• Journal of Information Display
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• 제12권1호
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• pp.11-15
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• 2011

An inverse-twisted-nematic (ITN) transflective (TRF) liquid crystal (LC) display, where two imprinted optical films (IOFs) with surface microstructures are embedded was developed. One of the IOFs serves as an in-cell patterned retarder with multioptic axes, and the other behaves as a viewing-angle enhancement film. In the presence of an applied voltage, the surface microstructures on the IOFs provide the spontaneous twist of the LC from a vertically aligned state to a $90^{\circ}$ twisted-nematic (TN) state in the transmissive part, and to a $45^{\circ}$ TN state in the reflective part. The developed ITN TRF LC display exhibits high transmission and reflectance, fast response, and wide-viewing characteristics, along with achromaticity.

• Journal of Power Electronics
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• 제15권1호
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• pp.123-130
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• 2015

This paper investigates the high efficiency operation of a switched reluctance generator over a wide speed range. The system efficiency is improved by optimizing the current shape. A modified angle position control (MAPC) method that can be used to optimize the current shape over a wide speed range is proposed. Simulation and experimental results are presented to validate the effectiveness of the proposed control scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.848-851
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• 2003

Display devices are becoming increasingly important as an interface between humans and machines in the growing information society In display device, PDP(Plasma Display Panel) has many advantages in that wide screen, light weight, thin, wide viewing angle and unaffected by magnetic field. In this paper, modified ramp waveform is suggested by Vt Close Curve, and PDP driving circuit is designed by modified ramp waveform, this modified ramp waveform have more addressing wall voltage better then the old ramp waveform.

• 한국전기전자재료학회논문지
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• 제32권2호
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• pp.141-146
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• 2019

Non-emissive LCDs need a backlight, and have difficulty implementing wide viewing angles due to differences in phase retardation depending on the behavior of the liquid crystals. Although wide viewing angles are good characteristics for devices such as TVs, they are not good for mobile devices. In this paper, we propose ways to design diffusers with ELC lenses to achieve wide and narrow viewing angles depending on the circumstances. A study was conducted on optimizing the design of a liquid lens diffuser with the same light as that for an OLED, by extracting design factors that affect the performance of the diffuser and applying the Taguchi method to them.

• 한국멀티미디어학회논문지
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• 제23권3호
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• pp.395-401
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• 2020

In this paper, a motion-based ROI extraction algorithm from a high resolution fisheye image is proposed for multi-view monitoring systems. Lately fisheye cameras are widely used because of the wide angle-of-view and they basically provide a lens correction functionality as well as various viewing modes. However, since the distortion-free angle of conventional algorithms is quite narrow due to the severe distortion ratio, there are lots of unintentional dead areas and they require much computation time in finding undistorted coordinates. Thus, the proposed algorithm adopts an image decimation and a motion detection methods, that can extract the undistorted ROI image with a standard angle-of-view for the fast and intelligent surveillance system. In addition, a mesh-type ROI is presented to reduce the lens correction time, so that this independent ROI scheme can parallelize and maximize the processor's utilization.

• Tribology and Lubricants
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• 제35권6호
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• pp.350-355
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• 2019

Surface energy is an important factor in determining the performance of application components in terms of preventing adhesion failure between thin films. In this regard, numerous attempts have been made to acquire the desired surface energy through chemical treatment or by using micro/nanostructures. However, such approaches are expected to provide extreme values of surface energy, which may not be suitable in achieving the enhanced performance of applications. In this study, we propose a method to control surface energy by using bilayer metallic film heterostructures. We measure the water contact angle of incompatible (Ni/Ag) and compatible (Zn/Ag) metal pairs under several experimental factors, including thickness, time, and temperature. Furthermore, we conduct Auger electron spectroscopy measurements to investigate the atomic concentration with respect to depth after the change in the water contact angle. The experimental results reveal that three parameters, namely, compatibility, film thickness, and environmental temperature, are major factors in controlling the water contact angle. Thus, we experimentally demonstrate that controlling these three parameters can provide the approximate desired water contact angle. This result is expected to aid in the performance enhancement of a wide range of application components, where control of surface energy is required.

• Structural Engineering and Mechanics
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• 제51권3호
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• pp.471-485
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• 2014

Until now, the finite corner stiffness of the right-angle frames used as horizontal girders in a bonnet, have not been considered during the design process to result in not a precise result. This paper presents a design equation set for right-angle frames used as horizontal girders in a bonnet assuming rigid corner stiffness. By comparing the center stresses of the right-angle frame according to the design equation set with the results of the finite element method, the master curves for the empirical corner stiffness can be determined as a function of slenderness ratio. A second design equation set for a right-angle frame assuming finite corner stiffness was derived and compared with the first equation set. The master curves for the corner stiffness and the second design equation set can be used to determine the design moments at the centers of the girder so that the bending stresses can be analyzed more precisely.

• 대한기계학회논문집B
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• 제22권11호
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• pp.1591-1602
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• 1998

Simple spanwise distribution models of deviation angle and pressure loss coefficient due to the tip leakage flow are formulated for use in association with the streamline curvature method as a flow analysis. Combining these new models with the previous deviation and loss models due to secondary flow, a robust streamline curvature method is established for flow analysis of single-stage, subsonic axial turbines with wide ranges of turning angle, aspect ratio and blading type. At the exit from rotor rows, the flow variables are mixed radially according to a spanwise transport equation. The proposed streamline curvature method is tested against a forced vortex type turbine as well as a free vortex type one. The results show that the spanwise variations of flow angle, axial velocity and loss coefficients at rotor exit are predicted with good accuracy, being comparable to a steady three-dimensional Navier-Stokes analysis. This simple and fast flow analysis is found to be very useful for the turbine design at the initial design phase.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.7-8
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• 2012

The effects of interaction between partially premixed and premixed swirl flames on CO and NOx emissions were experimentally investigated using a hybrid/dual swirl jet combustor for a micro-gas turbine. Under the condition of constant angle ($45^{\circ}$) for outer swirl vane, the angle and direction of inner swirl vane installed for a partially premixed flame were varied as main parameters with a constant fuel flow rate for each nozzle. It was found that for all conditions, CO and NOx emissions were measured below 4 ppm and 15 ppm at 15% $O_2$, respectively, in a wide range of equivalence ratio (0.6~0.9). For co-swirl flows, CO emission increased dramatically as the angle of inner swirl vane increased from $15^{\circ}$ to $45^{\circ}$ near lean-flammability limit (i.e. equivalence ratio of 0.5). On the other hand, the case of swirl $angle=45^{\circ}$ provided the lowest NOx emission at higher equivalence ratios than 0.6. For counter-swirl flows, the case of swirl $angle=45^{\circ}$ extended the lean-flammability limit but higher NOx emissions were found compared to those of co-swirl flows. These results could be inferred by interaction between (inner) partially premixed and (outer) premixed swirl flames. However, these estimations were not clear yet because there was insufficient data on turbulent flow structure and fuel-air mixing in the present experimental approach.

• 한국정밀공학회지
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• 제26권4호
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• pp.47-54
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• 2009

In the last few years, lasers have found new applications as tools for ceramic machining which is laser-assisted machining(LAM). LAM process for the machining of difficult-to-machine materials such as structural ceramics, has recently been studied on silicon nitride workpiece for a wide range of operating condition. However, there have been few studies on rake angle in LAM process. In this paper we analyzed difference of machinability between positive and negative rake angle in tools. We have obtained interesting results that we could eliminate chattering, lower specific cutting and cutting ratio in case of positive rake angle. The results suggest that positive rake angled tools can make more plastic deformation and stable cutting of silicon nitride in comparison with negative rake angled one.