• Current Photovoltaic Research
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• v.4 no.2
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• pp.48-53
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• 2016

We report the effect of physical load on the stability of organic solar cells under physical loads. The active layers in organic solar cells were fabricated with bulk heterojunction films (BHJ) films of poly (3-hexylthiophene) and phenyl-$C_{61}$-butyric methyl ester. The loading time was varied up to 60 s by keeping the physical load constant. Results showed that the open circuit voltage was not influenced by the physical load but other solar cell parameters were sensitive to the loading time. The fill factor was very slightly increased at 15 s, while short circuit current density was well kept for 30 s. The power conversion efficiency was reasonably maintained for 45 s but became significantly decreased by the continuous loading for 60 s.

• Journal of electromagnetic engineering and science
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• v.7 no.3
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• pp.122-128
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• 2007

In this paper, we present the design and measurement of a side-fed circularly-polarized patch antenna with a dielectric loading. The antenna consists of a comer-truncated rectangular patch, an L-shaped ground plane, a dielectric loading material, and a coaxial probe. An antenna operating at the UHF band (910 MHz) for the RFID reader applications is optimized using a commercial software. The size of the patch is reduced by a factor of 1.73 by loading the patch with mono-cast(MC) nylon. Measurements of the fabricated antenna show performance characteristics comparable to those of much larger commercial RFID reader antennas.

• Journal of the Korean Ceramic Society
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• v.33 no.11
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• pp.1203-1208
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• 1996

Crack growth tests on silicon nitride have been made to clarify the crack growth characteristics under static and cyclic loading. Under constant K(K: stress intensity factor) static loading the crack growth rate in silicon nitride decreases with increasing crack extension and is finally arrested. The cack growth resistiance is largely reduced by the application of stress cycling and though the crack growth resistiacne increases with increasing of crack extension the increasing rate is much smaller under cyclic loading than under static loading.

• Structural Engineering and Mechanics
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• v.48 no.2
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• pp.275-289
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• 2013

The cross sections of multi-span beams are sometimes suddenly increased at the interior support of continuous beams to resist high negative moment. An earlier study on elastic lateral torsional buckling of stepped beams was conducted to propose new design equations. This research aims to continue the earlier study by considering the effect of inelastic buckling of stepped beams subjected to pure bending and general loading condition. A three-dimensional finite element-program ABAQUS and a statistical program MINITAB were used in the development of new design equations. The inelastic lateral torsional buckling strengths of 36 and 27 models for singly and doubly stepped beams, respectively, were investigated. The general loading condition consists of 15 loading cases based on the number of inflection point within the unbraced length of the stepped beams. The combined effects of residual stresses and geometrical imperfection were also considered to evaluate the inelastic buckling strengths. The proposed equations in this study will definitely improve current design methods for the inelastic lateral-torsional buckling of stepped beams and will increase efficiency in building and bridge design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.238-243
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• 2011

This study compared Kd, loss factor and thickness of floor impact isolator by loading/unloading heat treatment with results by continuous loading treatment and checked problem and improvement method of heat treatment condition for the long-term stability evaluation of the floor impact isolation. As the results, it is required the change of heat treatment condition unloading now to loading as actual weigh on the floor impact isolator.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.521-522
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• 2006

Occlusal loading is considered as the main factor of noncarious cervical lesions. The goal of this study is to identify stress distribution using three dimensional finite element analysis, when occlusal loading is applied on the cervical lesion of human tooth. A finite element model was constructed from micro-CT image and three kinds of static force(500 N) were assumed. In all cases stress concentrates on the same area in the cement-enamel junction. This finding is consistent with published experimental results.

• Journal of Mechanical Science and Technology
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• v.20 no.10
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• pp.1541-1547
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• 2006

An efficient procedure to obtain the optimal stacking sequence and the minimum weight of stiffened laminated composite curved panels under several loading conditions and stiffener layouts has been developed based on the finite element method and the genetic algorithm that is powerful for the problem with integer variables. Often, designing composite laminates ends up with a stacking sequence optimization that may be formulated as an integer programming problem. This procedure is applied for a problem to find the stacking sequence having a maximum critical buckling load factor and the minimum weight. The object function in this case is the weight of a stiffened laminated composite shell. Three different types of stiffener layouts with different loading conditions are investigated to see how these parameters influence on the stacking sequence optimization of the panel and the stiffeners. It is noticed from the results that the optimal stacking sequence and lay-up angles vary depending on the types. of loading and stiffener spacing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.654-661
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• 2001

In this study, fatigue growth behavior of the transverse crack, which was the most dangerous damage among the various types of rail defects, was investigated using the notched keyhole specimen under constant amplitude loadings. Fatigue limit of smooth specimen in rail steel at R=0 was 110MPa, and the fatigue crack initiation life in the region of the low stress amplitude (ie. long life) occupied the major portion of the total fatigue life. The fatigue strength under variable amplitude loading was converted to the equivalent fatigue strength based upon. Miners rule, which was estimated approximately 9% lower than that under constant amplitude loading. Also, in the low ΔK(sub)rms region ($\leq$21MPa√m), fatigue crack growth rate (da/dN) under constant amplitude loading was higher than that under variable amplitude loading, whereas the tendency was reversed in the high ΔK(sub)rms region. It is believed that this behavior is due to the transition of fracture appearance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.772-778
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• 2009

By rising the interests of the railroad, It has been required the research about railroad structure. And since 2000, the study about railway bridges caused by steel box railway bridges has been only 0.2%. So I was hard to find out about steel box railway bridges. In this study, I evaluate and analyze 4 types(KTX, Saemaeul, Mugunghwa, Freight) of dynamic caused by train loading, natural frequency and damping ratio, verticality deflection and verticality acceleration, end slope deflection, impact factor for dynamic characteristics analysis. natural frequency was measured 2.45Hz~3.34Hz and damping ratio revealed for 1.26~2.84%. Maximum verticality deflection(4.86mm) was sufficiently satisfied the design criteria(30.1mm), but in the case of verticality acceleration's respond, design criteria BRDM(Bridge Design Manual) & CTRL presentation derive rail limit value 0.35g be more than value 6 time recorded, maximum was measured 0.49g in 3 kinds of train(KTX, Saemaeul, Mugunghwa), except for Freight. Survey impact factor of Experiment bridge was 0.20 which is measured when the KTX(15:04) was driving. impact factor is enough contended with design criteria 0.29 which is presented in domestic railway design criteria and thoroughly guarantee the dynamic stability.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.846-851
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• 2017

Piezoelectricity is the capability of a piezoelectric material to change mechanical energy into electrical energy. The determination of electrical and mechanical properties plays a significant role in characterizing the piezoelectric material. The energy losses characteristics of piezoelectric material can be described by mechanical quality factor. In this paper, the output voltage and mechanical quality factor of Lead Zirconate Titanate (PZT-4A) piezoelectric material is determined under various resistance and loading conditions by using the test setup. The commercial FEM software ABAQUS is used to analyze the performance of piezoelectric material under static loading conditions. It is observed that these properties affect the performance of a material particularly in the designing of smart structures. The experimental results are partially compared to the simulation values.