• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.388-388
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• 2016

Chemical mist deposition (CMD) of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was investigated with cavitation frequency f, solvent, flow rate of nitrogen, substrate temperature $T_s$, and substrate dc bias $V_s$ as variables for efficient PEDOT:PSS/crystalline (c-)Si heterojunction solar cells (Fig. 1). The high-speed camera and differential mobility analysis characterizations revealed that average size and flux of PEDOT:PSS mist depend on f, solvent, and $V_s$. The size distribution of mist particles including EG/DI water cosolvent is also shown at three different $V_s$ of 0, 1.5, and 5 kV for a f of 3 MHz (Fig. 2). The size distribution of EG/DI water mist without PEDOT:PSS is also shown at the bottom. A peak maximum shifted from 300-350 to 20-30 nm with a narrow band width of ~150 nm for PEDOT:PSS solution, whose maximum number density increased significantly up to 8000/cc with increasing $V_s$. On the other hand, for EG/water cosolvent mist alone, the peak maximum was observed at a 72.3 nm with a number density of ~700/cc and a band width of ~160 nm and it decreased markedly with increasing $V_s$. These findings were not observed for PEDOT:PSS/EG/DI water mist. In addition, the Mie scattering image of PEDOT:PSS mist under white bias light was not observed at $V_s$ above 5 kV, because the average size of mist became smaller. These results imply that most of solvent is solvated in PEDOT:PSS molecule and/or solvent is vaporized. Thus, higher f and $V_s$ generate preferentially fine mist particle with a narrower band width. Film deposition occurred when $V_s$ was impressed on positive to a c-Si substrate at a Ts of $30-40^{\circ}C$, whereas no deposition of films occurred on negative, implying that negatively charged mist mainly provide the film deposition. The uniform deposition of PEDOT:PSS films occurred on textured c-Si(100) substrate by adjusting $T_s$ and $V_s$. The adhesion of CMD PEDOT:PSS to c-Si enhanced by $V_s$ conspicuously compared to that of spin-coated film. The CMD PEDOT:PSS/c-Si solar cell devices on textured c-Si(100) exhibited a ${\eta}$ of 11.0% with the better uniformity of the solar cell parameters. Furthermore, ${\eta}$ increased to 12.5% with a $J_{sc}$ of $35.6mA/cm^2$, a $V_{oc}$ of 0.53 V, and a FF of 0.67 with an antireflection (AR) coating layer of 20-nm-thick CMD molybdenum oxide $MoO_x$ (n= 2.1) using negatively charged mist of 0.1 wt% 12 Molybdo (VI) phosphoric acid n-Hydrate) $H_3(PMo_{12}O_40){\cdot}nH_2O$ in methanol. CMD. These findings suggest that the CMD with negatively charged mist has a great potential for the uniform deposition of organic and inorganic on textured c-Si substrate by adjusting $T_s$ and $V_s$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.6
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• pp.327-340
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• 2017

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.

• Korean Journal of Environment and Ecology
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• v.34 no.1
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• pp.18-26
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• 2020

Echinosophora koreensis (Nakai) Nakai an endemic plant with limited distribution in some parts of the Korean Peninsula, is designated as "Endangered" species on the IUCN Red List. The species is under the threat of deterioration in nature due to various environmental changes causing loss of natural habitats. We investigated the distribution pattern and population structure of E. koreensis to serve as a basic reference for identifying the dynamics and persistence of natural populations of this species in the future. To determine the characteristics of the E. koreensis population, we laid two to three large plots sized 20m×30m on the ridgeline as the reference in Yanggu, Chuncheon, and Hongcheon and laid four to seven small quadrats sized 1m×1m on the transect. A total of 530 plots were laid, 10 each at 2m interval, to measure the number of the stems, the number of fruiting, height, and other factors. The collected distribution information was compared with the existing IUCN assessed categories by applying IUCN Red List ver 3.1 Criteria B. The average population density of the three surveyed areas was 3.47 stem/㎡; the density of each area was 3.95 stems/㎡ in Yanggu, 3.37 stems/㎡ in Chuncheon, and 2.87 stems/㎡ in Hongcheon. The number of fruiting per stem was 0.0038, indicating only 7 fruits out of 1,837 stems and that vegetative reproduction is likely to be more dominant than sexual reproduction. The distribution tendency of population density in the small plots in three surveyed areas showed that the density of E. koreensis tended to decrease toward the center of the forest with low crown openness and around the mountain ridge with high crown openness. It indicated that the quantity of light could be a very important factor for the growth of individuals of this species. The analysis of the heights of individuals present in the surveyed plots showed a range of 2.3 ~ 68.5cm and an average of 20.1cm. An analysis on the stage-structure of the E. koreensis population based on the sieve height found that the appearance frequency decreased with increasing height above 15 ~ 20cm and that the percentage of individuals lower than 10cm, which were presumed to be seedlings, was severely low, indicating a necessity of study on the population sustainability based on the monitored data. The occupied area calculated with the collected species distribution information was 200㎢, indicating the EN category according to the IUCN Red List Reference B.

• The korean journal of orthodontics
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• v.33 no.1 s.96
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• pp.51-61
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• 2003

The purpose of this study was to evaluate the effects of a self-etching primer on the shear bond strength of orthodontic brackets and on the failure pattern of bracket-adhesive interfaces in dry or wet condition. Brackets were bonded to extracted human teeth according to one of three experimental protocols. In the Group P, teeth were etched with $37\%$ phosphoric acid. After the Transbond XT Primer was applied onto the etched surfaces, the brackets were bonded with Transbond XT(3M, Unitek, Monrovia, Calif) and light cured for 40 seconds. In the Group SD, a self-etching primer(3M, Unitek, Monrovia, Calif) was placed on the enamel for 3 seconds and gently evaporated with air, as suggested by the manufacturer. The brackets were then bonded with Transbond XT as in the Group P In the Group SW, artificial saliva was applied to the enamel surface for 10 seconds to allow complete hydration of the surface before application self-etching primer The brackets were then bonded following the procedures of Group SD. Each group was divided into 2 sub-groups(0.5h, 24h) according to debonding time. Shear bond strengths were measured by Instron universal testing machine. After debonding, the teeth and brackets were examined under scanning electron microscope and assessed with the adhesive remnant index. The result obtained were summarized as follows ; 1. The shear bond strengths were high enough to use clinically in all testing groups, but the shear bond strengths of Group SD and SW were significantly lower than Group P(p<0.05). 2. With respect to comparison of debonding time, 24h debonding samples exhibited heigher shear bond strength than 0.5h debonding samples in Group P, SD and SW(p<0.05). 3. In the self etching primer groups(Group SD and Group SW), there was no significant difference in mean shear bond strength between under dry and wet state(p>0.05). 4. There was a greater frequency of ARI score of 0 and 1 with the Group P. On the other hand, there was a higher frequency of ARI scores of 2 and 3 with Group SD and Group SW(p<0.05).

• Restorative Dentistry and Endodontics
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• v.27 no.4
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• pp.355-362
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• 2002

One fifth dilution of formocresol is usually used for pulpotomy of the primary teeth and emergency pulpotomy of the permanent teeth. However the use of formaldehyde has been subjected to criticism because it may be absorbed into the blood stream and become distributed systemically, it nay also alter the pulp tissue rendering it immunologically active, and have carcinogenic potential. Recently Depulpin$^{\circledR}$(VoCo., Germany) gains popularity as a devitalizing agent during root canal therapy in spite of high concentration of 49 % paraformaldehyde because it facilitate devitalization of pulp and make root canal therapy easier But there have been not enough publications about the reaction of pulp and periapical tissue caused by Depulpin. This study was performed to evaluate the histological changes in pulp and periapical tissue of rats after pulpotomy using formocresol and Depulpin and to elucidate the toxic effects of these agents. Thirty six Sprague-Dawley rats were anesthetized by intraperitoneal injection of ketamine Maxillary first molar teeth were used for pulpotomy with formocresol and Depulpin. Rats were sacrificed after 2 days, 4 days, 1 week, 2 weeks, 3 weeks and 4 weeks respectively. Specimens were histologically observed by light microscope changes in pulp and periapical tissue. The obtained results were as follows. 1. Formocresol group A zone of fixed tissue. in which odontoblasts could clearly be defined, was present directly underneath the pulpotomy dressing in almost all teeth of this group. This was followed by an area of necrotic tissue which resembled dried out fibrous tissue with no cellular detail except some pyknotic nuclei. In the specimens of after 2 days, 4 days, 1 week, 2 weeks in which vital tissue was present, it was separated from the fibrous area by a zone of inflammation. In the specimens of after 3 weeks and after 4 weeks, inflammatory infiltrate was in the periodontal ligament adjacent to the apical foramina of the teeth. 2. Depulpin$^{\circledR}$ group The area of necrotic tissue which had no cells and fibers, was present adjacent to the dressing. This was followed by dried out fibrous tissue with no cellular details except some pyknotic nuclei, A short stump of vital pulp with odontoblasts was present at the end of the canal after 2 days. Inflammatory infiltrate was in the periodontal ligament after 4 days and after 1week. Severe root resolution and necrosis of periapical tissue opposite the root resorption site were defined after 2 weeks and after 3 weeks. Periapical lesion which consist of necrotic tissue surrounded by a fibrous connective wall, was found after 4 weeks. The results indicated that Depulpin can cause more adverse reaction to the dental pulp and periapical tissue than formocresol, and further studies are needed for its clinical use with safety.

• Journal of the Korean Vacuum Society
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• v.14 no.2
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• pp.78-83
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• 2005

Nanometric crystalline silicon (no-Si) embedded in dielectric medium has been paid attention as an efficient light emitting center for more than a decade. In nc-Si, excitonic electron-hole pairs are considered to attribute to radiative recombination. However the surface defects surrounding no-Si is one of non-radiative decay paths competing with the radiative band edge transition, ultimately which makes the emission efficiency of no-Si very poor. In order to passivate those defects - dangling bonds in the $Si:SiO_2$ interface, hydrogen is usually utilized. The luminescence yield from no-Si is dramatically enhanced by defect termination. However due to relatively high mobility of hydrogen in a matrix, hydrogen-terminated no-Si may no longer sustain the enhancement effect on subsequent thermal processes. Therefore instead of easily reversible hydrogen, phosphorus was introduced by ion implantation, expecting to have the same enhancement effect and to be more resistive against succeeding thermal treatments. Samples were Prepared by 400 keV Si implantation with doses of $1\times10^{17}\;Si/cm^2$ and by multi-energy Phosphorus implantation to make relatively uniform phosphorus concentration in the region where implanted Si ions are distributed. Crystalline silicon was precipitated by annealing at $1,100^{\circ}C$ for 2 hours in Ar environment and subsequent annealing were performed for an hour in Ar at a few temperature stages up to $1,000^{\circ}C$ to show improved thermal resistance. Experimental data such as enhancement effect of PL yield, decay time, peak shift for the phosphorus implanted nc-Si are shown, and the possible mechanisms are discussed as well.

• Journal of Korean Society of Forest Science
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• v.106 no.4
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• pp.487-496
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• 2017

The marketization in North Korea is spreading rapidly. This study proposes forest rehabilitation strategy for North Korea in light of their major shift toward market economy. This current trend of marketization in North Korea is now affecting the forest sector, especially the way the residents utilize small forest land. For analyzing the influence of marketization on forest management in North Korea, we reviewed the official documents issued by North Korea and related materials of North Korean marketization. The government of Kim Jong Eun has set up policies and systems regarding the spread of marketization, such as guaranteeing individuals a right to dispose certain products on their own and establishing a special economic zone to attract foreign investments. In the forestry sector, the North Korean government has been trying to fully implement its forest restoration plan by carrying out measures like re-claiming of sloping lands that had been previously used by residents. However, as marketization progresses, it is expected that there lies much difficulty in government-led massive mobilization for forest restoration due to the increase of illegal logging to meet high demand for timber, illegal firewood harvesting, collecting non-timber products for livelihoods and illegal crop cultivation to sell in the market. Therefore, South Korea's support for forest restoration should also consider the recent marketization phenomenon in North Korea. It is necessary to formulate strategic measures such as conducting joint commercialization project on agroforestry management using cooperative farming unit, helping to improve income source from small forest lands, and to activate a comprehensive mountain village special economic zone by utilizing forest business. We do hope that our proposed forest rehabilitation strategy in this paper regarding the changes in North Korea's marketization and forest policy can give a meaningful suggestion on supporting forest restoration in North Korea in an effective way.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.1
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• pp.69-80
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• 2007

Among the photoactive semiconductors such as $TiO_2,\;ZnO,\;Fe_2O_3,\;WO_3,\;and\;CdSe,\;TiO_2$ is the most widely used as photocatalyst in different media, because of its lack of toxicity and stability. In this study, the effects of titanium dioxide were investigated to obtain the information of physiological change in rice plant. Light-adapted Chlorophyll flourescence index decreased and relative electron transport rate of rice leaves was activated by titanium dioxide under $2,400\;{\mu}mol\;m^{-2}\;s^{-1}$ PAR (Photosynthetic active radiation). Relative electron transport rate of rice leaf treated with titanium dioxide 10 ppm was high in order of $2,400\;{\mu}mol\;m^{-2}\;s^{-1}\;PAR,\;2,200\;{\mu}mol\;m^{-2}\;s^{-1}\;PAR,\;450\;{\mu}mol\;m^{-2}\;s^{-1}\;PAR$ and titanium dioxide 10 ppm (45.1%), control (32.4%), diuron 10 ppm (15.3%) under $2,400\;{\mu}mol\;m^{-2}\;s^{-1}\;PAR$. Titanium dioxide increased photosynthesis of the rice leaf under $13.6\;KJ\;m^{-2}\;day^{-1}$ UV-B only. With titanium dioxide 20 ppm, reduced UV-B ($0.15\;KJ\;m^{-2}\;day^{-1}$) intensity changed the induction of proteins and twenty-five proteins were identified. Among them, seventy proteins were up-regulated, four proteins were down-regulated and four proteins were newly synthesized. Function of these proteins was related to photosynthesis (52%), carbohydrate metabolism (4%), stress/defense (8%), secondary metabolism (4%), energy/electron transport (4%), and miscellaneous (28%).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.4
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• pp.377-385
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• 2020

Recently, wheat consumption has been increasing in Korea, requiring increased production. Nitrogen fertilization is a critical determinant in crop yield; therefore, it is necessary to optimize the nitrogen fertilization regime with current trends that emphasize the minimum impact of nitrogen fertilizer on the environment. In this study, both nondestructive spectral analysis using a hyperspectral camera and growth analysis were performed to determine the optimal N top-dressing rates after heading. The nitrogen application regimes consisted of three conditions according to the secondary top-dressing rate: N_4:3:0 (0 kg 10 a^-1), N_4:3:3 (2.73 kg 10 a^-1), and N_4:3:6 (5.46 kg 10 a^-1). Subsequently, growth and physiological investigations were performed at the jointing, heading, and ripening stages of wheat, and spectral investigations were conducted. On April 29, as the nitrogen fertilization rate was increased to N_4:3:3 and N_4:3:6, plant height and grain yield increased by 4% and 8%, and 8% and 52%, respectively, compared to those under N_4:3:0. Leaf area index and SPAD value also increased by 13% and 24%, and 32% and 43%, respectively. The R (red), G (green), and B (blue) of leaf color were lowered by 15, 11, and 4 in N_4:3:3 and 44, 34, and 18 in N_4:3:6, respectively, as compared to the control. Grain yield was the highest at high top-dressing (N_4:3:6), however, there was no difference between no top-dressing (N_4:3:0) and intermediat top-dressing (N_4:3:3). The reflectance analyzed using a hyperspectral camera showed a difference in the near-infrared (NIR) region on March 19, and on April 29, there was a difference both in the visible light region greater than 550 nm and the NIR region. Vegetation indices differed according to fertilization regime, except for the greenness index (GI). The results of this study showed that not only growth and physiological analysis but also spectral indices can be used to optimize the nitrogen top-dressing rate.

• Journal of Bio-Environment Control
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• v.25 no.2
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• pp.111-117
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• 2016

The objective of this study was to analyze the microclimate and the growth of tomato and lettuce in the greenhouses covered with spectrum conversion films using different phosphor particles sizes. Two spectrum conversion films using phosphor particles larger than $10{\mu}m$ (Micro-film) and smaller than 500 nm (Nano-film) in radius, and poly-ethylene (PE) film were used in double-layered greenhouses as outer coverings. PE films were used as inner coverings in all the greenhouses. Thickness of the films for inner and outer coverings was 0.06 mm. Tensile strength, elongation, and tearing resistance of the Micro- and Nano-films were not different from those of the PE film. Transmittances at a wavelength of 300-1100 nm were a little higher at the Micro-film and lower at the Nano-film than that of the PE film, respectively. Air temperatures at the Micro- and Nano-films were over $2^{\circ}C$ higher than at the PE film, but no significant difference was observed between the two light conversion films. The soil temperature at the Nano-film was $1.5^{\circ}C$ and $3^{\circ}C$ higher than at the Micro- and PE films, respectively. The yields of tomato at the Micro- and Nano-films were 12% and 14% higher than at the PE film, but no significant difference was observed between the two spectrum conversion films. The total soluble solid showed no significant differences among all the films. The yields of lettuces at the Micro- and Nano-films were 27% and 59% higher than at the PE film. Hunter's red (a) value of the lettuce leaf was the highest at the Nano-film. In this experiment, tomatoes requiring high irradiation were better at the Nano film, while lettuce requiring low irradiation better at the Micro film.