• Journal of Power Electronics
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• v.16 no.5
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• pp.1678-1688
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• 2016

This paper presents a capacitive power transfer (CPT) system using a Class-E resonant inverter. A Class-E resonant inverter is chosen because of its ability to perform DC-to-AC inversion efficiently while significantly reducing switching losses. The proposed CPT system consists of an efficient Class-E resonant inverter and capacitive coupling formed by two flat rectangular transmitter and receiver plates. To understand CPT behavior, we study the effects of various coupling distances on output power performance. The proposed design is verified through lab experiments with a nominal operating frequency of 1 MHz and 0.25 mm coupling gap. An efficiency of 96.3% is achieved. A simple frequency tracking unit is also proposed to tune the operating frequency in response to changes in the coupling gap. With this resonant frequency tracking unit, the efficiency of the proposed CPT system can be maintained within 96.3%-91% for the coupling gap range of 0.25-2 mm.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.455-465
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• 2008

In this study, the load distribution and deformation of rock-socketed drilled shafts subjected to axial load are investigated based on small scale model tests. In order to analyze the effects of major influencing factors of end bearing capacity, Hoek-cell triaxial tests were performed. From the test results, it was found that the initial slope of end bearing load transfer (q-w) curve was highly dependent on rock mass modulus and pile diameter, while the ultimate unit toe resistance ($q_{max}$) was influenced by rock mass modulus and the spacing of discontinuities. End bearing load transfer function of drilled shafts socketed in rock was proposed based on the Hoek-cell triaxial test results and the field loading tests which were performed on granite and gneiss in South Korea. Through the comparison with pile load tests, it is found that the load-transfer curve by the present study is in good agreement with the general trend observed by field loading tests, and thus represents a significant improvement in the prediction of load transfer of drilled shaft.

• Journal of Korean Academy of Nursing
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• v.38 no.3
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• pp.353-362
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• 2008

Purpose: This study was conducted to analyze and clarify the meaning of the concept for relocation stress -focusing on patients transferred from an intensive care unit to a general ward. Methods: This study used Walker and Avant's process of concept analysis. Results: Relocation stress can be defined by these attributes as follows: 1) involuntary decision about relocation, 2) moving from a familiar and safe environment to an unfamiliar one, 3) broken relationship of safety and familiarity, 4) physiological and psychosocial change after relocation. The antecedents of relocation stress consisted of these facts: 1) preparation degrees of transfer from the intensive care unit to a general ward, 2) pertinence of the information related to the transfer process, 3) change of major caregivers, 4) change in numbers of monitoring devices, 5) change in the level of self-care. There are consequences occurring as a result of relocation stress: 1) decrease in patients' quality of life, 2) decrease in coping capacity, 3) loss of control. Conclusion: Relocation stress is a core concept in intensive nursing care. Using this concept will contribute to continuity of intensive nursing care.

• Journal of Korean Clinical Nursing Research
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• v.14 no.1
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• pp.139-150
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• 2008

Purpose: The aim of this study was to develop instrument measuring the relocation stress syndrome for patients transferred from intensive care unit to general ward in Korea. Method: For item construction, components were drawn from an extensive review of the literature, existing instruments and the result of qualitative approach. A total 48 items were selected for the first draft. Ten experts evaluated this instrument for content validity and the number of items was reduced to 29. To refine and test reliability and validity of the instrument, data were collected from the 594 patients following transfer from intensive care unit. Results: Preliminarily twenty-nine items were generated through content validity and a pilot study. Using corrected items to total correlation coefficient, this instrument was further shortened to a 25 item scale. Factor analysis extracted a total of 23 items with a 5-point Likert-type scale. Relocation Stress Syndrome (RSS) included three subscales; physical factors (12 items), Patient's recognition to health care providers (8 items), and emotional factors (3 items). The RSS established content validity, construct validity, and reliability. Conclusion: This instrument demonstrates good reliability and validity, and therefore it is an appropriate measurement of assessing relocation stress syndrome in ICU to ward transition period.

• Asia pacific journal of information systems
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• v.25 no.3
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• pp.445-472
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• 2015

Although knowledge transfer between two different parties occurs in IS development projects, the majority of prior studies focused on knowledge transfer from IT consultants to clients. Considering two parts of knowledge transfer in IS development projects, we must consider both 'where knowledge is transferred from' and 'where it is transferred to'. Therefore, in this study, we attempt to describe two different routes of knowledge transfer, such as knowledge transfer from an IT consultant to a client and knowledge transfer from a client to an IT consultant. In this regard, we have examined the effect of two different routes of knowledge transfer on system implementation success in IS development project. Specifically, we adopted the knowledge stock-flow theory to examine the causal relationship between IT consulting firms and clients in terms of knowledge transfer and eventual system implementation success. Survey data collected from 213 pairs of individuals (both clients and IT consultants) were used to test the model using three different analytic approaches such as PLS (partial least squares) and two types of mediated regression techniques. We found that knowledge transfers partially mediated both the relationships between IT consultants' IT skills (project members' business knowledge) and system implementation success. Furthermore, the effects of each knowledge transfer were distinguished by depending on the types of system, such as ERP or groupware. Our attempts have significant implications for both research and practice given the importance of effective knowledge transfer to IT consulting.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.324-330
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• 2012

In this paper, we presents a robust control system design for compensating hysteresis of a piezoelectric actuator-based actuation unit. First, the dynamics between the input voltage and the output displacement of the actuation unit are unravelled via a non-parametric system identification method. From the dynamic characteristics of those experimental transfer functions, a parametric model is then derived, whose dynamics match those of the non-parametric ones under various conditions on input voltages. A robust controller is constructed on the basis of this parametric model in order not only to effectively compensate the hysteresis of the actuation unit but also to guarantee the robust stability. Extensive experiments show that the proposed robust control system successfully mitigate the effect of the hysteresis and improve the tracking capability of the actuation unit.

• Journal of Advanced Navigation Technology
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• v.18 no.1
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• pp.35-43
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• 2014

In this paper, it is about to non-contact wireless power transmission according to various conditions of self induction principle between the two planar coils at a transmission unit and a receiving unit based on the theory of wireless power transmission. The experiments are occurred in order to power transfer of noncontact method from designed wireless circuits in the primely coil and secondary coil, and the applying to Half Bridge Resonant converter transmission unit and receiving unit. and that were able to prepared circumstance to calculate of the output voltage and power source. The main power of the inductive coupling the resonant converter at the transmission unit is converted electrical energy using the solar cell module and artificial light source (halogen lamp) as a replace light and received 24 V power supply from solar power was used a input power source for the wireless power transmission device. Experimental results, to received of power is used to illuminate the lighting and to charge the battery in receiving circuit.And the wireless power transmission efficiency measured at the output side of the transmission unit is obtained about 70% to 89% compared to input power of receiving unit.In addition, efficiency were tested through ID verification method and comparing the phase difference between the voltage when foreign substances interfere with wireless power transmission.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.357-362
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• 2006

This research focused on the multi-pass heat exchanger using the minichannel possessing the spring fin. An air-water was used as working fluid. The characteristics of liquid single phase heat transfer were verified. The compact heat exchanger (heat transfer area density : ${\beta}=2,146 m^2/m^3$), based on the shape of header(Top combining header), 63 minichannels ($D_i$ : 1.4 mm, L : 0.25 m) and the air side adopting the copper wire spring fin, was fabricated. The heat transfer area density of the air side was improved up to 161% when compared with the conventional fin-tube heat exchanger that adopts the heat transfer tube with the inner diameter of 5 mm. With regard to heat transfer performance, heat transfer rate per unit volume increased up to 142% when compared with the fin-tube heat exchanger adopting the heat transfer tube with the inner diameter of 5 mm.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.1888-1893
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• 2007

In this study, the microchannel plated heat exchanger were numerically studied for the enhancement of heat transfer in the channel configuration. Unit cold and hot fluid region with the microchannel were modeled and periodic boundary condition at the side wall was applied to continuously repeating geometry. The material of micro-structured plate is STS304 and working fluid is water. Triangular obstacles were placed in micro channel to enhance heat transfer. The performance of microchannel plated heat exchangers were numerically investigated with various obstacle configuration and Reynolds number under the parallel and counter flows. Heat transfer rate has increased about 18% compared with straight channel, but pressure drop also increased about 3.5 times. The main factor of increasing of pressure drop and heat transfer rate is considered that the momentum was lost to collide against obstacles, generation of secondary flow and boundary layer separation, wake and vortex forming phenomena.

• Environmental Engineering Research
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• v.16 no.1
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• pp.47-51
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• 2011

The oxygen transfer rate is a parameter that characterizes the gas-liquid mass transfer in surface aerators. Gas-liquid transfer mechanisms in surface aeration tanks depend on two different extreme lengths of time; namely, macromixing and micromixing. Small scale mixing close to the molecular level is referred to as micromixing; whereas, macromixing refers to mixing on a large scale. Using experimental data and numerical simulations, macro- and micro-scale parameters describing the two extreme time scales were investigated. A scale up equation to simulate the oxygen transfer rate with micromixing times was developed in geometrically similar baffled surface aerators.