• Transactions of the Korean Society of Automotive Engineers
• /
• v.2 no.5
• /
• pp.30-40
• /
• 1994

The direct-injection stratified-charge engine has the advantages of higher thermal efficiency and less CO and $NO_x$ emission levels than conventional spark ignition engines. However, its actual utilization is prevented by high unburned hydrocarbon emission levels during light-load operations. In this paper, fundamental studies were carried out using a pancake type constant volume bomb. The effects of intensification of local premixing by tangential and radial fuel injection were examined experimentally. Unburned hydrocarbon emission levels with radial fuel injection were shown to be lower than those of tangential fuel injection cases. The stratification and mixing process of fuel jet and combustion process were observed by schlieren photography.

• Journal of Power Electronics
• /
• v.16 no.3
• /
• pp.994-1003
• /
• 2016

Two major obstacles in the utilization of electrical vehicles are their price and range. The collaboration of direct torque control (DTC) with induction motor (IM) is preferred for its low cost, easy implementation, and parameter independency. However, in terms of edges, the method has drawbacks, such as variable switching frequency and undesired current harmonic distortion. These drawbacks result in acoustic noise, reduced efficiency, and electromagnetic interference. A feed-forward approach for stator-flux-oriented DTC with space vector pulse-width modulation is presented in in this paper. The outcome of the proposed method is low current harmonic distortion with fixed switching frequency while preserving the torque performance and simple application feature of basic DTC. The method is applicable to existing and forthcoming IM drive systems via software adaptation. The validity of the proposed method is confirmed by simulation and experimental results.

• Macromolecular Research
• /
• v.16 no.6
• /
• pp.524-531
• /
• 2008

The mitigation or elimination of methanol crossover for perfluorosulfonic acid fuel cell membranes has been investigated extensively for direct methanol fuel cell applications with the aim of increasing the electrochemical performance and enhancing the utilization rate of methanol. Self-assembly modifications by applying an oppositely charged polyelectrolyte to Nafion membranes were attempted in order to block or reduce methanol crossover while maintaining the other advantageous properties of Nafion membranes. It was reported that anionic polyallylamine hydrochloride (PAH) was the most efficient polyelectrolyte in reducing methanol crossover, and considerable cell performance was obtained even at a methanol feed concentration of 10 M.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.3
• /
• pp.890-910
• /
• 2014

This paper investigates the spectrum hole utilization of cooperative schemes for the two-way relaying model in order to improve the utilization efficiency of limited spectrum holes in cognitive radio networks with imperfect spectrum sensing. We propose two specific bidirectional secondary data transmission (BSDT) schemes with two-step and three-step two-way relaying models, i.e., two-BSDT and three-BSDT schemes, where the spectrum sensing and the secondary data transmission are jointly designed. In the proposed cooperative schemes, the best two-way relay channel between two secondary users is selected from a group of secondary users serving as cognitive relays and assists the bi-directional communication between the two secondary users without a direct link. The closed-form asymptotic expressions for outage probabilities of the two schemes are derived with a primary user protection constraint over Rayleigh fading channels. Based on the derived outage probabilities, the spectrum hole utilization is calculated to evaluate the percentage of spectrum holes used by the two secondary users for their successful information exchange without channel outage. Numerical results show that the spectrum hole utilization depends on the spectrum sensing overhead and the channel gain from a primary user to secondary users. Additionally, we compare the spectrum hole utilization of the two schemes as the varying of secondary signal to noise ratio, the number of cognitive relays, and symmetric and asymmetric channels.

• Journal of Preventive Medicine and Public Health
• /
• v.39 no.5
• /
• pp.397-403
• /
• 2006

Objectives: We estimated the asthma-related health care utilization and costs in Korea from the insurer's and societal perspective. Methods: We extracted the insurance claims records from the Korea National Health Insurance claims database for determining the health care services provided to patients with asthma in 2003. Patients were defined as having asthma if they had ${\geq}$2 medical claims with diagnosis of asthma and they had been prescribed anti-asthma medicines, Annual claims records were aggeregated for each patient to produce patient-specific information on the total utilization and costs. The total asthma-related cost was the sum of the direct healthcare costs, the transportation costs for visits to health care providers and the patient's or caregivers' costs for the time spent on hospital or outpatient visits. Results: A total of 699,603people were identified as asthma patients, yielding an asthma prevalence of 1.47%. Each asthma patient had 7.56 outpatient visits, 0.01 ED visits and 0.02 admissions per year to treat asthma. The per-capita insurance-covered costs increased with age, from 128,276 Won for children aged 1 to 14 years to 270,729 Won for those aged 75 or older. The total cost in the nation varied from 121,865 million to 174,949 million Won depending on the perspectives. From a societal perspective, direct health care costs accounted for 84.9%, transportation costs for 15.1 % and time costs for 9.2% of the total costs. Conclusions: Hospitalizations and ED visits represented only a small portion of the asthma-related costs. Most of the societal burden was attributed to direct medical expenditures, with outpatient visits and medications emerging as the single largest cost components.

• Journal of Preventive Medicine and Public Health
• /
• v.42 no.1
• /
• pp.5-11
• /
• 2009

Objectives : This study was conducted to estimate the socioeconomic cost of injuries in South Korea. Methods : We matched claims data from national health insurance, automobile insurance and industrial accident compensation insurance(IACI), and mortality data obtained from the national statistical office from 2001 to 2003 by patients unique identifier. Socioeconomic cost included both direct cost and indirect cost: the direct cost was injury-related medical expenditure and the indirect cost included loss of productivity due to healthcare utilization and premature death. Results : The socioeconomic cost of injuries in Korea was approximately 1.9% of the GDP from 2001 to 2003. That is, 12.1 trillion KRW(Korean Won) in 2001, 12.3 trillion KRW in 2002, and 13.7 trillion KRW in 2003. In 2003, direct medical costs were 24.6%(3.4 trillion KRW), the costs for loss of productivity by healthcare utilization were 13.0%(1.8 trillion KRW), and the costs for loss of productivity by premature death were 62.4%(8.6 trillion KRW). Conclusions : In this study, the socioeconomic cost of injuries in Korea between 2001 and 2003 was estimated by using not only health insurance claims data, but also automobile insurance, IACI claims and mortality data. We conclude that social efforts are required to reduce the socioeconomic cost of injuries in Korea, which represented approximately 1.9% of the GDP for the time period specified.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.4
• /
• pp.1511-1519
• /
• 2010

The purpose of this study was to analyze regional medical utilization variation of hospital inpatients and to suggest policy for the allocation of medical service in Korea. We analyzed the relationship among medical service, city size, income level and regional medical utilization variation of hospital inpatients. The patient survey report of 2005 year in Ministry of Health and Welfare was used for this study. To adjust on the factor age and sex, we used direct standardization method. Findings of the research were summarized as follows ; First, standardization discharge rate on patient was different in the district. city type, and number of beds. Second, standardization length of stay of patient was different in region, city type, and number of beds.

• Journal of Distribution Science
• /
• v.19 no.11
• /
• pp.5-15
• /
• 2021

Purpose: The current study aims at knowing and testing factors supporting business and how to distribute it for resilience business in new normal era. Factors Supporting business resilience will be seen in terms of entrepreneurial competence, technology utilization and government support for business resilience through entrepreneurial spirit as an intervening variable. Research design, data, and methodology: A constructed questionnaire in direct survey and interview was conducted with 97 respondents in South Sulawesi. Partial Least Square (PLS) analysis, was utilized to analyze and verify all the data. Results: This study indicated entrepreneurial competence and utilization of technology have a positive and significant effect on entrepreneurial spirit, while government support has no significant effect on entrepreneurial spirit. This study also indicated that entrepreneurial spirit has a significant effect on business resilience. Conclusion: To increase business resilience, it is very important to have entrepreneurial skills and mastery on utilization of technology. To anticipate future crises, entrepreneurial competencies must be evenly distributed both for business owners and for all members of the organization. To institutionalize crisis management in business, it is important for SMEs in Indonesia to develop an institutionalized Business Crisis Management.

• Journal of Distribution Science
• /
• v.20 no.2
• /
• pp.101-108
• /
• 2022

Purpose: In this logistics disturbance period, this study conducts research of distribution and logistics firms in Korea. The purpose of this exploratory research is to analyze global competitive capability influence on business performance. And give managerial implications and contribute to academics. Research design, data, and methodology: This research empirically analyzes the relationship between global competitive capability and business performance. As for business performance this research considered non-financial performance and measured with business performance fulfillment. As for antecedent variables, this research measured three global competitive capability constructs; preparation, utilization, intensive capability. And each construct includes two capability concepts. This study used 2,316 executing direct export distribution and logistics industry firmsfrom KOTRA's GCL data. This research used frequency analysis, reliability analysis, correlation analysis, and step-wise regression analysis by SPSS26. Results: The result shows that all the variables except export infra showed statistically significant. As results show, mid/long strategy & global mind of preparation capability, both communication and marketing of utilization capability and market strategy and product/goods/service of intensive capability give a positive influence on business performance fulfillment. Conclusions: Based on the results, this research provide implication for practical management, contribution to academic, and suggestion for feature research.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.4
• /
• pp.363-371
• /
• 2022

In this study, the operation characteristics of the internal reforming type molten carbonate fuel cell (MCFC) were studied using computational fluid dynamics (CFD) analysis according to the steam to carbon ratio (S/C ratio), operating temperature, and gas utilization. From the simulation results, the distribution of gas composition due to the electrochemical reaction and the reforming reaction was predicted. The internal reforming type showed a lower temperature difference than the external reforming type MCFC. As the operating temperature decreased, less hydrogen was produced and the performance of the fuel cell also decreased. As the gas utilization rate decreased, more gas was injected into the same reaction area, and thus the performance of the fuel cell increased.