• Journal of Power Electronics
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• 제16권2호
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• pp.572-583
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• 2016

In view of the speed control characteristics of induction traction motors and the problems of direct torque control (DTC) algorithms in current applications, this paper presents a DTC algorithm characterized by a symmetrical polygon flux control and a closed loop power control in the constant-torque base speed region and constant-power field-weakening region of induction traction motors. This algorithm only needs to add a stator flux control algorithm to the traditional DTC structures. This has the benefit of simplicity, while maintaining the features of traditional algorithms such as a rapid dynamic response, uncomplicated control circuit, reduced dependence on motor parameters, etc. In addition, it obtains a smoother flux trajectory that is conducive to improvement of the harmonic elimination capability, the switching frequency utilization as well as the torque and power performance in the field-weakening region. The effectiveness and feasibility of this DTC algorithm are demonstrated by both theoretical analysis and experimental results.

• Journal of Information Science Theory and Practice
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• 제11권1호
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• pp.31-48
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• 2023

Digital service transformation study is a part of research in the field of digital transformation, which is devoted to exploring the transformations that occur in digital service products, which have been intensely explored in recent years to address digital disruption. Several concepts and definitions of digital service transformation have emerged as a result of an approach from the point of view of digital transformation and digital services concepts. This paper is organized to provide a foundational understanding of digital service transformation terminology. This paper uses the systematic literature review method to compile 52 qualified articles from previous studies. We conduct an analysis and synthesis of articles to answer research questions. The results of this study are a descriptive summary of research in the digital service transformation field, determining digital service transformation terminology and components, and also a proposed digital service transformation model to explain the position of transformation in digital service products in the overall transformation process. We construct this model using the findings of previously determined components synthesis.

• Solar Energy
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• 제18권2호
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• pp.1-17
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• 1998

In order to analyze the status of development of solar thermal technology in Korea, importance and characteristics of solar thermal technology is considered. That is, solar collector, solar hot water heater, solar industrial system and solar buildings is analyzed in the view of worldwide technology, And then, domestic insolation sources and sale amounts of solar system is introduced. In this paper, it Is presented long-term objective in the basic plan of development new & rowable energy in Korea. As a result of analysis, the status of solar thermal technology in Korea is pactical use state in the field of low temperature use and application state in the field of mid-temperature use.

• Korean Journal of Materials Research
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• 제30권2호
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• pp.99-104
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• 2020

Recent discoveries of ferroelectric properties in ultrathin doped hafnium oxide (HfO₂) have led to the expectation that HfO₂ could overcome the shortcomings of perovskite materials and be applied to electron devices such as Fe-Random access memory (RAM), ferroelectric tunnel junction (FTJ) and negative capacitance field effect transistor (NC-FET) device. As research on hafnium oxide ferroelectrics accelerates, several models to analyze the polarization switching characteristics of hafnium oxide ferroelectrics have been proposed from the domain or energy point of view. However, there is still a lack of in-depth consideration of models that can fully express the polarization switching properties of ferroelectrics. In this paper, a Zr-doped HfO₂ thin film based metal-ferroelectric-metal (MFM) capacitor was implemented and the polarization switching dynamics, along with the ferroelectric characteristics, of the device were analyzed. In addition, a study was conducted to propose an applicable model of HfO₂-based MFM capacitors by applying various ferroelectric switching characteristics models.

• KSBB Journal
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• 제27권2호
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• pp.121-126
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• 2012

In order to explore structural features of minoxidil analogs with a view of enhancing lysyl hydroxylase (LH) inhibitory activity, molecular holographic QSAR (HQSAR) and CoMSIA (comparative molecular similarity indices analysis) were performed. The results from the atomic contributions with optimized the HQSAR 6-2 model indicated that, in case of pyrimidine-1-N-oxide substituent, C2 atom of pyrimidine ring and C'3-C'4 bond of 4-piperidinol group showed the highest impact on the inhibitory activity towards LH enzyme. It was also evident from the information of the optimized CoMSIA F5 model that the inhibitory activity mainly depended on the hydrophobic field contribution (36%) and the hydrogen bond (H-bond) field contribution (49.2%) of substrate molecule. Particularly, it is predicted that the functional groups which disfavor H-bond acceptors in large space around the piperidinol group and also the functional groups which favor the H-bond acceptors at C'4 (& C'5) atom in $R_5$ group play a role for increased inhibitory activity. With this in mind, it is likely that a novel candidate having more improved inhibitory activity on hair growth could be designed in the future.

• Journal of the Korean Society of Visualization
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• 제7권1호
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• pp.3-8
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• 2009

Most vehicles have a heating, ventilating and air conditioning (HVAC) device to control the thermal condition and to make comfortable environment in the passenger compartment. The improvement of ventilation flow inside the passenger compartment is crucial for providing comfortable environment. For this, better understanding on the variation of flow characteristics of ventilation air inside the passenger compartment with respect to various ventilation modes is strongly required. Most previous studies on the ventilation flow in a car cabin were carried out using computational fluid dynamics (CFD) analysis or scale-down water-model experiments. In this study, whole ventilation flow discharged from the air vent of a real passenger car was measured using a special PIV (particle image velocimetry) system for large-size FOV (field of view). Under real recirculation ventilation condition, the spatial distributions of stream-wise turbulence intensity and mean velocity were measured in the vortical panel-duct center plane under the panel ventilation mode. These experimental data would be useful for understanding the detailed flow structure of real ventilation flow and validating numerical predictions.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제5권3호
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• pp.145-159
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• 1985

An understanding of interrelationships among basic characteristics of vehicular traffic flow, such as volum, speed, headtime, and density, is of prime importance. Similarly in providing proper level of servicebility in the field of base of design and traffic control, it is deeply connected. After all, with a view to improve traffic flow characteristics, future efforts about the mutual function development between rod and traffic should be made on the basis of present traffic characteristics. This paper figures out some traffic characteristics from field data and provides proper model of equation to estimate traffic volume on the road.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.574-581
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• 2014

This paper presents the design and evaluation of the optical zoom system for an LWIR camera. The 12.8operating wavelength range of this system is from $7.7{\mu}m$ to $12.8{\mu}m$. Through a paraxial design and optimization process, we have obtained the extended four-group inner-focus zoom system with focal lengths of 10 to 100 mm, which consists of the six lenses including four aspheric surfaces and two diffractive surfaces. The diffractive lenses were used to balance the higher-order aberrations, and its diffraction properties were evaluated by scalar diffraction theory. We have calculated the polychromatic integrated diffraction efficiency and the MTF drop generated by background noise. The f-number of the zoom system is F/1.4 at all positions. Fields of view are given by $51.28^{\circ}{\times}38.46^{\circ}$ at wide field and $5.50^{\circ}{\times}4.12^{\circ}$ at narrow field positions. In conclusion, this design procedure results in a $10{\times}$ compact zoom lens system useful for an LWIR camera.

• Journal of the Korean Society for Marine Environment & Energy
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• 제5권3호
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• pp.10-15
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• 2002

The assessment of PIV to measure the mean velocity and turbulence was carried out over a train of fixed two-dimensional dunes. The agreement between the PIV and LDV is good enough even in regions of flow reversals and high shear. Though limited in the wall normal direction field-of-view, PIV provides instantaneous flow fields, which reveal the complex nature of flow over dunes, as well as more sophisticated analyses such as two-point space correlation and quadrant analysis with a reasonable accuracy The present study is expected to be directly applied to more complex flow such as sediment transport.

• SUVANNABHUMI
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• 제13권1호
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• pp.7-33
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• 2021

With a view to contributing to the epistemological and methodological debates in Southeast Asian Studies, the aim of this paper is to examine critically the epistemic concepts and approaches in the social sciences and then to seek an epistemic reflexivity and its potential methodological applications to Southeast Asian Studies. Although the field of social sciences has attempted to search for a means of tackling the ontological and epistemological dilemmas in its major paradigms, Southeast Asian Studies still demands a more 'actor-centered' epistemic account of reflexive interaction between actors and social structures. Bearing in mind the need for a more 'actor-centered' epistemic approach, this paper continues to discuss the 'epistemic reflexivity' in the social sciences and its potential applications to Southeast Asian Studies. In this paper, I will consider 'epistemic reflexivity' as an alternative methodological orientation. It emerges as interlinked with the ontological standpoint of what is called 'reflexive approaches' and its application to the detailed 'reflexive methodology' which I am proposing in this paper. In doing so, this paper discusses the autobiographical experiences of the author arising from his ethnographic field research in North Sulawesi, Indonesia and their implication for a reflexive methodology in Southeast Asian Studies. In conclusion, the paper argues that we need a 'more actor-centered' epistemic framework to compensate for the epistemological and methodological dilemmas in the social sciences and the alternative framework will equip Southeast Asian Studies with a reflexive methodology relevant to the life-dynamics of the social world in the process of developing its inquiries, methodological technics, analysis, and validation.