• Journal of Korean Ophthalmic Optics Society
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• v.7 no.2
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• pp.181-187
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• 2002

Curvature of Crystalline lens changes by Accommdation's change. When Accommdation gives force vertically to Crystalline lens that is elastic body, length increases for vertex direction. Density distribution and form of Crystalline lens that receive force lean to posterior surface, horizontal force of anterior surface direction is bigger more than horizontal force of posterior surface direction. But, if Accommdation begins to grow more than threshold value, expansity reaches in limit on anterior surface. This time, horizontal force of posterior surface direction is great mored more than horizontal force of anterior surface direction, thickness of posterior surface direction increases because is more than anterior surface direction. Anterior and posterior relationship thickness change difference accomplish the 2-nd funtional line(${\Delta}=B_1D+B_2D^2$) about Accommdation. Thickness (${\Delta}t_a$, ${\Delta}t_p$) difference change curved line of anterior pole-border and border-posterior pole by Accommdation is expressed as following. $${\Delta}t_a=t_a-t_{ao}=t_{max}+t_0{\exp}(-A/B)-t_{ao}$$ $${\Delta}t_p=t_p-t_{po}=t_{min}+t_0{\exp}(A/B)-t_{po}$$ The Parameter value that save in human's Crystalline lens obtain $t_{min}=1.1.06$, $t_0=-0.33$, B=9.32 in anterior, and $t_{max}=1.97$, $t_0=0.10$, B=7.96 etc. in posterior. Vertex curvature radius' change is as following Crystalline lens' anterior and posterior by Accommation $$R=R_0+R_1{\exp}(D/k)$$ The Parameter value that save in human's Crystalline lens obtain $R_{min}=5.55$, $R_1=6.87$, k=4.65 in anterior, and $R_{max}=-68.6$, $R_1=76.7$, k=308.5 in posterior, respectively.

• The Journal of the Acoustical Society of Korea
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• v.30 no.4
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• pp.215-222
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• 2011

In order to obtain high resolution images, a focusing ultrasonic transducer operated in very high frequency (VHF) range was fabricated and its characteristics were evaluated. A 9-${\mu}m$ thick PVDF film with only one metalized surface for electric ground was adhered to a CCP (Copper-clad polyimide) film by using epoxy. It was pressed by a metal ball to form a concave surface and its rear side was filled with the epoxy. The radius of curvature and the f-number of the fabricated transducer are 7.5 mm and 1.7, respectively. The pulse-echo measurement results from a target located at the focal point showed that the frequency bandwidth was 35.0 MHz and the insertion loss near the peak frequency of approximately 40 MHz was about 60 dB. Those values agreed well with the simulation results by the KLM equivalent circuit analysis including the effect of the epoxy bonding layer. When the image of thin copper lines by the 35 MHz transducer of the UBM (Ultrasonic Backscattering Microscope) system was compared with the image by the transducer fabricated in this study, the fabricated transducer was observed that the axial resolution was improved although the lateral resolution was degraded.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.1
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• pp.35-40
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• 2018

Nd:YAG laser was used to carbonize polyimide films to produce carbon films. This is a simple manufacturing process to fabricate low cost sensors. By applying this method, we studied characteristics of flexible and low-cost piezoresistive. Previously, many studies focused on carbonization of polyimide using $CO_2$ laser with wavelength of $10.6{\mu}m$. In this paper, carbonization (carbonization process) was performed on polyimide films using an Nd:YAG laser with a wavelength of $1.064{\mu}m$. In order to increase the resolution, we optimized the laser conditions of the power density ($W/cm^2$) and the beam scan rate. In previous studies using $CO_2$ laser, the minimum line width was $140{\sim}220{\mu}m$ but in this study, carbon line width was reduced to $35{\sim}40{\mu}m$. The initial sheet resistance of the carbon sensor was $100{\sim}300{\Omega}/{\square}$. The resistance decreased by 30% under stretched with a curvature radius of 21 R. The calculated gauge factor was 56.6. This work offers a simple, highly flexible, and low-cost process to fabricate piezoresistive sensors.

• Applied Microscopy
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• v.24 no.3
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• pp.1-9
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• 1994

Pardosa astrigera possessed eight eyes arranged in three rows on the frontal carapace. A pair of small anterior lateral eyes (ALE) flanked each side by an anterior median eyes (AME) lay along the anterior margin that was situated on the anterior row of clypeus. The anterior lateral eye was composed of cornea, vitreous body, and retina. Cornea was made up mainly of exocuticle lining the cuticle. Lens in anterior lateral eye was biconvex type which bulged into the cavity of the eyecup. Outer and inner central region of lens were approximately spherical with radius of curvature $5.6{\mu}m$ and $12.5{\mu}m$, respectly. Vitreous body formed a layer between the cuticular lens and retina. They formed biconcave shape. Retina of the anterior lateral eyes was composed of three types of cells: visual cells, glia cells, and pigment cells. The visual cells were unipolar neuron, as were the receptor of the posterior lateral eye. But cell body was unique to the anterior lateral eyes. They were giant cell, relatively a few in number, and under the layer of vitreous bodies. Each visual cell healed rhabdomeres for a short stretch beneath the cell body. Rhabdomes were irregulary pattern in retina and electron dense pigment granules scattered between the rhabdomes. Glia cell situated at the cell body of visual cell and glia cell process reached to rhabdomere portion. Below the rhabdome, tapetum were about $30{\mu}m$ distance from lens, which composed of 4-5 layers. It was about $25{\mu}m$ length that intermediate segment of distal portion of visual cell. Electron dense pigment granules between the intermediate segment were observed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1309-1315
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• 2014

The switch for a maglev vehicle should be designed such that the vehicle safely changes its track without touching the guiderail. In particular, a medium-to-low-speed EMS -type maglev train relies heavily on a U-type electromagnet where it generates levitation force and guidance force simultaneously. Therefore, it is necessary to evaluate the safety of the vehicle whenever it passes the switch, as it lacks active control of the guidance force. Furthermore, when the vehicle passes a segmented switch, which is a group of curves made up of connected lines with a small radius of curvature, it may come into mechanical contact with the guiderail owing to the excessive lateral displacement of the electromagnet. The goal of this study is to analyze the influence of a segmented switch on the safety of major design-related variables for achieving improved running safety. We propose a three-dimensional multibody dynamics model composed of two cars with one body. Using the proposed model, we perform a simulation of the lateral air gap, which is one of the measurements of the running safety of the vehicle when it passes the switch. The analyzed design variables are the length between short span girder, the articulation angle, the length between two centers of a fixed girder at its ends, and the number of girders. On the basis of the effects of the considered design variables, we establish an optimized design of a switch with improved safety.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.559-573
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• 2007

Orthotropic steel decks are manufactured by welding thin plates therefore it is inevitable that there are abundant works of welding process. On connection of transverse rib web, crossing point of longitudinal rib, transverse rib and deck plate and cut-out parts of transverse rib are the significant position of stress concentration because of out of plane and oil-canning deformation caused by longitudinal rib distortion with shear force and distortion. At the current research, the crossing point where the orthotropic steel decks's effect of improving fatigue performance are high, not placing scallop and diaphragm which have same plane with transverse rib placed inside of longitudinal rib at the same time, the reduce effects of stress concentration at the cut-out section and the crossing are high. Especially the installation of the diaphragm causing great effects based on research results to stress concentration appearance reduce effects at the cut-out section, putting radius of curvature of the diaphragm's top and bottom as a target, as a result of carrying out the parametric analysis an optimal diaphragm form that has great effects in fatigue performance came to a conclusion. Also based on optimal diaphragm form, an advantage of the diaphragm optimal setting position for improvement of the fatigue performance came to a conclusion.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.477-483
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• 2015

Investigations into cavity flows have been conducted for noise and vibration problems that arise in cavity systems. Cavity systems have been applied in engineering devices and have undergone rapid development in the aerospace industry. Meanwhile, to the author's best knowledge, the cavity on a curved wall has been seldom studied. The present work is conducted to study the flow physics of a cavity mounted on a curved wall. Numerical analysis is performed to investigate the cavity flow. Two variables of sub- and supersonic cavity flows were considered: the radius of curvature of the curved wall (L/R) and the inlet Mach number. The results show that the uniform vortex generated by the cavity flow on the curved wall stabilize the pressure fluctuation as time passes. As the inlet Mach number increases, the pressure fluctuation amplitude increases. The results obtained from the curved wall are compared with those from a straight wall using Rossiter's formula. The Strouhal number of the curved wall is lower than that of the straight wall. Lower Strouhal numbers have been obtained in the present computational fluid dynamics (CFD) results than in the theoretical results using Rossiter's formula.

• Current Photovoltaic Research
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• v.4 no.3
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• pp.108-113
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• 2016

III-V compound semiconductor based thin film solar cells promise relatively higher power conversion efficiencies and better device reliability. In general, the thin film III-V solar cells are fabricated by an epitaxial lift-off process, which requires an $Al_xGa_{1-x}As$ ($x{\geq}0.8$) sacrificial layer and an inverted solar cell structure. However, the device performance of the inversely grown solar cell could be degraded due to the different internal diffusion conditions. In this study, InGaP/GaAs double-junction solar cells are inversely grown by MOCVD on GaAs (100) substrates. The thickness of the GaAs base layer is reduced to minimize the thermal budget during the growth. A wide band gap p-AlGaAs/n-InGaP tunnel junction structure is employed to connect the two subcells with minimal electrical loss. The solar cell structures are transferred on to thin metal films formed by Au electroplating. An AlAs layer with a thickness of 20 nm is used as a sacrificial layer, which is removed by a HF:Acetone (1:1) solution during the epitaxial lift-off process. As a result, the flexible InGaP/GaAs solar cell was fabricated successfully with an efficiency of 27.79% under AM1.5G illumination. The efficiency was kept at almost the same value after bending tests of 1,000 cycles with a radius of curvature of 10 mm.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.417-428
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• 2004

We have investigated the optical property of the KAO(Korea Astronomy Observatory) wide field telescope (named NEOPAT-3; Near Earth Object and Satellite Patrol-3) and aligned optical system. The NEOPAT-3 is restricted to V,R,I-filters because of the refractive property of the correcting lens system. Because of the fast focal ratio, the optical performance of the NEOPAT-3 is very sensitive to its alignment factors of the optical system. To make the spot radius smaller than $8{\mu}m$ in rms over 2degree${\times}2$degree field, the optical system must satisfy the following conditions: 1) The tilt error between detector plane and focal plane should be less than 0.05degree. 2) The decenter error between the primary mirror and the correcting lens system should be less than 1mm. 3) The distance error between the primary mirror and the correcting lens system should be less than 2.3mm. In order to align the optical system accurately, we measured the aberrations of the telescope quantitatively by means of curvature sensing technique. NEOPAT-3 is installed temporary on the roof of the TRAO(Taeduk Radio Astronomy Observatory) main building to normalize system performance and to develop automatic observation.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.3
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• pp.235-240
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• 2010

Purpose: In this study, we proposed a simple accommodation-dependent crystalline lens with a constant volume and homogeneous refractive index. Methods: We proposed a human crystalline lens with two aspheric surfaces. Two surfaces intersect in two points and straight line between two points was equator(2b). It assumed that the derivative in axial direction was zero at the equator and the radial derivative was zero at the vertex. Proposed human crystalline lens was divided by the equator into the anterior and posterior parts. It was assume that the volume of each part and refractive index of the human crystalline lens were constant during accommodation. Results: For the changes during accommodation, geometrical parameters were determined by different objective distances. Considering the constant volume of each part with the small decrement of the equator, we obtained the paraxial parameters, such as the anterior and posterior vertex radius of curvature and lens thickness. Compared with the experimental data published in the literature, calculated values using simple approximation showed similar change per accommodative stimulus. Conclusions: These results showed that proposed simple approximation using assumption of constant volume and refractive index of the human crystalline lens made it possible to predict changes of geometrical parameters during accommodation.