• Title/Summary/Keyword: bridge system

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Magnetic Exchange Interactions in a 2D Grid-like Copper(II) Polymer with Bridging End-on Cyanato and Pyrazine Ligands: A DFT Study

  • Kang, Dae-Bok
    • Bulletin of the Korean Chemical Society
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    • v.31 no.6
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    • pp.1704-1710
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    • 2010
  • The structure of a 2D grid-like copper(II) complex [Cu$(NCO)_2$(pyz)](pyz=pyrazine) (1) consists of 1D chains of Cu-pyz units connected by double end-on (EO) cyanato bridges. Each Cu(II) ion has a distorted octahedral coordination, completed by the four EO cyanato and two pyrazine ligands. Magnetic interactions through EO cyanato and pyrazine bridges in 1 are discussed on the basis of DFT broken-symmetry calculations at the B3LYP level. For model dicopper(II) complexes I (bridged by cyanato) and II (bridged by pyrazine), electronic structure calculations reproduce very well the experimental couplings for the S = 1/2 ferromagnetic and antiferromagnetic exchange-coupled 2D system: the calculated exchange parameters J are +1.25 $cm^{-1}$ and -3.07 $cm^{-1}$ for I and II, respectively. The $\sigma$ orbital interactions between the Cu $x^2-y^2$ magnetic orbitals and the nitrogen lone-pair orbitals of pyrazine are analyzed from the viewpoint of through-bond interaction. The energy splitting of 0.106 eV between two SOMOs indicates that the superexchange interaction should be antiferromagnetic in II. On the other hand, there are no bridging orbitals that efficiently connect the two copper(II) magnetic orbitals in I because the HOMOs of the basal-apical NCO bridge do not play a role in the formation of overlap interaction pathway. The energy separation in the pair of SOMOs of I is calculated to be very small (0.054 eV). This result is consistent with the occurrence of weakly ferromagnetic properties in I.

An Experimental Study for Bond Stress between DFRCC and Carbon FRP Plank Used as a Permanent Formwork (영구거푸집으로 활용한 탄소섬유 FRP 판과 DFRCC 사이의 부착응력에 관한 실험적 연구)

  • Park, Chan-Young;Yoo, Seung-Woon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.6
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    • pp.1687-1694
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    • 2014
  • Recently FRP of carbon fibers is utilized as a repairing and reinforcing material for concrete structures. In this study, the bond performance between CFRP planks and ductile fiber reinforced cementitious composites was evaluated in order to develop a new system of concrete bridge deck to take advantage of the FRP planks of carbon fiber using as a permanent formwork. In order to strengthen the bonding between the FRP and cast-in-place concrete, an epoxy resin circulated in the market generally was fitted with a silica sand. The bond stress of ordinary concrete appeared in 2.11~5.43MPa and the bond stress of ductile fiber reinforced cementitious composites DC1 (RF4000) and DC2 (PP) respectively were 3.91~5.60MPa, 2.92~5.21MPa and the average bond stress of DC3 (RF4000+RSC15) and DC4 (PP+RSC15) were 4.80~5.58MPa, 5.57~5.89MPa.

Comparison of Abdominal Muscle Thickness Using Ultrasound Imaging During Bridging Exercises With a Sling and Ball in Healthy Young Adults

  • Moon, Young;Choi, Jong-duk
    • Physical Therapy Korea
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    • v.27 no.1
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    • pp.87-92
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    • 2020
  • Background: Bridging exercises are used to enhance the functional stability of the lumbopelvic region in clinical settings. Although most of the studies on bridging exercises have compared the complete activation of the trunk muscles, some recent studies have examined the functional stability of the trunk and the lumbopelvic region and assessed the appropriate recruitment of the local and global muscles during different task levels. Objects: The purpose of this study was to investigate the changes in muscle thickness in the transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) muscles during a common bridging exercise on an unstable surface and to determine whether these changes differ based on the surface used. Methods: Twenty-five healthy young adults (8 males, 17 females) were recruited. The subjects were randomly assigned to either the exercise progression with a sling bridge group or the ball bridging exercise progression group, each with three stages of increasing difficulty. Each position was measured three times with an ultrasonic diagnostic imaging system, and the mean values were recorded for analysis. Results: No significant differences were observed between the TrA, IO, or EO muscle thickness ratios between the sling and ball exercise groups (p > 0.05). There were also no significant differences in the EO muscle thickness ratios between the tasks irrespective of whether the sling or ball was used. However, the TrA and IO thickness ratios in both groups were significantly greater during stages 2 and 3 compared to stage 1. Conclusion: The results suggest that the use of slings and balls during bridging exercises is effective in activating the deep abdominal muscles.

A Study on the Design and Effect of Feedback for Virtual Reality Exercise Posture Training (가상현실 운동 자세 트레이닝을 위한 피드백 설계 및 효과 연구)

  • Park, Woohee;Kim, Jieun;Lee, Jieun
    • Journal of the Korea Computer Graphics Society
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    • v.26 no.3
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    • pp.79-86
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    • 2020
  • It is important to exercise in the correct posture in order to increase the exercise effect of the core exercise. This paper introduces a system that can train an exercise posture by providing feedback so that a user who performs core exercise in a virtual reality environment can take an accurate posture. It targeted three core movement postures, such as squat, lunge, and bridge, and provides visual feedback and haptic feedback to the user to take an accurate posture. The reference posture is generated by adjusting the expert's posture to the user's body length, and the accuracy of the exercise posture is calculated by comparing the user's posture with the reference posture. The effectiveness of the feedback was verified through user experiments, and the training effects according to the design of the feedback were compared.

Estimation of Initial Tensile Force Acting on Tendon using the Deformation of a Multi-tendon Anchor Head (멀티 텐던 앵커헤드의 변형을 이용한 텐던의 초기 긴장력 추정)

  • Park, Jang Ho;Cho, Jeong-Rae;Park, Jaegyun
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.27 no.6
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    • pp.581-588
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    • 2014
  • The PSC bridges have recently been widely used in Korea. The PSC bridge is a structure whose performance is improved through the use of tendons and steel bars in deflection and cracking characteristics of the concrete. Therefore, measurement or estimation of the load acting on tendon is important in order to maintain the PSC bridges efficiently and safely. This paper deals with a numerical study on the deformation of a multi-tendon anchor head in order to verify the relationship between the load acting on tendon and the deformation of anchor head. All kinematics, material properties and contact nonlinearity are included for the precise analysis and numerical studies are performed by Abaqus. From the numerical results, it is verified that the hoop strain is most useful in the estimation of the load acting on tendon and strains are affected by various parameters such as friction coefficient, boundary conditions, and arrangement.

Systemization Setting of Various Improvement Plans in Railway Bridges (철도교량에서 다양한 개량계획의 체계화 설정)

  • Baek, Jae-Wook;Park, Tae-Hyo
    • Journal of the Korean Society for Railway
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    • v.14 no.4
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    • pp.354-363
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    • 2011
  • Existing railway bridges have been going through various improvements since the past, with new improvement plans being formed based on social and technological demands. However, there is the need, above all, for an efficient execution plan due to the great number of sites and excessive amount of required expenses contrary to limited assets. The system itself must be held in question in order to systemize various improvement plans, to define and describe factors while utilizing evaluation methods for significance and correlation to achieve generalization. This paper is focused on determining the priority of various improvement plans through the optimization selection process of mutually evaluating alternative plans under various evaluation standards, thus corresponding to the decision-making purpose. The AHP analysis technique was applied for systemization setting and preference evaluation, while the HPT procedure was applied to develop and select appropriate improvement plan factors.

Nonlinear Finite Element Analysis of Circular Hollow Reinforced Concrete Columns Based on Design Variables (설계변수에 따른 중공원형 철근콘크리트 교각의 비선형 유한요소해석)

  • Cheon, Ju-Hyun;Lee, Seung-Jin;Lee, Byung-Ju;Lee, Jae-Hoon;Shin, Hyun-Mock
    • Journal of the Earthquake Engineering Society of Korea
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    • v.15 no.2
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    • pp.35-42
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    • 2011
  • The seismic design of solid reinforced concrete bridge columns has been committed to, based on accumulated research and design specifications. The rational confinement model and seismic performance evaluation, however, are insufficient because of the lack of domestic and foreign design specifications about the experimental and analytical difficulties in the case of circular hollow reinforced concrete columns. In this paper, the seismic behavior of circular hollow reinforced concrete columns and its dependence on design variables are understood and explained. These research results can be used to derive the rational and economical design specifications for circular hollow sectional columns based on the result from the nonlinear analysis program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology).

Rainfall-Runoff Characteristics in a Jeju Stream considering Antecedent Precipitation (선행강우를 고려한 제주하천 유출특성 분석)

  • Yang, Sung-Kee;Kim, Dong-Su;Jung, Woo-Yul
    • Journal of Environmental Science International
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    • v.23 no.4
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    • pp.553-560
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    • 2014
  • The rainfall-runoff characteristics in Jeju Island significantly differ from those in inland, due to highly permeable geologic features driven by volcanic island. Streams are usually sustained in the dry conditions and thereby the rainfall-runoff characteristics changes in terms of initiating stream discharge and its types, depending highly on the antecedent precipitation. Among various the rainfall-runoff characteristics, lag time mainly used for flood warning system in river and direct runoff ratio for determining water budget to estimate groundwater recharge quantity are practically crucial. They are expected to vary accordingly with the given antecedent precipitation. This study assessed the lag time in the measured hydrograph and direct runoff ratio, which are especially in the upstream watershed having the outlet as $2^{nd}$ Dongsan bridge of Han stream, Jeju, based upon several typhoon events such as Khanun, Bolaven, Tembin, Sanba as well as a specific heavy rainfall event in August 23, 2012. As results, considering that the lag time changed a bit over the rainfall events, the averaged lag time without antecedent precipitation was around 1.5 hour, but it became increased with antecedent precipitation. Though the direct run-off ratio showed similar percentages (i.e., 23%)without antecedent precipitation, it was substantially increased up to around 45% when antecedent precipitation existed. In addition, the direct run-off ration without antecedent precipitation was also very high (43.8%), especially when there was extremely heavy rainfall event in the more than five hundreds return period such as typhoon Sanba.

Application of Artificial Neural Network Model for Environmental Load Estimation of Pre-Stressed Concrete Beam Bridge (PSC Beam교 환경부하량 추정을 위한 인공신경망 모델 적용 연구)

  • Kim, Eu Wang;Yun, Won Gun;Kim, Kyong Ju
    • Korean Journal of Construction Engineering and Management
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    • v.19 no.4
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    • pp.82-92
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    • 2018
  • Considering that earlier stage of construction project has a great influence on the possibility of lowering of environmental load, it is important to build and utilize system that can support effective decision making at the initial stage of the project. In this study, we constructed an environmental load estimation model that can be used at the early stage of the project using basic design factors. The model was constructed by using the artificial neural network to estimate environmental load by applying to planning stage (ANN-1), basic design stage (ANN-2). The result of test, shows that average of absolute measuring efficiency and standard deviation of ANN-1 and ANN-2 were 11.19% / 5.30% and 9.59% / 3.09% each. This result indicates that the model using the input variables extended with the project progress has high reliability and it is considered to be effective in decision support at the initial design stage of the project.

A study on the annual energy performance of apartment building with the equivalent U-value of envelope considering the effect of thermal bridges (공동주택 외피의 열교영향을 고려한 상당열관류율 및 연간 에너지소비성능 평가 연구)

  • Kim, Dong Su;Yoon, Jong Ho;Shin, U Cheul;Kwak, Hee Yul
    • KIEAE Journal
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    • v.12 no.3
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    • pp.41-46
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    • 2012
  • The building envelope is important specially for saving energy consumption of residential buildings. but Apartment houses in Korea commonly have inside insulation system which have constantly arisen thermal bridges, the risk of heat loss, as a necessity. This study aims to evaluate integrated insulation performance according to the different shapes of external walls, adjacent to windows. The thermal performance analysis was carried out by Equivalent U-value and using the three-dimensional heat transfer computer simulation (TRISCO-RADCON), under nine different cases of comparing among three each of different bases(current standard model, 30percent energy saving model and 60percent energy saving model). The heating and the cooling load were also compared between two cases (standard U-value and Equivalent U-value) of three each of different bases, using the Building energy simulation which is based on DOE-2.1 analysis. As results, it turns out that if the Equivalent U-value is considered on the envelope analysis, the heat flow loss will be increasing more than the standard U-value, and if heat insulation property of the residential building reinforced rather than current, the rate of influences on the thermal bridges would be extremely expanded. In addition, it is shown that annual heating loads of the apartment house with applied Equivalent U-value substantially increased by more than 15 percent compared to those with the existing U-value, but annual cooling loads were negligibly affected.