• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.2
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• pp.41-48
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• 2018

In this study, the dynamic absorber and the damper are applied to improve the seismic performance of the piping system, and their quantitative effects on the piping system performance are examined. For this purpose, the response performances of piping system applied with the dynamic absorber/damper are compared with those of the original piping system. Firstly, the frequency response analyses of the piping system with the presence or the absence of dynamic absorber/damper are performed and these results are compared. It has been shown that the maximum acceleration response per the frequency of the piping system is considerably reduced by installing the dynamic absorber and the damper. Secondly, the seismic responses of the piping systems with and without dynamic absorber/damper are compared. As a result of the numerical analyses, it is confirmed that key responses are reduced by 17%-63% due to the installation of the dynamic absorber and damper. Finally, as a result of the seismic performance evaluation, it is confirmed that the HCLPF (High Confidence of Low Probability of Failure) seismic performances are increased by 1.22 to 2.70 times with respect to the failure modes with an aid of the dynamic absorber and damper.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.2
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• pp.190-201
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• 1985

Direct cutting tests was carried out to evaluate the dynamic performance of lathes under various cutting conditions. Significant factors influencing the chatter limits were identified through use of analysis of variance. Dynamic performances of two lathes were compared and the merits and drawbacks of the direct cutting test were discussed. Exciting-direct-cutting test method was newly proposed as a more rational method of dynamic performance test. The basic theory and experiments of the test were explained. The results shows that the method can be used as a powerful tool for the evaluation and the improvement of dynamic performance of machine tools.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.445-452
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• 1998

The dynamic performance design of catenary-pantograph system which collects current for the next generation Korean high speed train(KHST) was considered. Used was the same dynamic model of the catenary-pantograph system as that of TGV-K which will be introduced for Kyung-bu corridor. Using the model , sensitivity analysis fer design variables were made to improve dynamic performance of KHST system. The results of sensitivity analysis and performance improvement are as follows: (1) It was found that aerodynamic force, tension of contact wire, mass of contact strip, mass of supporting contact strip, mass of clamp, mass of steady arm, and stiffness of plunger were the design variables most influencing the dynamic performance of the system. (2) Pantograph with reductions of 20% aerodynamic force, 34% weight of supporting contact strip, 20% spring constant of plunger, and 34% equivalent mass of steady arm was very possible system for the KHST which will be running at maximum operating speed 350 km/h.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.114-122
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• 2009

An adaptive Kalman filter is designed as a post-navigation filter to improve the accuracy of GPS receiver's navigation performance in high dynamic environments. Not only the adaptive Kalman filter reduces the large noise error of navigation data which is obtained by least square method, but also the filter is not degraded as normal Kalman filter in high acceleration movements because the system noise is estimated. Also an initialization structure of the filter is desisted in consideration for irregular output condition of navigation data by least squared method such as reacquisition status in GPS receiver. The filter performance is verified by GPS simulator which has the simulation capability of high velocity and acceleration. Finally, a vehicle test including DGPS is executed to conform the real improvement of that filter performance. This filter can be applied to various data measurement systems to improve accuracy in high dynamic conditions besides GPS receiver.

• PNF and Movement
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• v.9 no.4
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• pp.13-21
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• 2011

Purpose : The purpose of this study was to analyze the effect of closed kinematic chain exercise and proprioceptive neuromuscular facilitation exercise on the static dynamic balance performance of hemiplegic patients in order to suggest them therapeutic intervention methods. Methods : The subjects of this study were 18 hemiplegic patients grouped into 2 subgroups according to the exercise program. one group of closed kinematic chain exercise carried out sit to stand, Hooklying with pelvic lift(bridging) and stair-up & down by a hemiplegic leg. The other group of proprioceptive neuromuscular facilitation exercise carried out leg flexion-extension pattern in supine position, leg flexion pattern in standing and stabilizing reversal exercise in stating position. Each exercise was carried out over 3 sets of 10reps. Results : The results of this study were summarized as follows: 1. For both groups, there were statistically significant changes in the static balance (FICSIT-4) performance after exercise program (p<.05). 2. For both groups, there were statistically significant changes in the dynamic balance (FSST, TUG, FRT) performance after exercise program (p<.05). 3. In the comparison between both groups, there was no statistically significant difference in the static dynamic balance performance (FICSIT-4, FSST, TUGT, ER) after exercise program. Conclusion : As the results of the study shows closed kinematic chain exercise and proprioceptive neuromuscular facilitation exercise affect the improvement of hemiplegic patients'' static dynamic balance performance, it is supposed that these exercises could be therapeutic exercise program in clinical situations.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.3
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• pp.294-303
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• 1999

Resistance spot welding is commonly used for welding products of high quality because of clean welding and short w welding-time. But. conventional spot welders bring about the depreciation of welding products, iuespective of dynamic r resistance characteristics during welding time. This paper discussed dynamic resistance database implementation in t terms of welding performance improvement. On different welding conditions, we compared dynamic resistance, r respectively, about pure iron and Sn-Pb alloy on Copper. Also, it investigated the relation of tensile shear strength and d dynamic resistance in welded workpiece.

• 한국기계연구소 소보
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• s.14
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• pp.17-31
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• 1985

The Primary object of this study is to predict rigid carbody's vertical and pitch acceleration and/or displacement frequency response to vertical sinusoidal rail surface irregularities for any specified point of the carbody, and to verify the predictions by means of experiments. The developed computer program also calculates vertical and pith transmissibilities and acceleration spectra. This model can be used for first order analysis of ride behabior. it's main advantage is its simplicity and ease of use. This model can be used for first order analysis of ride quality behabior. It's main advantage is its simplicity and ease of use. The model was designed with 6 degreed of freedom. Equations of motion were derived by Lagrangian method. This calculation was applied to the vertical dynamic analysis in order to pursue a possible improvement of the dynamic performance of co-co locomotive, and results were very useful.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.8
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• pp.727-733
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• 2010

Optical tables provide a platform for the establishment and test of measurement systems which use Laser. Therefore, not only static characteristics such as surface flatness, static stiffness and etc. but dynamic response characteristics is very important design parameter. The dynamic stiffness is generally estimated through the modal test, and compliance is used as a representative performance standard. Recently there is an example of defining the dynamic deflection coefficient and using it as a new performance standard of the dynamic stiffness, but it is not generalized yet in industry. In this study, we verify the validity of existing DDC calculus by making an experiment on granite. And for improvement in damping performance of optical tables, we are going to evaluate the effect of fillers on the compliance, then develop an epoxy adhesive based on the result of this experiment.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.125-128
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• 2003

In this paper, we propose a dynamic key lifetime change protocol for performance enhancement of virtual private networks using IPSec. The proposed protocol changes the key lifetime according to the number of secure tunnels. The proposed protocol is implemented with Linux 2.4.18 and FreeS/WAN 1.99. The system employing our proposed protocol performs better than the original version in terms of network performance and security.

• Journal of Power Electronics
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• v.12 no.1
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• pp.145-156
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• 2012

These days, the application of electronic power transformers (EPTs) is expanding in place of ordinary power transformers. These transformers can transmit power via three or four wire converters. Their dynamic performance is extremely important, due to their complex structure. In this paper, a new method is proposed for improving the dynamic performance of distribution electronic power transformers (DEPT) by using sliding mode control (SMC). Hence, to express the dynamic characteristics of a system, different factors such as the voltage unbalance, voltage sag, voltage harmonics and voltage flicker in the system primary side are considered. The four controlling aims of the improvement in dynamic performance include: 1) maintaining the input currents so that they are in sinusoidal form and in phase with the input voltages so they have a unity power factor, 2) keeping the dc-link voltage within the reference amount, 3) keeping the output voltages at a fixed amount and 4) keeping the output voltages in sinusoidal and symmetrical forms. Simulation results indicate the potential and capability of the proposed method in improving DEPT behavior.