• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.780-789
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• 2008

A new method for measuring the performance of a micro-thruster is suggested in this paper. A few thrust stands have been developed for measuring micro-level thrusts. This paper describes a different measurement method that can minimize the calibration involved in the measurements, while providing the capability of directly measuring the produced minimum impulse bit directly. The underlying theory and the theoretical background for the measurement mechanism are described here. The theory and method is verified using a computer simulation, and the result is given in this paper. The theory has also been tested on an actual hardware. Although this hardware is a prototype, developed for proof-of-concept analysis, satisfactory results have been obtained.

• Toxicological Research
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• v.34 no.2
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• pp.163-172
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• 2018

Air pollution is increasing, along with consumption of fossil fuels such as coal and diesel gas. Air pollutants are known to be a major cause of respiratory-related illness and death, however, there are few reports on the genotoxic characterization of diverse air pollutants in Korea. In this study, we investigated the mutagenic activity of various particles such as diesel exhaust particles (DEP), combustion of rice straw (RSC), pine stem (PSC), and coal (CC), tunnel dust (TD), and road side dust (RD). Ultra-fine particles (UFPs) were collected by the glass fiber filter pad. Then, we performed a chemical analysis to see each of the component features of each particulate matter. The mutagenicity of various UFPs was determined by the Ames test with four Salmonella typhimurium strains with or without metabolic activation. The optimal concentrations of UFPs were selected based on result of a concentration decision test. Moreover, in order to compare relative mutagenicity among UFPs, we selected and tested DEP as mutation reference. DEP, RSC, and PSC induced concentration-dependent increases in revertant colony numbers with TA98, TA100, and TA1537 strains in the absence and presence of metabolic activation. DEP showed the highest specific activity among the particulate matters. In this study, we conclude that DEP, RSC, PSC, and TD displayed varying degrees of mutagenicity, and these results suggest that the mutagenicity of these air pollutants is associated with the presence of polycyclic aromatic hydrocarbons (PAHs) in these particulate matters.

• Asia pacific journal of information systems
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• v.20 no.4
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• pp.1-23
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• 2010

Some researches insist that, to participate in an e-partnership, a distributor needs a given level of trust to reduce the perceived risk of an e-partnership to his/her own threshold. However, other researches insist that if a distributor has only a given level of trust in his/her suppliers, irrelevant of the perceived risk level, he/she participates in the e-partnership. Thus, from the perspective of a distributor, this study built a trust model in which these two viewpoints were reflected. And then this study examined whether or not perceived risk mediates an influence of trust to e-partnership. The proposed trust model was tested with 265 questionnaires about a distributor-supplier e-partnership in food wholesale markets. The analysis results Indicated that perceived risk partially had a mediating effect between trust and e-partnership Intention. That is, of the two risk types, only perceived performance risk mediated an influence from competence trust to e-partnership intention. Relational risk did not play a mediating role between goodwill trust and e-partnership intention. This result Implies two managerial meanings. First, a distributor Intends to engage In e-partnership with his/her supplier, irrelevant of relational risk's level if goodwill trust level surpasses his/her own threshold. Thus, suppliers should concentrate more effort in developing goodwill trust than in reducing relational risk. To develop goodwill trust, they should endeavor to establish mutual interests and individual trust with their distributor, and to utilize institutional trust bases. Second, a distributor requires a certain competence In his/her suppliers to sufficiently reduce performance risk caused bye-partnership. Thus, to develop competence trust in e-partnership, suppliers should improve on any lack of competence and build a good reputation.

• Journal of the Korean Wood Science and Technology
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• v.46 no.6
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• pp.735-747
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• 2018

Radon radiation exposures in home have been posed as a potential cancer hazard. This research aims to present the basic data of the indoor radon concentration level by examining the radon exhalation rates of wood species. Radon exhalation rates from five commonly used wood species in Korean wood building construction were measured with Continuous Radon Monitor (CRM), Model 1028 (Sun Nuclear Co., USA) using the Closed Chamber Method (CCM). The mass exhalation rate was observed to vary from $0.00089Bq{\cdot}kg^{-1}{\cdot}h^{-1}$ to $0.00181Bq{\cdot}kg^{-1}{\cdot}h^{-1}$, whereas the surface exhalation rate was observed to be $0.00677-0.01517Bq{\cdot}m^{-2}{\cdot}h^{-1}$. The radon exhalation rate of Quercus accutissima Carruth (white oak) which has the highest density showed the highest figure among the five wood species, on the other hand, the rest of four species showed similar results which were similar to the radon exhalation rates of wood in the U.S.A. and Canada. The average of the concentration measured by the CCM represented well up to the second half-life period (7.7 days). Because result of these small quantities seems to indicate that radon exhalation from the tested wood species has almost negligible impact, the main culprit of the high indoor radon concentration is clearly derived from the background of surrounding wood house. Therefore, as a safety precaution, infrastructures made of wood materials should be designed with the consideration of influx of radon and built accordingly. Furthermore, it is highly desirable that wood will be needed to use for furniture and interior finishing material in indoor environment.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.3
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• pp.146-155
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• 1992

It has been conventional to treat the land boundary as a fixed one in numerical modeling of tidal flows, particularly in the finite element scheme. However conventional models using the fixed land boundary result in unrealistic tidal flows in inter-tidal zones which exist over wide coastal area in Korea. In this study, a 2-dimensional hydrodynamic model, using finite element method for moving boundary problems was developed. The performance of the model was tested in a rectangular channel with an open boundary at one end and a moving boundary at the other end. The model was applied to calculate the tidal currents in Maro Hae, located in the southwestern part of Korea where wide tidal flats develop. The behavior of tidal currents in the Udolmok and near the tidal flats in the study area was satisfactory when compared with the observed data. Variation of tidal currents due to the construction of Kochunam sea-dyke which barrages large area of tidal flat was presented. The results of this study confirm the efficiency of moving boundary treatment in coastal numerical models.

• Korean Journal of Community Nutrition
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• v.15 no.2
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• pp.169-179
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• 2010

Good snack consumption behaviors are important among elementary students because snack provides additional energy and nutrients and because good dietary behaviors should be formed during early stages of life. This study investigated, among elementary school students, 1) snack consumption behaviors, 2) snack-related nutrition knowledge level, and 3) relationships between snack behaviors and snack-related nutrition knowledge. A convenience sample (N = 372), drawn from 5th and 6th graders of an elementary schools in Siheung-si, Gyeonggi-do, completed a pre-tested questionnaire. More than 85% of the participants snacked more than once per week. Most (77%) had their snacks at home. Fruit and fruit juice were the most frequently consumed and the most liked snack items. Taste was the most important in choosing a snack item closely followed by health/nutrition. Snack-related knowledge level was relatively high and the participants obtained their nutrition knowledge through mass media (30.4%) and family/friends (29.0%). Snack-related nutrition knowledge level and snack consumption behaviors showed positive relationships in various areas such as choosing more nutritious snack items and checking nutrition labels. Although this study was limited by its cross-sectional study design, these positive relationships suggest that better nutrition knowledge could result in better behaviors. Results of this study indicated that factual nutritional knowledge has been well transmitted to students. Therefore, future nutrition education on snacking could focus more on providing problem-solving and operational knowledge.

• The Journal of the Korea Contents Association
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• v.14 no.3
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• pp.203-214
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• 2014

In this study, a meta-analysis was conducted to investigate the effect of community-based rehabilitation on patients with brain injury by ICF factor in previous studies and examine the application of recent community-based rehabilitation program. Total 15 articles that satisfied the selection criteria were divided by ICF factors to obtain the effect size. Homogeneity and publication bias were tested for those selected papers. As a result, the overall effect size of community-based rehabilitation was 0.22; the effect size by physical function and structure among the ICF factors came to be 0.21; and the effect size of activity and participation was 0.20, indicating a small effect size. The studies involved in a meta-analysis were considered as the absence of heterogeneity and publication bias, which indicates that the results of this study are subjectively reliable. These results well explained the level of change on ICF factors, especially physical function and structure, activity and participation, in other words, the intervention effect of community-based rehabilitation on patients with brain injury.

• The Journal of the Korea Contents Association
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• v.13 no.12
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• pp.786-796
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• 2013

The purpose of this study was to search for approaches towards the improved the job performance of the community child center workers, by analyzing relations between their job performance and its concerned variables. For that purpose, the investigator searched the characteristics of variables and relations among the variables and empirically analyzed the factors affecting the job performance. As a result, there were significant differences in job performance according to the empowerment, network and job characteristics. The results of hierarchical regression analysis reveal that changes to each of the models were checked by introducing a new group of variables in each stage. Then the influences of the variables including the empowerment, network and job characteristics on job performance were tested through the influence and significance of the variables and the changing explanatory power of the entire models.

• The Korean Journal of Pain
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• v.14 no.1
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• pp.110-113
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• 2001

In controlling chronic intractable pains, the current therapeutic methods used are exercise, over the counter medication, cognitive-behavioral therapy, opioid medication, neural blockade, operation, etc., spinal cord stimulation being the last resort. Spinal cord stimulation was initiated when Shearly and others clinically tested the Gate control theory of Melzack and Wall. This had triggered the advancement of theoretic research on the mechanism and hardware necessary and has resulted in an accumulation of clinical experiences. This is known to be effective for treating sympathetic pain, arachnoiditis, failed back pain syndrome, radiculopathy, peripheral vascular disease, phantom limb syndrome, post-herpetic neuralgia, peripheral neuropathy, and angina pectoris. This report describes our experience in experimental spinal cord stimulation in patients with simultaneous post-herpetic neuralgia and herniated intervertebral disc. There wasn't any improvement in the post-herpetic neuralgia but the symptoms of a herniated intervertebral disc was much ameliorated. This was quite an unexpected result. The patient's back pain returned when the stimulation stopped.

• Journal of Pharmaceutical Investigation
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• v.34 no.1
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• pp.43-48
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• 2004

The purpose of the present study was to evaluate the bioequivalence of two nizatidine capsules, Axid (Lilly Korea Pharm. Co., Ltd.) and Nex (Bi-nex Pharm. Co., Ltd.), according to the guidelines of Korea Food and Drug Administration (KFDA). The nizatidine release from the two nizatidine capsules in vitro was tested using KP Apparatus method with various dissolution media (pH 1.2, 4.0, 6.8 buffer solutions and water). The dissolution prefers of two nizatidine capsules were very similar at all dissolution media. Twenty four normal male volunteers were divided into two groups with a randomized 22 crossover study. After two capsules (300 mg nizatidine) were orally administrated, blood was taken and the concentrations of nizatidine in serum were determined using HPLC with UV detector. The pharmacokinetic parameters such as $AUC_t$, $C_{max}$ and $T_{max}$ were determined. The result showed that the differences in $AUC_t$, $C_{max}$ and $T_{max}$ between two nizatidine capsules based on the Axid were -6.16%, -8.26% and -1.82%, respectively. There were no sequence effects between two capsules in these parameter. The 90% confidence intervals using logarithmically transformed data were within the acceptance range of log(0.8) to log(125)(e.g., $log(0.91){\sim}log(0.97)$ and $log(0.85) {\sim}log(0.99)$ for $AUC_t$ and $C_{max}$ respectively), indicting that Nex capsule is bioequivalent to Axid capsule.