| 11. |
- Liu, Tang hong, et al.
(författare)
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Field test measurement of the dynamic tightness performance of high-speed trains and study on its influencing factors
- 2019
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Ingår i: Measurement: Journal of the International Measurement Confederation. - : Elsevier BV. - 0263-2241. ; 138, s. 602-613
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Tidskriftsartikel (refereegranskat)abstract
- During the actual operation of a high-speed train, the airtight performance of the carriages will change significantly. Based on a series of field tests, the external and interior pressure variations of train carriages are measured and then the dynamic pressure tightness coefficient are analysed quantitatively for investigating the airtight performance of a train passing at various speeds through tunnels of different lengths. It is found that the amplitude of the external pressure variations is proportional to the square of the train speed, while the amplitude inside the vehicle is approximately proportional to the speed to the 0.7th power due to the airtight effect. The dynamic pressure tightness coefficient increases with increasing tunnel length and decreases with increasing train speed. Regarding the effect of the carriage location, the coefficient shows an overall increasing trend from the train head to tail.
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| 12. |
- Liu, Tao, et al.
(författare)
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Prediction model for austenite grains growth during reheating process in Ti micro-alloyed cast steel by coupling precipitates dissolution and coarsening behavior
- 2019
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Ingår i: Journal of Iron and Steel Research International. - : SPRINGER. - 1006-706X .- 2210-3988. ; 26:2, s. 162-172
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Tidskriftsartikel (refereegranskat)abstract
- A combined model to predict austenite grains growth of titanium micro-alloyed as-cast steel during reheating process was established. The model involves the behaviors of austenite grains growth in continuous heating process and isothermal soaking process, and the variation of boundary pinning efficiency caused by the dissolution and coarsening kinetics of second-phase particles was also considered into the model. Furthermore, the experimental verifications were performed to examine the prediction power of the model. The results revealed that the mean austenite grains size increased with the increase in reheating temperature and soaking time, and the coarsening temperature of austenite grains growth was 1423K under the current titanium content. In addition, the reliability of the predicted results in continuous heating process was validated by continuous heating experiments. Moreover, an optimal regression expression of austenite grains growth in isothermal soaking process was obtained based on the experimental results. The compared results indicated that the combined model in conjunction with precipitates dissolution and coarsening kinetics had good reliability and accuracy to predict the austenite grains growth of titanium micro-alloyed casting steel during reheating process.
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| 13. |
- Liu, Tanghong, 1976, et al.
(författare)
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Wave effects in a realistic tunnel induced by the passage of high-speed trains
- 2019
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798. ; 86, s. 224-235
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Tidskriftsartikel (refereegranskat)abstract
- As a high-speed train passes through a tunnel, aerodynamic pressure waves propagate backwards and forward in the tunnel, and they persist for a long time after the train is gone. Understanding the aerodynamic characteristics influenced by various factors on a tunnel is essential for ensuring the safety of tunnel structures. Field measurements were conducted in a 2812 m-long tunnel to systematically investigate the pressure characteristics during the passage of CRH2-150C and CRH380AL high-speed trains through the tunnel, both in single-train and intersecting cases. The results reveal that as the train speed increases, the location of the maximum peak-to-peak pressure variation shifts toward the tunnel entrance, mainly driven by the change in the negative pressure peak. The train length induces significant differences in peak pressures on the tunnel wall in the middle of the tunnel, and a long train brings more massive subsequent pressure waves than a short train in the post-train stage, but they decay faster. The intersection of two trains in the tunnel not only causes a significant change in the peak pressure and its location, but also has a significant effect on damage factor (the damage level on a structure subjected to a specific load) after train leaving the tunnel, with a 65.3% of this factor during trains operating in the tunnel.
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| 14. |
- Wang, Min, et al.
(författare)
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Apolipoprotein M induces inhibition of inflammatory responses via the S1PR1 and DHCR24 pathways
- 2019
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Ingår i: Molecular Medicine Reports. - 1791-2997. ; 19:2, s. 1272-1283
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Spandidos Publications. All rights reserved. Apolipoprotein M (ApoM) is a type of apolipoprotein. It is well known that high-density lipoprotein (HDL) decreases inflammatory responses via the apoM-sphingosine-1-phosphate (S1P) pathway. The present study further investigated the importance of ApoM in the inhibitory effects of HDL on inflammation. Mice with an apoM gene deficiency (apoM-/-) were employed to investigate the effects of ApoM on the expression of interleukin-1β (IL-1β), monocyte chemotactic protein-1 (MCP-1), S1P receptor-1 (S1PR1) and 3β-hydroxysterol Δ-24-reductase (DHCR24), as compared with in wild-type mice (apoM+/+). Furthermore, cell culture experiments were performed using a permanent human hybrid endothelial cell line (EA.hy926). Cells were cultured in the presence of recombinant human apoM (rec-apoM) or were induced to overexpress apoM (apoMTg); subsequently, cells were treated with tumor necrosis factor-α (TNF-α), in order to investigate the effects of ApoM on IL-1β and MCP-1. The results demonstrated that the mRNA expression levels of IL-1β and MCP-1 were significantly higher in the liver following administration of lipopolysaccharide in apoM-/- mice compared with in apoM+/+ mice. In cell culture experiments, when cells were pre-cultured with rec-apoM or were engineered to overexpress apoM (apoMTg), they exhibited decreased expression levels of IL-1β and MCP-1 following TNF-α treatment compared with in normal apoM-expressing cells (apoMTgN). Furthermore, the mRNA expression levels of IL-1β and MCP-1 were significantly elevated following addition of the S1PR1 inhibitor W146, but not by the scavenger receptor class B type I inhibitor, block lipid transport-1 (BLT-1), in apoMTg cells prior to TNF-α treatment. Conversely, there were no differences in these inflammatory biomarkers under the same conditions in apoMTgN cells. The mRNA expression levels of DHCR24 were significantly reduced by the addition of BLT-1 prior to TNF-α treatment in apoMTg cells; however, there was no difference in the expression of this inflammatory biomarker in apoMTgN cells. In conclusion, ApoM displayed inhibitory effects against the inflammatory response in vivo and in vitro; these effects may be induced via the S1PR1 and DHCR24 pathways.
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| 15. |
- Wang, Renjun, et al.
(författare)
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Sympathoexcitation in Rats With Chronic Heart Failure Depends on Homeobox D10 and MicroRNA-7b Inhibiting GABBR1 Translation in Paraventricular Nucleus
- 2016
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Ingår i: Circulation Heart Failure. - 1941-3289 .- 1941-3297. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Chronic heart failure (CHF) increases sympathoexcitation through angiotensin II (ANG II) receptors (AT1R) in the paraventricular nucleus (PVN). Recent publications indicate both γ-aminobutyric acid B-type receptor 1 (GABBR1) and microRNA-7b (miR-7b) are expressed in the PVN. We hypothesized that ANG II regulates sympathoexcitation through homeobox D10 (HoxD10), which regulates miR-7b in other tissues.METHODS AND RESULTS: Ligation of the left anterior descendent coronary artery in rats caused CHF and sympathoexcitation. PVN expression of AT1R, HoxD10, and miR-7b was increased, whereas GABBR1 was lower in CHF. Infusion of miR-7b in the PVN caused sympathoexcitation in control animals and enhanced the changes in CHF. Antisense miR-7b infused in PVN normalized GABBR1 expression while attenuating CHF symptoms, including sympathoexcitation. A luciferase reporter assay detected miR-7b binding to the 3' untranslated region of GABBR1 that was absent after targeted mutagenesis. ANG II induced HoxD10 and miR-7b in NG108 cells, effects blocked by AT1R blocker losartan and by HoxD10 silencing. miR-7b transfection into NG108 cells decreased GABBR1 expression, which was inhibited by miR-7b antisense. In vivo PVN knockdown of AT1R attenuated the symptoms of CHF, whereas HoxD10 overexpression exaggerated them. Finally, in vivo PVN ANG II infusion caused dose-dependent sympathoexcitation that was abrogated by miR-7b antisense and exaggerated by GABBR1 silencing.CONCLUSIONS: There is an ANG II/AT1R/HoxD10/miR-7b/GABBR1 pathway in the PVN that contributes to sympathoexcitation and deterioration of cardiac function in CHF.
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| 16. |
- Xin, Yan-Bo, et al.
(författare)
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Research progress of hydrogen tunneling in two-dimensional materials
- 2017
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Ingår i: Wuli xuebao. - : CHINESE PHYSICAL SOC. - 1000-3290. ; 66:5
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Forskningsöversikt (refereegranskat)abstract
- One-atom-thick material such as graphene, graphene derivatives and graphene-like materials, usually has a dense network lattice structure and therefore dense distribution of electronic clouds in the atomic plane. This unique structure makes it have great significance in both basic research and practical applications. Studies have shown that molecules, atoms and ions are very difficult to permeate through these above-mentioned two-dimensional materials. Theoretical investigations demonstrate that even hydrogen, the smallest in atoms, is expected to take billions of years to penetrate through the dense electronic cloud of graphene. Therefore, it is generally considered that one-atom-thin materialis impermeable for hydrogen. However, recent experimental results have shown that the hydrogen atoms can tunnel through graphene and monolayer hexagonal boron nitride at room temperature. The existence of defects in one-atomthin material can also effectively reduce the barrier height of the hydrogen tunneling through graphene. Controversy exists about whether hydrogen particles such as atoms, ions or hydrogen molecules can tunnel through two-dimensional materials, and it has been one of the popular topics in the fields of two-dimensional materials. In this paper, the recent research progressof hydrogen tunneling through two-dimensional materials is reviewed. The characteristics of hydrogen isotopes tunneling through different two-dimensional materials are introduced. Barrier heights of hydrogen tunneling through different graphene and graphene-like materials are discussed and the difficulties in its transition are compared. Hydrogen cannot tunnel through the monolayer molybdenum disulfide, only a little small number of hydrogen atoms can tunnel hrough graphene and hexagonal boron nitride, while hydrogen is relatively easy to tunnel through silicene and phosphorene. The introduction of atomic defects or some oxygen-containing functional groups into the two-dimensional material is discussed, which can effectively reduce the barrier height of the hydrogen tunneling barrier. By adding the catalyst and adjusting the temperature and humidity of the tunneling environment, the hydrogen tunneling ability can be enhanced and the hydrogen particles tunneling through the two-dimensional material can be realized. Finally, the applications of hydrogen tunneling through two-dimensional materials in ion-separation membranes, fuel cells and hydrogen storage materials are summarized. The potential applications of hydrogen permeable functional thin film materials, lithium ion battery electrode materials and nano-channel ions in low energy transmission are prospected. The exact mechanism of hydrogen tunneling through two-dimensional material is yet to be unravelled. In order to promote these applications and to realize large-scale production and precision machining of these two-dimensional materials, an in-depth understanding of the fundamental questions of the hydrogen tunneling mechanism is needed. Further studies are needed to predict the tunneling process quantitatively and to understand the effects of catalyst and the influences of chemical environments.
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| 17. |
- Xu, Chao-Qun, et al.
(författare)
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Genome sequence of Malania oleifera, a tree with great value for nervonic acid production
- 2019
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Ingår i: GigaScience. - : Oxford University Press. - 2047-217X. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- Background Malania oleifera, a member of the Olacaceae family, is an IUCN red listed tree, endemic and restricted to the Karst region of southwest China. This tree's seed is valued for its high content of precious fatty acids (especially nervonic acid). However, studies on its genetic makeup and fatty acid biogenesis are severely hampered by a lack of molecular and genetic tools. Findings We generated 51 Gb and 135Gb of raw DNA sequences, using Pacific Biosciences (PacBio) single-molecule real-time and 10x Genomics sequencing, respectively. A final genome assembly, with a scaffold N50 size of 4.65 Mb and a total length of 1.51Gb, was obtained by primary assembly based on PacBio long reads plus scaffolding with 10x Genomics reads. Identified repeats constituted approximate to 82% of the genome, and 24,064 protein-coding genes were predicted with high support. The genome has low heterozygosity and shows no evidence for recent whole genome duplication. Metabolic pathway genes relating to the accumulation of long-chain fatty acid were identified and studied in detail. Conclusions Here, we provide the first genome assembly and gene annotation for M. oleifera. The availability of these resources will be of great importance for conservation biology and for the functional genomics of nervonic acid biosynthesis.
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| 18. |
- Yang, Zhenxing, et al.
(författare)
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Tuning the band gap and the nitrogen content in carbon nitride materials by high temperature treatment at high pressure
- 2018
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Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 130, s. 170-177
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nitride (C-N) materials have been attracting great interest because of their extraordinary performance in photocatalysis and energy conversion. However, developing an effective strategy for achieving band-gap engineering of C-N materials to satisfy practical applications remains highly desired. Here we report an efficient way to tune the band gap and control the nitrogen stoichiometry in carbon nitride compounds by using high pressure and high temperature (HPHT) treatment. It is found that treating a g-C3N4 precursor at relatively low temperature (630oC and below) under pressure can efficiently narrow the band gap even down to the red light region (~600 nm), increase the crystallinity, and significantly improve the charge carrier separation efficiency (by two orders of magnitude), almost without changing their stoichiometry. When increasing the treatment temperature under pressure, nitrogen-doped graphene/graphite materials with weak ferromagnetism were obtained. We thus obtained C-N materials with tunable band gaps, ranging from semiconducting to metallic states. XPS measurements show that pyridinic nitrogen is preferentially eliminated under such HPHT conditions while graphitic nitrogen is preserved in the C-N network. Our results thus provide an efficient strategy for tuning the structure and physical properties of C-N materials for applications.
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| 19. |
- Yu, Jiangfei, et al.
(författare)
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Numerical investigation in chaos characteristics of macro-mixing efficiency of two-dimensional supersonic mixing layer
- 2015
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Ingår i: Proceedings of the Institution of Mechanical Engineers. Part G: Journal of Aerospace Engineering. - : SAGE Publications. - 0954-4100 .- 2041-3025. ; 229:7, s. 1226-1235
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Tidskriftsartikel (refereegranskat)abstract
- Coherent structures of two-dimensional supersonic turbulent mixing layers with the engineering background have been investigated numerically with large eddy simulation method. The chaos characteristics of transverse sections of mixing layer flowfield have been obtained through the analyses of two chaos characteristic parameters, Lyapunov exponent and correlation dimension. The results show that under the conditions of the present numerical simulations and physical models, the distribution of correlation dimension is roughly consistent with that of streamwise turbulent intensity at transverse sections of mixing layers through analysis of nonlinear time series, as may be used to measure the macro-mixing efficiency of mixing layers quantitatively. The distribution of maximal Lyapunov exponent could be used to validate the quantitative results. Therefore, a potential experimental method measuring the thickness of mixing layers with low costs on the basis of chaos characteristic parameters has been proposed firstly.
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