• 대한의용생체공학회:의공학회지
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• 제38권5호
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• pp.219-226
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• 2017

Penalized-likelihood (PL) reconstruction methods for transmission tomography are known to provide improved image quality for reduced dose level by efficiently smoothing out noise while preserving edges. Unfortunately, however, most of the edge-preserving penalty functions used in conventional PL methods contain at least one free parameter which controls the shape of a non-quadratic penalty function to adjust the sensitivity of edge preservation. In this work, to avoid difficulties in finding a proper value of the free parameter involved in a non-quadratic penalty function, we propose a new adaptive method of space-variant smoothing with a simple quadratic penalty function. In this method, the smoothing parameter is adaptively selected for each pixel location at each iteration by using the image roughness measured by a pixel-wise standard deviation image calculated from the previous iteration. The experimental results demonstrate that our new method not only preserves edges, but also suppresses noise well in monotonic regions without requiring additional processes to select free parameters that may otherwise be included in a non-quadratic penalty function.

• 한국산림과학회지
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• 제81권4호
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• pp.337-345
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• 1992

산지유역은 대부분이 수원대(水源帶)이고 수자원상 중요한 위치를 차지하고 있기 때문에 수자원의 확보와 홍수재해의 경감을 위해 삼림의 유량조절기능과 우수유출(雨水流出)에 미치는 삼림의 영향을 정량적으로 해석할 필요가 있다. 본 논문은 유출해석모델로 Kinematic wave법을 채용했다. 그리고 모델의 조변수(助變數)(parameter)로서 사면조도계수(斜面組度係數)를 동정(calibration)에 의해 추정해서 그 값으로 삼림의 이수기능(理水機能)을 평가할 수가 있었다. 본 논문에 사용한 수문자료(水文資料)는 동경대학(東京大學) 애지(愛知)연습림의 두 시험유역에서 관측한 자료이다. 삼림이 수기능의 평가방법으로서 제안한 조도계수의 추정방법과 그 결과를 요약하면 다음과 같다. 1. 조도계수($N_s$)는 산복사면의 표면유(表面流)의 유수저항(流水抵抗)을 나타낸다. 즉 삼림의 성장과 함께 $A_o$층(層)의 발달에 의해 우수(雨水)의 유하(流下)가 방해를 받는다. 2. Kinematic wave법(法)에 의한 모델실험에 의하여 하도(河道)의 직접유출량(直接流出量)을 계산할 때 조변수로서 사면 조도계수의 값을 추정할 수가 있었다. 3. 혈궁유역(穴宮流域)에서의 조도계수는 지수함수적으로 일정치에 점근(漸近)하면서 증대하는 곡선상에 있고, 치산 조림의 성과가 나타나기 시작한 1940년대 전후의 급격한 증대가 특징적이다. 한편 백판유역(白坂流域)에서는 직선적으로 미증(微增)경향이 있는 것으로 지표의 상태에는 거의 변화가 없었던 것이 추찰(推擦)된다. 4. 조도계수값의 증대는 직접유출량의 감소 및 기저유츨량(基底流出量)의 증대와 직접적인 관련이 있었다. 임상(林相)의 양호화(良好化)와 함께 한 강우에 대한 직접유출량의 비율은 상대적으로 감소하고, 기저유출량의 비율이 증가하는 경향이 인정되었다. 그러나 한 강우에 대한 유출량의 절대량은 경년적(經年的)으로 감소해 가는 경향이 있었다.

• 대한화장품학회지
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• 제45권4호
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• pp.373-380
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• 2019

얼굴과 하박내측의 피부는 경피수분손실량(TEWL), 피부 수분량, 탄력 등에서 많은 차이를 보이고 있다. 특히, 이전 연구 결과에서 얼굴피부와 하박내측 피부는 수화(hydrating) 과정에 따른 탄력특성의 차이를 보여 주었다. 이에 본 연구에서는 신체부위에 따른 피부특성 차이는 각 신체부위를 구성하고 있는 각질세포 특성과 연관성이 있을 것이라는 가정하에 atomic force microscopy (AFM)을 이용하여 각질세포 표면 특성을 비교 연구하였다. 각질세포 표면의 거칠기(roughness)와 villus-like projections (VPs)을 이용하여 비교 평가 하였다. 더 나아가 얼굴피부, 하박내측, 입술 피부의 각질세포 표면을 정성적으로 비교해 보았다. 각질세포는 8명의 피험자의 얼굴과 하박내측 피부에서 tape-stripping을 이용하여 채취하여, AFM을 이용하여 40 ㎛ × 40 ㎛ 크기로 각질세포의 아랫면 표면 특성(bottom surface of corneocyte)을 측정하였다. 그 결과, 얼굴 각질세포 아랫면 표면 거칠기는 388.34 ± 86.189 nm이었고, 하박내측 각질세포 아랫면 표면 거칠기는 662.27 ± 224.257 nm로 하박내측 각질세포가 얼굴 각질세포보다 더 거친 표면 특성임을 확인하였다(p < 0.001). 관찰된 VPs의 양을 비교해보면, 입술 각질세포가 가장 많았고, 그 다음이 얼굴 각질세포이며, 하박내측 각질세포는 낮은 수준이었다. 이러한 결과를 통해 볼때, 각질세포 표면 특성이 얼굴과 하박내측 피부 사이에 보이는 특성 차이에 어느 정도 관여하고 있음을 확인할 수 있었으며, VPs는 부위별 피부 특성 연구에 유용한 parameter가 될 수 있는 가능성도 확인할 수 있었다. 그리고, AFM은 각질세포 표면의 미세한 구조적 차이를 비교 연구하는데 매우 유용한 기기임을 알 수 있었다. 향후 조금 더 많은 연구가 진행된다면 각질세포에 대한 새로운 화장품 효능 평가법이 개발될 것으로 사료된다.

• Journal of Computational Design and Engineering
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• 제1권2호
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• pp.128-139
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• 2014

This study investigates the effects of machining parameters as they relate to the quality characteristics of machined features. Two most important quality characteristics are set as the dimensional accuracy and the surface roughness. Before any newly acquired machine tool is put to use for production, it is important to test the machine in a systematic way to find out how different parameter settings affect machining quality. The empirical verification was made by conducting a Design of Experiment (DOE) with 3 levels and 3 factors on a state-of-the-art Cincinnati Hawk Arrow 750 Vertical Machining Center (VMC). Data analysis revealed that the significant factor was the Hardness of the material and the significant interaction effect was the Hardness + Feed for dimensional accuracy, while the significant factor was Speed for surface roughness. Since the equally important thing is the capability of the instruments from which the quality characteristics are being measured, a comparison was made between the VMC touch probe readings and the measurements from a Mi-tutoyo coordinate measuring machine (CMM) on bore diameters. A machine mounted touch probe has gained a wide acceptance in recent years, as it is more suitable for the modern manufacturing environment. The data vindicated that the VMC touch probe has the capability that is suitable for the production environment. The test results can be incorporated in the process plan to help maintain the machining quality in the subsequent runs.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 추계학술대회 논문집
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• pp.196-201
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• 1997

The biggest challenge facing today's manufacturing industry is better quality and high productivit. From an economic point of view, productivity is the most important parameter, as high productivity will reduce the cost. However, the customers of today are not only cost concerned, but also quality conscious. So high accuracy levels should also be achieved in the manufacturing process. The aim of this paper is to get a comprehensive understanding of its machinability properties and to investigate the relationship between cutting conditions and surface roughness for Ball End Mill cutting process so as to enhance its practical application.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.52-57
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• 1993

In this study, the inclined endmilling process with a 3-axis machining center using inalined jigs is introduced for the purpose of reducing overall Dies/Molds machining time and improving the machining accuracies. In order to analyse the cutting mechanism of a given endmill more accurateky, the unification of the cutting mechanism model of 3-different-kind endmills is examined by using the mose radius as a parameter. By adding radial runouts as a parameter which influences on surface roughness, the superposition method which defines the effective cusp heigh superposing the cutter mark height and the conventional cusp height is modified. And 3-D surface topography predicted in this paper looks like the surface normally observed in practice. Through machining experiments, the adequacy of the superposition algorithm was confirmed.

• 산업공학
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• 제12권3호
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• pp.458-467
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• 1999

In this paper, we analyze the calendaring operation in the process of paper manufacturing. Controllable parameters involved in the calendaring operation are the calendar material, temperature and pressure. Main objective of this paper is to find the robust design of these parameters which would provide consistent quality of paper in terms of the thickness, brightness, and roughness. We first use a split-plot design in the context of a central composit design for a preliminary analysis to find the proper calendar material. Next, response surfaces for the mean and variance of each quality attribute are fitted as functions of calender temperature and pressure. Bootstrap resampling approach is used to find the robust parameter design.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.642-645
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• 2004

This paper focuses on recovering systematic biases during LIDAR calibration, particularly using natural surfaces as control features. Many previous approaches have utilized all the points overlapping with the control features and often experienced with an inaccurate value converged with a poor rate due to wrong correspondence in pairing a point and the corresponding control features. To overcome these shortcomings, we establish a preventive scheme to select the pairs of high confidence, where the confidence value is based on the error budget associated with the point measurement and the linearity and roughness of the control feature. This approach was then applied to calibraring the LIDAR data simulated with the given systematic biases. The parameters were successfully recovered using the proposed approach with the accuracy and convergence rate superior to those using the previous approaches.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.322-325
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• 2000

In the previous report1), the grinding characteristics of quartz were investigated. In this paper, the grinding mechanisms of brittle materials including ceramics and quartz are modeled and a new parameter SDR(Surface roughness Direction Ratio) is proposed to characterize the grinding mechanisms of such materials. A set of experiments were performed to verify the effectiveness of the suggested parameter. The experimental results indicate that the plastic deformation is the dominant material removal mode at the grinding conditions which show the higher value of SDR. In the case of quartz, the material was removed by brittle fracture in a lower value of SDR and by plastic deformation in a higher value of it. SDR is not affected by wheel mesh size when brittle fracture occured. But in the plastic deformation case, SDR value increases with wheel mesh size.

• 대한안전경영과학회지
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• 제3권1호
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• pp.117-125
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• 2001

Polyacetal resin is usually used to make molds, but it is difficult to achieve dimension accuracy during molding. Therefore it is usually necessary to cut the polyacetal resin after a molding process. Polyacetal resin is easily machining by standard machine tool. Acetal is also a thermal stable material which can be totted without coolant Another concern about the use of polyacetal resin is that it absorbs water easily, which also results in problems with dimension accuracy Therefore, in this study, the cutting resistance of water-absorbed polyacetal resin and its surface roughness after cutting in order to achieve the highest degree of accuracy in the cutting of polyacetal resin were investigated. Also, The Robust Design method uses a mathematical tool called orthogonal arrays to study a large number of decision variables with a small number of experiments. It also uses a new measure of quality, called signal-to-noise (S/N) ratio, to predict the quality from the customer's perspective. Thus, we have taken Taguchi's parameter design approach, specifically orthogonal array, and determined the optimal levels of the selected variables through analysis of the experimental results using S/N ratio.