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      • The Impacts and Countermeasures of Japan's Proposal to Release Nuclear-Contaminated Water into the Sea on Neighboring Countries

        Xuexi Zhang(Xuexi Zhang),Xi Chen(Xi Chen) 아시아사회과학학회 2023 Jornal of Asia Social Science Vol.10 No.1

        Since 2020, the Japanese government has made great efforts to promote the discharge of nuclear-polluted water from the Fukushima nuclear power plant. Although it is strongly opposed by the Japanese and neighboring countries, the Japanese government still puts economic benefits first and does not fully consider the biological and chemical hazards that may be caused by the discharge of nuclear-polluted water into the sea, the impact on people's health, or whether it will pose a threat to Japan's offshore and neighboring countries' marine safety and food safety. As always, it is an obvious violation of the United Nations Convention on the Law of the Sea to choose the simplest, lowest-cost, and most irresponsible way to discharge nuclear-polluted water into the sea, which needs to be highly valued by neighboring countries and even all countries around the Pacific Ocean, and actively take measures to avoid the harm caused by Japan's nuclear-polluted water discharged into the sea to neighboring countries. To solve the current problems, it is necessary for the United Nations to actively play the role of central mediator and for neighboring countries to jointly create international public opinion on the harm caused by the discharge of nuclear-polluted water into the sea. At the same time, it is also necessary to call on non-governmental environmental protection organizations to protest and continuously increase internal pressure in Japan. In addition, the active resistance to importation of the fish resources from Japan and the reduction in the number of tourists to Japan are also important measures to prevent the Japanese government from dumping nuclear-polluted water. Therefore, actively calling on the Japanese government to cancel or terminate the dumping of nuclear-polluted water into the sea is not only the greatest protection of the lives and property of people in Japan and neighboring countries, but a responsible expression of ensuring that the world's maritime security is not threatened.

      • KCI등재

        Magnesium isoglycyrrhizinate inhibits L-type Ca2+ channels, Ca2+ transients, and contractility but not hERG K+ channels

        Yue Lin,Yuanyuan Zhang,Qiongtao Song,Tao Song,Xue Han,Ying Zhang,Xuan Zhang,Xi Chu,Fenghua Zhang,Li Chu,Jianping Zhang 대한약학회 2017 Archives of Pharmacal Research Vol.40 No.10

        To explore the cardiovascular protective effectsof Magnesium isoglycyrrhizinate (MI), especially theunderlying cellular mechanisms related to L-type calciumchannels and myocardial contractility, and to examine theeffects of MI on hERG K? current expressed in HEK293cells. We used the whole-cell patch clamp technique,video-based edge detection and dual excitation fluorescencephotomultiplier systems to explore the effect of MIon L-type Ca2? currents (ICa-L) and cell contraction in ratcardiomyocytes. We also examined the rapidly activatingdelayed rectifier potassium current (IKr) expressed inHEK293 cells using a perforated patch clamp. MI inhibitedICa-L in a dose-dependent manner, with a half-maximalinhibitory concentration (IC50) of 0.22 mg/ml, and themaximal inhibitory effect was 61.10 ± 0.59%. MI at aconcentration of 0.3 mg/ml reduced cell shortening by24.12 ± 3.97% and the peak value of the Ca2? transient by36.54 ± 4.96%. MI had no significant influence on hERGK? channels expressed in HEK293 cells at all testpotentials. MI exerts protective effects on the heart via theinhibition of ICa-L and cell shortening in rat cardiomyocytes. However, MI had no significant influence on IKr;thus, MI may exert cardioprotective effects without causingdrug-induced long QT syndrome.

      • KCI등재

        Reduced-order Mapping and Design-oriented Instability for Constant On-time Current-mode Controlled Buck Converters with a PI Compensator

        Xi Zhang,Jianping Xu,Jiahui Wu,Bocheng Bao,Guohua Zhou,Kaitun Zhang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

        The constant on-time current-mode controlled (COT-CMC) switching dc-dc converter is stable, with no subharmonic oscillation in its current loop when a voltage ripple in its outer voltage loop is ignored. However, when its output capacitance is small or its feedback gain is high, subharmonic oscillation may occur in a COT-CMC buck converter with a proportional-integral (PI) compensator. To investigate the subharmonic instability of COT-CMC buck converters with a PI compensator, an accurate reduced-order asynchronous-switching map model of a COT-CMC buck converter with a PI compensator is established. Based on this, the instability behaviors caused by output capacitance and feedback gain are investigated. Furthermore, an approximate instability condition is obtained and design-oriented stability boundaries in different circuit parameter spaces are yielded. The analysis results show that the instability of COT-CMC buck converters with a PI compensator is mainly affected by the output capacitance, output capacitor equivalent series resistance (ESR), feedback gain, current-sensing gain and constant on-time. The study results of this paper are helpful for the circuit parameter design of COT-CMC switching dc-dc converters. Experimental results are provided to verify the analysis results.

      • KCI등재

        Design-Oriented Stability of Outer Voltage Loop in Capacitor Current Controlled Buck Converters

        Xi Zhang,Zhongwei Zhang,Bocheng Bao,Han Bao,Zhimin Wu,Kaiwen Yao,Jing Wu 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

        Due to the inherent feedforward of load current, capacitor current (CC) control shows a fast transient response that makes itsuitable for the power supplies used in various portable electronic devices. However, considering the effect of the outer voltageloop, the stable range of the duty-cycle is significantly diminished in CC controlled buck converters. To investigate the stabilityeffect of the outer voltage loop on buck converters, a CC controlled buck converter with a proportion-integral (PI) compensatoris taken as an example, and its second-order discrete-time model is established. Based on this model, the instability caused by theduty-cycle is discussed with consideration of the outer voltage loop. Then the dynamical effects of the feedback gain of the PIcompensator and the equivalent series resistance (ESR) of the output capacitor on the CC controlled buck converter with a PIcompensator are studied. Furthermore, the design-oriented closed-loop stability criterion is derived. Finally, PSIM simulationsand experimental results are supplied to verify the theoretical analyses.

      • Effects of silver nanoparticles on neonatal testis development in mice

        Zhang, Xi-Feng,Gurunathan, Sangiliyandi,Kim, Jin-Hoi Dove Medical Press 2015 International journal of nanomedicine Vol.10 No.-

        <P><B>Background</B></P><P>Metal nanoparticles (MNPs) play an important role in consumer products. An increasing use of MNPs has raised concerns about potential risks for human health. Therefore, in vivo tests of MNPs are urgently required. Using mice as a model animal, the aim of the present study was designed to investigate the effect of biologically synthesized silver nanoparticles (AgNPs) on spermatogenesis in neonatal mice.</P><P><B>Methods</B></P><P>AgNPs were synthesized using <I>Bacillus funiculus</I>. The prepared nanoparticles were characterized using various analytical techniques such as UV–visible spectroscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, and transmission electron microscopy. The prepared AgNPs were used to investigate testis development in neonatal mice. Institute of Cancer Research neonatal male mice were used in all experiments and were treated with different doses (0, 1, and 5 mg/kg) of AgNPs five times (interval of 3 days from postnatal day [PND] 8–21) by abdominal subcutaneous injection.</P><P><B>Results</B></P><P>The results showed that the sperm abnormalities such as quality and quantity were significantly increased by the synthesized AgNPs. The diameter of the convoluted tubules shrank significantly in mice treated with AgNPs on PND28 and PND42. The results of reverse transcription-quantitative polymerase chain reaction indicated that the <I>E1f1ay</I>, <I>Gsta4</I>, and <I>Fdx1</I> genes were up-regulated, and the <I>Amh</I>, <I>Cx43</I>, and <I>Claudin-11</I> genes were down-regulated in response to AgNPs exposure on PND28; however, these genes recovered at PND60. AgNPs had no effect on the recombination levels of chromosomes in germ cells.</P><P><B>Conclusion</B></P><P>These results demonstrated the adverse effects of AgNPs on the male reproductive tract, particularly spermatogenesis and the quality of sperm. This study suggests that the development of nanomaterials should be safer and non-toxic to the living organisms and the potential reprotoxicity of AgNPs should be investigated more carefully.</P>

      • SCIESCOPUSKCI등재

        Design-Oriented Stability of Outer Voltage Loop in Capacitor Current Controlled Buck Converters

        Zhang, Xi,Zhang, Zhongwei,Bao, Bocheng,Bao, Han,Wu, Zhimin,Yao, Kaiwen,Wu, Jing The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

        Due to the inherent feedforward of load current, capacitor current (CC) control shows a fast transient response that makes it suitable for the power supplies used in various portable electronic devices. However, considering the effect of the outer voltage loop, the stable range of the duty-cycle is significantly diminished in CC controlled buck converters. To investigate the stability effect of the outer voltage loop on buck converters, a CC controlled buck converter with a proportion-integral (PI) compensator is taken as an example, and its second-order discrete-time model is established. Based on this model, the instability caused by the duty-cycle is discussed with consideration of the outer voltage loop. Then the dynamical effects of the feedback gain of the PI compensator and the equivalent series resistance (ESR) of the output capacitor on the CC controlled buck converter with a PI compensator are studied. Furthermore, the design-oriented closed-loop stability criterion is derived. Finally, PSIM simulations and experimental results are supplied to verify the theoretical analyses.

      • SCIESCOPUS

        Effect of joint gap on bead formation in laser butt welding of stainless steel

        Zhang, Yan-Xi,Han, Sang-Woo,Cheon, Jason,Na, Suck-Joo,Gao, Xiang-Dong Elsevier 2017 Journal of materials processing technology Vol.249 No.-

        <P>Simulations and experiments of laser butt welding are presented in the paper with the laser beam traveling along an inclined line across the gap. Full penetration was observed when the laser beam focused on the gap, while partial penetration was achieved when the laser beam deviated from the gap. A three-dimensional numerical model coupled with a ray tracing algorithm was established to investigate and compare the transient dynamics of the keyhole, molten pool and laser induced plume. The shape of the simulation cross-sections of the welds show good agreement with the experimental results. The gap contributed to transmission of laser beam energy deep into the inner part of the workpiece. The absorbed energy by the workpiece decreased when the laser beam was focused on the gap as some rays escaped through the opening gap. The decrease in absorbed energy resulted in a lower velocity of the molten pool and lower average pressure on the free surface. The velocity and volume of the plume on the top side of the workpiece also decreased. Flow patterns in the molten pool were also identified and discussed.</P>

      • KCI등재

        Biosynthesis of adipic acid in metabolically engineered Saccharomyces cerevisiae

        Zhang Xi,Liu Yingli,Wang Jing,Zhao Yunying,Deng Yu 한국미생물학회 2020 The journal of microbiology Vol.58 No.12

        Adipic Acid (AA) is a valued platform chemical compound, which can be used as a precursor of nylon-6,6. Due to the generation of an enormous amount of nitric oxide metabolites and the growing depletion of oil resources as a result of AA production from a mixture of cyclohexanol and cyclohexanone, the microbial methods for synthesizing AA have attracted significant attention. Of the several AA-producing pathways, the reverse adipate degradation pathway in Thermobifida fusca (Tfu RADP) is reported to be the most efficient, which has been confirmed in Escherichia coli. In this study, the heterologous Tfu RADP was constructed for producing AA in S. cerevisiae by co-expressing genes of Tfu_ 0875, Tfu_2399, Tfu_0067, Tfu_1647, Tfu_2576, and Tfu_ 2576. The AA titer combined with biomass, cofactors and other by-products was all determined after fermentation. During batch fermentation in a shake flask, the maximum AA titer was 3.83 mg/L, while the titer increased to 10.09 mg/L during fed-batch fermentation in a 5-L bioreactor after fermentation modification.

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