• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.3
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• pp.240-245
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• 2013

Each pixel of InfraRed(IR) sensor differently responds to IR light as time elapses or the sensor on/off operation is repeated. As a result, the quality of IR sensor image is deteriorated, and therefore NUC(Non-uniformity Correction) is periodically needed for IR sensor. In this paper, in order to perform NUC in the Satellite, on-board V-grooved blackbody is designed with a baffle so that the emissivity of black body is to be higher than 0.995 as well as the temperature deviation is less than $1^{\circ}C$ in the range of the infrared wave length from 3.3 to $5.2{\mu}m$. To check its performance, the emissivity and the surface temperature of the blackbody by TRT(Transfer Reference Thermometer) and IR Micrometer scanner are measured, respectively. From the results, black body design is verified and the uncertainty of NUC is estimated through the measurement results.

• Korean Journal of Materials Research
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• v.22 no.3
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• pp.130-135
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• 2012

We present a method of graphene synthesis with high thickness uniformity using the thermal chemical vapor deposition (TCVD) technique; we demonstrate its application to a grid supporting membrane using transmission electron microscope (TEM) observation, particularly for nanomaterials that have smaller dimensions than the pitch of commercial grid mesh. Graphene was synthesized on electron-beam-evaporated Ni catalytic thin films. Methane and hydrogen gases were used as carbon feedstock and dilution gas, respectively. The effects of synthesis temperature and flow rate of feedstock on graphene structures have been investigated. The most effective condition for large area growth synthesis and high thickness uniformity was found to be $1000^{\circ}C$ and 5 sccm of methane. Among the various applications of the synthesized graphenes, their use as a supporting membrane of a TEM grid has been demonstrated; such a grid is useful for high resolution TEM imaging of nanoscale materials because it preserves the same focal plane over the whole grid mesh. After the graphene synthesis, we were able successfully to transfer the graphenes from the Ni substrates to the TEM grid without a polymeric mediator, so that we were able to preserve the clean surface of the as-synthesized graphene. Then, a drop of carbon nanotube (CNT) suspension was deposited onto the graphene-covered TEM grid. Finally, we performed high resolution TEM observation and obtained clear image of the carbon nanotubes, which were deposited on the graphene supporting membrane.

• Journal of the Korean Vacuum Society
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• v.15 no.3
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• pp.280-286
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• 2006

A distributed Bragg reflector (DBR) for the application of $1.3{\mu}m$ vertical cavity surface emitting laser (VCSEL) has grown by digital-alloy AlGaAs layer using the molecular beam epitaxy (MBE) method. The measured reflection spectra of the digital-alloy AlGaAs/GaAs DBR have uniformity in 0.35% over the 1/4 of 3-inch wafer. Furthermore, the TEM image showed that the composition and the thickness of the digital-alloy AlGaAs layer in AlGaAs/GaAs DBR was not affected by the temperature distribution over the wafer whole surface. Therefore, the digital-alloy AlGaAs/GaAs DBR can be used to get higher yield of VCSEL with the active medium of InAs quantum dots whose gain is inhomogeneously broadened.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.5
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• pp.382-388
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• 2016

When Flat Panel Display (FPD) is made with backlight module, such as LED TV, it inherently suffers from the non-uniform backlight luminance problem that results in un-even brightness distribution throughout the TV screen. If the luminance of each pixel location of a TV screen as a function of the driving voltage can be measured, it can be used to compensate the non-uniformity of the backlight module. We use a carefully calibrated imaging system to take pictures of a TV screen at different levels of brightness and generate the compensation functions for the driving circuitry to correct the luminance level at each pixel location. Making use of the fact that the luminance of the screen is normally brightest at around the center of the screen and gradually decreases toward the border of the screen, the luminance of the whole TV screen is approximated by a mathematical function of the pixel locations. The parameters of the function are computed in the least square sense by the values of both the pixel luminance sent from the driving circuit and the grayscale value measured from the image taken by the imaging system. To justify the correction system, a simple second order polynomial function is used to approximate the luminance across the screen. When the driving circuit voltage is corrected according to the measured function, the variance of the screen luminance is reduced to one tenth of the one measured from the un-corrected TV screen.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.4
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• pp.45-52
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• 2009

We proposed a new pixel circuit and driving method for the large-area, high-luminance AMOLED applications in this study. We designed with the low-temperature poly-silicon(LTPS) thin film transistors(TFTs) that has poor uniformity but stable characteristic. To improve the uniformity of an image, the threshold voltage($V_{TH}$) and the mobility of the TFTs can be compensated together. The proposed method overcomes the previous methods for mobility compensation, and that is profitable for large-area applications. Black data insertion was introduced to improve the characteristics for moving images. AMOLED panel can operate in two compensation mode, so the luminance degradation by mobility compensation can be released. The scan driver for controlling the pixel circuits were optimized, and the compensation mode can be controlled simply by that. Final driving signal has large timing margin, and the panel operates stably. The pixel circuit was designed for 14.1" WXGA top-emission ANGLED panel. The non-uniformity of the designed panel was estimated under 5% for the mobility compensation time of 1us.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.391-396
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• 2020

In this study, we developed a phosphor film screen that can be applied to radiographs during non-destructive testing using Gd₂O₂S:Tb phosphor compounds. The image uniformity of the fabricated phosphor screen film was analyzed by FE-SEM, RMS and RDS analysis. In addition, the tensile strength, elongation, and modulus of elasticity of the Gd₂O₂S:Tb phosphor screen were evaluated by measuring the stress-strain characteristic curve. As a result, it was evaluated that the RSD value had an excellent image uniformity within 10% of the evaluation criteria. In addition, as a result of evaluation of physical properties, the tensile strength was 1.1760 N/㎟, the tensile strength at break was 1.1515 N/㎟. These results suggest that the Gd₂O₂S:Tb phosphor screen fabricated using the room temperature gel-printing method could be applied to digital radiography detectors for radiography.

• Journal of radiological science and technology
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• v.34 no.4
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• pp.315-321
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• 2011

The goal of this study is to reduce patient exposure dose by providing image quality and radiation dose according to inspection methods. Volume Computed Tomography Dose Index(CTDIvol) and Dose Length Product(DLP) of prospective and retrospective ECG gating snapshot segment of Coronary CT angiography(CTA) were measured each snapshot segment methods. CT number, noise, uniformity, and resolution were also measured using phantom under the same condition of coronary CTA. The results showed that CT number, noise, uniformity and resolution are similar to each other. In terms of CTDIvol and DLP, however, measurement dose of prospective ECG gating snapshot segment was lower than the retrospective case by 37.5% and 40.3%. Therefore, it is highly recommended that in the coronary CTA, prospective ECG gating scan mode should be chosen to reduce patient dose.

• Wind and Structures
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• v.31 no.3
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• pp.229-240
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• 2020

In the present work, the main features of primary vortices and the vorticity concentrations downstream of vortex bursting in crossflow plane of a delta wing with a sweep angle of Λ=70° were investigated under the variation of the sideslip angles, β. For the pre-review of flow structures, dye visualization was conducted. In connection with a qualitative observation, a quantitative flow analysis was performed by employing Particle Image Velocimetry (PIV). The sideslip angles, β were varied with four different angles, such as 0°, 4°, 12°, and 20° while angles of attack, α were altered between 25° and 35°. This study mainly focused on the instantaneous flow features sequentially located at different crossflow planes such as x/C=0.6, 0.8 and 1.0. As a summary, time-averaged and instantaneous non-uniformity of turbulent flow structures are altered considerably resulting in non-homogeneous delta wing surface loading as a function of the sideslip angle. The vortex bursting location on the windward side of the delta wing advances towards the leading-edge point of the delta wing. The trajectory of the primary vortex on the leeward side slides towards sideways along the span of the delta wing. Besides, the uniformity of the lift coefficient, C_L over the delta wing plane was severely affected due to unbalanced distribution of buffet loading over the same plane caused by the variation of the sideslip angle, β. Consequently, dissimilarities of the leading-edge vortices result in deterioration of the mean value of the lift coefficient, C_L.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.2
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• pp.58-69
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• 2003

The Hemi-sphere projection method produces an image that includes all surrounding visual landscape from a view point. This characteristic can solve the problem of perspective method that has only a limited view angle, and thus can be a potentially effective method for the analysis of visual landscape. This study tried to adopt the hemi-sphere projection method in the evaluation of streetscape, and examined its effectiveness and possibilities. Computer animations using the perspective method and the hemi-sphere method were produced for Bang-Hak Ro, Seoul, and the kames of the animations were reclassed to identify the visibility ratio of physical elements(buildings, sky and mountains). A preference questionnaire was given to 51 university students, and the relationships between the visibility ratio and visual preference were analyzed. The results showed that visual preference of streetscape can be explained by three factors: Openness, Uniformity, and Variousness, accounting for 63.2% of the total variance, and among which Openness showed the highest proportion at 32.1％. The visibility ratio calculated by the hemi-sphere method yielded strong correlation coefficients with Openness, and it was much higher than with the perspective method. The hemi-sphere method also produced significant correlation coefficients about Uniformity and Variousness, but the perspective method could not. The results demonstrated that the hemi-sphere method can provide more accurate observation of visual changes, and that it can be an effective method for the analysis of streetscape.

• The Korean Fashion and Textile Research Journal
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• v.20 no.2
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• pp.167-176
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• 2018

In this study, an eye-tracking program that can confirm a design cognition process was developed for the purpose of presenting strategic methods to create fashion images, and the program was used to identify what effects fashion models' external characteristics have on the cognition of design. The data for analysis were collected through an eyemovement tracking experiment and a survey, with the focus on the research problem that differences in models' external uniformity will lead to differences in the eye movement for perceiving models and design as well as the image sensibility. The results of the analysis are as follows. First, it was confirmed that the uniformity of model types and the simplicity/complexity of design led to differences in the eye movement directed at design and models and the gaze ratio. Consequently, it is deemed that models should be selected in consideration of the characteristics of design and the intention of planning when creating fashion images. Second, it was found that in terms of the cognition of design, external conditions of models affect design sensibility. A change in models led to a subtle difference in sensibility cognition even when the design condition did not change. Thus, not only the design but also model attributes are factors that should be considered important in fashion planning.