• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.1037-1044
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• 2008

Radiation efficiency and antenna gain, in this paper, can be increased by the slot on EMI shield painted on the mobile phone back cover. When the EMI slot which has proper dimension and location is located on the EMI paining area in the phone, the increment of antenna current density due to mutual coupling between the antenna and slot derives increment of antenna efficiency. For the verification of EMI slot effect, we apply the EMI slot to the mobile phone which is operating on GSM/DCS/USPCS/WCDMA quad band, and measure $S_{11}$ and antenna efficiency. It's shown that resonant frequency is not changed and radiation efficiencies to frequency channels by EMI slot are increased from 0.21 % to 8.96 %.

• Journal of IKEEE
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• v.24 no.2
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• pp.619-625
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• 2020

In this paper, we propose a TS-DMOSFET(Trench Shielded DMOSFET) structure in which P+ shielding region is formed in a deeper region than C-DMOSFET(Conventional DMOSFET) and S-DMOSFET(Shielded DMOSFET). Using TCAD simulation to compare the static characteristics of TS-DMOSFET with C- and S-DMOSFET. As for the structure proposed, the doping is followed by the source trench process. Despite the fact that it is a SiC material, this allows it to form a P+ shielding region in a deep area. Followed by completely suppressing the reach-through effect. As a result, when the breakdown voltage of the three structures is 3.3kV, the Ron of TS-DMOSFET is 9.7mΩ㎠. Thus, it is 68% and 54% smaller than the Ron of C-DMOSFET and S-DMOSFET respectively.

• Journal of radiological science and technology
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• v.43 no.5
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• pp.323-329
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• 2020

The purpose of this study is to investigate the effect of radiation shielding on the thyroid organ dose and image quality during Chest PA examination using automatic exposure control system. This study was conducted in the patient posture and examination conditions such as Chest PA using human model phantom. An experiment without shielding was set as a control group (non) and the cases of using paper coated with a contrast agent (contrast) and bismuth (bismuth) were used as experimental groups. Compared to non-shielded(non), the dose at bismuth increased about 7% in C(cervical vertebrae)5 and C6 and 14% in C7 and contrast showed dose increases of about 17 to 19% in C5 and C6 and about 21% in C7. As a result of the image quality comparison, when measured in the center of the cervical vertebrae, both SNR and CNR in bismuth increased about 40% higher than non, and contrast showed about 8 to 9% improvement. Compared with soft tissues of the cervix, bismuth reduced SNR by about 15% and CNR by about 13%, in contrast, SNR decreased by 11%, and CNR decreased by about 10%. In the Chest PA using AEC, the method of using the shield in front of the collimator has the advantage to observe the anatomical structure of the neck area well compared to the method using the lead. However, the dose at the neck can be increased by 7-21% depending on shielding materials.

• Journal of the Korea Society of Computer and Information
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• v.21 no.6
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• pp.89-96
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• 2016

Damage and attack size of cyber terror is growing to the national size. Not only targeting at a certain companies or individuals but number of cyber terror targeting government bodies or unspecific people is increasing. This is because compared to traditional weapon, input cost is very cheap but ripple effect and shock are much stronger, affecting not only certain groups but also each individuals. 'Anti-terror measurement for protection of nation and public safety' passed last month is one of the renowned measurement passed regardless of objection from opposition party. The opposition party went against this through filibuster for 192 hours but this finally passed National Congress due to lack of oppositions. Korean government is taking post actions after passage of anti-terror measurement. Legislation of enforcement ordinance and regulations is due by 6th of next month. This regulation will be executed from June 4th after legislation. Whenever there is any security issues such as hacking of Korea Hydro and Nuclear Power and National Intelligence Service happens, lot of attention is made to those hackers. However, social recognition or management of those hackers need lot more improvement. Especially, as market of internet of things is increasing, there is an increased anxiety on information security. But as we only rely on security solutions, this problems are keep happening. Therefore, active investment on nurturing hackers who play the role of 'spear and shield' shall be made. Government should put more efforts to allow white hackers to show their abilities. We should have a policy for supporting high-quality programs such as BoB. To make information protection industry into future growth engine, it is necessary to nurture professionals for information protection and white hackers through special programs. Politicians should make related regulations as soon as possible to remove factors that prevent swift management of cyber attack due to lack of legislation. Government should pay lot more financial investment to nurturing professional manpower than now. Protecting life and asset of nation is responsibility and duty of our government. We all should recognize that controlling cyber attack is a part of national defense.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.3
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• pp.202-210
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• 2016

A thermal barrier coating (TBC) has been widely applied to machine components working under high temperature as a thermal insulator owing to its critical financial and safety benefits to the industry. However, the nondestructive evaluation of TBC damage is not easy since sensing of the microscopic change that occurs on the TBC is required during an evaluation. We designed an eddy current probe for evaluating damage on a TBC based on the finite element method (FEM) and validated its performance through an experiment. An FEM analysis predicted the sensitivity of the probe, showing that impedance change increases as the TBC thermally degrades. In addition, the effect of the magnetic shield concentrating magnetic flux density was also observed. Finally, experimental validation showed good agreement with the simulation result.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.25-25
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• 2009

종래의 위보기 자세에서 용접은 중력이 모재의 표면으로 향하고 있어 용융금속이 중력에 의해 표면방향으로 흘러내리게 되어 용접 실시가 불가능하였다. 이에 Shield Gas Force, Trailing Gas Force 그리고 Ahead Gas Force를 적절히 적용하여 Position Welding에서 중력으로 인해 Molten Metal이 처지는 문제를 극복하여 생산성 향상으로 연결할 수 있음을 선행 실험을 통해 확인하였으나 기존의 C(Convergent)형, CP(Convergent Divergent)형 및 P(Parrallel)형 가스 노즐은 용접조건에 따라 실드 가스의 소모량이 많고, 토출되는 실드가스력이 부족하여 용접시 볼록한 이면 비드 형성을 위한 용융 풀을 효과적으로 제어 할 수 없다. 따라서 본 연구에서는 동일량의 실드 가스 공급시 가스 노즐을 통해 토출되는 실드가스의 소모를 줄이고 실드가스력을 극대화하여 저가의 고생산성을 가진 친 환경 용접기술(Green welding)에 부합하는 CDP(Convergent Divergent Parrallel)형 가스 노즐을 제작하여 기존의 CP형 가스 노즐과 비교 분석하였다. 또한 Overhead Position에서의 비드형상제어와 Flat Position에서 방풍효과를 비교해 보았다. 그 결과 CDP Nozzle은 CP Nozzle보다 동일한 유량에서 풍속은 3.5배, 냉각능력은 1.5배, 가스압력은 6.25배로 우수한 성능을 확인할 수 있었고, Overhead Position에서 가스 유량을 동일하게 하여 용접하였을 때 CP Nozzle의 경우 오목한 이면비드가 나타났지만 CDP Nozzle의 경우 볼록하게 양호한 이면비드 형상이 나타났고, Flat Position에서의 방풍효과 비교실험에서 CDP Nozzle에서는 깊고 균일한 용입을 CP Nozzle에서는 불안정한 용입이 나타났는데 이는 CDP Nozzle의 경우 풍속에 의한 Arc Blow가 적게 발생하여 상대적으로 더 나은 용입을 확인하였다.

• Journal of the Korean Institute of Gas
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• v.23 no.4
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• pp.28-39
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• 2019

In this paper is image characteristics of main gas can be a basic data for the identification of the type of leaking gas and the estimation of the emission quantity in OGI(Optical Gas Image) technology. The purpose of this research is to observe the differences of leaking gas images of the two important hydrocarbons of methane and propane in the industry. We fabricated a wind shield of quartz-based with infrared-permeable properties was prepared and methane and propane were simultaneous emission and then photographed with an infrared OGI camera and we are analyzed it. We have a stable image with windbreak of quartz-based minimizes the effect of wind. As a result of analyzing the image of two hydrocarbons with a leakage gas reference value of 1 L/min, an easily recognizable distances by OGI camera were 6 m for methane and 9 m for propane. In the distances range of 1 to 10 m between the infrared camera and the leaking gas point, the gas plume size of the propane gas was larger and clear than that of the methane gas plume. Compared with the number of points in the image, propane was 3.8 times more than methane.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.42-55
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• 2021

In this study, the effect of nozzle performance according to the selection of the center line equation. Three of S-type nozzles and three of double S-type nozzles were designed using the curve equation and design parameters, and the nozzle shielding performance was evaluated using the shielding ratio definition. In order to analyze the internal flow of the nozzle, the characteristics of the velocity distribution and pressure distribution were studied, and the nozzle performance was evaluated through the total thrust ratio(f) and the nozzle insulation efficiency coefficient(η). On the other hand, the centerline with a sharply change in curvature at the entrance has a low nozzle performance and a high shielding rate. The double S-type nozzle is excellent nozzle performance and shielding rate by using a smooth centerline at the first curvature.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2614-2624
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• 2022

Monte Carlo simulations were used to model a portable Neutron backscattering (NBT) sensor suitable for detecting plastic anti-personnel mines (APMs) buried in dry and moist soils. The model consists of a 100 MBq ²⁵²Cf source encapsulated in a neutron reflector/shield assembly and centered between two ³He detectors. Multi-parameter optimization was performed to investigate the efficiency of Be/Zr(BH₄)₄ and Be/Be(BH₄)₂ assemblies in terms of increasing the signal-to-background (S/B) ratio and reducing the total dose equivalent rate. The MCNP results showed that 2 cm Be/3 cm Zr(BH₄)₄ and 2 cm Be/3 cm Be(BH₄)₂ are the optimal configurations. However, due to portability requirements and abundance of Be, the ²⁵²Cf-2 cm Be/3 cm Be(BH₄)₂ NBT model was selected to scan the center of APM buried 3 cm deep in dry and moist soils. The selected NBT model has positively identified the APM with a S/B ratio of 886 for dry soils of 1 wt% hydrogen content and with S/B ratios of 615, 398, 86, and 12 for the moist soils containing 4, 6, 10, and 14 wt% hydrogen, respectively. The total dose equivalent rate reached 0.0031 mSv/h, suggesting a work load of 8 h/day for 806 days within the permissible annual dose limit of 20 mSv.

• Journal of Pharmacopuncture
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• v.26 no.4
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• pp.319-326
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• 2023

Objectives: The study's goal was to find out whether Chrysanthemum rubellum extract has anti-diabetic properties by concentrating on α-glucosidase and the PTP-1B signaling pathway. C. rubellum flowers were used for extraction using Methanol/water (80/20) as solvent. Methods: LC-MS techniques was used to check the presence of phytoconstituents present in C. rubellum extract. In vitro antidiabetic activity was evaluated using α-glucosidase inhibitory activity and PTP-1B signaling pathway. On Streptozotocin (STZ)-induced rats with diabetes, the in vivo antidiabetic efficacy was assessed using a test for oral glucose tolerance. Results: The phytoconstituents identified in the extract of C. rubellum were apigenin, diosmin, myricetin, luteolin, luteolin-7-glucoside, and Quercitrin as compound 1-6, respectively. Results showed that diosmin exhibited highest α-glucosidase inhibitory activity i.e. 90.39%. The protein level of PTP-1B was lowered and the insulin signalling activity was directly increased by compounds 1-6. The maximum blood glucose levels were seen in all groups' OGTT findings at 30 minutes following glucose delivery, followed by gradual drops. In comparison to the control group, the extract's glucose levels were 141 mg/dL at 30 minutes before falling to 104 mg/dL after 120 minutes. The current study has demonstrated, in summary, that extract with phytoconstituents reduce blood sugar levels in rats. Conclusion: This finding suggests that extract may reduce the chance of insulin resistance and shield against disorders like hyperglycemia.