• Korean Journal of Audiology
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• v.18 no.3
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• pp.105-111
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• 2014

Assistive listening devices (ALDs) refer to various types of amplification equipment designed to improve the communication of individuals with hard of hearing to enhance the accessibility to speech signal when individual hearing instruments are not sufficient. There are many types of ALDs to overcome a triangle of speech to noise ratio (SNR) problems, noise, distance, and reverberation. ALDs vary in their internal electronic mechanisms ranging from simple hard-wire microphone-amplifier units to more sophisticated broadcasting systems. They usually use microphones to capture an audio source and broadcast it wirelessly over a frequency modulation (FM), infra-red, induction loop, or other transmission techniques. The seven types of ALDs are introduced including hardwire devices, FM sound system, infra-red sound system, induction loop system, telephone listening devices, television, and alert/alarm system. Further development of digital wireless technology in hearing instruments will make possible direct communication with ALDs without any accessories in the near future. There are two technology solutions for digital wireless hearing instruments improving SNR and convenience. One is near-field magnetic induction combined with Bluetooth radio frequency (RF) transmission or proprietary RF transmission and the other is proprietary RF transmission alone. Recently launched digital wireless hearing aid applying this new technology can communicate from the hearing instrument to personal computer, phones, Wi-Fi, alert systems, and ALDs via iPhone, iPad, and iPod. However, it comes with its own iOS application offering a range of features but there is no option for Android users as of this moment.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1498-1499
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• 1998

Thin film inductors of 10 mm ${\times}$ 10 mm with spiral pattern of 14 turns were fabricated by sputtering, photo-masking, and etching processes. Their impedence characteristics and annealing after effects were investigated. After magnetic annealing, the impedence characteristics of the inductors were improved at comparatively low frequencies, but the tendencies of it for thr frequency changes were almost same. These improvement was caused by the annihilation of the internal stresses of films, Uniaxial field annealed thin film inductor had an inductance of 1000 nH, resistance of 6 $\Omega$, and quality factor of 1 at 2 MHz.

• ETRI Journal
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• v.28 no.1
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• pp.107-110
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• 2006

The dimensions of the human body vary by age, sex, and race. The internal structure and outer dimensions of a body exposed to an electromagnetic field is important for accurate dosimetry. The average physical size of Korean adult males between the ages 18 to 24 was investigated, and a male volunteer was selected whose physical condition is within the physical standards, ${\pm}5%$. Magnetic resonance images and partially computerized tomography images of the volunteer were acquired. The intervals between the transverse images were 1 mm for the head and 3 mm for the rest of the body. About 30 different tissues were manually classified by an anatomist on the raw images, and the segmented images were implemented in the form of a text file appropriate for numerical formulation.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.58.3-59
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• 2017

The JCMT is now in its third year of operations under EAO management. During this past year, we continued with calls for regular PI programs as well as the second call for Large Programs. The performance of SCUBA-2 has been improved by replacing internal optical filters. The 230GHz Receiver A is in the process of being replaced by a new closed-cycle system. The SCUBA-2 polarimeter, POL-2, commissioned during the past year, has been working very well in measuring the magnetic field structures in molecular clouds. The JCMT successfully participated in the Event Horizon Telescope experiment during April 2017, which utilized the phased-up ALMA for the first time. The first round of Large Programs are nearing completion, with first publications beginning to be published. The JCMT continues to welcome inputs from the community, and the next users meeting will be held in Seoul in January 2018.

• Journal of applied mathematics & informatics
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• v.11 no.1_2
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• pp.1-57
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• 2003

Vector fields in three-space admit bundles of internal variables such as a Heisenberg algebra bundle. Information transmission along field lines of vector fields is described by a wave linked to the Schrodinger representation in the realm of time-frequency analysis. The preservation of local information causes geometric optics and a quantization scheme. A natural circle bundle models quantum information visualized by holographic methods. Features of this setting are applied to magnetic resonance imaging.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.419-422
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• 1998

This paper presents how to design speed control of wound rotor induction motors with slip energy recovery. The speed is limited at some range of sub-synchronous speed of the rotating magnetic field. The problem with speed control by adjusting resistance value in the rotor circuit reduces the efficiency of power, because of the slip energy is lost when it passes through the rotor resistance. The control system is designed to maintain efficiency of motor, where it recovers loss energy by returning it to the system to improve the efficiency. A new PI control method of adaptive control [1］,［13］is applied for the system with cascade type PI controller on the main loop to keep the speed constant and the internal loop to adjust the rotor appropriated current of the load provides the good transient response without overshoot.

• Journal of the Korean Magnetics Society
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• v.6 no.4
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• pp.264-271
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• 1996

A magnetically shielded room has been constructed for biomagnetic applications. The room has internal dimensions of $2\;m(length){\times}2\;m(width){\times}2.5\;m(height)$ and it consists of high permeability Mumetal and high conductivity alummum, utilizing ferromagnetic shielding and eddy current shielding. The de shielding factor around the center of the room is above 60 dB, and the ac shielding factors at 1 and 10 Hz are larger than 60 and 80 dB, respectively. The internal magnetic field noise at 1 Hz is $500\;fT/{\sqrt}Hz$ and at 10 Hz is $100\;fT/{\sqrt}Hz$, and the field gradient noise at 1 Hz is below $7\;fT/cm{\sqrt}Hz$. Successful measurements of cardiomagnetic fields usmg SQUID magnetometer and neuromagnetic fields using SQUID gradiometer have been done.

• The Journal of the Korea Contents Association
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• v.10 no.9
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• pp.302-308
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• 2010

In MRI, the Ferromagnetic artifact is generated by the metalization within in which the before inspection removal is impossible and the distortion of an image is brought. The distortion measure according to the steel for each sequence of T1 image and magnetic field intensity are analyzed and minimized method is looked into. We used SIEMENS 1.5T and 3.0T MRI for experiment equipment. First, it places within the Phantom making a metalization(Ti+Al, Stainless, Nitinol) on 1.5T, 3.0T MRI and the T1 weighted image for each Sequence is acquired. The distortion of an image and about adjacent portion change of the metal material were compared through the obtained image, we analyzed. In all metalizations, a distortion was generated and a distortion was few in particularly, and Titanium-Aluminium alloy. And the extent of a distortion was worse image in the Turbo spin Echo. The use of the Titanium-Aluminium alloy the inserted in an internal material of the metalization is recommend. and, equipment of 1.5T the patient inserting a metal in an internal is used in an inspection than equipment of 3.0T. Also, the sequence is suitable when it obtains the optimum T1 weighted image of an impersonate to use the Turbo spin Echo.

• The Korean Journal of Physiology and Pharmacology
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• v.15 no.3
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• pp.137-142
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• 2011

Extremely low frequency magnetic fields (ELF-MF) have the ability to produce a variety of behavioral and physiological changes in animals. The stomach, as the most sensitive part of the neuroendocrine organ of the gastrointestinal tract, is crucial for the initiation of a full stress response against all harmful stress. Thus, the purpose of this study was to examine whether ELF-MF stimuli induce changes in the activity of neuroendocrine cells, considering their involvement in endocrine or paracrine effect on surrounding cells. The exposure to ELF-MF (durations of 24 h and 1 or 2 weeks, 60 Hz frequency, 0.1 mT intensity) altered the distribution and occurrence of gastrin, ghrelin and somatostatinpositive endocrine cells in the stomach of rats. The change, however, in the secretion of those hormones into blood from endocrine cells did not appear significantly with ELF-MF exposure. Comparing with sham control, ELF-MF exposure for 1 and 2 week induced an increase in $BaSO_4$ suspension propelling ratio of gastrointestinal tract, indicating that ELF-MF affects gastrointestinal motility. Our study revealed that ELF-MF exposure might influence the activity of endocrine cells, an important element of the intrinsic regulatory system in the digestive tract. The pathophysiological character of these changes and the mechanism responsible for neuroendocrine cell are still unclear and require further studies.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.8
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• pp.583-593
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• 2018

Lightning causes physical damage to aircraft, such as melting, burning and arcing, and magnetic field that occurs on the aircraft's outer body during the penetration of a lightning stroke causes voltage and current transients in the electronics and wiring within the aircraft. This effect will cause induced lightning strikes in the aircraft's internal airborne electronic systems, preventing safe flight. This paper introduces protection circuit design techniques, and the test results that meet the requirements for certification of criteria.