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CONSTRAINTS ON A-DECAYING COSMOLOGY FROM OBSERVATIONAL POINT OF VIEW

  • KOMIYA ZEN;KAWABATA KIYOSHI;HIRANO KOICHI;BUNYA HIROSHI;YAMAMOTO NAOTAKA
    • Journal of The Korean Astronomical Society
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    • v.38 no.2
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    • pp.157-160
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    • 2005
  • To constrain the values of the model parameters for the cosmological models involving the time-decaying $\Lambda$ term, we have computed sets of theoretical predictions for the N-m relation of galaxies as well as the CMB angular power spectrum: three types of variation, viz., ${\Lambda}{\propto} T^{-1},\;a^{-m}$, and $H^n$ are thereby assumed following Overduin & Cooperstock (1998), although we concentrate here on the discussion of the results obtained from the first type. Our results for the N-m relation indicate that the observed excess of the galaxy counts N in the faint region beyond the blue apparent magnitude 24 can be reasonably well accounted for with the value of ${\iota}$ in the range between 0.2 and 1. Furthermore, a comparison of our computational results of the CMB spectra with the observational data shows that the models with a mild degree of the $\Lambda$ term decay, viz., with the value of ${\iota}{\le}$0.4, are favorable. In this case, the age of our universe turns out to be larger than or equal to 14 Gyr, the lower limit inferred from some Uranium datings.

Fatigue Behavior of Concrete Beam Using CFRP Rebar (CFRP 보강근을 이용한 콘크리트 보의 피로거동)

  • Zhang, Pei-Yun;Kim, Okk-Yue;Cui, Xian
    • Journal of the Korea Institute of Building Construction
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    • v.19 no.6
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    • pp.495-501
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    • 2019
  • Recently, research has been carried out into the use of carbon fiber reinforced polymer (CFRP), which has good tensile strength and corrosion resistance, as an alternative to rebar. But as of yet, the research into fatigue failure of CFRP is insufficient. In this paper, an analysis was performed of the mechanical behavior and failure patterns of CFRP reinforced concrete beams according to static and cyclic loads, in order to evaluate the safety and validity of CFRP rebar as an alternative material for rebar. The cyclic load ranged from 10 % to 70% of the ultimate load, and was loaded at a speed of 3Hz using a sine wave in the form of a three-point loading method. Through the static load test, the maximum load or stiffness of the beam was found to increase remarkably with the increase of the reinforcement, but the fatigue test showed that the number of repetitions decreased and the amount of deflection increased with the increase of the reinforcement.

The Production and Spatial Heterogeneity of Litterfall in the Mixed Broadleaved-Korean Pine Forest of Xiaoxing'an Mountains, China

  • Jin, Guangze;Zhao, Fengxia;Liu, Liang;Kim, Ji Hong
    • Journal of Korean Society of Forest Science
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    • v.97 no.2
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    • pp.165-170
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    • 2008
  • Litterfall has been recognized an important part of the forest ecosystem production, playing a major pathway in energy flow and nutrient cycling through the ecosystem. This study was carried out to examine the quantity and components, temporal variation, and spatial heterogeneity of the litterfall in the mixed broadleaved-Korean pine forest. The data were collected from the 9ha permanent experimental plot, of which on the center area, i.e. $150m{\times}150m$, the total number of 319 circular litterfall traps with the size of $0.5m^2$ were established to collect falling litterfall. The results showed that the annual amount of litterfall was totalized 3,033.7 kg/ha, occupying broad-leaves of 39.3%, conifer-leaves of 29.5%, others of 18.5%, branches of 10.4%, and seeds of 2.3%. The peak point of the litterfall production was made at the end of September, proportionating 32.2% of total amount. The analysis of semivariogram revealed the existence of high spatial heterogeneity, calculated the scale of spatial heterogeneity ranged from 11.6 m to 29.1 m. The result of proportion (C/[Co+C]) showed that spatial heterogeneity of autocorrelation in total spatial heterogeneity were from 97.0% to 100%. The relatively heavy branches and others had significant differences in litterfall production between the areas of canopy gap and closed canopy in the 95% probability level, but the other components did not show statistical differences.

A Study for Developing the Competitive Swimming Suit Design with Korean Traditional Image (I) - Focused on the 5 traditional colors and Taeguk motive - (한국적 이미지의 경기용 수영복 디자인 개발에 관한 연구(I) - 오방색과 태극문을 중심으로 -)

  • 최경희;김민자
    • Journal of the Korean Society of Costume
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    • v.53 no.2
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    • pp.35-55
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    • 2003
  • The purpose of the study is to get some pieces of prior information to eventually develop competitive swimming suit designs with Korean traditional images. The study has been accomplished in following steps. First, as theoretical research, the history of swimming suit design and the requirements in designing competitive swimming suits were studied. Second, as practical research, at first, the trend of the competitive swimming suit designs in the national swimming suit market was examined. And then. the questionnaire surveys of both professional and amateur swimmers about their design preferences with purchasing and fabric-related tendencies were conducted for understanding professionals' characters more exactly. This data were analyzed through cross-analysis and multi-response analysis and x 2 was used. The results of this study can be summarized as follows : First, athletes' preferential design tendency for the swimming suit designs were examined in the aspects of style, color, pattern, logo, and accessary. In style, female athletes preferred an athletic one-piece style and male ones preferred a brief style. In color. neutral, mostly black was preferred most and cold color group like dark blue and navy blue next, regardless of sex. In addition, they preferred similar color coordination. In pattern, though solid fabrics were mostly preferred in both sexes, especially Taeguk motive were considered the most appropriate pattern to show Korean image. Besides, logo was considered importantly, and swimming caps and goggles of accessaries were generally used. Second, athletes' swimming suit purchasing tendency was as a following. the number of swimming suits possessed was more than 4 pieces. the durable period was less than 3 months. and the most important point considered in purchasing was an easy fitting for men and a design with an easy fitting for women. And most of swimming athletes preferred foreign products than domestic ones, which was attributed to excellent quality, easy fitting, and good design. and so on. Third, in fabric-related tendency, food touch, easy fitting. and opaqueness were considered importantly. and durability to chlorine, elasticity, color fastness, easy draining, lightness, and so on were demanded forward.

Effect of Boundary Layer Thickness on the Flow Around a Rectangular Prism (직사각형 프리즘 주위의 유동구조에 대한 경계층 두께의 영향)

  • Ji, Ho-Seong;Kim, Kyung-Chun;Lee, Seung-Hong;Boo, Jeong-Sook
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.6
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    • pp.893-901
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    • 2002
  • Effect of boundary layer thickness on the flow characteristics around a rectangular prism has been investigated by using a PIV(Particle Image Velocimetry) technique. Three different boundary layers(thick, medium and thin)were generated in the Atmospheric Boundary Layer Wind Tunnel at Pusan National University. The thick boundary layer having 670 mm thickness was generated by using spires and roughness elements. The medium thickness of boundary layer($\delta$=270 mm) was the natural turbulent boundary layer at the test section floor with fairly long developing length(18 m). The thin boundary layer($\delta$=36.5 mm) was generated on the smooth panel elevated 70cm from the wind tunnel floor. The Reynolds number based on the free stream velocity(3 ㎧) and the height of the model(40 mm) was 7.9$\times$10$^3$. The mean velocity vector fields and turbulent kinetic energy distributions were measured and compared. The effect of boundary layer thickness was clearly observed not only in the length of separation bubble but also in the location of reattachment point. The thinner the boundary layer thickness, the higher the turbulent kinetic energy Peak around the model roofbecame. It is strongly recommended that the height ratio between the model and the approaching boundary layer thickness should be encountered as a major parameter.

A study on the coordinates conversion procedures to activate the transformation of local into world geodetic reference system (세계측지계 전환활성화를 위한 변환방법 연구)

  • Hong, Chang-Ki;Kwon, Jay-Hyoun;Lee, Hyun-Jik;Lee, Won-Jin
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.27 no.1
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    • pp.677-682
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    • 2009
  • According to the revised law of survey, all the geographic information data including 1/1,000 digital topographic maps have to be converted to world geodetic reference system by the end of 2009. National Geographic Information Institute (NGII) formulated the policy to promote the conversion from local geodetic reference system to world geodetic reference system. However, the current conversion rate is lower than planned due to some impeding factors. Therefore, in this paper, those impeding factors are investigated and then efficient conversion strategies are established and provided. The research involves the validation of affine transformation, the determination of critical value for outlier detection and optimal number of common control points for coordinate conversion, and the treatment of old and new control points.

Development of a Windows-based Program for Discrete Event Simulation of Truck-Loader Haulage Systems in an Underground Mine (지하광산 트럭-로더 운반시스템의 이산 사건 시뮬레이션을 위한 Windows용 프로그램 개발)

  • Choi, Yosoon;Park, Sebeom;Lee, Sung-Jae;Baek, Jieun;Jung, Jihoo;Park, Han-Su
    • Tunnel and Underground Space
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    • v.26 no.2
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    • pp.87-99
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    • 2016
  • We developed a Windows-based program for discrete event simulation of truck-loader haulage systems in an underground mine. The Daesung MDI limestone mine located in Samcheok City, Gangwon Province, Korea was selected as the study area to design the program. The developed program is composed of the graphic user interface (GUI) and simulation engine implemented by Visual Basic.NET 2012 and the GPSS/H simulation language, respectively. When a user sets up input parameters for the discrete event simulation through GUI, the program activates the simulation engine, and then simulation results are displayed on GUI. This paper describes the details of the program development as well as its applications to the study area to determine the optimal number of trucks dispatched at each loading point under different operating conditions.

Axial Loading Behaviors of Square Concrete-Filled Tubular Columns with Large Width-to-Thickness Ratio Retrofitted using Carbon Fiber Reinforced Polymer Sheets(CFRP Sheets) (탄소섬유쉬트(CFRP Sheets)로 보강된 폭두께비가 큰 콘크리트 충전 각형강관 기둥의 중심축하중거동)

  • Park, Jai Woo;Yoo, Jung Han
    • Journal of Korean Society of Steel Construction
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    • v.26 no.3
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    • pp.169-176
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    • 2014
  • This paper presents the experimental results of behavior of square CFT columns with large the width-ro thickness ratio strengthened with carbon fiber reinforced polymers (CFRP) sheets subjected to concentrated axial loading. The main parameters were b/t ratio and the number of CFRP layers and 6 specimens were fabricated. The values of b/t were ranged from 60 to 100. From the tests, Maximum increase of 16% was also achieved in axial-load capacity with three transverse layered CFRP applied on four sides of steel tubes. The load capacity decreased up to 41% comparing with nominal load capacity of unstrengthened CFT column. However, for CFRP strengthened CFT, the load capacity decreased up to 32%. Finally, from the load-strain relationships, the local buckling occurred before yield point of steel tubes. Also, from the load-strain relationships, it was observed that local buckling were delayed on CFT columns by CFRP sheets retrofitting.

The Relationship between the Mental Model and the Depictive Gestures Observed in the Explanations of Elementary School Students about the Reason Why Seasons change (계절의 변화 원인에 대한 초등학생들의 설명에서 확인된 정신 모델과 묘사적 몸짓의 관계 분석)

  • Kim, Na-Young;Yang, Il-Ho;Ko, Min-Seok
    • Journal of the Korean Society of Earth Science Education
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    • v.7 no.3
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    • pp.358-370
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    • 2014
  • The purpose of this study is to analyze the relationship between the mental model and the depictive gestures observed in the explanations of elementary school students about the reason why seasons change. As a result of analysis in gestures of each mental model, mental model was remembered as "motion" in case of CM-type, and showed more "Exphoric" gestures that expressed gesture as a language. CF type is remembered in "writings or pictures," and metaphoric gestures were used when explaining some alternative concepts. CF-UM type explained with language in detail, and showed a number of gestures with "Lexical." Analyzing depictive gestures, even with sub-categories such as rotation, revolution and meridian altitude, etc., a great many types of gestures were expressed such as indicating with fingers, palms, arms, ball-point pens, and fists, etc., or drawing, spinning and indicating them. We could check up concept understandings of the students through this. In addition, as we analyzed inconsistencies among external representations such as verbal language and gesture, writing and gesture, and picture and gesture, we realized that gestures can help understanding mental models of the students, and sometimes, we could know that information that cannot be shown by linguistic explanations or pictures was expressed in gestures. Additionally, we looked into two research participants that showed conspicuous differences. One participant seemed to be wrong as he used his own expressions, but he expressed with gestures precisely, while the other participant seemed to be accurate, but when he analyzed gestures, he had whimsical concepts.

A Study on the Participatory Irrigation Management under Public Irrigation Management System (공적(公的)관리에서의 참여형 관개관리(PIM) 모델)

  • Lee, Sung-Hee;Kim, Tai-Cheol
    • Journal of The Korean Society of Agricultural Engineers
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    • v.53 no.3
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    • pp.13-17
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    • 2011
  • There was a transition from participatory irrigation management (PIM) to public irrigation management (PubIM) in Korea when Korea Rural corporation and Community (KRC) merged with Farm Land Improvement Associations (FLIAs), which had managed 60 % of irrigation areas. While making a number of achievements, some problems occurred in the public irrigation management, such as lack of farmers' participation, increased amount of water usage, and elevating operating costs. Accordingly, this paper suggested ways to increase efficiency in water usage and reduce operating costs under the public management through the motive power of farmers participation. First, WUGs replaced the discarded water management committee should be reorganized to revive the concept of PIM in the form of autonomously reinforced one and the roles and functions of WUGs and the board of representatives should be strengthened. The member of new type of WUGs should participate in the national and regional water management committees as a stakeholder of irrigation water user. And also new type of WUGs initiates not only the management of irrigation water but also the management of irrigation water quality and non-point source pollution in the watersheds. Those additional activities of WUGs should be properly compensated. Second, subsidies (direct payments) should be provided to faithful farmers as an incentive for their labor supply. Third, water fees could be charged to large scale agriculture companies. Fourth, professional managers could be hired, management targets would be adjusted, and incentives should be offered. These efforts are expected to improve the irrigation management by encouraging farmers' participation under public system.