• International Journal of Naval Architecture and Ocean Engineering
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• 제10권3호
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• pp.393-402
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• 2018

While interacting with a sloping structure, an ice floe may fracture in different patterns. For example, it can be local bending failure or global splitting failure depending on the contact properties, geometry and confinement of the ice floe. Modelling these different fracture patterns as a natural outcome of numerical simulations is rather challenging. This is mainly because the effects of crack propagation, crack branching, multi fracturing modes and eventual fragmentation within a solid material are still questions to be answered by the on-going research in the Computational Mechanic community. In order to simulate the fracturing of ice floes with arbitrary geometries and confinement; and also to simulate the fracturing events at such a large scale yet with sufficient efficiency, we propose a semi-analytical/empirical and semi-numerical approach; but with focus on the global splitting failure mode in this paper. The simulation method is validated against data we collected during the Oden Arctic Technology Research Cruise 2015 (OATRC2015). The data include: 1) camera images based on which we specify the exact geometry of ice floes before and after an impact and fracturing event; 2) IMU data based on which the global dynamic force encountered by the icebreaker is extracted for the impact event. It was found that this method presents reasonably accurate results and realistic fracturing patterns upon given ice floes.

• The Plant Pathology Journal
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• 제27권4호
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• pp.315-323
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• 2011

Soybean plants infected with Bean pod mottle virus (BPMV) develop acute symptoms that usually decrease in severity over time. In other plant-virus interactions, this type of symptom recovery has been associated with degradation of viral RNAs by RNA silencing, which is accompanied by the accumulation of virus-derived small interfering RNAs (siRNAs). In this study, changes in the accumulation of BPMV siRNAs were investigated in soybean plants infected with BPMV alone, or infected with both BPMV and Soybean mosaic virus (SMV) and in transgenic soybean plants expressing SMV helper component-protease (HC-Pro). In many potyviruses, HC-Pro is a potent suppressor of RNA silencing. In plants infected with BPMV alone, accumulation of siRNAs was positively correlated with symptom severity and accumulation of BPMV genomic RNAs. Plants infected with both BPMV and SMV and BPMV-infected transgenic soybean plants expressing SMV HC-Pro exhibited severe symptoms characteristic of BPMVSMV synergism, and showed enhanced accumulation of BPMV RNAs and siRNAs compared to plants infected with BPMV alone and nontransgenic plants. Likewise, SMV HC-Pro enhanced the accumulation of siRNAs produced from a silenced green fluorescent protein gene in transient expression assays, while the P19 silencing suppressor of Tomato bushy stunt virus did not. Consistent with the modes of action of HC-Pro in other systems, which have shown that HC-Pro suppresses RNA silencing by preventing the unwinding of duplex siRNAs and inhibiting siRNA methylation, these studies showed that SMV HC-Pro interfered with the activities of RNA-induced silencing complexes, but not the activities of Dicer-like enzymes in antiviral defenses.

• 대한기계학회논문집A
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• 제35권3호
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• pp.317-323
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• 2011

본 논문에서는 원자력 발전소 폴라 크레인(polar crane)의 설계를 위해 유한요소법을 통한 내진해석을 수행하였다. 모드 해석(modal analysis)을 통하여 폴라 크레인의 고유진동수와 진동형상을 파악하고 응답스펙트럼(response spectrum)을 통해 폴라 크레인의 내진 안전성을 평가하였다. 그리고 액체저장탱크에 대한 내진해석을 유한요소법을 이용하여 수행하였는데, 탱크가 요동시에 액체가 탱크 외벽에 가하는 힘을 고려한 슬로싱해석과 안전정지지진 하중 조건에서의 해석을 수행하였다. 본 논문에서 유한요소해석 상용코드인 ANSYS를 이용하여 내진해석에 필요한 해석기법과 과정 등을 설계 시에 활용할 수 있도록 제안하였다.

• 한국항공우주학회지
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• 제35권6호
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• pp.503-508
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• 2007

본 연구에서는 대변형 보이론을 이용하여 무베어링 로터 시스템의 공력탄성학적 안정성 해석을 수행하였다. 무베어링 로터 시스템의 유연보, 토오크 튜브, 그리고 메인 블레이드를 각각 탄성 운동을 하는 보로 가정하고, 1차원 보 요소로 모델링을 하였다. 외력으로는 2차원 준-정상 공기력 모델을 적용하였으며, 보의 유한 요소 지배방정식은 헤밀턴 원리(Hamilton's Principle)를 이용하여 얻었다. 공력탄성학적 안정성 해석을 수행하기 위하여 정지 비행시는 모달 접근법을, 전진 비행시는 주기적인 특성을 갖는 비선형 정적 트림해를 얻기 위해 동체 평형을 고려한 연계 평형 해석을 통한 완전 유한요소 방정식을 이용하였다. 본 연구에서 구한 결과를 기존의 적정변형 보이론에 모달 접근법을 이용한 무베어링 로터 시스템의 결과와 비교하였다.

• 대한약리학회지
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• 제8권2호
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• pp.35-39
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• 1972

Previous studies on the effect of the visible lights on the organism have shown the possible influences on the nervous system. It was reported that the illumination of blue beam increased the sympathetic tone and that of red beam increased the parasympathetic tone. The pharmacological actions of the sympathomimetics were also known to be altered by various visible lights. But their modes and mechanisms of actions on the nervous system have not been clarified and is obscure. To elucidate the precise mechanism of action of the visible lights on the nervous system, present study was made to observe the survival time of the mole living in the dark environment, under the illumination of the various visible lights and influences of several drugs. The results are summerized as follows: 1. The illumination of the natural sun light caused the survival time of the mole to be shortened and visible monochromatic beams (red, blue and green) even more markedly shortened the survival time. No significant difference was noted depending on the wave length of the chromatic beam. 2. The shortened survival time caused by the visible monochromatic lights was prolonged by strychnine but not affected by morphine. 3. The survival time under the illumination of the visible monochromatic lights was prolonged by acetylcholine and physostigmine. 4. The shortened survival time under the illumination of the monochromatic visible lights was not affected by adrenaline but prolonged by priscoline. It is suggested that the shortened survival time of the mole by the illumination of the visible lights can be prolonged by the stimulation of central and parasympathetic nervous system and blocking of the sympathetic nervous system.

• Steel and Composite Structures
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• 제28권5호
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• pp.589-606
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• 2018

The previous studies reflected the significant effect of neutral-axis position and coupling of in-plane and out-of-plane displacements on behavior of functionally graded (FG) nanobeams. In thin FG beam, this coupling can be eliminated by a proper choice of the reference axis. In shear deformable FG nanobeam, not only this coupling can't be eliminated but also the position of neutral-axis is dependent on through-thickness distribution of shear strain. For the first time, in this paper it is avoided to guess a shear strain shape function and the exact shape function and consequently the exact position of neutral axis for arbitrary gradation of higher order nanobeam are obtained. This paper presents new methodology based on differential transform and collocation methods to solve coupled partial differential equations of motion without any simplifications. Using exact position of neutral axis and higher order beam kinematics as well as satisfying equilibrium equations and traction-free conditions without shear correction factor requirement yields to better results in comparison to the previously published results in literature. The classical rule of mixture and Mori-Tanaka homogenization scheme are considered. The Eringen's nonlocal continuum theory is applied to capture the small scale effects. For the first time, the dependency of exact position of neutral axis on length to thickness ratio is investigated. The effects of small scale, length to thickness ratio, Poisson's ratio, inhomogeneity of materials and various end conditions on vibration and buckling of local and nonlocal FG beams are investigated. Moreover, the effect of axial load on natural frequencies of the first modes is examined. After degeneration of the governing equations, the exact new formulas for homogeneous nanobeams are computed.

• Structural Engineering and Mechanics
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• 제64권6권
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• pp.703-721
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• 2017

The experimental study of the behavior of dry medium and loose sandy soil under the action of a single impulsive load is carried out. Different falling masses from different heights were conducted using the falling weight deflectometer (FWD) to provide the single pulse energy. The responses of soils were evaluated at different locations (vertically below the impact plate and horizontally away from it). These responses include; displacements, velocities, and accelerations that are developed due to the impact acting at top and different depth ratios within the soil using the falling weight deflectometer (FWD) and accelerometers (ARH-500A Waterproof, and Low capacity Acceleration Transducer) that are embedded in the soil and then recorded using the multi-recorder TMR-200. The behavior of medium and loose sandy soil was evaluated with different parameters, these are; footing embedment, depth ratios (D/B), diameter of the impact plate (B), and the applied energy. It was found that increasing footing embedment depth results in: amplitude of the force-time history increases by about 10-30%. due to increase in the degree of confinement with the increasing in the embedment, the displacement response of the soil will decrease by about 25-35% for loose sand, 35-40% for medium sand due to increase in the overburden pressure when the embedment depth increased. For surface foundation, the foundation is free to oscillate in vertical, horizontal and rocking modes. But, when embedding a footing, the surrounding soil restricts oscillation due to confinement which leads to increasing the natural frequency, moreover, soil density increases with depth because of compaction, that is, tendency to behave as a solid medium.

• 대한약침학회지
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• 제19권1호
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• pp.7-15
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• 2016

Objectives: Malaria has been a major global health problem in recent times with increasing mortality. Current treatment methods include parasiticidal drugs and vaccinations. However, resistance among malarial parasites to the existing drugs has emerged as a significant area of concern in anti-malarial drug design. Researchers are now desperately looking for new targets to develop anti-malarials drug which is more target specific. Malarial parasites harbor a plastid-like organelle known as the 'apicoplast', which is thought to provide an exciting new outlook for the development of drugs to be used against the parasite. This review elaborates on the current state of development of novel compounds targeted againstemerging malaria parasites. Methods: The apicoplast, originates by an endosymbiotic process, contains a range of metabolic pathways and housekeeping processes that differ from the host body and thereby presents ideal strategies for anti-malarial drug therapy. Drugs are designed by targeting the unique mechanism of the apicoplasts genetic machinery. Several anabolic and catabolic processes, like fatty acid, isopenetyl diphosphate and heme synthess in this organelle, have also been targeted by drugs. Results: Apicoplasts offer exciting opportunities for the development of malarial treatment specific drugs have been found to act by disrupting this organelle's function, which wouldimpede the survival of the parasite. Conclusion: Recent advanced drugs, their modes of action, and their advantages in the treatment of malaria by using apicoplasts as a target are discussed in this review which thought to be very useful in desigining anti-malarial drugs. Targetting the genetic machinery of apicoplast shows a great advantange regarding anti-malarial drug design. Critical knowledge of these new drugs would give a healthier understanding for deciphering the mechanism of action of anti-malarial drugs when targeting apicoplasts to overcome drug resistance.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권9호
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• pp.427-433
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• 2001

A linear ultrasonic motor was designed by a combination of the first longitudinal and fourth bending mode, and the motor consisted of a straight aluminum alloys bar bonded with a piezoelectric ceramic element as a driving element. That is,$L_1-B_4$ linear ultrasonic motor can be constructed by a multi-mode vibrator of longitudinal and bending modes. Linear ultrasonic motors are based on an elliptical motion on the surface elastic body, such as bar or plates. In general, the natural resonance frequency of the stator is used as a driving frequency of the motor which provides a large elliptical motion. The corresponding eigenmode of one resonance frequency can be excited twice at the same time with a Phase shift of 90 degrees in space and time. And the rotation can be reversed by changing the phase between the two signals from sin$\omega$t to cos$\omega$t. Moreover, the tangential force pushes the slider(rotor) and, therefore, determines the thrust and speed of the motor. The experimental results of fabrication motors, bimorph-tyPe motor showed more excellent than unimorph-type. The maximum speed of TBL-200, TBL-300, TBL-400, TBL -220, TBL-310 and TBL-420 motors were 0.12, 0.37, 0.39, 0.14, 0.55 and $0.60ms6{-1}$, respectively. And the efficiency were reported 1.15, 7.9, 6.6, 2.36, 10.1 and 16.5%, respectively. That time, output thrust of the motor was a strong(1~2N) and the weight of stator was a lightness(5~7g).

• 한국전산구조공학회논문집
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• 제27권5호
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• pp.379-384
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• 2014

본 논문은 갠트리 크레인의 설계를 위해 컨테이너 하역작업 시 특정하중 조건하의 RTGC(Rubber Tired Gantry Crane)의 동적거동과 그에 따른 윤하중을 분석한 내용을 기술하고 있다. 먼저 RTGC의 동적거동을 살펴보기 위해 거대 구조물인 크레인의 유한요소 모델을 개발하고 고유진동수와 고유모드의 모달시험결과를 이용하여 유한요소모델을 검증하였다. RTGC의 기타 부속품은 3차원 CAD모델링을 통해 다물체 동역학해석 소프트웨어인 ADAMS에서 강체로 모델링하였다. 본 연구에서 하중 조건은 일반적인 컨테이너의 이송조건(OP1)과 외부부하조건 없이 단순히 트롤리를 이용하여 컨테이너를 하역하는 2가지 경우로 고려하였다. 해석 결과 RTGC의 컨테이너 작업 시 발생하는 크레인의 진동은 거대 구조물의 강성과 변형에 주로 기인함을 확인하였으며 이러한 크레인의 진동은 RTGC의 움직임을 발생시켜 컨테이너 하역작업 불능 등의 거동을 발생시킬 수 있음을 분석할 수 있었다.