• Korean Journal of Radiology
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• 제21권5호
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• pp.550-560
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• 2020

Objective: To evaluate the interobserver agreement, diagnostic value, and associated clinical factors of automated breast ultrasound (ABUS) coronal features in differentiating breast lesions. Materials and Methods: This study enrolled 457 pathologically confirmed lesions in 387 female (age, 46.4 ± 10.3 years), including 377 masses and 80 non-mass lesions (NMLs). The unique coronal features, including retraction phenomenon, hyper- or hypoechoic rim (continuous or discontinuous), skipping sign, and white wall sign, were defined and recorded. The interobserver agreement on image type and coronal features was evaluated. Furthermore, clinical factors, including the lesion size, distance to the nipple or skin, palpability, and the histological grade were analyzed. Results: Among the 457 lesions, 296 were malignant and 161 were benign. The overall interobserver agreement for image type and all coronal features was moderate to good. For masses, the retraction phenomenon was significantly associated with malignancies (p < 0.001) and more frequently presented in small and superficial invasive carcinomas with a low histological grade (p = 0.027, 0.002, and < 0.001, respectively). Furthermore, continuous hyper- or hypoechoic rims were predictive of benign masses (p < 0.001), whereas discontinuous rims were predictive of malignancies (p < 0.001). A hyperechoic rim was more commonly detected in masses more distant from the nipple (p = 0.027), and a hypoechoic rim was more frequently found in large superficial masses (p < 0.001 for both). For NMLs, the skipping sign was a predictor of malignancies (p = 0.040). Conclusion: The coronal plane of ABUS may provide useful diagnostic value for breast lesions.

• 한국전산구조공학회논문집
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• 제24권3호
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• pp.275-281
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• 2011

일반적으로 인장 시험에 주로 사용되는 납작한 형태의 금속 재료에 천천히 인장력을 가하고 그 힘을 증가시키면 어느 순간에 루더스 밴드(Luders band)라고 불리는 소성 변형의 띠가 갑자기 발생한다. 이 띠들은 일정 각도를 가지고 평행하게 발생하며, 여러 연구자들에 의해 특정 경계조건에 대하여 이 띠가 발생하는 조건과 그 각도에 대한 많은 연구가 선행되어 왔다. 본 연구에서는 평면 응력 조건에서 이루어진 Thomas(1961)의 연구를 기반으로 하고 $J_2$ 소성 변형 조건, 힘의 평형방정식, 그리고 구성방정식을 이용하여 평면 변형 조건에서 발생하는 밴드의 각도를 해석적으로 유도하였다. 이 결과는 음향텐서를 이용한 기존의 연구 결과와 일치함을 확인하였다.

• Geomechanics and Engineering
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• 제11권4호
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• pp.457-469
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• 2016

Steep rock slope with water-filled tension crack will happen to overturn around the toe of the slope under seismic loading. This failure type is completely different from the common toppling failure occurring in anti-dipping layered rock mass slopes with steeply dipping discontinuities. This paper presents an analytical approach to determine the seismic factor of safety against overturning for an intact rock mass slope with water-filled tension crack considering horizontal and vertical seismic coefficients. This solution is a generalized explicit expression and is derived using the moment equilibrium approach. A numerical program based on discontinuous deformation analysis (DDA) is adopted to validate the analytical results. The parametric study is carried out to adequately investigate the effect of horizontal and vertical seismic coefficients on the overall stability against overturning for a saturated rock slope under two water pressure modes. The analytical results show that vertically upward seismic inertia force or/and second water pressure distribution mode will remarkably decrease the slope stability against overturning. Finally, several representative design charts of slopes also are presented for the practical application.

• Structural Engineering and Mechanics
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• 제15권3호
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• pp.331-344
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• 2003

The plane contact problem for two infinite elastic layers whose elastic constants and heights are different is considered. The layers lying on a Winkler foundation are acted upon by symmetrical distributed loads whose lengths are 2a applied to the upper layer and uniform vertical body forces due to the effect of gravity in the layers. It is assumed that the contact between two elastic layers is frictionless and that only compressive normal tractions can be transmitted through the interface. The contact along the interface will be continuous if the value of the load factor, ${\lambda}$, is less than a critical value. However, interface separation takes place if it exceeds this critical value. First, the problem of continuous contact is solved and the value of the critical load factor, ${\lambda}_{cr}$, is determined. Then, the discontinuous contact problem is formulated in terms of a singular integral equation. Numerical solutions for contact stress distribution, the size of the separation areas, critical load factor and separation distance, and vertical displacement in the separation zone are given for various dimensionless quantities and distributed loads.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.833-841
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• 2008

Recently, the upheaval generation in the road which is under service had been reported. Due to the upheaval generation, total 4 lanes were forced to curtail to 3 lanes, and traffic was delayed. In normal situation of cut-slopes in korea, that condition is hard to detect since most cut-slopes contain discontinuous material, that is rock. Common collapses in rock-slopes is wedge failure, plane failure and toppling failure which is all individual mechanism of discontinuous rock mass. In contrast, such upheaval in the road in front of cut-slope can be generated only when circular movement is triggered within the cut-slope. In this sense, rock-slopes barely show any kind of movement in the road locates at the front of them. Numerical analysis is general method in simulation of slope displacement and evaluation of safety. However, numerical analysis programs which are related with rock-slopes are not able to simulate such upheaval movement because that programs are based on discontinuous modeling mechanism. In addition, although numerical analysis programs which are based on FEM/FDM and thus utilize continuous modeling mechanism are able to simulate circular movement and upheaval situation, they have weakness in reflecting discontinuities of rock-slope itself. In this study, detailed in-site investigation and numerical analysis based on in-site condition were performed in order to expect upheaval movement in the road. In this procedure, the FLAC program which uses continuous modeling method was utilized, and new approach reflecting discontinuity developed toward the road with a ubiquitous joint model was tried to derive reliable analysis result.

• 지질공학
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• 제2권1호
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• pp.1-18
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• 1992

불연속면을 갖는 암체는 거의 대부분 조도를 가지고, 이 조도는 전단강도에 영향을 크게 미치므로 불연속면을 갖는 화강암류(15개), 편마암류(7개), 안산암류(1개) 등을 연구대상으로 하여 전단마찰각(${\Phi}_p$), 조도의 한계응력(${\sigma}_r$) 및 전단파괴강도(${\tau}$_o)를 도출하여 불연속면에 있어서의 전단강도($\tau$)를 규명한 것이다. 1. 조도는 단계전단력에 따라 마찰각은 ${\Phi}_i=38.03^{\circ}$에서 $33.21^{\circ}$로 감소하고 있다. 즉 초기때가 가장 높고, 말기때가 가장 낮다. 2. 조도각(i)의 한계는 $45^{\circ}$ 이내 (시험치:$43^{\circ}$)에 분포하고, 절리조도계수(JRC)는 14를 넘지않으며, $JRC=-4.63{\;}Ln{\sigma}n+5.63$을 경계로한 분포 범위에 있다. 3. 조도한계응력 ${\sigma}_T$는 0.1-3.65Mpa일때 전단파괴강도 ${\tau}_o$는 0.01-0.46Mpa가 되고, 이들 불연속면의 전단강도 $\tau$는 3.65-39.11Mpa로 되어 있어서 만일 이 이상의 하중이 가해 졌을때 그 암체는 붕괴 및 활동이 일어날 것이다.

• 비파괴검사학회지
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• 제30권5호
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• pp.423-428
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• 2010

본 논문에서는 ESPI 방법을 이용하여 자동차 엔진의 핵심 부품인 TPS의 열변형력에 따른 변외변형을 측정하여 열변형 특성을 분석하였다. 높은 해상도의 CCD와 줌렌즈를 사용하여 부품의 검사영역을 가로 세로 각각 5cm로 최소화하였다. 주행거리가 다른 TPS 부품들을 4-step 위상이동법과 위상 연속화를 통해 변형량이 연속적으로 변하는 위상도를 얻었고, 3차원으로 변형의 모양과 크기를 나타내었다. 약 $70^{\circ}C$의 온도를 유지하면서 TPS 부품에 열을 가한 경우 주행거리가 길어질수록 TPS 변형은 크게 측정되었고, 위로 볼록한 형태로 변형되었다. 그리고 내부결함이 있는 부품에서는 위상도에 불연속적인 무늬가 나타났고, 아래로 오목한 모양을 갖는 변형으로 나타났다.

• 한국주거학회논문집
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• 제23권1호
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• pp.27-41
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• 2012

The objective of this study is to develop the blind control strategy and method which reduce negative effect of incoming daylight on visual comfort of occupants, minimize psychological anxieties caused by frequent motions of a blind, and maximize positive effect of incoming daylight and solar irradiation by opening/closing of a blind. As previous researches on blind controls have limited outdoor environmental conditions to those in specific regions, orientations and dates, these resulted in problems at various conditions for general-purpose application. Major problem is that the time interval and amount of blind movement do not meet the control objective at the end of control zone and discontinuous curve. To overcome these limitations revealed in the previous researches, following tasks were performed in this study. 1) To establish the control objective to accomplish the goal of this study. 2) To develop the control methods and algorithms which prevent glare on the work-plane at any time and which control the time interval and amount of blind movement to follow the control objective at various profile angle curves. 3) To validate the general-purpose applicability and performance of the developed control methods and algorithms by simulation and its data analysis at various conditions. It was found that the proposed methods and algorithms can prevent the direct glare on the work-plane at all the time and also increase the incoming daylight and solar irradiation.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.296-303
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• 2000

The purpose of this study is to find inelastic behavior and ductility capacity of reinforced concrete bridge columns under earthquake. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. In boundary plane at which each member with different thickness is connected, due to the abrupt change in their stiffness local discontinuous deformation can be taken into account by introducing interface element. Also an analytical model is developed to express the confining effects of lateral tie which depend on the existence or nonexistence and the amounts of transverse confinement, etc. The proposed numerical method for inelastic behavior and ductility capacity of reinforced concrete bridge columns will be verified by comparison with reliable experimental results.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 사면안정학술발표회
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• pp.119-127
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• 2003

For the calculation of internal stability, the hypothesis in conventional design is on the basis of two distinct zones, which are‘active zone’and‘passive zone’. This means that there is an abrupt discontinuous transition from active to passive states across a potential failure line. The existence of a discontinuity of this nature appears physically unreasonable, especially from kinematic considerations. A series of pull-out model tests was undertaken from a wall being rotated about the toe to find the strain distribution mobilized from near the wall face into the deep, stable zone through the centre plane. With this finding of transition zone, the objective of study is aiming at identifying the likely effect of this zone in designing method by comparing with the prevailing design method.