• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.1
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• pp.55-60
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• 2020

The aim of this study was to investigate the change of microbial contamination levels in the different areas and at the different time points after application of a quaternary ammonium compound (QAC) that has mechanical antimicrobial effect. The microbial contamination levels were measured in three different areas; unit chair handle, spit sink area and hand piece holder at different time points using adenosine triphosphate (ATP) monitoring system and ATP surface test kit. Hand piece holder showed the highest level of microbial contamination. In most of the clinics, QAC significantly reduced the levels of microbial contamination, and maintained antimicrobial activity for 4 to 6 months. QAC may be used effectively in dental clinics due to the duration of antimicrobial effect and the minimal exposure of chemicals and further studies are needed with large sample size.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.3
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• pp.313-314
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• 2009

To project military power, the paradigm of the modern warship aquisition has evolved with more large platform and high-technology equipment. For example, the Aegis combat system equipped warship is one of the most advanced and capable defense systems currently in use. Concurrently, if the warship attacked and disabled, it may worse the asymmetry of the battle field and it also depress the morale of the fleet. For that reason, to keep and protect few number of the big and high technology equipped warship from enemy is very important. At the present, the performance of unit weapon has enhanced remarkably. A Korean-built SS-209 class submarine, Lee Chun-ham, participated in Naval Exercise Tandem Thrust conducted in 1999, sink the target ship ex-USS Oklahoma by a single torpedo. USS Stark was struck on May 17, 1987, by two Exocet anti ship missiles and disabled. For this reason, susceptibility should be prior to vulnerability and recoverability. In this paper, deception ship which is small and chief but has very similar signatures to large and high technology equiped warship has conceptually studied by using systems engineering approach. And it may be a effective way to enhance the susceptibility of the key fighting power.

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.460-465
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• 2019

In this study, we aim to derive a solution from the structural analysis for electrical failure of single board computers for computing navigation information. By analyzing the characteristic factor, we identify that crack occur on the central processing unit board due to a certain structural problem, and that the physical effect by the crack make communication function be impossible to perform, which it causes booting error. In order to find the location of excessive stress causing the crack, structural analysis for the single board computer is done. From the structural analysis, the areas where stress concentration occurs are identified, and improvement methods changing the structures are developed. As a result, we shows that stresses are reduced entirely on the stress distribution for the improved structure. In addition, heat analysis shows that changing the structure to reduce stresses is not affect to the heat radiation, and the thermal resistance of the actual equipment is verified by measuring the temperature of the heat sink applied with the improved structure.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.1
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• pp.1-12
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• 2019

Objective: Significant concerns have been raised over chemical exposure and potential health risks such as increased cancer mortality among laboratory workers. The aim of this study was to investigate the overall exposure and unit task exposure levels of researchers in organic synthesis laboratories at universities. Methods: Seventy-seven personal Time-weighted average(TWA) samples and 139 task-based samples from four organic synthesis laboratories at two universities were collected over three days. The concentrations of acetone, chloroform, dichloromethane(DCM), diethyl ether, ethyl acetate, n-hexane, tetrahydrofuran(THF), benzene, toluene, and xylene were determined using the GC-FID. Results: The most frequently used chemicals in the laboratories were acetone, DCM, n-hexane, methanol, and THF. Carcinogens such as benzene, chloroform, and DCM were used in one or more laboratories. The TWA full-shift exposures of researchers to acetone was the highest(ND-59.3 ppm). Benzene was observed above the occupational exposure limit in 18-40% of the samples. The levels of exposure to organic solvents were statistically different by task(p<0.05), while washing task was the highest. Washing was not perceived as a part of the real lab tasks. Rather it was considered as simple dish-washing or experimental preparation and performed in an open sink where exposure to organic solvents was unavoidable. TWAs and task-based concentrations were compared by substance, which suggests that TWA-based assessment could not reflect short-term and high concentration exposures. Conclusions: Laboratory workers may be exposed to various organic solvents at levels of concern. TWA-based measurement alone cannot guarantee holistic exposure assessment among lab workers as their exposures are very dependent on their tasks. Further investigation and characterization for specific tasks and overall chronic exposures will help protect lab workers from unnecessary exposure to chemicals while they perform research.

• Applied Biological Chemistry
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• v.35 no.6
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• pp.449-456
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• 1992

Expermient were conducted to determine the effect of phosphorus stress on bacteroid content and energy status of soybean (Glycine max [L.] Merr.) nodules. Plants inoculated with Bradyrhizobium japonicum MN 110 were grown with P-stressed (0.05 mM-P) and control (1 mM-P) treatment in the greenhouse. Phosphorus stress decreased nodule mass per plant and nodule mass to whole plant mass ratio. Phosphorus concentration in leaf, stem and root tissues were reduced by 75% but in nodule tissue was reduced only by 40% under phosphorus stress during 3 week experimental period. The bacteroid content per unit nodule mass and the distribution of total nitrogen and total phosphorus among the bacteroid and plant cell fractions of nodule were not affected significantly by phosphorus stress. Regardless of phosphorus treatment, 22% of the nitrogen and 27% of the phosphorus in whole nodules were associated with the bacteroid fraction. The ATP and total adenylate concentrations in and energy charge of whole nodule were decreased 77%, 46% and 37%, respectively, by phosphorus stress. The ATP concentration in and energy charge of the host plant cell fraction of nodules were decreased 86% and 59%, respectively, but these parametres in bacteroid in nodules were not affected by phosphorus stress. These results indicated that nodule is a strong phosphorus sink and that nodule growth and development are regulated to maintain a high phosphorus and energy content in bacteroid even when the host plant is subjected to phosphorus deficiency.

• Journal of Korean Society of Forest Science
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• v.96 no.3
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• pp.235-244
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• 2007

Potentials of AR CDM project in North Korea are assessed and feasible land area for AR CDM project is estimated. According to our estimation, There could be 515,000 hectares of forest lands deforested before 1990 in North Korea and 8,854 hectares at the regional level of Gae-sung City, which are eligible for AR CDM project, based on researches of satellite image analyses conducted from 1980's to 1990's. A baseline scenario assumed 44.73 tones of carbon stored in soil per hectare with no vegetation above ground remained during the project period following the default value of IPCC's Good Practice Guidance for LULUCF considering soil structure, climate and land use of the project area. The scenario also assumes that black rocust (Robinia pseudoacacia) is planted and the CDM project is implemented for 20 years. The costs for producing greenhouse gases CER (certified emission reduction) credits include costs of tree planting and forest management, and costs of project negotiation and transactions for issuing the credits. It is estimated that 376 tones of carbon dioxide per hectare can be accumulated and 503 temporary CER credits per hectare and 265 long-term CER credits per hectare could be produced during the project period. It is estimated to cost US$ 4.04 and US$ 7.67 to provide one unit of temporary credit and long-term credit, respectively. These values can be regarded as the cost of conferring emission commitment of a country or a private entity. However, it is not clear which option is better economically because the replacement periods are different in these two cases.

• Ecology and Resilient Infrastructure
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• v.10 no.4
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• pp.161-170
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• 2023

We attempted to estimate the carbon accumulation of Hibiscus hamabo and Paliurus ramosissimus, semimangroves native to Jeju Island, by remote sensing and to build an artificial intelligence model that predicts its spatial variation with climatic factors. The aboveground carbon accumulation of semi-mangroves was estimated from the aboveground biomass density (AGBD) provided by the Global Ecosystem Dynamics Investigation (GEDI) lidar upscaled using the normalized difference vegetation index (NDVI) extracted from Sentinel-2 images. In Jeju Island, carbon accumulation per unit area was 16.6 t C/ha for H. hamabo and 21.1 t C/ha for P. ramosissimus. Total carbon accumulation of semi-mangroves was estimated at 11.5 t C on the entire coast of Jeju Island. Random forest analysis was applied to predict carbon accumulation in semi-mangroves according to environmental factors. The deviation of aboveground biomass compared to the distribution area of semi-mangrove forests in Jeju Island was calculated to analyze spatial variation of biomass. The main environmental factors affecting this deviation were the precipitation of the wettest month, the maximum temperature of the warmest month, isothermality, and the mean temperature of the wettest quarter. The carbon accumulation of semi-mangroves predicted by random forest analysis in Jeju Island showed spatial variation in the range of 12.0 t C/ha - 27.6 t C/ha. The remote sensing estimation method and the artificial intelligence prediction method of carbon accumulation in this study can be used as basic data and techniques needed for the conservation and creation of mangroves as carbon sink on the Korean Peninsula.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.55 no.4
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• pp.275-283
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• 2010

This experiment was conducted to construct process models to estimate grain weight (GW) and grain nitrogen content (GN) in rice. A model was developed to describe the dynamic pattern of GW and GN during grain-filling period considering their relationships with temperature, solar radiation and growth traits such as LAI, shoot dry-weight, shoot nitrogen content, grain number during grain filling. Firstly, maximum grain weight (GWmax) and maximum grain nitrogen content (GNmax) equation was formulated in relation to Accumulated effective temperature (AET) ${\times}$ Accumulated radiation (AR) using boundary line analysis. Secondly, GW and GN equation were created by relating the difference between GW and GWmax and the difference between GN and GNmax, respectively, with growth traits. Considering the statistics such as coefficient of determination and relative root mean square of error and number of predictor variables, appropriate models for GW and GN were selected. Model for GW includes GWmax determined by AET ${\times}$ AR, shoot dry weight and grain number per unit land area as predictor variables while model for GN includes GNmax determined by AET ${\times}$ AR, shoot N content and grain number per unit land area. These models could explain the variations of GW and GN caused not only by variations of temperature and solar radiation but also by variations of growth traits due to different sowing date, nitrogen fertilization amount and row spacing with relatively high accuracy.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.1
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• pp.104-111
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• 2007

As protein content of milled rice, generally used as a benchmark for rice eating quality, is greatly affected by N fertilization and nutrition status of rice plant, understanding its response to nitrogen rate and plant nitrogen status at different growth stage is important for recommending N fertilizer management for high quality rice production. The responses of milled-rice protein content were compared and quantified under various combinations of basal+tillering and panicle N application levels in 2001 and 2002. Protein content of milled rice was ranged from 6 to 9%, increasing significantly with increasing basal+tillering and panicle N rates. However, milled rice protein content was raised much greater by panicle N than by basal+tillering N fertilization. Even though basal+tillering N increased up to 20 kg/ha, protein content of milled rice was observed less than 7% in case that panicle N was applied below 1.8 kg/10a. Regression analysis revealed that nitrogen accumulated until harvest was partitioned with almost constant rates of 58.3% and 46.5% to panicle and milled rice, respectively. The partitioning rates was slightly but not significantly different between experimental years. Protein content of milled rice showed linear and quadratic responses to the shoot N accumulation until panicle initiation stage (PIS) ant shoot nitrogen accumulation from PIS to harvest, respectively. The increment of milled-rice protein content per unit N increase was much greater in shoot N accumulation from PIS to harvest than in that until PIS. Regardless of shoot N accumulation until PIS upto 8 kg/10a, protein content of milled rice was lower than 7% and ranged from 6.5 to 7.5% in case that shoot N accumulation from PIS to harvest was below 3.0 kg/10a and below 6.0 kg/10a respectively. It would be concluded that even under the same N accumulation until harvest milled rice protein content could be different according to the N fertilizer management and weather condition especially during ripening, providing rooms for controlling protein content by N fertilizer management without damage to grain yield.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.4
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• pp.361-371
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• 1992

For the increase of grain yield potential in rice, a low-tillering large panicled type has been suggested as an ideotype. A low-tillering plant type may have different yield potential and needs different cultural practices from that used in a high-tillering type for the maximum yield. This study was conducted to evaluate the grain yield performances of a low-tillering large panicled rice and high-tillering small panicled rice at different plant spacings, nitrogen(N) levels and seedling numbers per hill. A low-tillering large panicled genotype, IR25588 was compared with a high-tillering small panicled IR58. The grain yield of IR25588 was significantly higher than that of IR58 under a narrow spacing with high N level. The maximum yields of IR58 and IR25588 were reached at about 35,000 and 40,000 spikelets per m$^2$, respectively. The increased grain yield in IR25588 was mainly due to the increase in spikelet number per unit area which is the most precise indicator of grain yield in rice. The optimum spacing for the maximum yield was denser for IR25588 than that for IR58 under high N level. The intra-hill competition of the low-tillering type was lower than that of the high-tillering type. The higher dry matter production and bigger leaf area and culm weight were the main factors for increased grain yield in a low-tillering panicle weight type. Based on the results, the yield potential of a low-tillering panicle weight type was higher than that of a high-tillering panicle number type, especially under a close spacing with high N level.