• Journal of Ocean Engineering and Technology
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• v.25 no.1
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• pp.27-31
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• 2011

The previously developed method of estimating the propulsion performance of a UUV was applied to the high speed UUV, which is propelled by commercial thrusters. The thrusters were selected with an overdesign mentality; in other words, their capacities were excessive. At that point, the designer's concern was focused on a question regarding at what rpm the UUV could reach the design speed. Because the developed method required thrust coefficient curve data, the researchers asked for the POW data of the thrusters from the manufacturer. From the data, the researchers extracted the thrust coefficient and estimated the rpm value of design speed for the UUV. Finally, the researchers compared the estimated value and the result from a self-propulsion test using a VPMM (Vertical planar motion mechanism) test at a towing tank in MOERI.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.557-570
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• 2000

It is necessary to perform a study on the interrace between a G7 pantograph and a KTX catenary system prior to G7 on-line tests in the Korea High Speed Test Track in order to predict how high current collection quality can be obtained during the on-line tests and check if safety problems shall be caused b)Y the tests or not. According to the simulation results, current collection quality of the G7 pantograph at 350km/h is lower than that of a GPU pantograph at 300km/h, but the contact wire uplifts and average contact forces are within the safe-zone. In addition, the ratio of running speed (350km/h) to safe running. Therefore, the G7 on-line tests at 350km/h in the Korea High Speed Test Track is expected not to cause the safety problem.

• Journal of the Korean Society for Railway
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• v.6 no.2
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• pp.122-128
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• 2003

The acceptance test of KTX has been performed in Korea. During the test, lateral vibration of carbody over the accepted value called sway was found. Many activities have been taken to find the cause of the vibration and the counter-measure. KTX has 20 car trainset formation whose trailer cars are linked by articulate bogies. So this study is performed to see the effects of long trainset formation on vehicle dynamics and the train stability by 16 car vehicle model. Firstly the reliable vehicle model which shows well the tendencies appeared in the tests on the high speed test line is required to find the cause of lateral vibration and the countermeasure. Vehicle model was made for the analysis with VAMPIRE. The analysis results show that secondary air spring lateral stiffness is the most significant parameter to cause carbody lateral vibration. Mode analysis results show that the least damped mode shape is similar to the vibration pattern shown in the tests that the amplitude of the motion increases along the train set and decreases in the tail part. The lateral vibration was "appeared at the speed range between 100km/h and 200km/h and disappeared at the low speed and the high speed.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.9
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• pp.765-771
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• 2014

During the acceptance test of KTX, unexpectedly great lateral vibration in 14th~16th train at 150km/h~200km/h was appeared on a straight line in the winter season. Generally, stiffness of secondary suspension in KTX vehicle is one of the most sensitive components on air temperature. So, we examined that the secondary suspension to be mounted heating system was able to reduce the lateral vibration in the tail car of KTX. Also, we verified that lateral vibration from test results on KTX train with wheel conicity 1/20 disappeared. In this paper, we analysis effective reduction methods and the cause of the lateral vibration using model of KTX train and compare with the test results. The analysis results agree well with test ones. From mode analysis result, lateral vibration is occurred at natural frequency range 0.5~0.6Hz with a negative damping value and its natural frequency disappear gradually according to increasing of wheel concinicy.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2017.10a
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• pp.189-190
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• 2017

For the concept design of the device, a tool was made to test the simulated fuel rods and cutting force and the cutting force was measured. When 2-CUT and 3-CUT modules were used, the maximum force in 2-CUT at 12.5 mm/s speed change was $197.5kg_f$ and the maximum force at 3-CUT was $363.2kg_f$. The change of force in 2-CUT rapidly increases from about 1 second, and you can see that there are increase and decrease of the force change from about 5 seconds to 18 seconds, and it was rapidly decreased and the cut was made. The force change in 3-CUT has higher force at about 5 seconds later than 2-CUT at the speed of 12.5 mm/s, and you can see that it has the same tendency afterwards. If you search for the force at adequate speed from this cutting force test, 2-CUT module requires less slitting force than 3-CUT module, and the cutting time for 250 mm at 12.5 mm/s was 21 seconds, which can cut 4 m fuel rod in 5 minutes. But, there are cases of not completely slitting with 2-CUT module, so it is necessary to supplement this in the future through experiments.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.04a
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• pp.97-107
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• 1998

Three different kinds of brake discs including two coated brake discs and one steel disc were tested under the same experimental conditions on a reduced scale braking test bench. Braking test bench was specially designed to analyse thermo-mechanical and frictional behaviors of two sizes of brake discs in stop and hold braking modes. And Plasma spray coating technique was used to coat ceramic powder on the discs. In the test four commercial brake pads were coupled with discs. Ceramic coated discs had shown good stability in friction coefficient at high speed and high energy braking conditions. But they caused large pad mass wear loss compared with the steel disc. It was shown that thermal barrier effect in ceramic coated discs adjusted the thermal partition between pad and disc. For a steel disc, it had shown fluctuating friction coefficient at high speed but a fittie pad mass wear loss compared with ceramic coated discs.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.201-206
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• 2003

This study is test for STS304 specimen using bending and torsion state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed If summarize STS304 torsion result of fatigue test, is as following. Fatigue life prediction was available by Weibull statistics distribution, and 50% breakdown probability correlation equation was appeared as following.

• Wind and Structures
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• v.31 no.5
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• pp.419-430
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• 2020

Weibull distribution is a conspicuous distribution known for its accuracy and its usage for wind energy analysis. The two and three parameter Weibull distributions are adopted in this study to fit wind speed data. The daily mean wind speed data of Ennore, Tamil Nadu, India has been used to validate the procedure. The parameters are estimated using maximum likelihood method, least square method and moment method. Four statistical tests namely Root mean square error, R2 test, Kolmogorov-Smirnov test and Anderson-Darling test are employed to inspect the fitness of Weibull probability density functions. The value of shape factor, scale factor, wind speed and wind power are determined at a height of 100m using extrapolation of numerical equations. Also, the value of capacity factor is calculated mathematically. This study provides a way to evaluate feasible locations for wind energy assessment, which can be used at any windy site throughout the world.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.238-243
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• 2000

The effect of the temperature, the fatigue and the test speed on DEN(double edged notch) specimen which was made by the pp-rubber composites during fracture was stuied. DEN specimen was made on PP-rubber composites through the injection molding. With increasing temperature the fracture strength is linearly decrease and the fracture energy is first increase by $0^{\circ}C$ and after that decrease. In the same temperature the fracture strength during increasing the notch radius is hardly increase. The fracture behaviour at low and high test speed is different entirely. At high test speed plastic region is small and fracture behaviour was seen to brittle fracture tendency. The deformation mechanism of polypropylene-rubber composites during fracture was studied by SEM fractography. A strong plastic deformation of the matrix material ahead of the notch/crack occured. The deformation seem to be enhanced by a thermal blunting of the notch/crack.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.225-234
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• 2008

This study was carried out to select proper loading speed for deformation strength ($S_D$) of asphalt mixtures. Kim test using loading head of diameter(40mm) with radius(10mm) was conducted to measure $S_D$ in different loading speed (10mm/min, 30mm/min, 50mm/min, 70mm/min) and wheel tracking test was also conducted. The regression analyses between the So values and WT results were carried out by loading speeds. Higher $S_D$ was observed as increasing loading speed. This means that loading speed is a high influencing factor on $S_D$. The loading speed of 30mm/min was found as an optimum for better correlation with WT results than any other speeds from the regression analysis between $S_D$ and wheel tracking test results. $S_D$ value measured at other loading speed than 30mm/min has to apply the conversion coefficients.