• 한국인터넷방송통신학회논문지
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• 제16권2호
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• pp.93-99
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• 2016

본 논문은 무인기용 Ku 대역 위성추적 안테나 시스템의 다중모드 모노펄스 추적 시스템을 위한 소형구조 도파관 고차모드 커플러를 설계, 제작 및 성능시험을 수행하였다. 제안된 고차모드 커플러는 이동형 탑재용 위성추적 안테나 시스템에 적용이 가능하도록 장착성을 감안, 동축 구조의 도파관 구조를 이용하였다. 또한 제안된 커플러를 이용하여 출력된 추적 오차 신호의 패턴을 측정하고 설계된 주파수 대역내에서 적정한 추적 오차가 도출됨을 확인하였다. 제안된 커플러 구조는 향후 정밀추적이 요구되는 다중모드 모노펄스 위성추적시스템에 이용될 것으로 기대된다.

• Structural Engineering and Mechanics
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• 제55권4호
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• pp.719-742
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• 2015

This paper dealt the free vibration analysis of thick truncated conical composite sandwich shells with transversely flexible cores and simply supported boundary conditions based on a new improved and enhanced higher order sandwich shell theory. Geometries were used in the present work for the consideration of different radii curvatures of the face sheets and the core was unique. The coupled governing partial differential equations were derived by the Hamilton's principle. The in-plane circumferential and axial stresses of the core were considered in the new enhanced model. The first order shear deformation theory was used for the inner and outer composite face sheets and for the core, a polynomial description of the displacement fields was assumed based on the second Frostig's model. The effects of types of boundary conditions, conical angles, length to radius ratio, core to shell thickness ratio and core radius to shell thickness ratio on the free vibration analysis of truncated conical composite sandwich shells were also studied. Numerical results are presented and compared with the latest results found in literature. Also, the results were validated with those derived by ABAQUS FE code.

• 대한가정학회지
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• 제26권4호
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• pp.15-30
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• 1988

The purpose of this study is to collect basic data which will be effective in performing nutrional education. This study was conducted at Taegu area and adjacentrural area from June to July in 1986. The completely answered questionnaires were analyzed for food habits, purchase of food, the sources of nutrition information and general characteristics of housewives of 20's to 50's. The results obtained are summarized as follows ; 1) The major food of breakfast was boiled rice (93.9%). With decreasing level of education and in rural area, the percent of boiled rice was higher. 2) The frequency of eating out with family is higher in urban area, younger age, and nuclear family. 3) The preference for eating between meals appeared in order of bread and cakes, cookies, and the others. 4) The preference for desserts appeared in order of fruits, coffee, the other, coarse tea, adlay tea, and gingseng tea. 5) The purchasing place for vegetables and fruits was market (53.5%) on the whole, but in rural area, the percent of self production was higher (63.6%). 6) With increasing age and decreasing level of education, the percent of accuracy of nutrition knowledge was lower. 7) Sources in the knowledge of nutrition appeared in order of Radio and T.V., relatives, cookbooks, newspapers and magazines, lectures in cooking school. In order to promote nutritional status of family, nutritional education for housewives must be accomplished in the first place.

• Steel and Composite Structures
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• 제43권1호
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• pp.1-17
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• 2022

The free and forced nonlinear dynamic behaviors of Porous Functionally Graded Material (PFGM) plates are examined by means of a High-Order Implicit Algorithm (HOIA). The formulation is developed using the Third-order Shear Deformation Theory (TSDT). Unlike previous works, the formulation is written without resorting to any homogenization technique neither rule of mixture nor considering FGM as a laminated composite, and the distribution of the porosity is assumed to be gradually variable through the thickness of the PFGM plates. Using the Hamilton principle, we establish the governing equations of motion. The Finite Element Method (FEM) is used to compute approximations of the resulting equations; FEM is adopted using a four-node quadrilateral finite element with seven Degrees Of Freedom (DOF) per node. Nonlinear equations are solved by a HOIA. The accuracy and the performance of the proposed approach are verified by presenting comparisons with literature results for vibration natural frequencies and dynamic response of PFGM plates under external loading. The influences of porosity volume fraction, porosity distribution, slenderness ratio and other parameters on the vibrations of PFGM plate are explored. The results demonstrate the significant impact of different physical and geometrical parameters on the vibration behavior of the PFGM plate.

• 한국응급구조학회지
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• 제25권3호
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• pp.71-80
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• 2021

Purpose: The purpose of this study is to investigate the characteristics and appropriateness of the Korean-type severity classification by ambulance based on the medical records of 43,561 emergency patients who were brought to the emergency medical center via ambulance between January 1, 2015 and December 31, 2017. Methods: This study analyzed the classification characteristics of the Korean severity classification tool by applying them to emergency patients who visited the emergency medical center. Results: As a result of the study first, among the categories of home hospitals according to the results of visits, "other," "low consciousness," and "dyspnea" in the order of 129 ambulances were statistically significantly higher. In the order of "low consciousness" and "trauma," the "trauma" category was 5.3% higher than that of 129 ambulances. Conclusion: Among the classification items, "others," "low consciousness," and "dyspnea" were significantly higher in the group of patients who boarded 129 ambulances, and "others," "low consciousness," and "traumatic" were significantly higher in the 119 ambulances.

• 한국대기환경학회지
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• 제8권4호
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• pp.221-228
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• 1992

In order to evaluate the degree of air pollution, soils from 125 and 60points of main streets of Seoul and Daejeon, respectively, were sampled and analyzed for the contents of lead, copper, iron and zinc by nitric acid($HNO_3$) extraction followed by atomic absorption spectrophotometry during June and September, 1990. The Pb contents of Seoul and Daejeon were 350.2$\mu$g/g and 175.9$\mu$g/g, respectively, which were 14.5times and 7.3times respectively higher than the control(24.0). In Seoul, the commercial area gave the highest value followed by resdential and industrial areas in the decreasing order, while the order in Daejeon was Industrial, commercial and residential areas. The Cu contents in Seoul and Daejeon were very similar(236.6 and 234.6, respectively) each other, and about 11times higher than the control(20.9). The concentration was highest in industrial, followed by commercial and the lowest in residential areas in Seoul, while the order in Daejeon was industrial, residential and commercial areas. The Fe contents were 25716.5 in Seoul and 22838.6 in Daejeon, both being similar to the control value(22537.0). The value was highest in industrial and next in commercial areas and the lowest in residential area both in Seoul and Daejeon. The Zn contents in Seoul and Daejeon were 728.2 and 404.0, respectively, wihch were 6.3 and 3.6times higher than the control(113.3). The value was highest in commercial and next in industrial areas and the lowest in residental area in Seoul, while the order was industrial, residential and commercial areas in Daejeon. The heavy metal content was higher in the soil of main streets than that of minor streets in Seoul. The content of lead in Seoul was higher in the streets of Chongro-ku(525.9) and Chung-ku(684.8), the central area of the city which had a heavy traffic, than those in Nowon-ku(320.3) and Kwanak-ku(312.6) which had relatively less traffic crowd. The similar pattern was observed in the content of zinc; it was higher in Chongro-ku(1305.0) and Chung-ku(1335.4) than in Nowon-ku(489.1) and Kwanak-ku(569.8). In Daejeon, the contents of lead and zinc were decreasing as the distance from Daejeon Railroad Station increased : they were respectively 157.8 and 447.7 within 2km from the station, 157.6 and 235.7 with in 2-4km, and 63.5 and 156.2 within 4-6km and 58.7 and 142.2 within 6-8km. In summary, the contents of lead, copper and zinc were generally higher in the central area of the city, areas of heavy traffic and areas of industry and commerce.

• 한국국방경영분석학회지
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• 제8권1호
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• pp.99-107
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• 1982

This paper is concerned with the optimality of exponential smoothing applied to the general IMA process with different moving average and differencing orders. Numerical experiments were performed for IMA(m,n) process with various combinations of m and n, and the corresponding forecast errors were compared. Results show that the higher differencing order is more critical to the optimality of exponential smoothing, i.e., the IMA process with the higher moving average order, forecasted by exponential smoothing, has comparatively smaller forecast error. If the difference between the differencing order and the moving average order becomes larger, the accuracy of forecast by exponential smoothing declines gradually.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.216-221
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• 2004

In two dimensional incompressible flaws, a preconditioning technique called Hierarchical Iterative Procedure(HIP) has been implemented on a SUPG finite element formulation. By using the SUPG formulation, one can escape from the LBB constraint and hence achieve an equal order formulation. In this paper, we increased the order of interpolation up to cubic. The conjugate gradient squared(CGS) method is used for the outer iteration, and the HIP for the preconditioning for the incompressible Navier-Stokes equation. The hierarchical elements has been used to achieve a higher order accuracy in fluid flaw analyses, but a proper efficient iterative procedure for higher order finite element formulation has not been available so far. The numerical results by the present HIP for the lid driven cavity flaw showed the present procedure to be stable, very efficient and useful in flaw analyses in conjunction with hierarchical elements.

• 한국해양공학회지
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• 제17권5호
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• pp.11-18
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• 2003

In two-dimensional incompressible flows, a preconditioning technique called Hierarchical Iterative Procedure (HIP) has been implemented on a SUPG finite element formulation. By using the SUPG formulation, one can escape from the LBB constraint hence, achieving an equal order formulation. In this paper, we increased the order of interpolation up to cubic. The conjugate gradient squared (CGS) method is used for the outer iteration, and the HIP for the preconditioning for the incompressible Navier-Stokes equation. The hierarchical elements have been used to achieve a higher order accuracy in fluid flow analyses, but a proper and efficient iterative procedure for higher order finite element formulation has not been available, thus far. The numerical results by the present HIP for the lid driven cavity flow showed the present procedure to be stable, very efficient, and useful in flow analyses, in conjunction with hierarchical elements.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.91-98
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• 2004

In two dimensional incompressible flows, a preconditioning technique called Hierarchical Iterative Procedure(HIP) has been implemented on a stabilized finite element formulation. The stabilization has been peformed by a modified residual method proposed by Illinca et. al.[3]. The stabilization which is necessary to escape from the LBB constraint renders an equal order formulation. In this paper, we increased the order of interpolation whithin an element up to cubic. The conjugate gradient squared(CGS) method is used for the outer iteration, and the HIP for the preconditioning for the incompressible Navier-Stokes equation. The hierarchical elements has been used to achieve a higher order accuracy in fluid flow analyses, but a proper efficient iterative procedure for higher order finite element formulation has not been available so far. The numerical results by the present HIP for the lid driven cavity flow showed the present procedure to be stable, very efficient and useful in flow analyses in conjunction with hierarchical elements.