• Industrial Engineering and Management Systems
• /
• v.12 no.2
• /
• pp.161-170
• /
• 2013

Deployment of green transportation in reverse logistics is a key issue for low carbon technologies. To cope with such logistic innovation, this paper proposes a hybrid approach to solve practical vehicle routing problem (VRP) of pickup type that is common when considering the reverse logistics. Noticing that transportation cost depends not only on distance traveled but also on weight loaded, we propose a hierarchical procedure that can design an economically efficient reverse logistics network even when the scale of the problem becomes very large. Since environmental concerns are of growing importance in the reverse logistics field, we need to reveal some prospects that can reduce $CO_2$ emissions from the economically optimized VRP in the same framework. In order to cope with manifold circumstances, the above idea has been deployed by extending the Weber model to the generalized Weber model and to the case with an intermediate destination. Numerical experiments are carried out to validate the effectiveness of the proposed approach and to explore the prospects for future green reverse logistics.

• Journal of Welding and Joining
• /
• v.7 no.1
• /
• pp.59-66
• /
• 1989

The weldability and joint performance were evaluated for newly developed 60kg/mm$\^$2/ steel which had low cold cracking susceptibility. The main results obtained were as follows; In case of quenched and tempered 60kg/mm$\^$2/ steels, it was very effective to improve weldability and joint performance by lowering carbon and Pcm level. Very small addition of about 0.001 to 0.002wt% boron exhibited an appreciable compensation effect on strength which was decreased by lowering carbon and Pcm level. As a result, the newly developed steel was able to be welded without preheating and exhibited superior joint performance to conventional steels.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.05a
• /
• pp.431-434
• /
• 2008

Effects of microstructure on the toughness of low carbon HSLA steels were investigated. Nickel decreased the ferrite-austenite transformation temperature, resulted in increase of the fraction of bainitic ferrite. However, it was decreased with increasing deformation amount at austenite region. Since fine austenite grains formed by dynamic recrystallization under large strain transformed to acicular ferrite or granular bainite rather than bainitic ferrite. The effective grain size, thus, was decreased by deformation and it resulted in lower ductile-brittle transition temperature (DBTT). The bainitic ferrite was thought to inhibit the fracture crack initiation and to delay the crack propagation by its high dislocation density and hard interlath $2^{nd}$ phase constituents, respectively. Thus, DBTT was also decreased by Ni addition in low carbon HSLA steels.

• STI Policy Review
• /
• v.2 no.1
• /
• pp.13-34
• /
• 2011

This paper investigates the interaction among the paradigm of Low-Carbon Society (LCS) and the megatrends in field of population, environment, geopolitics, and energy. The paradigm of LCS is regarded as a 'social will' trend, distinguished from other 'phenomenal' trends. The qualitative analysis shows that the megatrends and the LCS paradigm have positive/neutral/negative impacts on one another, while some impacts can be reversed to other types of impact with the conditions having ripened. In quantitative analysis, the correlation between the LCS paradigm and the economy is traced with our Integrated Assessment Model, looking into such response options as population control, increase in labor force participation, and productivity enhancement to maintain utility level despite the pursuit of LCS paradigm. The future challenges in national strategy and S&T policy are suggested, based on the interaction analyses.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.20 no.5
• /
• pp.620-632
• /
• 2017

A chemical vapor curing method(CVC) was developed to cure polycarbosilane(PCS) fibers by using cyclohexene vapour as a non-oxygen active reactant, instead of air in oder to prepare the silicon carbide(SiC) fiber with low oxygen content. A cross-linked PCS fibers by cyclohexene vapor showed a completely different variation in IR spectra in comparison to the air-cured PCS fiber. CVC method resulted in less than 3 wt% in oxygen content. In this experiment conditions, The average tensile strength and modulus of SiC fiber obtained by CVC had 1995 MPa and 183 GPa respectively, which is higher than that of SiC fiber prepared by air-curing process.

• Journal of the Korean Society of Industry Convergence
• /
• v.10 no.2
• /
• pp.89-96
• /
• 2007

For the environment protection, carbon dioxide as a natural refrigerant has been studied to use in an automotive air conditioning system. Hence, a numerical model has been developed to describe the evaporation phenomena of carbon dioxide flowing through very small diameter tubes. The two dimensional low-Reynolds $k-{\varepsilon}$ model was used to predict the flow phenomena of carbon dioxide in the two phase during its evaporation. Furthermore, the results obtained from the model were compared with the experiments for the validation. The heat transfer coefficient is lower, as the tube inner diameter becomes smaller. However, the amount of heat absorbed by a unit mass of carbon dioxide is greater due to more surface area. Therefore, the small diameter tube has advantage in terms of compact design of evaporator. When the inlet condition of pressure and temperature is low, the heat transfer coefficient is slightly high at the same size of tube because of the thermal properties of carbon dioxide.

• Journal of Korean Society for Atmospheric Environment
• /
• v.25 no.4
• /
• pp.316-324
• /
• 2009

Carbon based sorbents for $CO_2$ adsorption were prepared by impregnation with alkali metals ($Li^+$, $K^+$) and alkaline earth metals ($Ca^{2+}$, $Mg^{2+}$). BET surface area of test sorbents was lower than the intrinsic activated carbon. In particular, impregnation of $Ca^{2+}$ or $Mg^{2+}$ resulted in lower surface area of specific adsorption sites than that of $Li^+$ or $K^+$. While the adsorption capacity for $CO_2$ was high in the sorbents containing $Ca^{2+}$ and $Mg^{2+}$, strong interaction with $CO_2$ would cause to drop the capacity after regeneration. The adsorption was found high relatively in the flow with a high concentration of $CO_2$ and in a low flow rate. The adsorption isotherm for the present modified AC sorbents fits well with the Freundlich model.

• Macromolecular Research
• /
• v.11 no.2
• /
• pp.122-127
• /
• 2003

A glass-like carbon was fabricated using furan resin. The influence of heat treatment temperature during fabrication process on the chemical and micro-structural changes was studied by various analytical and spectroscopic methods including TGA, FT-IR, CHN, TEM and XRD. The chemical resistance properties of the fabricated glass-like carbon were also investigated. It has been found that the heat-treated samples at higher temperature up to 2600 $^{\circ}C$ in $N_2$ atmosphere had little weight loss, small amounts of functional groups, and high carbon content. The fabricated glass-like carbons upon heat treatment at 2600 $^{\circ}C$ showed an amorphous stage without any grain growth and/or reconstruction of structure. The glass-like carbon had much better chemical resistance than the artificial graphite, and exhibited a high chemical resistance due to its low surface areas, minimum impurities, and low graphite crystallites.

• Journal of the Korean Solar Energy Society
• /
• v.33 no.2
• /
• pp.108-117
• /
• 2013

Studies on the regulation and measurement of greenhouse gases(GHGs) emissions have been carrying out for global wanning. In order to reduce greenhouse gas emissions, many countries have been promoting the Emissions Trading System and projects of the Joint Implementation(JI) and Clean Development Mechanism(CDM). These country's GHG emissions have been measured calculation criteria based on the Intergovernmental Panel on Climate Change(IPCC) Guidelines. In order to respond to GHGs regulation, in each country, it is planing to build a Low-Carbon City. The system has been developed for calculating GHGs emissions from companies and institutions in their respective countries. However, the system can monitor the GHGs per city, has not been developed. In this paper, it is studied to design the User Interface and to develop integrated monitoring program for Low-carbon city. This program will make possible monitoring and management, statistics, and reports written by using each data in units of cities.

• Journal of Microbiology
• /
• v.45 no.4
• /
• pp.311-317
• /
• 2007

In this study, the effects of phosphate concentration and carbon source on the patterns of alkaline phosphatase (APase) and phospholipase (PLase) expression in Vibrio vulnificus ATCC 29307 were assessed under various conditions. The activities of these enzymes were repressed by excess phosphate (4 mM) in the culture medium, but this repression was reversed upon the onset of phosphate starvation in low phosphate defined medium (LPDM) containing 0.2 mM of phosphate at approximately the end of the exponential growth phase. The expressions of the two enzymes were also influenced by different carbon sources, including glucose, fructose, maltose, glycerol, and sodium acetate at different levels. The APase activity was derepressed most profoundly in LPDM containing fructose as a sole carbon source. However, the repression/derepression of the enzyme by phosphate was not observed in media containing glycerol or sodium acetate. In LPDM-glycerol or sodium acetate, the growth rate was quite low. The highest levels of PLase activity were detected in LPDM-sodium acetate, followed by LPDM-fructose. PLase was not fully repressed by high phosphate concentrations when sodium acetate was utilized as the sole carbon source. These results showed that multiple regulatory systems, including the phosphate regulon, may perform a function in the expression of both or either APase and PLC, in the broader context of the survival of V. vulnificus.