• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.409-409
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• 2014

Recently hexagonal boron nitride (h-BN), III-V compound of boron and nitrogen with strong covalent $sp^2$ bond, is a 2 dimensional insulating material with a large direct band gap up to 6 eV. Its outstanding properties such as strong mechanical strength, high thermal conductivity, and chemical stability have been reported to be similar or superior to graphene. Because of these excellent properties, h-BN can potentially be used for variety of applications such as dielectric layer, deep UV optoelectronic device, and protective transparent substrate. Ultra flat and charge impurity-free surface of h-BN is also an ideal substrate to maintain electrical properties of 2 dimensional materials such as graphene. To synthesize a single or a few layered h-BN, chemical vapor deposition method (CVD) has been widely used by using an ammonia borane as a precursor. Ammonia borane decomposes into hydrogen (gas), monomeric aminoborane (solid), and borazine (gas) that is used for growing h-BN layer. However, very active monomeric aminoborane forms polymeric aminoborane nanoparticles that are white non-crystalline BN nanoparticles of 50~100 nm in diameter. The presence of these BN nanoparticles following the synthesis has been hampering the implementation of h-BN to various applications. Therefore, it is quite important to grow a clean and high quality h-BN layer free of BN particles without having to introduce complicated process steps. We have demonstrated a synthesis of a high quality h-BN monolayer free of BN nanoparticles in wafer-scale size of $7{\times}7cm^2$ by using CVD method incorporating a simple filter system. The measured results have shown that the filter can effectively remove BN nanoparticles by restricting them from reaching to Cu substrate. Layer thickness of about 0.48 nm measured by AFM, a Raman shift of $1,371{\sim}1,372cm^{-1}$ measured by micro Raman spectroscopy along with optical band gap of 6.06 eV estimated from UV-Vis Spectrophotometer confirm the formation of monolayer h-BN. Quantitative XPS analysis for the ratio of boron and nitrogen and CS-corrected HRTEM image of atomic resolution hexagonal lattices indicate a high quality stoichiometric h-BN. The method presented here provides a promising technique for the synthesis of high quality monolayer h-BN free of BN nanoparticles.

• Journal of Korean Society on Water Environment
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• v.20 no.4
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• pp.313-320
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• 2004

In this study, variable characteristics of drinking water and the influences on underground water reservoirs, rooftop water tanks, and service water pipes in the building were assessed. The influence of underground water reservoir material and water capacity on water quality also were assessed. The results are the following as; First of all, the drinking water passing through underground water reservoirs or service water pipes in the building, averagely metal component concentration more increased from percent of 41.3 to percent of 74.2 totally than other items of water quality. On the other hand, both residual chlorine and total solid highly decreased 65.6 percent and 35.3 percent, respectively. Therefore, it was thought that water quality could be getting worse for microorganism re-growth by residual chlorine reduction, and total solid also could be a cause for extraneous matters accumulated in water reservoir. Secondly, the variations on water quality of each stage for water supply system in the building were higher in water service pipes connected from rooftop water tanks to the tap than in underground water reservoirs. In addition to, among of twelve items on water quality, ten items on water quality except dissolved oxygen and residual chlorine increased. Therefore, it was thought that the influence of water service pipes connected from rooftop water tanks to the tap on water quality were higher than other stages of water supply system in the building. Thirdly, in case of materials of underground water reservoir, it was likely that the variation on water quality by stainless steel and concrete materials got some similar. In case of water capacity, the variations on water quality of underground water reservoirs over $1,000m^3$ higher than those under $1,000m^3$. That reasons was likely that the retention time(49.72 hours averagely) of underground water reservoirs over $1,000m^3$ was two times longer than it of those under $1,000m^3$(23.37 hours). Therefore, it was thought that the influence on water quality by materials were some similar, but in case of water capacity, the influence of underground water reservoirs were higher.

• Korean Journal of Food Science and Technology
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• v.41 no.3
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• pp.258-264
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• 2009

The principal objective of this study was to estimate the measurement uncertainty associated with determination of deoxynivalenol (DON), a mycotoxin generated by Fusarium strain, in food. In service of this goal, wheat as a food matrix was analyzed via high performance liquid chromatography-ultraviolet (HPLC-UV) detection using an immunoaffinity column for clean-up. The uncertainty sources in the measurement process were identified by sample weight, final volume, and sample concentration in extraction volume with components including standard stock solution, working standard solution, 5 standard solutions, calibration curve, matrix, and instrument. The expanded uncertainty for DON at a concentration of 300 ${\mu}g/kg$ was estimated as 71.62 ${\mu}g/kg$ using a coverage factor of two, which provides a confidence level of approximately 95%. The most influential component in the uncertainty sources was the recovery of the wheat matrix, followed by the calibration curve. These results indicate that all efforts may be directed toward reducing the uncertainties of the recovery of the wheat matrix and the calibration curve to obtain a reliable HPLC-UV method for DON analysis in wheat.

• Korean Journal of Food Science and Technology
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• v.40 no.3
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• pp.354-359
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• 2008

A survey for zearalenone contamination was conducted on 27 soy bean samples, 27 red bean samples, 16 black bean samples, 19 seoritae samples, 14 seomoktae samples, for a total of 127 commercial Korean samples. Zearalenone was quantified by the immunoaffinity column clean-up method with high performance liquid chromatography-fluorescence detection (HPLC-FLD), and was confirmed by liquid chromatography tandem mass spectrometry(LC-MS/MS). The limits of detection and quantification were $2.0{\mu}g/kg$ and $6.0{\mu}g/kg$, respectively. The recovery in the beans ranged from 82.2 to 98.4%. According to HPLC-FLD, zearalenone was detected in 13 samples (10.2% incidence), including 1 soybean and 12 red bean samples. The zearalenone contamination levels were in the range of 8.01${\sim}38.98{\mu}g/kg$. Finally, LC-MS/MS analysis was conducted in the contaminated samples to verify the results of HPLC-FLD. The LC-MS/MS results confirmed the presence of zearalenone in all 13 samples. The contamination level was lower than that of EU, which is below $100{\mu}g/kg$ for raw grains.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.3
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• pp.166-172
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• 1997

In order to exterminate effectively starfish, Asterias amurensis inhabited a village fishing grounds and shellfish farms on coast of Korea, Mop and sledge gear were made and sea trials for capture efficiency of starfish by each gear and towing distance were carried out by commercial dredger on the coast of Keojedo from April to May in 1995. As Starfish mop and sledge were slowly dragged over the bottom at the same time, starfish became entangled in bunches of twine and netting respectively. The gears were hauled up at intervals to remove the starfish and hand-picking operations on vessel were conducted. The results obtained are as follows : Two gears were smoothly slidden over the sea bottom and captured numerous starfish. The optimal towing distance by each gear was 300 to 500 m.The capture efficiency of starfish species by sledge was 57% compared with 43% of that by mop but mixed rate with fish or shellfish of the former was 21 times as high as that of the letter. It was concluded from sea trials that moping was effective in shellfish farms, because the mop outfit causes little damage to useful shellfishes and the mixture of starfish with fish or shellfish was low, whereas sledging can be used to clean uncultivated areas free of shellfish where starfish population is very heavy and common fishing grounds in which bottom material is rock or gravel.

• Journal of the Korean Wood Science and Technology
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• v.38 no.6
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• pp.532-540
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• 2010

The strength properties of wooden model retaining wall made of pitch pine (Pinus rigida Miller) was evaluated. Three different types of wooden model retaining wall were made of the 11cm square timber treated with CUAZ-2 (Copper Azole). The retaining wall was made into the 4 layers of crossbar and the 3 layers of vertical-bar, of which the size was 86 cm high, 200 cm long and 96 cm wide. Type I was control and in Type II 20 cm vertical-bars and 93 cm vertical-bars were arranged alternately to decrease wood usage. TypeIII was similar to TypeII except that the connection between crossbars was reinforced with the wooden armature. In each type, the strength properties of retaining wall were investigated by horizontal loading test and the deformation of structure by image processing (AICON 3D DPA-PRO system). In horizontal loading test of Type I, Type II and Type III was 63.17, 57.80, and 60.97 kN/m, respectively. The deformation of the top layer in Type II was 1.5 times larger than in Type I and Type III. Consequently, the economic efficiency and strength performance were better in Type III than in Type I and Type II.

• Journal of Korea Water Resources Association
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• v.48 no.12
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• pp.1051-1064
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• 2015

Currently, the H purification plant determines the hourly water intake amount based on operator experience and skill. Therefore, inevitably, there are deviations among operators. While meeting time-varying demand and maintaining the proper water level in the clean water reservoir, the methodology for minimizing electricity cost, when dealing with different electricity rate time zones, is a very complicated problem, which is beyond an operator's capability. To solve this problem, a linear programming (LP) model is proposed, which can determine the optimal hourly water intake amount for minimizing the daily electricity cost. It is shown that an inaccurate estimate for the hourly water usage in the demand areas causes the water level constraint to be violated, which is the weak point of the proposed LP method. However, several examples with real-field data show that we can practically and safely solve this problem with safety margins. It is also shown that the safety margin method still works effectively whether the estimate is accurate or not. The operators need not attend the site at all times under the proposed LP method, and we can additionally expect reductions in labor costs.

• Environmental and Resource Economics Review
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• v.16 no.2
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• pp.275-311
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• 2007

Hydrogen energy is emphasized as a substitutable energy of carbon-based energy system in the future, since it is non-depletable and clean energy. Long term vision of Korean government on the national energy system is to promote hydrogen energy by 15% of final energy demand until 2040. This study analyzes economic impacts of hydrogen energy development employing a dynamic CGE model for Korea. Frontier technology such as hydrogen energy is featured as slow diffusion at the initial stage due to the learning effect and energy complementarity. Without government intervention, hydrogen energy would be produced upto 6.5% of final energy demand until 2040. However, if government subsidizes sales price of hydrogen energy by 10%, 20%, and 30%, share of hydrogen energy would increase 9.2%, 15.2%, and 37.7% of final energy demand. This result shows that the slow diffusion problem of hydrogen energy as frontier technology could be figured out by market incentive policy. On the other hand, production levels of transportation sector would increase while growth rate of oil and electricity sectors would decline. Household consumption would be affected negatively since increase of consumption due to the price decrease would be overwhelmed by income reduction owing to the increase of tax. Overall, GDP would not decrease or increase significantly since total production, investment, and export would increase even if household consumption declines.

• Korean Journal of Food Science and Technology
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• v.44 no.2
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• pp.235-239
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• 2012

This research was conducted to monitor ochratoxin A in wine, beer, $makgeolli$ and fermented alcoholic beverages to estimate the exposure to ochratoxin A in the assorted alcoholic beverages. The analytical method for ochratoxin A was based on immuno-affinity column clean up followed by HPLC-FLD. Ochratoxin A was detected in 30 samples of 177 wine (17%), 25 samples of 106 beer (23.6%), 11 samples of 74 $makgeolli$ (14.9%), and 7 samples of 74 fermented alcoholic beverages (9.5%). The average levels of ochratoxin A were 0.039 ng/mL in wine, 0.010 ng/mL in beer, 0.023 ng/mL in $makgeolli$, and 0.014 ng/mL in fermented alcoholic beverages. The daily dietary exposure level of ochratoxin A estimated by using the report on national health and nutrition survey were 0.039 ng/b.w.day from wine, 0.010 ng/b.w.day from beer, 0.023 ng/b.w.day from $makgeolli$, and 0.014 ng/b.w.day from fermented alcoholic beverage.

• Health Policy and Management
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• v.22 no.2
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• pp.183-206
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• 2012

Changing social conditions have resulted in a situation where elderly patients are no longer cared for by family and where medical care hospitals play a more prominent role. In this study, the unique elements of the medical service required from a long term care hospital were identified using conventional and exploratory analysis, and the causal relationship between medical service quality, relationship quality, and Revist intent was confirmed. The intermediary role and the quantitative importance of relationship quality (including trust and commitment) were also characterized. This study identifies the key points and indicators that the administrators of a long term care hospital can use to effectively plan their medical service offering in order to secure the commitment of customers through relationship quality. The theoretical indications of this study are set out below. First, four factors are selected as being the key elements determining service quality: medics, administrative service, healthcare environment, and subsidiary facilities. Second, it seems that medics, administration service, and the healthcare environment have some effect on the evaluations made in relation to trust and satisfaction (subsidiary facilities are not considered to be a key element). Third, patient satisfaction has a positive impact on trust and commitment and can be regarded as a key element for establishing connections. Fourth, commitment is likely to be strengthened when trust is significant. Fifth, as trust and commitment increase, revist intent strengthens. Lastly, this study illustrates how the levels of trust and commitment play a modulating role between patient satisfaction and revist intention. There are many practical indications from the findings of this study. First, the influences of medics, the administrative service, and the healthcare environment on trust and satisfaction vary. Especially, the healthcare environment is likely to be more important than medics. Accordingly, it is essential to establish an elderly-friendly environment, to improve a hospital's structure, and to maintain a clean environment. Second, medics must show compassion to their patients and be patient when providing explanations to elderly patients who often lack powers of concentration. Third, in order to establish patient trust, it is essential that medics provide an excellent medical service. Ultimately, these elements of relationship quality may strengthen the revist intention of elderly patients.