• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.998-1001
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• 2009

A new flexible TFT backplane structure with improved mechanical reliability is proposed. Amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors based on this structure have been fabricated on a polyimide substrate, and the resultant mechanical durability has been evaluated in a cyclic bending test. The panel can withstand 10,000 bending cycles at a bending radius of 5 mm without any noticeable TFT degradation. After 10K bending cycles, the change of threshold voltage, mobility, sub-threshold slope, and gate leakage current were only -0.22V, -0.13$cm^2$/V-s, -0.05V/decade, and $-3.05{\times}10^{-13}A$, respectively.

• 재활복지공학회논문지
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• 제7권1호
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• pp.39-43
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• 2013

본 논문에서는 근전도를 이용하여 근피로도를 분석함에 있어서 중앙주파수의 임계점을 이용한 효과적인 보행재활훈련 방법을 제시한다. 신호의 측정을 위하여 건강한 성인 남성 5명을 대상으로 실험을 실시하였고 정상 보행에서의 대퇴사두근, 전경골근에 표면전극을 붙여 변화를 측정 하였다. 근전도신호의 측정을 위하여 트레드밀 위에서 30분간 6km/h의 일정한 속력으로 보통걸음을 실시하였고 이를 통해 측정된 근전도신호를 주파수 분석 및 중앙주파수를 계산하여 근피로도를 수치화 한 뒤 30분간 근피로도의 상태와 포화되는 지점을 찾아 이를 근육이 견딜 수 있는 임계점, 즉 근육의 한계로 설정하였다. 실험 결과 근육의 임계점을 정량화 할 수 있었다.

• International Journal of Fluid Machinery and Systems
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• 제3권4호
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• pp.352-359
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• 2010

In recent years, the market has shown increasing interest in pump-turbines. The prompt availability of pumped storage plants and the benefits to the power system achieved by peak lopping, providing reserve capacity, and rapid response in frequency control are providing a growing advantage. In this context, there is a need to develop pumpturbines that can reliably withstand dynamic operation modes, fast changes of discharge rate by adjusting the variable diffuser vanes, as well as fast changes from pumping to turbine operation. In the first part of the present study, various flow patterns linked to operation of a pump-turbine system are discussed. In this context, pump and turbine modes are presented separately and different load cases are shown in each operating mode. In order to create modern, competitive pump-turbine designs, this study further explains what design challenges should be considered in defining the geometry of a pump-turbine impeller. The second part of the paper describes an innovative, staggered approach to impeller development, applied to a low head pump-turbine project. The first level of the process consists of optimization strategies based on evolutionary algorithms together with 3D in-viscid flow analysis. In the next stage, the hydraulic behavior of both pump mode and turbine mode is evaluated by solving the full 3D Navier-Stokes equations in combination with a robust turbulence model. Finally, the progress in hydraulic design is demonstrated by model test results that show a significant improvement in hydraulic performance compared to an existing reference design.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.294-295
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• 2006

Varistor fabricated with ZnO nano-powder was studied about the characteristic of energy capability in this paper. ZnO nano-powder varistor were sintered in air at $1050\;^{\circ}C$. The electrical properties and residual voltage of ZnO nano-powder varistor were obtained. Our ZnO nano-powder varistor has about 3 times of electric field at varistor voltage as compared with commercial ZnO varistor fabricated with micro-powder. In the current impulse withstand test, our nano varistor has had better performance than micro varistor. To analysis energy capability take infrared images for pyrexia distribution of each varistor. ZnO Nano-powder varistor has shown much quick response property because of increasing effective cross-section.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.319-319
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• 2010

Dye-sensitized solar cells (DSSCs) based on plastic substrates have attracted much attention mainly due to extensive applications such as ubiquitous powers, as well as the practical reasons such as light weight, flexibility and roll-to-roll process. However, conventional high temperature fabrication technology for glass based DSSCs, cannot be applied to flexible devices because polymer substrates cannot withstand the heat more than $150^{\circ}C$. Therefore, low temperature fabrication process, without using a polymer binder or thermal sintering, was required to fabricate necked $TiO_2$. In this presentation, we proposed polymer-inorganic composite photoelectrode, which can be fabricated at low temperature. The concept of composite electrode takes an advantage of utilizing elastic properties of polymers, such as good impact strength. As an elastic material, poly(methyl methacrylate) (PMMA) is selected because of its optical transparency and good adhesive properties. In this work, a polymer-inorganic composite electrode was constructed on FTO/glass substrate under low temperature sintering condition, from the mixture of PMMA and $TiO_2$ colloidal solution. The effect of PMMA composition on the photovoltaic property was investigated. Then, the enhanced mechanical stability of this composite electrode on ITO/PEN substrate was also demonstrated from bending test.

• Steel and Composite Structures
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• 제30권2호
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• pp.97-108
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• 2019

This paper presents a new model for the strap combined footings to obtain the most economical contact surface on the soil (optimal dimensioning) to support an axial load and moment in two directions to each column. The new model considers the soil real pressure, i.e., the pressure varies linearly. Research presented in this paper shows that can be applied to the T-shaped combined footings and the rectangular combined footings. The classical model uses the technique of test and error, i.e., a dimension is proposed, and subsequently, the equation of the biaxial bending is used to obtain the stresses acting on each vertex of the strap combined footing, which must meet the conditions following: The minimum stress should be equal or greater than zero, and maximum stress must be equal or less than the allowable capacity that can withstand the soil. Numerical examples are presented to obtain the optimal area of the contact surface on the soil for the strap combined footings subjected to an axial load and moments in two directions applied to each column. Appendix shows the Tables 4 and 5 for the strap combined footings, the Table 6 for the T-shaped combined footings, and the Table 7 for the rectangular combined footings.

• Geomechanics and Engineering
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• 제28권4호
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• pp.375-384
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• 2022

The glacial tills and shales in Midwestern states of the USA often show strength degradation after construction. They are often in need of applying soil modification techniques to remediate their strength degradation with weathering process. This study investigated the weathering durability of these natural soils and biopolymer treated soils by comparing direct shear test results for wet-dry and wet-freeze-thaw-dry cycled specimens. The tests showed that untreated glacial tills maintained only 62% and 50% initial shear strength after eight wet-dry cycles and eight wet-freeze-thaw-dry cycles, respectively. These untreated soils could not withstand by themselves after 16 weathering cycles. The same soils treated with 1.5% (by dry weight) food-grade Xanthan gum maintained 140% and 88% initial shear strength of untreated soils after 16 weathering cycles for wet-dry cycles and wet-freeze-thaw-dry cycles, respectively. The same soils treated with 1.5% (by dry weight) Gellan gum maintained 82% and 60% initial shear strength of untreated ones after 16 weathering cycles, respectively. Similar results were obtained for crushed shales, manifesting that the biopolymerization method may be adopted as a new eco-friendly method to enhance the weathering durability of these problematic soils of glacial tills and shales.

• Structural Engineering and Mechanics
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• 제81권3호
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• pp.317-333
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• 2022

Visco-Plastic Damper (VPD) as a passive energy dissipation device with dual behavior has been recently numerically studied. It consists of two bent steel plates and segments with a viscoelastic solid material in between, combining and improving characteristics of both displacement-dependent and velocity-dependent devices. In order to trust the performance of VPD, for the 1st time this paper experimentally investigates prototype damper behavior under a wide range of frequency and amplitude of dynamic loading. A high-axial damping rubber is innovatively proposed as the viscoelastic layer designed to withstand large axial strains and dissipate energy accordingly. Test results confirmed all assumptions about VPD. The behavior of VPD subjected to low levels of excitation is elastic while with increasing levels of excitation, a significant source of energy dissipation is provided through the yielding of the steel elements in addition to the viscoelastic energy dissipation. The results showed energy dissipation of 99.35 kN.m under a dynamic displacement with 14.095 mm amplitude and 0.333 Hz frequency. Lateral displacement at the middle of the device was created with an amplification factor obtained ranging from 2.108 to 3.242 in the rubber block. Therefore, the energy dissipation of viscoelastic material of VPD was calculated 18.6 times that of the ordinary viscoelastic damper.

• Design & Manufacturing
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• 제16권4호
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• pp.17-23
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• 2022

Recently, several studies are being conducted to achieve a curvature of 180° or more for the edge of the display glass. The thermocompression molding process is applied to the manufacture of curved glass, and high hardness G5 graphite is used as the mold material to withstand the impact applied to the mold. G5 graphite has high hardness and strong brittleness, which makes tool wear and surface damage easy during machining. Therefore, the demand for diamond-coated tools with good mechanical properties is increasing in the G5 machining field. In this study, the optimal cutting conditions and machinability of a nanodiamond (NCD) coated ball end mill being developed by a tool manufacturer were analyzed and evaluated. For this purpose, the same test was performed on the microdiamond (MCD) coated ball end mill and compared together. In summary, the machinability of MCD and NCD coated tools showed better cutting performance at a cutting speed of 282 m/min, a feed rate of 1,400 mm/min, and a radial depth of cut of 0.08 to 0.1 mm.

• Physical Therapy Rehabilitation Science
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• 제11권4호
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• pp.409-413
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• 2022

Objective: This study aims to compare the range of motion of the joints by applying the contraction and relaxation techniques used in manual therapy as electrical stimulation treatment. Based on this, we would like to propose the possibility of using motor nerve electrical stimulation therapy for musculoskeletal physical therapy. Design: Single-arm interventional study Methods: Active and passive straight leg raising tests were performed on 20 healthy men and women in their 20s to measure the angle of hip joint flexion. Then, the electrical stimulation time was set to 10 seconds and 5 seconds of rest, and motor nerve electrical stimulation of 1 Hz was applied with the maximum strength that could withstand the hamstring muscles for 10 minutes. After electrical stimulation, straight leg raising tests again to confirm the range of motion of the hip joint flexion. Results: As a result of this study, it was confirmed that the joint range of motion was significantly improved for both active and passive straight leg raising tests after application of motor nerve electrical stimulation(p<.05). Conclusions: With a strong electrical stimulation treatment of 1 Hz, the effect similar to the contraction and relaxation technique used in manual therapy was confirmed through the joint range of motion. In the future, motor nerve electrical stimulation therapy can be used for musculoskeletal physical therapy to provide a new approach for patients with reduced pain and joint range of motion due to muscle tension.