• 보존과학연구
• /
• s.28
• /
• pp.59-73
• /
• 2007

Wooden artifacts are biologically damaged by animals, insects, and micro-organisms. We focused on the evaluation of the antifungal and insecticidal activities of tree extracts to control deterioration of wooden cultural properties. 12 kinds of methanol extracts from 9 species of tree were investigated for their biocidal activities against two micro-organisms and two spices of insect. Most tree extracts showed fungicidal activities to Tyromyces palustris and Trametes versicolor. Among 12 different tree extracts, the strongest antifungal activity against T.palustris and T.versicolor was observed from the extracts of Pinus densiflora stem-bark extract and Pinus koraiensis leaf extracts. However, in the insecticidal activity test, Pinus densiflora stem-bark extracts against termite was relatively effective. Chemical compositions of methanol extracts were analyzed by gas chromatography/mass spectrometry. As a result, it was confirmed that development of biocide based on the natural extracts can be expected to conservate of wooden cultural properties.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.163.1-163.1
• /
• 2014

Electron-electron interactions bear important information on fundamental electronic properties such as electron effective mass, conductivity, and charge mobility. By using angle-resolved photoemission spectroscopy, here we address unusual electron self-energy in graphene induced by the electron-electron interactions, which are distinguished from those of an ordinary Fermi liquid. Our findings provide a new route for two-dimensional electron systems toward device applications.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2002.12a
• /
• pp.150-151
• /
• 2002

In recent years, semi-metallic Bismuth (Bi) has attracted significant attention due to very large magnetoresistance (MR) at room temperature originating from long carrier mean free path l and small effective carrier mass m＊[1, 2]. In particular, the MR behavior and long carrier mean free path l in Bi thin films can be exploited for spintronic devices, e.g. magnetic field sensors and spin-valve transistors. In present work, we present the magnetotransport properties of the electroplated and sputtered Bi thin films in the temperature range 4-300 K. (omitted)

• Smart Structures and Systems
• /
• v.13 no.2
• /
• pp.257-280
• /
• 2014

In this paper, a novel PARAllel FACtor (PARAFAC) decomposition based Blind Source Separation (BSS) algorithm is proposed for modal identification of structures equipped with tuned mass dampers. Tuned mass dampers (TMDs) are extremely effective vibration absorbers in tall flexible structures, but prone to get de-tuned due to accidental changes in structural properties, alteration in operating conditions, and incorrect design forecasts. Presence of closely spaced modes in structures coupled with TMDs renders output-only modal identification difficult. Over the last decade, second-order BSS algorithms have shown significant promise in the area of ambient modal identification. These methods employ joint diagonalization of covariance matrices of measurements to estimate the mixing matrix (mode shape coefficients) and sources (modal responses). Recently, PARAFAC BSS model has evolved as a powerful multi-linear algebra tool for decomposing an $n^{th}$ order tensor into a number of rank-1 tensors. This method is utilized in the context of modal identification in the present study. Covariance matrices of measurements at several lags are used to form a $3^{rd}$ order tensor and then PARAFAC decomposition is employed to obtain the desired number of components, comprising of modal responses and the mixing matrix. The strong uniqueness properties of PARAFAC models enable direct source separation with fine spectral resolution even in cases where the number of sensor observations is less compared to the number of target modes, i.e., the underdetermined case. This capability is exploited to separate closely spaced modes of the TMDs using partial measurements, and subsequently to estimate modal parameters. The proposed method is validated using extensive numerical studies comprising of multi-degree-of-freedom simulation models equipped with TMDs, as well as with an experimental set-up.

• Nuclear Engineering and Technology
• /
• v.54 no.6
• /
• pp.2253-2261
• /
• 2022

In this study, nano-scaled shielding materials were assembled and fabricated by doping different weight percentages of Nano-mercuric oxide (N-HgO) into Nano-Bentonite (N-Bent) based on using (100-x% N-Bent + x% N-HgO, x = 10, 20, 30, and 40 wt %). The fabricated N-HgO/N-Bent nanocomposites were characterized by FT-IR, XRD, and SEM and evaluated to evaluate their shielding properties toward gamma radiation by using four different γ-ray energies form three point sources; 356 keV from ¹³³Ba, 662 keV from ¹³⁷Cs as well as 1173, and 1332 keV from ⁶⁰Co. The γ-rays mass attenuation coefficients were plotted as a function of the doped N-HgO concentrations into N-HgO/N-Bent nanocomposites. The computed values of mass attenuation coefficients (µ_m), effective atomic number (Z_eff) and electron density (N_el) by the as-prepared samples were found to increase, while the half value layer (HVL) and mean free path (MFP) were identified to decrease upon increasing the N-HgO contents. It was concluded also that the increase in N-HgO concentration led to a direct increase in the mass attenuation coefficient from 0.10 to 0.17 cm²/g at 356 keV and from 0.08 to 0.09 cm²/g at 662 keV. However, a slight increase was observed in the identified mass attenuation coefficients at (1172 and 1332 keV).

• The Journal of Engineering Geology
• /
• v.12 no.3
• /
• pp.319-332
• /
• 2002

This study is focused on the characterization of an effective hydraulic conductivity in each hydrogeologic unit assumed as an equivalent continuum medium in the granitic area. Four boreholes of 3" diameter were installed and a Multi-packer system was facilitated in the selected borehole. Various in-situ tests including the fracture logging, constant injection and fall-off tests, slug and pulse tests were carried out. A hydrogeologic unit was defined into the upper and lower zones based on the variation of fracture properties and hydraulic conductivities. The difference of the result obtained by the various hydraulic tests and the effective characterization techniques on rock mass permeability are also discussed. The effective hydraulic conductivity of the upper unit was measured by two times(5.27E-10 m/s~7.57E-10 m/s) that of the lower unit(2.45E-10 m/s~6.81E-10 m/s)through the constant injection and fall-off tests.

• Nuclear Engineering and Technology
• /
• v.53 no.6
• /
• pp.2025-2037
• /
• 2021

The influence of lead cations on natural quartz (QZ) from Egypt as a glass shielding material for the composition with nominal formula (10Na₂O - (90 - x) QZ - xPbO (where x = 30, 35, 40, 45 and 50 mol %)) was examined. The studied samples are synthesized via the melt quenching method at 1050 ℃. The X-ray diffraction XRD patterns were confirmed the glass nature for studied samples. Moreover, the optical properties, and the transparency for all compositions were examined by UV-Vis spectroscopy. Also, the major elemental composition of the natural quartz were estimated via the X-ray fluorescence (XRF) technique. Further, the density and molar volume were determined. Furthermore, the nuclear shielding parameters such as, mass attenuation coefficient, effective atomic number, electronic density, the total atomic, and electronic cross sections as well as the mean free path, and the half value layer with different gamma ray energies (81 keV-1407 keV) were calculated. Besides, the results showed that the shielding behavior towards the gamma ray radiation for all glass samples was increased as the increment in PbO concentration in the glass system.

• Journal of the Korean Magnetic Resonance Society
• /
• v.6 no.1
• /
• pp.69-77
• /
• 2002

During the screening of material which has the antimicrobial activity against aminoglycoside-resistant bacteria, A new material $\varepsilon$-(L-$\beta$-Iysine) polypeptide from a culture medium of Streptomyces sp.(DWGS2) was isolated, and the structure and the physicochemical properties of the new material were elucidated. The new material was separated by column chromatography of the culture medium using Dowex1$\times$2, Silica gel, and Sephadex LH20 etc. The chemical structure and molecular weight were determined with the data of various NMR experiments, MALDI mass, and ESI mass experiments. The antimicrobial activity of $\varepsilon$-(L-$\beta$-Iysine) polypeptide is not only better than equal to the activity of known aminoglycoside type of antibiotics(MIC=3.125 - 6.25ug/mL) but also effective against aminoglycoside-resistant bacteria and fungi. If the mechanism of antimicrobial activity against aminoglycoside- resistant bacteria is figured out, the $\varepsilon$-(L-$\beta$-Iysine) polypeptide can be utilized for the treatment of diseases caused by aminoglycoside-resistant bacteria.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.38.3-38.3
• /
• 2019

We investigate the stellar population properties of nine passive spiral galaxies in the CALIFA survey. They have NUV-r > 5 and no/weak nebular emission lines in their spectra. They lie in the redshift range of 0.001 < z < 0.021 and have stellar mass range of 10.2 < ${\log}(M{\star}/M{\odot})$ < 10.8. We analyze the stellar populations out to two effective radius, using the best-fitting model to the measured absorption line-strength indices in the Lick/IDS system. We compare the passive spirals with S0s selected in the same mass range. S0s cover a wide range in age, metallicity, and [${\alpha}/Fe$], and stellar populations of the passive spirals are encompassed in the spread of the S0 properties. However, the distribution of passive spirals are skewed toward higher values of metallicity, lower [${\alpha}/Fe$], and younger ages at all radii. These results show that passive spirals are possibly related to S0s in their stellar populations. We infer that the diversity in the stellar populations of S0s may result from different evolutionary pathways of S0 formation, and passive spirals may be one of the possible channels.

• Proceedings of the Korean Fiber Society Conference
• /
• 2002.04a
• /
• pp.309-312
• /
• 2002

The polymer nanocomposites are attracting considerable attention on account of the characteristic properties of nanoparticles have extremely large surface area per a unit mass. Recentry, mica-type silicates like montmorillonite have received a good deal of attention as effective nano-reinforcemen(1), but actually some critical problems such as the difficulties of exfoliation and surface modification, the weak heat-resistance of modifier, and inferior processability due to the increase in melt viscosity have restricted the mass production and various applications of the nanocoposite. (omitted)