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Xuhui Zhang,Yi-Min Xia,Qing Tan,Dun Wu**** 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.10
To improve the excavation efficiency of Tunnel Boring Machines (TBMs), the free-face-assisted rock cutting method induced by TBM disc cutter (FM) was explored and the differences between the FM and the conventional Cutting Method (CM) were also compared based on a series of rock cutting tests. The results show that when the free face distance is less than a critical value, the FM can promote the tensile failure of the rock and the formation of big rock debris effectively. Moreover, the cutting efficiency and the cutting forces including normal force, rolling force and side force of the disc cutter under the FM are also significantly reduced and improved, respectively, compared to that under the CM. The FM can be applied in multi-stage cutterhead TBMs to improve the cutting efficiency and reduce the failure of the disc cutter, the research results indicate that the free face distance should be controlled within 80 mm to use the free face effectively.
Expression, Purification and Properties of Shikimate Dehydrogenase from Mycobacterium Tuberculosis
Zhang, Xuelian,Zhang, Shunbao,Hao, Fang,Lai, Xuhui,Yu, Haidong,Huang, Yishu,Wang, Honghai Korean Society for Biochemistry and Molecular Biol 2005 Journal of biochemistry and molecular biology Vol.38 No.5
Tuberculosis, caused by Mycobacterium tuberculosis, continues to be one of the main diseases to mankind. It is urgent to discover novel drug targets for appropriate antimicrobial agents against this human pathogen. The shikimate pathway is onsidered as an attractive target for the discovery of novel antibiotics for its essentiality in bacteria and absence in mammalian cells. The Mycobacterium tuberculosis aroE-encoded shikimate dehydrogenase was cloned, expressed and purified. Sequence alignment analysis shows that shikimate dehydrogenase of Mycobacterium tuberculosis exhibit the pattern of G-X-(N/S)-V-(T/S)-X-PX-K, which is highly conserved within the shikimate dehydrogenase family. The recombinant shikimate dehydrogenase spectrum determined by CD spectroscopy showed that the percentages for $\alpha$-helix, $\beta$-sheet, $\beta$-turn, and random coil were 29.2%, 9.3%, 32.7%, and 28.8%, respectively. The enzymatic characterization demonstrates that it appears to be fully active at pH from 9.0 to 12, and temperature $63^{\circ}C$. The apparent Michaelis constant for shikimic acid and $NADP^+$ were calculated to be about $29.5\;{\mu}M$ and $63\;{\mu}M$. The recombinant shikimate dehydrogenase catalyzes the substrate in the presence of $NADP^+$ with an enzyme turnover number of $399\;s^{-1}$. Zymological studies suggest that the cloned shikimate dehydrogenase from M. tuberculosis has a pretty activity, and the work should help in the discovery of enzyme inhibitors and further of possible antimicrobial agents against Mycobacterium tuberculosis.
Zhang, Xiao-Dong,Jing, Yaqi,Song, Shasha,Yang, Jiang,Wang, Jun-Ying,Xue, Xuhui,Min, Yuho,Park, Gyeongbae,Shen, Xiu,Sun, Yuan-Ming,Jeong, Unyong Elsevier 2017 Nanomedicine Vol.13 No.5
<P><B>Abstract</B></P> <P>Bi<SUB>2</SUB>Se<SUB>3</SUB> nanoparticles (NPs) have attracted wide interests in biological and medical applications. Layer-like Bi<SUB>2</SUB>Se<SUB>3</SUB> with high active surface area is promising for free radical scavenging. Here, we extended the medical applications of Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs further to <I>in vivo</I> protection against ionizing radiation based on their superior antioxidant activities and electrocatalytic properties. It was found that Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs can significantly increase the surviving fraction of mice after exposure of high-energy radiation of gamma ray. Additionally, the Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs can help to recover radiation-lowered red blood cell counts, white blood cell counts and platelet levels. Further investigations revealed that Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs behaved as functional free radical scavengers and significantly decreased the level of methylenedioxyamphetamine. <I>In vivo</I> toxicity studies showed that Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs did not cause significant side effects in panels of blood chemistry, clinical biochemistry and pathology.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs can significantly increase the surviving fraction of mice up to 70% after Gamma radiation. </LI> <LI> Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs can help to recover radiation-lowered red blood cell counts, white blood cell counts and platelet levels. </LI> <LI> Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs behaved as functional free radical scavengers and significantly decreased the level of methylenedioxyamphetamine. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>Layer-like Bi<SUB>2</SUB>Se<SUB>3</SUB> with high active surface area can protect mice against ionizing radiation based on their superior antioxidant activities and electrocatalytic properties. Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs can significantly increase the surviving fraction of mice up to 70% after exposure of high-energy radiation of gamma ray. Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs behaved as functional free radical scavengers and significantly decreased the level of methylenedioxyamphetamine. <I>In vivo</I> toxicity studies showed that Bi<SUB>2</SUB>Se<SUB>3</SUB> NPs did not cause significant side effects in panels of blood chemistry, clinical biochemistry and pathology.</P> <P>[DISPLAY OMISSION]</P>
Hong Zhang,Lei Shi,Xuhui Liu,Xianshu Leng,Ding Feng,Paul Tu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.12
Wellbore trajectory control tool is a sort of point-the-bit drilling tool to achieve the steering function while drilling. In complex conditions, the spindle bears the acting force of the bit pressure, the torque, the force of biasing mechanism and so on. So the force is very complex. Basing on the early research of our group, the further research of spindle deflecting reliability of prototype has been carried out. Based on the contact analysis between the tool spindle and the inner eccentric ring, the variation law of contact stress between the inner ring of the eccentric mechanism and the spindle is studied. Based on Palmgren-Miner and the fatigue life experiment of the spindle material, the cumulative damage calculation model of the spindle is established, and the fatigue life of spindle is solved. The result shows that the deflecting reliability of the spindle can be guaranteed.
Wenshan Li,Xuhui Wen,Jian Zhang,Youlong Wang 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.6
This paper describes a narrow pulse suppression method that is called hybrid modulation strategy for T-type neutral point clamped (TNPC) three-level converters. Conventional VSVPWM does not function well in high-frequency TNPC converters due to the problem of narrow pulses during the permanent magnet synchronous motor (PMSM) starting process. The narrow pulse phenomenon occurs when the ON/OFF state time of the driving pulse is less than the minimum time required by the power devices. The narrow pulse threatens the safe operation of power devices and results in a high surge voltage and electromagnetic interference. In addition, neutral point voltage unbalance is caused by the narrow pulse in motor starting process. The eff ects of the narrow pulse on the surge voltage and the neutral point voltage are both discussed in this paper. The minimum pulse width function is designed to defi ne the relationship between the gate drive signal and the modulation strategy. The switch pattern limited region of the virtual space vector modulation strategy is analyzed by the minimum pulse width function under both low and high modulation indexes. A resistance inductance load and a PMSM drive system test setup based on a TNPC three-level converter are both established to verify the analysis and eff ectiveness of the proposed method.
DPOAE Biological Feature Modeling and Identity Authentication
Haijun Lin,Bin Zhang,Xuhui Zhang,Binqiu Duan 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.10
In this article, a multi-tone signal generated by micro-speaker is adopted as the acoustic stimulation, and two microphones are used to collect the DPOAE data from human ear and background noise respectively. Otoacoustic emission is modeled based on Volterra kernel. The feature of human ear’s DPOAE feature model is extracted intelligently by improved stimulation annealing genetic mixed algorithm. In order to apply this model feature to identification, its feasibility is verified by BP neural network. This provides a new biometric method for identity authentication.
Wear Characteristics of TBM Disc Cutter Ring Sliding against Different Types of Rock
Laikuang Lin,Yimin Xia,Xuhui Zhang 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.10
To investigate wear characteristics of tunnel boring machine (TBM) disc cutter rings interacting with types of rock, a range of wear tests were performed on a TBM cutter test rig, and laboratory-scale disc cutters were used in the experiments. The mass loss, vertical load, temperature field, wear mechanism and change rule of cutter tip for the disc cutter rings were obtained during the tests. The results indicate that the rock types and properties of rock exhibit great influences on the cutter wear. The variation of the weight loss testing with different types of rock is partially explained by the discrepancies of vertical load, cutting temperature, and the transition of wear mechanisms. In addition, the test results show that the wear characteristics of cutter rings are mainly affected by uniaxial compressive strength (UCS) rather than equivalent quartz content (EQC) for types of rock. This study will benefit the design of cutter rings with enhanced wear resistance.