• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.4
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• pp.318-325
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• 2015

Pico satellite has limited surface to install the solar cells due to its extremely limited size. Also, the sun incidence angle with respect to the solar panel continuously varies according to the attitude control strategy and its important parameter for the power generation. In this study, a concentrating photovoltaic system for pico satellite application has been proposed that can enhance the power generation efficiency in case of the unfavorable condition of the sun incidence angle with respect to the solar panel of the satellite using the fresnel lens. To prove the possibility of maximizing the power generation efficiency of the proposed concentrating power system, we have performed the power measurement test using a solar simulator and commercial fresnel lens. And on-orbit analysis of the power generation efficiency using the STK which is a commercial S/W has also been performed based on the test results.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.6
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• pp.1-9
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• 2008

The current test methods are insufficient to evaluate and ensure the safety and reliability of vehicle system for all possible dynamic situation including the worst case such as rollover, spin-out and so on. Although the known NHTSA J-turn and Fish-hook steering maneuvers are applied for the vehicle performance assessment, they aren't enough to estimate other possible worst case scenarios. Therefore, it is crucial for us to verify the various worst cases including the existing severe steering maneuvers. This paper includes the procedure to search for other useful worst case based upon the existing worst case scenarios mentioned above and its application in simulation basis. The only human steering angle is selected as a design parameter here and optimized to maximize the index function to be expressed in terms of either roll angle or yaw rate. The obtained scenarios were enough to generate the worst case to meet NHTSA worst case definition (ex.2-inch wheel lift). Additionally, as an application, the worst case steering maneuver is acquired for the vehicle to operate with a simple ESP system. It has been concluded that the new procedure in this paper is adequate to create other feasible worst case scenarios for a vehicle system both with an intelligent safety control system and without it.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.1021-1026
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• 2000

The thermal characteristics of high-speed air spindle system with built-in motor are studied. Experiment and finite element method analysis obtain temperature rise and temperature distribution of housing. For the analysis three-dimensional model is built and temperature rise and distribution in thermal steady state are computed for each rotational frequency. Generally. It is said that the heat generation of air bearing is negligible. But it is certain that the heat generation of air bearing can not be negligible especially in high-speed conditions Frequency response test for air spindle system is executed. In case that the heat generation of air spindle system is high, natural frequency of the system becomes lower when it reaches thermal steady-state and it means that the stiffness of air hearing becomes smaller due to the change of bearing clearance. It is shown that the temperature rise of all spindle system causes thermal expansion md induces the variation of hearing clearance. In consequence the st illness of air bearing becomes smaller.

• Journal of Software Engineering Society
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• v.29 no.2
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• pp.13-20
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• 2020

The exploratory test was introduced as a desirable test method due to its fast development cycle, but it is not actively adopted because documentation and analysis of the test range are required for application. On the other hand, keyword-based testing has been introduced as a way to save resources and facilitate maintenance, but it is difficult to plan tests in advance due to the large number of variables such as data, settings, interactions, sequence and timing. However, in keyword-based testing, you can create a test case based on keywords by presenting clear criteria and methods for creating keywords and applying the exploration testing process. In this paper, we propose a model that automates exploratory tests based on keywords. To verify the effectiveness, we compared the general keyword-based test(KBT) and keyword-based exploratory test(KBET), and compared with the exploratory normal test case(ETC) and keyword-based exploratory test(KBET).

• Journal of Welding and Joining
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• v.22 no.4
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• pp.43-49
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• 2004

Conventional method for electrode force application in resistance spot welding(RSW) processes is to use pneumatic cylinder. However, due to its inherent problems in pneumatic power system such as compressibility of air and poor transient response characteristics, new electrode force system with servo control are recently introduced in RSW machine. This machine is called “servogun”. The purpose of this study is to evaluate performance of servogun in case of spot welding of aluminum alloy. Aluminum alloy(A5052) sheets are spot welded using pneumatic gun and servogun. Both results are compared by means of macro cross-section etching test and tensile shear strength test. Numerous previous research have reported nugget with many voids and cracks are not uncommon defects in spot welds with aluminum alloy. The experimental results show similar defects in case of pneumatic gun. In contrast, use of servogun considerably reduced generation of voids and cracks. In case of step-wise increased forging force at the end of welding cycle with servogun, crack-free and void-free nuggets have been observed. The performance of servogun has been also verified by series of tensile shear test. Higher strength values have been achieved with servogun in comparison to that of pneumatic gun.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.5
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• pp.541-545
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• 2010

AUTOSAR, a standard software platform for automotive, has been developed to manage software complexity and improve software reuseability. However reuse of test system is difficult because it is dependant on implementation language and test phase. In this paper, we suggest a test system generation method for AUTOSAR software component using TTCN-3, a standardized testing language. TTCN-3 test system is generated automatically from AUTOSAR XML containing software design information. The test system consists of TTCN-3 tester and target system and tests functionality and worst case response time of software under simulation environment. With the proposed testing techniques we can reduce time and effort to build the testing system and reuse testing environment.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.49-55
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• 2021

In this paper, an application example for fitness-for-service of material is shown. A kind of instrument valve is made of austenitic stainless steel fabricated by the cold working process. The tensile strength of the cold worked austenitic stainless steel has to be limited under 90 ksi to prevent the stress corrosion cracking in power plants. In industrial fields, tensile strengths of some materials were discovered to be over the regulation requirements in a certified material test report (CMTR). Owner's verification tests were performed to compare with that in a CMTR and to check the appropriateness. It is found that, in the case of verification test under the required test speed, valve materials could be used in the field. Although it is only one application sample of material check process in the power generation site, this case study could show an importance of basic experimental technology in academia and research circles.

• Journal of the Korean Home Economics Association
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• v.39 no.8
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• pp.107-120
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• 2001

The purpose of this study is to characterize the preference for fashion design according to fashion value of Net generation's. This study has 824 samples of individuals aged from 13 to 24. These sampling data are analyzed by frequency analysis, cross-tabs analysis, T-test, LSD-test, MANOVA and ANOVA utilizing SPSS WIN package. The results of this study are as follows; Net generation's is economic value higher than other fashion value and prefer for ring cuffs, mandarin sleeves, shirt collar, round neckline, tailored pants, blue color, check pattern according to economic value. It is proved that in case of shirt, people prefer ring cuffs, raglan sleeves, shirt collar, for jacket, prefer coat cuffs, mandarin sleeves, tailored collar, for jumper, they prefer single cuffs, set in sleeves, soutien collar and for T-shirt, prefer round neckline. For the design and length of pants, people prefer long tailored pants, color of blue and check designed one. It is proved that women haute a higher degree of preference for sleeve-design, neckline-design and color than men do.1318 teenagers have a higher preference for sleeve-design, neckline-design and color than semi-adult. Above university educational-course Net generation has a higher degree of preference for sleeve-design, neckline-design and color than high school educational-course Net generation does. A class of average monthly income of 2-3 million won has a higher degree of preference for neckline-design and color than other lasses do. And there is no difference at the preference for the fashion design when considered classes of average monthly expenditure on purchasing clothes.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.9
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• pp.469-478
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• 2001

It is difficult to test a distributed system because of the task of controlling concurrent events,. Existing works do not propose the test sequence generation algorithm in a formal way and the amount of message is large due to synchronization. In this paper, we propose a formal test sequence generation algorithm using logical clock to control concurrent events. It can solve the control-observation problem and makes the test results reproducible. It also provides a generic solution such that the algorithm can be used for any possible communication paradigm. In distributed test, the number of channels among the testers increases non-linearly with the number of distributed objects. We propose a new remote test architecture for solving this problem. SDL Tool is used to verify the correctness of the proposed algorithm and it is applied to the message exchange for the establishment of Q.2971 point-to-multipoint call/connection as a case study.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.10-13
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• 2008

Fuel cell systems have witnessed remarkable development in recent years as they offer a clean and efficient alternative for power generation. Testing was conducted to determine the safety performance of a residential fuel cell system when subjected to abnormal operation condition, especially for voltage sag and fuel cut. In case of voltage sag to 198V, its arriving time at rated power had shown a slight lag but there wasn't any noticeable change when operating it between rated voltage(220V) and 10% voltage sag(198V). In case of fuel cut, it also showed stable shut-down characteristics. The test results are being used to develop a new safety evaluation for residential fuel cell system.