• Title/Summary/Keyword: 부착모델

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Mechanical Properties of Strain Hardening Cement-Based Composite (SHCC) with Recycled Materials (자원순환형 재료를 사용한 변형경화형 시멘트 복합체(SHCC)의 역학적 특성)

  • Kim, Sun-Woo;Cha, Jun-Ho;Kim, Yun-Yong;Yun, Hyun-Do
    • Journal of the Korea Concrete Institute
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    • v.22 no.5
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    • pp.727-736
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    • 2010
  • This paper describes results of an preliminary study to produce strain hardening cement-based composites (SHCCs)with consideration of sustainability for infrastructure applications. The aims of this study are to evaluate the influence of recycled materials on the mechanical characteristics of SHCCs, such as compressive, four-point bending, and direct tensile behaviors, and to give basic data for constitutive model for analyzing and designing infra structures with SHCCs. In this study, silica sand, cement, and PVA fibers, were partially replaced with recycled sand, fly-ash, and FET fibers in the mixture of SHCCs, respectively. Test results indicated that fly-ash could improve both bending and direct tensile performance of SHCCs due to increasing chemical bond strength at the interface between PVA fibers and cement matrices. However, SHCCs replaced with PET fibers showed much lower performance in bending and direct tensile tests due to originally low mechanical properties of own fibers, although compressive behavior is similar to PVA2.0 specimen. Also, it was noted that the recycled sand would increase elastic modulus of SHCCs due to larger grain size compared to silica sand. Based on pre-set target value to maintain the performance of SHCCs, it was concluded that the replacement ratio below 20% of fly-ash or below 50% of recycled sands would be desirable for creating sustainable SHCCs.

Evaluation of Interlayer Shear Properties and Bonding Strengths of a Stress-Absorbing Membrane Interlayer and Development of a Predictive Model for Fracture Energy (덧씌우기 응력흡수층에 대한 전단, 부착강도 평가 및 파괴에너지 예측모델 개발)

  • Kim, Dowan;Mun, Sungho;Kwon, Ohsun;Moon, Kihoon
    • International Journal of Highway Engineering
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    • v.20 no.1
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    • pp.87-95
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    • 2018
  • PURPOSES : A geo-grid pavement, e.g., a stress-absorbing membrane interlayer (SAMI), can be applied to an asphalt-overlay method on the existing surface-pavement layer for pavement maintenance related to reflection cracking. Reflection cracking can occur when a crack in the existing surface layer influences the overlay pavement. It can reduce the pavement life cycle and adversely affect traffic safety. Moreover, a failed overlay can reduce the economic value. In this regard, the objective of this study is to evaluate the bonding properties between the rigid pavement and a SAMI by using the direct shear test and the pull-off test. The predicted fractural energy functions with the shear stress were determined from a numerical analysis of the moving average method and the polynomial regression method. METHODS : In this research, the shear and pull-off tests were performed to evaluate the properties of mixtures constructed using no interlayer, a tack-coat, and SAMI with fabric and without fabric. The lower mixture parts (describing the existing pavement) were mixed using the 25-40-8 joint cement-concrete standard. The overlay layer was constructed especially using polymer-modified stone mastic asphalt (SMA) pavement. It was composed of an SMA aggregate gradation and applied as the modified agent. The sixth polynomial regression equation and the general moving average method were utilized to estimate the interlayer shear strength. These numerical analysis methods were also used to determine the predictive models for estimating the fracture energy. RESULTS : From the direct shear test and the pull-off test results, the mixture bonded using the tack-coat (applied as the interlayer between the overlay layer and the jointed cement concrete) had the strongest shear resistance and bonding strength. In contrast, the SAMI pavement without fiber has a strong need for fractural energy at failure. CONCLUSIONS : The effects of site-reflection cracking can be determined using the same tests on cored specimens. Further, an empirical-mechanical finite-element method (FEM) must be done to understand the appropriate SAMI application. In this regard, the FEM application analy pavement-design analysis using thesis and bonding property tests using cored specimens from public roads will be conducted in further research.

Analysis of the particulate matters in the vertical-flow woodchip wetland treating stormwater from paved road (포장도로 강우유출수 처리목적의 수직흐름형 우드칩 충진 습지에서 입자상 물질분석)

  • Yuan, Qingke;Kim, Youngchul
    • Journal of Wetlands Research
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    • v.20 no.2
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    • pp.145-154
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    • 2018
  • In this study, three pilot-scale wetland systems were built for treating stormwater runoff from asphalt road. Each of the system consists of a settling tank and a vertical flow wetland packed with 25%, 50%, and 75% woodchip as treatment media. According to the analysis of the distributions of particle size, it was found that solids ranging in size $0.52-30{\mu}m$ were predominant in the stormwater runoff. After 24-hours settling, those coarser than $20{\mu}m$ were significantly detained. Further retention, especially for the finer-sized fraction, occurred in the wetland through internal recirculation during the dry day periods. As a primary media of the wetland, woodchip showed a high filtration and attachment capacity for the particulates in pre-settled stormwater, whereas overall amount of solids in the wetland effluent increased due to the detachment of woody elements from the media. This was observed mainly during the initial 75 days of operation, and the size and detachment rate were found to be strongly related with the woodchip packing ratio. The mechanism involving woody particle detachment was modeled as a first-order form. In addition, water quality factors and operational parameters affecting the detachment were analyzed and discussed.

Evaluation of Low-cost MEMS Acceleration Sensors to Detect Earthquakes

  • Lee, Jangsoo;Kwon, Young-Woo
    • Journal of the Korea Society of Computer and Information
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    • v.25 no.5
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    • pp.73-79
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    • 2020
  • As the number of earthquakes gradually increases on the Korean Peninsula, much research has been actively conducted to detect earthquakes quickly and accurately. Because traditional seismic stations are expensive to install and operate, recent research is currently being conducted to detect earthquakes using low-cost MEMS sensors. In this article, we evaluate how a low-cost MEMS acceleration sensor installed in a smartphone can be used to detect earthquakes. To this end, we installed about 280 smartphones at various locations in Korea to collect acceleration data and then assessed the installed sensors' noise floor through PSD calculation. The noise floor computed from PSD determines the magnitude of the earthquake that the installed MEMS acceleration sensors can detect. For the last few months of real operation, we collected acceleration data from 200 smartphones among 280 installed smartphones and then computed their PSDs. Based on our experiments, the MEMS acceleration sensor installed in the smartphone is capable of observing and detecting earthquakes with a magnitude 3.5 or more occurring within 10km from an epic center. During the last several months of operation, the smartphone acceleration sensor recorded an earthquake of magnitude 3.5 in Miryang on December 30, 2019, and it was confirmed as an earthquake using STA/LTA which is a simple earthquake detection algorithm. The earthquake detection system using MEMS acceleration sensors is expected to be able to detect increasing earthquakes more quickly and accurately.

A Distributed address allocation scheme based on three-dimensional coordinate for efficient routing in WBAN (WBAN 환경에서 효율적인 라우팅을 위한 3차원 좌표 주소할당 기법의 적용)

  • Lee, Jun-Hyuk
    • Journal of Digital Contents Society
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    • v.15 no.6
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    • pp.663-673
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    • 2014
  • The WBAN technology means a short distance wireless network which provides each device interactive communication by connecting devices inside and outside of body. Standardization on the physical layer, data link layer, network layer and application layer is in progress by IEEE 802.15.6 TG BAN. Wireless body area network is usually configured in energy efficient using sensor and zigbee device due to the power limitation and the characteristics of human body. Wireless sensor network consist of sensor field and sink node. Sensor field are composed a lot of sensor node and sink node collect sensing data. Wireless sensor network has capacity of the self constitution by protocol where placed in large area without fixed position. In this paper, we proposed the efficient addressing scheme for improving the performance of routing algorithm by using ZigBee in WBAN environment. A distributed address allocation scheme used an existing algorithm that has wasted in address space. Therefore proposing x, y and z coordinate axes from divided address space of 16 bit to solve this problems. Each node was reduced not only bitwise but also multi hop using the coordinate axes while routing than Cskip algorithm. I compared the performance between the standard and the proposed mechanism through the numerical analysis. Simulation verified performance about decrease averaging multi hop count that compare proposing algorithm and another. The numerical analysis results show that proposed algorithm reduced the multi hop better than ZigBee distributed address assignment

Natural Convection in a Water Tank with a Heated Horizontal Plate Facing Downward (아래로 향한 수평가열판이 있는 수조에서의 자연대류)

  • Yang, Sun-Kyu;Chung, Moon-Ki;Helmut Hoffmann
    • Nuclear Engineering and Technology
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    • v.27 no.3
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    • pp.301-316
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    • 1995
  • experimental and computational studies ore carried out to investigate the natural convection of the single phase flow in a tank with a heated horizontal plate facing downward. This is a simplified model for investigations of the influence of a core melt at the bottom of a reactor vessel on the thermal hydraulic behavior in a oater filled cavity surrounding the vessel. In this case the vessel is simulated by a hexahedron insulated box with a heated plate Horizontally mounted at the bottom of the box. The box with the heated plate is installed in a water filled hexahedron tank. Coolers are immersed in the U-type water volume between the box and the tank. Although the multicomponent flows exist more probably below the heated plate in reality, present study concentrates on the single phase flow in a first step prior to investigating the complicated multicomponent thermal hydraulic phenomena. In the present study, in order to get a better understanding for the natural convection characteristics below the heated plate, the velocity and temperature are measured by LDA(Laser Doppler Anemometry) and thermocouples, respectively. And How fields are visualized by taking pictures of the How region with suspended particles. The results show the occurrence of a very effective circulation of the fluid in the whole How area as the heater and coolers are put into operation. In the remote region below the heated plate the new is nearly stagnant, and a remarkable temperature stratification can be observed with very thin thermal boundary. Analytical predictions using the FLUTAN code show a reasonable matching of the measured velocity fields.

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Seismic Performance of Concrete-Filled Steel Piers Part I : Quasi-Static Cyclic Loading Test (강합성교각의 내진성능평가 Part I : 준정적 반복재하실험)

  • 조창빈;서진환;장승필
    • Journal of the Earthquake Engineering Society of Korea
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    • v.6 no.2
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    • pp.9-19
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    • 2002
  • Steel piers and concrete-filled steel(CFS) piers, in spite of reasonable strength, high ductility, small section, and fast construction, have not been considered as one of alternatives to RC piers even in the highly populated urban area where aseismic safety, limited space and fast construction are indispensably required. This paper, the first of two companion papers for the seismic performance of steel and CFS piers, tests steel and CFS piers under quasi-static cyclic loading to estimate their ductility and strength. Additional details such as rebars and base ribs are added to increase the ductility of a concrete-filled steel pier with minimum additional cost. Also, simplified numerical analyses using nonlinear spring and shell elements are examined for the estimation of the ductility and strength of concrete-filled steel piers and a steel pier. The result shows that concrete-filled steel peirs have higher energy absorption, i.e., ductility and strength than those of steel pier and increasing bonding between in-filled concrete and lower diaphragm, and the improved details of stress concentrated region would be important for the ductility and strength of a pier. Numerical results show that simplified modeling with nonlinear springs and shells has potential to be effective modeling technique to estimate the seismic performance of a concrete-filled steel pier.

Effect of Hydrosalpingeal Fluid on the Implantation in-vitro in a Murine Model (생쥐 배아의 체외배양 시 착상과정에 대한 난관수종액의 영향)

  • Jun, Jin-Hyun;Koong, Mi-Kyoung;Lim, Chun-Kyu;Kim, Soo-Kyung;Kang, Inn-Soo
    • Clinical and Experimental Reproductive Medicine
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    • v.27 no.2
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    • pp.159-164
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    • 2000
  • 연구목적:인간의 체외수정 및 배아이식술에서 난관수종을 갖는 환자에서 임신율과 착상률이 감소된다는 보고들이 있지만 이에 대한 명확한 기작은 밝혀지지 않았다. 본 연구에서는 생쥐 배아를 이용한 체외 착상모델에서 인간의 난관수종액(HSF)이 착상과정에 미치는 영향을 알아보고자 하였다. 연구재료 및 방법 난관수종액은 난관수종으로 수술을 받은 8명의 환자로부터 채취하였으며, 실험에 사용하기 전까지 냉동고에 보관하였다. 생쥐의 포배기 배아는 2-세포기배아를 3일 동안 배양하여 그 중 상태가 양호한 포배기 배아만을 선별하여 투명대를 제거한 후 사용하였다. 기본 배양액으로는 Ham's F-10을 사용하였으며, 배양 시 기본 배양액만을 사용한 경우를 group Ⅰ으로 하였고, 기본 배양액에 0.5% FBS를 첨가한 경우를 group Ⅱ, 0.5% FBS와 50% HSF를 첨가한 경우를 group Ⅲ , 100% HSF에 0.5% FBS를 첨가한 경우를 group Ⅳ,100% HSF만을 사용한 경우를 group Ⅴ로 하였다. 투명대를 제거한 포배기 배아를 각각의 HSF에 대한 5종류의 배양액에서 48시간 동안 배양하였다. 체외 착상 유무는 부착 부위에서 크기가 커진 영양세포들을 관찰하여 판정하였으며, 착상 부위의 표면적은 화상분석기를 이용하여 산출하였다. 결 과: 생쥐 배아의 체외 착상률은 group Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ에서 각각 0%, 98.9%, 77.5%, 40.4%, 10.0%로 나타났으며, 착상 부위의 평균 표면적은 group Ⅱ, Ⅲ, Ⅳ, Ⅴ에서 각각 $74,675{\pm}25,201{\mu}m^2$, $59,024{\pm}25,877{\mu}m^2$, $45,156{\pm}22,654{\mu}m^2$, $38,254{\pm}17,115{\mu}m^2$이었다. 체외 착상률과 부위의 표면적은 HSF의 농도가 증가함에 따라 통계적으로 유의하게 감소하였다(p<0.001). 결론:인간의 난관수종액(HSF)은 생쥐 배아의 체외 착상과 영양배엽세포의 증식을 억제하는 것으로 확인되었으며, 이러한 원인이 난관수종을 갖는 환자에서 임신율이 낮은 것과 밀접한 관련이 있을 것으로 생각된다.

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Scattering Characteristic from Building Walls with Periodic and Random Surface (규칙적 또는 불규칙적 구조를 가지는 빌딩벽면에서의 전자파 산란 특성)

  • 윤광렬
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.4
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    • pp.428-435
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    • 2004
  • With the rapid and wide-spread use of cellular telephones much attention has been focussed on propagation in the urban area crowed with buildings and houses. It is often surrounded by hills, forests, and mountains. The importance of surface scattering intereference between transmitters and receivers on the rough surfaces has been interested and investigated. Therefore, a prediction method is necessary to estimate the influence of rough surfaces on microwave radio propagation. Moreover, most of the mobile communications are performed based on the digital communication system rather than the analog one. In this case, we must pay more careful attention to the signal delay caused by the phase delay due to the multi-path propagation. In this paper we have analyzed numerically scattering of electromagnetic waves from building walls by using FVTD(Finite Volume Time Domain) method. We consider three different types of rough surfaces such as periodic, random, and composite structures. We calculate the bistatic normalized radar cross section (NRCS) for horizontal and vertical polarization, and we take account of the conventional optical reflection which corresponds to the n-th Bragg reflection for periodic structures. In addition, we investigated what conditions are needed in order to be able to ignore the higher order Bragg reflection for the periodic structures.

A real-time construction management of a tunnel using position tracking sensor (위치추적 센서를 이용한 터널의 실시간 시공관리)

  • Lee, Kang-Hyun;Kim, Dae-Won;Mun, Sung-Mo;Cho, Hun-Hee;Kang, Kyung-In;Lee, In-Mo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.13 no.2
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    • pp.133-148
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    • 2011
  • Construction sites are becoming larger and complex with the growth of national economy. Accordingly, it is important to identify real-time information about materials, equipments, and manpower during construction at sites. Even though research utilizing position tracking sensors has been conducted in architectural engineering fields, this area of research is almost nil in civil engineering fields. Therefore, a feasibility study to find a way to apply position tracking sensors to an in-situ tunnel construction site adopting conventional tunnelling method is performed in this study. A methodology is proposed that the progress management of the tunnelling work can be monitored by checking construction materials needed at job site and the safety management system can be assessed by checking distance between in-situ workers and construction equipments. The most representative materials were identified so that IT technology can be applied by attaching and monitoring sensors to the selected materials. Also, time of arrival (TOA) for a position determination technology along with a wireless network technology was chosen and build wireless network system. The adopted methodology was applied to an in-situ tunnelling site, and verified the usefulness of the proposed system.