• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.785-794
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• 2004

This paper describes a new refined truss modeling technique derived based on the well-known relationship of V=dM/dx=zdT/dx+Tdz/dx in a reinforced concrete beam subjected to combined shear and moment loads. The core of the model is that a new perspective on the shear behavior can be gained by considering the variation of the internal arm length along the span, so that the shear resistance mechanism can be expressed by the sum of two base components; arch action and beam action. The sharing ratio of these two actions is determined by accounting for the compatibility of deformation associated to the two actions. Modified Compression Field Theory and the tension-stiffening effect formula in CEB/FIP MC-90 are employed in calculating the deformations. Then the base equation of V=dM/dx has been numerically duplicated to form a new refined truss model.

• Composites Research
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• v.16 no.4
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• pp.74-79
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• 2003

Comparison of interfacial properties and microfailure mechanisms of oxygen-plasma treated poly(p-phenylene-2,6-benzobisoxazole(PBO. Zylon) and poly(p-phenylene terephthalamide)(PPTA, Kevlar) fibers/ epoxy composites were investigated using micromechanical technique and nondestructive acoustic emission(AE). Interfacial shear strength(IFSS) and work of adhesion, Wa of PBO or Kevlar fibers/epoxy composites increased by oxygen-plasma treatment. Plasma-treated Kevlar fiber shooed the maximum critical surface tension and polar term, whereas the untreated PBO fiber showed the minimum value. Microfibril fracture pattern of plasma-treated Kevlar fiber appeared obviously. Based on the propagation of microfibril failure toward core region. the number of AE events for plasma-treated PBO and Kevlar fibers increased significantly. The results oi nondestructive AE were consistent well with microfailure modes by optical observation in microdroplet and two-fiber composites tests.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.61-69
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• 2001

EFP(Fitness For Purpose) type defect assessment methodologies based on ECA(Engineering Critical Analysis) have been established and are in use for the structural integrity evaluation of gas pipelines. ECA usually includes the fracture mechanics analysis, and it is assumed that the J-integral uniquely characterizes the crack-tip stress-strain field. However, it has been proven that the J-integral alone can not be sufficient to characterize the crack-tip field under low levels of constraint with a single parameter. Since pipeline structures are made of ductile material, locally loaded in tension, cracks may experience low level of constraint, and therefore, J-dominance will be lost. For this reason, the level of constraint must be quantified to establish a precise assessment procedure for pipeline defects. The objective of this paper is to investigate the fracture behavior of a crack in gas pipeline(KS D 3507) by quantifying the level of constraint. For this purpose, tensile tests and CTOD tests were performed at room temperature(24$\^{C}$) and low temperature(-40$\^{C}$) to obtain the material properties. J-Q analyses were performed for SENB and SENT specimens based on 2-D finite element analyses, in order to investigate the in-plane constraint effects on pipeline defects. For precise assessment of cracks, especially shallow cracks, in KS D 3507 pipeline, constraint effect must be considered.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.209-216
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• 2000

The lateral behavior of the moving web is critical to the quality of the web products. The alignment of the rollers carrying the web is found to be one of important factors to the lateral behavior of the moving web. But, the study on the effect of the tilting roller in the direction of the normal to the moving web on the lateral behavior has not been reported in the literature yet. For example, the contact roller often contacts the winding roll in a tilted fashion and causes the lateral motion of the winding web, which induces the offset on the wound roll. The lateral dynamics of the moving web induced by a tilted roller in normal direction of a web is investigated in this paper. The two-dimensional dynamic model developed by Shelton is extended to investigate the effect of a titled roller in a normal direction of the moving web on the lateral motion of the moving web. New boundary conditions are developed to solve the extended model. Computer simulation study proved that the model developed can be used to predict the lateral motion of the moving web ？ to a tilted roller in normal direction of the moving web. The lateral deflection is increased exponentially a the tilting angle is increased. As the length of web span is increased, the amount of lateral deflection was increased almost linearly for the same tilting angle. The lateral dynamics turned out to be almost independent to the operating tension. The model developed can be used to solve the offset problem of the staggered winding and also to design a new web guiding mechanism.

• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.844-851
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• 2010

Controlling the dissolved oxygen (DO) in the fed-batch culture of the medicinal mushroom Ganoderma lucidum led to a 2-fold increase of the maximum biomass productivity compared with uncontrolled DO conditions. By contrast, extracellular polysaccharide (EPS) production was two times higher under oxygen limitation (uncontrolled DO) than under increased oxygen availability (controlled DO). Morphologically, dispersed mycelium was predominant under controlled DO conditions, with highly branched hyphae, consistent with the enhanced culture growth noted under these conditions, whereas in the uncontrolled DO process mycelial clumps were the most common morphology throughout the culture. However, in both cultures, clamp connections were found. This is an exciting new finding, which widens the applicability of this basidiomycete in submerged fermentation. In rheological terms, broths demonstrated shear-thinning behavior with a yield stress under both DO conditions. The flow curves were best described by the Herschel-Bulkley model: flow index down to 0.6 and consistency coefficient up to 0.2 and 0.6 Pa $s^n$ in uncontrolled and controlled cultures DO, respectively. The pseudoplastic behavior was entirely due to the fungal biomass, and not to the presence of EPS (rheological analysis of the filtered broth showed Newtonian behavior). It is clear from this study that dissolved oxygen tension is a critical process parameter that distinctly influences G. lucidum morphology and rheology, affecting the overall performance of the process. This study contributes to an improved understanding of the process physiology of submerged fermentation of G. lucidum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.42-42
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• 2008

Considerable attention has been focused on the applications of flexible liquid crystal (LC)-based displays because of their many potential advantages, such as portability, durability, light weight, thin packaging, flexibility, and low power consumption. To develop flexible LCDs that are capable of delivering high-quality moving images, like conventional glass-substrate LCDs, the LC device structure must have a stable alignment layer of LC molecules, concurrently support uniform cell gaps, and tightly bind two flexible substrates under external tension. However, stable LC molecular alignment has not been achieved because of the layerless LC alignment, and consequently high-quality images cannot be guaranteed. To solve these critical problems, we have proposed a PDMS pixel-wall based bonding method via the IB irradiation was developed for fasten the two substrates together strongly and maintain uniform cell gaps. The effect of the IB irradiation on PDMS with PI surface was also evaluated by side structure configuration and a result of x-ray photoelectron spectroscopic analysis of PDMS interlayer as a function of binder with substrates. large number of PDMS pixel-walls are tightly fastened to the surface of each flexible substrate and could maintain a constant cell gap between the LC molecules without using any other epoxy or polymer. To enhance the electro-optical performance of the LC device, we applied an alignment method that creates pretilt angle on the PI surface via ion beam irradiation. Using this approach, our flexible LCDs have a contrast ratio of 132:1 and a response time of about 15 ms, resulting in highly reliable electro-optical performance in the bent state, comparable to that of glass-substrate LCDs.

• Journal of the Korean Applied Science and Technology
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• v.13 no.3
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• pp.61-71
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• 1996

In acid-catalyzed acetal cyclization of long aliphatic aldehydes($R=n-C_7H_{15}$ ; $n-C_9H_{19}$ ; $n-C_{11}H_{23}$) with 1,1,1-tris(hydroxymethyl)propane, 2-alkyl-5-hydroxymethyl-5-ethyl-1,3-dioxanes were obtained. The final products, sodium 2-alkyl-5-(sulfonatedpropylethermethyl)-5-ethyl-1,3-propanesultion in the presence of sodium hydride. These compounds were a new group of destructible surfactants which were readily hydrolyzed and oxidized in natural water reservoirs. Physical properties of these new compounds involved some surface properties such as Krafft point(Kp), critical micelle concentration(cmc), surface tension of aqueous solutions near cmc(${\gamma}_{min}$), foaming power, emulsion power and hydrolysis properties were determined. The destructible surfactants containing 1,3-dioxane ring were synthesized to about $85{\pm}5.5%$ yield. The cmc values of the compounds by ring method were assumed to $0.5{\sim}5.0{\times}10^{-3}mol/L$ range and surface tensions at cmc were $29.5{\sim}33.0dyne/cm$ respectively at $25^{\circ}C$. The foaming power and foam stability were $170{\sim}230mm$ and $52{\sim}135mm$ respectively at $1{\times}10^{-2}mol/L$, foam was occurred rarely below $1{\times}10^{-3}mol/L$. The emulsion property of liquid paraffin was better than that of soybean oil. For hydrolysis property with ph and time, these compounds were decomposed within about 200minutes at $ph1{\sim}2$. Hopefully these compounds are expected to be a good O/W emulsifier that have decomposability in acid and may be used in the process which do not need foaming.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.60.1-60.6
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• 2019

Background: The lingual nerve plays an important role in multiple functions, including gustatory sensation and contact sensitivity and thermosensitivity. Misdiagnosed conservative treatments for serious lingual nerve (LN) injuries can induce the patient to serious mental disability. After continuous observation and critical diagnosis of the injury, in cases involving significant disruption of lingual nerve function, microneurosurgical reconstruction of the nerve is recommended. Direct anastomosis of the torn nerve ends without tension is the recommended approach. However, in cases that present significant gaps between the injured nerve ends, nerve grafts or conduits (tubes of various materials) are employed. Recently, various reconstruction materials for peripheral nerves were commercially offered especially in the USA, but the best method and material is still unclear in the world. There currently exists no conventional protocol for managing LN neurosensory deficiency in regard to optimal methods and the timing for surgical repair. In Japan, the allograft collagen nerve for peripheral nerves reconstruction was permitted in 2017, and we tried to use this allograft nerve and got a recommendable result. Case presentation: This report is a long-term abandoned torn LN reconstructed with allograft nerve induced by the lower third molar extraction. Conclusions: In early sick period, with the exact diagnosis, the LN disturbance should be managed. In a serious condition, the reconstruction with allograft nerve is one of the recommendable methods.

• Progress in Superconductivity and Cryogenics
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• v.17 no.3
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• pp.13-17
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• 2015

In superconducting coil applications particularly in wet wound coils, coated conductor (CC) tapes are subjected to different type of stresses. These include hoop stress acting along the length of the CC tape and the Lorentz force acting perpendicular to the CC tape's surface. Since the latter is commonly associated with delamination problem of multi-layered CC tapes, more understanding and attention on the delamination phenomena induced in the case of coil applications are needed. Difference on the coefficient of thermal expansion (CTE) of each constituent layer of the CC tape, the bobbin, and the impregnating materials is the main causes of delamination in CC tapes when subjected to thermal cycling. The CC tape might also experience cyclic loading due to the energizing scheme (on - off) during operation. In the design of degradation-free superconducting coils, therefore, characterization of the delamination behaviors including mechanism and strength in REBCO CC tapes becomes critical. In this study, transverse tensile tests were conducted under different loading conditions using different size of upper anvils on the GdBCO CC tapes. The mechanical and electromechanical delamination strength behaviors of the CC tapes under transverse tensile loading were examined and a two-parameter Weibull distribution analysis was conducted in statistical aspects. As a result, the CC tape showed similar range of mechanical delamination strength regardless of cross-head speed adopted. On the other hand, cyclic loading might have affected the CC tape in both upper anvil sizes adopted.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.379-388
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• 2006

This paper presents a model for evaluating the contribution by arch action to shear resistance in shear-critical reinforced concrete beams. Based on the relationship between shear and bending moment in beams subjected to combined shear and bending, the behavior of a beam is explicitly divided into two base components of the flexural action and the tied arch action. The compatibility condition of the shear deformation that deviates from Bernoulli bending plane is formulated utilizing the smeared truss idealization with an inclined compression chord. The Modified Compression Filed Theory is employed to calculate the shear deformation of the web, and the relative axial displacements of the compression and the tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. Then the validity of the model is examined by applying the model to some selected test beams in literatures. The results may confirm the rationale of the proposed behavioral model.