• 대한약침학회지
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• 제16권1호
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• pp.43-49
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• 2013

Objective: Pyungwi-san (PWS) plays a role in a number of physiologic and pharmacologic functions in many organs. Interstitial cells of Cajal (ICCs) are pacemaker cells that generate slow waves in the gastrointestinal (GI) tract. We aimed to investigate the beneficial effects of PWS in mouse small-intestinal ICCs. Methods: Enzymatic digestion was used to dissociate ICCs from the small intestine of a mouse. The whole-cell patch-clamp configuration was used to record membrane potentials from the cultured ICCs. Results: ICCs generated pacemaker potentials in the GI tract. PWS produced membrane depolarization in the current clamp mode. Pretreatment with a $Ca^{2+}$-free solution and a thapsigargin, a $Ca^{2+}$-ATPase, inhibitor in the endoplasmic reticulum, eliminated the generation of pacemaker potentials. However, only when the thapsigargin was applied in a bath solution, the membrane depolarization was not produced by PWS. Furthermore, the membrane depolarizations due to PWS were inhibited not by U-73122, an active phospholipase C inhibitor, but by chelerythrine and calphostin C, protein kinase C inhibitors. Conclusions: These results suggest that PWS might affect GI motility by modulating the pacemaker activity in the ICCs.

• Ocean Systems Engineering
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• 제3권4호
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• pp.257-273
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• 2013

Top tensioned riser (TTR) is often used in a floating oil/gas production system deployed in deep water for oil/gas transport. This study focuses on the extension of the existing numerical code, known as CABLE3D, to allow for static and dynamic simulation of a TTR connected to a floating structure through a tensioner system or buoyancy can, and restrained by riser guides at different elevations. A tensioner system usually consists of three to six cylindrical tensioners. Although the stiffness of individual tensioner is assumed to be linear, the resultant stiffness of a tensioner system may be nonlinear. The vertical friction between a TTR and the hull at its riser guide is neglected assuming rollers are installed there. Near the water surface, a TTR is forced to move horizontally due to the motion of the upper deck of a floating structure as well as related riser guides. The extended CABLE3D is then integrated into a numerical code, known as COUPLE, for the simulation of the dynamic interaction among the hull of a floating structure, such as spar or TLP, its mooring system and riser system under the impact of wind, current and waves. To demonstrate the application of the extended CABLE3D and its integration with COUPLE, the numerical simulation is made for a truss spar under the impact of Hurricane "Ike". The mooring system of the spar consists of nine mooring lines and the riser system consists of six TTRs and two steel catenary risers (SCRs).

• Current Optics and Photonics
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• 제2권3호
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• pp.261-268
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• 2018

Stimulated polariton scattering (SPS) from the $A_1$ transverse optical (TO) modes of $BaTiO_3$ bulk crystal generating a terahertz (THz) wave with the noncollinear phase-matching (NPM) condition is theoretically investigated. To our best knowledge, this is the first report on THz wave generation from $BaTiO_3$ bulk crystal via SPS. Phase-matching (PM) characteristics in the NPM configuration are analyzed. Effective parametric gain lengths for the Stokes and THz waves in the NPM configuration are calculated. The effective parametric gain coefficient and absorption coefficient of the THz wave in $BaTiO_3$ are theoretically simulated. The THz phonon flux densities generated via SPS in $BaTiO_3$ are theoretically calculated by solving the coupled wave equations under the NPM condition. The PM characteristics and THz-wave parametric gain characteristics in $BaTiO_3$ are compared to those in $MgO:LiNbO_3$. The results of the analysis indicate that $BaTiO_3$ is an attractive optical crystal for efficient THz wave generation via SPS.

• Geomechanics and Engineering
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• 제36권3호
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• pp.231-245
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• 2024

In recent decades, the protection and vulnerability of civil structures under explosion loads became a critical issue in terms of security, which may cause loss of lives and structural damage. Concrete retaining walls also restrict soils and slopes from displacements; meanwhile, intensive temporary loading may cause massive damage. In the current study, the modified Johnson-Holmquist (also known as J-H2) material model is implemented for concrete materials to model damages into the ABAQUS through user-subroutines to predict the blasting-induced concrete damages and volume strains. For this purpose, a 3D finite-element model of the concrete retaining wall was conducted in coupled Eulerian-Lagrangian simulation. Subsequently, a blast load equal to 500 kg of TNT was considered in three different positions due to UFC 3-340-02. Influences of the critical parameters in smooth blastings, such as distance from a free face, position, and effective blasting time, on concrete damage rate and destroy patterns, are explored. According to the simulation results, the concrete penetration pattern at the same distance is significantly influenced by the density of the progress environment. The result reveals that the progress of waves and the intensity of damages in free-air blasting is entirely different from those that progress in a dense surrounding atmosphere such as soil. Half-damaged elements in air blasts are more than those of embedded explosions, but dense environments such as soil impose much more pressure in a limited zone and cause more destruction in retaining walls.

• 한국강구조학회 논문집
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• 제29권6호
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• pp.401-410
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• 2017

본 연구에서는 긴장재로 계류된 해중 터널에서 긴장재의 느슨해짐에 따른 동적 불안정 거동에 대해 다룬다. 해중 터널의 설계는 파랑 및 조류 등 유체력에 의해 지배받는다. 특히 시간에 따라 지속적으로 크기 및 작용방향이 변하는 파랑은 해중 터널의 동적 거동을 직접적으로 야기하게 되는데, 파랑에 의한 부유 튜브의 운동은 계류선 내력의 동적 변동을 유발하게 되고, 이 힘의 변화는 계류선의 강도설계 뿐 만 아니라 피로 설계에도 직접적인 영향을 미친다. 파랑에 의한 터널의 운동이 극심할 경우, 계류선의 장력은 모두 소실될 수 있는데, 이 때 계류선이 느슨해짐에 따라 일시적으로 부유 터널의 운동에 대한 저항성이 사라져 동적 불안정 거동이 유발 될 수 있다. 이에 본 연구에서는 유체-구조동역학 해석기법을 통해 해중 터널 긴장재의 느슨해짐 발생 시 부유 튜브의 동적 불안정 거동에 대해 분석하였다. 특히 해중터널의 중요 설계 인자인 흘수, 부력-자중 비율(Buoyancy-Weight Ratio, BWR), 긴장재 기울임이 동적 불안정 거동에 미치는 영향에 대해 분석하였다.

• 한국해양공학회지
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• 제28권2호
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• pp.133-139
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• 2014

Offshore wind turbines have been constructed extensively throughout the world. These turbines are subjected to approximately $10^8$ horizontal load cycles produced from wind, waves, and current during their lifetimes. Therefore, the accumulated displacement of the foundation under horizontal cyclic loading has significant effects on the foundation design of a wind turbine. Akili(2006) and Achmus et al.(2009) performed cyclic triaxial tests on dry sands and proposed an empirical model for predicting the accumulated plastic strain of sands under long-term cyclic loading. In this study, cyclic triaxial tests were performed to analyze the cyclic loading behaviors of dry sands. A total of 27 test cases were performed by varying three parameters: the relative density of the sands, cyclic load level, and confining stress. The test results showed that the accumulated plastic strain increased with an increase in the cyclic load level and a decrease in the relative density of the sand. The confining stress had less effect on the plastic strain. In addition, the plastic strain at the 1st loading cycle was about 57% of the accumulated strain at 1,000 cycles. Finally, the input parameters of the empirical models of Akili(2006) and Achmus et al.(2009) were evaluated by using the relative density of the sand and the cyclic load level.

• 한국제4기학회지
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• 제4권1호
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• pp.15-26
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• 1990

한국 동해 대륙붕 표층 퇴적물은 대부분 육성기원 쇄설성 퇴적물로 이루어져있으며, 이 퇴적물은 홀로세 해수면 변동의 영향을 잘 나타내고 있다. 퇴적물은 연안이나 내대륙붕에서는 이질사 혹은 사닐니로 이루어져 있고 혹은 자갈들이 나타나는 경우도 있으며, 외해로 갈수록 세립화하는 경향을 보여 외대륙붕에는 대부분이 세립의 이질 퇴적물로 이루어져 있다. 그러나 수심 약 130-150m의 붕단 부근에서는 사질, 니질사, 역니질사 등의 조립 퇴적물이 나타나며 이들은 소위 위스콘신 빙하기의 해수면이 낮았을 때 수심이 얕은 연안환경에서 퇴적된 잔류퇴적물로 생각된다. 연구해역 대륙붕에서의 현생 퇴적물 분포는 파도나 해류 등에 의하여 연안이나 수십이 얕은 곳에는 세립퇴적물이 쌓이지 못한 것으로 생각되며, 특히 대마해류에서 분리된 동한난류는 남해로부터 동해 대륙붕으로 세립퇴적물을 운반하고 분포시키는 데 큰 영향을 미칠 것으로 추정된다.

• 한국사회복지학
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• 제68권3호
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• pp.105-125
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• 2016

학교결석은 학업중단이나 비행 범죄에 대한 잠정적인 조기 예측요인으로 그 중요성이 강조되고 있다. 이에 본 연구는 생태체계적 관점을 토대로 시간의 흐름에 따라 아동의 학교결석일에 영향을 미치는 다양한 보호요인과 위험요인을 경험적으로 검증하였다. 이를 위해 한국아동 청소년패널조사에서 초4 패널의 2차년도와 3차년도의 자료를 활용하였으며, 초등학교 2,378명을 대상으로 패널회귀분석의 고정효과모형을 적용하였다. 분석결과, 아동의 컴퓨터 사용시간, 부모의 학대, 학교활동참여정도, 학업성적이 학교결석일 변화에 중요한 영향을 미치는 것으로 나타났다. 특히 컴퓨터 사용시간, 부모의 학대는 학교결석에 위험요인으로 작용하였으며, 학교활동참여와 학업성적은 학교결석에 보호요인으로 작용하였다. 이러한 연구결과들을 바탕으로 우리나라 아동 청소년 문제에 대한 예방적 접근의 필요성을 강조하고 학교결석에 대한 체계적인 모니터링 시스템 구축의 필요성을 제언하였다.

• Geomechanics and Engineering
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• 제19권1호
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• pp.11-20
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• 2019

The use of electrokinetic dissipation method to study the fluid flow law in micro-pores is of great significance to reservoir rock microfluidics. In this paper, the micro-capillary theory was combined with the coupling model of the seepage field and the current field under the excitation of the harmonic signal, and the coupling theory of the electrokinetic effect under the first-order approximation condition was derived. The dissipation equation of electrokinetic dissipation and viscous resistance dissipation and its solution were established by using Green's function method. The physical and mathematical models for the electrokinetic dissipation of reservoir rocks were constructed. The microscopic mechanism of the electrokinetic dissipation of reservoir rock were theoretically clarified. The influencing factors of the electrokinetic dissipation frequency of the reservoir rock were analyzed quantitatively. The results show that the electrokinetic effect transforms the fluid flow profile in the pores of the reservoir from parabolic to wavy; under low-frequency conditions, the apparent viscosity coefficient is greater that one and is basically unchanged. The apparent viscosity coefficient gradually approaches 1 as the frequency increases further. The viscous resistance dissipation is two orders of magnitude higher than the electrokinetic effect dissipation. When the concentration of the electrolyte exceeds 0.1mol/L, the electrokinetic dissipation can be neglected, while for the electrolyte solution (<$10^{-2}M$) in low concentration, the electrokinetic dissipation is very significant and cannot be ignored.

• 한국해양학회지:바다
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• 제28권1호
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• pp.51-61
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• 2023

음향은 수중에서 원거리 전파가 가능하여 수심 측량, 수중 물체 탐지, 수중 통신, 유속 측정 등 다방면에서 해양관측에 널리 사용되고 있다. 본 논문에서는 해저면 계류형태의 압력측정 전도음향측심기(Pressure-recording Inverted Echo Sounder, PIES)를 활용하여 관측 가능한 해양물리현상(해류, 중규모 소용돌이, 내부파, 해면고도변화 등)에 대해 서술한다. 이어서 PIES장비 회수 없이 음향을 활용한 원격 자료획득법, 자동 자료전송 팝업 부표(Pop-up Data Shuttle, PDS)를 활용한 최신의 원격 자동자료획득법을 소개하고, 향후 실현 가능한 (준)실시간 원격 자동자료획득법을 덧붙인다.