• Journal of Soil and Groundwater Environment
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• v.17 no.6
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• pp.119-128
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• 2012

The applicability and accuracy of Revised Universal Soil Loss Equation (RUSLE) model on the estimation of soil loss at impacted area of shooting range was tested to further the understanding of soil erosion at shooting ranges by using RUSLE. At a shooting range located in northern Kyunggi, the amount of soil loss was estimated by RUSLE model and compared with that estimated by Global Positioning System-Total Station survey. As results, the annual soil loss at a study site (202 m long by 79 m wide) was estimated to be 2,915 ton/ha/year by RUSLE and 3,058 ton/ha/year by GPS-TS survey, respectively. The error between two different estimations was less than 5%, however, information on site conditions should be collected more to adjust model coefficients accurately. At the study shooting range, sediments generated by rainfall was transported from the top to near the bottom of the sloping face through sheet erosion as well as rill erosion, forming a gully along the direction of the storm water flow. Coarser fractions of the sediments were redeposited in the limited area along the channel. Distribution characteristics of explosive compounds in soil before and after summer monsoon rainfall in the study area were compared with the erosion patterns. Soil sampling and analyses results showed that the dispersion of explosive compounds in surface soil was consistent with the characteristics of soil erosion and redeposition pattern of sediment movements after rainfalls.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.430.1-430.1
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• 2016

We present the concept of reducible fugitive material that conformally surrounds core Cu nanowire (NW) to fabricate transparent conducting electrode (TCE). Reducing atmosphere can corrodes/erodes the underlying/surrounding layers and might cause undesirable reactions such impurity doing and contamination, so that hydrogen-/forming gas based annealing is impractical to make device. In this regards, we introduce novel reducible shell conformally surrounding indivial CuNW to provide a protection against the oxidation when exposed to both air and solvent. Uniform copper lactate shell formation is readily achievable by injecting lactic acid to the CuNW dispersion as the acid reacts with the surface oxide/hydroxide or pure copper. Cu lactate shell prevents the core CuNW from the oxidation during the storage and/or film formation, so that the core-shell CuNW maintains without signficant oxidation for long time. Upon simple thermal annealing under vacuum or in nitrogen atmosphere, the Cu lactate shell is easily decomposed to pure Cu, providing an effective way to produce pure CuNW network TCE with typically sheet resistance of $19.8{\Omega}/sq$ and optical transmittance of 85.5% at 550 nm. Our reducible copper lactate core-shell Cu nanowires have the great advantage in fabrication of device such as composite transparent electrodes or solar cells.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.718-725
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• 2002

A wall type friction damper is newly Proposed in this paper to improve the performance of R/C framed structures under earthquake loads. Although traditional dampers are usually placed as bracing members, the application ot bracing-type dampers into R/C structures is not as simple as those of steel structures due to the connection between R/C members and dampers and the stress concentration in connection region. Proposed damper is consisted of Teflon-sheet slider and R/C shear wall. The damper can also avoid stress concentration and reduce P-Δ effect. To evaluate the performance of proposed damper, nonlinear dynamic analyses are carried on 10 story and 3 bay R/C structures with numerical model for the damper. It is shown that the damper reduces the inter-story drifts and the time-historic responses; especially the damper prevents from forming plastic hinges on the lower columns.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.33-40
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• 1988

The new technique has been used to determine the soil-reinforcement interaction. The testing apparatus is essentially a triaxial cell fitted with the capability to house a hollow cylinderical sample. A hollow cylinderical sand specimen with a concentrical layer of reinfarcing material sandwitched in the middle is used in this investigation. The reinforcement is fastened at the base. The hollow specimen can be viewed as a "unit sheet" of a soil-reinforcement composite system of infinite horizontal extent. Axial load as well as inner and outer chamber pressures can be applied to perform a test. The specimen is first subjected to an isotropic stress state corresponding to the overburden pressure. Next, an extension test by reducing the axial load is carried out. The specimen is "loaded" to failure by either the breakage of reinforcing material (tensile failure) or slippage which takes place at the soil-reinforcement interface (i.e. the overcoming of the bonding capacity). Since the reinforcement is fastened at its lower end to the base, any tendency of relative movement between the reinforcement and the sand during an extension test can induce tensile force in the reinforcement thus forming a "reversed pull-out" test condition. Preliminary test results have demonstrated positively of the new approach to test the soil-reinforcement interaction. Reinforcing elements of different extensibility were used to study the deformbility of reinforced soil. Furthermore, both the breakage and the pull-out modes of failure were observed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.267-275
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• 2012

Austenite stainless steel 304 has properties of high resistance to corrosion and temperature changes. Therefore, this material is widely used in various of industries. However, when the material is subjected to heating and cooling cycles the forming accuracy, for example, the right angle associated with a sharp bend such as corner is lost. This phenomenon is caused by the reversion of the deformation-induced martensite into austenite when the temperature in increased. This result in misfit of a structure or an assembly, and an increase in residual stress. Hence, it is important to understand this process. In this study, to evaluate the mechanical behavior of the deformation-induced martensite and reversed austenite, a scanning acoustic spectroscope including the capability of obtaining both phase and amplitude of the ultrasonic wave (i.e., the complex V(z) curve method) was used. Then, the velocities of the SAW propagating within the specimens made in different conditions were measured. The experimental differences of the SAW velocities obtained in this experiment were ranging from 2,750 m/s to 2,850 m/s, and the theoretical difference was 3.6% under the assumption that the SAW velocity was 2,800 m/s. The error became smaller as the martensite content was increased. Therefore, the SAW velocity may be a probe to estimate the marternsite content.

• The Journal of the Korean Society for Microbiology
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• v.17 no.1
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• pp.7-14
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• 1982

A model of induction of neoplasia by viruses has develpoed from experimental studies in animals and in cultured cells and oncogenic transformation of cells is the result of integration of viral genetic information into the cellular DNA. The evidence for these associations was derived primarily from seroepidemiologic investigation. However, data indicating that the relation between HSV-2 and cervical cancer fits the model derived from experimental animal studies are not yet sufficient to draw conclusion with regard to the etiologic role the virus in the development of the neoplasms. In other hand, the K562 tumor cell is highly susceptible target for natural killer cell lysis by the lymphocytes of human and murine periperal blood. The characteristics of this effector cell type has been investigated. A study on natural killer cell mediated cytotoxicity(NKMC) against $^{51}Cr$-K562 as target cell was studed in HSV-2 infected ICR mouse. We have studied for susceptibility of HSV-2 against mouse embryo fibroblast(MEF) cells and NKMC from HSV-2 infected mouse. The results obtained that the mouse embryo fibroblast cells culture, the number and size of the cells were markedly increased and formed a monolayers relatively rapid, and become complete monolayer sheet around 72 hrs. Duration of cytopathic effect on MEF cells was rapid by serial passing of HSV-2. The morphology of the HSV-2 infected cells appear to be mainly round, ovium, spindle form and some of them was forming large giant cells. The NKMC was decrease in mouse with HSV-2 and comparison between effector/target cells ratio as 25:1 and 50:1 respectively, the NKMC was found to be more significantly decreased than normal control we have concluded that the natural killer cell activity of the viral infected mouse was shown as a suppressed during the HSV-2 infection, day 7th and 14th.

• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.313-322
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• 2004

Thick film photolithography is a new technology in that the lithography process such as exposure and development is applied to the conventional thick film process including screen-printing. In this research, low-temperature cofireable silver paste, which enabled the formation of thick film fine-line using photolithographic technology, was developed. The optimum composition for fine-line forming was studied by adjusting the amounts of silver powder, polymer and monomer, and the additional amount of photoinitiator, and then the effect of processing parameter such as exposing dose on the formation of fine-line was also tested. As the result, it was found that the ratio of polymer to monomer, silver powder loading, and the amount of photoinitiator were the main factors affecting the resolution of fine-line. The developed photosensitive silver paste was printed on low-temperature cofireable green sheet, then dried, exposed, developed in aqueous process, laminated, and fired. Results showed that the thick film fine-line under 20$\mu\textrm{m}$ width could be obtained after cofiring.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.11
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• pp.3474-3490
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• 1996

A metal matrix composites(MMCs) for A16061 reinforced with silicon carbide particles is fabricated by melt-stirring method. The primary products of MMCs billets are prepared by volume fractions 5 vol% to 20 vol% and particle size $13\mu m$ to $22\mu m$.This paper will be made to examine the microstructure and mechanical properties of fabricated $SiC_p$/Al 6061 composite by melt-stirring and squeeze casting method. The MMC billets is extruded at $500^{\circ}C$ under the constant extrusion velocity $V_e$=2mm/min using curved shape die. Extrusion force, particle rearrangement, micro structure and mechanical properties of extruded composites will be investigated. The mechanical properties of primary billets manufactured by melt-stirring and squeeze casting method will be compared with extrusion specimen. The effect of volume fraction and size of the reinforcements will be studied. The increase in uniformity of particle dispersion is the major reason for an improvement in reliability due to hot extrusion with optimal shape die. Experimental Young's modulus and 0.2% offset yield strength for the extruded MMCs will be compared with theretical values calculated by the Eshelby method. A method will be proposed for the prediction of Young's modulus and yield strength in $SiC_p$ reinforced MMCs.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.63-71
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• 2004

Recently, a sheet forming process of Mg alloys is highlighted again due to increasing demand for Mg wrought alloys in the applications of casings of mobile electronics and outer-skins of light-weight transportation. Microstructure control is essential for the enhancement of workability and formability of Mg alloy sheets. In this research, AZ31 Mg alloy sheets were prepared by hot rolling process and the rolling condition dependency of the microstructure and texture evolution was studied by employing a conventional rolling mill as well as an asymmetric rolling mill. When rolled through multiple passes with a small reduction per pass, fine-grained and homogeneous microstructure evolved by repetitive dynamic and static recrystallization. With higher rolling temperature, dynamic recrystallization was initiated in lower reduction. However with increasing reduction per pass, deformation was locallized in band-like regions, which provided favorable nucleation sites f3r dynamic recrystallization. Through post annealing process, the microstructures could be transformed to more equiaxed and homogeneous grain structures. Textures of the rolled sheets were characterized by $\{0002\}$ basal plane textures and retained even after post annealing. On the other hand, asymmetrically rolled and subsequently annealed sheets exhibited unique annealing texture, where $\{0002\}$ orientation was rotated to some extent to the rolling direction and its intensity was reduced.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.10
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• pp.1239-1249
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• 2013

In this study we establish a process to predict hardening behavior considering the Bauschinger effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Bauschinger effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with FEA. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.