• Title/Summary/Keyword: strength loss

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RSSI-based Indoor Location Tracking System using Wireless Sensor Networks (무선 센서 네트워크를 이용한 RSSI 기반의 실내 위치 추적 시스템)

  • Jung, Kyung-Kwon;Park, Hyun-Sik;Choi, Woo-Seung
    • Journal of the Korea Society of Computer and Information
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    • v.13 no.7
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    • pp.67-73
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    • 2008
  • This paper describes a system for location tracking wireless sensor nodes in an indoor environment. The sensor reading used for the location estimation is the received signal strength indication (RSSI) as given by an RF interface. By tagging users with a mobile node and deploying a number of reference nodes at fixed position in the room, the received signal strength indicator can be used to determine the position of tagged users. The system combines Euclidean distance technique with signal strength obtained by measurement driven log-normal path loss model of 2.4 GHz wireless channel. The experimental results demonstrated the ability of this system to estimate the location with a error less than 1.3m.

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A Study on Physical Properties of Mortar Using Shrinkage Reducing Agent (수축저감제를 사용한 모르터의 물성에 관한 연구)

  • 이승한;이종석;이순환
    • Proceedings of the Korea Concrete Institute Conference
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    • 1995.10a
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    • pp.103-107
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    • 1995
  • The intention of this study is to reduce the drying shrinkage of the cement mortar using the shrinkage reducing agent and the inorganic admixture. In this experiment the drying shrinkage strain, rate of weight loss and strength have been measured depending on age using the motar specimen. The result show that the usage of shrinkage reducing agent up to 1.5% will give an effect of approximately 30% without loss of strength, and the efficiency will increase together with the inorganic admixture. Also, as the amount of shrinkage reducing agent increases, the rate of weight loss increases. Drying shrinkage reduces at the same rate of weight loss.

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Modification of Wool Fiber by Enzymatic Treatment (I) (효소처리에 의한 양모섬유의 개질 (I))

  • Park, Jung-A;Park, Jeoung-Young;Lim, Yong-Jin
    • Textile Coloration and Finishing
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    • v.3 no.4
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    • pp.7-12
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    • 1991
  • Wool gabardines were treated with alkaline proteases, and their tensile strerigth and dyeing behavior were obtained. Enzylon ASA 30 and Alcalase 2.5L DX did not show much effect on the weight loss of wool, but Esperase 8.0L decreased the weight of wool to a great extent. Pretreatment of wool with dichloroisocyarturic acid before protease-treatment increased the weight loss of wool considerably. Weight loss was accompanied by serious strength decrease and the use of sodium sulfate in the protease-treatment had not effect on the strength retention, only lowering the weight loss of wool. Protease-treatment of wool increased dyeability considerably, which may be due to the change in the inner structure of wool fiber by protease.

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Rebar corrosion effects on structural behavior of buildings

  • Yuksel, Isa
    • Structural Engineering and Mechanics
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    • v.54 no.6
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    • pp.1111-1133
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    • 2015
  • Rebar corrosion in concrete is one of the main causes of reduction of service life of reinforced concrete buildings. This paper presents the influence of rebar corrosion on the structural behavior of reinforced concrete (RC) buildings subjected to strong earthquake ground motion. Different levels of rebar corrosion scenarios were applied on a typical four story RC frame. The deteriorated conditions as a result of these scenarios include loss in cross-sectional area and loss of mechanical properties of the reinforcement bars, loss in bond strength, and loss in concrete strength and its modulus of elasticity. Dynamic analyses of the frame with different corrosion scenarios are performed with selected strong earthquake ground motion records. The influences of degradation in both concrete and reinforcement on structural behavior are investigated by comparing the various parameters of the frame under different corrosion scenarios with respect to each other. The results show that the progressive deterioration of the frame due to rebar corrosion causes serious structural behavior changes such as change in failure mode. The intensity, propagation time, and extensity of rebar corrosion have very important effects on the level of degradation of steel and concrete, as well as on the earthquake behavior of the structure.

hydration of the Fly Ash-CaO System in the Presence of Various Chemical Activators (화학 활성화제에 의한 플라이애쉬-생석회계의 수화반응)

  • 송종택;김재영;류동우;고상렬;한경섭
    • Journal of the Korean Ceramic Society
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    • v.35 no.2
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    • pp.185-195
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    • 1998
  • This experiment carried out in order to investigate the effect of the chemical activators for acceleration of hydration the system of Fly ash-Cao The paste was consisted of 80wt% Fly ash and 20wt% CaO with 1. 3. 5wt% of 4 activators(N{{{{ alpha _2 }}S{{{{ OMICRON _4 }}, CaC{{{{ {l }_{2 } }}, NaOH, Ca(N{{{{ OMICRON _3 {)}_{2 } }} and W/S ratio of 0.42 After curing for 1, 3, 7, 14, 28 days the paste hydration was characterized by the measurement of compressive strength XRD analysis SEM observation the combined water and the reaction amount of Ca(OH)2 determination. As a result of this ex-periment all of the system which involved Na2SO4 or NaOH had a god compressive strength. In the case of 7 days curing a system which added CaCl2 showed the highest compressive strength among all especially NaOH system showed a high increase in strength as a dosage of it increased. Hydration products were different according to activatores added. Only C-S-H was observed in NaOH system. As the reaction amount of Ca(OH)2 and combined water were increased the compressive strength increased. There were few differences in the comparision of strength between ignited loss 3.1% and loss 9.3% of fly ash.

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Assessment of Shear Strength Parameter for Weathered Soils Using Artificial Neural Network (인공신경망을 이용한 풍화토의 강도정수 산정)

  • Lee, Moo-Cheol;Lee, Song
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.3
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    • pp.147-154
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    • 2008
  • Weathered soil slope loses its shear strength if it is exposed in the air for a long time or in contact with water. And this kind of strength loss is remarkable in dam slope which has very big difference in water level according to the season. In this study, shear strength loss of weathered soil due to saturation had been found out through dryness and wetness repetition direct shear test. Also relation between penetration blow number(Nc) and shear strength parameter had been found out through small sized dynamic cone penetration test device and the correlation equation of Nc had been proposed through artificial neural network analysis to estimate shear strength parameter easily.

Effect of fly ash and GGBS combination on mechanical and durability properties of GPC

  • Mallikarjuna Rao, Goriparthi;Gunneswara Rao, T.D.
    • Advances in concrete construction
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    • v.5 no.4
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    • pp.313-330
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    • 2017
  • Geopolymer is a sustainable concrete, replaces traditional cement concrete using alternative sustainable construction materials as binders and alkaline solution as alkaline activator. This paper presents the strength characteristics of geopolymer concrete (GPC) developed with fly ash and GGBS as binders, combined Sodium silicate ($Na_2SiO_3$) and Sodium Hydroxide (NaOH) solution as alkaline activators. The parameters considered in this research work are proportions of fly ash and GGBS (70-30 and 50-50), curing conditions (Outdoor curing and oven curing at $600^{\circ}C$ for 24 hours), two grades of concrete (GPC20 and GPC50). The mechanical properties such as compressive strength, split tensile strength and flexural strength along with durability characteristics were determined. For studying the durability characteristics of geopolymer concrete 5% $H_2SO_4$ solutions was used and the specimens were immersed up to an exposure period of 56 days. The main parameters considered in this study were Acid Mass Loss Factor (AMLF), Acid Strength Loss Factor (ASLF) and products of degradation. The results conclude that GPC with sufficient strength can be developed even under Outdoor curing using fly ash and GGBS combination i.e., without the need for any heat curing.

An Experimental Study on Alkali-Silicate Reaction of Fiber Reinforced Concrete Containing Waste Glass (폐유리를 혼입한 섬유보강 콘크리트의 알카리-실리카 반응에 관한 실험적 연구)

  • Lee, Bong-Chun;Lee, Taek-Woo;Kwon, Hyuk-Joon;Lee, Jun;Park, Seung-Bum
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.05a
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    • pp.49-54
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    • 2001
  • Using waste glass in concrete can cause crack and strength loss by the expansion of alkali-silica reaction(ASR). In this study, ASR expansion and properties of strength were analyzed in terms of brown waste glass content, and fibers(steel fiber, polypropylene fiber) and fiber content for reduction ASR expansion due to waste glass. In this accelerated ASTM C 1260 test of waste glass, pessimum content can not be found. Also, when used the fibers with waste g1ass, there is an effect on reduction of expansion and strength loss due to ASR between the alkali in the cement paste and the silica in the waste glass. Specially, adding 1.5 vol.% of steel fiber to 20% of waste glass the expansion ratio was reduced by 40% and flexural strength was developed by up to 110% comparing with only Waste glass ( $80^{\circ}C$ $H_{2}$ O curing).

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A Study on the Properties of High Fluidity Concrete Incorporating Lime Stone Powder and Fly Ash (석회석 미분말 및 플라이애쉬 치환율 변화에 따른 고유동 콘크리트의 특성에 관한 연구)

  • 조병영;윤길봉;황인성;한민철;윤기원;한천구
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.287-292
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    • 2001
  • This paper investigates the properties of high fluidity concrete incorporating lime stone powder and fly ash. Lime stone powder(LSP) and fly ash(FA) contents are varied with. According to test results, as LSP and FA contents increase, fluidity, air content and placeability shows a declining tendency. For the temperature history, both LSP and FA have favorable effects on reducing hydration heat, moreover, LSP reduces hydration heat more than FA. LSP shows undesirable strength loss as its content increases. FA also decreases the strength at early age, but it enhances later age strength. Accordingly LSP is expected to improve the quality at fresh concrete and reduce hydration heat, while it causes strength loss.

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Study on the field application according to the early strength of the concrete admixed with polycarboxylate superplasticizer (폴리카본산계 고성능감수제를 이용한 콘크리트의 초기강도에 따른 현장적용성 연구)

  • Lee Jin Woo;Kim Kyung Min;Bae Yeoun Ki;Lee Jae Sam
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.05a
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    • pp.200-203
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    • 2004
  • In this study, it is examined the properties of flow and early strength of concrete according to superplasticizer. For this experiment, it is analyzed that the flow and strength properties according to the mixture factors, compared with naphthalene superplasticizer(normal & delay type) focused on polycarboxylate superplasticizer. (1) The slump loss of concrete used polycarboxylate superplasticizer showed $4\~8cm$, it is judged that slump loss according to the time lapse can be minimized. (2) The performance of polycarboxylate superplasticizer is about $70\%$ level of the normal naphthalene type, it is superior to the delay type, but the performance showed so lowly. The 28days, early strength didn't differ according to the kind of superplasticizer.

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