• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.498-503
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• 2002

This paper has studied thermal characteristics of machine tool to develope high speed spindle and optimum design considering the thermal deformation. Comparing the test data of temperature measurement and structural analysis data using FEM, we verified the test validity and predicted thermal deformation, influence of spindle generation of heat, and established cooling system to prevent the thermal deformation. 1) The temperature rise of spindle system depends on increasing number of rotation and shows sudden doubling increment of number of rotation over 7,000rpm. 2) Oil jacket cooling can be effective cooling method below 8,000rpm but, over 8,000rpm, it shows the decrement of cooling effect. 3) Comparing FEM analysis results and revolution test results, we can confirmn approximate temperature change consequently, it is possible to simulate temperature rise and thermal distribution on the inside of spindle system. 4) We can confirm that simulated approach by FEM analysis can be effective mettled in thermal-appropriate design.

• 대한전자공학회논문지
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• 제23권3호
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• pp.345-350
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• 1986

This paper deseribes the design of a vector-coordinate rotation processor and the apporoximate evaluations of sine and consine based upon the use of residue number systems. The proposed algorithm results in a considerable improvement of computational speed as compared to the CORDIC algorithm. According to the results of computer simulation, the mean error of sine and cosine is 0.0025, and the mean error of coorcinate rotation arithmatic is 0.65. The proposed processor has the efficiency for the design and fabrication of integrated circuits, because it consists of an array of identical lookup tables.

• 한국정보통신학회논문지
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• 제21권1호
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• pp.8-16
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• 2017

줄넘기와 같은 반복적인 운동들의 횟수를 측정하는 방법은 다양하다. 그 중 대표적으로 가속도 센서의 가속도 값 또는 자이로스코프 센서의 각속도 값을 이용하여 파형과 데이터의 특징을 추출하고 선택한 후 선택한 특징을 알고리즘에 적용하여 측정하는 방법이 있다. 하지만 고정되지 않고 유동적인 운동들은 다양한 변수가 존재한다. 이러한 경우의 수를 하나의 센서만으로 찾기 쉽지 않으며, 잡음과 진동에 취약한 가속도계와 드리프트 현상이 발생하는 각속도의 문제점으로 인하여 정확한 줄넘기 개수를 세는데 다소 정확도가 떨어지는 현상이 발생한다. 본 논문에서는 기존의 방식인 단일 센서만의 값으로 회전운동을 검출하는 방법의 문제점을 개선하기 위해 가속도와 각속도의 데이터값에 상보 필터를 적용하고, 가속도와 각속도 값이 상호보완 하여 서로의 문제점을 최소화하여 보다 정확한 개수를 측정할 수 있는 방법을 제안한다. 제안하는 방법은 센서 값의 특징만을 보고 판단하는 방법과 비교하여 정확하게 줄넘기 개수를 측정하는 것을 실험 결과를 통해 확인할 수 있다.

• 전자공학회논문지SC
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• 제49권3호
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• pp.31-37
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• 2012

본 논문에서는 기븐스 회전 기반의 QR 분해를 고속으로 하기 위한 하드웨어 구조를 제안하였다. 제안된 접근 방식은 단위시간 당 처리량을 증대하기 위해 임의의 행렬을 직교행렬과 상삼각행렬의 곱으로 분해하는 과정 중 기븐스 회전을 위한 행렬의 기준 성분을 1개만 고정적으로 두지 않고 가능한 한 증가시킨다. 또한 기븐스 회전을 고속의 SSL-코딕(CORDIC)으로 구성하여 처리속도를 더욱 증대하였다. 제안 방법은 QR 분해의 성능을 기존의 TSA(triangular systolic array) 방식에 비해 비약적으로 향상되었을 뿐 아니라, 연산의 중간 결과를 저장하는 플립플롭의 개수를 경감하여 회로의 면적 또한 감소시키는 효과를 보여준다. 제안하는 QR 분해 하드웨어는 TSMC $0.25{\mu}m$ 공정을 사용하여 구현되었다. 실험 결과, $8{\times}8$ 행렬의 QR 분해에 대해 제안 구조는 TACR/TSA 기반 구조와 비교하여 75.24%의 성능 향상을 이룩할 수 있었다.

• 대한기계학회논문집B
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• 제26권1호
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• pp.159-169
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• 2002

The present study investigates in detail the combined effects of the Coriolis and centrifugal farce on the development of laminar flows in a square-sectioned U-bend rotating about an axis parallel to the center of bend curvature. When a viscous fluid flows through a rotating curved region, two types of secondary flow occur. One is caused by the Coriolis force due to the rotation of U-bend and the other by the centrifugal farce due to the curvature of U-bend. When the values of Rossby number and curvature ratio are large, the flow field in a rotating U-bend can be represented by two dimensionless parameters ; the Dean number K$\_$LC/=Re/√λ and a body ratio F=λ/Po. For positive rotation, where the rotation is in the same direction as that of the main flow, both the Coriolis force and the centrifugal force act radially outwards, the directions of the two secondary flows are the same. Therefore, the flow structure is qualitatively similar to that observed in a stationary curved duct with a larger f7c. On the other hand, in case of negative rotation, where two farces act in opposite direction, more complex flow fields can be observed depending on the relative magnitudes of the forces.

• Journal of Microbiology and Biotechnology
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• 제14권3호
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• pp.435-441
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• 2004

A drum bioreactor was used for the treatment of sandy soil contaminated with three kinds of aromatic compounds (phenol, naphthalene, and phenanthrene), and its performance was evaluated in two different operation modes; intermittent and continuous rotation of drum. When the drum bioreactor was operated with one rotation per day, the microbial growth was relatively low, and most of the compounds remaining in soil, except naphthalene of 90 mg/kg dry soil, disappeared mainly due to volatilization. In contrast, when the drum was continuously rotated at 9 rpm (rotation/min), the number of microorganisms was drastically increased and nitrate was consumed for growth as a nitrogen source. Phenol and phenanthrene were removed at rates of 56.7 mg/kg dry soil/day and 3.2 mg/kg dry soil/day, respectively.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 2008년도 공동추계학술대회
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• pp.245-246
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• 2008

The goal of this study is to explore the possibility of KLT tracker for tracking the features between two images including rotation and shift. As a test site, Jangsu-Gun area of South Korea is selected and the images taken from UAV camera are used for analysis. The analysis was carried out using KLT tracker developed in a PC environment. The results of the experiment used two images with the large overlapping area are compared with the results of two images with the little overlapping area and rotation. Overall, the research indicates that the integrated features of littlerotation and motion images can significantly increase during the tracking process. But using KLT tracker for extracting and tracking features between images with large rotation and motion, the number of tracked features are decreased.

• Coupled systems mechanics
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• 제6권3호
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• pp.317-333
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• 2017

The present paper is concerned with the investigation of Rayleigh waves in a homogeneous transversely isotropic magnetothermoelastic medium with two temperature, in the presence of Hall current and rotation. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi theories of Type-II and Type-III. Secular equations are derived mathematically at the stress free and thermally insulated boundaries. The values of Determinant of secular equations, phase velocity and Attenuation coefficient with respect to wave number are computed numerically. Cobalt material has been chosen for transversely isotropic medium and magnesium material is chosen for isotropic solid. The effects of rotation, magnetic field and phase velocity on the resulting quantities and on particular case of isotropic solid are depicted graphically. Some special cases are also deduced from the present investigation.

• 대한기계학회논문집B
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• 제24권6호
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• pp.845-851
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• 2000

In this paper, we show the numerical and the experimental results of two-dimensional fluid motions inside a rectangular container subjected to a background rotation added by a rotational oscillation. In the PlY experiment we apply a new algorithm, new three step search(NTSS), to the velocity calculation. In the numerical computation, the linear Ekman-pumping model was used to take the bottom friction effect into account. It was found that it well produces the experimental results at low e number.

• 전자공학회논문지B
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• 제30B권4호
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• pp.44-55
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• 1993

In this paper, we proposed a new optical method for the efficient recognition of Korean characters. There are six filters in the proposed method which employed the concepts of amplitude-modulated phase-only filter(AMPOF) and spatial frequency modulation(SFM). Here, amplitude modulation is used to achieve improved correlation discrimination and SFM is to reduce the number of filters. We also used a simplified synthetic discriminant function(SDF) for distortion invariance of input image. In order to recognize the partial rotation invariant Korean characters, the proposed distortion invariant minimum average correlation energy (MACE) filter is synthesized SFM, partial rotation invariant filter (PRIF), AMPOF and MACE for partial rotation invariance in the frequency domain. The advantage of the proposed filters is to supress the sidelobes of cross correlation peak away from the autocorrelation peak and to produce sharp correlation peaks. We performed simulation and optical experiment for some of Korea characters using the proposed method. The results show that the proposed method has more improved discriminant ability and reduced processing time than the conventional methods.