• Wind and Structures
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• v.11 no.5
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• pp.361-376
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• 2008

This paper considers internal pressure fluctuations for a range of building volumes and dominant wall opening areas. The study recognizes that the air flow in and out of the dominant opening in the envelope generates Helmholtz resonance, which can amplify the internal pressure fluctuations compared to the external pressure, at the opening. Numerical methods were used to estimate fluctuating standard deviation and peak (i.e. design) internal pressures from full-scale measured external pressures. The ratios of standard deviation and peak internal pressures to the external pressures at a dominant windward wall opening of area, AW are presented in terms of the non-dimensional opening size to volume parameter, $S^*=(a_s/\bar{U}_h)^2(A_W^{3/2}/V_{Ie})$ where $a_s$ is the speed of sound, $\bar{U}_h$ is the mean wind speed at the top of the building and $V_{Ie}$ is the effective internal volume. The standard deviation of internal pressure exceeds the external pressures at the opening, for $S^*$ greater than about 0.75, showing increasing amplification with increasing $S^*$. The peak internal pressure can be expected to exceed the peak external pressure at the opening by 10% to 50%, for $S^*$ greater than about 5. A dominant leeward wall opening also produces similar fluctuating internal pressure characteristics.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.967-970
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• 2003

A new modified singular value decomposition method, piecewise polynomial truncated SVD (PPTSVD), which was originally developed to identify discontinuity of the earth's radial density function, has been used for large solvent peak suppression and noise elimination in nuclear magnetic resonance (NMR) signal processing. PPTSVD consists of two algorithms of truncated SVD (TSVD) and L₁ problems. In TSVD, some unwanted large solvent peaks and noise are suppressed with a certain soft threshold value, whereas signal and noise in raw data are resolved and eliminated in L₁ problems. These two algorithms were systematically programmed to produce high quality of NMR spectra, including a better solvent peak suppression with good spectral line shapes and better noise suppression with a higher signal to noise ratio value up to 27% spectral enhancement, which is applicable to multidimensional NMR data processing.

• Current Optics and Photonics
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• v.6 no.3
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• pp.252-259
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• 2022

In this paper, a dual-function dynamically tunable metamaterial absorber is proposed. At frequency points of 1.545 THz and 3.21 THz, two resonance peaks with absorption amplitude of 93.8% (peak I) and 99.4% (peak II) can be achieved. By regulating the conductivity of photosensitive silicon with a pump laser, the resonance frequency of peak I switches to 1.525 THz, and that of peak II switches to 2.79 THz. By adjusting the incident polarization angle by rotating the device, absorption amplitude tuning is obtained. By introducing two degrees of regulation freedom, the absorption amplitude modulation and resonant frequency switching are simultaneously realized. More importantly, dynamic and continuous adjustment of the absorption amplitude is obtained at a fixed resonant frequency, and the modulation depth reaches 100% for both peaks. In addition, the sensing property of the proposed MMA was studied while it was used as a refractive index sensor. Compared with other results reported, our device not only has a dual-function tunable characteristic and the highest modulation depth, but also simultaneously possesses fine sensing performance.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.16-17
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• 2010

Molecular spintronics has attracted attentions, which combines molecular electronics with the spin degree of freedom in electron transport. Among various molecules as candidates of the molecular spintronics, single molecule magnet (SMM) is one of the most promising material. SMM molecules show a ferromagnetic behavior even as a single molecule and hold the spin information even after the magnetic field is turned off. Here in this report, we show the spin behavior of SMM molecules adsorbed on the Au surface by combining the observation of Kondo peak in the STS and ESR-STM measurement. Kondo resonance state is formed near the Fermi level when degenerated spin state interacts with conduction electrons. ESR-STM detects the Larmor frequency of the spin in the presence of a magnet field. The sample include $MPc_2$ and $M_2Pc_3$ molecules ($M\;=\;Tb^{3+}$, $Dy^{3+}$, and $Y^{3+}$ Pc=phthalocyanine) whose critical temperature as a ferromagnet reaches 40 K. A clear Kondo peak was observed which is originated from an unpaired electron in the ligand of the molecule, which is the first demonstration of the Kondo peak originated from electron observed in the STS measurement. We also observed corresponding peaks in ESR-STM spectra. [1] In addition we found that the Kondo peak intensity shows a clear variation with the conformational change of the molecule; namely the azimuthal rotational angle of the Pc planes. This indicates that the Kondo resonance is correlated with the molecule electronic state. We examined this phenomena by using STM manipulation technique, where pulse bias application can rotate the relative azimuthal angle of the Pc planes. The result indicates that an application of ~1V pulse to the bias voltage can rotate the Pc plane and the Kondo peaks shows a clear variation in intensity by the molecule's conformational change.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.12
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• pp.5085-5088
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• 2015

Background: The aim of this study was to assess the role of the presence of a choline peak in 3 Tesla 1H magnetic resonance spectroscopy (MRS) for differentiating benign from malignant adnexal masses. Materials and Methods: A total of 46 adnexal masses (23 malignant and 23 benign) underwent 1H MRS study prior to surgery to assess the presence of choline peak. Results: A choline peak was detected in 16 malignant masses (69.5%) and was absent in the other 7 (30.5%). A choline peak was only detected in 6 (26%) of the benign adnexal masses. The presence of an MRS choline peak had a sensitivity of 69.5%, a specificity of 74%, a positive predictive value (PPV) of 72.7%, and a negative predictive value (NPV) of 71% for diagnosing malignant adnexal masses. A significant difference between the frequency of mean choline peaks in benign and malignant adnexal masses was observed (P value < 0.01). Conclusions: A 1H MRS choline peak is seen in malignant adnexal masses more frequently than the benign masses, and may be helpful for diagnosing malignant adnexal masses.

• Journal of Veterinary Science
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• v.22 no.1
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• pp.2.1-2.10
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• 2021

Background: Diseases related to cerebrospinal fluid flow, such as hydrocephalus, syringomyelia, and Chiari malformation, are often found in small dogs. Although studies in human medicine have revealed a correlation with cerebrospinal fluid flow in these diseases by magnetic resonance imaging, there is little information and no standard data for normal dogs. Objectives: The purpose of this study was to obtain cerebrospinal fluid flow velocity data from the cerebral aqueduct and subarachnoid space at the foramen magnum in healthy beagle dogs. Methods: Six healthy beagle dogs were used in this experimental study. The dogs underwent phase-contrast and time-spatial labeling inversion pulse magnetic resonance imaging. Flow rate variations in the cerebrospinal fluid were observed using sagittal time-spatial labeling inversion pulse images. The pattern and velocity of cerebrospinal fluid flow were assessed using phase-contrast magnetic resonance imaging within the subarachnoid space at the foramen magnum level and the cerebral aqueduct. Results: In the ventral aspect of the subarachnoid space and cerebral aqueduct, the cerebrospinal fluid was characterized by a bidirectional flow throughout the cardiac cycle. The mean ± SD peak velocities through the ventral and dorsal aspects of the subarachnoid space and the cerebral aqueduct were 1.39 ± 0.13, 0.32 ± 0.12, and 0.76 ± 0.43 cm/s, respectively. Conclusions: Noninvasive visualization of cerebrospinal fluid flow movement with magnetic resonance imaging was feasible, and a reference dataset of cerebrospinal fluid flow peak velocities was obtained through the cervical subarachnoid space and cerebral aqueduct in healthy dogs.

• Journal of the Korean Magnetic Resonance Society
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• v.22 no.2
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• pp.40-45
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• 2018

We report Optically-Detected Magnetic Resonance (ODMR) study on Nitrogen-Vacancy (NV) centers in diamond. The experiment can easily be conducted with basic optics and microwave components. A diamond crystal having a high-density NV center is suitable for the ODMR study. The magnetic field dependence of ODMR spectrum allowed us to determine the orientation of the diamond crystal. In addition, we measured the variation of the ODMR spectrum as a function of the excitation laser power. Thermal heating induced by optical absorption caused the monotonic decrease of zero field splitting. The contrast of the ODMR peak, however, increased and, then, began to decrease, indicating the optimal laser power for recording the ODMR spectrum.

• Journal of the Korean Magnetic Resonance Society
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• v.22 no.2
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• pp.34-39
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• 2018

The Nuclear Magnetic Resonance (NMR) technique using Dynamic Nuclear Polarization (DNP) procedures is one of the promising techniques that enable overcoming low sensitivity problems in NMR spectroscopy. We constructed an ODNP-NMR system using a commercial benchtop EPR spectrometer. The $^1H$ NMR peak area of water in aqueous solutions of 4-hydroxy-TEMPO was enhanced more than 95 times in the ODNP-NMR experiments. Our signal enhancement results were about 55% of the previously reported result. This could be due to non-uniform microwave power over a sample and unwanted sample heating by microwave. However, this portable ODNP-NMR spectrometer will be eventually useful for site-specific detection with nano-scale spatial resolutions and molecular dynamics studies with significantly improved signal sensitivity.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.734-739
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• 1994

Elastic wave propagation in discrete random medium is studied to evaluate the effects of particle resonance on dispersion and attenuation of composite materials containing spherical inclusions. The frequency-dependent wave speed and attenuation coefficient can be obtained from proposed self-consistent method. It can be observed that the abrupt increase of effective wave speed and the concurrent peak of attenuation at low frequency is due to the lowest resonance of particles, whereas those in high frequency region are due to higher ones. The lowest resonance is mainly caused by the density mismatch and higher resonances by the stiffness mismatch between matrix and particles. The dispersion and attenuation of elastic waves in particulate composites are affected by the lowest resonance much than by higher ones.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.614-624
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• 2013

The resonance power buoy is a convincing tool that can increase the extraction efficiency of wave energy. The buoy needs a corresponding draft, to move in resonance with waves within the peak frequency band where wave energy is concentrated. However, it must still be clarified if the buoy acts as an effective displacement amplifier, when there is insufficient water depth. In this study, the vertical displacement of a circular cylinder-type buoy was calculated, with the spectrum data observed in a real shallow sea as the external wave force, and with the corresponding draft, according to the mode frequency of normal waves. Such numerical investigation result, without considering Power Take-Off (PTO) damping, confirmed that the area of the heave responses spectrum can be amplified by up to about tenfold, compared with the wave energy spectrum, if the draft corresponds to the peak frequency, even with insufficient water depth. Moreover, the amplification factor of the buoy varied, according to the seasonal changes in the wave spectra.