• Title/Summary/Keyword: 내구도 평가

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Quantification of Chloride Diffusivity in Steady State Condition in Concrete with Fly Ash Considering Curing and Crack Effect (재령 및 균열효과를 고려한 플라이애시 콘크리트의 정상상태 염화물 확산 특성의 정량화)

  • Yoon, Yong-Sik;Cheon, Ju-Hyun;Kwon, Seung-Jun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.2
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    • pp.109-115
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    • 2019
  • In case of the cracks in concrete, the penetration of deterioration ions such as chloride ions in to cracks is accelerated. According to the penetration of chloride ions, structural and durability problems to RC(Reinforced Concrete) structures are caused. In this study, the accelerated chloride diffusion coefficient which is in steady state is evaluated for 2 year aged normal and high strength FA(Fly Ash) concrete, after a range of crack depths are induced up to 1.0 mm in 56 aged day. Considering crack effect by linear regression analysis, high strength concrete has slightly less increasing ratio of diffusion coefficient by crack than normal strength concrete, and diffusion coefficient increases non-linearly as crack width is increased. Also, In two types of concrete, crack effect decrease as the curing period increase. In the case of quantifying crack and curing effect by using exponential function form, the coefficients of determination are higher than those of linear regression analysis. Under steady state, it is thought that there is not a high correlation between the crack effect and the curing effect, and considering the two independent effects, it is believed that reasonable prediction equation for diffusion of concrete with crack can be proposed.

Physiochemical Characteristics and its Applicable Potential of Blast Furnace Slag Grout Mixtures of Sodium Silicate and Calcium Hydroxide (규산소다 및 수산화칼슘을 적용한 고로슬래그 그라우트의 적용성 및 물리화학적 특성)

  • Kim, Joung-Souk;Yoon, Nam-Sik;Xin, Zhen-Hua;Moon, Jun-Ho;Park, Young-Bok;Kim, Young-Uk
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.1
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    • pp.200-207
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    • 2019
  • Cement is one of the most commonly used materials in the construction and civil engineering industry. However, emissions of carbon dioxide generated during the production of cement have been linked to climate change and environment pollutants. In order to replace cement, many studies have been actively performed research to utilizing Blast Furnace Slag(BFS), which is a byproduct of the steel industry. This study aims to investigate the physiochemical properties of the BFS powder based grout to determine whether it can be used as an environment-friendly grout material. As a fine powder, BSF can be used instead of cement grout due to its potential hydraulic property. BSF has also been known for its ability to strengthen materials long-term and to densify the internal structure of concrete. In order to investigate the physicochemical properties of the BFS powder based grout as a grout material, in this study assessment tests were performed through a gel-time measurement, uniaxial compressive strength, and chemical resistance tests, and heavy-metal leaching test. Characteristics and advantages of the slag were studied by comparing slag and cement in various methods.

Power-efficiency Analysis of the MIMO-VLC System considering Dimming Control (조광제어를 고려한 MIMO-VLC 시스템의 전력 효율 분석)

  • Kim, Yong-Won;Lee, Byung-Jin;Lee, Byung-Hoon;Lee, Min-Jung;Kim, Kyung-Seok
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.18 no.6
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    • pp.169-180
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    • 2018
  • White light-emitting diodes (LEDs) are more economical than fluorescent lights, and provide high brightness, a high lifetime expectancy, and greater durability. As LEDs are closely connected with people's daily lives, dimming control of LED is an important component in providing energy savings and improving quality of life. In visible light communications systems using these LEDs, multiple input multiple output (MIMO) technology has attracted a lot of attention, in that it can attain the channel capacity in proportion to the number of antennas. This paper analyzes the power performance of three kinds of modulation in visible light communications (VLC) systems applied space-time block code (STBC) techniques. The modulation schemes are return-to-zero on-off keying (RZ-OOK), variable pulse position modulation (VPPM), and overlapping pulse position modulation (OPPM), and dimming control was applied. The power requirements and power consumption were used as metrics to compare the power efficiency in $2{\times}2$ STBC-VLC environments under the three kinds of modulation. We confirm that dimming control affects the communications performance of each modulation scheme. VPPM showed greater consumption among the three modulations, and OPPM showed energy savings comparable to VPPM.

Effect of microstructure of surface glaze on printability of ink-jet printing ceramic tile (표면 유약 미세구조가 잉크젯 프린팅 도자타일의 인쇄적성에 미치는 효과)

  • Lee, Ji-Hyeon;Hwang, Kwang-Taek;Han, Kyu-Sung;Kim, Jin-Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.28 no.6
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    • pp.243-249
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    • 2018
  • Ceramic tiles, which were manufactured through high-temperature firing process at over $1000^{\circ}C$, are widely used as interior and exterior materials for building construction due to their excellent durability and aesthetic of surface glaze. In recent years, the introduction of digital ink-jet printing in ceramic tiles for architectural use has been rapidly proceeding, and studies on the materials such as ceramic ink, ceramic pigment, glaze have been actively conducted. In this study, the effect of microstructure change of surface glaze on the printing properties of ceramic inks was investigated by micronization of kaolin, which is the raw material of surface glaze. Black ceramic ink was used for ink-jet printing on the surface glaze of ceramic tile to evaluate the printability by measuring the size and roundness of the printed ink dot. The relationship between microstructure change of surface glaze and printability of ceramic ink was also investigated by analyzing the surface roughness and internal micropore distribution of surface glaze.

Material Characteristics and Deterioration Assessment for Multi-storied Round shape Stone Pagoda of Unjusa Temple, Hwasun, Korea (화순 운주사 원형다층석탑의 재질특성과 훼손도 평가)

  • Park, Sung Mi;Lee, Myeong Seong;Kim, Jae Hwan;Lee, Chan Hee
    • Korean Journal of Heritage: History & Science
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    • v.45 no.1
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    • pp.86-101
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    • 2012
  • The constituting rocks of Multi-storied Round shape stone Pagoda of Unjusa Temple are lithic tuff and rhyolite tuff breaccia which show green or grey and also rock fragment with poor roundness are present in the structure. lithic tuff is composed of feldspar and quartz which are glassy texture and cryptocrystalline and also micro crystalline are scattered. phenocryst quartz and feldspar in the substrate composed of feldspar and opaque minerals are found in rhyolite tuff breaccia. dust, exfoliation, cavity, fracture and crack are observed in all the stone of the pagoda and the result of Infrared Thermography shows partial inter cavities have developed severely which may cause further exfoliation. In addition, a great deal of various grey, green, and yellow brown lichen as well as bryophyte are present at the upper part of eastern and western roof stone located above the third floor. Discolors remarkably shown at stereobate and roof stone are identified as inorganic pollutants such as manganese oxide, iron oxide and iron hydroxide. The stone of the pagoda of the Chemical Index of Alteration (CIA) and the Weathering Potential Index (WPI) are 55.69 and 1.12 respectively and this corresponds to a highly weathered stage. The measured values, average ultrasonic velocity 2,892m/s, coefficient of weathering 0.4k and compressive strength $1,096kg/cm^3$, suggest that the rock strength and durability are weakened.

A Study on the Development of Sleep Monitoring Smart Wear based on Fiber Sensor for the Management of Sleep Apnea (수면 무호흡증 관리를 위한 섬유센서 기반의 슬립 모니터링 스마트 웨어 개발에 관한 연구)

  • Park, Jin-Hee;Kim, Joo-Yong
    • Science of Emotion and Sensibility
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    • v.22 no.1
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    • pp.89-100
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    • 2019
  • Sleep apnea, a medical condition associated with a variety of complications, is generally monitored by standard sleep polysomnography, which is expensive and uncomfortable. To overcome these limitations, this study proposes an unconstrained wearable monitoring system with stretch-fiber sensors that integrate with the wearer's clothing. The system allows patients to undergo examinations in a familiar environment while minimizing the occurrence of skin allergies caused by adhesive tools. As smart clothing for adult males with sleep apnea, long-sleeved T-shirts embedding fibrous sensors were developed, enabling real-time monitoring of the patients' breathing rate, oxygen saturation, and airflow as sleep apnea diagnostic indicators. The gauge factor was measured as 20.3 in sample 4. The maximum breathing intake, measured during three large breaths, was 2048 ml. the oxygen saturation was measured before and during breath-holding. The oxygen saturation change was 69.45%, showing a minimum measurable oxygen saturation of 70%. After washing the garment, the gauge factor reduced only to 18.0, confirming the durability of the proposed system. The wearable sleep apnea monitoring smart clothes are readily available in the home and can measure three indicators of sleep apnea: respiration rate, breathing flow and oxygen saturation.

Measuring Willingness to Pay for PM10 Risk Reductions: Evidence from Averting Expenditures for Anti-PM10 Masks and Air Purifiers (미세먼지 건강위험 감소에 대한 지불의사 측정: 마스크 착용과 공기청정기 사용에 따른 회피비용을 중심으로)

  • Eom, Young Sook;Kim, Jin Ok;Ahn, So Eun
    • Environmental and Resource Economics Review
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    • v.28 no.3
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    • pp.355-383
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    • 2019
  • This study is to investigate whether averting costs for wearing $anti-PM_{10}$ masks and using air purifiers at home to reduce exposure from $PM_{10}$ are influenced by subjective risk perceptions and/or objective $PM_{10}$ concentration levels, whose estimates will be used to measure the willingness to pay for $PM_{10}$ risk reduction. An empirical analysis was conducted on a sample of 1,224 respondents who participated in the web-based survey in the late October of 2017. As we reflect the potential endogeniety bias in the estimation of averting cost functions of using air purifiers, the coefficients of risk perception were differed by 6~7 times. Respondents. subjective risk perceptions were influenced by individuals' knowledge, attitudes and demographic variables, as well as the levels of $PM_{10}$ concentrations in their residential region. The marginal willingness to pay for risk reductions at the mean levels of their risk perceptions were measured at 1,000 won per month from wearing $anti-PM_{10}$ masks and 6,000 won for using air purifiers respectively.

Analysis of Equivalent Torque of 78 kW Agricultural Tractor during Rotary Tillage (78 kW급 농업용 트랙터의 로타리 경운 작업에 따른 등가 토크 분석)

  • Baek, Seung-Min;Kim, Wan-Soo;Park, Seong-Un;Kim, Yong-Joo
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.12 no.4
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    • pp.359-365
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    • 2019
  • This paper is a basic study for the performance evaluation, durability improvement and optimal design of tractor transmission. The engine torque of the 78 kW agricultural tractor during rotary tillage was measured using CAN communication. It was calculated with equivalent torque and then analyzed. In order to develop a reliable tractor, it is important to convert measured torque in various agricultural operations into equivalent torque and analyze it. The equivalent torque was calculated using Palmgren-Miner's rule, which is a representative cumulative damage law. The equivalent torque of rotary tillage period and steering period are 229.2 and 136.7 Nm, respectively. The maximum and average torque during rotary tillage period are 336.0 and 234.4 Nm, respectively. The maximum and average torque of the steering period are 288.0 and 134.6 Nm, respectively. The engine torque in rotary tillage period is higher than in the steering period because of cultivation of soil through PTO. The maximum and rated torque of engine are 387.0 and 323.0 Nm, respectively, which are 183% and 136% higher than the equivalent torque during rotary tillage and of steering section. Because transmission of agricultural tractor in Korea companies is generally designed by the rated torque of engine, there is a difference from measured torque during agricultural operations. Therefore, it is necessary to consider it for optimal design.

Development of Environmental Safety Real-Time Monitoring System by Living Area (생활권역별 환경안전 실시간 모니터링 시스템의 개발)

  • Lee, Joo-Hyun;Kim, Joo-Ho;Lee, Seung-Ho
    • Journal of IKEEE
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    • v.23 no.3
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    • pp.1088-1091
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    • 2019
  • In this paper, a real-time monitoring system for environmental safety by living area is proposed. The proposed system is designed to measure radiation, fine dust and basic living information (temperature) using fixed and mobile measuring equipment, and constitutes a web database that stores data received from the equipment. It also develops web programs for displaying received data on PCs and mobile phones. The results of testing the performance of the system by an authorized testing agency showed that the radiation measurement range was measured in the range of $10{\mu}Sv/h$ to 10mSv/h, which is comparable to the world's highest level, and that the accuracy was measured between ${\pm}6.7$ and ${\pm}8.7$ percent of the measurement uncertainty was measured and normal operation at or below the international standard of ${\pm}15$ percent. In addition, the temperature test was conducted on a section of $-20^{\circ}C$ to $50^{\circ}C$ and normal operation was confirmed in response to the temperature change. Stability of radiated electromagnetic waves was ensured by a suitable judgment. The product's testing in general and high and low temperature environments for about four months after the prototype was made confirmed to be more than five years of durability. The measurement range and accuracy of fine dust sensors are compared with those of companies that measure the air environment, and the performance level is similar through the air quality measurement register.

A Study on Performance of Steel Monocell Expansion Joints (강재형 모노셀 신축이음장치 성능 연구)

  • Kim, Yong-Hoon;Yhim, Sung-Soon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.5
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    • pp.502-509
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    • 2019
  • Studies have been made on performance evaluation of expansion joint systems for an ordinary highway or road bridge. However little study has been made for runway connection bridges at airports. A study on performance evaluated from computer code analysis and shrinkage, extension, and compression repetition tests based on KS F 4425 is conducted to a newly developed expansion joint system which has been installed in a runway connection bridge at Incheon Airport Extension 2 Construction Site. The MIDAS computer code is used to analyze the performance before the manufacture of the mock-up of expansion joint system on the basis of design requirements. Tests based on the KS F 4425 of 2001 year-version are conducted for the mock-up. Domestic codes and standards to validate the performance of the expansion joint system in a connection bridge have been developed for a vehicle. However the expansion joint system tested in this study is installed in a runway connection bridge for an aircraft. Conservatively the heaviest one among airplanes departing and landing at Incheon Airport is assumed level-F $468.4kN/m^2$ and adopted for the tests and analyses in this study. KS F 4425 method is selected for the shrinkage, extension, and compression repetition tests. No remarkable problem was observed for the 2,500-cycle shrinkage and extension and two million-cycle repeatition load tests. The results of this study are expected to contribute to establishment of code and standard for the performance validation of an expansion joint system installed in a runway connection bridge for an aircraft by providing performance test results and computer analysis results based on finite element methods.