• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.732-739
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• 2009

Flow phantom with stenosis was manufactured using an auto-injector to obtain angiostenotic flow information and quality assurance (QA) for ultrasound diagnostic instrumentation. Effectiveness of manufactured flow phantom with stenosis was investigated with power Doppler that was known to have diagnostic efficiency for angiostenosis. The flow phantom with stenosis was manufactured to 70% stenosis with 8 mm and 2.4 mm silicon tube, and silicone tube was covered with gelatin that has acoustic characteristics similar to soft tissue. When the linear transducer was used for measurement, the estimated diameter of normal vessel was measured lower than that of normal value, and the estimated diameter of stenosed vessel was measured higher than that of normal value. The measured parameters were not affected except for the radical conditions such as gain of 60%, PRF of 3000 Hz, use of maximal filter or angle. In addition, when the convex transducer was used for measurement, measurement parameters were affected by gain, PRF, filter, and angle. Therefore it is expected that flow phantom with stenosis manufactured with an auto-injector will be utilized effectively for QA of angiostenotic diagnosis.

• Korean Journal of Radiology
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• v.24 no.9
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• pp.849-859
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• 2023

Objective: The prognostic value of the volume and density of skeletal muscles in the abdominal waist of patients with colon cancer remains unclear. This study aimed to investigate the association between the automated computed tomography (CT)-based volume and density of the muscle in the abdominal waist and survival outcomes in patients with colon cancer. Materials and Methods: We retrospectively evaluated 474 patients with colon cancer who underwent surgery with curative intent between January 2010 and October 2017. Volumetric skeletal muscle index and muscular density were measured at the abdominal waist using artificial intelligence (AI)-based volumetric segmentation of body composition on preoperative pre-contrast CT images. Patients were grouped based on their skeletal muscle index (sarcopenia vs. not) and muscular density (myosteatosis vs. not) values and combinations (normal, sarcopenia alone, myosteatosis alone, and combined sarcopenia and myosteatosis). Postsurgical disease-free survival (DFS) and overall survival (OS) were analyzed using univariable and multivariable analyses, including multivariable Cox proportional hazard regression. Results: Univariable analysis showed that DFS and OS were significantly worse for the sarcopenia group than for the non-sarcopenia group (P = 0.044 and P = 0.003, respectively, by log-rank test) and for the myosteatosis group than for the non-myosteatosis group (P < 0.001 by log-rank test for all). In the multivariable analysis, the myosteatotic muscle type was associated with worse DFS (adjusted hazard ratio [aHR], 1.89 [95% confidence interval, 1.25-2.86]; P = 0.003) and OS (aHR, 1.90 [95% confidence interval, 1.84-3.04]; P = 0.008) than the normal muscle type. The combined muscle type showed worse OS than the normal muscle type (aHR, 1.95 [95% confidence interval, 1.08-3.54]; P = 0.027). Conclusion: Preoperative volumetric sarcopenia and myosteatosis, automatically assessed from pre-contrast CT scans using AI-based software, adversely affect survival outcomes in patients with colon cancer.

• Journal of Nutrition and Health
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• v.7 no.4
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• pp.33-37
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• 1974

Changes in the concentration of total protein, albumin, ${\alpha}_1-,{\alpha}_2-,{\beta}-,$ and ${\gamma}-globulin$ in Serum from 138 healthy, normal pregnant woman were studied by the method of cellulose-acetate electrophoresis. 1. The concentration of total serum protein decreased gradually during the first 7 month, and showed a tendency to increase thereafter. 2. The concentration of serum albumin showed a steady continuous fall untill term. 3. During pregnancy,${\alpha}_1$ and ${\beta}-globulin$ value rose, ${\gamma}-globulin$ value fell and ${\alpha}_2-globulin$ value showed no significant change.

• Journal of the Korean Data and Information Science Society
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• v.27 no.6
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• pp.1661-1671
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• 2016

Risk analysis is a systematic study of uncertainties and risks we encounter in business, engineering, public policy, and many other areas. Value at Risk (VaR) is one of the most widely used risk measurements in risk management. In this paper, the Korean Composite Stock Price Index data has been utilized to model the VaR employing the classical ARMA (1,1)-GARCH (1,1) models with normal, t, generalized hyperbolic, and generalized pareto distributed errors. The aim of this paper is to compare the performance of each model in estimating the VaR. The performance of models were compared in terms of the number of VaR violations and Kupiec exceedance test. The GARCH-GPD likelihood ratio unconditional test statistic has been found to have the smallest value among the models.

• Journal of the Korean Statistical Society
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• v.33 no.2
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• pp.245-254
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• 2004

This paper derives a distribution function of the terminal value and running maximum of two-dimensional Brownian motion {X($\tau$) = (X$_1$($\tau$), X$_2$ ($\tau$))', $\tau$ 〉0}. One random variable of the joint distribution is the terminal time value, X$_1$ (T). The other random variable is the maximum of the Brownian motion {X$_2$($\tau$), $\tau$〉} between time s and time t. With this distribution function, this paper also derives an explicit pricing formula for an outside barrier option whose monitoring period starts at an arbitrary date and ends at another arbitrary date before maturity.

• Bulletin of the Korean Mathematical Society
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• v.47 no.1
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• pp.81-87
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• 2010

In this paper, we consider the existence of nontrivial solutions for the nonlinear fractional differential equation boundary-value problem(BVP) $-D_0^{\alpha}+u(t)=\lambda[f(t, u(t))+q(t)]$, 0 < t < 1 u(0) = u(1) = 0, where $\lambda$ > 0 is a parameter, 1 < $\alpha$ $\leq$ 2, $D_{0+}^{\alpha}$ is the standard Riemann-Liouville differentiation, f : [0, 1] ${\times}{\mathbb{R}}{\rightarrow}{\mathbb{R}}$ is continuous, and q(t) : (0, 1) $\rightarrow$ [0, $+\infty$] is Lebesgue integrable. We obtain serval sufficient conditions of the existence and uniqueness of nontrivial solution of BVP when $\lambda$ in some interval. Our approach is based on Leray-Schauder nonlinear alternative. Particularly, we do not use the nonnegative assumption and monotonicity which was essential for the technique used in almost all existed literature on f.

• Transactions of Materials Processing
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• v.19 no.7
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• pp.393-398
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• 2010

This paper investigates the effect of material properties on the formability of sheet metals based on the Marciniak-Kuczynski model (M-K model). The hardening behavior of the material is modeled as the Hollomon model with the strain rate effect. The yield surfaces are constructed with Hosford79 yield function. The material properties considered in this study include the R-value, the strain hardening exponent, the strain rate hardening exponent, and the crystal structure of the material. The effect of the crystal structure on formability is roughly expressed as the change of the yield surface by varying the value of the exponent in Hosford79 yield function. Results show that the R-value affects neither the magnitude nor the shape of right hand side of forming limit diagrams (FLDs). Higher strain hardening exponent and higher strain rate hardening exponent improve the formability of sheet metals because they stabilize the forming processes.

• Economic and Environmental Geology
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• v.33 no.4
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• pp.309-320
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• 2000

Aperture is an important parameter for determining the hydraulic characteristics of fractured media. In this study the topography of artificial rock joint surface was measured using 3D laser profilometer to analyze the aperture distribution. The initial aperture distribution was determined when the contact area became one percent of total joint surface. The initial aperture distribution of granite joint, with the mean value of 0.78 mm and the standard deviation of 0.34 mm was much different from that of the marble joint, with the mean value of 0.57 mm and the standard deviation of 0.26 mm. Apertures of both granite and marble showed normal distributions. Aperture distribution with the contact area of 25% was also analyzed. Mean value was decreased to one third compared to the initial aperture, but the standard deviation was decreased slightly. To determine the spatial correlation of the aperture distribution variogram analysis was carried out on the initial aperture data. Most experimental variograms were fitted well with exponential model. It is expected that the measured aperture characteristics can be used for stochastic analysis of fluid flow through rock joints.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.42-43
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• 2015

This study has analyze the suitable area of slump and slump flow among the fluidity evaluation of concrete by measuring slum and slump flow variation according to unit quantity and fine aggregate percentage in a low W/C mix. The fluidity of concrete can be expressed well with the slump value when sump value is 122mm or less. On the other hand, the fluidity of concrete can be expressed more accurately with slump flow value when slump is 122mm or greater.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.83-83
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• 2002

목적： 현재 임상적으로 사용되고 있는 확산경사자장의 세기 이상( > 1200)의 강한 확산 경사자장이 가해진 경우 뇌구조물들의 확산계수값을 조사하고 고자장(Bo = 3T)에서 이러한 강한 확산 경사자장을 이용하는 경우 1.5T에서 시행하는 경우와의 차이점을 비교 연구해보고자 하였다. 대상 및 방법： 정상 성인 3명을 대상으로 b-value를 0부터 3500까지 변화시키며 확산강조영상을 최대경사자장 40 mT/m, slew rate 150 T/m/s의 경사자장계가 장착된 3T MR scanner (General Electric, USA)에서 획득하였다. 사용한 펄스열은 Stejskal-Tanner type의 확산강조 경사자장이 포함된 single-shot SE EPI를 사용하였으며 영상획득시 사용한 파라미터는 다음과 같다. TR/TE= 10000/95.1, Thickness/space=512mm, FOV=24$\times$21cm, Matrix=128$\times$128, NEX=1 뇌구조물들에 관심 영역을 설정하고 b-value에 따른 신호감소를 측정하였다. 측정된 데이터를 hi-exponential decay 모델을 이용하여 분석하였다.