• Journal of the Korean Society for Railway
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• v.20 no.3
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• pp.311-319
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• 2017

The primary suspension system of a railway vehicle restrains the wheelset and the bogie, which greatly affects the dynamic characteristics of the vehicle depending on the stiffness in each direction. In order to improve the dynamic characteristics, different stiffness in each direction is required. However, designing different stiffness in each direction is difficult in the case of a general suspension device. To address this, in this paper, an optimization technique is applied to design different stiffness in each direction by using a conical rubber spring. The optimization is performed by using target and analysis RMS values. Lastly, the final model is proposed by complementing the shape of the weak part of the model. An actual model is developed and the reliability of the optimization model is proved on the basis of a deviation average of about 7.7% compared to the target stiffness through a static load test. In addition, the stiffness value is applied to a multibody dynamics model to analyze the stability and curve performance. The critical speed of the improved model was 190km/h, which was faster than the maximum speed of 110km/h. In addition, the steering performance is improved by 34% compared with the conventional model.

• Journal of The Korean Society For Urban Railway
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• v.6 no.4
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• pp.233-241
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• 2018

Recently, integrated railway safety monitoring and control system, which is a convergence system based on data distribution service for railway safety monitoring and control, is under development. It collects safety data of vehicle, signal, power and safety monitoring facilities in real time and adopts communication middleware based on distributed service for mass data processing. However, in the case of a server device used as an existing control server, the performance of the distributed service middleware can not be exhibited due to low hardware performance due to safety reasons. In the safety control system, 200,000 packets per second were set as the transmission target, but the performance test of the LAB was not satisfied. In this paper, we analyze the characteristics of railway data to improve the data collection performance of existing equipment and apply DDS-based streaming transmission method to the data model of signal facilities and vehicle facilities with large packet amount according to the analysis result. As a result, it was confirmed that the throughput was improved about 30.4 times when the hardware performance was the same. We plan to improve the data processing performance by applying it to real-time railway safety integrated monitoring and control system in the future.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.5
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• pp.499-506
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• 2019

This paper is concerned with the operating stability of 7kW inverter using SIC hybrid module and verifies the validity of the simulation results by comparing the result of the loss equation and the simulation result, Simulation results using Si module and SiC hybrid module are compared to compare switch loss and diode loss. Through the loss equation calculation, the conduction loss of SiC Hybrid module is 168W, switching loss is 9.3W, diode loss is 10.5nW, When compared with the simulation results, similar values were shown. As a result of comparing the simulation results of the Si module and the SiC Hybrid module, The total device loss of the Si module was 246.2W, and the total device loss of the SiC Hybrid module was 189.9W. The loss difference was 56.3W, which was about 0.8W. thereby verifying the reverse recovery characteristics of the SiC SBD. In addition, temperature saturation test was conducted to confirm the stability of SiC Hybrid module and Si module under high temperature saturation, In the case of the Si module, the output power was stopped at 4kW, and the SiC Hybrid module was confirmed to operate at 7kW. Based on this, an efficiency graph and a temperature graph are presented, and the Si module is graphed up to 4kW and the SiC Hybrid module is graphed up to 7kW.

• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.161-167
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• 2019

In this paper, the performance verification of an around-view sonar and an excavation depth measuring sonar applicable to track-based ROVs (Remotely Operated underwater Vehicles) for heavy duty work is studied. For the performance verification, an experiment is carried out in a water tank and at sea by attaching the around-view sonar and the excavation depth measuring sonar for a heavy work ROV. In the case of the around-view sonar, image sonars are mounted on ROV in four directions (front, back, left and right) and in the case of the excavation depth measuring sonar, the same kind of MBES (Multi Beam Echo Sounder) is mounted on the front of the ROV. The result of an operation test of the ROV equipped with these sonars shows that the sonar systems are rarely affected by high turbidity due to sedimentation during the operation. In the case of the around-view sonar, it is possible to see rock formation, gravel and sandbank 30 m ahead of the ROV. It is confirmed that the excavation depth can be measured after the ROV has performed the excavation. This experiment demonstrates that the ROV can improve the efficiency of the work by utilizing the around-view sonar and the excavation depth measuring sonar.

• Journal of Digital Convergence
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• v.17 no.11
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• pp.207-213
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• 2019

The fuel-cut coast-down driving mode is activated when the acceleration pedal is released with transmission gear engaged, and it's a default function for electronic-controlled engine of vehicles. The fuel economy becomes better because fuel injection stops during fuel-cut driving mode. A fuel-cut detection method is suggested in the study and it's based on the speed, acceleration and road gradient data from GPS sensor. It detects fuel-cut driving mode by comparing calculated acceleration and realtime acceleration value. The one is estimated with driving resistance in the condition of fuel-cut driving and the other is from GPS sensor. The detection accuracy is about 80% when the method is verified with road driving data. The result is estimated with 9,600 data set of vehicle speed, acceleration, fuel consumption and road gradient from test driving on the road of 12km during 16 minutes, and the road slope is rather high. It's easy to detect fuel-cut without injector signal obtained by connecting wire. The detection error is from the fact that the variation range of speed, acceleration and road gradient data, used for road resistance force, is larger than the value of fuel consumption data.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.1
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• pp.174-192
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• 2021

The LIDAR sensor, which provides higher cognitive performance than cameras and radar, is difficult to apply to ADAS or autonomous driving because of its high price. On the other hand, as the price is decreasing rapidly, expectations are rising to improve existing autonomous driving functions by taking advantage of the LIDAR sensor. In level 3 autonomous vehicles, when a dangerous situation in the cognitive module occurs due to a sensor defect or sensor limit, the driver must take control of the vehicle for manual driving. If the driver does not respond to the request, the system must automatically kick in and implement a minimum risk maneuver to maintain the risk within a tolerable level. In this study, based on this background, a LIDAR-based LKS MRM algorithm was developed for the case when the normal operation of LKS was not possible due to troubles in the cognitive system. From point cloud data collected by LIDAR, the algorithm generates the trajectory of the vehicle in front through object clustering and converts it to the target waypoints of its own. Hence, if the camera-based LKS is not operating normally, LIDAR-based path tracking control is performed as MRM. The HAZOP method was used to identify the risk sources in the LKS cognitive systems. B, and based on this, test scenarios were derived and used in the validation process by simulation. The simulation results indicated that the LIDAR-based LKS MRM algorithm of this study prevents lane departure in dangerous situations caused by various problems or difficulties in the LKS cognitive systems and could prevent possible traffic accidents.

• Journal of Space Technology and Applications
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• v.2 no.1
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• pp.52-65
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• 2022

Korea is near close the success on the indigenous launch vehicle KSLV-2 after the second test launch during the second half of 2022, and the satellite development has been already in the level of advanced country. After the such mature of satellite and launch vehicle technologies, Korea's space development main theme should be 'Space Exploration and Space Application', and paradigm should be changed from 'Hardware' to 'Scientific/Technological Mission', from 'Unmanned' to 'Manned'. Korea's prime space strategy should be the direction of expansion of space industry, creation of employment and secure the key technologies, improvement of convenience and safety of people. For the purpose it is necessary to start 'Manned Space Development' such that participation to 'Artemis and Gateway Program' in 20s' and manned Mars exploration in 30s' which would be carried out by means of global international cooperation, and which could be a good opportunity to explore the new area of space development and upgrade national technology capability. Taking advantage of this opportunity, it is required for Korea to join the international programs through developing indigenous challenging, sustainable Korean mission and hardware. Also selection of the 2^nd Korean Astronaut could draw national attention, especially could give dreams to young generation. Participation to the Artemis program could be the opportunity of entering the major space fairing nation and boosting up national pride. In this study we survey and analyze the Artemis Program in detail, and in conclusion we suggest the strategy of Korea's participation to the Artemis Program.

• Resources Recycling
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• v.31 no.4
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• pp.3-11
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• 2022

Owing to the increasing demand for electric vehicles (EVs), appropriate management of their waste batteries is required urgently for scrapped vehicles or for addressing battery aging. With respect to technological developments, data-driven diagnosis of waste EV batteries and management technologies have drawn increasing attention. Moreover, robot-based automatic dismantling technologies, which are seemingly interesting, require industrial verifications and linkages with future battery-related database systems. Among these, it is critical to develop and disseminate various advanced battery diagnosis and assessment techniques to improve the efficiency and safety/environment of the recirculation of waste batteries. Incorporation of lithium-related chemical substances in the public pollutant release and transfer register (PRTR) database as well as in-depth risk assessment of gas emissions in waste EV battery combustion and their relevant fire safety are some of the necessary steps. Further research and development thus are needed for optimizing the lifecycle management of waste batteries from various aspects related to data-based diagnosis/classification/disassembly processes as well as reuse/recycling and final disposal. The idea here is that the data should contribute to clean design and manufacturing to reduce the environmental burden and facilitate reuse/recycling in future production of EV batteries. Such optimization should also consider the future technological and market trends.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.504-512
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• 2021

Sperm formation disorders and sperm quality degradation comprises the largest proportion of male infertility caused by TCDD. To solve this problem, this study examined the effects of Gobonyangjeonbang oriental medicine prescription on the endocrine function and reproductive toxicity-related indicators in rat-induced TCDD-induced reproductive. Male SD rats were divided into five groups of seven animals and tested. The normal control group was administered the vehicle and saline, the TCDD alone group was administered intraperitoneally with TCDD (2 ㎍/kg, weeks) and physiological saline, and the test group was administered orally by dividing GYB (75, 150, and 300 mg/kg) into three concentrations for six weeks. Weight loss was observed in all groups administered TCDD. Regarding the hormonal changes, a significant decrease in free testosterone was observed in the GYB 300 mg/kg group (p<0.01). In addition, some of the germ cell destruction, seminiferous tubular atrophy, and decrease in sperm count was improved in a concentration-dependent manner in the testicular tissue of the GYB-treated group. In addition, Johnsen's score and serotoli cell index (SCI) were improved in a concentration-dependent manner (p<0.05). Overall, GYB can be used in drug therapy rather than medical procedures to solve male infertility in the future.

• Korean journal of applied entomology
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• v.61 no.1
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• pp.267-274
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• 2022

Portable and vehicle thermal fogs were tested using etofenprox, bifenthrin, and deltamethrin diluted with diesel oil, kerosene, and water against domestic vector mosquitoes, Aedes albopictus, Anopheles sinensis s.l., Culex pipiens, and Culex tritaeniorhynchus. The female mosquitoes were confined in small cages suspended on poles at progressively greater distances from the fog release point at an open field. The average mortality rates of four vector mosquitoes to the three insecticides were 52.0% and 64.0% at a portable thermal fogs diluted with diesel oil and water within a 10 m distance, respectively. A vehicle thermal fog had a mean mortality of 34.8% of the females to the insecticides diluted with diesel oil within 50 m. The mortality rates were not significantly different among all the tested distances. At a dilution solvent test, the mortality of the females to the insecticides diluted with kerosene was 1.9 times higher than that of diesel oil.