• Steel and Composite Structures
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• v.18 no.6
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• pp.1353-1368
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• 2015

A finite element model is presented for the analysis of composite steel-concrete beams based on a refined high-order theory. The employed theory satisfies all the kinematic and stress continuity conditions at the layer interfaces and considers effects of the transverse normal stress and transverse flexibility. The global displacement components, described by polynomial or combinations of polynomial and exponential expressions, are superposed on local ones chosen based on the layerwise or discrete-layer concepts. The present finite model does not need the incorporating any shear correction factor. Moreover, in the present $C^1$-continuous finite element model, the number of unknowns is independent of the number of layers. The proposed finite element model is validated by comparing the present results with those obtained from the three-dimensional (3D) finite element analysis. In addition to correctly predicting the distribution of all stress components of the composite steel-concrete beams, the proposed finite element model is computationally economic.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.353-355
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• 2007

A simple technique for PFC circuit is presented using UC3854. This technique is about current peak controlling by a reference current generator. Decreased peak currents of the boost pre-regulator reduce circuit current stress and so rated currents of circuit elements are minimized. Simulation and experimental results will verify the viability of the new scheme.

• Journal of Power Electronics
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• v.3 no.4
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• pp.215-223
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• 2003

In this paper, a new zero-current-transition (ZCT) circuit cell is proposed. The main switch is turned-off under the zero current and zero voltage condition, and there is no additional current stress and voltage stress in the main switch and the main diode, respectively. The auxiliary switch is turned-off under the zero voltage condition, and the main diode is turned-on under the zero voltage condition. The resonant current required to obtain the ZCT condition is relatively small and regenerated to the input voltage source. The operational principles of a boost converter integrated with the proposed ZCT circuit cell are analyzed and verified by the simulation and experimental results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1681-1690
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• 1992

The effects of the stress ratio and the fiber orientation(0.deg./90.deg. and .+-.45.deg.) to the load direction on the fracture behavior of the glass/epoxy plain woven composites were studied. The tests were carried out using compact tension specimens under both static and fatigue loading. The values of $k_{a}$ obtained from the energy release rate are independent of notch depth(a/w=0.2~0.6) for the 0.deg./90.deg. specimens, but decreases with an increase in a/w for the .+-.45.deg. specimens. And $k_{q}$ has higher values than $k_{ASTM}$ has been evaluated by the ASTM E399 test procedure. It is shown in the relation between fatigue crack growth rate da/dN and stress intensity factor range .DELTA.K using modified shape correction factor that da/dN decreases with a decrease in stress ratio and is lower for .+-..deg. specimens than for 0.deg./90.deg. These phenomena can be explained by the crack deflection to the load direction.n.n.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.319-322
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• 1998

In this paper we further propose to add a very simple regenerative clamping circuit to SSIPP to reduce the voltage stress and to recycle the energy trapped in the leakage inductance of the isolation transformer, thus eliminating the need for a lossy snubber circuit. In addition, this proposed clamping circuit also provides a mechanism to reset the magnetizing current of the output transformer of SSIPP employing a Forward converter as the output stage. Simulations and experimental results are reported to verify the operation and performance of the SSIPP with regenerative clamping.

• Nuclear Engineering and Technology
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• v.43 no.1
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• pp.83-88
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• 2011

To define the effect of strain rate variation from 0.04% to 0.004%/s on environmental fatigue of CF8M cast stainless steel, which is used as a primary piping material in nuclear power plants, low-cycle fatigue tests were conducted at operating pressure and temperature condition of a pressurized water reactor, 15 MPa and $315^{\circ}C$, respectively. A high-pressure and high-temperature autoclave and cylindrical solid fatigue specimens were used for the strain-controlled low-cycle environmental fatigue tests. It was observed that the fatigue life of CF8M stainless steel is shortened as the strain rate decreases. Due to the effect of test temperature, the fatigue data of NUREG-6909 appears a slightly shorter than that obtained by KEPRI at the same stress amplitude of $1{\times}10^3$ MPa. The environmental fatigue correction factor $F_{en}$'s calculated with inputs of the test data increases with high strain amplitude, while the $F_{en}$'s of NUREG-6909 remain constant regardless of strain amplitude.

• Journal of Korean Academy of Nursing
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• v.44 no.6
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• pp.630-638
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• 2014

Purpose: The purpose of this study was to develop a scale to evaluate stress in elderly patients with coronary artery diseases (CAD) and to examine validity and reliability of the scale. Methods: The development process for the preliminary scale included construction of a conceptual framework and initial items, verification of content analysis, sentence correction, and pilot study. This study was conducted using a questionnaire survey with one-to-one interviews during January and February, 2012. Participants were 240 elderly patients with CAD. Data were analyzed using item analysis, factor analysis, criterion related validity, and internal consistency. Results: The developed scale consisted of 32 items and 6 factors - aging and disease (7 items), family relations (5 items), anxiety and withdrawal (9 items), management of daily living (3 items), compliance of medical regimen (4 items), poverty and finance (4 items), and explained 68.5% of total variance. The scale had significantly positive correlation with the Korean Perceived Stress Scale (KPSS). Cronbach's alpha was .96, and Guttman split half coefficient was .91. Conclusion: Results indicate that the Stress Scale for Elderly Patients with CAD has validity and reliability, and is a suitable scale in health care settings to assess stress in elderly patients with CAD.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1110-1113
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• 2002

A Single-Stage Single-Switch power-factor- correction(PFC) AC/DC Converter with universal input is presented in this paper. The PFC Converter can be achieved based upon the continuous current mode(CCM). The switch has less current and voltage stresses over a wide range of load variation so that a low voltage rating device can be used. The presented converter features high power factor high efficiency, and low cost. An 90W prototype was implemented to show that it has 70% efficiency with low voltage stress over universal line input.

• Journal of Fisheries and Marine Sciences Education
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• v.9 no.2
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• pp.209-221
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• 1997

This paper presents a soft switching unity power factor PWM rectifier, which features reduced conduction losses and soft switching with no auxiliary switches. The soft switching are achieved by using a simple commutation circuit with no auxiliary switches, and reduced conduction loses are achieved by employing a single converter, instead of a typical front end diode rectifier followed by a boost rectifier. Furthermore, thanks to good features such as simple PWM control at constant frequency, low switch stress and low VAR rating of commutation circuits, it is suitable for high power applications. The principle of operation is explained in detail, and major characteristics analysis and experimental results of the new converter also included.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.85-89
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• 2003

Many single-stage PFC(power-facto.-correction) ACHC converters suffer from the high link voltage at high input voltage and light load condition. In this paper, to suppress the link voltage, a novel high power factor high efficiency PFC AC/DC converter is proposed using the single controller which generates two gate signals so that one of them is used far gate signal of the flyback DC/DC converter switch and the other is applied to the Boost PFC stage. A 130w prototype for LCD monitor adapter with universal input $(90-265V_{rms})$ and 19.5V 6.7A output is implemented to verify the operational principles and performances. The experimental results show that the maximum link voltage stress is about 450V at 270Vac input voltage. Moreover, efficiency and power factor are over $84\%$ and 0.95, respectively, under the full load condition.