• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.46-52
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• 2010

In this paper, emission analysis during cold start period of CVS-75 mode in LPG vehicle was performed to find out proper operating conditions of SAI(Secondary Air Injection) system. In order to meet SULEV target, the simulated emission system had a SAI system as well as a MCC(Manifold Catalytic Converter) and a UCC(Under body Catalytic Converter). Using commercial 1-D code AMESIM, in which 7 step global surface chemical reactions of Langmuir-Hinshelwood type were adopted, transient emission analysis in the exhaust system during cold start period of CVS-75 mode were carried out to figure out the effects of flow rate, duration of supply air on HC, CO, NO emission.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.7
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• pp.423-426
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• 2017

The designing approaches with consideration offabrication process technologies for high-frequency, high-powered, silicon-based static induction thyristors (SITH) are presented. The effects of doping concentration and thickness on the I-V characteristics and power performance of the devices are discussed. The dependence of SITH switching performances on material, geometric structure, and technological parameters isexamined by using two-dimensional simulations. Thick-epitaxy technology is found to be one of the most critical steps in realizing the proposed structure and switching times, $t_{off}$, of SITH, which may be reduced to below ${\sim}0.26{\mu}s$ for the proposed 1,700 V SITH devicesafter optimization.

• Journal of Information Technology Applications and Management
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• v.21 no.2
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• pp.149-165
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• 2014

This paper has studied whether cultural factors have an effect on privacy concern of Internet users in Korea and China. The result has shown that power distance, individualism, uncertainty avoidance, and long-term orientation are positively related to privacy concern, while masculinity is negatively related to privacy concern. This study has also found some similarities and differences between the two countries. First, privacy concern of Korean Internet users is significantly higher than that of Chinese users. Second, individualism and uncertainty avoidance significantly affect privacy concern in both Korea and China, although individualism in Korea has stronger effect than that in China. Third, long term orientation has a significant effect in only Korea while power distance is significant only in China. These results suggest that an online company doing businesses in multiple countries should have country-specific privacy policies to deal with the privacy concern of Internet users in different countries.

• Structural Engineering and Mechanics
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• v.14 no.2
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• pp.209-221
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• 2002

In this paper a fracture criterion is proposed for cracked cylindrical samples of high-strength prestressing steels of different yield strength. The surface crack is assumed to be semi-elliptical, a geometry very adequate to model sharp defects produced by any subcritical mechanism of cracking: mechanical fatigue, stress-corrosion cracking, hydrogen embrittlement or corrosion fatigue. Two fracture criteria with different meanings are considered: a global (energetic) criterion based on the energy release rate G, and a local (stress) criterion based on the stress intensity factor $K_I$. The advantages and disadvantages of both criteria for engineering design are discussed in this paper on the basis of many experimental results of fracture tests on cracked wires of high-strength prestressing steels of different yield strength and with different degrees of strength anisotropy.

• Biomolecules & Therapeutics
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• v.20 no.3
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• pp.340-345
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• 2012

Sarsasapogenin (SAR) is a steroidal sapogenin that is used as starting material for the industrial synthesis of steroids. It has various pharmacological benefits, such as antitumor and antidepressant activities. Since its effect on melanin biosynthesis has not been reported, we used murine melanocyte melan-a cells to investigate whether SAR influences melanogenesis. In this study, SAR significantly increased the melanin content of the melan-a cells from 1 to 10 ${\mu}M$. Based on an enzymatic activity assay using melan-a cell lysate, SAR had no effect on tyrosinase and DOPAchrome tautomerase activities. It also did not affect the protein expression of tyrosinase-related protein 1 and DOPAchrome tautomerase. However, protein levels of tyrosinase and microphthalmia-associated transcription factor were strongly stimulated by treatment with SAR. Therefore, our reports suggest that SAR treatment may induce melanogenesis through the stimulation of tyrosinase and microphthalmia-associated transcription factor expression in melan-a cells.

• Honam Mathematical Journal
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• v.45 no.1
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• pp.54-70
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• 2023

In this article, we state and prove several new retarded nonlinear integral and integro-differential inequalities of Gronwall-Bellman-Pachpatte type. These inequalities generalize some former famous inequalities and can be used in examining the existence, uniqueness, boundedness, stability, asymptotic behaviour, quantitative and qualitative properties of solutions of nonlinear differential and integral equations. Applications are provided to demonstrate the strength of our inequalities in estimating the boundedness and global existence of the solution to initial value problem for nonlinear integro-differential equation and Volterra type retarded nonlinear equation. This research work will ensure to open the new opportunities for studying of nonlinear dynamic inequalities on time scale structure of varying nature.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.8
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• pp.4083-4088
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• 2016

Background: Physical inactivity has been identified as the fourth leading risk factor for global mortality and is associated with increased breast cancer diagnosis and recurrence. Purpose: To examine the association between adult lifetime physical activity and breast cancer risk in a case-control analysis. Materials and Methods: This study involved 122 cases of breast cancer and 121 controls in the state of Kelantan in Malaysia. A comprehensive measure of lifetime physical activity was used to assess occupational, household, and recreational/sports activity. For every type of activity, a metabolic equivalent (MET) score was assigned using the compendium of physical activities. MET-hours/week per year for all types of activities at different levels of intensities for different age groups were calculated. Logistic regression analysis was used to estimate odds ratios between various measures of physical activity and breast cancer risk. Conclusions: The mean MET-hours/week per year for all activities were 120.0 and 132.9 of MET-hours/week per year for cases and controls respectively. Household activities accounted for about 70% of the total lifetime physical activities. Only about 2.5% of the total lifetime physical activities were in the form of recreational/sports. This study found no association between lifetime occupational and recreational/sports physical activities with breast cancer risk among Kelantanese women. However, higher intensity lifetime household activities seemed to significantly reduce risk of breast cancer.

• Journal of Communications and Networks
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• v.12 no.1
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• pp.52-66
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• 2010

Since large objects consume substantial resources, web proxy caching incurs a fundamental trade-off between performance (i.e., hit-ratio and latency) and overhead (i.e., resource usage), in terms of caching and relaying large objects to users. This paper investigates how and to what extent the current dedicated-server based web proxy caching scheme is affected by large file transfers in a high bandwidth campus network environment. We use a series of trace-based performance analyses and profiling of various resource components in our experimental squid proxy cache server. Large file transfers often overwhelm our cache server. This causes a bottleneck in a web network, by saturating the network bandwidth of the cache server. Due to the requests for large objects, response times required for delivery of concurrently requested small objects increase, by a factor as high as a few million, in the worst cases. We argue that this cache bandwidth bottleneck problem is due to the fundamental limitations of the current centralized web proxy caching model that scales poorly when there are a limited amount of dedicated resources. This is a serious threat to the viability of the current web proxy caching model, particularly in a high bandwidth access network, since it leads to sporadic disconnections of the downstream access network from the global web network. We propose a peer-to-peer cooperative web caching scheme to address the cache bandwidth bottleneck problem. We show that it performs the task of caching and delivery of large objects in an efficient and cost-effective manner, without generating significant overheads for participating peers.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.34-50
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• 2022

Since the Paris climate agreement, reducing greenhouse gases has been the most important global issue. In particular, it is necessary to reduce fossil fuels in the mobility sector, which accounts for a significant portion of total greenhouse gas emissions. In this paper, we investigated the economic feasibility of green mobility energy supply chains, which supply hydrogen as fuel to hydrogen vehicles based on electricity from renewable energy sources. The design and operation costs were analyzed by evaluating nine scenarios representing various combinatorial possibilities such as renewable energy generation, hydrogen production through water electrolytes, hydrogen storage and hydrogen refueling stations. Simulation calculations were made using Homer Pro, widely used commercial software in the field. The experience gained in this study could be further utilized to construct actual hydrogen energy systems.

• Journal of Korean Academy of Rural Health Nursing
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• v.18 no.1
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• pp.1-10
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• 2023

Purpose: This study was to evaluate the effects of a social prescribing program on cognitive function and depression of the elderly in the rural community. Methods: A non-equivalent control group pretest-posttest design was used for this study. The experimental group (n=76) completed a 8-week intervention of social prescribing, while the control group (n=39) only participated in pre- and post- need assessment from April 2021 to October 2022. A Wilcoxon signed rank test was conducted to evaluate the effectiveness of a social prescribing program on the level of cognitive function and depression of the participants. Results: The level of cognitive function was improved significantly in the experimental group (p<.05) while there was no significant change in the control group. Depression has been significantly decreased in the experimental group (p<.01), but there was no statistically significant change in the control group. Conclusion: The results of this study suggest that the social prescribing program is effective for improving cognitive function and reducing depression of the elderly living in the rural area. Therefore, a social prescribing program can be utilized as a preventive program for dementia and depression of the elderly.