• Smart Structures and Systems
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• 제5권2호
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• pp.119-137
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• 2009

Smart sensors densely distributed over structures can use their computational and wireless communication capabilities to provide rich information for structural health monitoring (SHM). Though smart sensor technology has seen substantial advances during recent years, implementation of smart sensors on full-scale structures has been limited. Hardware resources available on smart sensors restrict data acquisition capabilities; intrinsic to these wireless systems are packet loss, data synchronization errors, and relatively slow communication speeds. This paper addresses these issues under the hardware limitation by developing corresponding middleware services. The reliable communication service requires only a few acknowledgement packets to compensate for packet loss. The synchronized sensing service employs a resampling approach leaving the need for strict control of sensing timing. The data aggregation service makes use of application specific knowledge and distributed computing to suppress data transfer requirements. These middleware services are implemented on the Imote2 smart sensor platform, and their efficacy demonstrated experimentally.

• 대한전자공학회논문지SD
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• 제43권7호
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• pp.20-28
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• 2006

본 논문에서는 불규칙하고 복잡한 다층(multi-layer) RLC 배선에 대하여 TWA(Traveling-wave-based Waveform Approximation)을 기반으로 한 새로운 시그널 인테그러티 검증에 대한 방법을 제시한다. 실제 레이아웃 구조의 불규칙한 배선을 가상 직선 배선으로 변환하고 이를 TWA 기법을 사용하여 효율적으로 검증하였다. 여기서 제안된 방법은 3차원 구조에 대한 회로 모델을 사용한 일반적인 SPICE 시뮬레이션에 비하여 계산시간을 현저하게 단축시킬 수 있으며, 타이밍의 경우 5% 이내에서, 크로스톡의 경우 10% 이내에서 정확하다는 것을 보인다.

• Structural Engineering and Mechanics
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• 제52권6호
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• pp.1193-1208
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• 2014

A simulation of failures on responsible elements is only one form of the extreme structural behavior analysis. By understanding the dynamic behavior in incidental situations, it is possible to make a special structural design from the point of the largest axial force, stress and redundancy. The numerical realization of one such simulation analysis was performed using FEM in this paper. The boundary parameters of transient analysis, such as overall structural damping coefficient, load accelerations, time of load fall and internal forces in the responsible structural elements, were determined on the basis of the dynamic experimental parameters. The structure eigenfrequencies were determined in modal analysis. In the study, the basic incidental models were set. The models were identified by many years of monitoring incidental situations and the most frequent human errors in work with heavy structures. The combined load models of structure are defined in the paper since the incidents simply arise as consequences of cumulative errors and failures. A feature of a combined model is that the single incident causes the next incident (consecutive timing) as well as that other simple dynamic actions are simultaneous. The structure was observed in three typical load positions taken from the crane passport (range-load). The obtained dynamic responses indicate the degree of structural sensitivity depending on the character of incident. The dynamic coefficient KD was adopted as a parameter for the evaluation of structural sensitivity.

• Journal of Astronomy and Space Sciences
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• 제18권3호
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• pp.191-208
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• 2001

We have recently compiled a database of the properties of 192 impact craters, which supercedes previous compilations. Using our database, the impact structures found in North America, Europe and Australia have been examined; these cratonic areas have been relatively stable for considerably long geological periods, and thus have been best preserved. It is confirmed that there is a close correlation between the geological epoch boundaries, the epochs of mass extinctions, antral the "timing" of impacts. In addition, the terrestrial cumulative flux of objects >20km is found to be $1.77{\times}10^{-15}km^{-2}yr^{-1}$, over the last 120 Myr, which is much smaller than the published values in McEwen et al. (1997) and Shoemaker (1998) ($5.6{\pm}2.8{\times}10^{-15}km^{-2}yr^{-1}$. For terrestrial impact structures with D> 50 km, the apparent cumulative flux over the last 2450 Myr is ~50 times smaller than the corresponding value for the Moon. If we assume that the Earth and the Moon suffered the same level of bombardment over this time, this would mean that the actual flux of impacting bodies, capable of making craters with D)50 km, was ~ 50 times larger than the apparent flux estimated from the currently known terrestrial records.

• 한국지능정보시스템학회:학술대회논문집
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• 한국지능정보시스템학회 2002년도 춘계학술대회 논문집
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• pp.429-434
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• 2002

For companies assembling end products from sub assemblies or components, MRP (Material Requirement Planning) logic is frequently used to synchronize and pace the production activities for the required parts. However, in MRP, the planning of operational-level activities is left to short term scheduling. So, we need a good scheduling algorithm to generate feasible schedules taking into account shop floor characteristics and multi-level job structures used in MRP. In this paper, we present a GA (Genetic Algorithm) solution for this complex scheduling problem based on a new gene to reflect the machine assignment, operation sequences and the levels of the operations relative to final operation. The relative operation level is the control parameter that paces the completion timing of the components belonging to the same branch in the multi-level job hierarchy. In order to revise the fixed relative level which solutions are confined to, we apply large step transition in the first step and GA in the second step. We compare the genetic algorithm and 2-phase optimization with several dispatching rules in terms of tardiness for about forty modified standard job-shop problem instances.

• 암석학회지
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• 제19권1호
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• pp.19-30
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• 2010

옥천대의 중앙부에 위치하는 옥천지역에는 쥬라기 대보 옥천화강암이 분포한다. 본 논문은 옥천화강암에 발달하는 변형구조에 대한 구조암석학적 연구결과를 바탕으로 호남전단대의 운동시기를 새롭게 고찰해 보았다. 옥천화강암의 구조적 형태는 지질도상에서 동서 방향의 쐐기형 꼬리와 동북동 방향으로 약간 신장된 타원형 분포를 하고 있고, 주변암인 옥천누층군의 광역엽리 S1은 옥천화강암의 접촉부와 평행하게 발달한다. 이는 옥천화강암이 광역엽리 S1이 형성된 이후에 수동적으로 관입하였음을 지시한다. 옥천화강암의 주요 변형구조는 그 접촉부를 관통하는 고결후 형성된 남북 방향의 구조적 엽리와 동서 방향의 반화강암질 암맥 그 리고 그 동부 경계부에 북서 및 동서 방향의 좌수향 전단대 등이 있다. 남북 방향의 구조적 엽리와 동서 방향의 반화강암질 암맥은 옥천화강암이 관입후 냉각되는 약 $500{\sim}450^{\circ}C$ 부근의 변형온도에서 (북)북동 방향의 우수 주향-이동성 호남전단운동에 의해 형성되었으며, 북서 및 동서 방향의 좌수향 전단대는 옥천화강암의 원래의 관입위치에서 우수향 회전운동 동안에 옥천화강암과 주변암 사이에서 발생된 전단변형에 의해 형성되었다. 호남전단대의 활동시기 및 중생대 화성활동에 대한 기존 연구결과를 종합하여 옥천화강암의 관입 및 변 형작용사와 호남전단대의 운동시기를 고찰해 보면 다음과 같다. (1) 전기~중기 쥬라기 (187~170 Ma); 전기 호남전단운동과 관련된 동구조 엽리상 화강암의 관입. (2) 중기 쥬라기 (175~166 Ma); 쥬라기 화강암류의 주 관입기, 옥천화강암의 수동적 관입, (3) 중기~후기 쥬라기 (168~152 Ma); 쥬라기 화강암류의 주 냉각기, 후기 호남전단운동과 관련된 옥천화강암의 변형작용. 따라서 본 연구결과는 호남전단운동은 175~166 Ma 동안의 휴식기를 걸쳐 187~152 Ma 약 35 Ma 동안 적어도 2회 발생하였음을 제안한다.

• Architectural research
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• 제7권2호
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• pp.81-89
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• 2005

Over the years, existing bridges have had various degrees of maintenance to extend the service life. As the existing bridges continue to deteriorate, however, each Department of Transportation (DOT) of the United States of America faces increasing demands on the limited funds available for bridge maintenance. Therefore, it is very important for State Department of Transportations to establish Maintenance, Repair, and Rehabilitation (MR&R) strategies for bridge structures such that funds get allocated for appropriate maintenance over the service life. This paper identifies the state-of-art and the state-of-practice of MR&R actions and the use of MR&R strategies in concrete bridge decks. In addition, a questionnaire survey was conducted to identify the type and timing for MR&R actions as well as existing MR&R strategies taken in concrete bridge deck by each DOT. This paper also presents the results of the survey.

• 대한전자공학회논문지
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• 제27권8호
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• pp.1201-1210
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• 1990

This paper proposes on-chip instruction and data cache memories on RISC reduced instruction set computer) architecture which supports fast instruction fetch and data read/write, and enables RISC processor under research to obtain high performance. In the execution of HLL(high level language) programs, heavily used local scalar variables are stored in large register file, but arrays, structures, and global scalar variables are difficult for compiler to allocate registers. These problems can be solved by on-chip Instruction/Data cache. And each cycle of instruction fetch, pad delay causes the lowering of the processors's performance. Cache memories are designed in CMOS technology and SRAM(static-RAM), that saves layout area and power dissipation, is used for instruction and data storage. To speed up and support RISC processor's piplined architecture efficiently, hardwired logic technology is used overall circuits i cache blocks. The schematic capture and timing simulation of proposed cache memorises are performed on Apollo DN4000 workstation using Mentor Graphics CAD tools.

• 대기
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• 제20권3호
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• pp.367-377
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• 2010

Variation of tracer distribution during the vortex-breakup period in the Antarctic region was observed by the data from the Improved Limb Atmospheric Spectrometer (ILAS) and ILAS-II. All four trace species including methane, nitrous oxide, ozone, and water vapor show similar patterns of vertical gradient in spite of different structures of zonal mean mixing ratio. Timings of vortex breakup on each level are estimated by two different methods, and they are compared with zonal standard deviations following the latitude circle of each trace species. Although the tracers have different chemical life times and sink/source, the zonal standard deviation patterns show remarkable similarities. The zonal standard deviation shown here to measure the zonal asymmetry of tracer distribution is believed to diagnose the timing of the Antarctic polar-vortex breakup reasonably well.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2006년도 추계학술대회 논문집
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• pp.55-58
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• 2006

The flow characteristics in a confined slot jet impinging on a flat plate were investigated by using cinematic Particle Image Velocimetry technique. The three different kinds of confined slot were applied to the jet with a view to evaluating the shape effect and the jet Reynolds number was varied from 250 to 1000 for a fixed jet-to-plate spacing of H/W=5. It was found that the vortex structures in the shear layer are developed with increase of Reynolds number and that the jet becomes unsteady by the interaction of vortex pairs between 500 and 750 of Reynolds number. Finally, the slot shape was proved to be related with the generation timing of vortex pair and the temporal vortex structure.