• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.11a
• /
• pp.248-251
• /
• 2002

In the electrophoresis for fabrication of a superconducting wire and film, the enough deposition and formal sustain of a film condition affect to superconducting state of samples. In this paper, a superconducting film was fabricated with various suspension solution such as acetone, buthanol, and ethanol. As a results, the best deposition condition with d.c 250 V and a.c 25 V of applied voltage, and 90 sec of applied time for BSCCO superconducting film by electrophoresis was investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.04a
• /
• pp.37-40
• /
• 2002

Superconductor wire fabricated by electrophoresis showed its critical current density depended on parameters such as applied voltage and deposition time. Substrate and suspension solutions. and its properties are also important parameters. When same optimal parameter and condition was used, deposition density of superconductor film affect directly its critical current density. In this study, therefore, electrophoretic deposition technique was utilized for a densification of YBCO superconducting wire, and researches on electrophoretic suspension solutions and additive were experimentally performed for an improvement of the critical current density of fabricated electrophoretically superconducting wire. The samples fabricated in the solution with the additive, 8 vol.% of 1% PEG(1000), showed the highest critical current density.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.23 no.6
• /
• pp.325-328
• /
• 2013

Phosphate has been removed in waste water by chemically synthesized graphene oxide. Removing efficiency of phosphate was investigated using phosphate dispersion aqueous solution, and 70 % of phosphate was removed in phosphate dispersion solution by chemically synthesized graphene oxide solution. Removing efficiency of phosphate was increased from 70 % to 80 % with assistant of iron nano-particle in chemically synthesized graphene oxide solution. Phosphate removing capacity was up to 89.37 mg/g at initial phosphate concentration of 100 mg/l and temperature of 303 K. The Freundlich was applied to describe the equilibrium isotherms and the isotherm constants were determined.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.123-126
• /
• 2003

The electrophoretic deposition method using the suspension solution with additives under the electric potential was applied for the fabrication of YBCO superconductor wire. This method was able to simplify the fabrication facilities, and produce an uniform and dense thick film. To improve the critical current density of deposited films, the additive PEGs(Poly Ethylene Glycole) with the molecular weight of 600, 1000 and 3400, were used as chemical binders for the suspension solution. The organic additive PEG showed better effects to the properties of YBCO superconductor wire. The PEG improved the adhesion between superconductor particles and suppressed the crack on the surface, which enhanced the surface uniformity and density of YBCO deposited film. It was found that acetone suspension solution showed better deposition properties than the others. The samples fabricated in the solution with the additive, 8 vol.% of 1% PEG(1000), showed the highest critical current density measured as $2300{\sim}2400\;Acm^2$ at 77 K, 0 T.

• Journal of the Speleological Society of Korea
• /
• no.75
• /
• pp.49-54
• /
• 2006

Electrophoretic Deposition (EPD) is the most convenient technology to deposit natural or oxide powders of nonconductive materials in alcoholic suspension solution with adding electrolyte of iodine to form ceramic thick film on metal substrate under applied electric field with double electric layer between electrode and metal substrate. In this research work, the important parameters and technical ways were studied to form EPD thick films of typical oxide ceramics of Al2O3, YBCO and tourmaline powders.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
• /
• v.3 no.1
• /
• pp.29-34
• /
• 2000

This paper proposes a long-term prediction of offshore structures in ocean waves. All short-term statistics is generated by the simulation for all the combinations of significant wave heights and spectral peak periods. The simulation has been tested first on linear system, whose analytic solution is known, to verify if the simulation works accurately. Then the scheme was applied to the nonlinear system. This paper demonstrated that the proposed scheme could be an efficient tool in estimating the response of offshore structures.

• Journal of Korea Port Economic Association
• /
• v.31 no.1
• /
• pp.37-49
• /
• 2015

According to outstanding maritime economists from domestic and overseas, shipping lines or ships' enlargement reduce fixed costs, and assist realization of scale of economy of shipping. On the contrary, recent Korean liquidity crisis on the shipping lines (SL) has been focused on the leading companies such as Hanjin Shipping (HJS), Korealines, and STX Pan Ocean. In this respect, this study aims to review Korean SLs' strategies and suggest the optimal solution between the specialization and enlargement. For these purposes, this research adopts slack based measure data envelopment analysis (SBM-DEA) model as a research methodology. As for decision making units (DMUs), SLs which have increased the vessel numbers and belonged to top tier group in year 2013, are selected. The results are comprised with two aspects. Firstly, HJS, KMTC, Korea LNG Trading (KLT), EUKOR, and Sinokor Tanker show the most efficient in regard to constant return to scale (CRS) model. Secondly, HJS, KMTC, KLT, Daerim, Chungang, Sinnokor Tanker, and EUKOR are the most efficient companies in terms of variable return to scale (VRS) model. Lastly, these results could be affected to the management philosophy and can answer the following question. Which is the most optimized SL?s management decision making, enlargement or specialization?

• Management & Information Systems Review
• /
• v.36 no.3
• /
• pp.89-111
• /
• 2017

The era of today's day is that the era of the black gold age is now approaching the era of the blue gold age. As the importance of water increases, support and policies for the water industry are presented. The water industry is a public service industry but it faces the problem for unbalanced supply between users. One of solutions for solving the problem at hand is the privatization of the public service and it is the most sensitive and focused subject to the issue. Korea is also coming up for the privatization of the water industry. So, one of the privatization operations based on the privatization of the current waterworks law is management contract by the specialized organization and it is in progress to enhance the efficiency of public services. Therefore, this study aims at finding out the local water supply services' efficiency by K-Water using DEA(Data Envelopment Analysis), and productivity analysis by malmquist index on 18 organizations of the implementation of local water supply management contract using the date from 2012 to 2014. According to the result of the DEA, 10 of the 18 organizations were the most efficient during 3 years and malmquist index for analysing the productivity was decreasing. That is because of the leakage ratio and utilization ratio of the raw water and both of them are significant to productivity. As a result, this study differs from the previous studies by analysing efficiency and productivity using DEA and malmquist index to the solution for the problem faced by current water industry.

• Journal of Distribution Science
• /
• v.16 no.5
• /
• pp.91-101
• /
• 2018

Purpose - This study compares the management efficiency of retailers in China, Korea and other global countries. China's retail industry is experiencing a recession. In order to strengthen the competitiveness of retailers, it is necessary to manage the efficiency. Therefore, we analyzed the management efficiency of Chinese retailers as well as Korea and global retailers who are competing with Chinese retailers. Research design, data, and methodology - The DEA(Data Envelopment Analysis) carried out for evaluating the relative efficiency of multiple DMUs (decision making units) with homogeneity. Data were collected from the American Retail Trade Association (2017). In those distributors' data, 5 of China and 5 of Korea and 10 of other global countries' analyzed. CCR and BCC analysis were performed to determine the cause of the inefficiency of DMUs by measuring the technical efficiency, pure technology efficiency and scale efficiency. Result - Among the 20 retail distributors, Costco, Kroger (Global), Eland World, BGF(Korea) are operating efficiently. Chinese retailers are operating inefficiently. Retailers' CRS status means the growth rate of input is equal to the growth rate of output. In the case of DRS status, the ratio of output to input variable is much smaller. In order to improve inefficiency, reducing input variables can be a solution. For the firms in IRS status, the rate of increase in output is relative greater than the input. That means efficiency is good condition. The analysis result shows that most retailers are showing DRS status especially Chinese retailers. Scale efficiency is a major cause of inefficiency rather than pure technology efficiency. It is recommended for ineffective retailers to reduce inputs to become efficient retailers. Otherwise, retrain existing employees or introducing advanced technologies to increase the output. Conclusions - Most of Chinese retailers are operating inefficiently which caused by the excessive investment in the inputs. On the other hand, Other global retailers are analyzed to be efficient by DEA. In this study, benchmarking targets of some retailers' suggested to improve the management efficiency especially in inputs.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.318-321
• /
• 2007

CdSe nanoparticles were prepared by chemical solution methods using $CdCl_2{\cdot}4H_2O$ (or $Cd(NO_3)_ 2{\cdot}4H_2O$) and $Na_2SeSO_3$. The characteristics of CdSe nanoparticles were controlled by the react ion time, reaction temperature and reaction method as well as the surfactants. Cetyltrimethyl ammonium bromide(CTAB) was used as a capping agent to control the chemical reactions in aqueous solution. Polyvinylalcohol(PVA) was used as a templet in sono-chemical method. CdSe nanoparticles synthesized in aqueous solution showed homogeneous size distribution with relatively stable surface. CdSe nanoparticles synthesized in non-aqueous solution containing diethanolamine(DEA) showed the structure transformation from cubic to hexagonal as the reduction temperature increased from 80 to $160^{\circ}C$. Core shell CdSe was synthesized by sono-chemical method. Characteristics of CdSe nanoparticles were analyzed using transmission electron microscopy(TEM), x-ray photoelectron spectroscopy(XPS), x-ray diffraction(XRD), UV-Vis absorption spectra, fourier transform infrared spectroscopy(FT-IR) and photoluminescence spectra spectroscopy(PL). This paper presents simple routes to prepare CdSe nanoparticles for solar cell applications.