• 한국측량학회지
• /
• 제25권4호
• /
• pp.337-345
• /
• 2007

국토지리정보원은 1995년 수원 관측소 설치를 시작으로 현재 14개소의 GPS 상시관측소를 운영하고 있다. 이 연구에서는 14개 관측소를 모두 방문하고 IGS와 NGS의 사이트 가이드라인에 적합한 안테나와 지지대를 유지하고 있는지, 그리고 관측소 주변 환경으로 인해 측위오차가 발생할 가능성이 있는지를 조사하였다. 또한 현장조사 결과를 TEQC 프로그램을 이용한 GPS 데이터 품질평가 결과와 비교하였다. 현장조사 결과 태백, 제주, 광주, 그리고 원주 관측소의 관측환경은 충분한 시야각이 확보되지 않고 다중경로 오차 유발 요인이 다수 존재하는 등의 문제점이 있음을 파악하였고, 이는 TEQC 품질평가를 통해서도 입증되었다. 그리고 2005-2006년 사이에 진행된 GPS 수신기 교체에 의해 국토지리정보원 GPS 상시관측소의 다중경로 오차와 사이클슬립 개수가 감소되었음을 발견하였다.

• 한국정보과학회논문지:소프트웨어및응용
• /
• 제30권11호
• /
• pp.1044-1053
• /
• 2003

본 논문에서는 과학 교육 분야에서 기존의 교육방식이 갖고 있는 한계성을 극복하고 교육 및 학습 효과를 향상시키기 위한 방안으로 역감 제시 장치를 이용한 가상 현실 시스템을 제안한다. 제안된 시스템의 효용성과 응용가능성, 활용방법을 효과적으로 나타낼 수 있는 4가지 과학세계로 구성된 가상 과학 체험 공간을 구축하여 미시 세계에서는 원자간의 현상을, 마찰 세계에서는 스틱-슬립 마찰현상을, 기전 세계에서는 모터 및 발전기의 원리를, 거시 세계에서는 코리올리스 가속도로 인한 물리적 현상을 각 세계에서 역학적으로 모델링하고 역감 제시 장치와 인터페이스를 위한 에뮬레이션 기법을 고안한다. 그리고, 역감 제시 장치, HMD(Head Mounted Displays), 가상환경(스테레오 그래픽스와 GUI)을 포함한 디지털 제어기로 구성된 가상 과학 체험 시스템을 구축한다. 끝으로 본 연구를 통해 교육의 보조 매체와 학습의 도구로서 효율성을 극대화시키기 위한 가상 과학 체험 공간의 설계 및 구현에 관한 고려사항을 제시한다.

• 지질공학
• /
• 제31권3호
• /
• pp.269-281
• /
• 2021

Land creeping is the imperceptibly slow, steady, downward movement o f slope-forming soil or rock. Because creep-related failures occur frequently on a large scale without notice, they can be hazardous to both property and human life. Korea Forest Service has operated the prevention and response system from land creeping which has been on the rise since 2018. We categorized and proposed three survey steps (e.g., preliminary, regional, detailed) for investigation of creeping susceptibility site with a focus on geophysical mapping of a selected test site, Yongheung-dong, Pohang, Korea. The combination of geophysical (dipole-dipole electrical resistivity tomography and reciprocal seismic refraction technique, well-logging), geotechnical studies (standard penetrating test, laboratory tests), field mapping (tension cracks, uplift, fault), and comprehensive interpretation of their results provided the reliable information of the subsurface structures including the failure surface. To further investigate the subsurface structure including the sliding zone, we performed high-resolution geophysical mapping in addition to the regional survey. High-resolution seismic velocity structures are employed for stability analysis because they provided more simplified layers of weathering rock, soft rock, and hard rock. Curved slip plane of the land creeping is effectively delineated with a shape of downslope sliding and upward pushing at the apex of high resistive bedrock in high-resolution electrical resistivity model with clay-mineral contents taken into account. Proposed survey steps and comprehensive interpretation schemes of the results from geological, geophysical, and geotechnical data should be effective for data sets collected in a similar environment to land-creeping susceptibility area.

• Nuclear Engineering and Technology
• /
• 제51권3호
• /
• pp.709-718
• /
• 2019

The international nuclear industry has undergone a lot of changes since the Fukushima, Chernobyl and TMI nuclear power plant accidents. However, there are still large and small component deficiencies at nuclear power plants in the world. There are many causes of electrical equipment defects. There are also factors that cause component failures due to human errors. This paper analyzed the root causes of failure and types of human error in 300 cases of electrical component failures. We analyzed the operating experience of electrical components by methods of root causes in K-HPES (Korean-version of Human Performance Enhancement System) and by methods of human error types in HuRAM+ (Human error-Related event root cause Analysis Method Plus). As a result of analysis, the most electrical component failures appeared as circuit breakers and emergency generators. The major causes of failure showed deterioration and contact failure of electrical components by human error of operations management. The causes of direct failure were due to aged components. Types of human error affecting the causes of electrical equipment failure are as follows. The human error type group I showed that errors of commission (EOC) were 97%, the human error type group II showed that slip/lapse errors were 74%, and the human error type group III showed that latent errors were 95%. This paper is meaningful in that we have approached the causes of electrical equipment failures from a comprehensive human error perspective and found a countermeasure against the root cause. This study will help human performance enhancement in nuclear power plants. However, this paper has done a lot of research on improving human performance in the maintenance field rather than in the design and construction stages. In the future, continuous research on types of human error and prevention measures in the design and construction sector will be required.

• Computers and Concrete
• /
• 제24권2호
• /
• pp.103-115
• /
• 2019

In this study, the strength and stiffness (EI) of wood-concrete composite beams for bridges with T-shaped cross section were evaluated. Two types of connectors were used: connectors bonded with epoxy adhesive and connectors attached to the wood just by pre-drilling (without adhesive). The connectors consisted of common steel bars with a diameter of 12.5 mm. Initially, the strength and stiffness (EI) of the beams were analyzed by bending tests with the load applied at the third point of the beam. Subsequently, the composite beams were evaluated by numerical simulation using ANSYS software with focus on the connection system. To make the composite beams, Eucalyptus citriodora wood and medium strength concrete were used. The slip modulus K and the ultimate strength values of each type of connector were obtained by direct shear tests performed on composite specimens. The results showed that the connector glued with epoxy adhesive resulted in better strength and stiffness (EI) for the composite beams when compared to the connector fixed by pre-drilling. The differences observed were up to 10%. The strength and stiffness (EI) values obtained analytically by $M{\ddot{o}}hler^{\prime}$ model were lower than the values obtained experimentally from the bending tests, and the differences were up to 25%. The numerical simulations allowed, with reasonable approximation, the evaluation of stress distributions in the composite beams tested experimentally.

• 자원환경지질
• /
• 제54권6호
• /
• pp.629-647
• /
• 2021

Located in the eastern part of the Anti-Atlas, the Tafilalet region shows numerous dykes and sills that crosscut the Paleozoic terrains. The magmatic structures (dykes and sills) of the Tadaout-Tizi n'Rsas (TTR) anticline is studied here, it located neighboring the main branch of the Anti-Atlas Major Fault (AAMF), known in this location as the Oumejrane-Taouz Fault (OJTF). The N20° to N60° trending dykes crosscut the Paleozoic formations (Ordovician to Devonian), whereas sills are injected into the Silurian and Devonian ones. The dyke swarms of TTR have been studied using the Anisotropy of Magnetic Susceptibility (AMS), petrographic study and structural analyses. The petrographic study of the TTR doleritic dykes shows a dominance of plagioclase feldspars, alkali feldspars, amphiboles, pyroxenes and biotite. The dykes contain also mesotype (natrolite), sphene (titanite), apatite, actinolite and pegmatitic enclaves of biotite, orthoclase feldspars and pelites. Concerning field works, they show the deformation of TTR dykes by the Variscan tectonics events, it is marked by the presence of displacements (strike-slip faults) and cleavages. The Magnetic Susceptibility (MS) measured on magmatic specimens show the dominance of ferromagnetic and paramagnetic minerals. The high values of MS in the dykes are due to the presence of hematite, amphibole, pyroxene and biotite. In addition their magnetic fabric, determined by our AMS study, allows us to reconstitute the tectonic event which affected the magmatic bodies. This one is characterized by a magnetic foliation and a NNW-trending lineation that reflect the Variscan shortening orientation.

• 터널과지하공간
• /
• 제32권3호
• /
• pp.203-218
• /
• 2022

본 연구에서는 유체 주입 중단과 유발 지진 규모의 관계에 대하여 수리역학적으로 분석하였다. 수리적 해석을 통해 공극압의 구배가 유체 주입 중단으로 인해 완만해짐과 동시에 주입 중단 이후에도 수 시간 동안 압력 선두에서 상당한 임계 공극압에 도달하면서 더 넓은 영역에서 추가적인 전단을 일으킬 수 있음을 확인하였다. 수리역학 복합 해석을 단순화된 균열모델에 적용함으로써 유체 주입 중단 후에 최대 규모의 지진이 발생하는 것을 모사하였고, 유체 주입을 유지하는 경우와의 비교를 통해 급작스런 유체 주입 중단이 지진 유발에 미치는 영향을 분석하였다. 또한 공극압의 분포 이외에도 단층 간의 기하학적 관계와 응력 재분배 등에 의해 임계 공극압의 구배가 변하며 이것이 유발 지진의 규모 평가에 중요하게 고려되어야 함을 확인하였다.

• Geomechanics and Engineering
• /
• 제28권4호
• /
• pp.335-346
• /
• 2022

Buckling failure is a typical slope instability mode that should be paid more attention to. It is difficult to provide systematic guidance for the monitoring and management of such slopes due to unclear mechanism. Here we examine buckling failure as the potential instability mode for a slope above a railway tunnel in southwest China. A comprehensive model test system was developed that can be used to conduct buckling failure experiments. The displacement, stress, and strain of the slope were monitored to document the evolution of buckling failure during the experiment. Monitoring data reveal the deformation and stress characteristics of the slope with different slipping mass thicknesses and under different top loads. The test results show that the slipping mass is the main subject of the top load and is the key object of monitoring. Displacement and stress precede buckling failure, so maybe useful predictors of impending failure. However, the response of the stress variation is earlier than displacement variation during the failure process. It is also necessary to monitor the bedrock near the slip face because its stress evolution plays an important role in the early prediction of instability. The position near the slope foot is most prone to buckling failure, so it should be closely monitored.

• 한국분무공학회지
• /
• 제27권3호
• /
• pp.117-125
• /
• 2022

This study examines whether engine fuel efficiency is improved by optimization of the exhaust valve timing in a state where the intake valve timing has been optimized in a small turbo gasoline engine that has intake cams and exhaust cams with fixed valve opening periods. When the exhaust valve is opened late, the expansion stroke is longer, and the efficiency can be improved. A 2-cylinder turbo gasoline engine with 0.8 liters of displacement and an MPI (Multi Point Injection) fuel system was used. The engine was operated at 1,500 and 3,000 rpm, and the load conditions included a partial load of 50 N·m and a high load of 70 N·m. Data was recorded as the exhaust valve timing was controlled, and this was used to calculate the efficiency of combustion using a heat release, the fuel conversion efficiency, and the pumping loss. Results and the hydrocarbon concentrations in the exhaust gas were compared for each condition. Experiment results confirmed that additional fuel efficiency improvements are possible through exhaust valve timing control at 1,500 rpm and 50 N·m. However, in other operating conditions, fuel efficiency improvements could not be obtained through exhaust valve timing control because cases where the pumping loss and fuel/air mixture slip increased when the exhaust valve timing changed and the fuel efficiency declined.

• Steel and Composite Structures
• /
• 제46권4호
• /
• pp.497-512
• /
• 2023

Using light weight concrete as infill material in conventional cold-formed steel (CFS) shear wall systems can considerably increase their load bearing capacity, ductility, integrity and fire resistance. The compressive strength of the filler concrete is a key factor affecting the structural behaviour of the composite wall systems, and therefore, achieving maximum compressive strength in lightweight concrete while maintaining its lightweight properties is of significant importance. In this study a new type of optimum polystyrene lightweight concrete (OPLC) with high compressive strength is developed for infill material in composite CFS shear wall systems. To study the seismic behaviour of the OPLC-filled CFS shear wall systems, two full scale wall specimens are tested under cyclic loading condition. The effects of OPLC on load-bearing capacity, failure mode, ductility, energy dissipation capacity, and stiffness degradation of the walls are investigated. It is shown that the use of OPLC as infill in CFS shear walls can considerably improve their seismic performance by: (i) preventing the premature buckling of the stud members, and (ii) changing the dominant failure mode from brittle to ductile thanks to the bond-slip behaviour between OPLC and CFS studs. It is also shown that the design equations proposed by EC8 and ACI 318-14 standards overestimate the shear force capacity of OPLC-filled CFS shear wall systems by up to 80%. This shows it is necessary to propose methods with higher efficiency to predict the capacity of these systems for practical applications.