• Journal of Korean Society on Water Environment
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• v.36 no.1
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• pp.55-68
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• 2020

Because of the intensified environmental problems such as climate change and resource depletion, sewage treatment technology focused on energy management has recently attracted attention. The conversion of primary sludge from the primary sedimentation tank and excessive sludge from the secondary sedimentation tank into biogas is the key to energy-positive sewage treatment. In particular, the primary sedimentation tanks recover enriched biodegradable organic matter and anaerobic digestion process produces methane from the organic wastes for energy production. Such technologies for minimizing oxygen demand are leading the innovation regarding sewage treatment plants. However, sewage treatment facilities in Korea lack core technology and operational know-how. Actually, the energy potential of sewage is higher than sewage treatment energy consumption in the sewage treatment, but current processes are not adequately efficient in energy recovery. To improve this, it is possible to apply chemically enhanced primary treatment (CEPT), high-rate activated sludge (HRAS), and anaerobic membrane bioreactor (AnMBR) to the primary sedimentation tank. To maximize the methane production of sewage treatment plants, organic wastes such as food waste and livestock manure can be digested. Additionally, mechanical pretreatment, thermal hydrolysis, and chemical pretreatment would enhance the methane conversion of organic waste. Power generation systems based on internal combustion engines are susceptible to heat source losses, requiring breakthrough energy conversion systems such as fuel cells. To realize the energy positive sewage treatment plant, primary organic matter recovery from sewage, biogas pretreatment, and co-digestion should be optimized in the energy management system based on the knowledge-based operation.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.2
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• pp.161-168
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• 2015

Recently, due to various environmental problems such as global warming, increases of international oil prices, exhaustion of resource, a paradigm of world automobile market is rapidly changing from conventional vehicles using internal combustion engine to eco-friendly vehicles using electric power such as EV, HEV, PHEV and FCEV. Generally, in order to measure fuel consumption and pollutant emissions of cars, chassis dynamometer tests are performed on various driving cycles before actual driving test. There are many driving cycles for performance evaluation of conventional vehicles. However, there is a lack of researches on driving cycle for EV. In this study, the urban driving cycle for performance evaluation of electric vehicles was developed. This study is composed of two parts. In the part 1, the urban driving cycle 'GUDC-EV(Gwacheon-city Urban Driving Cycle for Electric Vehicles)' was developed by using driving data, which were obtained through actual driving experiment, and statistic analysis with chronological table. In this paper part 2, in order to verify the developed driving cycle GUDC-EV, virtual EV platforms were configured and simulations were performed with actual driving data using In addition, simulation results were compared with existing driving cycles such as FTP-72, NEDC and Japan 10-15.

• Journal of KIISE:Information Networking
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• v.33 no.5
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• pp.355-368
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• 2006

This paper introduces a new split-TCP approach for improving TCP performance over IEEE 802.11-based wireless LANs. TCP over wireless LANs differently from wired networks is not aggressive, which is a fundamental reason for poor performance. Therefore, we propose TAS (TCP-Aware Sub-layer) to migigate this problem. Our scheme extends the split-connection approach that divides a connection into two different connections at a split point such as an access point (AP). Using TAS, a wireless node emulates TCP ACK packets using MAC ACK frames, instead of receiving real TCP ACK packets. We compared TAS with both normal TCP and I-TCP (Indirect TCP) by NS2 simulation. Results show that TAS achieves higher throughput, more fair resource allocation and, in power-saving mode, shorter delays.

• Korea Journal of Hospital Management
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• v.11 no.1
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• pp.54-90
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• 2006

Medical clinics are core institutes that cover the primary medical care in Korea. Financial viability of the clinics is essential for them to conduct their roles and functions, and can be improved by increasing their operating profitability. On this ground, this study aimed at finding important factors that affect the operating profitability, and thereby at suggesting strategic alternatives that can contribute to the improvement of the profitability. Operating margin was set as a dependent variable, and such factors as general management conditions, number of visits, medical revenue, marketing activities, input resources, medical cost as independent variables. Nineteen hypotheses related to the variables were established and tested using data collected from 138 sample clinics for the year 2003. The results of the study are as follows : Firstly, such variables as percent ratio of the depreciation plus rent costs to total administration costs, type of clinical department manifested whether medical, surgical, or quasi-surgical, percent ratio of the interior facility investment to total fixed assets, and total number of outpatient visit are important factors that affect, positively or negatively, the medical profitability of the clinics. Secondly, following measures are needed to be established and implemented to improve the medical profitability. (1) Administration costs share 53.2% of the total medical costs, and depreciation plus rent costs 16.3% of the total administration costs. This implies that such measures as reinforcement of marketing activities, establishment of the cooperative utilizing system of the facility and equipment, or group practice are needed to increase cost-effectiveness. (2) Occupancy rate of the clinics with inpatient bed is as low as 45.5%, causing high fixed costs and low medical profitability. For its improvement, the resource input structure should be reorganized. Thirdly, in the future, a study that can increase sample representativeness of the study and explanation power of the variables should be performed for each type of clinical department to find more specific determinant factors and to contribute to the improvement of the medical profitability of the clinics.

• Convergence Security Journal
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• v.13 no.2
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• pp.195-202
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• 2013

Defense reform our military for the globalization of information. Scientific command structure, troop structure, unit structure, step-by-step into the power structure while promoting a history of quantitative-oriented structure, and structure of the quality of state-of-the-art technology-driven transition in the middle of the bottle numberplans about the current 3.3-fold increase in reducing the cadre(officers and NCOs). NCO groups in the executive, especially expanding the current level of 100% increase in the rate of long-serving, while ensuring a stable job and to superior resources to secure a stable policy through science. Military alliance is now underway. In the midst of this group, and urged the group at the University of the leading military and specialized resources to ensure each agreement required by subjects to reflect. Thus effectively improve the quality of education and the demands of the job analysis, DACUM curriculum development methods and procedures can be applied at the time of urgent need for foster an excellent resource for the discharge of curriculum development at the University of Selected as a core job, career, and job classification configuration inside of Duty according to KST derived from the group reflect on the training courses to meet the requirements in the curriculum through the development of curriculum, job definition, job model set to propose.

• Korean Journal of Construction Engineering and Management
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• v.2 no.1 s.5
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• pp.88-97
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• 2001

The Internet, the main issue of a new millennium, is being researched vitally for the progress of the construction industry, and the construction industry is considered to be led into a high-value added state-of-arts technology industry through CALS. Even if many construction companies gradually widen the use of the Internet for various purposes such as an electronic bidding system and an e-commerce system, the companies are still demanded to use the Internet more broadly and practically. Hence, the need for a tool for fast decision making and an effective construction management has risen. The PRIMA system has been developed specifically focused on meeting with those recent changes of the construction industry. This system is composed of three parts. Those are Just In Time(JIT) management, integrated application of man power${\cdot}$safety${\cdot}$work management and decision making process based on real-time information in the Internet. The usefulness of the PRIMA system has already been proved in a super-scale construction project. As the Internet environment get improved the use of the tool will be spread out gradually for many construction projects, regardless their size and location.

• Journal of Communications and Networks
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• v.17 no.5
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• pp.453-462
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• 2015

Body area networks (BANs) have emerged as an enabling technique for e-healthcare systems, which can be used to continuously and remotely monitor patients' health. In BANs, the data of a patient's vital body functions and movements can be collected by small wearable or implantable sensors and sent using shortrange wireless communication techniques. Due to the shared wireless medium between the sensors in BANs, it may be possible to have malicious attacks on e-healthcare systems. The security and privacy issues of BANs are becoming more and more important. To provide secure and correct association of a group of sensors with a patient and satisfy the requirements of data confidentiality and integrity in BANs, we propose a novel enhanced secure sensor association and key management protocol based on elliptic curve cryptography and hash chains. The authentication procedure and group key generation are very simple and efficient. Therefore, our protocol can be easily implemented in the power and resource constrained sensor nodes in BANs. From a comparison of results, furthermore, we can conclude that the proposed protocol dramatically reduces the computation and communication cost for the authentication and key derivation compared with previous protocols. We believe that our protocol is attractive in the application of BANs.

• Journal of Digital Convergence
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• v.14 no.8
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• pp.269-276
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• 2016

Public Safty-LTE(Long Term Evolution) is being deployed in the direction of reducing cost by using both of municipal network and commercial network. However, LTE Network is difficult to ensure the survivability during the information communication infrastructure failures. In addition, it is vulnerable in communication coverage of inside buildings and underground. In this study, we propose to implement effectively the network survivability technique through the convergence to the proven technology. As the advent of the IoT Age, smart sensors which are embedded in the environment and the things will be able to provide a useful infrastructure for ensuring the network survivability. Based on the feature of the smart sensor, we designed the sink node architecture to guarantee the network survivability in disaster situation through the convergence of the small cell technology and extension of wireless network coverage technology. The computing power inherent in the environment is a valuable resource that can be utilized in the disaster situation.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.5
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• pp.691-697
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• 2011

In this study, by using the Water footprint technique, the water consumption by washing machines, which holds higher ranks in using water than any other electric appliances, was analyzed during their life cycle. The life cycle is defined as raw materials production step, manufacturing step, and using step. In raw materials production step, Input materials were researched by using LCI DB(Life Cycle Inventory Database) and the water consumption was calculated with consideration of approximately 65% Input materials which were based weight. In manufacturing step, the water consumption was calculated by the amount of energy used in assembly factories and components subcontractors and emission factor of energy. In using step, referring to guidelines on carbon footprint labeling, the life cycle is applied as 5 years for a washing machine and 218 cycles for annual bounds of usage. The water and power consumption for operating was calculated by referring to posted materials on the manufacture's websites. The water consumption by nation unit was calculated with the result of water consumption by a unit of washing machine. As a result, it shows that water consumption per life cycle s 110,105 kg/unit. The water consumption of each step is 90,495 kg/unit for using, 18,603 kg for raw materials production and 1,006 kg/unit for manufacturing, which apparently shows that the using step consume the most water resource. The water consumption by nation unit is 371,269,584tons in total based on 2006, 83,385,649 tons in both steps of raw material production and manufacturing, and 287,883,935 tons in using step.

• Korean Journal of Medicinal Crop Science
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• v.18 no.1
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• pp.34-39
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• 2010

Machilus thunbergii was an important medicinal resource and distributed widely in China. In this study, the bioactivities of dichloromethane fraction (DF) and water fraction (AF) from Machilus thunbergii methanol extract were investigated. Total phenolic contents of DF and AF were 57.90 mg Gal/g and 189.92 mg Gal/g, and total flavonoid contents were 17.34 mg Que/g and 58.38 mg Que/g respectively. The $EC_{50}$ for DPPH radical scavenging activity of DF and AF were $24.37\;{\mu}g/m{\ell}$ and $2.10\;{\mu}g/m{\ell}$. Reducing power and hydroxyl radical scavenging activities of AF were higher than those of DF. The $\alpha$-glucosidase inhibitory activity of AF ($IC_{50}\;=\;1.13\;{\mu}g/m{\ell}$) was higher than that of DF ($IC_{50}\;=\;5.34\;{\mu}g/m{\ell}$). The cell viability was showed that only the DF had anti-proliferation effect on human cancer cell HT-29. These results suggested that both the DF and AF extract of Machilus thunbergii were potential materials for anti-diabetes and functional food for their radical scavenging activity.