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Jun Wen,Liusen Hu,Min Yin,Shangda Xia 한국물리학회 2012 Current Applied Physics Vol.12 No.3
The 4f energy levels and crystal-field parameters for several clusters representing the local coordination surroundings of Eu3þ in the bulk and nanocrystalline cubic Y2O3: Eu3+ crystals are obtained by using a method based on the combination of the DV-Xa calculation and the effective Hamiltonian method initialized by M.F. Reid et al. (J. Phys.: Condens. Matter, 2011, 23: 045501). The results are in reasonable agreement with the measured energy levels and the crystal-field parameters obtained from the leastsquare fitting. The charge transfer energies are also obtained for all the clusters from the DV-Xa calculation. The results indicate that, compared with the bulk Y2O3: Eu3+ crystal, the charge transfer band in the excitation spectra is red-shifted in the nanocrystal. The 4f energy levels and crystal-field parameters for several clusters representing the local coordination surroundings of Eu3þ in the bulk and nanocrystalline cubic Y2O3: Eu3+ crystals are obtained by using a method based on the combination of the DV-Xa calculation and the effective Hamiltonian method initialized by M.F. Reid et al. (J. Phys.: Condens. Matter, 2011, 23: 045501). The results are in reasonable agreement with the measured energy levels and the crystal-field parameters obtained from the leastsquare fitting. The charge transfer energies are also obtained for all the clusters from the DV-Xa calculation. The results indicate that, compared with the bulk Y2O3: Eu3+ crystal, the charge transfer band in the excitation spectra is red-shifted in the nanocrystal.
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High-temperature-mixing hydrothermal synthesis of ZnO nanocrystals with wide growth window
Jun Wen,Yonghong Hu,Kongjun Zhu,Yufang Li,Jizhong Song 한국물리학회 2014 Current Applied Physics Vol.14 No.3
High-quality and controllable growth of nanocrystals (NCs) have been attracting great attention. Here, a high-temperature-mixing hydrothermal (HTMH) method was designed to synthesize ZnO NCs with high crystallinity and narrow size distribution in a wide growth window. Compared with conventional hydrothermal (CH) growth, zinc source and alkali precursors were intentionally separated in temperaturerising stage and permitted to mix at the starting of heat preservation stage of HTMH growth. Highly crystalline ZnO NCs with uniform spherical morphology can be formed at alkali concentration and temperature windows as wide as 0.1e0.5 M and 160e200 C, respectively. However, the products via CH method have much larger changes in not only morphology but also size. These results demonstrated that the high-temperature-mixing reaction greatly facilitates nucleation but depresses grain growth. Considering the simplicity and reproducibility, such HTMH method could have wide potentials for the fabrication of various functional nanocrystals.
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Shaking table test of liquid storage tank with finite element analysis considering uplift effect
Junwen Zhou,Ming Zhao 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.3
The seismic responses of elevated tanks considering liquid-structure interaction are presented under horizontal earthquake. The scaled model tank is fabricated to study the dynamic responses of anchored tank and newly designed uplift tank with replaced dampers. The natural frequencies for structural mode are obtained by modal analysis. The dynamic responses of tanks are completed by finite element method, which are compared with the results from experiment. The displacement parallel and perpendicular to the excitation direction are both gained as well as structural acceleration. The strain of tank walls and the axial strain of columns are also obtained afterwards. The seismic responses of liquid storage tank can be calculated by the finite element model effectively and the results match well with the one measured by experiment. The aim is to provide a new type of tank system with vertical constraint relaxed which leads to lower stress level. With the liquid volume increasing, the structural fundamental frequency has a great reduction and the one of uplift tank are even smaller. Compared with anchored tank, the displacement of uplift tank is magnified, the strain for tank walls and columns parallel to excitation direction reduces obviously, while the one perpendicular to earthquake direction increases a lot, but the values are still small. The stress level of new tank seems to be more even due to uplift effect. The new type of tank can realize recoverable function by replacing dampers after earthquake.
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Review of seismic studies of liquid storage tanks
Ming Zhao,Junwen Zhou 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.5
The academic research works about liquid storage tanks are reviewed for the purpose of providing valuable reference to the engineering practice on their aseismic design. A summary of the performance of tanks during past earthquakes is described in this paper. Next, the seismic response of tanks under unidirectional earthquake is reported, supplemented with the dynamic response under multidirectional motions. Then, researches on the influence of soil-structure interaction are brought out to help modify the seismic design approach of tanks in different areas with variable properties of soils. Afterwards, base isolation systems are reported to demonstrate their effectiveness for the earthquake-resistant design of liquid storage tanks. Further, researches about the liquid-structure interaction are reviewed with description of simplified models and numerical analytical methods, some of which consider the elastic effect of tank walls. Moreover, the liquid sloshing phenomenon on the hydrodynamic behaviors of tanks is presented by various algorithms including grid-based and meshfree method. And then the impact of baffles in changing the dynamic characteristics of the liquid-structure system is raised, which shows the energy dissipation by the vortex motion of liquid. In addition, uplifting effect is given to enhance the understanding on the capacity of unanchored tanks and some assessment of their development. At last, the concluding remarks and the aspects of extended research in the field of liquid storage tanks under seismic loads are provided, emphasizing the thermal stress analysis, the replaceable system for base isolation, the liquid-solid interaction and dynamic responses with stochastic excitations.
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Acteoside reduces testosterone by inhibiting cAMP, p450scc, and StAR in rat Leydig cells
Shuqiang Liu,Junwen Zhang,Weixuan Li,Tianxiang Zhang,Defu Hu 대한독성 유전단백체 학회 2015 Molecular & cellular toxicology Vol.11 No.1
The present study investigated the in vivo and in vitro effects of acteoside on testosterone production in Sprague-Dawley (SD) rats. The in vivo experiment revealed that acteoside reduced the testosterone level in serum significantly (P⁄0.05). The in vitro experiment also illustrated that acteoside significantly reduced testosterone production in SD rat Leydig cells in primary culture (P⁄0.05). Enzyme-linked immunosorbent assay results demonstrated that acteoside significantly reduced the cyclic adenosine 3′, 5′-monophosphate (cAMP) level (P⁄0.05), and Western blot analysis showed that acteoside significantly reduced cholesterol side-chain cleavage enzyme (p450scc) and steroidogenic acute regulatory (StAR) expression (P⁄ 0.05). Hoechst 33342 staining and Western blotting showed that acteoside did not induce apoptosis in Leydig cells. Together, these results suggest that the acteoside-induced reduction in testosterone production in rat may be at least partially due to down-regulation of cAMP, p450scc, and StAR, but not apoptosis.
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Frederick Sarpong,Cunshan Zhou,Junwen Bai,Leticia Peace Amenorfe,Moses Kwaku Golly,Haile Ma 한국식품과학회 2019 Food Science and Biotechnology Vol.28 No.1
Drying and b-carotenes retention kinetics werepredicted using models in relative humidity (RH) dryingcondition. This was achieved by drying carrot slices usingRH-convective hot-air dryer at 60, 70 and 80 C under RH(10% 20% and 30%) conditions at 2.0 m/s air velocity. Three mathematical models describing thin layer werecompared to their goodness of fit in terms of coefficient ofcorrelation (R2), root mean square error (RMSE) andreduced Chi square (v2). The Wang and Singh model couldsatisfactorily describe RH-convective drying of carrot sliceswith R2, RMSE and v2 in the ranges of 0.996–0.999,5.4 9 10-4–9.4 9 10-4 and 0.0150–0.03353 respectively. The results reveal that a range of 3.61–8.2% retention of bcarotenewas observed for every 10% increase in RH invarious drying air temperature. In summary, higher temperatureswere mainly responsible for b-carotenes degradationhowever this can be mitigated when drying isconducted under higher RH.
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