• The Journal of the Acoustical Society of Korea
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• v.31 no.8
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• pp.507-513
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• 2012

The room modes were showed as the peaks and dips on the low frequency response of the loudspeaker, and were one of the biggest obstacles to reproduce the sound. In order to reduce the occurrence of resonance, equalizing is performed at one position, and the frequency response to be equalized is valid only at that position. Performing the equalization would improve the flatness of the frequency response a little, but it cannot eliminate the ringing. Another method is that it is located the speaker at the specific position where the room resonances were not frequently happened. However, there may be the practical limitation that you may not be able to install the speaker at the position to be wanted. One of the practical solutions to decrease the production of resonance in room is the use of bass trap. In this paper, the practical limit for the room tuning using an equalizer and the room optimization will be discussed. The use of bass traps to solve the resonance problem that is always happened in the room is also proposed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.12
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• pp.897-901
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• 2010

A silencer has been widely used for the purpose of suppressing the noises propagated from duct of air conditioning system. The absorption type silencer is usually applied to reduce the noise with high frequency bandwidth. On the order hand, the resonance type silencer is applied to reduce the noise with low-middle frequency bandwidth. The insertion loss of silencer is measured in the reverberation room. The cut-off frequency of reverberation room is 100 Hz. The insertion loss of absorption type silencer is more larger than that for resonance type silencer regardless of changing the flow velocity.

• Journal of the Korean Magnetic Resonance Society
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• v.3 no.2
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• pp.109-126
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• 1999

The location of Cu(II) exchanged into measoporous aluminosilicate MCM-41(AlMCM-41) material and its interaction with various adsorbate molecules were investigated by electron spin resonance and electron spin echo modulation spectroscopies. Cu(II) is fully coordinated to adsorbates in a wide open mesopore of AlMCM-41 for the formation of favorable complexes. It was found that in the fresh hydrated material, Cu(II) is octahedrally coordinated to six water molecules as evidenced by an isotropic room temperature ESR signal. This species is located in a cylindrical MCM-41 channel and rotates rapidly at room temperature. Evacuation at room temperature removes some of these water molecules, leaving the Cu(II) coordinated to less water molecules and anchored to oxygens in an MCM-41 channel wall. Dehydration at 450$^{\circ}C$ produces one Cu(II) species located on the internal wall of a channel, which is easily accessible to adsorbates. Adsorption of adsorbate molecules such as water, methanol, ammonia, pyridine, aniline, acetonitrile, benzene, and ethylene on a dehydrated Cu-AlMCM-41 material causes changes in the ESR spectrum of Cu(II), indicating the complex formation with these adsorbates. Cu(II) forms a complex with six molecules of methanol as evidenced by an isotropic room temperature ESR signal and ESEM analysis like upon water adsorption. Cu(II) also forms a square planar complex containing four molecules of N-containing adsorbates such as ammonia, pyridine and aniline based on resolved nitrogen superhyperfine interaction and their ESR parameters. However, Cu(II) forms a complex with six-molecules of acetonitrile based on ESR parameters. Only one molecule of benzene or ethylene is coordinated to Cu(II).

• Investigative Magnetic Resonance Imaging
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• v.20 no.3
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• pp.152-157
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• 2016

Purpose: Operating room management is the serious and complex task for hospital managers and the common approach is to develop relevant standard operational procedures. From patient and staff safety perspective, operating room management should be well-studied and hospital should identify and address any potential risks. Simultaneous usage of different imaging and less-invasive treatment technologies demands strong management control. Materials and Methods: We have formed the multidisciplinary expert panel (surgeons, anesthesiologists, radiologists, healthcare managers etc.) for hybrid theater management standard operational procedure development. On the first stage the general concept of hybrid room design and patient routing was developed. The second stage included the technical details discussion. For patient safety improvement we modified the Surgical Safety Check-list in accordance with potential MRI-related safety challenges and concerns. Results: WHO Surgical Safety Checklist is a simple and easy-to use tool which includes three blocks of question (grouped by the surgery process). We have developed two additional blocks of questions for the intraoperative magnetic resonance investigation. It is very important to have a special detailed routing with a strong control of ferromagnetic devices and anesthesiology care. Conclusion: High-energy MRI (1.5-3.0T) is characterized by potential influence on patient and staff safety in case of hybrid surgery. It is obvious to have a strong managerial control of ferromagnetic devices and anesthesiology care. Surgical Safety Checklist is the validated tool for improving patient safety. Modification and customization of this check-list potentially provides the opportunity for surgery processes improving.

• Journal of the Korean Magnetic Resonance Society
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• v.1 no.2
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• pp.126-140
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• 1997

Mesoporous MCM-41 gallosilicate material was synthesized through shifting through shifting gallosilicate polymer equilibrium towards a MCM-41 phase by addition of acid. The location of Cu(II) exchanged into MCM-41 and its interaction with various adsorbate molecules were investigated by electron spin responance and electron spin echo modulation spectroscopies. It was found that in the fresh hydrated material, Cu(II) is octahedrally coordinated to six water molecules. This species is located in a cylindrical channel and rotates rapidly at room temperature. Evacuation at room temperature removes three of these water molecules, leaving the Cu (II) coordinated to three water molecules and anchored to oxygens in the channel wall. Dehydration at 45$0^{\circ}C$ produces one Cu (II) species located in the inner surface of a channel as evidenced by broadening of its ESR lines by oxygen. Adsorption of polar molecules such as water, methanol and ammonia on dehydrated CuNa-MCM-41 gallosilicate material causes changes in the ESR spectrum of Cu (II), indicating the complex formation with these adsorbates. Cu (II) forms a complex with six molecules of methanol as evidenced by an isotropic room temperature ESR signal and ESEM data like upon water adsorption. Cu(II) also forms a complex containing four molecules of ammonia based on resolved nitrogen superhyperfine interaction.

• Journal of the Korean Chemical Society
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• v.15 no.4
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• pp.177-181
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• 1971

Free radicals of lysozyme produced by $Ti-H_2O_2$ system were studied in aqueous solution at room temperature using ESR with a continuous flow-mixing. The spectra, each consisting of a doublet with 5.5 G splitting and a broad resonance covering 80 G splitting are closely similar in shape to that for solid irradiated in vacuum at $77^{\circ}K$ and observed at room temperature immediately on warming. The result is assumed to indicate that the secondary protein radical components formed within 0.01 second, dead time of the mixing chamber, and initiated by hydrogen atom abstraction at ${\alpha}$-carbon atom of peptide chain in liquid solution at room temperature are identical to those resulting from the initial formation of a mixture of positive holes and negative ions by ionization processes as well as radical fragments by the rupture of chemical bonds in the solid during similar time at the same temperature. A broad resonance is observed with considerable amplitude on the high field side of the doublet, which is quite dissimilar to the spectra of irradiated solid lysozyme. This resonance was tentatively attributed to the polypeptide free radical in which unpaired electrons are localized on side chain.

• Special Issue of the Society of Naval Architects of Korea
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• 2013.12a
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• pp.55-59
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• 2013

Transverse vibrations of ship's aft end and deckhouse among the various modes of hull structures are induced mainly by transverse exciting forces and moments of main engine such as ${\times}$ and h-moment. Avoidance of resonance should be made in a intial design stage in case there is a prediction for resonance between main engine and transverse modes of deckhouse. This study shows a case of change in type of main engine from 12 cylinders to 10 without modification of hull structures in engine room requested by a shipowner of 8,600 TEU class container carrier and proposes a guide to the effective ways of structural arrangement for avoiding resonance between transverse exciting force and surrounding structures of main engine in engine room through case studies.

• Journal of Magnetics
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• v.20 no.3
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• pp.295-301
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• 2015

We evaluated certain issues related to magnetic resonance imaging (MRI) coupled with the use of active 2.5 GHz radio frequency identification (RFID) tags for patient identification using low field (0.3 T) MRI and computed tomography (CT) scans. We also investigated the performance of the RFID reader located outside the MRI room by considering several factors. A total of ten active RFID tags were exposed to several MRI sequences and X-rays of CT scan. We found that only card type active RFID tags are suitable for patient identification purpose in MRI environment and both wristbands as well as card tags were suitable for the same in CT environment. Severe artifacts were found in the captured MRI and CT images when the area of the imaging was in proximity to the tags. No external factors affected the performance of active RFID reader stationed outside the MRI scan room.

• Investigative Magnetic Resonance Imaging
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• v.23 no.3
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• pp.202-209
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• 2019

Purpose: To investigate the temperature-based differences of cortical bone ultrashort echo time MRI (UTE-MRI) biomarkers between body and room temperatures. Investigations of ex vivo UTE-MRI techniques were performed mostly at room temperature however, it is noted that the MRI properties of cortical bone may differ in vivo due to the higher temperature which exists as a condition in the live body. Materials and Methods: Cortical bone specimens from fourteen donors ($63{\pm}21$ years old, 6 females and 8 males) were scanned on a 3T clinical scanner at body and room temperatures to perform T1, $T2^*$, inversion recovery UTE (IR-UTE) $T2^*$ measurements, and two-pool magnetization transfer (MT) modeling. Results: Single-component $T2^*$, $IR-T2^*$, short and long component $T2^*s$ from bi-component analysis, and T1 showed significantly higher values while the noted macromolecular fraction (MMF) from MT modeling showed significantly lower values at body temperature, as compared with room temperature. However, it is noted that the short component fraction (Frac1) showed higher values at body temperature. Conclusion: This study highlights the need for careful consideration of the temperature effects on MRI measurements, before extending a conclusion from ex vivo studies on cortical bone specimens to clinical in vivo studies. It is noted that the increased relaxation times at higher temperature was most likely due to an increased molecular motion. The T1 increase for the studied human bone specimens was noted as being significantly higher than the previously reported values for bovine cortical bone. The prevailing discipline notes that the increased relaxation times of the bound water likely resulted in a lower signal loss during data acquisition, which led to the incidence of a higher Frac1 at body temperature.

• Korean Journal of Radiology
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• v.20 no.6
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• pp.1001-1002
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• 2019