• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.2
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• pp.45-55
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• 1998

Although a number of methods have been proposed to predict the liquefaction potential, few methods have been developed by using the characteristic of material's microstructure. In this research, fundamental procedure is proposed for the assessment of liquefaction potential in saturated soils based on the Disturbed Sate Concept(DSC) model which can provide a unified constitutive model for the characterization of entire stress-strain behavior under cyclic loading. From this concept, the value of disturbance at threshold state (Critical Disturbance, $D_C$) in the deforming microstructure provides the basis for initial liquefaction. This method is verified with respect to data from Cyclic Truly Triaxial test for saturated Ottawa sand. Also, the relationship between liquefaction and initial confinig stress is defined using definition of $D_C$. It is believed that the new procedure for identifying liquefaction based on the DSC model can capture the behavior of liquefation, and as a result, it is shown to be on improvement over the available empirical procedures.

• Journal of the Korean Geotechnical Society
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• v.27 no.7
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• pp.69-79
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• 2011

Laboratory tests are generally used to determine the input parameters for the selected constitutive models controlling various stress and drainage conditions, but have disadvantages in that the tests are performed on the samples obtained from the bore hole which are prone to be disturbed by various factors such as the tube penetrations, sample preparations and storage. To overcome these disadvantages, it is necessary to understand the effect of disturbance on the stiffness of the sample, especially the normally consolidated clays which are generally considered as soft clays. Therefore, in this study triaxial tests are performed on the normally consolidated kaolinite to evaluate the sample disturbance effects on the stiffness and to determine the field representative input parameters. The stress path results show that the shear and coupling modulus degradation patterns with strain are affected seriously by the disturbance. However, the strengths of the normally consolidated kaolinite are little influenced by the disturbance.

• 한국공간정보시스템학회:학술대회논문집
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• 2007.06a
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• pp.268-272
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• 2007

현재 시행되고 있는 하천정비와 하도정비는 하천 흐름의 특성을 간과한 채 일괄적으로 진행되어 왔으며 그 결과로 하천의 인공화는 지금까지 계속되고 있다. 이에 따라 하천 및 하도의 물리, 화학, 생물에 미치는 영향은 심각하며, 그 동안 인위적인 하천교란의 요인과 하천교란에 따른 영향, 즉 하상변동, 외래종 식생 침입, 생태서식처 변화 등의 정량적 평가 기술의 수립은 매우 미흡한 상태이다. 뿐만 아니라 하천 교란 극복을 위한 저감기술, 복원기술 및 적응관리 기술 또한 체계적으로 정리되지 못하여 하천과 댐 관리당국이 어려움을 겪고 있다. 이러한 상황을 극복하기 위해서는 하천 교란에 대항하는 회복관리 기술 개발을 위한 교란 평가 기술이 필요하다. 따라서 본 연구에서는 항공사진 및 GIS기법을 이용하여 국내 주요하천의 원인별 교란실태를 조사하고 분석함으로써 하천교란 조사기술 개발에 응용할 수 있는 방안을 제시하고자 하였다. 분석을 위하여 댐 하류의 하천교란 및 적응현장 시범지역을 선정한 후 대상 지역의 항공사진을 GIS화하여 하천 교란 실태를 분석하는 데에 필요한 자료를 생성하였으며 생성된 자료를 바탕으로 하천의 평면 및 단면의 변화특성을 조사할 수 있었다. 또한 경년별 저수로 형태와 하천 중심선 비교 분석을 통하여 저수로의 이동 및 변화 양상을 규명해 낼 수 있었으며 그 결과 댐 하류지역에서 하도안정문제가 발생하였음을 확인할 수 있었다. 본 연구 결과를 바탕으로 보다 효율적인 하도안정문제에 관한 대책수립이 가능하리라 보며, 이를 위해서는 하천 교란 조사기술 개발에 대한 연구가 뒤따라야 할 것이다.과적임을 알 수 있었다. 실험 결과 본 기법으로 유휴시간에 프로세서를 저전력모드로 바꾸는 기존의 고전적인 전력 관리 기법보다 전체 시스템 전력 소모를 9% 더 절약할 수 있었다. 위성영상과 DEM 개발기술이 87% 이상의 점수를 받아 가장 시장성 및 활용성이 높은 기술로 평가되었으며, 초다분광영상에 대한 기술은 70%를 겨우 넘는 수준에서 평가가 되었다. 멀티센서 공간영상정보 통합처리 기술 개발은 다목적 실용위성의 보유, 국가 NGIS 사업의 결과물이 상당히 축척이 되어 있고, 라이다(LiDAR) 기술의 도입을 위한 환경이 조성되었기에 다른 국가에 비해 멀티센서 기술의 적용과 산업화가 가시화 될 수 있을 것으로 기대된다. 그러나 멀티센서 자료의 수급이 용이하지 못하고, 법 제도적인 한계, 시장의 성숙도가 기대이하라는 점 등의 한계를 노정하고 있다.a var. sieboldii 3. Pinus densiflora, Q. aliena, Q. acutissima, P. thunbergii, Q. acuta 4. Carpinus laxiflora, Camellia japonicas. C. tschonoskii community의 5개 그룹으로 나타났다. 하류의 부착돌말류는 상대적으로 양호한 수질을 가지고 있는 정점 1에서 다양한 생물상을, 탄천의 영향을 받는 정점 2는 상대적으로 수질이 악화되어 호오염성 종들이 높은 분포를 나타내고 있었다. 또한 부착돌말류 중 Cymbella minuta는 다른 부착돌말류에 비해 강한 오염지표성을 나타내고 있었다.p=0.000, $4.76{\pm}3.31$

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.9
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• pp.859-866
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• 2010

Nonlinear dynamics of pulsating instability-diffusional-thermal instability with Lewis numbers sufficiently higher than unity-in counterflow diffusion flames, is numerically investigated by imposing a Damkohler number perturbation. The flame evolution exhibits three types of nonlinear behaviors, namely, decaying pulsating behavior, diverging behavior (which leads to extinction), and stable limit-cycle behavior. The stable limit-cycle behavior is observed in counterflow diffusion flames, but not in diffusion flames with a stagnant mixing layer. The critical value of the perturbed Damkohler number, which indicates the region where the three different flame behaviors can be observed, is obtained. A stable simple limit cycle, in which two supercritical Hopf bifurcations exist, is found in a narrow range of Damkohler numbers. As the flame temperature is increased, the stable simple limit cycle disappears and an unstable limit cycle corresponding to subcritical Hopf bifurcation appears. The period-doubling bifurcation is found to occur in a certain range of Damkohler numbers and temperatures, which leads to extend the lower boundary of supercritical Hopf bifurcation.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.255-258
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• 2005

광케이블의 분기나 이전 공사 시 광케이블을 적확히 식별할 필요성이 있다. 현재의 광케이블 식별 방법은 인력당김에 의한 원시적인 방법이나 전자기 유도를 이용하는 방법 등이 사용되고 있으나 인력과 시간이 많이 소모되고 식별 가능한 거리에도 한계가 있다. 본 논문에서 제시하는 광케이블 식별 방법은 맨홀 등에서의 현장 작업자가 식별코자 하는 광케이블을 두드리는 등의 교란을 가하고, 이러한 교란을 광섬유 간섭계를 통하여 추출하여 다시 현장의 작업자에게 통신 수단을 통하여 전송하여 줌으로써 작업자가 직접 자신이 가한 교란 신호와 추출된 신호간의 일치 여부를 판단함으로써 광케이블을 식별할 수 있도록 하는 것이다. 이 방법에 따르면, 원격지의 현장에서도 수월하게 광케이블을 대조할 수 있어서 광케이블 절단 작업 시 오절단을 사전에 예방할 수 있다.

• Ecology and Resilient Infrastructure
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• v.10 no.4
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• pp.143-160
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• 2023

This study applied the stream physical habitat assessment system to obtain basic information for river restoration and watershed management in high-gradient and mid-gradient streams in the Naeseongcheon basin. The total length of high-gradient and mid-gradient streams in the Naeseongcheon basin is about 273 km, and as a result of the assessment, it was analyzed that suboptimal reach was about 8.2 km, normal reach was 180.3 km, and marginal reach was 84.7 km. In addition, the physical habitat quality of high-gradient streams was analyzed to be normal condition with an average of 106 points (53%), and in particular, the score of channel/hydraulic category, which is the most important for the habitat of aquatic animals, was analyzed to be normal, close to the limit, with an average of 54 points (45%). The physical habitat quality of mid-gradient streams was found to be in normal condition with an average of 90 points (45%), and the score of channel/hydraulic category was in marginal condition with an average of 39 points (32%). Overall, among 165 reaches of high-gradient and mid-gradient streams in the Naeseongcheon basin, 4 reaches (3%) were evaluated as suboptimal, 119 reaches (72%) were normal, and 42 reaches (25%) were considered marginal. These results showed that the physical habitat of Naeseongcheon was significantly disturbed. Disturbance of stream physical habitat in the Naeseongcheon basin occured due to farmland around stream, urbanization, reservoir construction, and river maintenance.

• Korean Journal of Plant Resources
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• v.21 no.1
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• pp.66-72
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• 2008

RAPD analyses were performed from twenty-four populations of Persicaria thunbergii(Sieb. & Zucc.) H. Gross ex Nakai. The length of amplified DNA fragments ranged from 200 to 1,900bp. 184 scorable RAPD markers were found from PCR reactions with sixteen random oligoprimers. Based on the results, populations of Persicaria thunbergii were classified into disturbance streams of urban and rural streams as well as natural streams. And the populations from natural streams showed having higher genetic similarites than those from highly disturbed streams, Also, the heterogenetic differences between the populations from natural and disturbed areas could be represented the results of the stream environmental changes.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.188-196
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• 2004

To optimize and limit the axial length of baffle in KSR-III engine, stability rating tests using pulse gun as one of artificial disturbance devices have been done. Decay time and other parameters for the evaluation of stabilization ability of engine to external perturbation have been analyzed to quantify stabilization capacity of engine, in other words, dynamic stability margin. If baffle does not cover flame zone enough which can be considered as collision region of injector, it wasn't be able to suppress external perturbation sufficiently. The limit of combustion stability margin of engine is assumed to be 50 mm length baffle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.281-287
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• 2005

Nonlinear behaviors such as steep-fronted wave motions and a finite amplitude limit cycle often accompanying combustion instabilities have been numerically investigated using a characteristic-based approximate Riemann solver and the well-known ${\eta}-{\tau}$ model. A resonant pipe initially subjected to a harmonic pressure disturbance described the natural steepening process that leads to a shocked N-wave. For a linearly unstable regime, pressure oscillations reach a limit cycle which is independent of the characteristics of the initial disturbances and depends only on combustion parameters and operating conditions. For the 1.5 MW gas generator under development in KARI, the numerical results show good agreement with experimental data from hot-firing tests.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.210-211
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• 2018

In general, the dam break problem is demonstrated to simulate open-channel disturbance due to large violent waves. These days, the large violent waves at shore and coastline can be seen frequently such like tsunami. The conventional computational fluid dynamics program based on Grid system, can be used to simulate this problem with large deformation of free surface in the restricted condition due to its limitation. The particle method based on fully Lagrangian approach is able to simulate large deformation of free surface by tracking each particles. In this study, the simulation of disturbance of mobile-bed due to large violent waves was investigated by using particle method.