• The Journal of the Korea Contents Association
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• v.19 no.10
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• pp.607-619
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• 2019

This study used Natural Monument water spiders and their habitats as educational contents, so those students could have a scientific literacy and the beautiful memories of Eundaeri's marshes through developing a virtual fieldwork courses (VFC) and observing the ecology of water spiders. In order to develop the program, the 2015 revised national curriculum and its textbooks were analyzed. In accordance with the STEAM model, we developed teaching-learning materials for 7 classes. Students produced 3D panorama virtual fieldwork courses (PVFC) about water spider by team-based cooperative learning, enabling them to emotionally experience the meaning and value of water spiders. A panel of six education experts verified the validity of the program and found it to be fairly valid at 4.24 (CVI = .88) on the 5-point Likert scale. In order to confirm the suitability of the program, students in the middle school science clubs participated in pilot testing camp. Their average classes satisfaction was 4.24 and students were very satisfied with the usefulness of the program, the fresh learning contents, and the suitability of the convergence education class. This study could contribute to convergence education related to ecology and virtual reality for adolescents.

• Earthquakes and Structures
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• v.8 no.6
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• pp.1325-1348
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• 2015

Real-time hybrid testing (RTHT) involves virtual splitting of the structure into two parts: physical substructure that contains the key region of interest which is tested in a laboratory and numerical substructure that contains the remaining part of the structure in the form of a numerical model. This paper numerically assesses four step-by-step integration methods (Central difference method (CDM), Operator splitting method (OSM), Rosenbrock based method (RBM) and CR-integration method (CR)) which are widely used in RTHT. The methods have been assessed in terms of stability and accuracy for various realistic damping ratios of the physical substructure. The stability is assessed in terms of the spectral radii of the amplification matrix while the accuracy in terms of numerical damping and period distortion. In order to evaluate the performance of the methods, five carefully chosen examples have been studied - undamped SDOF, damped SDOF, instantaneous softening, instantaneous hardening and hysteretic system. The performance of the methods is measured in terms of a non-dimensional error index for displacement and velocity. Based on the error indices, it is observed that OSM and RBM are robust and performs fairly well in all the cases. CDM performed well for undamped SDOF system. CR method can be used for the system showing softening behaviour. The error indices indicate that accuracy of OSM is more than other method in case of hysteretic system. The accuracy of the results obtained through time integration methods for different damping ratios of the physical substructure is addressed in the present study. In the presence of a number of integration methods, it is preferable to have criteria for the selection of the time integration scheme. As such criteria are not available presently, this paper attempts to fill this gap by numerically assessing the four commonly used step-by-step methods.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.4
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• pp.1-13
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• 2022

Household refrigerator cabinets must undergo cyclic testing at -20 ℃ and 65 ℃ for quality control (QC) after their production is complete. These cabinets were assembled from different materials, including acrylonitrile butadiene styrene (ABS), polyurethane (PU) foam, and steel plates. However, different thermal expansion values could be observed owing to differences in the mechanical properties of the materials. In this study, a technique to predict delamination on a refrigerator wall caused by thermal deformation was developed. The mechanical properties of ABS and PU foams were tested, theload factors causing delamination were analyzed, delamination was observed using a high-speed camera, and comparison and verification in terms of stress and strain were performed using a finite element model (FEM). The results indicated that the delamination phenomenon of a refrigerator wall can be defined in two cases. A method for predicting and evaluating delamination was established and applied in an actual refrigerator. To determine the effect of temperature changes on the refrigerator, strain measurements were performed at the weak point and the stress was calculated. The results showed that the proposed FEM prediction technique can be used as a basis for virtual testing to replace future QC testing, thus saving time and cost.

• International Journal of Aerospace System Engineering
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• v.1 no.1
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• pp.10-15
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• 2014

This study presents technical description of the operating program development that operates the test bench for functional test of EECU. The test bench is capable of testing, simulation and adjustment of the EECU software using the operating program. The test bench is for the Development Project of the EECU platform for FADEC system. The operating program is consists of 3 modules which are the test bench operating module, cockpit simulator module and SILS module. The operating module mainly carries out the EECU test with manual operation and operating scenarios. Also that record and process the test data. The cockpit simulator module is capable of implementation of virtual cockpit control input and engine status display. The SILS module can simulate engine and EECU operation in software environment.

• Journal of the Korean Home Economics Association
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• v.47 no.3
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• pp.67-77
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• 2009

This study developed a model economic education program for young children related to Korean seasonal customs. The model was developed via literature reviews and survey research concerning teachers’' recognition of ‘'early childhood economic education’', consultations with professionals in the field, and testing and modifying the program. The goals of the model program were: teaching children to understand basic economic concepts, helping children to develop an economic attitude that emphasizes interdependence, and acknowledging the importance of eco-friendly economic values. The model includes three educational areas and 21 content areas including understanding the concept of exchange, sharing and cooperation, and circulation with nature. This study also developed 37 early childhood economic education activities using the teaching and learning methods of experiencing nature, virtual experience, real life experience, and traditional games experience.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2099-2104
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• 2015

The paper presents a monitoring system for the cooling of distribution transformers. The suggested system is controlled by a microcontroller scheme. The system is designed to control the oil temperature. It gives a solution to improve the cooling system by adding a number of fans especially for indoor transformers that are placed in badly-ventilated rooms. Also, the paper includes an alarm system with the possibility of tripping the transformer if it is necessary. The monitoring system consists of acquisition temperature sensor, and on-site unit. The hardware and software of the on-site unit are demonstrated with sufficient illustrations. Small prototype is constructed in the laboratory. Some laboratory experiments are carried out for examining the designed circuit by using Proteus Virtual System Modeling as well as for testing the prototype monitoring system. Concerning this research point, a study is carried out to evaluate the economic feasibility. The results are recorded and associated with many recommendations that may be valuable to electrical distribution (utility) companies.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.883-886
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• 1999

Recently, with the development of computer technology, field instrument and control system using in industrial fields have changed from mechanical, electrical systems to digital electronic systems. Distributed control system(DCS), control functions are dispersed for grading up reliability and informations are combined fur effective management has been developed and sold. As this system has been enlarged and complicated, it is difficult to testing the system and very important to verifing functions systematically. In this report, function test procedure which is performed spontaneously by domestic or foreign DCS manufacturer was searched and analyzed. As its results, the test procedure of DCS functions were proposed. The proposed procedure was applied to DCS being used for a thermal power plant. The function test for DCS requires continuous and dynamic input/output signals, therefore we proposed the method to compose virtual plant which simulate the DCS functions with. And we suggested the test procedure of each DCS function.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.604-608
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• 2010

This paper proposed a new 2D multibody dynamic modeling technique to analyze overriding behavior taking place during train collision. This dynamic model is composed of nonlinear spring, damper and mass by considering the deformable characteristics of carbodies as well as energy absorbing structures and components. By solving this dynamic model of rollingstock, collision energy absorption capacity, acceleration of passenger sections, impact forces applied to interconnecting devices, and overriding displacements can be well estimated. For a case study, we choose KHST (Korean High Speed Train), obtained crush characteristic data of each carbody section from 3D finite element analysis, and established a 2D multibody dynamic model. This 2D dynamic model was suggested to describe the collision behavior of 3D Virtual Testing Model.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.53-57
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• 2002

The solar energy is purity and infinity. Solar power converter were used to convert the electrical energy from the solar arrays to a stable and reliable power source. So many countries research this solar energy system The photovoltaic system is construct many solar cell array. In this paper, new implementation solar system was showed buck converter that V-I curve produced. This system can be used to study the short-term and long-term performances of solar cell and efficiency. This system is a far more cost effective and reliable replacement for field and outdoor flight testing. Study of buck converter, analysis and control series or parallels connection characteristics of solar cell way.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10a
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• pp.829-832
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• 2000

스팸 전자우편과 전자우편 폭탄을 차단하기 위한 제품들은 많이 나와 있지만, 이러한 차단 제품들의 성능에 대한 신뢰성 있는 검증 자료는 많지 않으며. 검증 결과도 벤더(vendor)들의 주관이 개입될 수 있기 때문에 객관성과 공정성 면에서 부족하다고 하겠다. 이것은 차단 제품들의 성능과 잠재된 취약성을 분석하는 분석 방식의 부족과 기존의 분석 방식들의 한계성에 기인한다고 하겠다. 본 논문에서는 기존의 분석 방식들이 가지고 있는 한계점을 개선하고, 제품의 취약성 분석 과정을 자동화하여 소요되는 시간과 인력 낭비를 줄이고, 반복적으로 분석이 용이하며, 분석 결과와 관련된 취약성 정보를 제공하여 비전문가라도 취약성 분석이 용이한 SMTP 서버 보호를 위한 취약성 분석 자동화 도구를 제안한다.