• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.967-968
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• 2013

• Bulletin of the Korean Mathematical Society
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• v.59 no.1
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• pp.45-72
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• 2022

In this work, we study Bernstein-Walsh-type estimations for the derivative of an arbitrary algebraic polynomial in regions with piecewise smooth boundary without cusps of the complex plane. Also, estimates are given on the whole complex plane.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.24 no.2
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• pp.83-93
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• 1988

Recent Experimental results show that the J integral can be effectively used to obtain a valid parameter for predicting plane strain and plane stress fracture. However, only a few research results have been reported for the effect of thickness where the plane strain state can not be assumed. A purpose of this study is to find the behavior of fracture touhness and tearing modulus varing the specimen thickness. The type of specimen in the present study is compact tension (CT). The thicknesses of the low carbon steel specimens that are used in the experiments are 5, 10, 15, 20 and 25mm. The measurement of crack length is taken by optical measurements method. From the study, the followings are found; 1) The fracture toughness and the tearing modulus which are obtained by using Yoon's and Simpson's formula show more conservative than that by using Rice's and Merkel's. 2) The fracture toughness is increase in specimen thickness which is reached 15mm. Beyond this thickness the fracture toughness is decreased in specimen thickness. 3) In the case of CT specimen with the thickness ranging from 5 to 25mm, the tearing modulus which is applied the same J integral equation is almost constant. 4) By using Yoon's formula, the correlation of the plane slress fracture toughness J sub(C) with specimen thickness B is expressed as the following formula. J sub(C)/J sub(IC)=1.7-15.1(B/W)+112.9(B/W) super(2) -301.3(B/W) super(3) +260.6(B/W) super(4)

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.451-459
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• 2009

The purpose of this study was to evaluate the in-plane bending moment for T-joints made of cold-formed square hollow steel sections. In the previous studies, the T-joint was shown not to have an obvious peak load, and the failure mode was the main chord flange failure at the branch-width-to-chord-width ratio ($\beta$) of below 0.71. Based on the experimental results, including the tests conducted by Zhao, the deformation limit of 1% B was proposed for ${16.7{\leq}2{\gamma}(=B/T){\leq}33}$ and ${0.34{\leq}{\beta}(=b_{1}/B){\leq}0.71}$. Then, the ultimate in-plane bending strength was shown to be Mu=1.5${\cdot}$M1% B. The existing strength formulae for the original T-joint were investigated and were determined to be the main chord flange failure for the branch-squared T-joint. The bending strength formulae of CIDECT and other researchers were compared with the test results. Finally, a reasonably good agreement with Zhao's formula was found. Therefore, the design guidelines were presented based on Zhao's strength formula for T-joints.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.43 no.3
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• pp.152-159
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• 2017

Objectives: The aim of this study was to investigate the effects of advancement magnitude and changes in mandibular plane angle on the stability of mandibular advancement. Materials and Methods: This retrospective cohort study evaluated the postoperative stability of mandibular advancement in class II skeletal subjects who underwent bilateral sagittal split osteotomy. Radiographs taken preoperatively, immediately postoperatively and 1 year postoperatively were traced and analyzed using linear and angular measurements. To determine horizontal and vertical relapse, an X-Y coordinate system was established in which the X-axis was constructed by rotating S-N downward by $7^{\circ}$ (approximation of the Frankfort horizontal plane) and the Y-axis was defined as a line perpendicular to the X-axis and passing through the point Sella. For certain reference points including point A, point B, pogonion and menton, the perpendicular distance between each point and both axes was determined and cephalometric variables were recorded as X and Y coordinates. Results: Twenty-five subjects were studied. A significant correlation between the amount of mandibular advancement and relapse in the B point (vertical and horizontal) and the pogonion point was observed (vertical and horizontal, P<0.001). Evaluation of data demonstrated a positive correlation between the mandibular plane angle (SN/ML) change and vertical relapse in the B point (P<0.05). A simple regression model demonstrated that 74% of horizontal relapse and 42.3% of vertical relapse in the B point was related to the amount of mandibular advancement. The receiver operating characteristic test showed that 8.5 mm mandibular advancement is related to a relapse rate of 1 mm or more in the pogonion, vertically or horizontally. Conclusion: The magnitude of mandibular advancement is a stronger surgical predictor for horizontal rather than vertical relapse at the B point. Changes in mandibular plane angle (SN/ML) during surgery affect vertical, but not horizontal relapse at the B point.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.684-690
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• 2009

In this paper, we proposed a new method of the steganography based on bit plane using similarity. Applying a fixed threshold, the insert information into all bit planes showed different image quality. Therefore, we first defined the bit plane of block similarity to solve the fixing threshold problem. We then proposed a new method using the Bit Plane complexity and similarity to insert information into bit planes of block. In the experiment, we inserted information into the standard images with the same image quality and same insertion capacity. Finally analyzed the insertion capacity and image quality. As a result, the proposed method increased the insertion capacity of about 6% and improved the image quality of about 3.3dB than fixing threshold method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.103-107
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• 2009

Because individual HRTFs (Head-Related Transfer Functions) vary from a person to a person, a HRTF database has been measured by researchers to investigate the inter-subject variation, and to generate high fidelity virtual sound image. Individual HRTFs not only vary between subjects but also vary due to wearing clothes and glasses in daily life. However, influence of different dressing condition on the measured HRTF was not sufficiently investigated. To quantify the effect of wearing clothes and glasses, dummy's HRTF is measured in an anechoic chamber with various dressing condition, and is evaluated in the sense of spectral distortion. HRTFs are measured both in the median plane and in the horizontal plane. In the median plane, under 6kHz, effect of different wearing clothes and glasses is negligible. Over 6kHz, however, effect of clothing distorts HRTF about 6dB in the sense of spectral distortion. Moreover, at high frequencies, effect of glasses is no longer negligible. In the horizontal plane, at some azimuths, even additional light cloth over the dummy can change the spectrum of HRTF (6dB spectral distortion) especially when sound source is at contralateral positions. Therefore, HRTF measurement with different wearing conditions can broaden the capability of HRTF customization whose technique utilizes a HRTF database.

• Journal of Magnetics
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• v.9 no.2
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• pp.40-46
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• 2004

The magnetic properties of sputtered ($Ni_{83}Fe_{17}/Au/Co/Au$) multilayers with various thicknesses of Au (0.5 {\leq} t_{Au} {\leq} 3 nm), Ni-Fe ($1{\leq}t_{Ni-Fe}{\leq}4nm$) and Co ($0.2{\leq}t_{co}{\leq}1.5nm$) layers were characterized. An alternating in-plane and out-of-plane anisotropy of the ferromagnetic layers was achieved for the structures ($t_{Au}{\geq}1.5nm$) showing a weak coupling between the Ni-Fe layers with an in-plane anisotropy and the Co layers ($0.3{\leq}t_Co{\leq}1.2nm$) with a perpendicular anisotropy. For such a structure, a detailed discussion on the GMR effect is presented, relating to the magnetization reversal from a mutually perpendicular magnetic configuration at the remanence to a parallel one at the saturation. An influence of the dense labyrinth domain structure on the magnetoresistance effect is also addressed.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.193-196
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• 2006

In this paper, two $4{\times}4$ rectangular patch array antennas operated at 20 GHz are implemented for the satellite communication. Two $2{\times}2$ sub-arrays are designed and used for the design of $4{\times}4$ patch array. The sixteen patch antennas and microstrip feeding line are printed on the single-layered substrate. The spacing between the array elements is chosen to be $0.736{\lambda}$. The HPBW(Half Power Beam Width) of the $4{\times}4$ microstrip patch array is 17.01 degrees in the E-plane and 17.71 degrees in the H-plane with a gain of 11.6dB in the experimental results. The HPBW of the recessed $4{\times}4$ microstrip patch array is 18.66 degrees in E-plane and 17.12 degrees in the H-plane with a gain of 12.55dB in the experimental results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.3
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• pp.302-310
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• 2003

Experiments were conducted to show the characteristics of the flow on unventilated parallel plane jets. Measurements of mean velocity components and turbulent intensities were carried out with a particle image velocimetry to investigate the flow field generated by the air issued from two identical plane parallel nozzles and mixed with the ambient air. The measurements range of these experiments were Reynolds number of 5300 based on the nozzle width and the cases of nozzle-to-nozzle distance were four times. six times and eight times the width of the nozzle. Results show that a recirculation zone with a sub-atmospheric static pressure was bounded by the inner shear layers of the individual jets and the nozzles plate. The positions. where maximum value of mean turbulent intensities and mean turbulent kinetic energy show, were at the same position with the merging point. The spread of jets in the merging region increases more rapidly than that of Jets in the converging and the combined region. As nozzle-to-nozzle distances were increased. it was shown that merging and combined lengths were shorter.