• 한국지반공학회논문집
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• 제26권2호
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• pp.5-14
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• 2010

본 연구에서는 지반의 응력상태와 동하중을 실제 지반 및 지진하중과 가장 가깝게 모사하기 위하여 여러 압밀 응력비(K) 조건으로 시료를 구속시킨 후 실지진 하중을 이용해 진동삼축시험을 수행하였다. 시험시 시료는 액상화가 발생 가능한 상대밀도 50%의 주문진 표준사를 사용하였다. 시험은 K를 0.5~1.0까지 변화 시키며 구속된 시료에 Ofunato 지진파와 Hachinohe 지진파를 사용하여 축하중을 변화 시키며 진동삼축시험을 수행하여 과잉간극수압비의 발현 정도에 따라 액상화 저항강도를 판단하였다. 연구 결과 K값이 클수록 과잉간극수압비의 발현이 크게 되었고, 다른 조건이 같을 때 등방구속된 시료에서 과잉간극수압비의 발현이 가장 잘되었다. 즉, 등방 구속된 시료가 이방 구속된 시료보다 동일 조건에서 액상화 저항강도가 더 크다는 사실에 반하는 것을 알 수 있었다. 시험 결과 값을 이용하여 K에 따른 최대과잉간극수압비를 유도할 수 있었고, 그것을 유효구속압과 축차 하중을 이용하여 선형으로 정규화 하였으며, 등방 구속된 시료의 액상화 저항강도로부터 이방 구속된 시료의 액상화 저항강도를 구할 수 있는 보정계수를 제안하였다.

• 한국임상수의학회지
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• 제40권2호
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• pp.130-134
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• 2023

A 12-year-old Standard Poodle presented with intermittent weakness and occasional dyspnea at the Veterinary Medicine Teaching Hospital of Kangwon National University. A grade of 4 out of 6 systolic murmur with an irregular tachycardic rhythm was auscultated on both sides of the chest. Systolic blood pressure was 140 mmHg. Panting was noticed in the hospital, but there was no crackle sound. Blood analysis revealed mild increases in liver panel levels (alanine aminotransferase 149 [reference interval, 19-70] U/L; and alkaline phosphatase, 185 [reference interval, 15-127] U/L) and severe increases in cardiac biomarker levels (n-terminal pro-brain natriuretic peptide, 4169 [reference interval, 50-900] pmol/L; and cardiac troponin I, 0.22 [reference interval, 0.03-0.12] ng/mL). On electrocardiography, irregularly irregular supraventricular tachycardic rhythm with an f-wave and no distinct p-wave was observed. Generalized cardiomegaly with an enlarged right atrium and left ventricle was confirmed on thoracic radiography. Moreover, hepatomegaly and an enlarged caudal vena cava were observed. Echocardiographic evaluation revealed a fibromuscular diaphragm in the right ventricle. Because of the obstructive lesion in the right ventricle, the right atrium and ventricle were enlarged (right atrial area index, 38.82 cm²/m² [reference interval, 4.2-10.2 cm²/m²]; right ventricle end-diastolic area index, 14.152 cm²/m² [reference interval, 4.9-10.92 cm²/m²]). Accordingly, the patient was diagnosed with double-chambered right ventricle (DCRV). Pimobendan, furosemide, enalapril, diltiazem, and S-adenosylmethionine (SAMe) were prescribed, and all symptoms were relieved. DCRV is a right-sided congenital heart defect resembling pulmonic valve stenosis. If symptoms are not severe, medical therapy can be facilitated without surgery or the balloon dilation.

• 한국항해항만학회지
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• 제31권8호
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• pp.675-681
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• 2007

다방향 불규칙파 중에서의 인장계류식 해양구조물(TLP)의 구조응답 해석을 수행함으로써 다방향 불규칙파가 구조응답에 미치는 영향을 평가하고 있다. 인장계류식 해양구조물에 작용하는 파강제력과 동유체력은 3차원 특이점분포법을 사용하여 각각의 외각요소에 대해 평가하였다. 3차원 골조요소로 모델링하여 유한요소법에 의해 구조응답을 평가하였으며, 인장계류식 해앙구조물의 각 외각요소간의 유체역학적 상호간섭을 고려하여 구조응답을 해석하였다. 구조응답의 주파수 응답함수와 다방향파의 스펙트럼을 이용하여 다방향 불규칙파에 대한 해양구조물의 구조응답 스펙트럼을 구하여 다방향 불규칙파가 인장계류식 해양구조물의 구조응답에 미치는 영향을 평가하였다.

• 한국강구조학회 논문집
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• 제29권1호
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• pp.49-60
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• 2017

부유식 구조물의 계류선의 설계는 강도뿐만 아니라 피로수명 측면에서도 검토가 반드시 요구된다. 일반적으로 계류선의 피로 설계에는 동적 응력을 야기하는 하중이 지배적인 영향을 미치게 된다. 즉, 파랑이 주요 설계 하중으로 고려가 된다. 본 연구에서는 불규칙 파랑에 대한 해중 터널 계류선의 피로 손상 특성에 대해 분석한다. 시간 이력 유체-구조 동역학 해석을 통해 특정 환경 하중에 대한 해중터널의 동적 운동 및 계류선에 발생하는 장력과 응력을 계산하고, Rainflow 집계법 및 Palmgren-Miner의 법칙 그리고 DNV 기준에서 제시하는 해양구조물 설계를 위한 S-N 곡선을 고려하여 단기 피로 손상을 추정한다. 해중 터널의 계류 형식과 유사한 계류 형식을 갖는 인장각 플랫폼의 텐던 설계를 참고하여 100년 재현 주기 파랑이 48시간 지속되는 조건을 가정하여 이 환경 하중에 의한 피로 손상도를 추정한다. 본 해석 절차를 따르며, 함체의 흘수와 계류선의 간격 및 초기 기울임 각도가 피로 손상도에 미치는 영향을 분석한다.

• 한국해양공학회지
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• 제33권1호
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• pp.1-9
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• 2019

This paper considers a numerical assessment of the self-propulsion performance of a damaged ferry carrying cars in irregular waves. Computational fluid dynamics(CFD) simulations were performed to see whether the ferry complied with the Safe Return to Port (SRtP) regulations of Lloyd's register, which require that damaged passenger ships should be able to return to port with a speed of 6 knots (3.09 m/s) in Beaufort 8 sea conditions. Two situations were considered for the damaged conditions, i.e., 1) the portside propeller was blocked but the engine room was not flooded and 2) the portside propeller was blocked and one engine room was flooded. The self-propulsion results for the car ferry in intact condition and in the damaged conditions were assessed as follows. First, we validated that the portside propeller was blocked in calm water based on the available experimental results provided by KRISO. The active thrust of starboard propeller with the portside propeller blocked was calculated in Beaufort 8 sea conditions, and the results were compared with the experimental results provided by MARIN, and there was reasonable agreement. The thrust provided by the propeller and the brake horsepower (BHP) with one engine room flooded were compared with the values when the engine room was not flooded. The numerical results were compared with the maximum thrust of the propeller and the maximum brake horse power of the engine to determine whether the damaged car ferry could attain a speed of 6 knots(3.09 m/s).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.842-848
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• 2013

Developments of Solid-State Gyroscopy during last decades are impressive and were based on thin-walled shell resonators like HRG or CRG made from fused quartz or leuko-sapphire. However, a number of design choices for inertial-grade gyroscopes, which can be used for high-g applications and for mass- or middle-scale production, is still very limited. So, considerations of fundamental physical effects in solids that can be used for development of a miniature, completely solid-state, and lower-cost sensor look urgent. There is a variety of different types of bulk acoustic (elastic) waves (BAW) in anisotropic solids. Shear waves with different variants of their polarization have to be studied especially carefully, because shear sounds in glasses and crystals are sensitive to a turn of the solid as a whole, and, so, they can be used for development of gyroscopic sensors. For an isotropic medium (for a glass or a fine polycrystalline body), classic Lame's theorem (so-called, a general solution of Elasticity Theory or Green-Lame's representation) has been modified for enough general case: an elastic medium rotated about an arbitrary set of axes. Travelling, standing, and mixed shear waves propagating in an infinite isotopic medium (or between a pair of parallel reflecting surfaces) have been considered too. An analogy with classic Foucault's pendulum has been underlined for the effect of a turn of a polarizational plane (i.e., an integration effect for an input angular rate) due to a medium's turn about the axis of the wave propagation. These cases demonstrate a whole-angle regime of gyroscopic operation. Single-crystals are anisotropic media, and, therefore, to reflect influence of the crystal's rotation, classic Christoffel-Green's tensors have been modified. Cases of acoustic axes corresponding to equal velocities for a pair of the pure-transverse (shear) waves have of an evident applied interest. For such a special direction in a crystal, different polarizations of waves are possible, and the gyroscopic effect of "polarizational precession" can be observed like for a glass. Naturally, formation of a wave pattern in a massive elastic body is much more complex due to reflections from its boundaries. Some of these complexities can be eliminated. However, a non-homogeneity has a fundamental nature for any amorphous medium due to its thermodynamically-unstable micro-structure, having fluctuations of the rapidly-frozen liquid. For single-crystalline structures, blockness (walls of dislocations) plays a similar role. Physical nature and kinematic particularities of several typical "drifts" in polarizational BAW gyros (P-BAW) have been considered briefly too. They include irregular precessions ("polarizational beats") due to: non-homogeneity of mass density and elastic moduli, dissymmetry of intrinsic losses, and an angular mismatch between propagation and acoustic axes.

• 한국해양공학회지
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• 제31권3호
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• pp.196-201
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• 2017

A cylindrical structure has a very long period of heave and pitch motion response in ocean waves. To obtain the dynamic stability of a cylindrical structure, it is necessary to obtain the suitable metacentric height (GM). However, in a structure with sufficient metacentric height, Mathieu instability can occur if the natural frequency of the heave motion is double the natural frequency of the roll and pitch motion. This study carried out numerical calculations and experiments for vertical-axis wind turbines with cylindrical floaters, which had three different centers of gravity. In the regular wave experiment, the divergence of the structure motion without yaw was observed when the natural frequency of the heave motion was double the natural frequency of the roll and pitch motion. In the irregular wave experiment, the motion spectra of the structures with the different centers of gravity were compared, and one was very high when the natural frequency of the heave motion was double the natural frequency of the roll and pitch motion.

• Applied Microscopy
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• 제39권2호
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• pp.199-204
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• 2009

본 연구는 펌 염색을 한 번도 경험하지 않은 13세의 건강한 여성의 모발에 펌을 반복 시술하여 모발 표면의 형태적 변화를 주사전자현미경을 사용하여 관찰하였다. 펌1차 시술한 모발 표면은 큐티클 세포의 끝 부분들이 불규칙하게 쪼개져 나갔으며, 비늘의 가장자리 끝부분이 거칠은 상태로 관찰되었다. 그리고 큐티클세포들이 분리되고 공간이 형성되면서 표면 쪽으로 부풀어 오른 것을 확인하였다. 펌3차 시술한 모발의 경우에는 모발 표면에서 큐티클 세포와 세포 사이가 들떠서 분리되어 있고 중첩된 큐티클층 표면에 중첩된 비늘은 표면적이 불규칙하게 나타났다. 표면에 부서진 큐티클 세포의 세포질 일부가 부착되어 있으며 세포질 내의 내큐티클에는 공포가 형성되어 있었다. 펌의 횟수가 증가할수록 큐티클층과 피질의 분리가 쉽게 일어나는 것을 확인하였다.

• Ocean Systems Engineering
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• 제7권3호
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• pp.179-193
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• 2017

Dynamic response analysis of offshore triceratops with stiffened buoyant legs under impact and non-impact waves is presented. Triceratops is relatively new-generation complaint platform being explored in the recent past for its suitability in ultra-deep waters. Buoyant legs support the deck through ball joints, which partially isolate the deck by not transferring rotation from legs to the deck. Buoyant legs are interconnected using equally spaced stiffeners, inducing more integral action in dispersing the encountered wave loads. Two typical nonlinear waves under very high sea state are used to simulate impact and non-impact waves. Parameters of JONSWAP spectrum are chosen to produce waves with high vertical and horizontal asymmetries. Impact waves are simulated by steep, front asymmetric waves while non-impact waves are simulated using Stokes nonlinear irregular waves. Based on the numerical analyses presented, it is seen that the platform experiences both steady state (springing) and transient response (ringing) of high amplitudes. Response of the deck shows significant reduction in rotational degrees-of-freedom due to isolation offered by ball joints. Weak-asymmetric waves, resulting in non-impact waves cause steady state response. Beat phenomenon is noticed in almost all degrees-of-freedom but values in sway, roll and yaw are considerably low as angle of incidence is zero degrees. Impact waves cause response in higher frequencies; bursting nature of pitch response is a clear manifestation of the effect of impact waves on buoyant legs. Non-impact waves cause response similar to that of a beating phenomenon in all active degrees-of-freedom, which otherwise would not be present under normal loading. Power spectral density plots show energy content of response for a wide bandwidth of frequencies, indicating an alarming behaviour apart from being highly nonlinear. Heave, being one of the stiff degrees-of-freedom is triggered under non-impact waves, which resulted in tether tension variation under non-impact waves as well. Reduced deck response aids functional requirements of triceratops even under impact and non-impact waves. Stiffened group of buoyant legs enable a monolithic behaviour, enhancing stiffness in vertical plane.

• 한국지진공학회논문집
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• 제9권4호
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• pp.67-74
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• 2005

이 논문에서는 포화된 2상 지반의 동적해석에서 원역을 모형화하기 위한 새로운 무한요소를 제안하였다. 무한요소법은 무한영역 또는 반무한영역을 모형화해야 하는 공학문제에 효과적으로 적용되어 왔다. 그러나 현재까지 개발된 2상지반의 동적해석을 위한 무한요소는 형상함수에 사용될 수 있는 파동성문이 2개(Pl파와 P2파)로 한정되어 있다. 이 논문에서는 이와 같은 제한을 없애고 임의 개수의 파동성분을 고려할 수 있도록 하는 정식화 과정을 제안하였다. 구조물을 포함하는 근역은 유한요소로 나타내며 원역은 평행층상 반무한 지반으로 가정하였다. 제안된 무한요소의 타당성은 1차원 및 2차원 파동전달문제를 해석하고 이를 이론해 및 정밀수지해석 해와 비교하여 검증하였다.