• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.2
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• pp.6-12
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• 1985

In this paper, self tuning control algorithm based on least square method is applied to the speed control of D.C. motor using Z-80 microprocessor as control unit. And the performance of algorithm is analyzed when the correlated noises of variance 20 and 80 are applied respectively. The convergence speed is measured and tracking is verified for the step and staircase wave reference input. Also it is shown that self tuning control algorithm is more attractive to the D.C. Totor speed control system regardless of power supply voltage and friction load changes than linear feedback control method which doesn't estimate parameters.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.10
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• pp.90-97
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• 1996

A numerical method for scattering of electromagnetic waves from a periodic strip grating over a grounded dielectric slab is considered for TE and TM polarization cases from the viewpoints of both reflection grating problem and leaky wave antenna problem. The analysis is based on a mode expansion method, floquet's theorem, and the method of moments. Numerical results involving some combinations of geometric parameters are presented in terms of complex propagation constant (kd-$\beta$d diagram), radiation pattern, and relative scattered powers of spectral modes. In particular, the relationship between complex propagatio constnat form the viewpoint of leaky wqve antenna problem and Off-bragg and bragg blazing phenomena from the viewpoint of reflecton graing problem is investigated.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.5
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• pp.1-6
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• 1997

An analysis method for the electromagnetic scattering of a tE polarized plane wave from a periodic strip grating over a grounded dielectric slab is consisered from the viewpoint of reflectio ngraing problem. The strip gratings showing bragg and off-bragg balzing phenomena at the frequency of 10GHz are designed, respectively. The strip grating structure is implemented using aluminum plate (hround conductor), paraffin(dielectric material ; .xi.$_{\gamma}$=2.24) and copper (strip conductor ; 0.08mm thickness). The experimental results (reflection power) for bragg as well as off-bragg blazing phenomenon have been compared with the theoretical results and fairly good agreements between theory and experiment have been observed.ed.

• Journal of the Ergonomics Society of Korea
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• v.9 no.2
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• pp.29-35
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• 1990

To investigate and analyze of the human brain-wave changes during 3-dimenslonal image load were expected to take not only an important basic information of 3-dimensional TV usage but also 3-dimensional image design. In this experiment, to analyze the difference of visual analyze handing system for which we present the 2- dimensional image having no parallex and 3-dimensional image by visual evoked potentials(VEP). 2-dimensional image and 3-dimensional image displayed on the screen through video. In the test, the time interval was one sec for presentation of stimulus considering united time of visual information of right eye and left eye during watching the 3-dimensional image also display time interval was 200 mesc for each stimulus image. Results are as follow, (1) N190 appears faster 16msec-20msec in the point of Fz, Cz, Pz, Oz when loaded 3D4 angle than 2D3 angle. (2) About of the P300, 3D4 angle(Otherwise, Oz point was reverse) and in the case of no equipment of liquid crystal shutter, there appeared PEAK near the P250. (3) There were 5% significant difference when the liquid crystal shutter was equiped and didn't, Therefore, this phenomenon show the possibility that Liquid crystal shutter influences on Visual Evoked Potentials.

• Journal of Mechanical Science and Technology
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• v.16 no.2
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• pp.147-154
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• 2002

The objective of this paper is to develop a nondestructive method for estimating the fracture toughness (K$\_$IC/) of CrMoV steels used as the rotor material of steam turbines in power plants. To achieve this objective, a number of CrMoV steel samples were heat-treated, and the fracture appearance transition temperature (FATT) was determined as a function of aging time. Nonlinear ultrasonics was employed as the theoretical basis to explain the harmonic generation in a damaged material, and the nonlinearity parameter of the second harmonic wave was the experimental measure used to be correlated to the fracture toughness of the rotor steel. The nondestructive procedure for estimating the 7c consists of two steps. First, the correlations between the nonlinearity parameter and the FATT are sought. The FATT values are then used to estimate K$\_$IC/, using the K$\_$IC/ versus excess temperature (i.e., T-FATT) correlation that is available in the literature for CrMoV rotor steel.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1771-1776
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• 2003

The supersonic swirl jet is being extensively used in many diverse fields of industrial processes since those lead to more improved performance, compared with the conventional supersonic no swirl jet. In the present study, an experiment is carried out to investigate the effect of annular swirl jet on the supersonic dual coaxial jet. A convergent-divergent nozzle with a design Mach number of 1.5 is used for the supersonic primary jet, and the sonic nozzles with four tangential inlets are used to make the secondary swirl jet. The primary jet pressure ratio is varied in the range from 3.0 to 7.0 and the outer annular jet pressure ratio is from 1.0 to 4.0. The interactions between the annular swirl and the inner supersonic jet are quantified by the pitot impact and static pressure measurements and visualized by using the Schlieren optical method. The results show that annular swirl jet alters the shock structure and impact pressure distributions compared with no swirl jet.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1314-1322
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• 2000

The acoustic property of reactive type single expansion chamber can be analyzed by traditional plane wave theory. This theory can be applied in low frequency range and has good performance. But this theory can't include higher order modes, therefore another method is essential to analyze acoustic filter in high frequency range. Many researcher suggested the method that can concern higher order modes, and their methods are using mode matching technique. But there is no method that can be applied to the analysis of single expansion chamber with arbitrary inlet/outlet duct position and numbers of higher order modes of inlet/outlet duct and middle chamber. In this paper, the method which can analyze single expansion chamber with arbitrary inlet/outlet duct position and numbers of higher order modes of inlet/outlet duct and middle chamber using fundamental mode matching technique, was suggested and the predictions by this method was compared with those by the finite element method, and the influence of inlet/outlet location to acoustic performance of single expansion chamber is investigated and explained by higher order mode effects.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.48-54
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• 2001

We investigate the generation of the dark spatial soliton and its role of wave guiding in Fe doped$LiNbO_3$ A cw Ar+ laser of 488 nm is used for the generation of the dark spatial soliton. The generation of the dark spatial soliton is observed even at the laser intensity as low as 10 mW/cm2. The self-defocusing effect is observed when the direction of the intensity variation is parallel to the optic axis, while it can't be seen when perpendicular to the axis. So, it is verified that the refractive index change is generated parallel to the optic axis. When 633 nm He-Ne laser beam is injected into the dark spatial soliton, the beam propagates just as in the diffraction free medium. So, it is verified that the dark spatial soliton can act as a waveguide.eguide.

• Textile Coloration and Finishing
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• v.7 no.1
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• pp.32-42
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• 1995

In order to reduce the amount of waste water generated from textile dyeing process and processing water, cotton fabric was bleached with ozone in ozone/water contact system, and dyed. The results obtained from the measurement of whiteness, reflectance, tensile strength, color difference, and K/S value of treated samples were as follow : 1) In ozone bleaching, factors affect whiteness most are treatment time and ozone dosage. As treatment time is lengthened, whiteness increases. Futhermore, bleaching effect is high in acidic treatment, but low in alkaline treatment. 2) As bleaching goes on, maximum absorption wave length shifts to shoter wavelengths. 3) As treatment time is lengthened or pH of treatment is low, tensile strenth of treated fabric decrease. 4) In all cases, color difference of dyed cotton fabrics in above 2% o.w.f. dyestuff concentration don't go beyond 1∼2 AN unit, compared with standard.

• Journal of Chest Surgery
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• v.22 no.1
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• pp.67-73
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• 1989

Forty two patients with chronic constrictive pericarditis, who were admitted to the Yonsei University College of medicine over a period of 18 years from January, 1970 to August, 1988, were analyzed retrospectively. Mean age of the patient was 33.5 year ranging from 6.8 to 60 years old. Male to female ratio was 1.3 to 1. Twenty-one cases [50%] were tuberculous origin [based on either associated pulmonary tuberculosis and/or caseous necrosis in thickened pericardial specimen] and 17 cases [40.5%] were idiopathic [non specific chronic inflammatory change was considered to be idiopathic]. Dyspnea on exertion was evident in 30 cases [71.4%] and abdominal distention in 21 cases [50%]. On physical examination, hepatomegaly [83.3%], neck vein distention [54.8%], distant heart sound [47.6%] and ascites were found. Thirty-nine patients showed low voltage of QRS and/or T wave flattening or inversion on EKG. Thirty-one cases had undergone cardiac catheterization which showed data compatible with chronic constrictive pericarditis. Midsternostomy group [n=15] had shown the most remarkable CVP decline [12.20 mmHg] as compared with bilateral submammary incision group [n=25, 8.96 mmHg] and left thoracotomy group [n=2, 7.75 mmHg] but difference was not significant statistically There was four early death among 42 patients [9.5%] including 3 cases of left ventricular failure and one cardiac tamponade. Main postoperative complications were wound infection [6 cases] and arrhythmia [3 cases]. Follow-up of 24 patients [mean; 55.3 months, ranging from 2 months to 155 months] revealed good functional status.