• Title/Summary/Keyword: Light-weight material

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New Suggestion of Effective Moment of Inertia for Beams Reinforced with the Deformed GFRP Rebar (이형 GFRP Rebar로 보강된 보의 유효단면이차모멘트 산정식 제안)

  • Sim, Jong-Sung;Oh, Hong-Seob;Ju, Min-Kwan;Lim, Jun-Hyun
    • Journal of the Korea Concrete Institute
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    • v.20 no.2
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    • pp.185-191
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    • 2008
  • To fundamentally solve the problem of deterioration of concrete structures, it has been researched that the high durable concrete structure reinforced with the FRP rebar can be one of major solution to the newly-developed concrete structure. FRP rebar has lots of advantages such as non-corrosive, high performance and light weight against the conventional steel rebar. Among these kinds of FRP rebars, GFRP rebar has usually been considered as the best reinforcement because of its economic point of view. Even though the material capacity of the GFRP rebar was already investigated, there are some problems such as low modulus of elastic that will be cause for degrade of the serviceability of flexural concrete member reinforced with the GFRP rebar. Thus, the deflection characteristics of the GFRP rebar reinforced concrete structure should be considered then investigated. In this study, ACI 440 guideline (2003), ISIS Canada Design Manual (2001) and Toutanji et al. (2000) was considered for predicting the moment of inertia of the concrete beam reinforced with the GFRP rebar. And it was also evaluated that load-deflection relationship had a good accordance with the test and analysis result. In the result of this study, it could be estimated that the load-deflection relationship using the suggested equation of moment of inertia in this study indicated better accordance with the test result than that of the others until failure.

A Study on the Temperature Change of Green House using Aerogel (에어로젤을 사용한 시설하우스의 온도 변화에 대한 연구)

  • Yang, Ji-Ung;Lee, Eun-Suk;Ko, Joon-Young;Kim, Won-Kyung;Byun, Jae-Young;Park, Jin-Gyu;Choi, Won-Sik
    • Journal of the Korean Society of Industry Convergence
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    • v.23 no.6_2
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    • pp.1067-1074
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    • 2020
  • Green houses provide a more conditioned and warmer environment than the outside environment due to insulation. Currently used insulation materials include soft film (PVC, PE, EVA), foamed PE sheet, non-woven fabric, reflective film, and multi-layer insulation curtain, but there are many disadvantages and to compensate for this, silica aerogel insulation material with excellent warmth, light weight, and small volume Research using is in progress. In this study, the temperature change of the quadruple-structure green house and the temperature change in the dual-structure green house of soft film and silica airgel were investigated. The daytime temperature change was highest in A and A2 (soft film) at 10 to 16:00 after sunrise, but showed the lowest temperature at 17 to 18:00, which is the sunset time, showing the greatest change. The airgels of D and D2 showed the smallest change in temperature after sunrise and right after sunset. That is, it can be said that the airgel is hardly affected by external temperature. The temperature change at night was highest in D and D2 (aerogel) for both quadruple and dual structures. The temperature at night was measured higher in the quadruple structure than in the double structure. As for the ratio of the internal temperature to the external temperature for the quadruple structure and the double structure, D (aerogel) was not affected by the external temperature during the day in the quadruple structure and the double structure. D (Aerogel) seems to be able to reduce the damage caused by high temperatures in summer due to the high thermal insulation effect of the airgel, as the temperature rises above 4℃ at night. And in winter, it helps to save heating costs due to less heat emitted to the outside.

Analysis of Failure Behavior of FRP Rebar Reinforced Concrete Slab based on FRP Reinforced Ratio (FRP 보강근비에 따른 FRP 보강 콘크리트 슬래브의 파괴거동 분석)

  • Jang, Nag-Seop;Kim, Young-Hwan;Oh, Hong-Seob
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.5
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    • pp.173-181
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    • 2021
  • Reinforced concrete structures are exposed to various environments, resulting in reinforcement corrosion due to moisture and ions penetration. Reinforced concrete corrosion causes a decrease in the durability performance of reinforced concrete structures. One solution to mitigate such issues is using FRP rebars, which offer several advantages such as high tensile strength, corrosion resistance, and light-weight than conventional rebars, in reinforced concrete instead of conventional steel rebars. The FRP rebar used should be examined at the limit state because FRP reinforced concrete has linear behavior until its fracture and can generate excessive deflection due to the low elastic modulus. It should be considered while designing FRP reinforced concrete for flexure. In the ultimate limit state, the flexural strength of FRP reinforced concrete as per ACI 440.1R is significantly lower than the flexural strength by applying both the environmental reduction and strength reduction factors accounting for the material uncertainty of FRP rebar. Therefore, in this study, the experimental results were compared with the deflection of the proposed effective moment of inertia referring to the local and international standards. The experimental results of GFRP and BFRP reinforced concrete were compared with the flexural strength as determined by ACI 440.1R and Fib bulletin 40. The flexural strength obtained by the experimental results was more similar to that obtained by Fib bulletin 40 than ACI 440.1R. The flexural strength of ACI 440.1R was conservatively evaluated in the tension-controlled section.

Properties of Pepper growth and Yield, Cost Down with No-Tillage Organic Cultivation in Vinyl Greenhouse (시설고추 무경운 유기 재배의 생육 및 수량 특성과 생산비 절감효과)

  • Yang, Seung-Koo;Seo, Youn-Won;Son, Jang-Hwan;Park, Jong-Dae;Choi, Kyung-Ju;Jung, Woo-Jin
    • Korean Journal of Organic Agriculture
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    • v.20 no.3
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    • pp.411-422
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    • 2012
  • To investigate the possibility of sustainable agriculture in no-tillage pepper this study was carried out in vinyl greenhouse with organic cultivation having no pesticide certification. 1. Growth and yield in pepper cultivation General growth in pepper was suppressed with decreasing hill spacing, primary branch length, and stem width. Fruit diameter and fruit weight in no-tillage increased significantly, and yield of pepper increased by 10% compared with conventional tillage. From results organic cultivation in no-tillage improved a quality of pepper compared with conventional tillage. 2. Production cost of conventional tillage and no-tillage Production cost of conventional tillage and no-tillage was not different in seed cost, inorganic fertilizer cost, pesticide cost, repair cost, light agricultural tool cost, agriculture facilities depreciation cost and so on. Intermediary goods cost in no-tillage was decreased by 11% for organic fertilizer cost, light and heat expenses and power rate, heavy agricultural tool cost, and repairing expenses compare with conventional tillage. Employment effort cost and work effort cost were decreased, and farm income and farm income rate were increased by 11% and 5%, respectively, in no-tillage. In this work, yield and gross income were increased by 10% and 25%, respectively, in no-tillage. Therefore material cost, intermediary goods cost, working expensive, farm income, and income rate were increased by 34%, 3%, 2%, 52% and 22%, respectively.

THE EFFECTS OF NANO-SIZED HYDROXYAPATITE ON DEMINERALIZATION RESISTANCE AND BONDING STRENGTH IN LIGHT-CURED GLASS IONOMER DENTAL CEMENT (광중합형 글라스아이오노머 시멘트의 탈회 저항성과 결합 강도에 대한 나노미터 입자의 하이드록시아파타이트의 효과)

  • Kim, Ji-Hee;Lee, Yong-Keun;Kim, Seong-Oh;Song, Je-Seon;Choi, Byung-Jai;Choi, Hyung-Jun
    • Journal of the korean academy of Pediatric Dentistry
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    • v.37 no.1
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    • pp.24-34
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    • 2010
  • The aim of this study was to evaluate the effect of incorporated nano HA on the demineralization resistance and bonding strength of LC GIC in comparison with micro HA. Fuji II LC GIC was used as the control group and a base material for experimental groups. Two experimental groups were prepared. One was prepared by adding 15% micro HA to LC GIC by weight ratio (Exp. 1), and the other was prepared by adding 15% nano HA instead (Exp. 2). According to the results, the following conclusions could be obtained. 1. Observing under the CLSM, the control group showed thicker enamel demineralization layer than in the experimental groups, and the Exp. 2 group showed the thinnest demineralization layer. 2. In SEM analysis, there was greater enamel demineralization in the control group. The Exp. 2 group was more resistant to demineralization compared to the Exp. 1 group. 3. The bonding strength was found to be in the increasing order of control, Exp. 1, and Exp. 2 group (p < 0.05). 4. Observing the fractured surfaces under SEM after the bonding strength test was performed, there were bone-like apatite particles formed in HA-added experimental groups, and a greater number of bone-like apatite particles were formed in the Exp. 2 group compared to the Exp. 1 group.

A New Vegetable Soybean Cultivar, 'Sangwon' with Early Maturity and High Yield (풋콩용 조숙 다수성 신품종 '상원')

  • Ko, Jong-Min;Baek, In-Youl;Han, Won-Young;Kim, Hyun-Tae;Oh, Ki-Won;Shin, Sang-Ouk;Park, Keum-Yong;Ha, Tae-Jung;Shin, Doo-Chull;Chung, Myung-Geun;Kang, Sung-Taek;Yun, Hong-Tae;Oh, Young-Jin;Lee, Jong-Hyung;Son, Chang-Ki;Kim, Yong-Deuk
    • Korean Journal of Breeding Science
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    • v.42 no.6
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    • pp.684-689
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    • 2010
  • 'Sangwon', a new cultivar for vegetable soybean, was developed from the cross between 'Keunolkong' and 'Oshimamidori', and was released at the National Institute of Crop Science (NICS) in 2007. The goal to develop a vegetable soybean cultivar with green pod, early maturity, large seed size, high yield, lodging tolerance, and resistance to disease such as soybean mosaic virus (SMV). 'Sangwon' has light green pod, early maturity, large seed, short plant height, and lodging tolerance. 'Sangwon' has determinate growth habit, white flower, gray pubescence, and oval leaf shape. The matured seeds have a yellow seed coat with light brown hilum, and a yellow cotyledon. 'Sangwon' has 5.8 cm fresh pod length, 13.2mm fresh pod width, 69.5 g seed weight per 100 green seeds, 44.0% green seed protein content, and 14.8% green seed oil content. At the regional yield trials (RYT) for vegetable soybean from 2005 to 2007, 'Sangwon' shows strong resistance to soybean mosaic virus (SMV) and tolerance to lodging in fields. Fresh pods of 'Sangwon' were harvested at the beginning of August. In the same tests, fresh pod of 'Sangwon' (10.39ton/ha) yielded 5% higher than 'Hwaeomputkong' (9.90ton/ha).

The Effects of Moxifloxacin in Endotoxin-induced Acute Lung Injury (내독소로 유도된 급성폐손상에서 Moxifloxacin의 효과)

  • Baek, Jong Hyun;Lee, Jang Hoon;Lee, Jung Cheul;Lee, Dong Hyup;Moon, Yong Suk;Lee, Young Man
    • Journal of Chest Surgery
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    • v.42 no.1
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    • pp.1-8
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    • 2009
  • Background: The pathophysiology of acute respiratory distress syndrome with sepsis is acute lung injury (ALI) that's' caused by endotoxin (LPS). We evaluate effects of moxifloxacin on LPS-induced ALI in a rat model. Material and Method: The rats were divided into 3 groups as the control group (C), the LPS insult group (L), and the LPS+moxifloxacin treated group (L-M). ALI was induced by endotracheal instillation of E.coli LPS, then moxifloxacin was given in 30 minutes. Five hours later, we checked the lung weight/body weight ratio(the L/BW ratio), the protein & neutrophils in the bronchoalveolar lavage fluid (BALF), the myeloperoxidase (MPO) activity & the malondialdehyde (MDA) content, the expressions of cytosolic and secretory phospholipase $A_2$ (c, $sPLA_2$), and the morphology of the lung with using a light microscope. Result: The L/BW ratio, the protein content and the neutrophil count in the BALF, and the MPO activity and the MDA content in lung were significantly increased in group L compared to group C, and these factors were markedly decreased in group L-M compare to group L. The $cPLA_2$ expression and the $sPLA_2$ expression were increased in group L and the $cPLA_2$ expression was decreased in group L-M. Yet the $sPLA_2$ expression was not changed in group L-M. Morphologically, many inflammatory findings were observed in group L, but not in group L-M. Conclusion: Many of the inflammatory changes of ALI that were caused by LPS insult were ameliorated by moxifloxacin treatment.

Insurance system for legal settlement of drone accidents (드론사고의 법적 구제에 관한 보험제도)

  • Kim, Sun-Ihee;Kwon, Min-Hee
    • The Korean Journal of Air & Space Law and Policy
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    • v.33 no.1
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    • pp.227-260
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    • 2018
  • Recently, as the use of drones increases, the risk of drone accidents and third-party property damage is also increasing. In Korea, due to the recent increase in drone use, accidents have been frequently reported in the media. The number of reports from citizens, and military and police calls regarding illegal or inappropriate drone use has also been increasing. Drone operators may be responsible for paying damages to third parties due to drone accidents, and are liable for paying settlements due to illegal video recording. Therefore, it is necessary to study the idea of providing drone insurance, which can mitigate the liability and risk caused by drone accidents. In the US, comprehensive housing insurance covers damages caused by recreational drones around the property. In the UK, when a drone accident occurs, the drone owner or operator bears strict liability. Also, in the UK, drone insurance joining obligation depends on the weight of the drones and their intended use. In Germany, in the event of personal or material damage, drone owner bears strict liability as long as their drone is registered as an aircraft. Germany also requires by law that all drone owners carry liability insurance. In Korea, insurance is required only for "ultra-light aircraft use businesses, airplane rental companies and leisure sports businesses," where the aircraft is "paid for according to the demand of others." Therefore, it can be difficult to file claims for third party damages caused by unmanned aerial vehicles in personal use. Foreign insurance companies are selling drone insurance that covers a variety of damages that can occur during drone accidents. Some insurance companies in Korea also have developed and sell drone insurance. However, the premiums are very high. In addition, drone insurance that addresses specific problems related to drone accidents is also lacking. In order for drone insurance to be viable, it is first necessary to reduce the insurance premiums or rates. In order to trim the excess cost of drone insurance premiums, drone flight data should be accessible to the insurance company, possibly provided by the drone pilot project. Finally, in order to facilitate claims by third parties, it is necessary to study how to establish specific policy language that addresses drone weight, location, and flight frequency.

Analysis of Heat Transfer Characteristics on Multi-layer Insulating Curtains Coated with Silica Aerogel (실리카 에어로겔이 흡착된 다겹보온커튼의 전열 특성 분석)

  • Jin, Byung-Ok;Kim, Hyung-Kweon;Ryou, Young-Sun;Lee, Tae-Seok;Kim, Young-Hwa;Oh, Sung-Sik;Kang, Geum-Choon
    • Journal of Bio-Environment Control
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    • v.28 no.3
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    • pp.273-278
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    • 2019
  • The multi-layer insulating curtains used in the experiment was produced in six combinations using non-woven fabric containing aerogel and compared and analyzed by measuring heat flux and heat perfusion rates due to weight, thickness and temperature changes. Using silica aerogel, which have recently been noted as new material insulation, this study tries to produce a new combination of multi-layer insulating curtains that can complement the shortcomings of the multi-layer insulating curtains currently in use and maintain and improve its warmth, and analyze the thermal properties. The heat flux means the amount of heat passing per unit time per unit area, and the higher the value, the more heat passing through the multi-layer insulating curtain, and it can be judged that the heat retention is low. The weight and thickness of multi-layer insulation curtains were found to be highly correlated with thermal insulation. In particular, insulation curtains combined with aerogel meltblown non-woven fabric had relatively higher thermal insulation than insulation curtains with the same number of insulation materials. However, the aerogel meltblown non-woven fabric is weak in light resistance and durability, and there is a problem that the production process and aerogel are scattering. In order to solve this problems, the combination of expanded aerogel non-woven fabric and hollow fiber non-woven fabric, which are relatively simple manufacturing processes and excellent warmth, are suitable for use in real farms.

Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2016 (설비공학 분야의 최근 연구 동향 : 2016년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.29 no.6
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    • pp.327-340
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    • 2017
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.