• Title/Summary/Keyword: Energy Absorption Capacity

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A Preliminary Study on Assessment of Urban Parks and Green Zones of Ecological Attributes and Responsiveness to Climate Change (도시공원녹지의 생태성 및 기후변화 대응성 평가 기초 연구)

  • Sung, Hyun-Chan;Hwang, So-Young
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.16 no.3
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    • pp.107-117
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    • 2013
  • Problems in regard of ecological stability of urban ecosystem ensue from climate change and urbanization. Particularly, urban ecological conditions are deteriorating both quantitatively and qualitatively to a great extent. The present study aims to assess the current condition of selected sites (i. e. urban green zones and parks) in terms of preset assessment components; to find out problems and relevant solutions to improve the quality and quantity of parks and green zones; and ultimately to suggest some measures applicable to coping with climate change as well as to securing the ecological attributes of urban green zones and parks. According to the findings of this study, from quantitative perspectives, ecological attributes and responsiveness to climate change are high on account of the large natural-soil area(80%). By contrast, from qualitative perspectives including the planting structure (1 layer: 47%), the percentage of bush area(17%), the connectivity with surrounding green zones (independent types: 44%), the wind paths considered (5.6%), the tree species with high carbon absorption rates (20%), water cycles (17%), energy (8%) and carbon storage capacities(61%), ecological attributes and responsiveness to climate change were found very low. These findings suggest that the ecological values of urban parks and green zones should be improved in the future by conserving their original forms, securing natural-soil grounds and employing multi-layered planting structures and water bodies, and that responsiveness to climate change should be enhanced by planting tree species with high carbon storage capacities and obtaining detention ponds. In sum, robust efforts should be exerted in the initial planning stages, and sustained, to apply the methodology of green-zone development along with securing ecological attributes and responsiveness to climate change.

Residential Humidifying Element Made of Cellulose and PET Composite (셀룰로오스와 PET 복합체로 만들어진 가정용 가습소자)

  • Kim, Nae-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.4
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    • pp.13-18
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    • 2016
  • Humidifiers are used to control indoor humidity. Element-type humidifiers have the advantages of simple structure and low energy consumption, and Japanese products have been widely used for the humidifying elements. In this study, a new humidifying element made of cellulose and PET was developed, and the performance was compared with that of a Japanese element. The mass transfer rates and pressure drops were measured for an element installed at the entrance of a suction-type wind tunnel. The humidification efficiency of the new element was 2 to 4% greater and the pressure drop was 23 to 32% smaller compared to the Japanese element. The mass transfer effectiveness ($j_m/f$) of the new element is also 5 to 28% higher. However, the water absorption capacity was smaller than that of the Japanese element, meaning further development is needed.

Strength Analysis of Double Bottom Structures in Stranding by Idealized Structural Unit Method (이상화(理想化) 구조요소법(構造要素法)에 의한 좌초시(坐礁時) 이중저(二重底) 구조(構造)의 손상 및 강도(强度) 해석(解析))

  • Jeom-K. Paik;Chang-Y. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.28 no.1
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    • pp.125-138
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    • 1991
  • In this paper, an efficient method for the analysis of damage and strength of double bottom structure in stranding is described by using idealized structural unit method. Also a procedure for the determination of the effective double bottom height which is required in order to protect the inner-bottom plate is proposed. In the comparison between the present solution and he existing experimental and numerical results in stranding, its observed that the present method gives reasonable results requiring very shorts computiong times. The present method is then applied to the double bottom structure of 40K product oil carrier which is designed by the double skin design concept as an example. By performing the series of analysis, the influence of vertical member space, plate thickness and double bottom height on the energy absorption capacity of the double bottom structure in stranding is investigated. Also the minimum double bottom height with varying each design variable Is calculated based on the above result.

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Hysteresis Characteristics of Buckling Restrained Brace with Precast RC Restraining Elements (조립형 프리캐스트 콘크리트 보강재를 가지는 비좌굴가새의 이력특성)

  • Shin, Seung-Hoon;Oh, Sang-Hoon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.1
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    • pp.72-84
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    • 2016
  • The conventional brace system is generally accepted as the lateral load resisting system for steel structures due to efficient story drift control and economic feasibility. But lateral stiffness of the structure decreases when buckling happens to the brace in compression, so that it results in unstable structure with unstable hysteresis behavior through strength deterioration. Buckling restrained brace(BRB) system, in which steel core is confined by mortar/concrete-filled tube, represents stable behavior in the post-yield range because the core's buckling is restrained. So, seismic performance of BRB is much better than that of conventional brace system in point of energy absorption capacity, and it is applied the most in high seismicity regions as damper element. BRBs with various shaped-sections have been developed across the globe, but the shapes experimented in Korea are now quite limited. In this study, we considered built-up type of restraining member made up of precast reinforcement concrete and the steel core. we experimented the BRB according to AISC(2005) and evaluated seismic performances and hysteresis characteristics.

The Pressure Drop and Heat Transfer Characteristics of a Direct Contact 4-Stage Fluidized Bed Heat Exchanger (직접 접촉식 4단 유동층 열교환기의 압력손실 및 열전달 특성)

  • 임동렬;박상일;전광민
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.2
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    • pp.325-335
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    • 1992
  • In this work, direct contact 4-stage fluidized bed heat exchanger is experimentally studied to develop a new type of heat exchanger which recovers the energy contained in the high temperature waste gas exhausted from the industrial furnaces. A sand is used as a heat transfer medium in this experiment. To determine the optimum operating condition, 11 different perforated plates which have a different free area ratio with different hole diameter are used in the experiment. From the room temperature experiment, the pressure drop which is caused by fluidized bed formation is observed. The high temperature experiment is carried out to seek the optimum operating condition of high heat efficiency at low heat exchanger operation cost. The results of experiment are as following. The pressure drop in the high temperature condition can be predicted from the results of the room temperature experiment. And Nusselt number becomes smaller due to the increased interference between sand particles as Reynolds number increases when the dilute phase fluidized beds are formed in nigh temperature condition. But heat transfer amount through the total sand surface area become larger due to the large resident amount of sand. Considering the heat transfer amount and the heat exchanger operation cost, perforated plates which have either a 30% or 35% of free area ratio with 15mm of hole diameter are best fitted for our goal of this work. The values of .phi. which is a dimensionless number representing the absorption heat amount per unit sand rate are in the range from 0.4 to 0.5, when Reynolds number of waste gas ranges from 25-30 with these perforated plates.

The Suggestion of Seismic Performance Values on Connections for Performance Based Design of Steel Structures (강구조 성능기반설계를 위한 접합부의 내진성능평가치 제안)

  • Oh, Sang-Hoon;Oh, Young-Suk;Hong, Soon-Jo;Lee, Jin-Woo
    • Journal of Korean Society of Steel Construction
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    • v.23 no.2
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    • pp.147-158
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    • 2011
  • The purpose of this research was to analyze the connections of the seismic-performance values for domestic-performance-based designs. Basic research on the performance design method has been increasing of late, along with performance-based organization investigations. These investigations concern the performance level state of steel structure buildings. According to the performance limit state, seismic-performance values should be presented as appropriate steel structure engineering amounts. The first step, based on the full-scale steel structure experiments, involves researching on the making of a basic document. The moment-rotation angle relationship results of the experiment on the moment-frame connection were used to assort the functional and undamaged limits, which were assumed to be less than the yield moment. Moreover, the repairable and safety limits, which were assumed to exist between the yield and maximum moments, were assorted by investigating the accumulated plastic deformation ratio.

Flexural Behavior of Highly Ductile Cement Composites Mimicking Boundary Conditions of Shellfish Skin Layer (패류 껍질층의 경계면을 모방한 고연성 시멘트 복합재료의 휨 거동)

  • Kwon, Ki-Seong;Chun, Jae-Yeong;Bang, Jin-Wook;Kim, Yun-Yong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.1
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    • pp.108-115
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    • 2020
  • In this study, the flexural performance of Highly Ductile Cement Composites(HDCC) mimicking boundary conditions of shellfish skin layer was evaluated. To improve ductility by mimicking the boundary skin layer structure of shellfish, the method of stratification by charging between precast panels using HDCC and the method of distributing PE-mesh to the interface surface were applied. Evaluation of flexural performance of layered cement composite materials mimicking boundary conditions of shellfish skin layer resulted in increased ductility of all test specimens applied with stratified cross-section compared to typical bending test specimens. The layered method by inserting PE-mesh showed excellent ductility. This is most likely because the inserted PE-mesh made an interface for separating the layers while the HDCC pillars in the PE-mesh gave adhesion between layers.

Study on Crashworthiness of Icebreaker Steel: Part I Steel Properties (쇄빙선 강재의 내충격 특성에 관한 실험적 연구: 제1부 강재 특성)

  • Noh, Myung-Hyun;Lee, Jae-Yik;Park, Sung-Ju;Choung, Joonmo
    • Journal of Ocean Engineering and Technology
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    • v.30 no.4
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    • pp.268-276
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    • 2016
  • This paper presents a study on the crashworthiness of the scaled-down stiffened panels used on a Korean icebreaker. In order to validate the crashworthiness of the panels, this paper provides various mechanical properties such as the results of a CVN test, quasi-static tensile test, and high-speed tensile test at arctic temperatures. Two types of steels (EH32 and FH32) were chosen for the material tests. CVN tests revealed that the two steels were equivalent up to −60℃ in terms of their impact energy absorption capacity. However, the toughness of FH32 was significantly superior to that of EH32. EH32 showed slightly higher flow stresses at all temperature levels compared to FH32. The improvement ratios of the yield strengths, tensile strengths, plastic hardening exponents, etc. for FH32, which were obtained from quasi-static tensile tests, showed an apparent ascending tendency with a decrease in temperature. Dynamic tensile test results were obtained for the two temperatures levels of 20℃ and −60℃ with two plastic strain rate levels of 1 s−1 and 100 s−1. A closed form empirical formula proposed by Choung et al. (2011;2013) was shown to be effective at predicting the flow stress increase due to a strain rate increase.

Performance of a Refrigerant Heating Type Heat Pump by Changing of Driving Devices and Heat Exchangers (구동장치 및 열교환기 변경에 따른 냉매가열식 열펌프의 성능특성)

  • Park, Youn-Cheol;Kim, Sang-Hyuk;Kim, Ji-Young
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.1
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    • pp.49-56
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    • 2008
  • When the outdoor air temperature decreased less than the freezing temperature, frost forms at the surface of heat exchangers and it makes the performance degradation of a heat pump system. In this study, a heat pump system has been developed which has a refrigerant heating device as an auxiliarly heating equipment. To reduce power consumptions of the system, a liquid pump, rather than a compressor, was used to drive refrigerant in the heat pump cycle. Ratio of refrigerant mass flow between a refrigerant heating heat exchanger(GHX) and a outdoor plate heat exchanger(PHX) was varied and the system performance was measured and analyzed. As results, when the refrigerant flow rate to the GHX was decreased, the system performance is decreased due to heat absorption capability restriction of the GHX and small variation of the power consumption in the compressor. The effect on the evaporating and condensing pressure by the distribution ratio of the refrigerant to the each heat exchanger is small compare to the effect by the frequency change in the compressor. When the compressor was replaced by the liquid pump, the capacity of the system decreased a little, however the power consumption decrease approximately 80% compare with the power used in the compressor.

An Innovative shear link as damper: an experimental and numerical study

  • Ghamari, Ali;Kim, Young-Ju;Bae, Jaehoon
    • Steel and Composite Structures
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    • v.42 no.4
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    • pp.539-552
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    • 2022
  • Concentrically braced frames (CBFs) possess high stiffness and strength against lateral loads; however, they suffer from low energy absorption capacity against seismic loads due to the susceptibility of CBF diagonal elements to bucking under compression loading. To address this problem, in this study, an innovative damper was proposed and investigated experimentally and numerically. The proposed damper comprises main plates and includes a flange plate angled at θ and a trapezius-shaped web plate surrounded by the plate at the top and bottom sections. To investigate the damper behaviour, dampers with θ = 0°, 30°, 45°, 60°, and 90° were evaluated with different flange plate thicknesses of 10, 15, 20, 25 and 30 mm. Dampers with θ = 0° and 90° create rectangular-shaped and I-shaped shear links, respectively. The results indicate that the damper with θ = 30° exhibits better performance in terms of ultimate strength, stiffness, overstrength, and distribution stress over the damper as compared to dampers with other angles. The hysteresis curves of the dampers confirm that the proposed damper acts as a ductile fuse. Furthermore, the web and flange plates contribute to the shear resistance, with the flange carrying approximately 80% and 10% of the shear force for dampers with θ = 30° and 90°, respectively. Moreover, dampers that have a larger flange-plate shear strength than the shear strength of the web exhibit behaviours in linear and nonlinear zones. In addition, the over-strength obtained for the damper was greater than 1.5 (proposed by AISC for shear links). Relevant relationships are determined to predict and design the damper and the elements outside it.