulting in the decrease of standard deviations ($\sigma$values) of short circuit time and arc time. This result demonstrated that these factors are strongly correlated with each other and thus any one of these factors can be used for the evaluation index. In the discussion, however, short circuit frequency was proposed for the most practical index in evaluating the arc stability of short circuit transfer mode since it is the one which could be monitored in-process condition without any complex caculation process.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.1
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• pp.123-130
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• 2008

An analytical method for the free vibration of a flexible rectangular plate in contact with water is developed by the Rayleigh-Ritz method. The plate clamped along the edges is partially contacted with water at both sides. It is assumed that the contained water is incompressible and inviscid. The wet mode shape of the plate is assumed as a combination of the dry mode shapes of a clamped beam. The liquid motion is described by using the liquid displacement potential and determined by using the compatibility conditions along the liquid interface with the plate. Minimizing the Rayleigh quotient based on the energy conservation gives an eigenvalue problem. It is found that the theoretical results can predict excellently the fluid-coupled natural frequencies comparing with the finite element analysis result.