• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.45-51
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• 2000

This paper studies the effect of vibrational characteristics of the various tubes analyzed though experiment. By an experiment analysis we found out that the factor of system vibration is fluid-structure interaction of tube line. In fluid-filled tube system we study on the influence that the natural frequency of system and the frequency of wave motion produce upon through three experiments. Three experiments are modal test on each tube, FRF in continuous system, and vibrating tests when the system is driving on. From the results of the experimental studies, we obtained that the natural frequencies of system are very important than wave induced vibrations. and according to the variation of configuration, the frequencies are different each other. And we found that though fluid passed away through the tube, the tendency of system vibration level was similar with the mode shape at the simple system.

• Corrosion Science and Technology
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• v.18 no.4
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• pp.117-120
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• 2019

Considering the tendency of development of electrification vehicles, development and verification of new evaluation technology is needed because of new technology applications. Recently, as the battery package is set outdoors of an electric vehicle, such vehicles are exposed to corrosive environments. Among major components connected to the battery package, rust prevention of high-voltage cables and connectors is considered the most important issue. For example, if corrosion of high voltage cable connectors occurs, the corrosion durability assessment of using an electric vehicle will be different from general environmental corrosion phenomena. The purpose of this study is to investigate the corrosion mechanism of high voltage cable connectors of an electric vehicle under various driving environments (road surface vibration, corrosion environment, current conduction by stray current, etc.) and develop an optimal rust prevention solution. To improve our parts test method, we have proposed a realistic test method to reproduce actual electric vehicle corrosion issues based on the principle test.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.120-127
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• 1996

Anti-lock Brake System has been developed to reduce tendency for wheel lock and improve vehicle control during sudden braking on slippery road surfaces. This is achieved by controlling the braking pressure, avoiding wheel lock, while retaining handling and brake performance. This paper is concerned about pressurecharacteristics of hydraulic modulator. Experimental sets which is consists of hydraulic modulator, duty controller, pressure regulator, pressure senset is consuructed. System modelling and computer simulation are performed for comparison with experimental results. Brake wheel pressure are measured under various driving pulse. The result of experiment show fairly agreement with the simulation. As a result, it is known that wheel pressure is affected by duty ratio, orifice diameter through computer simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.521-526
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• 2016

This paper suggests a new design that makes use of rotary inertia that can allow autonomous movement of an autonomous colonoscope robot in the colon of a patient as a locomotive mechanism. As commercial colonoscopy causes a lengthy time of pain and discomfort to the patients when colonoscopy patients are reluctant to receive surgery, there is a tendency to avoid the test in the early diagnosis of colorectal cancer. To solve this problem, research has been conducted on the next generation of robotic colonoscopes that can reduce the discomfort and pain by moving autonomously within the colon of the patients. In the driving mechanism utilizing the rotational inertia, a flywheel is driven by a motor to store energy and produce rotational inertia. By the energy stored and released by the flywheel, the stick phenomenon that occurs when the robot is running in the intestine can be overcome effectively. To do this, a controller that can control the velocity of the flywheel and is robust to high frequency noise was designed and implemented. The driving mechanism using the rotational inertia presented here showed that the structure is also effective and the experiment can be run easily compared to another mechanism.

• The Journal of the Korea Contents Association
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• v.19 no.2
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• pp.194-203
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• 2019

Recently, it is emphasized that the approach towards the development of smart cities as a driving force of sustainable economic growth of the city. Governments and municipalities are expected to expand the support for the smart city industry promotion, as the needs for smart city technology and service development, and investment for smart city industry increases. In order to promote the smart city policy as the driving force for the growth, it is necessary to understand the tendency of service development and its application. Governments and municipalities need a credible reference for their decision making on which smart city policy should be prioritized for the revitalization of the local economy by deploying certain smart city services according to the local industrial conditions. This study will analyze the trends of smart city services and suggest a reference data for decision making for the promotion of smart city industry.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.3
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• pp.149-157
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• 2012

For the systemic management and planning of future agricultural water resources, deriving and analyzing the various results of climate change are necessary to respond the uncertainties of climate change. This study assessed the impact of climate change on the rainfall, temperature, and agricultural water requirement targeting in the Nakdong-river's basin periodically according to socioeconomic driving factors under the scenarios A1B, A2 and B1 of the Special Report on Emission Scenarios (SRES) through the various IPCC GCMs. As a result of future rainfall change (2011~2100), increasing or decreasing tendency of rainfall change for future periods did not show a clear trend for three rainfall observatories, Daegu, Busan and Gumi. The characteristics of the temperature change consistently show a tendency to increase, and in the case of Daegu observatory, high temperature growth was shown. Especially, it was increased by 93.3 % in the period of future3 (2071~2100) for A2 scenario. According to the scenario and periodic analyses on the agricultural water demand, which was thought to be dependent on rainfall and temperature, the agricultural water demand increased at almost every period except during the Period Future1 (2011~2040) with different increase sizes, and the scenario-specific results were shown to be similar. As for areas, the agricultural water demand showed more changes in the sub-basin located by the branch of Nakdong-river than at the mainstream of the River.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.269-275
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• 2019

As the national industry is developing gradually due to the expansion of the economic scale, the construction of large and super high-rise structures for building social infrastructure has been increasing, and studies have been conducted actively to transmit the large loads at the upper portion to the lower bedrock. In this study, the PHC was extended to an ultra-high strength PHC, which increased the concrete compressive strength of the PHC from the conventional 80 MPa to 110 MPa, and the PHC, which extended the tip of the pile. After construction with the driving method and injected pile method, the tendency of the bearing capacity was tested through a load test. Measurements of the bearing capacity of the extended PHC using the pile driving method revealed the main surface friction force to be smaller than that of the general PHC, and the stet-up effect was also insignificant. On the other hand, the effect of the friction force on the ground surface when the injected pile method was applied is expected to increase the bearing capacity when the gap between the main surface and the ground is wide and the cement paste is filled tightly. In addition, the ultrahigh strength PHC showed higher bearing capacity than the conventional PHC, and the permissible pile stress was less than 60%. Therefore, it is possible to reduce the number of piles and reduce the construction cost and effect of shortening the length of the pile by designing the tip of the pile on the ground with the intensity of soft rock as a method for utilizing the increased strength of the ultra-high strength PHC.

• Journal of the Korean Ceramic Society
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• v.33 no.6
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• pp.645-652
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• 1996

The ionic conductivity of NASICON (Na Super Ionic Conductor) solid electrolyte was simulated by using Monte Carlo Method (MCM)based on a hopping model. We assumed that the conduction path of Na ions is Na1→mid-Na→Na2 where the mid-Na sites are shallow potential sites to induce 'a breathing-like movement' of Na ions in the NASICON framework. The minimum of charge correlation factor Fc and the maximum of appeared at nearby x=2.0 The occupancy of mid-Na site affected the depth of potential barrier and the conduc-tivity of the NASICON. At above x=0.3 ln σT vs. 1/T* plots have been shown Arrhenius behavior but in (VWfc)vs. 1/T* have been shown the Arrhenius type tendency at x=1 MCM results accorded with the experi-mental procedure. The role of mid-Na on Na+ ion conduction could be explained by an additional driving force and a breating-like movement model for motions of Na+ ions in the NASICON framework. As we couldn't clearly remarked the model which is the better it seems reasonable to conclude that these hypothesies are suitable to explain the FIC behavior at NASICON.

• Journal of Sensor Science and Technology
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• v.24 no.4
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• pp.258-263
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• 2015

In order to prevent drink-driving by detecting concentration of alcohol from driver's exhale breath, twenty chemical sensors fabricated. The one of purposes for sensor array which consists of those sensors is to discriminate between target gas(alcohol) and interference gases($CH_3CH_2OH$, CO, NOx, Toluene, and Xylene). Wilks's lambda was presented to achieve above purpose and optimal sensors were selected using the method. In this paper, step-wise sensor elimination based on Euclidean distance was investigated for selecting optimal sensors and compared with a result of Wilks's lambda method. The selectivity and sensitivity of sensor array were used for comparing performance of sensor array as a result of two methods. The data acquired from selected sensor were analyzed by pattern analysis methods, principal component analysis and Sammon's mapping to analyze cluster tendency in the low space (2D). The sensor array by stepwise sensor elimination method had a better sensitivity and selectivity compared to a result of Wilks's lambda method.

• Journal of Drive and Control
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• v.12 no.4
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• pp.54-59
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• 2015

Due to the tendency to use high speed pneumatic cylinders to improve productivity, cushioning devices are adopted to decelerate the piston motion of pneumatic cylinders to reduce noise, vibration, and impact. This paper presents a comparison of the cushion characteristics of a high speed pneumatic cylinder with a relief valve type cushioning device. The system parameters selected are the damping coefficient, Coulomb friction, heat transfer coefficient, and cracking pressure of the relief valve in the air cushioning device. The integral of the time multiplied square error (ITSE) is used to quantitative measure the cushioning performance to assess the effect of varying these. The cushioning performance achieved good results when the ITSE is a minimum value. In a comparison of the piston displacement and velocity with the variations in system parameters, the heat transfer coefficients are not as significantly affected as the other. Also, the cracking pressure of the relief valve is mainly affected by the pressure and temperature in the cushion chamber.