• Journal of Electrical Engineering and Technology
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• 제4권3호
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• pp.330-336
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• 2009

This paper proposes an on-line voltage management and control solution for a distribution system which can improve the efficiency and accuracy of existing off-line work by collecting customer voltage on-line as well as the voltage compensation capability of the existing ULTC (Under Load Tap Changer) operation and control strategy by controlling the ULTC tap based on pattern clustering and recognition. The proposed solution consists of an ADVMD (Advanced Digital Voltage Management Device), a VMS (Voltage Management Solution) and an OLDUC (On-Line Digital ULTC Controller). An on-line voltage management emulator based on multi-thread programming and the shared memory method is developed to emulate on-line voltage management and digital ULTC control methodology based on the on-line collection of the customer's voltage. In addition, using this emulator, the effectiveness of the proposed pattern clustering and recognition based ULTC control strategy is proven for the worst voltage environments for three days.

• 한국지반공학회논문집
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• 제28권6호
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• pp.19-29
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• 2012

일반마이크로파일의 저항성능을 개선시키기 위해 최근에 토목섬유을 활용한 팩마이크로파일이 개발되었다. 팩마이크로파일은 일반마이크로파일의 강봉이나 강관을 토목섬유팩으로 감싸고 주입재와 주입압을 토목섬유팩 내부에 가하여 제작한다. 이 주입압에 의하여 천공 직경이 크게 확대된다. 동일한 한 지반 속에 설치된 세 개의 마이크로파일을 대상으로 일련의 말뚝인발시험을 실시하였다. 세 말뚝 중 두 개는 팩마이크로파일였고 나머지 하나는 강봉을 사용한 일반마이크로파일이였다. 토목섬유팩에 적용된 주입압에 의하여 팩마이크로파일의 경우 천공직경이 152mm에서 220mm으로 확대되었다. 마이크로파일의 주면에서 발달하는 단위주면마찰력은 말뚝두부의 인발변위량의 증가와 함께 서서히 증가하여 한계상태에 도달한 한계변위량에서 수렴치에 도달한다. 팩마이크로파일의 인발저항력은 일반마이크로파일의 인발저항력보다 크게 나타난다. 이와 같은 팩마이크로파일의 인발저항력을 증대시킬 수 있는 원인으로는 크게 두 가지를 생각할 수 있다; 첫째는 마이크로파일에 설치한 토목섬유팩내 주입압으로 마이크로파일의 단면적을 증대시키므로 말뚝주면의 마찰저항면적을 증대시킬 수 있기 때문이고, 둘째는 마이크로파일의 단면이 확대될 때 확대되는 부분의 체적만큼의 토사가 주변지반을 압축시켜 말뚝과 지반 사이의 마찰저항력을 증대시킬 수 있기 때문이다. 이 압축효과는 지표면 부근 보다 깊은 지층에서 크게 나타났다. 말뚝 주면에서 발휘되는 단위주면마찰력은 말뚝의 직경이 작은 경우가 더 크게 발휘된다. 즉 마이크로파일의 주면에서 발달되는 단위주면마찰력은 대구경 현장타설말뚝의 주면에서 발달되는 단위주면마찰력보다 크게 나타난다.

• 한국정보과학회논문지:시스템및이론
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• 제29권8호
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• pp.445-455
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• 2002

본 논문은 공유 메모리 시스템에서 계층적 태스크 그래프(Hierarchical Task Graph, HTG)의 복합 노드 태스크들을 효율적으로 수행하기 위한 새로운 태스크 스케쥴링 기법을 소개한다. 함수 병렬성 추출을 위해 제안된 기법은 별도의 전역 스케쥴러가 필요 없이 프로세서 스스로가 스케쥴링 기능을 행하는 자동 스케쥴링이다. 제안된 스케쥴링 기법을 단일처리기 시스템을 비롯한 여러 플랫폼에 적용하기 위해 자바 스레드를 이용하여 구현하였으며, 기존의 비트 벡터 방법과 성능을 비교 분석하였다. 실험 파라메터 값을 이용한 실험 결과, 제안된 스케쥴링 기법은 수행 시간 측면에서 효율적이며 양호한 부하 균형을 유지하였다. 또한, 제안된 기법은 기존의 방법에 비해 메모리 사용량을 줄일 수 있었다.

• 한국공간구조학회논문집
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• 제20권3호
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• pp.91-98
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• 2020

For form stability of membrane structures, membrane material is required to be in tension. Therefore, in planning and maintenance management, the engineer should consider enough about introduction of stress during construction and re-introduction of stress after completion. Clamping part is an important portion with the function for introducing tension into membrane materials, and the function to transmit stress to boundary structures, such as steel frames. Then, the purpose of this research is to clarify stress condition and stress transfer mechanism including clamping part of membrane structures, and to grasp the changing tendency of membrane structures with the passage of time. In this research, following previous one, we perform well-balanced evaluation by conducting tensile fractured tests of clamping part's specimens, and by measuring individually the amount of displacement of not only overall specimen's length but membrane material and clamping part. Thereby, we consider the influence the difference in the hardness of edge rope and the difference in the direction of thread affect modification and fracture load.

• Steel and Composite Structures
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• 제20권3호
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• pp.501-512
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• 2016

High-strength structural bolts have been utilized for beam-to-column connections in steel-framed structural buildings. Failure of these components may be caused by the bolt shank fracture or threads stripping-off, documented in the literature. Furthermore, these structural bolts are galvanized for corrosion resistance or quenched-and-tempered in the manufacturing process. This paper adopted the finite element simulation to demonstrate discrete mechanical performance for these bolts under tensile loading conditions, the coated and uncoated numerical model has been built up for two numerical integration methods: explicit and implicit. Experimental testing and numerical methods can fully approach the failure mechanism of these bolts and their ultimate load capacities. Comparison has also been conducted for two numerical integration methods, demonstrating that the explicit integration procedure is also suitable for solving quasi-static problems. Furthermore, by using precise bolt models in T-Stub, more accurately simulate the mechanical behavior of T-Stub, which will lay the foundation of the mechanical properties of steel bolted joints.

• 한국공간구조학회논문집
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• 제21권2호
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• pp.49-56
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• 2021

The damage to non-structural elements in buildings has been increasing due to earthquakes. In Korea, post-installed anchors produced overseas have been mainly used for seismic anchorage of non-structural components to structures. Recently, a new cast-in-place concrete insert anchor installed in concrete without drilling has been developed in Korea. In this paper, an experimental study was conducted to evaluate the tensile and shear strengths of the newly developed anchor under monotonic load. The failure modes of the tension specimens were divided into concrete breakout failure and steel failure, and all shear specimens showed steel failure. In both tension and shear, the maximum loads of specimens were greater than the nominal strengths predicted by the concrete design code (KDS 14 20 54). As a result, it is expected that the current code can also be used to calculate the strength of the developed cast-in anchor.

• 정보과학회 컴퓨팅의 실제 논문지
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• 제23권5호
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• pp.328-333
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• 2017

모바일 플랫폼에서 게임은 가장 전력을 많이 소모하여 배터리 사용시간을 단축시키는 응용 중 하나이다. 따라서 모바일 게임은 스마트폰의 배터리 사용시간을 늘리기 위한 중요한 전력관리 대상이다. 그러나 모바일 게임 실행 중에 배터리 용량이 급격히 감소하는 현상은 빈번하게 발생하는 문제이며 사용자가 많은 여러 모바일 게임의 동작을 검토해 본 결과 멀티 쓰레드로 동작하는 동안 특정 쓰레드가 불필요하게 CPU 사용량을 높게 점유하여 에너지가 낭비되는 경우가 발생하였다. 따라서 본 논문은 게임 실행 중 Quality of Service(QoS)와 무관하게 비정상적으로 CPU 사용량이 높은 쓰레드를 검출하고 이종 멀티프로세싱 (Heterogeneous Multi-Processing)의 특성을 활용하여 QoS 저하 없이 전력소모를 감소시키는 최적화 기법을 제안한다. 제안된 기법을 상용 스마트폰(삼성 Galaxy S6 Edge)에 적용하여 QoS 저하 없이 최대 58%의 에너지 효율 향상이 가능하였다.

• Journal of Periodontal and Implant Science
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• 제37권4호
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• pp.681-690
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• 2007

Mini implants had been used provisionally for the healing period of implants in the beginning. But it becomes used for the on-going purpose, because it is simple to use, economic and especially suitable for the overdenture. But there is few studies about the stability of mini implants, that is most important factor for the on-going purpose, and particularly the implant parameters affecting the initial stability. The purpose of this study was to evaluate the stress and the strain distribution pattern of immediate-loaded screw type orthodontic mini-implant and the parameters affecting the initial stability of immediate-loaded mini-implant. Two dimensional finite element models were made and contact non-linear finite element analysis was performed. The magnitude and distribution of Von Mises stresses were evaluated. The obtained results were as follows: 1. The stress was concentrated on the thread tip of an implant in the cortical bone. 2. The direction of load is the most important factor for the stress distribution in cortical bone. 3. The diameter of an implant is the most important factor for the stress distribution in the trabecular bone. In conclusion, if the horizontal load vector is successfully controlled, mini-implants, which diameter is under 3mm, can be used for the on-going purpose.

• Tribology and Lubricants
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• 제35권1호
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• pp.65-70
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• 2019

Self-loosening of bolts owing to external forces occurs in several machines that are clamped by bolts and nuts. This study focuses on the self-loosening of the aiming bolt of the head lamp in a vehicle. It is important to prevent the aiming bolt from self-loosening as it has a decisive effect on the angle of the head lamp. A nut clamped with a bolt, known as a retainer, is made of plastic and has a partial screw thread. In addition, a transverse load has a considerable impact on the self-loosening of a bolt. We concentrate on the self-loosening of a bolt by a transverse load. The aim of this study is to define the limits of the external force that loosen the bolt. Based on the above conditions, we derive a theoretical equation and develop a numerical analysis program that can calculate the limiting forces for self-loosening. To verify the developed program, we design a test device that can measure the self-loosening by applying sliding forces to the aiming bolt. Using this method, we can draw the following conclusions. First, the developed testing device is suitable to prove the theory for calculating the self-loosening force. Second, the equation confirms the relationship of bolt self-loosening between resistance torque and shear force. Finally, the equation obtains the minimum value of the resistance torque required to decrease the change in the angle of the head lamp, thereby improving the possibility of increasing the stability of the head lamp.

• Steel and Composite Structures
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• 제31권1호
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• pp.1-12
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• 2019

Steel-concrete composite walls have been proposed and developed for applications in various types of structures. The double-skin profiled composite walls, as a natural development of composite flooring, provide structural and architectural merits. However, adequate intermediate fasteners between profiled steel plates and concrete core are required to fully mobilize the composite action and to improve the structural behavior of the wall. In this research, two new types of fasteners (i.e., threaded rods and vertical plates) were proposed and three specimens with different fastener types or fastener arrangements were tested under axial compression. The experimental results were evaluated in terms of failure modes, axial load versus axial displacement response, strength index, ductility index, and load-strain relationship. It was found that specimen with symmetrically arranged thread rods sustained more stable axial strain than that with staggered arranged threaded rods. Meanwhile, vertical plates are more suitable for practical use since they provide stronger confinement to profiled steel plate and effectively prevent the steel plate from early local buckling, which eventually enhance the composite action and increase the axial compressive capacity of the wall. The calculation methods were then proposed and good agreement was observed between the test results and the predicted results.