• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.50-54
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• 1997

An expert drawbead model is developed to model a cranky drawbead in the finite element analysis of stamping processes. The expert model calculates the drawbead restraining forces (DBRF's) and bead-exit thinning, which are boundary conditions. DBRF's are calculated by considering bending force, unbending force, and friction force in order. Bead-exit thinning are due to the bending and tension during the deformation. The DBFR's and thinning computed form the mathematical model for the basic beads are compared with measurements and correction factors compensating for the differences are found using the multiple linear regression method. The composition beads are assumed to be a combination of basic beads so that the DBRF's and bead-exit thinning are computed to the sum of those of basic beads.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.4060-4066
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• 2021

Flow-accelerated corrosion (FAC) of carbon steel piping is a significant problem in nuclear power plants. The basic process of FAC is currently understood relatively well; however, the accuracy of prediction models of the wall-thinning rate under an FAC environment is not reliable. Herein, we propose a methodology to construct pipe wall-thinning rate prediction models using artificial neural networks and a convolutional neural network, which is confined to a straight pipe without geometric changes. Furthermore, a methodology to generate training data is proposed to efficiently train the neural network for the development of a machine learning-based FAC prediction model. Consequently, it is concluded that machine learning can be used to construct pipe wall thinning rate prediction models and optimize the number of training datasets for training the machine learning algorithm. The proposed methodology can be applied to efficiently generate a large dataset from an FAC test to develop a wall thinning rate prediction model for a real situation.

• Journal of Forest and Environmental Science
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• 제13권1호
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• pp.66-80
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• 1997

잣나무는 최근 10년간 우리나라 인공조림실적 중 31%를 차지하는 주요 조림수종이다. 현재 우리나라 산림(山林)은 대부분의 인공조림지를 포함하여 30년생 이하의 유령림(幼齡林)이 87%를 점유하고 있음에도 보육간벌은 거의 실시되지 못하고 있는 실정이다. 또한 현실정에 적합한 잣나무의 보육간벌 지침도 충분히 확립되어 있지 못하다. 본 연구는 잣나무림의 장기적 보육간벌 시험을 통하여 장차 최적(最適)한 간벌계획(間伐計劃) 및 방법(方法)의 확립 에 기여하고자, 우선 강원대학교(江原大學校) 연습림(演習林)에 설정된 잣나무의 간벌시험지와 기존의 임분수확표를 대상으로 생장함수를 이용하여 잣나무의 생장과정의 변화 등을 분석 고찰하였다. 간벌과정을 파악하기 위한 기초적인 단계로 생장과정을 표현하기 적합한 이론적 생장함수를 선정할 필요가 있다. 이를 위해 Mitscherlich, 4 parameter Richards, 3 parameter Richards의 3종의 생장함수식(生長函數式)을 간벌시험지에서 채취한 임령 18년 전후의 공시목의 직경생장 과정에 적용하였다. 그 결과 3변수 Richards 생장함수식이 가장 적합한 것으로 나타났다. 또한 산림청에서 작성한 잣나무 수확표의 직경과 수고생장, 입목본수의 감소 과정도 3변수 Richards 생장함수식에 의하여 적합하게 추정할 수 있음을 확인하였다. 장래 단목의 간벌에 따른 생장의 변화과정을 추정하기 위해, 단목의 점유 면적에 관계하는 계수 h를 포함하는 생장(生長)모델을 제안하였다. 현재 설치된 간벌시험지에서 향후 일정간격으로 얻어질 간벌시험지의 직경생장 공시자료를 이용하면 계수 h를 추정할 수 있고, 이를 이용하여 제안된 모델의 유용성을 검증, 보완한다면 단목의 생장과정을 사전에 유추하여 간벌의 효과를 표현할 수 있는 수식을 구축할 수 있을 것으로 사료된다.

• 농업과학연구
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• 제27권1호
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• pp.5-12
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• 2000

The main purpose of this study is to obtain spatial image information toward forest thinning process in Larix forest stands. Thirteen different alternatives were simulated to visualize on the basis of actual thinning work photos. The options were illustrated as photos produced by photoshop program. Each alternatives were evaluated by forest visitor group with total 244 respondents after reliability test. Spatial images of 13 thinning photos were measured by 12 semantic differential scale as broad -narrow, ordered-tangled, friendly-unfriendly, monotonous-divers, dry-refreshing, relieved -stifling, healthy-sickly, uniform-scattered, dead-alive, opened-closed, bent-straight, and beautiful-ugly. In comparison with thinning stands and natural stands, thinning works were visual improvement effects of spatial images. Seemingly, this trend is due to definite form beauty, straight and clear length form of coniferous forest, As can be expected, slash and downwood were negatively related to improvement effects of spatial images. The 60% ratio of stem/ tree height and 450-950 trees/ha was positive in attraction of spatial images. Results indicate how to conduct forest thinning system for spatial images on Larix forest stands.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.947-957
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• 2023

Curved cylindrical structures such as elbows have a non-uniform thickness distribution due to their fabrication process, and as a result have a number of complex mode shapes, including circumferential and axial nodal patterns. In nuclear power plants, material degradation is induced in pipes by flow accelerated erosion and corrosion, causing the wall thickness of carbon steel elbows to gradually thin. The corresponding frequencies of each mode shape vary according to the wall thinning state. Therefore, the thinning state can be estimated by monitoring the varying modal characteristics of the elbow. This study investigated the varying modal characteristics of artificially thinned carbon steel elbows for each thinning state using numerical simulation and experimental methods (MRIT, Multiple Reference Impact Test). The natural frequencies of specified mode shapes were extracted, and results confirmed they linearly decreased with increasing thinning. In addition, by comparing single FRF (Frequency Response Function) data with the results of MRIT, a concise and cost effective thinning estimation method was suggested.

• 소성∙가공
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• 제18권1호
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• pp.67-72
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• 2009

This paper covers finite element simulations to evaluate tube bending process of auto chassis component i.e. trailing-arm product. The rear of the auto chassis structure is primarily composed of CTBA and trailing-arm. When a car rolls into a corner, the trailing arm reacts to roll in the same degree as the car body. During the bending process of trailing arm the tube undergoes significant deformation. Thus forming defects such as excessive thinning and flattening of the tube will be formed in the outside of the tube. In this paper, we analyzed the effect of process parameters in rotary draw bending process and searched the optimized combination of process parameters using orthogonal arrays method to minimize the forming defects. In this process we analyzed several parameters which are displacement of pressure die, boosting force, initial position of mandrel bar, dimensions of mandrel in regarding to the thinning and flattening of the tube.

• Korea-Australia Rheology Journal
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• 제13권4호
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• pp.179-187
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• 2001

As part of continuing efforts to investigate nonlinear dynamics and stability of film casting process, our earlier results obtained by Lee et al. (2001b) have been extended in the present study to cover the film casting of both extension thickening and extension thinning fluids. The same instability mechanism and draw resonance criterion previously derived have been found valid here, and a rather complex dynamic behavior of film width in contrast to that of film thickness has also been confirmed. The effect of fluid viscoelasticity on draw resonance, however, exhibits opposite results depending on whether the fluid is extension thickening or thinning, i.e., it stabilizes film casting in the former while destabilizing in the latter. The encapsulation extrusion method which recently has been successfully employed to stabilize industrially important paper coating process, has been theoretically explained in the present study as to why such stabilization is possible.

• 전자공학회논문지B
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• 제29B권8호
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• pp.35-43
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• 1992

We have presented the tracing algorithm for center pixel of character image. Character image was read by scanner device. Performing the tracing process, it can be possible to detect feature points, such as branch point, stroke of 4 directions. So, the tracing process covers the thinning and feature point detection process for improving the processing time. Usage of suggested tracing algorithm instead of thinning that is the preprocessing of character recognition increases speed up to 5 times. The preprocessing chip has been designed by using single layer perceptron algorithm.

• Journal of information and communication convergence engineering
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• 제8권6호
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• pp.716-720
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• 2010

This paper proposes an effective fingerprint identification system with hardware block for thinning stage processing of a verification algorithm based on minutiae with 39% occupation of 32-bit RISC microprocessor cycle. Each step of a fingerprint algorithm is analyzed based on FPGA and ARMulator. This paper designs an effective hardware scheme for thinning stage processing using the Verilog-HDL in $160{\times}192$ pixel array. The ZS algorithm is applied for a thinning stage. The logic is also synthesized in $0.35{\mu}m$ 4-metal CMOS process. The layout is performed based on an auto placement-routing and post-simulation is performed in logic level. The result is compared with a conventional one.

• Advances in materials Research
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• 제2권4호
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• pp.195-208
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• 2013

A comprehensive theory of the spin coating technique has been reviewed and the basic principles and parameters controlling the process are clearly highlighted, which include spin speed, spin time, acceleration and fume exhaust. The process generally involves four stages: a dispense stage, substrate acceleration stage, a stage of substrate spinning at a constant rate and fluid viscous forces dominate fluid thinning behaviour and a stage of substrate spinning at a constant rate and solvent evaporation dominates the coating thinning behaviour. The study also considered some common thin film defects associated with this technique, which include comet, striation, chucks marks environmental sensitivity and edge effect and possible remedies.