• Journal of Information Display
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• v.2 no.3
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• pp.72-77
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• 2001

Amorphous silicon thin-film transistors (a-Si TFTs) were incorporated into Mo-tip-based triode-type field emitters and diode-type ones of carbon nanotubes for an active-matrix cathode (AMC) plate of field emission displays. Also, we developed a novel surface-treatment process for the Mo-tip fabrication, which gleatly enhanced in the stability of field emission. The field emission currents of AMC plates on glass substrate were well controlled by the gate bias of a-Si TFTs. Active-matrix field emission displays (AMFEDs) with these AMC plates were demonstrated in a vacuum chamber, showing low-voltage matrix addressing, good stability and reliability of field emission, and highly uniform light emissions from the anode plate with phosphors. The optimum design of AMFEDs including a-Si TFTs and a new light shield/focusing grid is discussed.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.17 no.3
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• pp.225-232
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• 2013

Objectives The aim of this study is to design a part in contact with the face of computerized tongue diagnosis system (CTDS), so that external light is effectively shielded even if the facial appearance and degree of protrusion differ when a patient opens or closes his/her jaws. Methods Each of the 4 researchers manually produced clay models of the part in contact with the face of CTDS. Shielding and contact feeling of the clay models were evaluated by 20 assessors. Based on the evaluation, we selected the appropriate model and produced the final silicon model. Then we evaluated the performance of the shielding of the completed silicon model. We took tongue pictures of 60 participants with a CTDS applying the silicon model in condition with external light and without it. The color values in RGB color model and gray scale of the tongue pictures in condition with external light were compared with those without external light. Results There was no significant difference between the color values of the picture taken in condition with external light and those without external light. Conclusions We concluded that the produced part in contact with the face of CTDS can effectively block out the external light.

• ETRI Journal
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• v.24 no.4
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• pp.290-298
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• 2002

We present, for the first time, a prototype active-matrix field emission display (AMFED) in which an amorphous silicon thin-film transistor (a-Si TFT) and a molybdenum-tip field emitter array (Mo-tip FEA) were monolithically integrated on a glass substrate for a novel active-matrix cathode (AMC) plate. The fabricated AMFED showed good display images with a low-voltage scan and data signals irrespective of a high voltage for field emissions. We introduced a light shield layer of metal into our AMC to reduce the photo leakage and back channel currents of the a-Si TFT. We designed the light shield to act as a focusing grid to focus emitted electron beams from the AMC onto the corresponding anode pixel. The thin film depositions in the a-Si TFTs were performed at a high temperature of above 360°C to guarantee the vacuum packaging of the AMC and anode plates. We also developed a novel wet etching process for $n^+-doped$ a-Si etching with high etch selectivity to intrinsic a-Si and used it in the fabrication of an inverted stagger TFT with a very thin active layer. The developed a-Si TFTs performed well enough to be used as control devices for AMCs. The gate bias of the a-Si TFTs well controlled the field emission currents of the AMC plates. The AMFED with these AMC plates showed low-voltage matrix addressing, good stability and reliability of field emission, and good light emissions from the anode plate with phosphors.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.4
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• pp.166-171
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• 2005

Shielding methods on ELF(Extremely Low Frequency) magnetic fields may include the use of induced currents, modification of magnetic field flux patterns using high permeability and/or high conductivity materials, and others. The magnetic shielding properties of enclosures can be utilized to reduce the magnetic field of current carrying conductors. In this paper, to get a more practical understanding of shielding phenomena, we have investigated the magnetic field reduction by means of 3 dimensional numerical analysis and experiments. We found copper could reduce flux density more then permalloy in both cases of box shield and cylindrical shield. Iron under l0$\mu$T of 1 phase could reduce flux density about $20\%$ more than silicon steel, but both of them under 50$\mu$T has a similar reduction rate of $10\%$. The 3 phase horizontal model gave the highest reduction rate and the 1mm thickness iron under 10$\mu$T of 3 phase lines did lowest.

• Radiation Oncology Journal
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• v.2 no.2
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• pp.271-280
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• 1984

The peripheral dose, defined as the dose outside therapeutic photon fields, which is responsible for the functional damage of the critical organs, fetus, and radiation. induced carcinogenesis, has been investigated for $^{60}Co\;\gamma$ ray and 10 MV Xray. It was measured by silicon diode controlled by semiautomated water phantom without any shielding or with lead plate of HVL thickness put horizontally or vertically to shield stray radiations. Authors could obtain following results. 1. The peripheral dose was larger than $0.7\%$ of central axis maximum dose even at 20cm distance from field margin. That is clinically significant, so it should be reduced. 2. Even for square fields of 10 MV Xray, radial peripheral dose distribution did not coincide with transverse distribution, because of the position of collimator jaws. 3. Between surface and $d_m$, the peripheral dose distributions show a pattern of the dose distribution of electron beams and the maximum doss was approximately proportional to the length of a side of square field. 4. The peripheral doses depended on radiation quality, field size, distance from field margin and depth in water. Distance from field margin was the most important factor. 5. Except for near surface, the peripheral dose from phantom was approximately equal to that from therapy unit. 6. To reduce the surface dose outside fields, therapist should shield stray radiations from therapy unit by lead plate of at least one HVL for 10 MV X-ray and by bolus equivalent to tissue of 0.5cm thickness for $^{60}Co$. 7. To reduce the dose at depth deeper than $d_m$, it is desirable to shield stray radiations from therapy unit by lead.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.6
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• pp.57-63
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• 2019

S-parameters were used to analyze the effect of the circuit according to the height of the EMI shield layers. Among the S-parameters, S11, S21, S22, and S31 were used as factors for determining the effect on the circuit function. Simulations were performed using shields made of Graphite and Ferrite, and the frequencies were run from 100 MHz to 1 GHz. As the height of the shield was increased, the value of S21 was getting closer to 0 dB. In addition, the SE value was confirmed to improve the shielding performance according to the thickness of the insulating layer only in a specific frequency band. Based on 800um with thickest silicon dioxide thickness, the FG structure averaged -1 dB in narrow frequency bands between 100 MHz and 300 MHz, showing better efficiency than GF with an average of -2 dB. Although GF structures do not show high efficiency, they exhibit average performance of -3 dB in frequency bands between 100 MHz and 1 GHz rather than FG structures that sway over a wide range. In other words, FG and GF structures have trade-off structures. Therefore, it should be noted that the appropriate structure is selected for use.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.530-538
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• 2007

An inductor library for efficient low cost RFIC design has been developed based on a standard digital 0.18 ${\mu}m$ CMOS process. The developed library provides four structural variations that are most popular in RFIC design; standard spiral structure, patterned ground shield(PGS) structure to enhance quality factor, stacked structure to enable high inductance values in a given silicon area, multilayer structure to lower series resistance. Electromagnetic simulation, equivalent circuit, and parameter extraction processes have been verified based on measurement results. The extensive measurement and simulation results of the inductor library can be a great asset for low cost RFIC design and development.

• Journal of the Korean Society of Radiology
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• v.17 no.2
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• pp.215-221
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• 2023

Among brain CT scan conditions including the lens, the tube voltage was changed to 80, 100, and 120 kVp and applied. The change in dose was analyzed using lead, lead goggles and barium sulfate silicon shielding materials, and the degree of influence of the shielding materials on image quality was compared and analyzed by applying the SNR, CNR, and SSIM index analysis methods. As a result, it was analyzed that although the dose was reduced by applying all shielding materials, the difference in dose reduction was not large (P > 0.05). In addition, as for the change in image quality due to the application of the shielding material, SNR and CNR were the highest when lead goggles were applied, and the structural similarity was measured to be the best as it was closest to the reference value of 1 in SSIM analysis. Therefore, based on the results of this study, it is thought that if more diverse shielding materials and clinical test results are derived and applied, it will be helpful for the clinical application criteria in the case of shielding utilization inspection.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.107-108
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• 2008

This article describes optimization for PGS(Patterned Ground Shield) of rectangular spiral inductor using Taguchi's Design of Experiment. PGS is decrease method of parasite component by silicon substrate among dielectric loss reduction method. Using taguchi's design of experiment, each parameter is fixed upon that PGS high poison(A), slot spacing(B), strip width(C) and overlap turn number(D) of PGS design parameter. Then we verified that percentage contribution and design sensitivity analysis of each parameter and level by signal to noise ratio of larger-the-better type. We consider percentage contribution and design sensitivity of each parameter and level, and then verify that model of optimization for PGS is lower inductance decreasing ratio and higher Q-factor increasing ratio by EM simulation.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.232.2-232.2
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• 2014

Since its discovery in 2004, graphene, a sp2-hybridized 2-Dimension carbon material, has drawn enormous attention. A variety of approaches have been attempted, such as epitaxial growth from silicon carbide, chemical reduction of graphene oxide and CVD. Among these approaches, the CVD process takes great attention due to its guarantee of high quality and large scale with high yield on various transition metals. After synthesis of graphene on metal substrate, the subsequent transfer process is needed to transfer graphene onto various target substrates, such as bubbling transfer, renewable epoxy transfer and wet etching transfer. However, those transfer processes are hard to control and inevitably induce defects to graphene film. Especially for wet etching transfer, the metal substrate is totally etched away, which is horrendous resources wasting, time consuming, and unsuitable for industry production. Thus, our group develops one-step process to directly grow graphene on glass substrate in plasma enhanced chemical vapor deposition (PECVD). Copper foil is used as catalyst to enhance the growth of graphene, as well as a temperature shield to provide relatively low temperature to glass substrate. The effect of growth time is reported that longer growth time will provide lower sheet resistance and higher VSG flakes. The VSG with conductivity of $800{\Omega}/sq$ and thickness of 270 nm grown on glass substrate can be obtained under 12 min growing time. The morphology is clearly showed by SEM image and Raman spectra that VSG film is composed of base layer of amorphous carbon and vertically arranged graphene flakes.