• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.147-150
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• 2002

A light guide panel is an element of the LCD backlight module that is often used for the display of compact electronic devices. In this study, a laser marking system is proposed to fabricate light guide panel, which can be replaced of other manufacturing methods such as silk printing, stamping, and v-cutting methods. The objectives of this research are the establishment of laser marking system, evaluation of laser marking parameters, understanding marking process, application to PMMA, reliability test and quality inspection. A 50W $CO_2$ laser (CW) was used to perform different experiments in which, the influence of some processing parameters (average power, scanning speed) on the geometry and quality of groove pattern was studied. The width of the etched grooves increases with increasing a laser power and decreasing a scan speed. In order to analyze surface characteristics and optical properties (luminance, uniformity), SEM photography and BM7 (luminance measuring system) were used. As a result, the optimal conditions of the process parameters were determined.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.353-361
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• 1989

A parametric study of load distribution in bolt-nut joints is performed by the method of finite element contact analysis. The contacting surface is assumed unbonded and frictionless. Multi-body contact analysis is performed in elastic region under the assumption of axi-symmetric stress state. Load acting on the first thread from the fastened plate is much greater than that on the other threads in the standard setting. But the load distribution is shown to be improved by making the center of contact force acting on the nut surface move outwards. Such a modification is possible by enlarging the gap between bolt shank and fastened plate or by inserting suitable washers. Shape modification of the standard nut by the making a groove and a step on the nut surface is also suggested, which results in almost uniform load distribution and considerable decrease in the maximum stress of the joint.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.6
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• pp.661-667
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• 2004

The control of tilt angle for nematic liquid crystal (NLC) with negative and positive dielectric anisotropy on the rubbed homeotropic polyimide (PI) using baking method by hot plate equipment was investigated. LC tilt angle decreased with increasing baking temperature and time. Especially, the low LC tilt angle of positive type NLC (Δ$\varepsilon$＞0) on the rubbed homeotropic PI surface by increasing temperature and time was measured. The tilt angle of positive type NLC(Δ$\varepsilon$＞0) is smaller than that of the negative type (Δ$\varepsilon$＞0) on rubbed PI with increasing baking temperature and time. We consider that the tilt angle of NLC is decreased due to increasing the steric interaction between horizon component of permittivity $\varepsilon$ = of NLC and the stress of polymer side chain by high temperature. As the increase of baking temperature, we obtain that AFM (atomic force microscope) image of rubbed PI surface using Hot-plate method has formed better solid micro-groove structure than oven method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.432-432
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• 2007

We studied optical simulation method for ultra slim backlight system. We designed 0.7mm thickness light guide plate and combined 48 white color LEDs for 12 inch wide size TFT-LCD. We designed flat shape PMMA light guide plate with both side patterned. It have vertical prism shape on upper side and ellipse dot pattern on the other side. We targeted 4500 nit brightness and uniform emission characteristic without hot spot or dark area. At first, we designed uniform emission area with more high brightness in center area and then, debugged light entering hot spot zone and direction of outgoing light flux. Although it was designing step, we obtained good result with reverse prism optical sheet and it had good repeatability because it was based on the stamper method in injection process without laser engraving or micro groove engraving method.

• Journal of Welding and Joining
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• v.25 no.1
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• pp.37-41
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• 2007

The purpose of this study is to establish the predictive method of angular distortion of the double-sided multi-pass butt weldment achieve it, the behavior of angular distortion in the butt weldment were investigated using comprehensive finite element analyses and experiments. The angular distortion in the multi-pass butt weldment strongly depends on the welding heat input(Q) and the effective bending rigidity of the weld throat. The effective bending rigidity of the first welding pass on the backing side was defined as the function of dimensionless parameter(k) and a bending rigidity of bead-on-plate weldment. Based on the results, the predictive equation for angular distortion of multi-pass butt weldment was proposed and verified by experiments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.267-271
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• 1993

Developed in this paper is a feature based modeling of welded plate construction(WPC) which is composed of flat or bended plates represented as reference plane with a constant thickness. First, the necessity and the characteristics of the feature based modeling of WPC as compared with the assemblies of mechanical parts are investigated. Second, feature library for the assemblied of WPC is shown which contains several types of features like joint feature, groove feature, materialfeature and precision feature. Third, the assembly procedures are presented whichmainly consist of both the assembly transformation and the correct assembly checking. Fourth, weld lines generated in the assembled WPC are defined so that those can be used in the process planning or the manufacturing stage. Finally, A prototype system isdeveloped by using a geometric modeling software Pro/Engineer, a graphic software GL(Graphic Library), and C language on a CAD workstation IRIS.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.3
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• pp.3872-3877
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• 1975

This study was conducted to examine the effects of the change of cap hole diameter and pressure on the travelling distance and the sprayed particle size for the medium range nozzle. The results of this study are summarized as follows; 1) The effective travelling distance was about from 1 meter to 8 meters and centro-position of the travelling distance was about 3 or 5 meters. 2) Main effect of change of cap hole diameter for the travelling distance was a slight convex quadratic curve. 3) Main effect of change of pressure increased linearly, its increasing rate about 1.6 was large. 4) Sizes of sprayed particles were less than 250${\mu}$ generally and the sizes decreased according to the increasing of travelling distance. 5) Changes of diameter of sprayed particles by cap hole diameter increased in accordance with increasing of cap hole diameter. 6) Changes of diameter of sprayed particles by the groove depth of swirl plate was very slight.

• Parasites, Hosts and Diseases
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• v.52 no.6
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• pp.685-690
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• 2014

A perianal tick and the surrounding skin were surgically excised from a 73-year-old man residing in a southwestern costal area of the Korean Peninsula. Microscopically a deep penetrating lesion was formed beneath the attachment site. Dense and mixed inflammatory cell infiltrations occurred in the dermis and subcutaneous tissues around the feeding lesion. Amorphous eosinophilic cement was abundant in the center of the lesion. The tick had Y-shaped anal groove, long mouthparts, ornate scutum, comma-shaped spiracular plate, distinct eyes, and fastoons. It was morphologically identified as a fully engorged female Amblyomma testudinarium. This is the third human case of Amblyomma tick infection in Korea.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.283-288
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• 1999

The sealing performance of an elastomeric O-ring seat with a temperature gradient has been analyzed for the contact stress behaviors that develop between the O-ring seal and the surfaces with which it comes into contact. The leakage of an O-ring seal will occur when the pressure differential across the seal just exceeds the initial (or static) peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of restrained geometry (grooved), are investigated using the finite element method. The analysis includes material hyperelasticity and axisymmetry. The computed FEM results show that the contact stress behaviors are related to a compression rate and a temperature gradient between the vacuum chamber with a groove and the contacting plate with a cooling jacket.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.267-272
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• 1995

The paper describes an approach for measuring flow ripple generated by oil hydraulic axial piston pumps. Flow ripple has periodic waveforms due to the cyclic nature of a pump's operation, and interacts with the connected hydraulic systems such as pipes and components to produce a pressure ripple, also known as fluid-borne noise. It is indispensable to measure a flow ripple because increasing of vibration and noise caused by a flow ripple has become a point to be considered and has need of solving these problems. The measurement of flow ripple with high frequencies from oil hydraulic axial piston pumps is msde by using the remote instantaneous flow rate measurement method. As a result, the reverse flow through the relief groove in valve plate has an important effect upon a flow ripple generated by a pumps.