• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.506-513
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• 2021

The durability and safety of reinforced concrete structures significantly depend on the reinforcement conditions, concrete cover thickness, cracks, and concrete strength. There are two ways to accurately determine the information on reinforcing bars embedded in concrete - the local destructive method and the non-destructive rebar detection test. In general, the non-destructive rebar detection tests, such as the electromagnetic wave radar method, electromagnetic induction method, and radiation method, are adopted to avoid damage to the structural elements. The moisture content and temperature of concrete affect the dielectric constant, which is the electrical property of concrete, and cause interference in the non-destructive rebar detection test results. Therefore, in this study, the effects of the electromagnetic wave radar method and electromagnetic induction method have been analyzed according to the temperature and surface moisture content of concrete. Due to the technological advancement and development of equipment, the average error rate was less than 5% in the specimens at 24℃, irrespective of their operating principles. Among the tested methods, the electromagnetic induction method showed very high accuracy. The electromagnetic wave radar method indicated a relatively small error rate in the dry state than in the wet state, and exhibited a relatively high error rate at high temperatures. It was confirmed that the error could be reduced by applying the electromagnetic wave radar method when the temperature of the probe was low and in a dry state, and by using the electromagnetic induction method when the probe was in a wet state or at a high temperature.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.2
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• pp.133-148
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• 2011

Construction sites are becoming larger and complex with the growth of national economy. Accordingly, it is important to identify real-time information about materials, equipments, and manpower during construction at sites. Even though research utilizing position tracking sensors has been conducted in architectural engineering fields, this area of research is almost nil in civil engineering fields. Therefore, a feasibility study to find a way to apply position tracking sensors to an in-situ tunnel construction site adopting conventional tunnelling method is performed in this study. A methodology is proposed that the progress management of the tunnelling work can be monitored by checking construction materials needed at job site and the safety management system can be assessed by checking distance between in-situ workers and construction equipments. The most representative materials were identified so that IT technology can be applied by attaching and monitoring sensors to the selected materials. Also, time of arrival (TOA) for a position determination technology along with a wireless network technology was chosen and build wireless network system. The adopted methodology was applied to an in-situ tunnelling site, and verified the usefulness of the proposed system.

• The KIPS Transactions:PartB
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• v.15B no.2
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• pp.113-122
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• 2008

While there are about 1 million color vision deficiencies in Korea, an assistive technology to digital contents of broadcasting and web for them remains scarce. In this study, we developed a generation method of the ICC profile to correct a graphic digital content adapted to various color perception characteristics of CVD by tuning the correction rules of the ICC profile by themselves. We tested the performance of the ICC profile to apply 10 Ishihara plates to the participants, 1 protanomaly, 1 protanomaly and deuteranomaly and 2 deuteranomaly. We used the color range information to build correction rules. Results of the test show that they passed Ishihara test by 97.5% success rate, compared to 20% success rate without it. The average time for them to spend to tune the customized ICC profile was about 13 minute without any diagnosis of specialist, any special instrument.

• Geotechnical Engineering
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• v.14 no.6
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• pp.45-56
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• 1998

In order to select a proper ground improvement technology and to assess the quality and rate of improvement in the soft deposits. it is essential to characterize in-situ properties of the soft marine clay layer that may have many thin silt or sand seams. In this paper, both piezocone and flat dilatometer tests were performed to characterize in situ properties of a marine clay. Both tests provided quite similar site classifications, and in both tests the penetration pore water pressure was the better indicator for the classification of marine clay layer, especially in which sand or silt seams are frequently interbedded. Undrained strengths determined by both the cone tip resistance and the excess pore water pressure measured from piezocone were very similar in clayey soil layers. And the untrained strength determined by dilatometer had an approximately average value of undiained strengths obtained from piezocone. In addition, the theoretical time factor that can consider pore pressure dissipation effect during cone penetration may provide a reliable estimation of the coefficient of consolidation, especially for a coastal site which includes many silt or sand fractions or seams.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.611-621
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• 2010

When an enemy platforms transmit electronic jamming or tracking interference signal to a friendly ship's radar, the radar have to avoid the jamming and to track targets continually without losing the targets with the electronic protection techniques. Electronic protection is an essential key for a platform to survive in electronic warfare, for this purpose, jamming simulator was developed to provide electronic warfare environments for the test and evaluate the effectiveness of radar's electronic protection techniques. Jamming simulator has ability to generate a variety of deception and noise jamming signals using the DRFM which minimize phase distortions of 1GHz broadband radar signal with the phase sampling method. This paper presents the design contents of the jamming simulator to process the analysis of broadband radar signal and generate jamming signal, also proposes the algorithms of the deception and noise jamming and verifies the effectiveness of the simulator by field trial.

• The Journal of Korean Institute of Information Technology
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• v.16 no.12
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• pp.41-47
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• 2018

The buoy-enabled underwater surveillance system is a device that is installed in a particular sea area and operated for a certain period of tine and moved to another sea area after recovery. In this paper, a mooring method which is applied for a buoy-enabled underwater surveillance system was selected to maintain installation and enure stable operation. Also, the structure of the mooring line was designed. Two-point mooring method was selected considering interference with the communication cable of array-assembly. The composite structure of buoy chain, nylon rope, and anchor chain is designed as the basic component of mooring line. For the verification of design, a numerical simulation and wave tank experiment were performed. Their results were confirmed similarity in test condition. Finally, the mooring lines were designed for the environment of the sea trial location. The mooring line produced by the final design confirmed the stability above the significant wave height considered in the design on the sea trial.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.1 no.1
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• pp.22-32
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• 2002

This paper describes about non-burial AVI (Automatic Vehicle Identification) system using general vehicle as probe car for obtaining more accurate traffic information while conserving road pavement surface. Existing spot traffic detectors have their own limits of not obtaining right information owing to its mathematical method. Burial AVI systems have some defects, causing traffic jam, needing much maintenance cost because of frequent cutting of loop and piezo-electric sensors. Especially, they have hard time to make right detection, when it comes to jamming time. Therefore, in this paper, we propose non-burial AVI system with laser trigger unit. Proposed non-burial AVI system is developed to obtain regional traffic information from normal Passing vehicle by automatic license number recognition technology. We have adapted it to national highway section between Suwon city and Pyong$\~$Taek city(9.5km) and get affirmative results. Vehicle detection rate of laser trigger unit is more than 95$\%$, vehicle recognition rate is 87.8$\%$ and vehicle matching rate is about 14.3$\%$. So we regard these as satisfying results to use the system for traffic information service. We evaluate proposed AVI system by regulation of some institutions which are using similar AVI system and the proposed system satisfies all conditions. For future study, we have plan of detailed research about proper lane number from all of the target lanes, optimal section length, information service period, and data fusion method for existing spot detector.

• Composites Research
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• v.28 no.4
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• pp.212-218
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• 2015

A large composite spar was manufactured using an automatic fiber placement (AFP) machine. To verify its structural performance, the weakest part of the structure, which is called 'corner radius', was tested under bending and examined by finite element analysis. Since the application of AFP machine to composite structure fabrication is still in early stage in Korea, this paper presents the summary of whole process for manufacturing composite spar using AFP machine from mandrel design and analysis to verification test. The deflection and stress by mandrel weight and AFP machine force, thermal deformation and natural frequency were all examined for mandrel design. The target structure was composite C-spar and cured in an autoclave. Test results were compared with nonlinear finite element analysis results to show that the structure has the strength close to the theoretical value. It was confirmed that the corner radius of the spar manufactured by AFP process showed deviation less than 20% compared with first ply failure strength. The results indicate that the AFP technology could be used for large scale composite structure production in the near future.

• The Journal of Engineering Geology
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• v.22 no.3
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• pp.275-281
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• 2012

Thermal distribution in soils must be considered in engineering designs and constructions, including estimates of frost heave and thaw settlement, infrastructure in cold regions, and geothermal systems. Because thermal conductivity is a key parameter for evaluation of thermal distribution in soils, it must be accurately estimated. The thermal conductivity of fine-grained soils has been widely studied in recent years; however, few studies have reported a reliable method for experimental measurement. The present study presents the results of an experimental investigation of the thermal conductivity of a saturated kaolinite-silica mixture with respect to the variation of dry density. Thermal conductivities were measured in Constant Rate of Strain (CRS) consolidation tests, and the experimental data were analyzed to evaluate the accuracy of the new measurement system. In addition, we present an evaluation method for predicting thermal conductivity in fine-grained soils.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.160-164
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• 1995

정보통신 시스템의 고속/고밀도화 요구에 따라 개발되고 있는 ATM(Asynchronous Transfer Mode) 교환기 시스템은 팬을 이용한 강제대류냉각 방식의 채택과 시스템이 설치되는 장소에 따른 여러 환경조건에 의한 진동 문제가 발생될 수 있다. 시스템의 진동으로 인한 피해중 커넥터 접촉부에서 전기적 특성의 변화는 고속으로 전송되는 신호의 왜곡을 유발시킬 수 있어 시스템 개발시 이에 대한 충분한 연구 및 시험이 요구되고 있다. 진동환경에서 커넥터 접촉부는 접촉면의 상대운동으로 인한 접촉저항의 증가와 순간적인 신호전달 중단을 가져오게 되며, 특히 PCB/Connector Assembly에서 커넥터 접촉부는 PCB(Printed Circuit Board)의 장착 조건 및 동적 거동에 따라 전기적 특성이 변할 수 있다. 시스템에서 커넥터의 동적 거동을 이해하기 위해서는 PCB를 포함하는 시스템내 여러 요소의 동적 특성 이해와 복잡한 해석과정이 요구되며, 시스템 개발자는 진동 환경에서 이것의 시험 결과에 따라 커넥터의 사용을 결정해야 할 것이다. 커넥터의 전기적 특성 시험법은 IEC, EIA드 여러 국제 규격에 제시되어 있으며, 본 연구의 대상이 된 ATM교환기 시스템에서 PCB/Connector Assembly의 진동환경에서 접촉저항 측정과 관련된 접촉저항 임계치 및 측정법은 IEEE 규격 및 Bellcore 규격에 규정되어 있다. Bellcore에는 주어진 진동시험주기 전후에 IEC 규격의 LLCR(Low Level Contact Resistance) 측정회로를 이용한 측정법이 규정되어 있고, 냉각팬 및 주위 환경진동이 가해지는 동안의 영향에 대한 시험법은 규정되어 있지 않다. 본 연구에서는 한국통신의 전자장비 운용환경시험 조건의 진동에서 ATM 교환기 시스템에 사용되는 PCB/Connector Assembly 커넥터 접촉부의 접촉저항 변화와 PCB 진동에 의한 영향을 시험하였다.proach)등이 제시되었고 평면파 영역에 한하여 해서되어져 왔다. 본 논문에서는 분할 접근 방법(Segmentation Approach)을 이용하여 다공 요소로 이루어진 소음기를 해석하는데 적용하였다.로 성능 및 안정도에 영향을 미치므로 주의 깊게 선정해야 한다. 방법의 실질적인 적용에는 어려움이 있다. 본 연구에서는 기존의 방법들의 단점을 극복할 수 있는 새로운 회귀적 모우드 변수 규명 방법을 개발하였다. 이는 Fassois와 Lee가 ARMAX모델의 계수를 효율적으로 추정하기 위하여 개발한 뱉치방법인 Suboptimum Maximum Likelihood 방법[5]를 기초로 하여 개발하였다. 개발된 방법의 장점은 응답 신호에 유색잡음이 존재하여도 모우드 변수들을 항상 정확하게 구할 수 있으며, 또한 알고리즘의 안정성이 보장된 것이다.. 여기서는 실험실 수준의 평 판모델을 제작하고 실제 현장에서 이루어질 수 있는 진동제어 구조물에 대 한 동적실험 및 FRS를 수행하는 과정과 동일하게 따름으로써 실제 발생할 수 있는 오차나 error를 실험실내의 차원에서 파악하여 진동원을 있는 구조 물에 대한 진동제어기술을 보유하고자 한다. 이용한 해마의 부피측정은 해마경화증 환자의 진단에 있어 육안적인 MR 진단이 어려운 제한된 경우에만 실제적 도움을 줄 수 있는 보조적인 방법으로 생각된다.ofile whereas relaxivity at high field is not affected by τS. On the other hand, the change in τV does not affect low field profile but strongly in fluences on both inflection fie이 and the maximum relaxivity value. The results shows a fluences on both inflection field and the maximum relaxivity v