• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7941-7948
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• 2015

Rolling noises during train operation are caused by vibration excited from irregularities of surface roughness between wheel and rail. Therefore, a proper measurement and analysis techniques of acoustic roughness between wheel and rail surface are required for transmission, prediction, and analysis of the train rolling noise. However, since current measuring devices and methods use trolley-based manual handling devices, the measurements induce unstable measuring speed and vibrational interface that increases errors and disturbances. In this paper, a new automatic rail surface exploring platform with a speed controller has been developed for improving measurement accuracy and reducing inconsistency of measurements. In addition, we propose a data integration method of the rail surface roughness with multiple homogeneous displacement sensors and verified the accuracy of the integrated data through standard test-bed railway track investigation.

• Journal of the Korean Society of Hazard Mitigation
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• v.2 no.4 s.7
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• pp.69-75
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• 2002

In this paper the development of a real time river water quality management system is described. This system can manage a river water quality fluctuation by finding out abnormal conditions quickly and exactly. The GIS based monitoring system collects various properties of river water quality through the wireless real time network. Tanchun, the first branch of the Han River was selected as the target basin of the system development. This system is composed of three parts - wireless real time field measuring system with a GPS receiver, a server computer and a GIS platform. After the first field test in Tanchun basin, the result showed the many possibilities of measuring various water quality properties in real time and storing the data and analyzing them within the GIS environment in real time in very efficient manners. It is expected that the developed system will contribute to the efficient management of a river water quality control and water quality related disaster prevention purposes.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06b
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• pp.120-125
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• 2010

최근 스마트폰과 같은 다양한 애플리케이션을 사용할 수 있는 모바일폰의 유행에 힘입어 모바일 애플리케이션 수요가 폭발적으로 증가하고 있다. 이에 따라 모바일 애플리케이션에서의 품질의 중요성도 점차 커지고 있다. 하지만 모바일 애플리케이션은 다양한 플랫폼이나 모바일폰의 제약사항에 따라 호환성이 떨어지는 특성을 가짐으로써, 다른 플랫폼에서 애플리케이션을 재사용시 해당 플랫폼이나 모바일폰의 제약사항에 따라 다시 개발해야하는 제약을 가지게 한다. 이런 재개발은 플랫폼의 특성이 플랫폼 별로 상이함에 따라 개발에 어려움을 겪게 하고, 이는 애플리케이션의 품질을 저하시키는 요인이 될 수 있다. 따라서, 본 논문에서는 모바일 애플리케이션을 개발함에 있어서, 플랫폼에 비종속적인 범용 애플리케이션을 개발하기 위해 고려되어야 하는 이식성 척도들과 기존 애플리케이션의 이식성 품질 평가 방법을 제안한다. 이를 위해, 먼저 애플리케이션을 다른 플랫폼으로 이식할 때 고려되어야 하는 모바일 애플리케이션의 특성들을 확인하고, ISO/IEC 9126에서 정의한 소프트웨어 품질 특성 모델을 참조하는 이식성 척도를 도출함으로써 기존 애플리케이션에서 이식성을 평가하기 위한 방법을 설계한다. 이를 통해 모바일 애플리케이션의 타 플랫폼 이식 가능성을 확인함으로써 다른 플랫폼에서의 재개발 필요성과 노력 정도를 확인할 수 있을 것으로 기대된다. 향후 이를 기반으로 모바일 애플리케이션의 타 플랫폼 이식 시, 수정되어야 하는 부분을 확인할 수 있도록 하는 자동화된 이식성 테스팅 툴을 연구하고자 한다.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1433-1435
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• 2003

Very decisive progress was made in advancing fundamental POL-IN-SAR theory and algorithm development during the past decade. This was accomplished with the aid of airborne & shuttle platforms supporting single -to-multi-band multi-modal POL-SAR and also some POL-IN-SAR sensor systems, which will be compared and assessed with the aim of establishing the hitherto not completed but required missions such as tomographic and holographic imaging. Because the operation of airborne test-beds is extremely expensive, aircraft platforms are not suited for routine monitoring missions which is better accomplished with the use drones or UAVs. Such unmanned aerial vehicles were developed for defense applications, however lacking the sophistic ation of implementing advanced forefront POL-IN-SAR technology. This shortcoming will be thoroughly scrutinized resulting in the finding that we do now need to develop most rapidly POL-IN-SAR drone-platform technology especially for environmental stress-change monitoring with a great variance of applications beginning with flood, bush/forest-fire to tectonic-stress (earth-quake to volcanic eruptions) for real-short-time hazard mitigation. However, for routine global monitoring purposes of the terrestrial covers neither airborne sensor implementation - aircraft and/or drones - are sufficient; and there -fore multi-modal and multi-band space-borne POL-IN-SAR space-shuttle and satellite sensor technology needs to be further advanced at a much more rapid phase. The existing ENVISAT with the forthcoming ALOSPALSAR, RADARSAT-2, and the TERRASAT will be compared, demonstrating that at this phase of development the fully polarimetric and polarimetric-interferometric modes of operation must be viewed and treated as preliminary algorithm verification support modes and at this phase of development are still not to be viewed as routine modes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.4745-4750
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• 2011

A HIL(hardware-in-the-loop) system was established and the simulation was carried out to determine whether the system operates normally. The system consists of turbocharger test bench, HIL platform with real time S/W and DAQ, and engine model using Matlab/Simulink. In the simulation the supplied fuel rate is changed step-by-step from 1.8944 kg/h to 4.7360 kg/h. The change of air-fuel ratio is analyzed and observed whether the air-fuel ratio follow the target air-fuel ratio 32. When the supplied fuel rate is changed, the air-fuel ratio is converged to the target air-fuel ratio after about 20 seconds. And the vane duty ratio of turbine and the boost pressure of compressor are also changed properly. Therefore this HIL system can be used to develop the new turbocharger and improve the performance of the modified turbocharger.

• KIISE Transactions on Computing Practices
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• v.21 no.4
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• pp.320-326
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• 2015

With the growing concern over frequent occurrences of criminal events, help-requesting mobile applications have drawn attention. However, existing applications solely focus on providing help-requesting services. Therefore, in this paper, we design and implement a help request and response process which allows users to request help by sending messages and locating their friends, acquaintances and even near-by application users, and to allow help be reached by forwarding messages. This application is composed of three parts: help-requesting, help-responding, and checking-status. This application is developed on the Android platform where we exchange users' longitude and latitude through web server communication. We conducted test to verify the effectiveness of the forwarding function, and it has been confirmed that 93.33% of subjects used the forwarding function to help users at risk.

• Korean Journal of Construction Engineering and Management
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• v.21 no.4
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• pp.30-37
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• 2020

The purpose of this study is to compare and contrast the amount of overseas construction orders of South Korea and China by using various time series models that measure the overseas construction orders. Based on the analysis we propose better specification (model selection) with much more predictive power and prove the universality of the model developed by applying our findings with respect to the prediction power of overseas construction orders from other countries viewpoints (verification of generalization). The input variables include Dubai crude oil and exchange rates by country from 1981 to 2019. The VAR model is proposed based on the prediction power test, with respect to MAPE, RMSE, and MAE between the estimates and actual measurements from 2016 to 2019. We also conclude the results of the prediction of overseas construction orders time series of China are again consistent with the actual numbers. These analyses suggest the possibility of developing a comprehensive model that predict the potential construction orders of other countries.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.3
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• pp.485-492
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• 2008

Computers used fer light-weight computing environments are considerably limited in resources and performance running in ubiquitous environment. Because of the limited resources, it is difficult to apply existing security technologies to the light-weight computers. In this paper, light-weight security software is implemented using RC-5 encryption and SHA-1 authentication algorithm which is appropriate for light-weight computing environments. The design of components based on security software of a light-weight computer application and the test-bed for security software are presented. The simulation verifies the correctness of the security software. The architecture of the light-weight and reconfigurable security software for light-weight computer applications is proposed. The proposed security software is small size and provides reconfigurable security library based on the light-weight component and the software manager that configures software platform is loaded with the library at the time it is needed.

• Interaction and multiscale mechanics
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• v.3 no.2
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• pp.192-211
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• 2010

In most framed structures the nonlinearities and the damages are localized, extending over a limited length of the structural member. In order to capture the details of the local damage, the segments of a member that have entered the nonlinear range may need to be analyzed using the three-dimensional element (3D) model whereas the rest of the member can be analyzed using the simpler one-dimensional (1D) element model with fewer degrees of freedom. An Element-Coupling model was proposed to couple the small scale solid 3D elements with the large scale 1D beam elements. The mixed dimensional coupling is performed imposing the kinematic coupling hypothesis of the 1D model on the interfaces of the 3D model. The analysis results are compared with test results of a reinforced concrete pipe column and a structure consisting of reinforced concrete columns and a steel space truss subjected to static and dynamic loading. This structure is a reduced scale model of a direct air-cooled condenser support platform built in a thermal power plant. The reduction scale for the column as well as for the structure was 1:8. The same structures are also analyzed using 3D solid elements for the entire structure to demonstrate the validity of the Element-Coupling model. A comparison of the accuracy and the computational effort indicates that by the proposed Element-Coupling method the accuracy is almost the same but the computational effort is significantly reduced.

• Ocean Systems Engineering
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• v.5 no.3
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• pp.139-160
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• 2015

The global performance of the 5MW OC4 semisubmersible floating wind turbine in random waves was numerically simulated by using the turbine-floater-mooring fully coupled and time-domain dynamic analysis program FAST-CHARM3D. There have been many papers regarding floating offshore wind turbines but the effects of second-order wave-body interactions on their global performance have rarely been studied. The second-order wave forces are actually small compared to the first-order wave forces, but its effect cannot be ignored when the natural frequencies of a floating system are outside the wave-frequency range. In the case of semi-submersible platform, second-order difference-frequency wave-diffraction forces and moments become important since surge/sway and pitch/roll natural frequencies are lower than those of typical incident waves. The computational effort related to the full second-order diffraction calculation is typically very heavy, so in many cases, the simplified approach called Newman's approximation or first-order-wave-force-only are used. However, it needs to be justified against more complete solutions with full QTF (quadratic transfer function), which is a main subject of the present study. The numerically simulated results for the 5MW OC4 semisubmersible floating wind turbine by FAST-CHARM3D are also extensively compared with the DeepCWind model test results by Technip/NREL/UMaine. The predicted motions and mooring tensions for two white-noise input-wave spectra agree well against the measure values. In this paper, the numerical static-offset and free-decay tests are also conducted to verify the system stiffness, damping, and natural frequencies against the experimental results. They also agree well to verify that the dynamic system modeling is correct to the details. The performance of the simplified approaches instead of using the full QTF are also tested.