• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.415-419
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• 2003

This paper focuses on a simple technique to reduced torque ripple in the direct torque control inverter for PMSM drive. It is actually impossible to raise the inverter switching frequency in the conventional system, although the hysterisis bandwidths for the stator flux and torque control are sufficiently diminished, because of the sampling Interval and the delay in estimating the flux and the torque In order to overcome the problem, the proposed method introduces a dithering technique into the conventional system by superposing triangular waves with high frequency and minute amplitude on the torque error. And the programable 3- stage lowpass filter is added instead of pure Integrator. Simulation results prove the feasibility of proposed strategy compared with conventional method.

• Journal of Electrochemical Science and Technology
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• 제6권3호
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• pp.81-87
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• 2015

This study introduces a facile strategy to prepare metal oxide/conducting polymer nanocomposites that may have promising applications in energy storage devices. Ploy aniline/nano wire manganese dioxide (PANI/NwMnO₂) was synthesized by cyclic voltammetry on glassy carbon electrode. Morphology and structure of the composite, pure PANI, MnO₂ nanowires were fully characterized using XRD and SEM analysis. Electrochemical studies shows excellent synergistic effect between PANI and MnO₂ nanowires which results in its capacitance increase and cycle stability against PANI electrode. Specific capacitances of PANI/NwMnO₂ and PANI were 456 and 190 F/g respectively. The electrochemical performance of electrodes studied using cyclic voltammetry, Galvanostatic charge/discharge and impedance spectroscopy.

• 대한핵의학회:학술대회논문집
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• 대한핵의학회 2001년도 제40차 춘계학술대회 및 연수교육
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• pp.60-65
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• 2001

The positron emission tomography (PET) has been used for the evaluation of the characteristics of various tumors. The role of PET in oncology has been evolved from a pure research tool to a methodology of enormous clinical potential. The unique characteristics of PET imaging make sophisticated quantitation possible. Several quantitative methods, such as standardized uptake values (SUV), simplified quantitative method, Patlak graphical analysis, and Sokoloff's glucose metabolism measurement, have been used in the field of oncology. However, each quantitative method has limitations of its own. For example, the SUV has been used as a quantitative index of glucose metabolism for tumor classification and monitoring response to treatment, even though it depends on blood glucose level, body configuration of patient, and scanning time. The quantitative methods of PET are reviewed and strategy for implementing these methods are presented.

• 전기학회논문지
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• 제59권12호
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• pp.2150-2156
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• 2010

In this paper, we investigate how an electricity capacity market design may encourage generators to exaggerate their available capacity. In order for an analytical approach, a two player game model is introduced. We focus on two pure strategy Nash equilibria: an equilibrium at which generators offer their true capacities, and an equilibrium at which generators offer exaggerated capacities. The latter case is caused by asymmetries of information between players and so called 'moral hazard' in terms of the economics literature. This paper shows that, considering practical electricity markets, the moral hazard case is highly probable. Moreover, it is shown that, with the considered capacity market design in the real world, the better the electricity energy market performs, the higher the risk of moral hazard becomes.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.19-19
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• 2003

The injection of spins into nonmagnetic semiconductors has recently attracted great interest due to the potential to create new classes of spin-dependent electronic devices. A recent strategy to achieve control over the spin degree of freedom is based on dilute ferromagnetic semiconductors. Ferromagnetism has been reported in various semiconductor groups including II-Ⅵ, III-V, IV and II-IV,-V$_2$, which will be reviewed. On the other hand, to date the low solubility of magnetic ions in non-magnetic semiconductor hosts and/or low Curie temperature have limited the opportunities. Therefore the search for other promising ferromagnetic semiconducting materials, with high magnetic moments and high Curie temperatures (Tc), is of the utmost importance. In this talk, we also introduce new pure ferromagnetic semiconductors, MnGeP$_2$ and MnGeAs$_2$, exhibiting ferromagnetism and a magnetic moment per Mn at 5K larger than 2.40 ${\mu}$B. The calculated electronic structures using the FLAPW method show an indirect energy gap of 0.24 and 0.06 eV, respectively. We have observed spin injection in MnGeP$_2$ and MnGeAs$_2$ magnetic tunnel junctions through semiconducting barriers.

• Management Science and Financial Engineering
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• 제1권1호
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• pp.1-19
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• 1995

In this paper, we analyze an M / M / 1 queueing system where there are incentive conflicts among customers. Self-interested customers' decisions whether to join the system or not may not necessarily induce a socially optimal congestion level. As a way to alleviate the over-congestion, toll imposition was used in Naor's paper [3]. Instead of using a toll mechanism, we study the usefulness of imperfect information on system state (queue size, for example) as a way to reduce the over-congestion by self-interested customers. The main conclusion of this paper is that by purposefully giving fuzzy or imperfect information on the current queue size we can improve the congestion in the system. This result might look contradictory to rough intuition since perfect information should give better performance than imperfect information. We show how this idea is verified. In deriving this result, we use the concept of Nash equilibrium (pure and mixed strategy) as introduced in game theory. In some real situations, using imperfect information is easier to apply than imposing a toll, and thus the result of this paper has practical implications.

• KSTLE International Journal
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• 제4권2호
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• pp.43-46
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• 2003

Water-lubricated frictional characteristics of a stainless steel ball bearings are not well known compared to the oil-lubricated frictional characteristics. Furthermore a study on friction at a high temperature is rare because the bearing maintenance strategy for water-lubricated or chemicals-lubricated bearings of equipment is generally based on the replacement of the failed bearings-and parts. Ball bearings and ball screw are installed in the power transmission for the newly developing integral reactor and these are lubricated with chemically-controlled pure water at a high temperature and a high pressure. Bearings and power transmitting mechanical elements for an atomic reactor requires high reliability and high performance during the estimated lifetime, and it should be verified. In this paper, experimental research results of the frictional characteristics for water-lubricated ball bearings are presented as a preliminary investigation.

• Journal of Information Technology Applications and Management
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• 제16권4호
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• pp.185-203
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• 2009

The literature reveals that service quality is critical determinants affecting customer satisfaction in the retail industry. Recent online B2C studies also show that service quality significantly influences online customer satisfaction. However, research on analyzing antecedents to determine the service quality level of online shopping has not been sufficiently reported. Moreover, the offline synergy effect on the Internet shopping mall has been presented mostly at a conceptual level. The purpose of this study is to investigate key managerial variables exploiting offline synergy, including pure online attributes, that impact on service quality of the click and mortar Internet shopping mall. A survey was conducted for empirical validation of the hypotheses. The results indicate that core offline synergy factors significantly enhance the perceived service quality level of the Internet shopping mall. Implications, limitations, and future research directions are also discussed.

• Journal of Information Technology Applications and Management
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• 제24권4호
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• pp.1-12
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• 2017

Item-based collaborative filtering (IBCF) is an important technology that is widely used in recommender system of online shopping malls. It uses historical information to compute item-item similarity and make predictions. However, in offline shopping each customer's purchasing pattern can be occurred continuously and repeatedly due to time and space constraints contrast to online shopping. Those facts can make IBCF to have limitations from being applied to offline shopping malls directly. In order to improve the quality of recommendations made by IBCF in offline shopping mall, we propose an ensemble approach that considers both item-item similarity of IBCF and each customer's purchasing patterns which are modeled by item networks. Our experimental results show that this approach produces recommendation results superior to those of existing works such as pure IBCF or bestseller approaches.

• 생물정신의학
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• 제17권4호
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• pp.194-202
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• 2010

Alzheimer's disease(AD) is the most common neurodegenerative disorder and constitutes about two thirds of dementia. Despite a lot of effort to find drugs for AD worldwide, an efficient medicine that can cure AD has not come yet, which is due to the complicated pathogenic pathways and progressively degenerative properties of AD. In its early clinical phase, it is important to find the subtle alterations in synapses responsible for memory because symptoms of AD patients characteristically start with pure impairment of memory. Attempts to find the target synaptic proteins and their pathogenic pathways will be the most powerful alternative strategy for developing AD medicine. Here we review recent progress in deciphering the role of target synaptic proteins related to AD in hippocampal glutamatergic synapses.