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        검색결과 70

        1.
        2023.10 구독 인증기관·개인회원 무료
        Honey bees are crucial pollinators for agricultural and natural ecosystems, but are experiencing heavy mortality in Korea due to a complex suite of factors. Extreme winter losses of honey bee colonies are a major threat to beekeeping but the combinations of factors underlying colony loss remain debatable. Finding solutions involves knowing the factors associated with high loss rates. To investigate whether loss rates are related to Varroa control and climate condition, we surveyed beekeepers in korea after wintering (2021–2022 to 2022–2023). The results show an average colony loss rate of 46%(2022) and 17%(2023), but over 40% colony loss before wintering at 2022. Beekeepers attempt to manage their honey bee colonies in ways that optimize colony health. Disentangling the impact of management from other variables affecting colony health is complicated by the diversity of practices used and difficulties handling typically complex and incomplete observational datasets. We propose a method to 1) Varroa mite population Control by several methods , and 2) Many nursing bee put in hive before wintering.
        2.
        2021.01 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Dynamic behavior of piezoelectric ZnO nanowires is investigated using finite element analyses (FEA) on FE models constructed based on previous experimental observations in which nanowires having aspect ratios of 1:2. 1:31, and 1:57 are obtained during a hydrothermal process. Modal analyses predict that nanowires will vibrate in lateral bending, uniaxial elongation/contraction, and twisting (torsion), respectively, for the three ratios. The natural frequency for each vibration mode varies depending on the aspect ratio, while the frequencies are in a range of 7.233 MHz to 3.393 GHz. Subsequent transient response analysis predicts that the nanowires will behave quasi-statically within the load frequency range below 10 MHz, implying that the ZnO nanowires have application potentials as structural members of electromechanical systems including nano piezoelectric generators and piezoelectric dynamic strain sensors. When an electric pulse signal is simulated, it is predicted that the nanowires will deform in accordance with the electric signal. Once the electric signal is removed, the nanowires exhibit a specific resonance-like vibration, with the frequency synchronized to the signal frequency. These predictions indicate that the nanowires have additional application potential as piezoelectric actuators and resonators.
        4,200원
        5.
        2018.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The purpose of this study was to evaluate the effect of joint mobilization and manual stretching exercises in patients with hallux valgus. Twenty-three participants were divided into two groups; joint mobilization (n=11) and manual stretching exercises (n=12). The subjects participated in the experiment for 15minutes, three times a week, four weeks. The joint mobilization (Grade III, Maitland) was performed to experimental group for a minute and then rested for 10 seconds for each set. The manual stretching was performed to control group with three exercise session (preparatory and finishing exercises, agonist contraction exercises, agonist contraction and hold-relax exercises). In the results of the study, intragroup comparison of the deformity angles (DA) was shown to decrease from 15.18° to 13.09° in the joint mobilization group (p<.05) and from 19.00° to 16.83° in the stretching exercises group (p<.05). However, left static foot pressure (LSFP), right static foot pressure (RSFP), left dynamic foot pressure (LDFP) and right dynamic foot pressure (RDFP) did not significantly increase or decrease after the experiment. Intergroup differences also were not statistically significant in all variables (p>.05). The current study suggests that JM and MSE are effective in decreasing the DA in patients with hallux valgus.
        4,000원
        6.
        2018.11 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Finite element analyses are carried out to understand the piezoelectric behaviors of ZnO nanowires. Three different types of ZnO nanowires, with aspect ratios of 1:2. 1:31, and 1:57, are analyzed for uniaxial compression, pure bending, and buckling. Under the uniaxial compression with a strain of 1.0 × 10−4 as the reference state, it is predicted that all three types of nanowires develop the same magnitude of the piezoelectric fields, which suggests that longer nanowires exhibit higher piezoelectric potential. However, this prediction is not in agreement with the experimental results previously reported in the literature. Such discrepancy is understood when the piezoelectric behaviors under bending and buckling are considered. When only the strain field due to bending is present in bending or buckling, the antisymmetric nature of the through-thickness stain distribution indicates that two piezoelectric fields, the same in magnitude and opposite in sign, develop along the thickness direction, which cancels each other out, resulting in a zero net piezoelectric field. Once additional strain contribution due to axial deformation is superposed on the bending, such field cancelling is compensated for due to the axial component of the piezoelectric field. Such numerical predictions seem to explain the reported experimental results while providing a guideline for the design of nanowire-based piezoelectric devices.
        4,000원
        10.
        2017.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        To establish low-temperature process conditions, process-property correlation has been investigated for Ga-doped ZnO (GZO) thin films deposited by pulsed DC magnetron sputtering. Thickness of GZO films and deposition temperature were varied from 50 to 500 nm and from room temperature to 250 oC, respectively. Electrical properties of the GZO films initially improved with increase of temperature to 150 oC, but deteriorated subsequently with further increase of the temperature. At lower temperatures, the electrical properties improved with increasing thickness; however, at higher temperatures, increasing thickness resulted in deteriorated electrical properties. Such changes in electrical properties were correlated to the microstructural evolution, which is dependent on the deposition temperature and the film thickness. While the GZO films had c-axis preferred orientation due to preferred nucleation, structural disordering with increasing deposition temperature and film thickness promoted grain growth with a-axis orientation. Consequently, it was possible to obtain a good electrical property at relatively low deposition temperature with small thickness.
        4,000원
        18.
        2015.07 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The feasibility of obtaining graphitic carbon films on targeted substrates without a catalyst and transfer step was explored through the pyrolysis of the botanical derivative camphor. In a horizontal quartz tube, camphor was subjected to a sequential process of evaporation and thermal decomposition; then, the decomposed product was deposited on a glass substrate. Analysis of the Raman spectra suggest that the deposited film is related to unintentionally doped graphitic carbon containing some sp-sp 2 linear carbon chains. The films were transparent in the visible range and electrically conductive, with a sheet resistance comparable to that of graphene. It was also demonstrated that graphitic films with similar properties can be reproduciblyobtained, while property control was readily achieved by varying the process temperature.
        4,000원
        19.
        2014.11 구독 인증기관·개인회원 무료
        Dictyophora indusiata (Vent.) Desv., “Queen of the mushroom”, is a mushroom in family Phallaceae of Basidiomycota, which is commonly used as edible and medicinal mushroom in China and Korea. This study initiated to evaluate the anti-cholinesterase, skin anti-wrinkle and melanogenesis inhibitory of 80% methanol extract from fruiting body of D.indusiata. In the anti-cholinesterase experiment, acetyl-cholinesterase and butyryl-cholinesterase inhibitory activities were performed. The extract were inhibited acetyl-cholinesterase and butyryl-cholinesterase 44.09% and 49.14% at the concentration 1 mg/mL, respectively. The skin anti-wrinkle effect of the extract were determined by measuring anti-collagenase and anti-elastase activities. While melanogenesis inhibitory activities were performed by tyrosinase, DOPA inhibitory and melanin synthesis inhibitory activities. The tyrosinase inhibitory activity of the extract were from 37.60~68.96%, while DOPA inhibitory activity were from 15.43 ~ 29.58% at the concentration ranged from 0.125~2.0 mg/mL. In addition, cellular tyrosinase activity was tested with result of the enzyme activity reduced from 99.09% to 72.91% against 25~500 μg/mL of the extract. The methanol extract of D.indusiata was inhibited melanin synthesis activity 41.86% at the concentration 500 μg/mL. The collagenase inhibitory activity of the extract from D.indusiata were 34.87%, which was comparable with the positive control, EGCG ( 45.31%). While the extract showed good inhibition of elastase enzyme (46.64%). The experiment results suggested that fruiting body of Dictyophora indusiata could be used as natural anti-cholinesterase and skin care agents.
        20.
        2014.11 구독 인증기관·개인회원 무료
        Calocybe indica (Purkayastha, 1974), Milky mushroom, is a relatively new to the world of mushroom industry, which is belong to Lyophyllaceae of Basidiomycota, and commonly used as edible mushroom in India and Southern Asia country. This study was conducted to investigate the free radical scavenging, skin whitening and anti-collagenase activities of methanol extract from fruiting body of C.indica cultivated in Bangladesh. In addition, the polyphenol compounds of the extract were analyzed by HPLC. The mushroom extract showed good activity in lipid peroxidation which ranged from 29.35% to 55.39% at the concentration 0.125~2.0 mg/mL. The scavenging activity of the extract on 1,1-diphenyl-2-picrylhydrazy radicals were from 20.22~83.93% at the same tested concentration, which were comparable with the positive control BHT. The hydroxyl radical scavenging activity of the extract was 76.24~93.92%. The skin whitening effect of the mushroom extract was performed with UV light protecting, tyrosinase and DOPA inhibitory activities. The methanol extract absorbed UV-B wavelength with maximum level of 0.356 at 280 nm. The tyrosinase and DOPA inhibitory activities of the extract were ranged from 30.36 ~ 66.25% and 7.13 ~ 30.25% at the concentration 0.125~2.0 mg/mL, respectively. Furthermore, anti-collagenase activity were determined by measuring collagenase and elastase inhibitory activity. The collagenase and elastase inhibitory activity of the extract were 42.77% and 51.08% at the concentration 1.0 mg/mL, respectively. The experiment results suggested that fruiting body of Calocybe indica could be used as natural skin care and antioxidant agents.
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