• Journal of the Korean Magnetics Society
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• v.5 no.3
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• pp.197-202
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• 1995

고주파용 전원의 필요성이 대두되면서 고주파에서 낮은 자기손실을 가진 재료의 개발이 요구되고 있다. Mn-Zn 페라이트의 자기손실은 전기비저항의 증거나 소결시 미세구조의 제어로 줄일 수 있다. 본 연구에서는 연쇄고온합성법(Self-propagation High- temperature Synthesis)에 의해 제조된 $_Mn_{0.72}$Z $n_{0.22}$)$_{0.94}$ (F $e_{2}$ $O_{3}$)$_{1.06}$ 조성의 Mn-Zn페라이트에서 첨가물이 미세구조와 자기적 성질에 미치는 영향에 대해 조사하였다. $SiO_{2}$와 Ca $Co_{3}$의 복합첨가에 의해 미세구조의 미세화와 아울러 낮은 자기손실 특성을 얻을 수 있었다. 그러나 첨가 물의 과다 첨가시에는 비정상입자성장 조직이 나타났으며 자기적 성질이 현저히 저하 하였다. 전기비저항, 자기손실의 주파수 의존 결과에 근거하여 주된 자기손실기구 및 이에 미치는 첨가물 효과에 대해 논하였다.

• Clinical and Experimental Reproductive Medicine
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• v.35 no.1
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• pp.77-82
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• 2008

Objective: This study was performed to investigate the efficacy and safety of radiofrequency (RF) myolysis under transvaginal ultrasound guidance. Methods: Transvaginal RF myolysis had been performed in one hundred nine women with uterine leiomyoma at Chung-Ang University hospital between Dec. 2004 and Mar. 2007. All patients, mean aged $42.8{\pm}5.8$ years, desired their uterine conservation. Patients underwent physical examination, transvaginal pelvic ultrasound for measurement of the lesions preoperatively. Follow up was done at 1 week, 1 month, 3 months, 6 months after RF myolysis by same physician and measurement of size and volume of myoma and improvement of myoma specific symptoms such as menorrhagia and dysmenorrhea were checked at each visit. Results: The mean maximal diameter of myomas treated by RF myolysis was $6.1{\pm}0.5\;cm$ and average time of the procedure was $16.3{\pm}8.5$ minutes. A significant decrease of myoma size and volume was observed at 1 month after myolysis. Mean reduction in maximal diameter was $29.9{\pm}4.8%$ at 1 week (p<0.001), $41.5{\pm}1.5%$ at 1 month (p=0.05), $46.2{\pm}3.9%$ at 3 months (p=0.003), $54.6{\pm}6.1%$ at 6 months (p<0.001) after RF myolysis respectively. Mean reduction in volume was $44.4{\pm}8.3%$ (p=0.001), $68.1{\pm}4.2%$ (p=0.035), 73.9$73.9{\pm}4.8%$ (p=0.042), $84.5{\pm}5.1%$ (p<0.001) at the same follow up period respectively. Significant improvement of symptom was observed at 3 months after RF myolysis. Transient low abdominal pain and prolonged vaginal bleeding were detected in 3 patients each but spontaneously resolved and no serious complication has been noticed or found. Conclusion: This study shows transvaginal RF myolysis could be a safe and effective method to treat uterine leiomyoma, allowing uterine conservation with significant volume reduction and rapid return to normal activity.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.3
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• pp.17-22
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• 2018

This study suggests that 'Will not we use more smartphones while watching TV commercials? Then, will the TV advertising effect decrease due to the distributed concentration?". As a result of the preliminary study, it was confirmed that about 63% of users watching TV commercials use smartphones together. In this study, we propose the possibility of a new mobile advertising service by experimenting and analyzing the effect of high frequency technology based TV advertising linked mobile advertising service. Experimental results show that the response rate of the same content is improved about 9 times as compared with that of the general mobile advertisement when the advertisement of the same content is provided by the TV advertisement interlocking type. It can be confirmed that it is quite effective to provide the same content advertisement to the customers who are in front of the TV at the time of sending the TV advertisement. Therefore, it is expected that various services based on high frequency technology will be activated as a new advertising service that will preserve the effect of TV commercials in the future.

• Resources Recycling
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• v.21 no.3
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• pp.48-55
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• 2012

Recently, the recycling with environmentally friendly method has been an issue for various fields. An effective removal method of coating layers from coated copper wires is one critical factor for recycling copper wire. We have adopted a high frequency heating routine for removing the coating layers on the coated copper wires, and attempted to find optimum conditions. The experimental results show that the copper wires should be maintained at or above $950^{\circ}C$ for rapid removal of the polyester. The simulation and experimental results are discussed with respect to the microstrucrual evolution during heating of the copper wires.

• 전기의세계
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• v.41 no.2
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• pp.47-54
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• 1992

본 고에서는 반도체 자기센서에 이용되는 기본 원리인 Hall효과, 실리콘을 이용한 자기센서의 종류 및 동작 원리, 그리고 용도 등에 대해서 간략히 기술하였다. 많은 자기센서들 중에서 어느 것이 가장 좋은가는 간단히 결정되어질 수 없으며 특정한 응용에 따른 요구조건에 따라 달라지게 된다. 높은 민감도를 요구하거나 저주파 영역에서의 잡음 등이 문제가 되는 경우에는 magnetotransistor가 유리하고, 고주파 영역에서의 잡음, offset, 선형성이나 온도 보상등의 면에서는 Hall Plate가 유리하다고 할 수 있다. 또한 대단히 낮은 전류에서는 높은 민감도를 얻기 위해서는 Split-Drain type MAGFET이 가장 유리하다.

• Journal of the Korea Organic Resources Recycling Association
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• v.8 no.3
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• pp.97-103
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• 2000

This study was performed to prove that vitrified slag can be utilized as sound absorbing materials by investigating on heavy metal elution and the properties of sound absorbing rate according to the thickness. The heavy metal elution experiment indicated that heavy metal was not eluted since it was fixed stable in the slag. Vitrified slag generally exhibited a maximum sound absorbing rate around at 600Hz-1kHz and 3kHz in the low and high frequency range, respectively. On the other hand, the absorbing rate increased beyond the range of 7kHz again. The sound absorbing rate varied a little according to the thickness of the material. However, Vitrified slag is likely to the effective as a sound absorbing wall material since it has a sound absorbing rate clover 80% in the low and high frequency region when used as a wall. The results obtained in this study showed that vitrified slag has the recyclable material properties and therefore, highly applicable to sound absorbing materials.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.8
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• pp.798-804
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• 2013

In this paper, conducted emission from the LDC(Low-Side DC/DC Converter) of a HEV/EV was analyzed using high-frequency circuit modeling in system-level approach. The conducted emission by PWM process(100 kHz; Switching Frequency) can cause RFI(Radio-Frequency Interference) problems in the AM/FM frequency range. In order to mitigate this conducted emission, a high-frequency equivalent circuit model is proposed by analyzing the fundamental circuits, parasitic components in their parts and connections and non-linear characteristics of MOSFETs, high-power capacitors, inverters, motors, high-power cables, and bus bars which are composed of the LDC. Using these circuit models, results of both simulation and measurement were compared and similarities between them were verified. We are looking forward that this approach can be effectively used in the EMC design of HEV/EV.

• Journal of Korea Multimedia Society
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• v.10 no.8
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• pp.958-966
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• 2007

In this paper, we implement a sound-enhanced MPEG-1 audio decoder on embedded OS Platform. Low bit rate lossy audio codecs such as MP3, OGG, and AAC for mitigating the problems in storage space and network bandwidth suffer a major common problem such as a loss of high frequency fidelity of audio signal. This high frequency loss will reproduce only a band-limited low-frequency part of audio in the standard CD-quality audio. In order to overcome this problem, we embedded a sound enhancement algorithm into the MPEG-1 audio decoder and then the algorithms optimized according to the characteristic of the MPEG-1 audio layer I, II, III were implemented on an embedded OS platform. From the experimental results with spectrum analysis and listening test, we confirm the superiority of the proposed system compared to the standard MPEG-1 audio decoder.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.2
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• pp.74-83
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• 1997

The definition of burning admittance and conventional n-$\tau$ stability rating technique are combined to investigate the high frequency combustion instabilities inside the cylindrical combustion chamber. Perturbed flow variables are written as the sum of fluctuating and time-averaged mean quantities on the assumption that the terms of the order higher than unity are sufficiently small, hence linearized governing equations could be formulated. Chamber admittances up and downstream of the flame front calculated with appropriate boundary conditions result in the burning admittance and corresponding n-$\tau$ neutral stability curve. Configurational and operational design factors are tested to detect the unstable wave-induced LOX-RP1 combustion instabilities. Operational design factors, e.g. pressure or O/F ratio, appear less influential to drive high frequency instability while the location of the flame front and configurational factors enhance or deteriorate the stabilities strongly. Conclusively, LOX-RP1 combustion inside the cylindrical combustion chamber is apt to be unstable against long residence time and shortened chamber length.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.6
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• pp.867-873
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• 2018

Recently, interests in the field of image processing have increased with the increased demand for digital imaging devices. However, digital images are damaged by the noise generated by various causes during image processing. Generally in digital imaging devices, noise such as AWGN, etc. is generated and performance and reliability are deteriorated, and various researches are in progress to remove it. Accordingly in the present paper, an algorithm to protect the high frequency components of the images and to efficiently remove AWGN is proposed. The proposed algorithm calculates the final output by adjusting estimate values applied with Gaussian mask and weight values applied according to the local mask distribution. And for performance evaluation of the proposed algorithm, simulations were performed with the existing methods, and the characteristics were compared through PSNR and the processed, enlarged images.