• Archives of Plastic Surgery
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• 제46권2호
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• pp.135-139
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• 2019

Background In immediate breast reconstruction using an extended latissimus dorsi musculocutaneous (eLDMC) flap, the volume of the flap decreases, which causes a secondary deformity of the breast shape. Since little research has investigated this decrease in muscle volume, the authors conducted an objective study to characterize the decrease in muscle volume after breast reconstruction using an eLDMC flap. Methods Research was conducted from October 2011 to November 2016. The subjects included 23 patients who underwent mastectomy due to breast cancer, received immediate reconstruction using an eLDMC flap without any adjuvant chemotherapy or radiotherapy, and received a computed tomography (CT) scan from days 7 to 10 after surgery and 6 to 8 months postoperatively. In 10 patients, an additional CT scan was conducted 18 months postoperatively. Axial CT scans were utilized to measure the volumetric change of the latissimus dorsi muscle during the follow-up period. Results In the 23 patients, an average decrease of 54.5% was observed in the latissimus dorsi muscle volume between the images obtained immediately postoperatively and the scans obtained 6 to 8 months after surgery. Ten patients showed an average additional decrease of 11.9% from 6-8 months to 18 months after surgery. Conclusions We studied changes in the volume of the latissimus dorsi muscle after surgery using an eLDMC flap performed after a mastectomy without adjuvant chemotherapy or radiotherapy. In this study, we found that immediate breast reconstruction using a latissimus dorsi muscle flap led to a decrease in muscle volume of up to 50%.

• Imaging Science in Dentistry
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• 제53권2호
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• pp.153-159
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• 2023

Purpose: The objective of this study was to assess the fractal dimension, lacunarity, trabecular microarchitecture parameters, and cortical linear measurements in the mandibles of male and female individuals to identify differences between them. Materials and Methods: In total, 116 cone-beam computed tomography scans of healthy individuals of different ages (57 men and 59 women, aged between 20 and 60 years) were selected. The following bone parameters were measured: 1) buccal, lingual, and basal cortical bone thickness in 5 standard parasagittal sections (the midline, the left and right sides of the lower lateral incisors, and the left and right sides of the lower canines); 2) the bone volume fraction of 10 sequential axial sections from each patient by creating a volume of interest in the area between the lower canines; and 3) fractal dimension and lacunarity using grayscale images of the same region of the volume of interest in the anterior mandible. Spearman correlation coefficients and the Mann-Whitney test were used. Results: A significant and positive correlation was found between age and cortical thickness, especially in the region of the central incisors. Significant differences between sexes in terms of fractal dimension, lacunarity, and bone volume were found. Women revealed lower fractal dimension values and higher lacunarity and bone volume ratio values than men. Conclusion: Fractal dimension, lacunarity, trabecular bone volume, and cortical thickness were different between men and women of different ages.

• 한국전산구조공학회논문집
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• 제20권5호
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• pp.581-592
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• 2007

이 논문은 일정체적 캔틸레버 기둥의 정확탄성곡선(elastica)에 관한 연구이다. 기둥의 자유단에 압축하중과 모멘트 하중으로 구성되는 조합하중이 작용하는 캔틸레버 기둥의 정확탄성곡선을 지배하는 비선형 미분방정식과 경계조건을 유도하였다. 미분방정식에는 전단변형효과를 고려하였다. 기둥의 변단면으로는 정다각형 단면을 갖는 선형, 포물선형 및 정현의 변단면을 채택하였다. 기둥의 정확탄성곡선을 해석하기 위하여 유도된 미분방정식을 수치해석하였다. 수치해석의 결과를 이용하여 기둥의 무차원 변수들이 정확탄성곡선에 미치는 영향을 분석하였다. 실험실 규모의 실험을 실시하여 이 연구에서 얻어진 수치해석의 결과를 검증하였다.

• 한국강구조학회 논문집
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• 제9권2호통권31호
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• pp.221-228
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• 1997

이 논문은 일정체적 단순지지 보-기둥의 동적 최적단면의 결정에 관한 연구이다. 정다각형 단면의 단면깊이가 포물선으로 변화하는 보-기둥에 대한 자유진동을 지배하는 상미분방정식을 유도하였다. 이 미분방정식에는 축하중효과를 고려하였고, Runge-Kutta method와 Regula-Falsi method를 이용하여 미분방정식을 수치적분하고 고유진동수를 산출하였다. 수치해석 결과로부터 얻어진 진동수-단면비 곡선의 임계값들을 분석하여 동적 최적단면을 결정하고 이 결과들을 표 및 그림에 나타내었다.

• 전산구조공학
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• 제9권3호
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• pp.135-143
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• 1996

일정체적의 원형단면을 갖는 변단면 보-기둥의 자유진동 및 좌굴하중을 지배하는 미분방정식을 유도하고 이를 수치해석하였다. 미분방정식에는 축하중효과를 고려하였다. 원형단면의 반경변화는 포물선식을 채택하였고, 고정-고정, 고정-회전 및 회전-회전 보-기둥의 고유진동수 및 좌굴하중을 산출하였다. 수치해석의 결과로 무차원 고유진동수와 무차원 변수들 사이의 관계 및 무차원 좌굴하중과 단면비 사이의 관계를 그림에 나타내었고, 최강기둥의 단면비와 좌굴하중을 구하였다.

• Smart Structures and Systems
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• 제30권2호
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• pp.135-143
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• 2022

The object of this paper is to investigate the free vibration behavior under the effect of carbon nanotube distribution in functionally graded carbon nanotube-reinforced composite (FG-CNTRC) by using higher-order shear deformation theories. In this work, we present a novel distribution method for carbon nanotubes in the polymer matrix by using a new exponential power law distribution of carbon nanotube volume fraction. It is assumed that the SWCNTs are aligned along the beam axial direction and the distribution of the SWCNTs may vary through the thickness of the beam with different patterns of reinforcement. The rule of mixtures is used in order to obtain material properties of the CNTRC beams. Hamilton's principle is used in deriving the equations of motion. The validity of the free Vibration results is examined by comparing them with those of the known data in the literature. The results that obtained indicate that the carbon nanotube volume fraction distribution play a very important role on the free vibrations characteristics of the CNTRC beam.

• Geomechanics and Engineering
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• 제33권5호
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• pp.463-475
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• 2023

Tunnel construction activity, conducted mainly in mountains and within urban centres, causes soil settlement, thus requiring the relevant management of slopes and structures as well as evaluations of risk and stability. Accordingly, in this study we performed a three-dimensional finite element analysis to examine the behaviour of piles and pile cap stability when a tunnel passes near the bottom of the foundation of a pile group connected by a pile cap. We examined the results via numerical analysis considering different conditions for reinforcement of the ground between the tunnel and the pile foundation. The numerical analysis assessed the angular distortion of the pile cap, pile settlement, axial force, shear stress, relative displacement, and volume loss due to tunnel excavation, and pile cap stability was evaluated based on Son and Cording's evaluation criterion for damage to adjacent structures. The pile located closest to the tunnel under the condition of no ground reinforcement exhibited pile head settlement approximately 70% greater than that of the pile located farthest from the tunnel under the condition of greatest ground reinforcement. Additionally, pile head settlement was greatest when the largest volume loss occurred, being approximately 18% greater than pile head settlement under the condition having the smallest volume loss. This paper closely examines the main factors influencing the behaviour of a pile group connected by a pile cap for three ground reinforcement conditions and presents an evaluation of pile cap stability.

• 대한토목학회논문집
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• 제26권3A호
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• pp.533-538
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• 2006

이 논문은 단순지지된 변단면 기둥의 정적, 동적 안정해석에 관한 연구이다. 이 연구에서 기둥의 체적과 지간길이는 일정하다. 기둥의 단면은 정다각형 단면이고 단면깊이의 변화는 포물선형으로 채택하였다. 압축하중을 받는 이러한 기둥의 자유 진동을 지배하는 미분방정식과 경계조건을 무차원으로 유도하였다. 이 미분방정식을 수치해석하여 고유진동수와 진동형 및 좌굴하중을 산정하였다. 단면비와 고유진동수 및 좌굴하중의 관계를 분석하여 동적 최적단면비, 최적 고유진동수 및 최강기둥의 단면비 및 좌굴하중을 얻었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.393-396
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• 2002

Submerged gas-injected system can be applied to various industrial field such as metallurgical and chemical processes, So this study aims at presenting the relevant relationship between gas phase and liquid phase in a gas-injected bath. In a cylinderical bath, local gas volume fraction and bubble frequency were measured by electroconductivity probe and oscilloscope. The temperature of each phase was measured using thermocouple and data acquisition system. In vertical gas injection system, gas-liquid two phase plume was formed, being symmetry to the axial direction of injection nozzle and in a shape of con. Lacal gas-liquid flow becomes irregular around the injection nozzle due to kinetic energy of gas and the flow variables show radical change at the vicinity of gas(air) injection nozzle As most of the kinetic energy of gas was transferred to liquid in this region, liquid started to circulate. In this reason, this region was defined as 'developing flow region' The Bubble was taking a form of churn flow at the vicinity of nozzle. Sometimes smaller bubbles formed by the collapse of bubbles were observed. The gas injected into liquid bath lost its kinetic energy and then was governed by the effect of buoyancy. In this region the bubbles which lost their kinetic energy move upward with relatively uniform velocity and separate. Near the gas nozzle, gas concentration was the highest. But it started to decrease as the axial distance increased, showing a Gaussian distribution.

• Journal of Advanced Marine Engineering and Technology
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• 제37권8호
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• pp.807-815
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• 2013

대기압에서의 층류 에틸렌 확산 화염 내 매연 생성에 대하여 부력의 영향에 대한 보다 나은 이해를 위해 0g와 1g 조건하에서 수치해석을 수행하였다. 수치해석을 위하여 가스상 메커니즘과 열 및 이송특성을 이용하였다. 매연의 생성과 성장 및 산화에 대하여 예측하기 위하여 간단한 매연 모델이 채택되었으며 이 모델은 가스상과 매연의 화학적 상호작용에 고려되었다. 수치 결과로서 보다 두꺼운 확산층과 축방향 속도의 감소로 인해 0g에서의 화염이 1g하의 화염보다 더 넓은 화염을 가진다는 알 수 있었다. 0g에서의 축방향 속도의 감소는 더 긴 체류 시간을 가지게 하고 그 결과로 더 많은 매연 체적분율을 나타나게 한다. 0g 하에서는 화염이 부력으로 인한 불안정성이 없어져 화염의 흔들거림이 사라졌다.