• 제어로봇시스템학회논문지
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• 제22권9호
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• pp.745-752
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• 2016

We suggest an efficient Simultaneous Localization and 3D Polygon Map Building (SLAM) method with Kinect depth sensor for mobile robots in indoor environments. In this method, Kinect depth data is separated into row planes so that scan line segments are on each row plane. After grouping all scan line segments from all row planes into line groups, a set of 3D Scan polygons are fitted from each line group. A map matching algorithm then figures out pairs of scan polygons and existing map polygons in 3D, and localization is performed to record correct pose of the mobile robot. For 3D map-building, each 3D map polygon is created or updated by merging each matched 3D scan polygon, which considers scan and map edges efficiently. The validity of the proposed 3D SLAM algorithm is revealed via experiments.

• 대한기계학회논문집B
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• 제21권1호
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• pp.113-124
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• 1997

This work is performed to investigate the pressure drop and heat transfer characteristics in the air side of finned-tube heat exchanger for air conditioner. Experimental apparatus and method are described to simulate the heat exchanger performance by using the three times enlarged model. The pressure drop and heat transfer coefficient were measured and compared for the heat exchangers with a plane fin and a commercial strip fin. The measured data for the strip fin agree well with those of prototype within a few percentages. For the plane fin, the measured data had similar trend to Gray & Webb's correlation at high air velocity, however a new correlation is needed to give more accurate prediction at low air velocity. It is found that most heat was transferred around the front row of the two-row heat exchanger, and the ratio of thermal load at the front tube row was increased for decreasing air velocity.

• 설비공학논문집
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• 제12권1호
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• pp.50-58
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• 2000

Experiments were carried out to obtain the effects of nozzle configuration and jet to jet spacing on the heat transfer characteristics of single line of circular water jets impinging on a constant heat flux plane surface. The nozzle configurations are Cone type, Reverse cone type and Vertical circular type, and the nozzle arrays are single jet(nozzle dia. 8 mm), 1 row of 3 jets and 1 row of 5 jets. Jet velocities ranging from 3m/s to 8m/s were investigated for the nozzle to target plate spacing of 80 mm. For the Cone and Reverse cone type nozzle arrays, the average Nusselt number of 1 row of 5 jets was larger than that of 1 row of 3 jets at Re$_{D}$<45000, but that of 1 row of 3 jets was larger than that of 1 row of 5 jets at $Reo\le45000$. For the Vertical circular type nozzle, however, the average Nusselt number of 1 row of 3 jets was larger than that of 1 row of 5 jets at all jet velocities. In the condition of fixed mass flow rates, the maximum heat transfer augmentation was obtained for 1 row of 5 jets and was over 2 times larger than that of the single jet for all nozzle configurations. The nozzle configurations that produce the maximum average Nusselt number are as follows: For 1 row of 3 jets, the Vertical circular type at $Reo\le45000$ and the Reverse cone type at $Reo\le45000$. But, they are the Reverse cone type at Re$_{D}$<55000 and the Vertical circular type at$Reo\le55000$ for 1 row of 5 jets.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.269-272
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• 2005

영상 데이터의 효과적인 암호화를 위하여 logistic 함수를 이용함 chaos 암호화 알고리즘을 구축하였다. 이 방식은 블록기반 암호화 기법에 비해 빠른 계산을 할 수가 있고 비밀 키로서 두 개의 초기 변수를 수신자에게 보내면 된다. 그렇지만 실수 연산을 하는 관계로 회수를 높여 암호의 안전성을 높이는 대신 행렬 기본 연산을 이용한 합성암호화 알고리즘을 구성하였다. 제안된 알고리즘에서는 송신자에게 logist 함수로부터 생성된 비밀 키와 이를 기반으로 만들어 진 반복 회수 키 열을 그대로 사용한다.

• Wind and Structures
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• 제34권3호
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• pp.275-290
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• 2022

Mobile sand barriers are a new type sand-retaining structure that can be moved and arranged according to the engineering demands of sand control. When only used for sand trapping, mobile sand barriers could be arranged in single row. For the dual purposes of sand trapping and sand stabilization, four rows of mobile sand barriers can be arranged in a staggered form. To reveal the effect of plane layout, the included angle between sand barrier direction and wind direction on the characteristics of flow fields and the sand control laws of mobile sand barriers, numerical computations and wind tunnel tests were conducted. The results showed that inflows deflected after passing through staggered arrangement sand barriers due to changes in included angle, and the sand barrier combination exerted successive wind resistance and group blocking effects. An analysis of wind resistance efficiency revealed that the effective protection length of staggered arrangement sand barriers approximately ranged from the sand barrier to 10H on the leeward side (H is sand barrier height), and that the effective protection length of single row sand barriers roughly ranged from 1H on the windward side to 20H on the leeward side. The distribution of sand deposit indicated that the sand interception increased with increasing included angle in staggered arrangement. The wind-breaking and sand-trapping effects were optimal when included angle between sand barrier direction and wind direction is 60°-90°.

• 한국기계기술학회지
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• 제13권2호
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• pp.39-44
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• 2011

An experimental method, based upon wall visualizations, has been developed to observe air flow near a plane wall around a row of five $45^{\circ}$ inclined jets discharging into a cross stream. This study concerns the variation of injection rate R which is one of the most important parameters governing this flow type. The Results are concentrated on the spatial evolution of two lobes with R. These structures are fastened to jets downstream edge and exist for very low injection rate values which are an indication of jets takeoff at the immediate downstream of injection orifices. The velocity rate of 0.42 marks a change in the structure alimentation system.

• 대한수학회보
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• 제54권4호
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• pp.1421-1441
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• 2017

We compute explicitly the matrix represented by the Toeplitz operator on the Hardy space over a smoothly finitely connected bounded domain in the plane with respect to special orthonormal bases consisting of the classical kernel functions for the space of square integrable functions and for the Hardy space. The Fourier coefficients of the symbol of the Toeplitz operator are obtained from zeroth row vectors and zeroth column vectors of the matrix. And we also find some condition for the product of two Toeplitz operators to be a Toeplitz operator in terms of matrices.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 1996년도 추계학술대회발표논문집; 고려대학교, 서울; 26 Oct. 1996
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• pp.177-181
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• 1996

Systematic classification system for standardization in telecommunication is essential to the standardization R&D strategy. This paper suggests a new reference model for development of work area and classification scheme related to the telecommunications standardization : Cubic and matrix approach. Standardization Work Areas(SWAs) that are upper level of the reference model are classified by its main role and function reflecting the market trends and user needs. Standardization expertise is lower level scheme, which can be regarded as the different possible layers of standardization to be applied to each one of the SWAs grouped under upper level scheme. A new reference model consists of two planes that are SWAs plane and Standardization layer plane. Finally the reference model for classification of SWAs in telecommunication mapping onto matrix table that row and column are defined by SWAs and standardization layer respectively.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제10권1호
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• pp.65-72
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• 2010

For developing navigation system of total hip arthroplasty (THA) and evaluating hip joint kinematics, 3-D pose position of the femur and acetabulum in the pelvic coordinate system has been quantified. The pelvic coordinate system is determined by manually indicating pelvic landmarks in multidetector-row computed tomography (MDCT) images. It includes intra- and inter-observer variability, and may result in a variability of THA operation or diagnosis. To reduce the variability of pelvic coordinate system determination, this paper proposes an automated method in MDCT images. The proposed method determines pelvic coordinate system automatically by detecting pelvic landmarks on anterior pelvic plane (APP) from MDCT images. The method calibrates pelvic pose by using silhouette images to suppress the affect of pelvic pose change. As a result of comparing with manual determination, the proposed method determined the coordinate system with a mean displacement of $2.6\;{\pm}\;1.6$ mm and a mean angle error of $0.78\;{\pm}\;0.34$ deg on 5 THA subjects. For changes of pelvic pose position within 10 deg, standard deviation of displacement was 3.7 mm, and of pose was 1.28 deg. We confirmed the proposed method was robust for pelvic pose changes.

• Steel and Composite Structures
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• 제18권4호
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• pp.811-831
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• 2015

This paper focuses on the strengthening methods used for improving the compression behaviors of perforated box-section walls as provided in the anchorage zones of steel pylons. Rectangular plates containing double-row continuous elliptical holes are investigated by employing the boundary condition of simple supporting on four edges in the out-of-plane direction of plate. Two types of strengthening stiffeners, named flat stiffener (FS) and longitudinal stiffener (LS), are considered. Uniaxial compression tests are first conducted for 18 specimens, of which 5 are unstrengthened plates and 13 are strengthened plates. The mechanical behaviors such as stress concentration, out-of-plane deformation, failure pattern, and elasto-plastic ultimate strength are experimentally investigated. Finite element (FE) models are also developed to predict the ultimate strengths of plates with various dimensions. The results of FE analysis are validated by test data. The influences of non-dimensional parameters including plate aspect ratio, hole spacing, hole width, stiffener slenderness ratio, as well as stiffener thickness on the ultimate strengths are illustrated on the basis of numerous parametric studies. Comparison of strengthening efficiency shows that the continuous longitudinal stiffener is the best strengthening method for such perforated plates. The simplified formulas used for estimating the compression strengths of strengthened plates are finally proposed.