• Computers and Concrete
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• 제22권2호
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• pp.133-142
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• 2018

The deterioration of existing bridges has become a major problem around the world. In the paper, a new model and an associated stress checking method are proposed for concrete box girders strengthened by external prestressing. The new model called the spatial grid model can analyze all the spatial behaviors clearly by transforming the box girder into discrete orthogonal grids which are equivalent to plate elements. Then the three-layer stresses are employed as the stress checking indices to evaluate the stress state of the plate elements. The initial stress check before strengthening reveals the cracked and potential cracking areas for existing bridges, making the strengthening design more targeted and scientific; the subsequent stress check after strengthening evaluates the strengthening effect and ensures safety. A deficient bridge is selected as the practical example, verifying the accuracy and applicability of the proposed model and stress checking method. The results show that principal stresses in the middle layer of plate elements reflect the main effects of external prestressing and thus are the key stress checking indices for strengthening. Moreover, principal stresses check should be conducted in all parts of the strengthened structure not only in the webs. As for the local effects of external prestressing especially in the areas near anchorage and deviator, normal stresses check in the outer and inner layers dominates and local strengthening measures should be taken if necessary.

• 한국재난정보학회 논문집
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• 제11권1호
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• pp.1-8
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• 2015

본 연구에서는 토압 등의 외압이 원주 용접된 매설 강관의 잔류응력에 미치는 영향을 유한요소 해석을 통하여 명확히 하였다. 먼저 3차원 열탄소성 해석을 통하여 원주 용접된 강관의 잔류응력을 구하였으며, 이를 초기조건으로 설정하여 3차원 탄소성 해석을 수행함으로써 외압이 작용하는 경우 잔류응력 거동을 조사하였다. 해석결과 외압에 의해 원주 용접부에 발생하는 원주방향 압축응력 때문에 원주방향 잔류응력이 압축 측으로 상당히 많이 이동함을 알 수 있었고, 축방향 잔류응력은 작용하는 외압에 의해 거의 영향을 받지 않음을 알 수 있었다.

• 한국자기공명학회논문지
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• 제21권3호
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• pp.102-108
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• 2017

Escherichia coli responds to ever-changing external and internal stresses by rapidly adjusting its physiology for better survival. This adjustment occurs at all levels including metabolites as well as mRNAs and proteins. Although there has been many reports describing E. coli's adaptation to various stresses regarding transcriptomics or proteomics, only a few investigations have been reported regarding this adaptation viewed from metabolites' perspective. We applied four different types of stresses at four different doses as imposed by NaCl, sorbitol, ethanol, and pH to investigate the similarities or differences among the stresses, and which stress causes the largest perturbation of the metabolite composition. We profiled the metabolites under such external stresses by using two-dimensional NMR spectroscopy and identified 39 metabolites including amino acids, sugars, organic acids, and nucleic acids. According to our statistical analysis, the osmotic stress caused by sorbitol differentiated itself from others, while NaCl showed the largest dose dependent metabolic perturbations. We hope this work will form a foundation on which an approach to a successful protein production is systematically provided by a favorable metabolic environment by imposing proper external stresses.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.407-414
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• 2000

This paper presents measured deformation of geomembrane installed on slopes of a landfill. The layout of geosynthetics installed on landfill slopes as required by regulations is composed of, in typical, geocomposite, geomembrane, geosynthetic clay liner in turn from the slope. An effort was made to better understand the sources of external forces acting on geosynthetics and their interactions. The results of a field observation indicated that tensile stresses induced on geomebrane were far less in magnitude than predicted by the design method employing mass equilibrium of waste. This was mainly because external forces acting on slopes were not transferred from geocomposite to underlying geomembrane. A simple, but rather rational method for assessing the stability of geosynthetics against tensile stresses was proposed. This method is based on a hypothesis that external forces acting on geosynthetics are the results of downdrag of waste during waste compaction.

• 한국생산제조학회지
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• 제24권2호
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• pp.231-237
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• 2015

The pin-gear drive is a special form of fixed-axle gear mechanism. A large wheel with cylindrical pin teeth is called a pinwheel. As pinwheels are rounded, they have a simple structure, easy processing, low cost, and easy overhaul compared with general gears. They are also suitable for low-speed, heavy-duty mechanical transmission and for occasions with more dust, poor lubrication, etc. This paper introduces a novel slewing ring bearing with an external pinwheel gear set (e-PGS). First, we consider the exact cam pinion profile of the e-PGS with the introduction of a profile shift. Then, the contact stresses are investigated to determine the characteristics of the surface fatigue by varying the shape design parameters. The results show that the contact stresses of the e-PGS can be lowered significantly by increasing the profile shift coefficient.

• 한국초전도ㆍ저온공학회논문지
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• 제2권2호
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• pp.20-25
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• 2000

A CICC type superconducting bus-line electrically connecting a superconducting magnet to a power supply is cooled down to low temperature under the external magnetic field during operation. The thermal contraction during the cooling may be constrained by the supports which are installed to protect the bus-line from Lorenz magnetic forces. This constrained contraction causes thermal stresses in the bus-line to release thermal contraction. The minimum stress conditions in the bus-line may be optimized by controlling the supporting arrangement considering the thermal contraction and the external field. The analytical method to find optimal supports arrangement was suggested by using the beam theory, and numerical calculation using commercial code was performed to verify the suggested analytical optimization method.

• 한국철도학회논문집
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• 제9권2호
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• pp.151-159
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• 2006

It analyzed the mechanical behaviors of non-ballasted railway bridge (steel plate girder type) with ballast reinforced on the finite element analysis, field test and laboratory test far the static and dynamic responses. The major objective of this study is to investigate the effects and application of reinforcement for steel plate girder railway bridge by the external post-tensioning method. The reinforcement of non-ballast railway bridge had obviously stable dynamic behaviors due to the additional dead force which was ballast. But in case of static behaviors, static displacements and stresses had increased nearly the allowable values. Therefore we analyzed the mechanical behaviors of non-ballasted railway bridge with ballast reinforced and external post-tensioning reinforced on the finite element analysis and laboratory test for the static and dynamic behavior. As a result, the reinforcement of ballasted railway bridge the external post-tensioning method are obviously effective for the additional dead force which is ballast. The analytical and experimental study are carried out to investigate the post-tension force decrease bending behavior and deflection in composite bridge for serviceability. The servicing railway bridge with ballast reinforced has need of the reasonable reinforcement measures which could be reducing the effect of additional dead load that degradation phenomenon of structure by an unusual. stresses and a drop durability.

• Journal of Welding and Joining
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• 제15권5호
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• pp.115-123
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• 1997

The buckling strength, fatigue strength, stress corrosion cracking are considerably effected on one of initial imperfections, the residual stresses produced by a circumferential weld between axisymmetric cylinders. Therefore, we study the residual stresses, plastic strain and temperature distribution with using thermal elasto-plastic analysis which are generated by a circumferential weld between axisymmetric cylinders. It is investigated that welding residual stresses have an effect on the strength of cylinder for inner and outer shell under external pressure.

• Structural Engineering and Mechanics
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• 제77권5호
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• pp.571-586
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• 2021

The present paper studies the influence of the inhomogeneous initial stresses in the bi-layered hollow cylinder and it is assumed that these stresses are caused by the hydrostatic pressures acting on the interior and outer free surfaces of the cylinder. The study is made by utilizing the version of the three-dimensional linearized theory of elastic waves in bodies with initial stresses for which the initial stress-strain state in bodies is determined within the scope of the classical linear theory of elasticity. For the solution to the corresponding eigenvalue problem, the discrete-analytical method is employed. Numerical results are presented and analyzed for concrete selected pairs of materials. According to these results and their analyses, it is established that, unlike homogeneous initial stresses, the influence of the inhomogeneous initial stresses on the torsional wave dispersion has not only quantitative but also qualitative character. For instance, in particular, it is established that as a result of the initial stresses caused by the hydrostatic pressure acting in the interior free surface of the cylinder, the cut-off frequency appears for the fundamental dispersive mode and the values of this frequency increase with the intensity of this pressure.

• 생명과학회지
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• 제23권4호
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• pp.479-486
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• 2013

대장균에서 DNA 결합 단백질로 확인된 DNA-binding Protein from Staved cells (DSP)는 DNA를 보호하는 중요한 기능을 한다는 것을 보여주었다. 이 연구의 목표는 야생형 대장균과 dps 유전자 결손 대장균(${\Delta}dps$ E.coli)의 특성 비교를 통해 여러 종류의 스트레스에 대해 대장균에서 DPS의 기능적 역할을 설명하는 것이다. 다양한 스트레스 상태에서 자외선 흡광도계(UV-spectrophotometer)를 이용하여 야생형 대장균과 dps 유전자 결손 대장균의 세포성장을 측정하였으며, 각각의 대장균 세포 성장 속도를 비교함으로써 우리는 대장균에 존재하는 DPS 단백질의 기능적 역할을 확인하였다. 야생형 대장균에 비해 dps 유전자 결손 대장균은 영양분 결핍, 산성화, 열충격, 다양한 활성산소종 스트레스들에 민감한 현상을 나타내었으며, 이것은 DPS가 다양한 극단적인 스트레스에 중요한 기능을 한다는 것을 제안하였다. 결론적으로 대장균의 DPS는 다양한 환경적인 스트레스로부터 DNA와 강하게 결합하여 유지함으로써 세포를 보호하고 세포성장에 결정적인 기능을 한다는 것을 증명하였다.