• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.2
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• pp.225-236
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• 2016

Objectives: Nanomaterials have been used in various fields. As use of nanoproducts is increasing, workers dealing with nanomaterials are also gradually increasing. Exposure assessments for nanomaterials have been carried out for protection of worker's health in workplace. Exposure studies were mainly focused on manufacturing processes, but these studies on after-treatment processes such as refinement, weighing, and packing were insufficient. So, we investigated exposure characteristics of particles during after-treatment processes of $Al_2O_3$ fibers and Ni powders. Methods: Mass-production of Ni powder process was carried out in enclosed capture-type canopy hood. In a developing stage, $Al_2O_3$ was handled with a local ventilation unit. Exposure characteristics of particles were investigated for $Al_2O_3$ fiber and Ni powder processes during the periods of 10:00 to 16:00, 20 May 2014 and 13:00 to 16:00, 21 May 2014, respectively. Three real-time aerosol instruments were utilized in exposure assessment. A scanning mobility particle sizer(SMPS, nanoscan, model 3910, TSI) and an optical particle counter(OPC, portable aerosol spectrometer, model 1.109, Grimm) were used to determine the particle size distribution in the size range of 10-420 nm and $0.25-32{\mu}m$, respectively. In addition, a nanoparticle aerosol monitor(NAM, model 9000, TSI) was used to measure lung-deposited nanoparticle surface area. Membrane filters(isopore membrane filter, pore size of 100 nm) were also used for air sampling for the FE-SEM(model S-5000H, Hitachi) analysis using a personal sampling pump(model GilAir Plus by 2.5 L/min, Gilian). Conclusions: For Ni powder after-treatment process, only 27% increase in particle concentration was found during the process. However, for $Al_2O_3$ fiber after-treatment process, significant exposure(1.56-3.34 times) was observed during the process.

• Journal of muscle and joint health
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• v.3 no.1
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• pp.63-89
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• 1996

This study has been done for the purpose of determining whether the positive association between social support and depression is attributable to an overall beneficial effect of support(direct effect) or to a process of support protecting persons from adverse effects of stressors such as life events, pain or physical disability (buffering effect). The sample consisted of 214 patients who were identified as the rheumatoid arthritis. The instruments used in this study were Depression Scale(CES-D), Perceived Social Support Scale, Life Events Questionnaire, AIMS Pain Scale, and Physical Disability Scale. The data were analysed by the use of t-test, ANOVA, Pearson Correlation Coefficient and Stepwise Multiple Regression. The results of this study are summerized as follows : 1. The 1st hypothesis, "The higher the life events degree, the higher the depression degree" was supported(r=.49, P=.0001). 2. The 2nd hypothesis, "The higher the pain degree, the higher the depression degree" was supported(r=.44, P=.0001). 3. The 3rd hypothesis, "The higher the physical disability degree, the higher the depression degree" was supported (r=.46, P=.0001). 4. The 4th hypothesis, "The higher the social support degree, the lower the depression degree" was supported(F=84.52, P=.0001). 5. The 5th hypothesis, "There will be different in the relationship between the degrees of life events and depression according to social support degree" was rejected (F=.29, P=.5928). 6. The 6th hypothesis, "There will be different in the relationship between the degrees of pain and depression according to social support degree" was supported (F=3.19, P=.0755). 7. The 7th hypothesis, "There will be different in the relationship between the degrees of physical disability and depression according to social support degree" was supported(F=5.69, P=.018). 8. The predictive variables for depression were the degrees for social support, life events, pain, and physical disability. 9. The depression degree showed a inverse correlation with social support degree (r=-.56, p=.0001). The social support degree showed a inverse correlation with the degrees of life events(r=-.22, p=.0007), pain(r=-.18, p=.0069) and physical disability(r=-.15, p=.0293). 10. The depression degree showed significant differences in the variables of sex (t=2.26, p=.025), educational level(r=.189, P=.006) and the number of treatment method (r=.201, P=.003). In conclusion, it was found that social support had the direct effect on depression and the buffering effect in each relationship between degrees of pain or physical disability and depression in patients with rheumatoid arthritis. So the researcher thinks that it is effective that nurses should provide these patients with social support to reduce depression in cases of having severe pain or physical disability.

• Journal of Korea Technology Innovation Society
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• v.9 no.1
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• pp.26-51
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• 2006

Recently technology commercialization has been the focus of technology Promotion Policy in Korea. This paper tries to develop a composite indicator for measuring trends and prospects of national technology commercialization through integrating large amount of information into easily understood formats. The indicator is composed of five sector indicators including activity, cooperation or networking, performance, environment, and psychology indicators, each of which aggregates five individual variables. The statistical method of standardizing and weighting variables in the aggregation process are also mentioned. This indicator is expected to be a useful monitoring and policy tool for the Korean technology market.

• Journal of the Korea Society of Computer and Information
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• v.23 no.7
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• pp.19-26
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• 2018

This paper presents a structuring process of unstructured social network service (SNS) messages on rail services. We crawl messages about rail services posted on SNS and extract keywords indicating date and time, rail operating company, station name, direction, and rail service types from each message. Among them, the rail service types are classified by machine learning according to predefined rail service types, and the rest are extracted by regular expressions. Words are converted into vector representations using Word2Vec and a conventional Convolutional Neural Network (CNN) is used for training and classification. For performance measurement, our experimental results show a comparison with a TF-IDF and Support Vector Machine (SVM) approach. This structured information in the database and can be easily used for services for railway users.

• International Commerce and Information Review
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• v.11 no.1
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• pp.485-515
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• 2009

In this study aims to research and analyze what are decision factors between a wholly-owned subsidiary and a international company cooperation in the internationalization process. From 57 primary studies found 26 observed variables for aggregation of effect size in the using "Fixed Effect Model" on this mata-analysis. The article also links the theories that are used in the literature, not considered in the most of primary studies, to the empirical results and recommends global management strategy which is needed for business practical affairs. According to the result, the meta-analysis suggests that the number of employees of a MNC, the geological and cultural differneces between the host country and home country, the country-specific international experience of the MNC and export intensity, the international product diversification, the market growth and the market size of the foreign operations, and resource intensity of the foreign operations, the legal restrictions in the host country and the country risk of the home country do exert a significant effect on the decision between cooperative arrangement and a wholly-owned subsidiary. Conversely, for a large number of variables, no significant relationship seems to exist based on the combined results. This is the case, for example, for factor specificity, the r&d-intensity, the subsidiary size, the assets of the MNC and the sales volume of the MNC.

• Journal of Environmental Science International
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• v.20 no.2
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• pp.215-222
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• 2011

The adsorption behavior of nitrate nitrogen was investigated from aqueous solution using char prepared from oak chip. The removal rate of nitrate nitrogen was found to be dependent on temperature and it is increased as the temperature increase. Adsorption equilibrium data of nitrate nitrogen on oak char. reasonably fitted Langmuir and Freundlich isotherm models. The adsorption energy obtained from D-R model was 12.5 kJ/mole at $20^{\circ}C$ indicating an ion exchange process as primary adsorption mechanism. Thermodynamic parameters such as ${\Delta}G^o$, ${\Delta}H^o$, and ${\Delta}S^o$ were -23.76 kJ/mole, 26.1 kJ/mole and 89.7 J/K mole at $20^{\circ}C$, respectively, indicated that the nature of nitrate nitrogen adsorption is spontaneous and endothermic.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.20-26
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• 2016

For power electronic devices, the thermal energy density per unit volume has seen a rapid increase in recent years, owing to the miniaturization and dense integration of electronic components, as well as the continuous development in performance and function. This research examined the validity and reliability of a thermal safety model for managing the heating conditions of TRIAC electronic components. Among the electronic components of a PCB, these can be considered as a heat source. Using the model, the heating conditions of TRIAC components were maintained at their design target levels in the process of developing an LMT motor drive board. In addition, the heating characteristics of the entire PCB were analyzed to verify its thermal safety. Finally, the reliability and validity of the thermal safety model for maintaining the heating conditions of the TRIAC electronic elements at adequate levels was verified using a numerical analysis method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.1
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• pp.22-26
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• 2014

$(Ba_{0.85}Ca_{0.15})(Ti_{0.9}Zr_{0.1})O_3$ + 0.04 wt% $CeO_2$ lead-free ceramics were prepared by conventional oxide-mixed method and the effect of sintering temperature on microstructure, dielectric and piezoelectric properties were investigated. Improved piezoelectric properties have been observed at $1,400^{\circ}C$ sintering temperature which show the optimal electrical properties, $k_p{\sim}0.412$, $d_{33}{\sim}316pC/N$, $Q_m{\sim}144$, ${\varepsilon}_r{\sim}3,345$ and $T_c{\sim}85^{\circ}C$. These results show that the sintering temperature plays an important role in piezoelectric properties.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.81-88
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• 2009

Bellows is used to control temperature of a Joule-Thomson micro cryocooler. It is made of Nickelcobalt alloy that retains mechanical properties from cryogenic temperature to temperature of 570K. The geometry of bellows is an axisymmetric shell and Nitrogen with high pressure was charged at temperature of 293K. During cool-down process, the pressure and volume of Nitrogen are changed and must be satisfied with state equation. At cryogenic temperature, Nitrogen can exist as a part liquid and part vapor. Pressure-density-temperature behavior under this vaporliquid phase equilibrium is closely given by the Modified-Benedict-Webb-Rubin(MBWR) state equation. To evaluate deformation of bellows for temperature change, the numerical calculation of the volume within bellows and finite element analysis of bellows under internal pressure were iteratively performed until MBWR state equation is satisfied. The numerical results show that deformation of the bellows can be analyzed by the present method in a wide range of temperature including cryogenic temperature.

• Journal of Drive and Control
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• v.19 no.1
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• pp.26-33
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• 2022

This study dealt with a self-propelled spinach harvester, which is capable of carrying out sequential harvesting work. This study aimed to find the cause of the harvester's occasional performance deterioration, which occurs in the process of simplifying the hydraulic circuit, using a multi-domain analysis model. The study was carried out in the following manner. First, a hydraulic system analysis model, which combines linear motion, rotary motion, hydrodynamic behavior, and an electrical signal, was developed through SimulationX software, specialized in multi-domain analysis. Second, a scenario for single behavior and coupled behavior was set out on an actuator basis. Third, the flow rate of the hydraulic system, which is not required for the movement of the actuator, was quantitatively analyzed. The results showed that a change in oil temperature was the cause of the harvester's occasional performance deterioration. And the higher the oil temperature, the more serious the performance deterioration, especially as the number of actuators operated simultaneously was small.