• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.14-18
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• 2001

Rise in cutting force causes tool damage and worsens product quality resulting in machining accuracy deterioration. Especially, fragile material cutting brings about breakage of material and worsens product surface quality. In this study, we trace the locus of cutting force and examine the machined surface corresponding to the cutting force loci. and build up a monitoring system for deciding normal operation or not of cutting process.

• 대한전자공학회논문지
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• 제24권6호
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• pp.980-985
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• 1987

The thin metal films of Cr, Al, Mn and were made in various evaporation rates with 100\ulcornerthickness under 2x10**-9 bar vacuum level. We analized and discussed the relationships between changes of structure, morphology and sheet resistance, light transmittance for the corresponding evaporation rates. As the evaporation rates were decreased at higher rates, grain sizes of all film were decreased, however both of the sheet resistance and light transmittance were increased. At lower evaporation rate, films of Cr and Cu porduced non-stoi-chiometric oxides but Al an Mn showed up amorphous structures.

• 한국CDE학회지
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• 제21권2호
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• pp.50-60
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• 2015

Corresponding to the high consumption rate of the selfie stick for cell phone camera, the design of the product is becoming diverse. However, relatively low cost selfie stick models are not strong enough to stand the weight of the cell phone. This results into a bending of the stick or the accidental fall of the cell phone by the failure of the holding unit. As a solution to the problem, design of selfie stick that is structurally strong enough to stand the weight of the cell phone with the minimum weight for the portability is proposed in this paper.

• Communications for Statistical Applications and Methods
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• 제20권5호
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• pp.377-385
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• 2013

We consider a compound Poisson risk model in which the premium rate changes when the surplus exceeds a threshold. The explicit form of the ruin probability for the risk model is obtained by deriving and using the overflow probability of the workload process in the corresponding M/G/1 queueing model.

• 한국산업정보학회논문지
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• 제2권1호
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• pp.73-87
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• 1997

Multilayer neural network using a modified beackpropagation learning algorithm was introduced to achieve automatic identification of different types of aircraft in a variety of 3-D orientations. A 3-D shape of an aircraft can be described by a library of 2-D images corresponding to the projected views of an aircraft. From each 2-D binary aircraft image we extracted 2-D invariant (L, Φ) feature vector to be used for training neural network aircraft classifier. Simulations concerning the neural network classification rate was compared using nearest-neighbor classfier (NNC) which has been widely served as a performance benchmark. And we also introduced reliability measure of the designed neural network classifier.

• Bulletin of the Korean Chemical Society
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• 제1권1호
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• pp.23-26
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• 1980

Direct photoisomerizations of benzalpyrrolinones yield the corresponding E-isomers via a singlet state, since no effect of oxygen on the reaction rates was observed. The Z-oxodipyrromethene was photoisomerized to the E-isomer in a degassed system. In an aerobic system the oxodipyrromethene 3 was photoisomerized at the early stage of the reaction and photooxygenated slowly at latter stage of the reaction. For bilirubin, other (possibly Z ${\to}$ E) than self-sensitizing $^1O_2$ reaction should have occurred because of the lack of a solvent effect on the self-sensitized photooxidation reaction rate at the early stage.

• Tribology and Lubricants
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• 제32권2호
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• pp.67-71
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• 2016

This study investigates the characteristics of the sapphire wafer chemical mechanical polishing (CMP) process. The material removal rate is one of the most important factors since it has a significant impact on the production efficiency of a sapphire wafer. Some of the factors affecting the material removal rate include the pressure, platen speed and slurry. Among the factors affecting the CMP process, we analyzed the trends in the material removal rate and surface roughness, which are mechanical factors corresponding to both the pressure and platen speed, were analyzed. We also analyzed the increase in the material removal rate, which is proportional to the pressure and platen speed, using the Preston equation. In the experiment, after polishing a 4-inch sapphire wafer with increasing pressure and platen speed, we confirmed the material removal rate via thickness measurements. Further, surface roughness measurements of the sapphire wafer were performed using atomic force microscopy (AFM) equipment. Using the measurement results, we analyzed the trends in the surface roughness with the increase in material removal rate. In addition, the experimental results, confirmed that the material removal rate increases in proportion to the pressure and platen speed. However, the results showed no association between the material removal rate and surface roughness. The surface roughness after the CMP process showed a largely consistent trend. This study demonstrates the possibility to improve the production efficiency of sapphire wafer while maintaining stable quality via mechanical factors associated with the CMP process.

• Journal of Computational Design and Engineering
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• 제2권4호
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• pp.206-217
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• 2015

This paper presents a complete S-shape feed rate scheduling approach (CSFA) with confined jerk, acceleration and command feed rate for parametric tool path. For a Non-Uniform Rational B-Spline (NURBS) tool path, the critical points of the tool path where the radius of curvature reaches extreme values are found firstly. Then, the NURBS curve is split into several NURBS sub-curves or blocks by the critical points. A bidirectional scanning strategy with the limitations of chord error, normal/tangential acceleration/jerk and command feed rate is employed to make the feed rate at the junctions between different NURBS blocks continuous. To improve the efficiency of the feed rate scheduling, the NURBS block is classified into three types: short block, medium block and long block. The feed rate profile corresponding to each NURBS block is generated according to the start/end feed rates and the arc length of the block and the limitations of tangential acceleration/jerk. In addition, two compensation strategies are proposed to make the feed rate more continuous and the arc increment more precise. Once the feed rate profile is determined, a second-order Taylor's expansion interpolation method is applied to generate the position commands. Finally, experiments with two free-form NURBS curves are conducted to verify the applicability and accuracy of the proposed method.

• 한국통신학회논문지
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• 제35권2A호
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• pp.128-133
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• 2010

본 논문에서는 나카가미 페이딩 채널 환경에서 전력 혹은 전송률 적응화 된 직접 대역확산 부호분할 다중접속 통신시스템에서의 최적 칩률에 관하여 연구한다. 주파수 효율을 최대화하는 최적의 칩률은 다중경로 세기 프로파일과 직접파 성분, 그리고 적응화 방식에 의해 결정됨을 알았다. 전송률 적응화 방식에서의 최적의 칩률은 채널 파라미터에 상관없이 다중경로 지연 확산 $1/T_m$ 보다 적다. 이 결과는 전송률 적응화 방식에서는 상관 수신기가 RAKE 수신기보다 더 높은 주파수 효율을 얻을 수 있다는 것을 의미한다. 반면에 전송 전력 적응화 방식에서는 최적의 칩률과 그에 상응하는 RAKE 수신기의 탭 수가 다중경로 세기 프로파일과 직접파 성분에 관한 함수임을 알 수 있었다.

• 한국식품과학회지
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• 제21권2호
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• pp.203-211
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• 1989

근채류를 열풍건조할 경우 수축변형 및 표면 경화현상을 일으켜 품질변화를 수반하게 되므로 본 연구에서는 온도, 상대습도 및 풍속을 조절할 수 있고 건조중의 시료크기 변화를 측정할 수 있는 실험실 규모의 건조장치를 제작하여 무우 및 고구마의 건조특성과 수축특성에 영향을 미치는 외부 요인들에 대해 조사하였다. 건조속도는 무우 및 고구마 모두 항률건조기, 감률건조기, 감률건조 2단계 a 및 b의 4단계로 구분되어 나타났다. 수축속도 곡선은 각각 건조속도에 대응하여 기울기가 다른 4단계로 나타났으며 항률건조 기간에서는 수축속도가 서서히 증가하다가 감률건조 1단계에서 급격히 증가하였고 감률건조 2단계의 초기에 상당하는 점에서 최대에 달하였다. 또한 시료의 두께. 상대습도 및 초기 함수율 등은 표면적 수축에 큰 영향을 미쳤고 시료의 두께가 얇을수록, 그리고 상대습도 및 초기 함수율이 높을수록 평형 상태에서의 수축율은 증가하였다.