• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 춘계학술대회 논문집
• /
• pp.42-45
• /
• 2002

General wheel mark in mono-crystalline silicon wafer finding is able to be expected because it depends on radius ratio and angular velocity ratio of wafer and wheel. The pattern is predominantly determined by the contour of abrasive grits resulting from a relative motion. Although such a wheel mark is made uniform pattern if the process parameters are fixed, sub-surface defect is expected to be distributed non-uniformly because of characteristic of mono-crystalline silicon wafer that has diamond cubic crystal. Consequently it is considered that this phenomenon affects the following process. This paper focused on kinematic analysis of wafer grinding process and simulation program was developed to verify the effect of process variables on wheel mark. And finally, we were able to predict sub-surface defect distribution that considered characteristic of mono-crystalline silicon wafer

• 한국정밀공학회지
• /
• 제28권9호
• /
• pp.1011-1017
• /
• 2011

Servo control loops are a core part in the control architecture of machine tools. Servo control loops manage acceleration, velocity and position of all the axes in a machine tool based on commands. The performance of servo control loops sets the basis for quality of production paris and cycle time reduction. First, this paper presents a general control architecture of machine tools and several control schemes in literature, which can be applicable to machine tools control; including Zero Phase Error Tracking Control (ZPETC) and Cross Coupling Control (CCC). After that, modem control strategies to mitigate the problem of high speed machining are reviewed. In high speed machining, high accelerations excite the machine structure up to high frequencies, thereby exciting the structure's modes of vibration. These structural vibrations need to be damped if accurate positioning or trajectory following is required. Input shaping is an attractive option in dealing with structural vibrations. The advantages and drawbacks of using input shaping technique for machine tools are discussed in detail.

• 한국농공학회지
• /
• 제40권4호
• /
• pp.85-93
• /
• 1998

In the 2nd year study of a 5 year project to evaluate the soil quality and develop the best management practices for mountaineous soils, 11 runoff plots were treated and monitored with respect to physical property of the soil, runoff and sediment discharge, and the following results were obtained. 1. Bulk density and porosity did not show any siginificant difference between experimental treatments. 2. Runoff was basically dependent on the soil's physical property and tillage. Up-and-down plots showed the highest runoff while contour plots the lowest runoff. 3. Sediment yield in the mountaineous soils was directly related to tillage and residue cover. Residue covered plots showed the lowest sediment yield and up-and-down plots the highest sediment yield. And it is recommended that the best management practices using till_age and residue cover for the mountaineous soils must be developed to protect soil quality and maintain agricultural productivity.

• 대한의용생체공학회:의공학회지
• /
• 제10권3호
• /
• pp.331-342
• /
• 1989

This paper presents a new algorithm that extracts lung region in X-Rays and enhance.j the region. Comparing to prior algorithms that enhance whole X-Ray image, this algorithm leads more effective results. For this algorithm extracts lung region first, and enhances the lung region excluding parameters of other region. For choosing optimal threshold, we compare OTSU's mothod with the proposed method. We obtain lung boundary using contour following algorithm and Rray level searching method in gray level rescaled image. We Process histogram equalization in lung region and obtain enhanced lung image. By using the proposed algorithm, we obtain lung region effectively in chest X-Ray that need in medical image diagnostic system.

• 대한치과의사협회지
• /
• 제56권9호
• /
• pp.503-511
• /
• 2018

Outcome of esthetic ceramic restorations are affected by tooth size, gingival contour, occlusal relationship, etc. For this reason, demand of orthodontic treatment before esthetic ceramic restoration is increasing. If a Bolton ratio discrepancy, a problem of the maxillary incisor's vertical position, a problem of inclination of anterior teeth, a pathogenic occlusion is existed, a pre-prosthodontic orthodontics should be accomplished. These problems can be satisfactory only after the prosthetic treatment is performed after orthodontic treatment. When orthodontic treatment is given, it should be treated with the following principle. 1. Treat it in the direction of functioning occlusion. 2. Keep the patient's stable occlusal scheme. 3. Treat the teeth by considering the average tooth size and Bolton ratio. Ortho-Prostho combined treatment with optimal treatment plan can lead a patient's function, esthetics, and long-term stability.

• 한국전산유체공학회지
• /
• 제2권1호
• /
• pp.54-65
• /
• 1997

Wall wetting in diesel engines has been considered as a bad phenomenon because of fuel deposition which makes fuel/air mixing and evaporation worse. In order to avoid the problem, many research works have been carried out. One of the studies is on new combustion chamber systems which are using spray impacting on a wall. In this study a new type of chamber system is analysed using wall impaction model introduced and assessed in the coupled paper. The gas phase is modelled in terms of the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction, The liquid phase is modelled following the discrete droplet model approach in Lagrangian form. With various conditions the spray distribution, vapor contour and gas flows are analyzed, and then design factors of those combustion systems are recommended.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2000년도 춘계학술대회 논문집
• /
• pp.767-770
• /
• 2000

A novel process is newly developed for building RP(Rapid Prototyping) parts using a sheet lamination technique. The build process of existing sheet lamination type RP machines consists of the following steps : feeding, lamination and cutting. In this process, the laminated part of an object is often scratched by a cutter or damaged by a laser beam due to the cutting operation preceded by lamination, In addition, decubing of the unused portion from the laminated block is difficult. In the new process, cutting operation is performed before lamination. The cutting operation takes place while a paper sheet is firmly attached on the plate using electrostatic force. Then liquid glue is applied to the calculated region of the given contour for lamination. The process aims to manufacture a $2k RP machine, what we call the Freeform Mater I, that can use A4 or latter-size used papers. A prototype machine that demonstrates the design concept is built and further research issues are discussed.

• 한국측량학회지
• /
• 제13권2호
• /
• pp.285-289
• /
• 1995

본 논문은 GPS로부터 측정된 타원체고와 Spirit Levelling으로부터 측정한 정표고를 이용하여 기하학적인 방법에 의하여 지오이드를 결정하였다. 기하학적인 지오이드고의 계산을 위하여 88점의 GPS측정데이타를 사용하였으며, 지오이드고는 간단하게 타원체고와 정표고의 차이를 구하고 보간법에 의하여 지오이드면을 결정하였다. 또한 보간법의 정확도를 평가하기 위하여 Minimum Curvature 방법과 Least Square Plane Fit방법을 사용하여 보간한 결과와 실측치를 비교하였으며, FFT를 적용하여 중력학적인 방법으로 결정한 지오이드고와 비교, 분석하였다.

• 전자공학회논문지CI
• /
• 제45권3호
• /
• pp.149-159
• /
• 2008

참조 영상을 이용하여 영상의 분위기를 전환하고자 할 때, 영상의 분위기에 영향을 주는 요소 중 하나인 색을 이용하여 영상이 가지는 분위기를 변환한다. 색을 변환할 때, 국부적인 색상의 특징을 반영하기 위해 입력 영상의 화소에 대하여 색인을 하는데 낮은 채도 상에서는 색상의 식별력 저하로 인해 부적절한 색인의 색상 항목으로 색인이 되는 문제가 발생한다. 따라서 본 논문에서는 유채색과 무채색을 분리하여 처리함으로써, 낮은 채도 상에서의 잘못된 색인이 일어나지 않도록 제한하는 기법을 제안한다. 제안하는 기법은 채도의 문턱치를 이용하여 유채색과 무채색을 구분하는 단계, 구분된 화소들을 실린드리컬 거리(Cylindrical metric)를 이용하여 11가지 색상 항목(Index color)으로 색인을 하는 단계, 각 색상 항목의 우선순위 결정하고 평균과 표준편차를 구하는 단계, 마지막으로 Lab 색 공간에서 색을 변환하고 영상의 잡음과 의사 윤곽선(pseudo-contour)을 제거하기 위한 후처리 단계의 4단계로 구성된다. 실험결과를 통해 제안하는 기법은 낮은 채도 상에서도 유채색과 무채색이 잘 분리되어 색인이 되었으며 원본 영상의 색이 참조 영상의 색으로 자연스럽게 변환된 결과를 얻을 수 있음을 확인하였다.

• Archives of Plastic Surgery
• /
• 제36권4호
• /
• pp.475-480
• /
• 2009

Purpose: To correct the facial asymmetry and to achieve symmetry and balance, not only the soft tissue restoration of deficits but also creation and facial contour line such as mandible border and angle is important. Micro fat graft has limitation such as high resorption rate and somewhat limited ability to emphasize the rigid bony characteristics of the mandible angle due to its innate soft consistency. We have investigated the advantages of dermal fat graft over micro fat graft to correct asymmetry of the lower face in patients who had undergone mandibular reconstruction or distraction, using comparative analysis. Methods: Total of 12 patients were enrolled in our study: 6 micro fat graft and 6 dermal fat graft. Postoperative results were compared and analyzed at immediate postoperative period and more than 1 year later in each group with photographs, and analysised with image J program. Result: No complications were noted both in the micro fat type and the dermal fat type of procedures such as fat necrosis or micro calcifications. All of the patients who received micro fat graft, however had considerable amount of fat resorption after the procedure which led to two additional fat graft procedures. Although minor contour obliteration due to contracture was seen in patients who had undergone dermal fat graft procedure, no definite resorption was found even after more than one year follow-up. Results of dermal fat graft patients were satisfactory in terms of mandible angle symmetry. Secondary revision was necessary in one case due to overcorrection using dermal fat graft. Conclusion: The dermal fat graft has many advantages over the conventionally more popular micro fat graft to correct asymmetry of the lower face following mandible reconstruction owing to its lower resoption rate, more effective in emphasizing the natural curvilinear anatomical contours of the mandible angle and body and lower complication rates such as fat necrosis or micro calcifications.