• 한국지반환경공학회 논문집
• /
• 제11권5호
• /
• pp.53-60
• /
• 2010

불포화토의 역학적 성질을 규명하기 위한 가장 기본적인 요소인 함수특성곡선을 연구하기 위하여 대구 팔공산 지역의 화강풍화토를 대상으로 함수특성곡선시험을 수행하였다. 기존의 함수특성곡선 실험은 상재하중과 체적변형의 고려없이 실시하였지만, 본실험은 두요소를 고려하기 위하여 기존의 실험장비인 압력판 추출기를 개량하여 함수특성곡선 실험을 실시하였다. 시험과정에 있어 상재하중은 0, 25, 50, 75, 100kPa을 가하였으며, 체적변형은 각 단계마다 측정하였다. 본 실험의 시료를 통한 함수특성곡선 실험 결과는 상재하중의 증가에 따라 동일한 모관흡수력에서 낮은 체적함수비를 가졌으며, 공기함입치는 증가하였다. 또한 전이영역 구간의 기울기는 감소하는 결과를 나타내었으며 이력현상은 줄어드는 결과를 보였다. 포화도는 상재하중의 증가에 따라 동일한 흡수력에서 큰 값을 나타내었으며 건조과정보다는 습윤과정이 큰 값을 나타내었다. 체적변화를 고려한 함수특성곡선은 미고려한 함수특성곡선보다 미세하게 큰 값을 나타낸다. 본 실험의 실측치와 Fredlund와 Xing(1994)의 이론식은 잘 부합하는 결과를 나타내었으며, 상수값 a, n, m값은 상재하중에 따라 기존의 연구결과와 비슷한 양상을 보였다.

• The Korean Journal of Ecology
• /
• 제27권1호
• /
• pp.27-33
• /
• 2004

Cryptomeria japonica plantation was monitored every year during 15 years from 1983 to 1997 for stem diameter and volume. The reciprocal equation, 1/Y = A + B/N, was applied to the relationship between cumulative volume Y and cumulative number N from the largest tree in the stand each year. The parameters A and B, which means respectively the reciprocal of an asymptotic value of total stand stem volume and the reciprocal of the maximum stem volume, are related by a power function. The power functional relationship between A and B derived a linear relationship of B-points ( $N_{B}$, $V_{B}$; $N_{B}$ = B/A, $Y_{B}$ = 1/2A) of each Y-N curve on log-log coordinates. The gradient of B-point line was so steep that the Y-N curve moved parallel upward year by year. The time trajectory of mean stem volume (W) and density ($\rho$) provided evidence in favor of the 3/2 power law of self-thinning, because the gradient of W - $\rho$ trajectory on log-log coordinates approximated to -3/2 at the final stage of stand development. On the basis of the results of Y-N curves and W - $\rho$ trajectory, the time trajectory of maximum stem volume $W_{max obs}$ and $\rho$ was derived theoretically. The gradient of $W_{max obs}$ - $\rho$ trajectory on log-log coordinates is calculated to be -0.6105 at the final stage. The gradient of $W_{max obs}$ - $\rho$ trajectory was steeper than that of W - $\rho$ trajectory at the early stage, while the former is gentler than the latter at the later stage.stage.e.age.e.

• 산업경영시스템학회지
• /
• 제5권6호
• /
• pp.69-78
• /
• 1982

Traditional CVP (Cost-Volume-Profit) analysis employs linear cost and revenue functions within some specified time period and range of operations. Therefore CVP analysis is assumption of constant labor productivity. The use of linear cost functions implicity assumes, among other things, that firm's labor force is either a homogenous group or a collection homogenous subgroups in a constant mix, and that total production changes in a linear fashion through appropriate increase or decrease of seemingly interchangeable labor unit. But productivity rates in many firms are known to change with additional manufacturing experience in employee skill. Learning curve is intended to subsume the effects of all these resources of productivity. This learning phenomenon is quantifiable in the form of a learning curve, or manufacturing progress function. The purpose d this study is to show how alternative assumptions regarding a firm's labor force may be utilize by integrating conventional CVP analysis with learning curve theory, Explicit consideration of the effect of learning should substantially enrich CVP analysis and improve its use as a tool for planning and control of industry.

• 한국게임학회 논문지
• /
• 제9권6호
• /
• pp.191-196
• /
• 2009

볼륨 렌더링은 볼륨 데이터로부터 유용한 정보를 추출하여 시각화 하는 방법이다. 일반적으로 볼륨 렌더링에서 사용하는 데이터가 크기 때문에 실시간 처리가 가능한 수준의 빠른 렌더링을 위한 가속기법들이 중요하다. 최대-최소 8진트리는 고속 볼륨 렌더링을 위한 자료구조이지만, 볼륨데이터가 클수록 생성시간이 오래 걸리는 문제가 있다. 본 논문에서는 CUDA를 이용하여 GPU에서 최대-최소 8진트리의 생성을 가속화 하는 방법을 제안한다. 먼저 볼륨데이터에 Space Filling Curve를 적용하여 3차원의 데이터를 연속적인 1차원 배열형태로 변환한다. 이렇게 변환된 데이터로부터 최대-최소 8진트리 자료구조를 만들어 빈공간 도약기법에 적용함으로써 렌더링 속도를 향상시킬 수 있다.

• Journal of Gastric Cancer
• /
• 제18권2호
• /
• pp.172-181
• /
• 2018

Purpose: This study aimed to evaluate the surgical outcomes and investigate the feasibility of reduced-port laparoscopic gastrectomy using learning curve analysis in a small-volume center. Materials and Methods: We reviewed 269 patients who underwent laparoscopic distal gastrectomy (LDG) for gastric carcinoma between 2012 and 2017. Among them, 159 patients underwent reduced-port laparoscopic gastrectomy. The cumulative sum technique was used for quantitative assessment of the learning curve. Results: There were no statistically significant differences in the baseline characteristics of patients who underwent conventional and reduced-port LDG, and the operative time did not significantly differ between the groups. However, the amount of intraoperative bleeding was significantly lower in the reduced-port laparoscopic gastrectomy group (56.3 vs. 48.2 mL; P<0.001). There were no significant differences between the groups in terms of the first flatus time or length of hospital stay. Neither the incidence nor the severity of the complications significantly differed between the groups. The slope of the cumulative sum curve indicates the trend of learning performance. After 33 operations, the slope gently stabilized, which was regarded as the breakpoint of the learning curve. Conclusions: The surgical outcomes of reduced-port laparoscopic gastrectomy were comparable to those of conventional laparoscopic gastrectomy, suggesting that transition from conventional to reduced-port laparoscopic gastrectomy is feasible and safe, with a relatively short learning curve, in a small-volume center.

• Journal of Magnetics
• /
• 제16권2호
• /
• pp.129-133
• /
• 2011

This paper shows the entire future market volume of the HTS power industry, one of main smart grid equipment, in the case of the final market penetration ratio reaching 100% in the domestic market (South Korea). In this paper, the market penetration ratio is determined using the judgment method, with the market penetration S-curve induced using the Delphi method and the Product Life Cycle from 2011 (supposed launching year, not realistic physical year), to 2050 (expected final target year). This paper analyzes the HTS market penetration ratio of each stage, apparent innovation, early adapters, and the early/late majority and laggard stage, using the S-curve, thus calculating the total future market volume of HTS equipment in the positive sense. Finally, this paper estimates the quantitative analysis results for the HTS4-items (cable, FCL, transformer, rotation machine) of each year within the domestic market.

• Steel and Composite Structures
• /
• 제7권5호
• /
• pp.355-376
• /
• 2007

The purpose of this study is to predict and investigate the time-dependent creep behavior of composite materials. For this, firstly the evaluation method for the modulus of elasticity of whole fiber and matrix is presented from the limited information on fiber volume fraction using the singular value decomposition method. Then, the effects of fiber volume fraction on modulus of elasticity of GFRP are verified. Also, as a creep model, the nonlinear curve fitting method based on the Marquardt algorithm is proposed. Using the existing Findley's power creep model and the proposed creep model, the effect of fiber volume fraction on the nonlinear creep behavior of composite materials is verified. Then, for the time-dependent analysis of a composite material subjected to uniaxial tension and simple shear loadings, a user-provided subroutine UMAT is developed to run within ABAQUS. Finally, the creep behavior of center loaded beam structure is investigated using the Hermitian beam elements with shear deformation effect and with time-dependent elastic and shear moduli.

• 한국항만경제학회지
• /
• 제27권3호
• /
• pp.1-12
• /
• 2011

본 논문은 금융위기 이후 대중 수출증가가 경기회복에 주도적 역할을 하고, 우리경제의 중국경제 의존도가 크게 상승하는 상황에서 J-curve 효과가 우리나라 대중국 항만 수출입 흐름에 적용되는가를 월별자료를 이용하여 2000년부터 2010년까지의 기간에 대해 실증분석 하였다. 오차수정모형을 추정한 결과 단기적인 조정역할은 실질실효환율이 수행하는 것으로 나타났으며, 분산분해 결과 대중국 항만 무역수지에 대한 영향력이 국내경기보다 실질실효 환율과 세계경기가 더 크게 나타남을 알 수 있었다. 이와 더불어 수준변수로 구성된 VAR과 오차수정항을 포함한 VECM을 이용한 충격반응 분석을 실시한 결과 대중국 항만 무역수지는 환율 충격에 대하여 시차를 두고 반응을 보이는 것으로 나타나 J-curve 효과가 존재함을 알 수 있었다.

• 한국물환경학회지
• /
• 제27권1호
• /
• pp.9-18
• /
• 2011

In this study the optimal volume for non-point source control retention is estimated considering spatio-temporal variation of land surface. The 3-parameter mixed exponential probability density function is used to represent the statistical properties of rainfall events, and NRCS-CN method is applied as rainfall-runoff transformation. The catchment drainage area is divided into individual $30m{\times}30m$ cells, and runoff curve number is estimated at each cell. Using the derived probability density function theory, the stormwater probability density function at each cell is derived from the rainfall probability density function and NRCS-CN rainfall-runoff transformation. Considering the antecedent soil moisture condition at each cell and the spatial variation of CN value at the whole catchment drainage area, the ensemble stormwater capture curve is established to estimate the optimal volume for an non-point source control retention. The comparison between spatio-temporally varied land surface and constant land surface is presented as a case study for a urban drainage area.

• 한국산림과학회지
• /
• 제3권1호
• /
• pp.28-31
• /
• 1963

Recognizing shortcomings and unreasonable points of the usual methods of measurement of the standing-tree volume, author contrived measurement formula of standing-tree volume which is based on stem-curve equation, $y^2=2px$, resulted from the analysises and experiments on stem-curve by differentiation & integration. The results of this study are as follows ; (1) The following is the formula. $V=1/2g_{1.2}$(h+1.2) V=volume of tree $g_{1.2}$ = sectional area at breast heigh h = height of tree (2) So plain is the form of this formula that this formula is more convenient than usual formulas in measuring. (3) The percentage error of this formula is negative and it is remarkably superior to usual formulas except Pressler's formula, in other words, the higher the tree that is measured is, the more inaccurate become pressler's formula, and the percentage error of the breast-height form factor method is direct proportion to the grossness of the tree that is measured, but the higher the tree that is measured, the lower become percentage error of this formula in geometrical progression.