• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.388-388
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• 2011

Graphene, with its unique physical and structural properties, has recently become a proving ground for various physical phenomena, and is a promising candidate for a variety of electronic device and flexible display applications. The physical properties of graphene depend directly on the thickness. These properties lead to the possibility of its application in high-performance transparent conducting films (TCFs). Compared to indium tin oxide (ITO) electrodes, which have a typical sheet resistance of ~60 ${\Omega}/sq$ and ~85% transmittance in the visible range, the chemical vapor deposition (CVD) synthesized graphene electrodes have a higher transmittance in the visible to IR region and are more robust under bending. Nevertheless, the lowest sheet resistance of the currently available CVD graphene electrodes is higher than that of ITO. Here, we report an ingenious strategy, irradiation of MeV electron beam (e-beam) at room temperature under ambient condition,for obtaining size-homogeneous gold nanoparticle decorated on graphene. The nano-particlization promoted by MeV e-beam irradiation was investigated by transmission electron microscopy, electron energy loss spectroscopy elemental mapping, and energy dispersive X-ray spectroscopy. These results clearly revealed that gold nanoparticle with 10~15 nm in mean size were decorated along the surface of the graphene after 1.0 MeV-e-beam irradiation. The fabrication high-performance TCF with optimized doping condition showed a sheet resistance of ~150 ${\Omega}/sq$ at 94% transmittance. A chemical transformation and charge transfer for the metal gold nanoparticle were systematically explored by X-ray photoelectron spectroscopy and Raman spectroscopy. This approach advances the numerous applications of graphene films as transparent conducting electrodes.

• Korean Journal of Optics and Photonics
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• 제17권5호
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• pp.447-454
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• 2006

We obtained analytic solutions of boundary conditions to the stable region of Z-fold $Cr^{4+}$ : YAG laser cavity when the conditions are with and without thermal tensing effect. Also we investigated the influence of the thermal tensing effect on the stability of cavity, beam waist, and astigmatic compensation using aberration transformation matrices. The thermal tensing effect almost has no influence on the stable region of the cavity when the crystal is located in the middle of two concave mirrors and when the distances from the concave mirror to the reflecting mirror and the output coupler are the same. The beam waist, however, is affected more in a tangential plane than in a sagittal plane, and so it is difficult to have astigmatic compensation when the thermal tensing effect exists. This result means that the thermal tensing effect should be considered even for the Kerr-lens mode-locking.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• 제7권2호
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• pp.81-90
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• 1998

Noise produced by surface transportation vehicles affects our daily lives, penetrating wherver man lives or works. In this paper, a theoretical model has been studied to describe the sound radiation by the surface vibration of in-service tires and studied about an experiment on sound radiation characteristic due to tire vibration. When a tire is analyzed, it has been modeled as a curved beams with distributed sprongs and dash-pots which represent the radial, tangential stiffnes and damping of tire, respectively. The experimental investigation for the sound radiation of a radial tire has been made. Based on the sound intensity and STSF(Spatial Transformation of Sound Field) techniques. the sound pressure and the sound radiation are measured. The comparison of numerically analyzed results with experimental results was made seperately for the tire in rotation. As a result of this study, a program for the prediction of the tire vibration sound radiation was intended to by developed which enables a designer of a tire to foresee the influence of the various design factors on the tire vibration sound radiation.

• Smart Structures and Systems
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• 제28권6호
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• pp.827-838
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• 2021

The dynamic displacement is considered to be an important indicator of structural safety, and becomes an indispensable part of Structural Health Monitoring (SHM) system for high-speed railway bridges. This paper proposes an indirect strain based dynamic displacement reconstruction methodology for high-speed railway box girders. For the typical box girders under eccentric train load, the plane section assumption and elementary beam theory is no longer applicable due to the bend-torsion coupling effects. The monitored strain was decoupled into bend and torsion induced strain, pre-trained multi-output support vector regression (M-SVR) model was employed for such decoupling process considering the sensor layout cost and reconstruction accuracy. The decoupled strained based displacement could be reconstructed respectively using box girder plate element analysis and mode superposition principle. For the transformation modal matrix has a significant impact on the reconstructed displacement accuracy, the modal order would be optimized using particle swarm algorithm (PSO), aiming to minimize the ill conditioned degree of transformation modal matrix and the displacement reconstruction error. Numerical simulation and dynamic load testing results show that the reconstructed displacement was in good agreement with the simulated or measured results, which verifies the validity and accuracy of the algorithm proposed in this paper.

• Asian Pacific Journal of Cancer Prevention
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• 제15권18호
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• pp.7757-7761
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• 2014

Aim: To report long term outcomes of laser conization for high grade cervical intraepithelial neoplasia (CIN) in Thai women. Materials and Methods: A retrospective cohort study was conducted in patients undergoing laser conization due to abnormal cervical cytology suggesting neoplasia during 1989 to 1994 and having follow-up data until December 2010. Conization was performed under colposcopy using a 0.5-mm $CO_2$ laser beam with power density of $18,000-20,000watts/cm^2$, and the surgical base was vaporized using a low power defocused beam. The follow-up protocol included cervical cytology and colposcopy. Long term outcome measures were failure rate (persistence and recurrence), post-conization status of transformation zone, and obstetric outcomes. Results: Of 104 patients undergoing conization, 71 had therapeutic conization for high grade CIN and were followed up for a median time of 115 (range 12-260) months. There was one case of persistent and one of recurrent disease comprising a failure rate of 2.8%. The post treatment transformation zone was well visualized in 68.3% of 63 patients with an intact uterus. Sixteen patients achieved 25 pregnancies; none had second trimester miscarriage. The obstetric outcomes were unremarkable. Conclusions: Laser conization under colposcopic visualization for the treatment of high grade CIN in Thai women has a low failure rate of 2.8%. The post-conization transformation zone could not be evaluated completely in approximately 30% of cases; therefore the follow-up protocol should include both cytology and colposcopy. Obstetric outcomes are not adversely affected by this therapeutic procedure.

• Journal of the Korean Wood Science and Technology
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• 제37권1호
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• pp.1-11
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• 2009

Although the exterior wood such as column may frequently contact with liquid water, little work has been found to measure liquid water absorption in wood. To investigate the moisture diffusivity of wood in the longitudinal direction including bound water and free water movement, liquid water absorption test was conducted at the room temperature. The order of magnitude for absorption coefficient and diffusivity was Japanese elm, horn beam, hemlock, spruce, radiata pine, and painted maple. The Boltzmann transformation method was used to determine the diffusivity from measured moisture content distributions in the absorption test. The shape of the curve representing the dependence of diffusivity with moisture content was similar in test samples. The diffusivity decreased with increasing moisture content until around the fiber saturation point and then increased at the nonhygroscopic region, which ranged from $10^{-10}$ to $10^{-7}m^2/s$.

• Journal of the Korea Concrete Institute
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• 제13권2호
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• pp.130-138
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• 2001

This paper presents on the shear behavior prediction of reinforced concrete beams using Transformation Angle Truss Model (TATM). The TATM can evaluate the stress-strain relationships for cracked concrete by transforming stresses and strains for principal plane into those over the crack surfaces. This proposed analytical method simplifies the Fixed Angle Softened Truss Model (FA-STM) and removes the limitation of applicability of the FA-STM. The shear.strength and strain of reinforced concrete beams are predicted by using the TATM. For the verification of proposed method, experimental results of reinforced concrete beams were compared with theoretical results by the TATM, FA-STM and Rotating Angle Softened Truss Model (RA-STM).

• Advances in nano research
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• 제15권4호
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• pp.339-353
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• 2023

This work aims to present a solution for the buckling behavior of perforated nano/microbeams with deformable boundary conditions using nonlocal strain gradient theory (NLSGT). For the first time, a solution that can provide buckling loads based on the non-local and strain gradient effects of perforated nanostructures on an elastic foundation, while taking into account both deformable and rigid boundary conditions. Stokes' transformation and Fourier series are used to realize this aim and determine the buckling loads under various boundary conditions. We employ the NLSGT to account for size-dependent effects and utilize the Winkler model to formulate the elastic foundation. The buckling behavior of the perforated nano/microbeams restrained with lateral springs at both ends is studied for various parameters such as the number of holes, the length and filling ratio of the perforated beam, the internal length, the nonlocal parameter and the dimensionless foundation parameter. Our results indicate that the number of holes and filling ratio significantly affect the buckling response of perforated nano/microbeams. Increasing the filling ratio increases buckling loads, while increasing the number of holes decreases buckling loads. The effects of the non-local and internal length parameters on the buckling behavior of the perforated nano/microbeams are also discussed. These material length parameters have opposite effects on the variation of buckling loads. This study presents an effective eigenvalue solution based on Stokes' transformation and Fourier series of the restrained nano/microbeams under the effects of elastic medium, perforation parameters, deformable boundaries and nonlocal strain gradient elasticity for the first time.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1130-1139
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• 2001

Springs are widely utilized in machine element. To find out stiffness of coil spring, the space beam theory using the finite element method is adopted in this paper. In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculated the another increments of nodal displacements, that is, the step by step method is used in this paper. The results of the finite element method are fairly well agreed with those of various experiments. Using MATLAB program developed in this paper, spring constants can be predicted by input of few factors.

• Journal of Advanced Marine Engineering and Technology
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• 제32권2호
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• pp.250-255
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• 2008

Springs are widely utilized in machine element. To find out stiffness of frustum-shaped coil spring, the space beam theory using the finite element method is adopted in this paper. In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. To find out load vector of coil spring subjected to distributed compression. principle of virtual work is adapted. And this theory was programming using MATLAB software. To compare FEM using MATLAB software was applied MSC. Nastran software. The geometry model for MSC. Patran was produced by 3-D design modeling software. Finite element model was produced by MSC. Patran. Finite element was applied tetra (CTETRA) having 10 node. The analysis results of the MATLAB and MSC. Nastran are fairly well agreed with those of various experiments. Using MATLAB program proposed in this paper and MSC. Nastran, spring constants and stresses can be predicted by input of few factors.