• Journal of the Mineralogical Society of Korea
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• v.24 no.4
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• pp.301-312
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• 2011

The study on the atomic structure of iron-bearing silicate glasses has significant geological implications for both diverse igneous processes on Earth surface and ultra-low velocity zones at the core-mantle boundary. Here, we report experimental results on the effect of iron content on the atomic structure in iron-bearing alkali silicate glasses ($Na_2O-Fe_2O_3-SiO_2$ glasses, up to 16.07 wt% $Fe_2O_3$) using $^{29}Si$ and $^{17}O$ solid-state NMR spectroscopy. $^{29}Si$ spin-lattice ($T_1$) relaxation time for the glasses decreases with increasing iron content due to an enhanced interaction between nuclear spin and unpaired electron in iron. $^{29}Si$ MAS NMR spectra for the glasses show a decrease in signal intensity and an increase in peak width with increasing iron content. However, the heterogeneous peak broa-dening in $^{29}Si$ MAS NMR spectra suggests the heterogeneous distribution of $Q^n$ species around iron in iron-bearing silicate glasses. While nonbridging oxygen ($Na-O-Si$) and bridging oxygen (Si-O-Si) peaks are partially resolved in $^{17}O$ MAS NMR spectrum for iron-free silicate glass, it is difficult to distinguish the oxygen clusters in iron-bearing silicate glass. The Lorentzian peak shape for $^{29}Si$ and $^{17}O$ MAS NMR spectra may reflect life-time broadening due to spin-electron interaction. These results demonstrate that solid-state NMR can be an effective probe of the detailed structure in iron-bearing silicate glasses.

• Progress in Medical Physics
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• v.24 no.2
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• pp.108-118
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• 2013

Currently, an arterial spin labeling (ASL) magnetic resonance imaging (MRI) technique does not routinely used in clinical studies to measure perfusion in brain because optimization of imaging protocol is required to obtain optimal perfusion signals. Therefore, the objective of this study was to investigate changes of perfusion-weighed signal intensities with varying several parameters on a pulsed arterial spin labeling MRI technique obtained from a 3T MRI system. We especially evaluated alternations of ASL-MRI signal intensities on special brain areas, including in brain tissues and lobes. The signal targeting with alternating radiofrequency (STAR) pulsed ASL method was scanned on five normal subjects (mean age: 36 years, range: 29~41 years) on a 3T MRI system. Four parameters were evaluated with varying: 1) the labeling gap, 2) the labeling delay time, 3) the labeling thickness, and 4) the slice scan order. Signal intensities were obtained from the perfusion-weighted imaging on the gray and white matters and brain lobes of the frontal, parietal, temporal, and occipital areas. The results of this study were summarized: 1) Perfusion-weighted signal intensities were decreased with increasing the labeling gap in the bilateral gray matter areas and were least affected on the parietal lobe, but most affected on the occipital lobe. 2) Perfusion-weighted signal intensities were decreased with increasing the labeling delay time until 400 ms, but increased up to 1,000 ms in the bilateral gray matter areas. 3) Perfusion-weighted signal intensities were increased with increasing the labeling thickness until 120 mm in both the gray and white matter. 4) Perfusion-weighted signal intensities were higher descending scans than asending scans in both the gray and white matter. We investigated changes of perfusion-weighted signal intensities with varying several parameters in the STAR ASL method. It should require having protocol optimization processing before applying in patients. It has limitations to apply the ASL method in the white matter on a 3T MRI system.

• Progress in Medical Physics
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• v.1 no.1
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• pp.31-42
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• 1990

The finding of long lived free radicals produced by ionizing radiation in organic crystals and the quantification of this effect by electron spin resonance(ESR) spactroscopy has proven excellent dosimetric applicability. The tissue equivalent alanine dosimeter also appear appropriate for radiation therapy level dosimetry. The dose measurement was performed in a Rando phantom using high energy photons as produced by high energy medical linear accelerator and cobalt-60 teletherapy unit. The absorbed dose range of the ESR/alanine dosimetry system could be extended down to 0.1 Gy. The response of the alanine dosimeters was determined for photons at different therapeutic dose levels from less than 0.1 Gy to 100 Gy and the depth dose measurements were carried out for photon energies of 1.25MeV, 6 and 10 MV with alanine dosimeters in Rando phantom. Comparisons between ESR/alanine in a Rando phantom and ion chamber in a water phantom were made performing depth dose measurements to examine the agreement of both methods under field conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.692-697
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• 2005

A canard type aircraft, which has good wing stall and stall/spin proof characteristics, is being developed. The previous first and second prototypes, having full depth core sandwich type wing and fixed landing gear, was built for test flights. Newly developing Firefly will be equipped with retractable landing gear and conventional foam core sandwich laminate for wing and fuselage. For manufacturing, composite material process has been studied including coupon tests. Wet lay-up onto foam core with glass fabric using lay-up mold has been chosen, and composite material parts are cured under room temperature and atmospheric pressure condition. In general, molded parts show so good surface smoothness and standardized quality that are best in mass production. In this study, we present the mold technology and development status for small aircraft firefly.

• Journal of the Korean Magnetics Society
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• v.10 no.2
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• pp.62-66
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• 2000

Annealing cycle number and nonmagnetic layer thickness dependences of interlayer coupling field ( $H_{inf}$ ) and coercivity ( $H_{cf}$ ) of free magnetic layer on NiMn alloy-spin valve films (SVF) were investigated. The SVF is Glass (7059)/N $i_{81}$F $e_{l9}$(70 $\AA$)/Co(10 $\AA$)/Cu(t $\AA$)/Co(15 $\AA$)N $i_{81}$$Fe_{19}$(35 $\AA$)/N $i_{25}$M $n_{75}$(250 $\AA$)Ta(50 $\AA$) films, it were fabricated using the dc sputtering method at different pinning layer thickness and nonmagnetic spacer thickness (Cu thickness; 30 $\AA$, 35 $\AA$, 40 $\AA$) of NiMn alloy with 25 at.%. Ni In case that Cu thickness of SVF is 35 $\AA$ and peak exchange coupling field ( $H_{ex}$) was 620 Oe, while coercivity $H_{c}$ = 280 Oe and MR ratio showed 2.5%. As for $H_{inf}$ and $H_{cf}$ , every SVF increased up to the stabilized values with the increase of annealing cycle number 15, which were $H_{inf}$ of 120 Oe and $H_{cf}$ of 75 Oe. The increase of $H_{cf}$ with the annealing cycle number seems to be caused by the effective reduction of Cu layer thickness due to the increase of interfacial mixing of Cu layer and Co layer. In addition, the $H_{inf}$ and $H_{cf}$ dependences of free NiFe layer by the interfacial mixing effect were appeared the different aspects when Cu layer becomes more thinner and thicker than Cu layer thickness of 35 $\AA$, respectively.ively....

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.3
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• pp.47-57
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• 2020

This study focuses on the proposition that the qualities and environmental conditions required for exploring entrepreneurial opportunities and realizing entrepreneurial opportunities depend on the types of entrepreneurial opportunities. In particular, this study aims to identify the type of entrepreneurial opportunities for laboratory start-ups, which have recently been gaining policy level attention. If the type of entrepreneurial opportunities for laboratory start-ups is identified as discriminative, appropriate start-up support policies and training programs can be established. For this study, eight major papers were identified among the papers of last 30 years related to the types of entrepreneurial opportunities. After, the classification attributes for each opportunity type were derived. Then, the existing theories of recognition, discovery and creative opportunities were organized, critically reviewed and reorganized. In addition, the substance of laboratory start-ups was verified according to the standardized classification attributes of the revised and reorganized opportunity types and newly classified as 'creative opportunity'. This study also presents networking capabilities and market orientation as examples of the capabilities needed for entrepreneurs of creative opportunity type. The implication of this study is that it makes it easy to discriminate ontological typology of entrepreneurial opportunity, derives important classification attributes, and that it organizes them conceptually. In addition, it critically reconstructs the problems of confusion in the existing typology, and based on this, the type of entrepreneurial opportunities for laboratory start-ups is determined as creative opportunity. These achievements can contribute to the improvement of start-up policies and start-up training programs according to the types of entrepreneurial opportunity and laboratory start-ups in the future, resulting in realization of actual results at the start-up sites.

• Journal of the Korean Society of Radiology
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• v.16 no.7
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• pp.835-842
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• 2022

This study is aimed to evaluate the effects of a synthetic MR technique in reducing metal artifacts. In the experiment, the in-plane and through-plane images were acquired by applying a synthetic MR technique and a high-speed spin echo technique to a phantom manufactured with screw for spinal surgery. The area of the metal artifact was compared. The metal artifacts were measured by dividing the signal-loss and the signal pile-up areas, and the area of the final artifact was calculated through the sum of the two. As a result, the metal artifacts were relatively reduced when the synthetic MR techniques were applied to both in-plane and through-plane. Comparing by sequence, the in-plane T1 images decreased by 23.45%, T2 images by 20.85%, PD images by 19.67%, and FLAIR images by 22.12%. Also, in the case of the through-plane, the T1 image decreased by 62.95%, the T2 image decreased by 73.93%, the PD image decreased by 74.68%, and the FLAIR image decreased by 66.43%. The cause of this result is that when the synthetic MR technique is applied, the distortion is due to the signal pile-up and does not occur and the size of the entire metal artifact is reduced. Therefore, synthetic MR technique can very effectively reduce metal artifacts, which can help to increase the diagnostic value of images.

• International Journal of Industrial Entomology and Biomaterials
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• v.5 no.2
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• pp.141-151
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• 2002

The success of sericulture industry in India is mainly attributed to the well-planned annual sericultural activity and the systematic implementation of pest preventive and control measures. The insect spectrum of silkworm and its food plants is complex and plays a major role in limiting the production of silk. Insects cause extensive damage to plant whereas predators and parasites either kill the silkworm larvae or force them to spin flimsy cocoons. Unilateral control measure against this pest is mainly based on the use of synthetic organic insecticides. Though these approaches initially paid rich dividends, the undesirable consequences soon surfaced. Insecticide induced resurgence of gall midges, leafhopper, leaf roller, secondary pest out breaks and development of pest biotypes has led to realization of Integrated Pest Management in sericulture. Various components of IPM, viz. Host plant resistance, cultural practices, biological control, chemical control and integrating them at various technological levels have been studied. Sources of host plant resistance have been identified for some of the major insect pests. High yielding mulberry variety has been propagated and their resistances towards major pests have been recorded. Cultural practices like pruning, pollarding, judicious use of nitrogen, optimum spacing and weed management have preyed to be the powerful tools in containing pests. Natural control over the pest population build- up exerted by the wide range of parasitoids, predators and pathogens has been well documented with identification of natural enemies and studies on their potential. Augmentation, through inoculation or inundative releases of parasitic arthropods, is the most direct way of increasing the numbers of these beneficials in sericulture.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.84.1-84.1
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• 2015

The Baptistina family is one of the typical young asteroid families with an age estimated to be about 140-320 Myrs old (Masiero et al. 2012); considered to have not enough time to experience a significant collisional and dynamical evolution since it was formed. Therefore, it may offer a unique insight into spin rate distribution of relatively fresh fragments and physical mechanism of a family break-up event. Observations of the Baptistina family asteroids were conducted during 111 nights from 2013 Oct. to 2015 Feb., using 0.5 m- to 2 m- class telescopes at 6 observatories in the northern hemisphere. We used CCD cameras on the Sobaeksan Optical Astronomy Observatory (SOAO) 0.6 m telescope on Mt. Sobaek, Korea, the Lemmonsan Optical Astronomy Observatory (LOAO) 1.0 m telescope on Mt. Lemmon, USA, the Tubitak Ulusal Gozlemevi (TUG) 1.0 m telescope in Bakirlitepe, Turkey, the Bohyunsan Optical Astronomy Observatory (BOAO) 1.8 m telescope on Mt. Bohyun, Korea, the McDonald Observatory 2.1 m Otto Struve Telescope on Mt. Locke, USA, and the National Astronomical Research Institute of Thailand (NARIT) Observatory 2.4 m telescope on Mt. Doi Inthanon, Thailand. Here, we will present our preliminary results for lightcurve analyses of Baptistina family members.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1245-1249
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• 2015

This study investigated the reflection spectra of wrinkled metal/polymer multilayers. A wavy surface was self-assembled by annealing an aluminum-coated poly(methyl metacrylate) layer on a silicon substrate. The total and diffuse reflectance characteristics of the sample with additional metal coatings(aluminum or silver) were evaluated in the visible wavelength(400~800 nm) using a spectrophotometer. The results showed that the wrinkled surface enhanced the diffuse reflectance up to 40~50% in the lower-wavelength range, demonstrating its potential for applications to optical thin-film devices.