• 기계와재료
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• v.25 no.3
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• pp.130-136
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• 2013

철도차량용 제동장치 성능시험기는 제륜자의 마찰계수, 마모량, 열반점 등의 물리적 성질을 실차와 유사한 환경조건에서 시험을 수행함으로써 제륜자의 연구개발 및 성능평가의 목적으로 활용한다. 제륜자는 차량의 운동에너지를 열에너지로 변환한다. 성능시험기는 철도차량의 주행 운동에너지에 해당하는 관성질량으로부터 회전 운동에너지에 해당하는 관성모멘트를 조성하여야 한다. 공용 시험기에서 각종 철도차량에 대한 관성모멘트를 기계적 관성모멘트인 플라이휠로 모의하기에는 용량도 크고 구조가 복합하여 현실적으로 한계가 있다. 본 연구에서는 기계적 관성모멘트의 한계를 극복하고자 전기적 관성모멘트를 부가적으로 활용하는 기법을 제시하고 이를 적용한 시험기를 소개하고자 한다. 이러한 연구는 시험기의 외형적인 크기를 줄이고 또한 각종 철도차량에서 요구하는 정량적인 관성질량의 모의가 가능하리라고 사료된다.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.820-823
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• 2008

본 논문은 기존의 XIP 기법에서 발생할 수 있는 메모리 접근 성능저하를 해결하기 위한 동적 XIP 기법을 제안하였다. 동적 XIP 기법은 상대적으로 성능저하가 적을 것으로 예상되는 코드 페이지들을 동적으로 선택하여 XIP 영역으로 설정하고, 성능저하가 크게 나타날 것으로 예상되는 코드 페이지들을 램 캐시에 캐싱하여 성능을 향상시킨다. 본 논문은 램 캐시를 관리하기 위해 MIN 캐시 알고리즘 및 메모리 접근 비용을 고려한 오프라인 캐시 알고리즘과, 페이지 접근에 대한 최신성(Recency) 및 슬라이딩 윈도우에 저장된 페이지 접근 기록에 기반하여 메모리 접근 비용을 예측하는 온라인 캐시 알고리즘, 온라인 캐시 알고리즘의 램 캐싱 판단의 정확성을 높이는 기법을 제안하였다. 본 논문은 온·오프라인 알고리즘의 성능비교를 위해 시뮬레이터를 통해 성능을 평가하였고, 유용성을 시험하기 위해 온라인 알고리즘을 리눅스를 기반으로 구현하여 성능을 평가하였다. 본 논문에서 제안한 동적 XIP는 실제 구현한 환경에서 실험한 결과, 작은 크기의 캐시를 사용하고도 수행시간에서는 최대 27%, 에너지 소모량에서는 최대 24%의 성능이 향상됨을 보였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.188-188
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• 2022

선박의 운용 효율을 높일 수 있는 방법인 무인 운용체계는 근래에 많은 관심을 받고 연구되어 왔다. 특히 무인수상선과 무인수중체의(USV-AUV)의 복합 운용 분야는 그 동안 어려움이 있었던 심해저 탐사 및 특수 임무 활용에 용이하여 많은 연구가 수행되고 있다. 본 연구에서는 쌍동선 형태인 무인수상선이 모선이 되고 무인수중체가 결합하여 충전하고 다시 진수하여 원거리 및 심해저 조건에서 무인수중체가 운용 가능하도록 하는 시스템의 일부인 USV-AUV의 docking을 위한 DP 시스템을 개발하고 선박해양플랜트연구소 해양공학수조에서 모형시험을 통해 이를 검증하였다. 또한, 실제 제작된 무인쌍동선과 추진 시스템을 활용하여 모형시험을 통해 검증한 DP 알고리즘을 적용하여 화성 제부도 앞바다에서 실선 DP 테스트를 수행하였다. 실 해역에서의 DP 시스템 테스트는 정확한 환경 조건의 계측 및 구현이 어려워 모형시험과 같은 정량적인 평가는 어렵지만, 정성적으로 DP 시스템이 작동하는 것을 확인할 수 있었다.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1139-1144
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• 2019

A calibration system for diagnosing and confirming the performance of precision measuring instruments minimizes the risk of misjudgment of calibration resulted by complying with international standard requirements in order to ensure the reliability of calibration results. This paper uses a proposed calibration system suitability assessment and a guard-band technique through an analysis of uncertainty factors when it is impossible to acquire and operate high-performance equipment at a calibration laboratory, and proposes an optimized test limit output model substituting performance standards. The proposed method provides an optimized test standard to meet the quantitative evaluation criteria of the calibration system and the probability of false acceptance risk required by international standards.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.110-114
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• 2009

This study is for the evaluation of compressive strength restoration of sandwich composite laminates with adhesively bonded scarf patches. It was used in this study that the sandwich composite laminate with an aluminum honeycomb core and CF1263 woven fabric carbon/epoxy faces was applied to the car body structure for Korean tiling train. In this study, it was damaged by low velocity impact and repaired using scarf repair method. Then, the compressive strength restoration of assessed by compressive after impact (CAI) test. From the test, it could be known that the compressive strength was restored up to 72% by only scarf repair method and 91% applied by an extra ply over the undamaged one.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.5
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• pp.525-531
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• 2004

In this paper, the concept of infrared thermography(IRT), the principle of measurement of IRT and how to set up the IR camera for the nondestructive testing are described in detail. Also, its utilization and non-destructive testing(NDT) diagnosis are reviewed. By performing the periodic non-touched WDT through the estimation of thermal patterns related with the temperature for the surface targeted, IRT can be applied to the early prevention of the device failure. For the diagnosis utilization, thermal imaging patterns obtained from IRT for heated blocks with internal defects were estimated through the lion-destructive method and discussed the way of IRT estimation from the analysis of characteristics between material defects and thermal imaging patterns.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.12
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• pp.1086-1092
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• 2012

It has been studied for DGPS/INS(Differential Global Positioning System/Inertial Navigation System) to offer the more precise and reliable navigation data with the aviation industry development. The flight performance evaluation of navigation system is very significant because the reliability of navigation data directly affect the safety of aircraft. Especially, the high-level navigation system, as DGPS/INS, need more precise flight performance evaluation method. The performance analysis is performed by comparing between the DGPS/INS navigation data and reference trajectory which is more precise than DGPS/INS. The GPS receiver, which is capable of post-processed CDGPS(Carrier-phase DGPS) method, can be used as reference system. Generally, the DGPS/INS is estimated the CG(Center of Gravity) point of aircraft while the reference system is output the position of GPS antenna which is mounted on the outside of aircraft. For this reason, estimated error between DGPS/INS and reference system will include the error due to lever arm. In order to more precise performance evaluation, it is needed to compensate the lever arm. This paper presents procedure and result of flight test which includes lever arm compensation in order to verify reliability and performance of DGPS/INS more precisely.

• International Journal of Highway Engineering
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• v.5 no.4 s.18
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• pp.23-35
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• 2003

In this study, compaction evaluating program based on ASTM critria is developed bu analyzing the results of laboratory tests. And the laboratory tests such as compaction test, triaxial test and resonance column test of subgrade soils are performed to develop compaction management methodology at seven test sites. Especially, to figure out chararteristic with changing compactive efforts, the test was carried out at five levels of compactive efforts at each soil sample. Database was set up from the test results. With the methodology using mechanical property - the elastic modulus, the gap between road design and management and road construction management is narrowed. The regression equation of G/$G_{max}$ is proposed at each strain level of subgrade soils according to AASHTO criteria, and the relationship between fundamental properties of soil mass and degree of compaction is derived as well. The development of compaction management and field compaction management method is proposed by the elastic modulus based on mechanical tests.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.135-148
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• 2001

In this study, an assessment method was proposed to evaluate the pullout resistance between geosynthetic and backill soil by using a stress-strain relationship of the orthotropic composite material subjected to both longitudinal and vertical loadings. For this analysis friction characteristics of geosynthetic-soil and stress-strain relationships subjected to soil confined pressure were investigated by performing the laboratory pullout tests for three types of geosynthetics and performing the confined extension tests far seven types of geosynthetics having geotextiles, composite geosynthetics and geogrids. A comparison was made between unconfined an confined moduli far each geosynthetic material to quantify the soil confinement effect on stress-strain properties. A comparison was also made between the relative increase of moduli at the same strain level among the seven geosynthetic materials to demonstrate the different responses of these geosynthetic materials under soil confinement. Based on the proposed procedure, it was shown that values of the increased tensile force are applicable fur the evaluation of friction strengths between five types of geosynthetics and sands in light of the soil confinement effect.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.1-8
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• 2017

An experimental study is needed a reinforcing method for seismic load to apply for RC structures because a lot of earthquakes have frequently happened in the world and those also collapsed infrastructures or damaged human lives. The reinforcing effect of PolyUrea (PU) appeared to be excellent under blast and impact about RC structures. In this study, Stiff Type PolyUrea (STPU) had developed by manipulating the ratio of the components of prepolymer and hardener of PU. And the durability performance evaluation of STPU for deterioration and chemical resistance has been performed. Acid environmental exposure test and ultraviolet (UV) exposure test have been performed as the durability performance evaluation for STPU. Concrete carbonation exposure test and freezing and thawing test for concrete coated with STPU have been performed. The experimental result showed that STPU has high resisting capacity and durability in all tests. Therefore, STPU would be used as seismic reinforcement materials.