• Journal of the Korean Society for Precision Engineering
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• v.28 no.7
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• pp.761-768
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• 2011

The large surface micro machining system includes the equipments and processes for manufacturing the ultra precision micro patterned products with large surface through the mechanical machining. Recent major issue on the micro machining technology may be the development of optical parts for the back light unit of display which has the largest market. This special issue makes up with three parts; the large surface micro machining system and machine, machining process and forming process. In this paper, the state-of-the-art and core technology of large surface micro machining system is introduced with focus on the manufacturing technology for the back light unit of LCD TV. Then, some research results on the development of a roll die lathe is introduced which involves the concept of machine design, improvement of thermal characteristics in the spindle system, improvement of relative parallelism and straightness between spindle system and long stroke feed table, machining of micro pitch patterns. Finally, the direct forming process is introduced as the future work in the large surface micro machining field.

• The Plant Pathology Journal
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• v.24 no.2
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• pp.112-117
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• 2008

Pre-infection behavior of Fusarium circinatum on stems of pine species was investigated with scanning electron microscopy. Two-year-old stems of Pinus densiflora and p. rigida were inoculated with the fungal conidial suspension and subjected to $25^{\circ}C$ for up to 16 hr. Most microconidia germinated 12 hr after inoculation on pine stems. Conidia produced germ tubes from either one or both ends of microconidia. Germ tubes grew over the stem surface and appeared to enter host tissues through natural openings on pine stems. Surface cracks in the cork were entrance sites of germ tubes of F. circinatum. In addition, host cell wall cracks were often found at the tip of germ tubes. The cuticle appeared to be eroded either at the tip of germ tubes or around germlings. Germ tubes also produced appressoria-like structures, exhibiting swollen tips of germ tubes on the stem surface. There seems to be no significant differences in the pre-infection behavior of F. circinatum on stems between the two pine species.

• Journal of Biomedical Engineering Research
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• v.29 no.2
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• pp.107-113
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• 2008

We introduce a rotating-gantry-based x-ray micro-tomography system to be used for small animal imaging studies. It has the zoom-in imaging capability for high resolution imaging of a local region inside the animal subject without any contrast anomalies arising from truncation of the projection data. With the sliding mechanism mounted on the rotating gantry holding the x-ray source and the x-ray detector, we can control the magnification ratio of the x-ray projection data. By combining the projection data from the large field of view (FOV) scan of the whole animal subject and the projection data from the small FOV scan of the region of interest, we can obtain artifact-free zoomed-in images of the region of interest. For the acquisition of x-ray projection data, we use a $1248{\times}1248$ flat-panel x-ray detector with the pixel pitch of 100 mm. It has been experimentally found that the developed system has the spatial resolution of up to 121p/mm when the highest magnification ratio of 5:1 is applied to the zoom-in imaging. We present some in vivo rat femur images to demonstrate utility of the developed system for small animal imaging.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.1
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• pp.23-33
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• 2001

In this paper we propose a multi-codebook structure which can synthesize high quality speech without increasing of CELP coder's computation. We also design a 4.8kbps CELP speech coder with the proposed codebook structure. The proposed multi-codebook structure is made up of basic codebook and the other codebook which Is formed for strengthen spectrum an4 pitch. Multi-codebook structure can represent accurate gains since it represents excitation signals as summation of two kinds of codebooks and uses different codebook gains respectively. Therefore it can provide better speech quality than other conventional structures. In computer simulation of the 4.8kpbs CELP coder designed with the proposed codebook structure its segSNR was 0.81dB more high than the DoD CELP coder of same transmission rates.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.1
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• pp.39-48
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• 2011

This study describes a range sensitivity of a canard controlled missile. An investigation was conducted into the relative importance of aerodynamic parameters on a guided missile. Also this study was analyzed by quantifying their effects on the missile range. To analyze the range sensitivity of a guided missile, a trajectory analysis program of a guided missile was developed. The range sensitivity analysis was conducted on a thrust, weight, drag and lift. The result of the range sensitivity analysis shows that the design parameters with the greatest effect on the missile range are thrust, drag, weight, and lift, in descending order of importance. The thrust on range extension is quite obvious to extend a range of a guided missile. In particular, the drag exhibited greater range sensitivity than lift at a guided flight. The result also shows that missile range could be maximized by applying the appropriate launch angle and canard pitch-up control.

• Journal of Ocean Engineering and Technology
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• v.22 no.4
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• pp.84-89
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• 2008

It is hard to find experimental data for a model test of small high-speed planning boats. It is difficult to verify the performance seen in a model test for a high-speed boat because the ship-model scale-ratio is very small and the flow velocity of the circulating water channel and the X-carriage speed of the towing tank are restricted. Therefore most hull-form designs for high-speed small boats depend on the sea-trial test result for similar boats or evaluation through numerical calculations. This study investigated the anti-rolling effect of the stern sub-body in a 50-knot doss planning boat. To carry out this work, new model test procedures were set up in the actual sea. Using this method, the anti-rolling effect of the stern sub-body was investigated. A stern sub-body attached to a planning boat was proved to be effective in reducing the roll and pitch angle.

• Speech Sciences
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• v.7 no.2
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• pp.19-35
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• 2000

Speech evaluation and treatment planning for the patients with articulation disorders have traditionally been based on perceptual judgement by speech pathologists. Recently, various computerized speech analysis systems have been developed and commonly used in clinical settings to obtain the objective and quantitative data and specific treatment strategies. 10 dysarthric children (6 neurogenic and 4 functional dysarthria) participated in this experiment. Speech evaluation of dysarthria was performed in two ways; first, the acoustic analysis by Visi-Pitch and a Computerized Speech Lab and second, the perceptual scoring of phonetic errors rates in 100 word test. The results of the initial evaluation served as primary guidlines for the indivisualized treatment planning of each patient's speech problems. After mean treatment period of 5 months, the follow-up data of both dysarthric groups showed increased maximum phonation time, increased alternative motion rate and decreased occurrence of articulatory deviation. The changes of acoustic data and therapeutic effects were more prominent in children with dysarthria due to neurologic causes than with functional dysarthria. Three cases including their pre- and post treatment data were illustrated in detail.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.530-541
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• 1998

Heat transfer augmentation in a rib-roughened duct is affected by the rib configurations, such as rib height, angle of attack, shape, rib to rib pitch, and aspect ratio of a duct. These have been the main subjects in studying the average heat transfer and the friction loss of the fully developed flow. Investigating distributions of local heat transfer coefficients and flow patterns in a duct with the rib turbulators is necessary to find the characteristics of heat transfer augmentation and to decide the optimal configurations of ribs. In the present study the numerical analyses and the mass transfer experiments are performed to understand the flow through a rib roughened duct and the heat transfer characteristics with various angles of attack of ribs. A pair of counter-rotating secondary flow in a duct has a main effect on the lateral distributions of local mass transfer coefficients. Downwash of the rotating secondary flow, reattachment of main flow between ribs and the vortices near ribs and wall enhanced the mass transfer locally up to 8 times of that in case of the duct without ribs.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.260-267
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• 2001

The objective of this study was to investigate the characteristics of jet flow and heat transfer caused by trapezoid rods array in impinging jet system. In this study, trapezoid rods have been set up in front of flat plate to serve as a turbulence promoter. The bottom width of trapezoid rod was W=4, 8mm and oblique angle were $80^{\circ}$. The space from rods to the heating surface was C=1, 2, 4mm, the pitch between each rods was P=30, 40, 50mm, and the distance from nozzle exit to flat plate was H=100, 500mm. This results were compared with the case without trapezoid rods. As a result, when rods are installed in front of the impinging plate, the acceleration of the jet flow and the eddies due to the rods seem to contribute to the heat transfer enhancement. Among test conditions, the heat transfer performance was best for the condition of W=8mm, C=1mm, P=30mm and H/B=10. The maximum heat transfer rate is about 1.9 times larger than that without trapezoid rods.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.3
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• pp.252-261
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• 2016

A spar-type floating substructure that is being widely used for offshore wind power generation is vulnerable to resonance in the heave direction because of its small water plane area. For this reason, the stable dynamic response of this floating structure should be ensured by accurately identifying the resonance characteristics. The purpose of this study is to analyze the characteristics of the combination resonance between the excitation frequency of a regular wave and natural frequencies of the floating substructure. First, the nonlinear equations of motion with two degrees of freedom are derived by assuming that the floating substructure is a rigid body, where the heaving motion and pitching motions are coupled. Moreover, to identify the characteristics of the combination resonance, the nonlinear term in the nonlinear equations is approximated up to the second order using the Taylor series expansion. Furthermore, the validity of the approximate model is confirmed through a comparison with the results of a numerical analysis which is made by applying the commercial software ANSYS AQWA to the full model. The result indicates that the combination resonance occurs at the frequencies of ${\omega}{\pm}{\omega}_5$ and $2{\omega}_{n5}$ between the excitation frequency (${\omega}$) of a regular wave and the natural frequency of the pitching motion (${\omega}_{n5}$) of the floating substructure.