• 한국물환경학회지
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• 제23권1호
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• pp.38-45
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• 2007

A one-dimensional kinematic wave model was used to calculate temporal and spatial changes of the highway runoff. Infiltration into pavement was considered using Darcy's law, as a function of flow depth and pavement hydraulic conductivity ($K_p$). The model equation was calculated using the method of characteristics (MOC), which provided stable solutions for the model equation. 22 storm events monitored in a highway runoff monitoring site in west Los Angeles in the U.S. were used for the model calculation and evaluation. Using three different values of $K_p$ ($5{\times}10^{-6}$, $10^{-5}$, and $2{\times}10^{-5}cm/sec$), total runoff volume and peak flow rate were calculated and then compared with the measured data for each storm event. According to the calculation results, $10^{-5}cm/sec$ was considered a site representative value of $K_p$. The study suggested a one-dimensional method to predict hydrodynamic behavior of highway runoff, which is required for the water quality prediction.

• International Journal of Aeronautical and Space Sciences
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• 제2권2호
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• pp.65-72
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• 2001

This paper demonstrates an explicit-implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for an existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory. Darcy's law is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full Newton-Raphson method is used for solving the nonlinear governing equations.

• 한국자동차공학회논문집
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• 제5권1호
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• pp.129-135
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• 1997

Previous studies has shown that the curve of low-cycle fatigue life was not expressed with the single line subjected to Manson-Coffin's law type and bent to short life in low ${\Delta}{\varepsilon}_p$ region. The main cause of this phenomenon has been considered that the localization of plastic strain in the crack initiation process fosters the crack initiation. In this study, the low-cycle fatigue life was investigated for each specimens omitted crack initiation process and it was found that fatigue life curve in log(${\Delta}{\varepsilon}_p$)-log($N_f$)was bent in low ${\Delta}{\varepsilon}_p$ region as ever. Therefore, the main cause of appearance of knee point in fatigue life curve is not found in the crack initiation process but in the crack propagation process. In the crack propagation process, the localization of the plastic strain in the vicinity of crack tip and the influence of test environment on the crack propagation rate were observed and these inclinations were more remarkable in low ${\Delta}{\varepsilon}_p$ region. Hence, it was concluded that these two phenomena in the crack propagation process were proved to the main cause which accelerates the crack propagation in low ${\Delta}{\varepsilon}_p$ region and bent the fatigue life curve in result.

• Agribusiness and Information Management
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• 제4권1호
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• pp.1-12
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• 2012

Cameroon, with her numerous resources, still depends on foreign aid while the rate of poverty remains high. Thus, even though historical evidence gives impetus to the impasse over role of developmental aid, from the top down approach through to development as a springboard raising states from the doldrums of poverty, it is still very difficult to draw a substantial relationship between developmental aid and poverty reduction. Against this backdrop of controversy, I find it apt to put Cameroon on a balance scale. Therefore, the purpose of this research is to critically assess the implications of developmental aid on poverty reduction and agro-rural development in Cameroon, using the RUMPI Area Development Project in the South West region of Cameroon as a case study. The study will situate and contextualize the top-down and bottom-up approaches to development within the basis of a Cameroonian perspective, using the Sachs-Easterly debate. The RUMPI Project was introduced with the objective of improving agriculture and empowering the rural woman; thereby fighting poverty within the South West region of Cameroon. Despite its criticism of the barriers to development created by corruption, political pressure and limited use of local and grass-root partnerships, the study, in assessing these failures also tries to outline vital ways in which the project can be improved upon.

• KDI Journal of Economic Policy
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• 제31권1호
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• pp.1-25
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• 2009

본 논문은 일반적인 뉴 케인지언 이론의 주요 특징을 바탕으로 하는 동태적 확률 일반 균형 모형을 설정하고 이를 바탕으로 하여, 베이지안 추정법을 통해 한국의 자연 산출량과 자연 이자율의 추정을 시도하였다. 본 논문의 주요 결과는 다음과 같다. 첫째, 이러한 이론 모형에 의해 추정된 산출량 갭은 기존의 일반적인 접근법에 의한 추정치보다 변동 폭이 훨씬 작은 것으로 나타났다. 둘째, 다양한 모형 설정을 통해 결과의 민감도를 살펴본 경우, 필립스 커브에서의 과거 지향적 요인 및 소비 행태에서의 습관 형성 등이 한국 거시경제의 동태적 양상을 설명하는 데 중요한 요인일 수 있는 것으로 나타났다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(4)
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• pp.151-154
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• 2001

In this Paper, a new harmonic imaging technique is proposed and evaluated experimentally. In the proposed method, a weighted chin signal with a hanning window is transmitted. The RF samples obtained on each array element are individually compressed by correlating with the reference signal defined as the 2nd harmonic (2f0) component of a transmitted chirp signal generated in a square-law system. The proposed method uses the compressed 2f0 component to form an image, for which the crosscorrelation term with f0 component should be suppressed below at least -60dB. After experiment, the 6dB pulse width and peak sidelobe level of the compressed 2f0 component were 0.7us and -60dB, respectively. This result shows that the proposed method can successfully eliminate the f0 component with a single transmit-receive event and therefore is more efficient than the conventional pulse inversion (PI) method in terms of frame rate. We also observed that the 2nd harmonic compont starts to decrease for source pressure higher than 210kPa in water, which implies that SNR of the 2nd harmonic imaging using short pulses cnanot be incresed beyond a certain limit.

• Corrosion Science and Technology
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• 제19권2호
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• pp.66-74
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• 2020

In this paper, the author's team has carried out a comparative experimental study on the corrosion characteristics of Q235 steel commonly used in large-scale storage tanks under the specific bottom water environment found with Russian and Daqing crude oil. It was found that there is a certain degree of uniform or local corrosion on the tank floor depending on the kind of bottom water. The bottom water corrosion of Daqing crude oil is a uniform corrosion caused by carbon dioxide. While the Russian crude oil bottom water corrosion is clearly local corrosion caused by co-corrosion of carbon dioxide and hydrogen sulfide, here the corrosion rate is obviously higher than that caused by Daqing crude oil. There are two modes of storage tank inspection and maintenance that have been currently adopted by Chinese refining and chemical enterprises: a regular inspection mode and a API581-2016 risk-based detection mode. These modes have been effectively combined to form an intelligent tank inspection and maintenance mode, software tools to support this intelligent inspection and maintenance management have been developed.

• 폴리머
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• 제27권6호
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• pp.603-608
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• 2003

신디오탁틱 폴리스티렌 (5-PS)는 시료의 처리 조건에 따라 여러 구조를 가지며 열처리에 따른 고체상의 구조 전이현상을 보여준다 서로 다른 s-PS 사슬 및 결정 구조를 가지는 시료들을 상온에서 220 $^{\circ}C$까지 온도를 올려가며 열처리하여 준비한 후 FTIR과 FT-Raman 분광계를 이용하여 구조의 변화를 조사하였다. 빠른 결정화 속도 때문에 DSC 실험으로 측정하기 힘든 x-PS 시료의 열처리 시간에 따른 결정화도 변화를 결정 부분과 비결정 부분 infrared특성피크 세기에 따라 측정한 후 Beer-Lambert 법칙에 적용하여 조사할 수 있었다.

• Design & Manufacturing
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• 제14권3호
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• pp.37-43
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• 2020

Progressive drawing processing is one of the manufacturing processes used to mass-produce a variety of products on the industrial site. In this study, the goal is to achieve a uniform product thickness of at least 1.3mm by reducing the wall thickness of the coupler parts used in automotive air conditioning systems to within 15% using A5052-H32 materials. The progressive die was designed using Blank's law of volume invariance. Due to the characteristics of the drawing process, the material thickness in the punch R part decreases and the thickness in the die R part increases. When designing the progressive die of the coupler part, an ironing method, a push back method, and a stand-alone die pad method were applied to each process to design a mold in consideration of the drawing rate and to artificially adjust the thickness change. The suitability of the method used in die design was investigated by measuring the thickness change of forming parts for each process. In the final part, it was confirmed that the thickness measurement values of the five regions of a radial line were implemented as 1.34-1.36 mm.

• Asian Journal of Business Environment
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• 제3권2호
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• pp.17-22
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• 2013

Purpose - This dissertation is based on previous research, and analyzes processing trade, which constitutes a major section of foreign trade in Shandong Province. Research design, data, and methodology - The study uses the survey data on polarization, which is a vital index reflecting the unbalanced growth of regional economic development. The article introduces the processing trade polarization index, and the processing trade polarization fluctuation rate, to predict the geographical polarization posture and development trends in Shandong Province. Results -The development of processing trade in Shandong Province shows the level of gradient from east to west. The first-line growth pole has been formed and developed, and the initial formation of the diffusion mechanism has taken place. However, coordination problems in accompanying regional development have become increasingly prominent. Conclusions - This study focuses on the development of processing trade strategy and suggests overall coordination of development objectives, using non-balanced development goals. According to regional characteristics and development objectives of the processing trade in Shandong Province, the region around the city is divided into innovation diffusion region, enhanced growth areas, areas expected to undertake development, and areas to upgrade in four levels, given the different policy proposals.