• Journal of Advanced Research in Ocean Engineering
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• v.1 no.2
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• pp.106-114
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• 2015

In the fabrication of offshore oil and gas facilities, the significance of dimension control is growing continuously. But, it is difficult to determine the deformation of the structure during fabrication by simple lab tests due to the large size and the complicated shape. Strain-boundary method (a kind of shrinkage method) based on the shell element was proposed to predict the welding distortion of a structure effectively. Modeling of weld geometry in shell element is still a difficult task. In this paper, a concept of imaginary temperature pair is introduced to handle the effect of geometric factors such as groove shape, plate thickness and pass number, etc. Single pass imaginary temperature pair formula is derived from the relation between the groove area and the FE mesh size. By considering the contribution of each weld layer to the whole weldment, multi-pass imaginary temperature is also derived. Since the temperature difference represents the distortion increment, cumulative distortion curve can be drawn by integrating the temperature difference. This curve will be a useful solution when engineers meet some problems occurred in the shipyard. A typical example is shown about utilization of this curve. Several verifications are conducted to examine the validity of the proposed methodology. The applicability of the model is also demonstrated by applying it to the fabrication process of the heavy ship block. It is expected that the imaginary temperature model can effectively solve the modeling problem in shell element. It is also expected that the cumulative distortion curve derived from the imaginary temperature can offer useful qualitative information about angular distortion without FE analysis.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.174-180
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• 2000

A reliable analytic model that determines the cross sectional shape of a workpiece(material) in round-oval(or oval-round) pass sequence has been developed. the cross sectional shape of an outgoing workpiece is predicted by using the linear interpolation of the radius of curvature of an incoming workpiece and that of roll groove to the roll axis direction. The requirements we placed on the choice of the weighting function were to ensure boundary conditions specified. The validity of the analytic model has been examined by hot rod rolling experiment with the roll gap and specimen size changed. The cross sectional shape and area of a workpiece predicted by the proposed analytic model were good agreement with those obtained experimentally. It was found that the analytic model has not only simplicity and accuracy for practical usage but also save a large amount of computational time compared with finite element method.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.132-137
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• 2001

Miniaturized specimen technology is useful to characterize the mechanical behavior using a minimum volume of material, because it is almost impossible to sample the conventional specimen for the fracture toughness test without damage to equipment. Test material was 1Cr-1Mo-0.25V steel which was widely used for turbine rotor material. Two kinds of miniaturized impact specimens were prepared, i.e., miniaturized specimen with side groove and without side groove. The correlation between ductile brittle transition temperature(DBTT) of full size impact specimen and that of miniaturized impact specimen was made. The characteristics of miniaturized impact specimens technique as well as fracture stress were discussed. Finally, we concluded that the characteristics of fracture stress change on aging time were similar to that of DBTT.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.880-882
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• 2002

We have proposed a novel optical design technique of light-guide plates(LGPs) which can able to improve the optical efficiency of transflective LCDs. The basic concepts of our design technique are that we make the groove-pattern of LGP pixels resemble the pixel-array-pattern of transflective LCDs in shape and size and make the surface of the groove scatter (front scattering). In simulated and measured results, we ensure that our design of LGP in backlight unit for transflective LCDs can improve the optical efficiency of LCDs.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.8
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• pp.691-697
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• 2004

Experimental study is carried out to investigate the heat transport capability and thermal resistance of sinusoidal axially grooved heat pipe, comparing its performance to trapezoidal axially grooved heat pipe. As a result from this work, the heat transport capability of sinusoidal grooved heat pipe is lower than that of trapezoidal grooved heat pipe for the same size of outer diameter. As the ratio of depth to width of sinusoidal groove heat pipe is higher, the heat transport capability of heat pipe becomes higher. It is found that Aluminum-ammonia heat pipes with sinusoidal and trapezoidal grooves have good thermal resistance, below 0.1$^{\circ}C$/W at evaporator section and below 0.05$^{\circ}C$/W at condenser section.

• YAKHAK HOEJI
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• v.54 no.1
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• pp.67-74
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• 2010

Some of the benzopyrene (BP)-DNA adduct are known to build intercalated motif between flanking base pairs in damaged DNA depending on the structural condition. The size of benzopyrene itself is definitely not comparable with any of the DNA bases and thus the question whether the lesion of some base pair by insertion of benzopyrene can happen with or without a dramatic distortion of the helical structure is a highly interesting theme. In this work we used a molecular dynamics simulation based on the theory of molecular mechanics. The specific consequences about the structural properties of the intercalated structures and benzopyrene motif in minor groove of the double helix are deduced after 5 ns simulation time.

• Advances in concrete construction
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• v.7 no.3
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• pp.191-201
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• 2019

Bamboo concrete bond behaviour is investigated through pullout test in this work. The bamboo strip to be used as reinforcement inside concrete is first treated with chemical adhesive to make the bamboo surface impermeable. Various surface coatings are explored to understand their water repellant properties. The chemical action at the bamboo concrete interface is studied through different chemical coatings, sand blasting, and steel wire wrapping treatment. Whereas mechanical action at the bamboo concrete interface is studied by developing mechanical interlock. The result of pullout tests revealed a unique combination of surface treatment and grooved bamboo profile. This combination of surface treatment and a grooved bamboo profile together enhances the strength of bond. Performance of a newly developed grooved bamboo strip is verified against equivalent plain rectangular bamboo strip. The test results show that the proposed grooved bamboo reinforcement, when treated, shows highest bond strength compared to treated plain, untreated plain and untreated grooved bamboo reinforcement. Also, it is observed that bond strength is majorly influenced by the type of surface treatment, size and spacing of groove. The changes in bamboo-concrete bond behavior are observed during the experimentation.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.523-527
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• 2011

Polycarbonate (PC) polymer is an engineering plastic which has large tensile strength and impact resistance and is wildly used as functional parts like micro mold. Direct machining of PC materials produces lots of burrs and rough surface due to large ductility and weak heat resistance and hence it is very difficult to machine PC materials using cutting tool to make micro-parts. In this study, elliptical vibration cutting (EVC) or 2-dimensional vibration cutting was performed to minimize the size of micro V-grooves on PC material. From the experimental results, it was observed that as the cutting depth and pattern size become smaller, the better machining quality was obtained, which is attributed to the positive effect of EVC that is dependent on the ratio of vibration amplitude to cutting depth. As the height of V-groove becomes less than $1.8{\mu}m$, however, the machining quality becomes lower as the pattern size decreases.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.729-736
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• 2015

In this study, the effects of specimen size and side-groove on the results of the J-R test for leak-before-break (LBB) evaluation were investigated. A series of J-R tests were conducted at both RT and $316^{\circ}C$, using three different sizes of compact tension (CT) specimens machined from SA508 Gr.1a piping material: 12.7 mm-thick 1T-CT, 25.4 mm-thick 1T-CT, and 25.4 mm-thick 2T-CT with and without side-groove. The results showed that side-grooving reduced the J-R curve for all specimens and the effect of side-grooving was more significant at $316^{\circ}C$ than at RT. As the thickness of the specimens decreased and the width of the specimens increased, the J-R curve slightly decreased at RT but it increased at $316^{\circ}C$. However, the variation in the J-R curve of SA508 Gr.1a with the thickness and width of CT specimen was insignificant.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.339-345
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• 2012

Electrospun meshed poly-caprolactone PCL was patterned by femtosecond laser with linear grooves. As parametric variables, focus spot size, pulse energy, and scanning speed were varied to determine the affects on groove size and the characteristics of the electrospun fiber at the edges of these grooves. The femtosecond laser was seen to be an effective means for flexibly structuring the surface of ES PCL scaffolds and the width of the ablated grooves was well controlled by laser energy and focus spot size. The ablation threshold was measured to be $14.9J/cm^2$ which is a little higher than other polymers. These affects were attributed to optical multiple reflections inside nano-fibers. By the laser-induced plasma at higher pulse energies, some melting of fibers was observed.