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1Zircon U-Pb geochronological framework of Qitianling granite batholith, middle part of Nanling Range, South China显示文摘The Qitianling granite batholith (QGB) is located in the southern Hunan Province, middle part of the Nanling Range, South China. Its total exposure area is about 520 km2. Based on our 25 single grain zircon U-Pb age data and 7 published data as well as the geological, petrological, and space distribution characteristics, we conclude that QGB is an Early Yanshanian (Jurassic) multi-staged composite pluton. Its formation process can be subdivided into three major stages. The first stage, emplaced at 163―160 Ma with a peak at about 161 Ma, is mainly composed of hornblende-biotite monzonitic granites and locally biotite granites, and distributed in the eastern, northern, and western peripheral parts of the pluton. The second stage, emplaced at 157―153 Ma with a peak at 157―156 Ma, is mainly composed of biotite granites and locally containing hornblende, and distributed in the middle and southeastern parts of the pluton. The third stage, emplaced at 150―146 Ma with a peak at about 149 Ma, is mainly composed of fine-grained (locally porphyritic) biotite granites, and distributed in the middle-southern part of the pluton. Each stage can be further disintegrated into several granite bodies. The first two intrusive stages comprise the major phase of QGB, and the third intrusive stage comprises the additional phase. Many second stage fine-grained granite bosses and dykes intruded into the first stage host granites with clear chilling margin-baking phenomena at their intrusive contacts. They were emplaced in the open fracture space of the earlier stage consolidated rocks. Their isotopic ages are mostly 2―6 Ma younger than their hosts. Conceivably, the time interval from magma emplacement, through cooling, crystallization, solidification, up to fracturing of the earlier stage granites cannot exceed 2―6 Ma. During the Middle-Late Jurassic in the Qitianling area and neighboring Nanling Range, the coeval granitic and basic-intermediate magmatic activities were widely developed. It indicates that the Early Yanshanian period was the culmination time of magmatic activities in this region. The Nanling Range was under a post-orogenic, intracontinental geotectonic environment with an obvious lithospheric extension and thinning. The crust-mantle interaction played an important role in formation of granitic rocks in this region.ZHU JinChu WANG RuCheng ZHANG PeiHua XIE CaiFu ZHANG WenLan ZHAO KuiDong XIE Lei YANG Ce CHE XuDong YU APeng WANG LuBin 2009Science China Earth Sciences2009,52,9:27
2Outcome of patients with acute, necrotizing pancreatitis requiring drainage-does drainage size matter?显示文摘AIM:To assess the outcome of patients with acute necrotizing pancreatitis treated by percutaneous drainage with special focus on the influence of drainage size and number. METHODS:We performed a retrospective analysis of 80 patients with acute pancreatitis requiring percutaneous drainage therapy for infected necroses. Endpoints were mortality and length of hospital stay. The influence of drainage characteristics such as the median drainage size, the largest drainage size per patient and the total drainage plane per patient on patient outcome was evaluated. RESULTS:Total hospital survival was 66%. Thirty-four patients out of all 80 patients (43%) survived acute necrotizing pancreatitis with percutaneous drainage therapy only. Eighteen patients out of all 80 patients needed additional percutaneous necrosectomy (23%). Ten out of these patients required surgical necrosectomy in addition, 6 patients received open necrosectomy without prior percutaneous necrosectomy. Elective surgery was performed in 3 patients receiving cholecystectomy and one patient receiving resection of the parathyroid gland. The number of drainages ranged from one to fourteen per patient. The drainage diameter ranged from 8 French catheters to 24 French catheters. The median drainage size as well as the largest drainage size used per patient and the total drainage area used per patient did not show statistically significant influence on mortality. CONCLUSION:Percutaneous drainage therapy is an effective tool for treatment of necrotizing pancreatitis.Large bore drainages did not prove to be more effective in controlling the septic focus.T Bruennler J Langgartner S Lang CE Wrede F Klebl S Zierhut S Siebig F Mandraka F Rockmann B Salzberger S Feuerbach J Schoelmerich OW Hamer 2008World Journal of Gastroenterology2008,14,5:23
3Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture显示文摘RemovalofheavymetalsfromsewagesludgebylowcostingchemicalmethodandrecyclinginagricultureWuQitang,NyirandegePascasie,MoCehuiF...Wu Qi tang, Nyirandege Pascasie, Mo Ce hui Faculty of Resources and Environments, South China Agricultural University, Guangzhou 510642, China Lin Yi Datansha Wastewater Treatment Plant, Guangzhou 510160, China 1998Journal of Environmental Sciences1998,10,1:21
4Modified constraint-induced movement therapy alters synaptic plasticity of rat contralateral hippocampus following middle cerebral artery occlusion显示文摘Modified constraint-induced movement therapy is an effective treatment for neurological and motor impairments in patients with stroke by increasing the use of their affected limb and limiting the contralateral limb.However,the molecular mechanism underlying its efficacy remains unclear.In this study,a middle cerebral artery occlusion(MCAO)rat model was produced by the suture method.Rats received modified constraint-induced movement therapy 1 hour a day for 14 consecutive days,starting from the 7^th day after middle cerebral artery occlusion.Day 1 of treatment lasted for 10 minutes at 2r/min,day 2 for 20 minutes at 2 r/min,and from day 3 onward for 20 minutes at 4 r/min.CatWalk gait analysis,adhesive removal test,and Y-maze test were used to investigate motor function,sensory function as well as cognitive function in rodent animals from the 1st day before MCAO to the 21^st day after MCAO.On the 21^st day after MCAO,the neurotransmitter receptor-related genes from both contralateral and ipsilateral hippocampi were tested by micro-array and then verified by western blot assay.The glutamate related receptor was shown by transmission electron microscopy and the glutamate content was determined by high-performance liquid chromatography.The results of behavior tests showed that modified constraint-induced movement therapy promoted motor and sensory functional recovery in the middle cerebral artery-occluded rats,but had no effect on cognitive function.The modified constraint-induced movement therapy upregulated the expression of glutamate ionotropic receptor AMPA type subunit 3(Gria3)in the hippocampus and downregulated the expression of the beta3-adrenergic receptor gene Adrb3 and arginine vasopressin receptor 1 A,Avprla in the middle cerebral artery-occluded rats.In the ipsilateral hippocampus,only Adra2 a was downregulated,and there was no significant change in Gria3.Transmission electron microscopy revealed a denser distribution the more distribution of postsynaptic glutamate receptor 2/3,which is an a-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor,within 240 nm of the postsynaptic density in the contralateral cornu ammonis 3 region.The size and distribution of the synaptic vesicles within 100 nm of the presynaptic active zone were unchanged.Western blot analysis showed that modified constraint-induced movement therapy also increased the expression of glutamate receptor 2/3 and brain-derived neurotrophic factor in the hippocampus of rats with middle cerebral artery occlusion,but had no effect on Synapsin I levels.Besides,we also found modified constraint-induced movement therapy effectively reduced glutamate content in the contralateral hippocampus.This study demonstrated that modified constraint-induced movement therapy is an effective rehabilitation therapy in middle cerebral artery-occluded rats,and suggests that these positive effects occur via the upregulation of the postsynaptic membrane a-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor expression.This study was approved by the Institutional Animal Care and Use Committee of Fudan University,China(approval No.201802173 S)on March 3,2018.Bei-Yao Gao Dong-Sheng Xu Pei-Le Liu Ce Li Liang Du Yan Hua Jian Hu Jia-Yun Hou Yu-Long Bai 2020Neural Regeneration Research2020,15,6:19
5From concept to reality-A review to the primary test stand and its preliminary application in high energy density physics显示文摘Pulsed power technology,whereas the electrical energy stored in a relative long period is released in much shorter timescale,is an efficient method to create high energy density physics(HEDP)conditions in laboratory.Around the beginning of this century,China Academy of Engineering Physics(CAEP)began to build some experimental facilities for HEDP investigations,among which the Primary Test Stand(PTS),a multi-module pulsed power facility with a nominal current of 10 MA and a current rising time~90 ns,is an important achievement on the roadmap of the electro-magnetically driven inertial confinement fusion(ICF)researches.PTS is the first pulsed power facility beyond 10 TW in China.Therefore,all the technologies have to be demonstrated,and all the engineering issues have to be overcome.In this article,the research outline,key technologies and the preliminary HEDP experiments are reviewed.Prospects on HEDP research on PTS and pulsed power development for the next step are also discussed.Jianjun Deng Weiping Xie Shuping Feng Meng Wang Hongtao Li Shengyi Song Minghe Xia Ji Ce An He Qing Tian Yuanchao Gu Yongchao Guan Bin Wei Xianbin Huang Xiaodong Ren Jiakun Dan Jing Li Shaotong Zhou Hongchun Cai Siqun Zhang Kunlun Wang Qiang Xu Yujuan Wang Zhaohui Zhang Guilin Wang Shuai Guo Yi He Yiwei Zhou Zhanji Zhang Libing Yang Wenkang Zou 2016Matter and Radiation at Extremes2016,1,1:19
6Numerical Analysis of Nozzle Clearance's Effect on Turbine Performance显示文摘Variable nozzle turbine (VNT) has become a popular variable geometry turbine (VGT) technology for the diesel engine application. Nozzle clearance, which can't be avoided on the hub and shroud side of the VNT turbine due to the pivoting stators, can lead to turbine performance deterioration. However, its mechanism is still not clear. In this paper, numerical investigation, which is validated by experiment, is carried out to study the mechanism of the nozzle clearance's effect on the turbine performance. Firstly, performance of the mixed flow turbine with fixed nozzle clearances tested on flow bench. Performance of the tested turbine with the same nozzle clearance is numerically simulated. The numerical result agrees well with the test data, which proves correct of the numerical method. Then the turbine performance with different nozzle clearances is numerically analyzed. The research showed that with nozzle clearance, flow loss in the nozzle increases at first and it reaches the maximum value when the clearance ratio is 5%. Flow at the exit of the nozzle becomes less uniform with nozzle clearance. The negative incidence angle of the rotor also increases with nozzle clearance and leads to more incidence angle loss in the rotor. The low energy fluid formed in the nozzle due to the nozzle clearance migrates from hub to shroud side in the rotor, which is another main reason for the rotor's performance degradation. The present research exposed the mechanism of the dramatically decrease of the turbine performance with nozzle clearance: (a) The loss associated with the nozzle leakage increases with the nozzle clearance; (b) The flow loss grows up quickly in the rotor due to the incidence angle loss and migration of the low energy fluid from hub to shroud side.HU Liangjun YANG Ce SUN Harold ZHANG Jizhong LAI Mingchia 2011Chinese Journal of Mechanical Engineering2011,24,4:17
7Three-year results of small incision lenticule extraction and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis for correction of high myopia and myopic astigmatism显示文摘AIM: To compare and calculate the 3-year refractive results, higher-order aberrations(HOAs), contrast sensitivity(CS) and dry eye parameters after small incision lenticule extraction(SMILE) and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK) for correction of high myopia and myopic astigmatism.METHODS: In this prospective, non-randomized comparative study, 78 eyes with spherical equivalent(SE) of-8.11±1.09 diopters(D) received a SMILE surgery, and 65 eyes with SE of-8.05±1.12 D received a wavefront-guided FS-LASIK surgery with the Visu Max femtosecond laser(Carl Zeiss Meditec, Jena, Germany) for flap cutting. Visual acuity, manifest refraction, CS, HOAs, ocular surface disease index(OSDI) and tear break-up time(TBUT) were evaluated during a 3-year follow-up.RESULTS: The difference of uncorrected distance visual acuity(UDVA) postoperatively was achieved at 1 mo and at3 mo, whereas the difference of the mean UDVA between two groups at 3 y were not statistically significant(t=-1.59,P=0.13). The postoperative change of SE was 0.89 D in the FS-LASIK group(t=5.76, P=0.00), and 0.14 D in the SMILE group(t=0.54, P=0.59) from 1 mo to 3 y after surgery.At 3-year postoperatively, both HOAs and spherical aberrations in the SMILE group were obviously less than those in the FS-LASIK group(P=0.00), but the coma root mean square(RMS) was higher in the SMILE group(0.59±0.26) than in the FS-LASIK group(0.29±0.14, P=0.00).The mesopic CS values between two groups were not statistically significant at 3 y postoperatively. Comparedwith the FS-LASIK group, lower OSDI scores and longer TBUT values were found in the SMILE group at 1 mo and 3 mo postoperatively. With regard to safety, no eye lost any line of CDVA in both groups at 3 y after surgery. CONCLUSION: Both SMILE and wavefront-guided FSLASIK procedures provide good visual outcomes. Both procedures are effective and safe, but SMILE surgery achieve more stable long-term refractive outcome and better control of early postoperative dry eye as compared to FS-LASIK.Li-Kun Xia Jing Ma He-Nan Liu Ce Shi Qing Huang 2018International Journal of Ophthalmology(English edition)2018,11,3:16
8Effects of Repetitive Transcranial Magnetic Stimulation Treatment on Event-Related Potentials in Schizophrenia显示文摘Xiao-Dong Lin Xing-Shi Chen Ce Chen Li-Jun Zhang Zuo-Liang Xie Zi-Ye Huang Guang-Dong Chen Wan-Tao Ding Zhi-Guang Lin Ming-Dao Zhang Chong Chen Rong-Qin Wu 2018Chinese Medical Journal2018,,3:16
9High-precision relocation of the aftershock sequence of the January 8,2022,M_(S)6.9 Menyuan earthquake显示文摘The 2022 Menyuan M_(S)6.9 earthquake,which occurred on January 8,is the most destructive earthquake to occur near the Lenglongling(LLL)fault since the 2016 Menyuan M_(S)6.4 earthquake.We relocated the mainshock and aftershocks with phase arrival time observations for three days after the mainshock from the Qinghai Seismic Network using the double-difference method.The total length and width of the aftershock sequence are approximately 32 km and 5 km,respectively,and the aftershocks are mainly concentrated at a depth of 7-12 km.The relocated sequence can be divided into 18 km west and 13 km east segments with a boundary approximately 5 km east of the mainshock,where aftershocks are sparse.The east and west fault structures revealed by aftershock locations differ significantly.The west fault strikes EW and inclines to the south at a 71°-90°angle,whereas the east fault strikes 133°and has a smaller dip angle.Elastic strain accumulates at conjunctions of faults with different slip rates where it is prone to large earthquakes.Based on surface traces of faults,the distribution of relocated earthquake sequence and surface ruptures,the mainshock was determined to have occurred at the conjunction of the Tuolaishan(TLS)fault and LLL fault,and the west and east segments of the aftershock sequence were on the TLS fault and LLL fault,respectively.Aftershocks migrate in the early and late stages of the earthquake sequence.In the first 1.5 h after the mainshock,aftershocks expand westward from the mainshock.In the late stage,seismicity on the northeast side of the east fault is higher than that in other regions.The migration rate of the west segment of the aftershock sequence is approximately 4.5 km/decade and the afterslip may exist in the source region.Liping Fan Boren Li Shirong Liao Ce Jiang Lihua Fang 2022Earthquake Science2022,35,2:14
10盆地演化认识中的几个问题显示文摘本文论述了盆地演化认识中的几个主要问题。一是陆缘裂解过程,华南边缘传统上认为是被动裂谷边缘的一个例子,其东部沉积物记录了压实的历史,它明显不同于被动裂谷作用模式,而是显示早第三纪大规模上隆和侵蚀的特征;而且,该地区覆盖在下地壳楔形体上面,具有比周围地壳明显要高的地震速度和密度,指示岩浆底侵作用。这些证据说明,与被动裂谷作用模式相比,华南边缘与主动裂谷作用模式较为一致,它是由早第三纪华南边缘东部底下地幔柱形成的主动裂谷。另一个问题是关于页岩的浅部破裂作用机理。大多数研究者认为,微裂隙的形成需要高孔隙压力,它限于深埋、低渗透率的岩石。然而,最近从北海观察表明,在第三纪页岩中,整个盆地范围内的破裂型式从未达到大于几百米的埋藏深度。这说明泥质源岩经历了水压破裂和浅部脱水,在破裂前可能达到深埋后生作用所需要的深度,实质上渗透率的改变是由于源岩的浅部破裂作用可能根本上改变了烃类的初次运移时间和效率。Wang Chiyuen(Department of Geology and Geophysics University of California,Berkeley,CA 94720)Yang Jiaming Zhu Weilin(Exploration and Development Research Center,China National Offshore Oil Corporation,Xincheng,074010)Zheng Mingling(Scientific Research Ce 1995地学前缘1995,2,3:14
11Research and Practice of Blending Teaching Based on “MOOC + SPOC + Flipped Classroom” for Software Engineering显示文摘Based on 'MOOC + SPOC + Flipped Classroom', a particular blending teaching pattern adapting to MOOC teaching is proposed to strengthen software engineering students' abilities to study themselves and practice innovatively. Firstly, the process of MOOC development in China is introduced. The distinguishing feature and effect of MOOC teaching are analyzed, followed by the comparison with traditional class. The online Plus offline blending teaching pattern is the combination of online self-study on MOOC before class, seminar study of flipped classroom in class and the summary after class. With the demonstration of a typical case, a progressive strategy is given to implement blending teaching. Finally, the blending teaching pattern is assessed from multiple perspectives, of which both advantages and disadvantages are dissected. Through primary exploration, introducing online study and flipped classroom, blending teaching plays a positive role in software engineering teaching, which means traditional teaching pattern is changed. Meanwhile, students' innovative consciousness and practical ability are inspired. Nevertheless, new problems arise, so that intensive practice and improvement are necessary.Ce Zhang Dianhui Chu Songlin Gu Xiaofei Xu Jianan Jiang Zheng Wang Hua Zhang 2018计算机教育2018,,12:14
12氧化铝/碳化硅纳米复合材料的力学性能和强化机理显示文摘热压合成的氧化铝/碳化硅纳米复合材料的四点弯曲强度随纳米尺寸的碳化硅的含量增加而增大。这一增大被部分地解释为晶粒细化的结果。与具有相同晶粒尺寸的纯氧化铝基体材料相比,复合材料的强度提高约20%。维氏压痕对样品表面应力的探测以及裂纹/粒子互作用的透射电镜观察表明,这一强化应归之于断裂模式的改变,即从氧化铝的沿晶断到复合的穿晶断裂。晶界上的碳化硅粒子在改变断裂模式上可能起着重要作用。焦绥隆 Bors.,CE 1996材料导报1996,,A00:13
13The Change of the Inlet Geometry of a Centrifugal Compressor Stage and its Influence on the Compressor Performance显示文摘The impact on the compressor performance is important for designing the inlet pipe of the centrifugal compressor of a vehicle turbocharger with different inlet pipes. First, an experiment was performed to determine the compressor performance from three cases: a straight inlet pipe, a long bent inlet pipe and a short bent inlet pipe. Next, dynamic sensors were installed in key positions to collect the sign of the unsteady pressure of the centrifugal compressor. Combined with the results of numerical simulations, the total pressure distortion in the pipes, the pressure distributions on the blades and the pressure variability in the diffuser are studied in detail. The results can be summarized as follows: a bent pipe results in an inlet distortion to the compressor, which leads to performance degradation, and the effect is more apparent as the mass flow rate increases. The distortion induced by the bent inlet is not only influenced by the distance between the outlet of the bent section and the leading edge of the impeller but also by the impeller rotation. The flow fields in the centrifugal impeller and the diffuser are influenced by a coupling effect produced by the upstream inlet distortion and the downstream blocking effect from the volute tongue. If the inlet geometry is changed, the distributions and the fluctuation intensities of the static pressure on the main blade surface of the centrifugal impeller and in the diffuser are changed accordingly.WANG Leilei YANG Ce ZHAO Ben LAO Dazhong MA Chaochen LI Du 2013Journal of Thermal Science2013,22,3:13
14Advance in the chemical synthesis and magnetic properties of nanostructured rare-earth-based permanent magnets显示文摘Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rare-earth-based permanent magnets with high energy products are highly required. In this article, we will review the progress in chemical synthetic strategies of nanostructured rare-earth-based permanent magnets.Ce Yang Yang-Long Hou 2013Rare Metals2013,32,2:13
15The MOOC/SPOC Based'1+M+N'Multi-University Collaborative Teaching and Learning Mode:Practice and Experience显示文摘Since 2012, the MOOCs, the massive open online courses, have brought big influences on the higher education in the world. How to use MOOCs to help universities rather than bother them to improve their education level and quality becomes an important issue. In China, many universities have explored the new modes and approaches for MOOC/SPOC-based teaching and learning. Especially, the China MOOC Association on Computing Education(CMOOC association), established in 2014, has done a set of successful practice and achieved fruitful experiences on MOOC courses development and computer education reform. Based on the practical experiences, a MOOC/SPOC based '1+M+N' multi-university collaborative teaching and learning mode is presented, which is adapted to the real situation of Chinese university education. In the paper, the practices and experiences of CMOOC association are introduced, the MOOC/SPOC based '1+M+N' multi-university collaborative teaching and learning mode and its approaches are described. Finally, the suggestions for MOOCs development and applications are also presented.Xiaofei Xu Dechen Zhan Ce Zhang Dianhui Chu Weihua Guo 2018计算机教育2018,,12:11
16Therapeutic effect of neohesperidin on TNF-α-stimulated human rheumatoid arthritis fibroblast-like synoviocytes显示文摘During the pathogensis of rheumatoid arthritis(RA),activated RA fibroblast-like synoviocytes(RA-FLSs)combines similar proliferative features as tumor and inflammatory features as osteoarthritis,which eventually leads to joint erosion.Therefore,it is imperative to research and develop new compounds,which can effectively inhibit abnormal activation of RA-FLSs and retard RA progression.Neohesperidin(Neo)is a major active component of flavonoid compounds with anti-inflammation and anti-oxidant properties.In this study,the anti-inflammation,anti-migration,anti-invasion,anti-oxidant and apoptosis-induced effects of Neo on RAFLSs were explored to investigate the underlying mechanism.The results suggested that Neo decreased the levels of interleukin IL-1β,IL-6,IL-8,TNF-α,MMP-3,MMP-9 and MMP-13 in FLSs.Moreover,Neo blocked the activation of the MAPK signaling pathway.Furthermore,treatment with Neo induced the apoptosis of FLSs,and inhibited the migration of FLSs.It was also found that Neo reduced the accumulation of reactive oxygen species(ROS)induced by TNF-α.Taken together,our results highlighted that Neo may act as a potential and promising therapeutic drug for the management of RA.WANG Xiao-He DAI Ce WANG Jun LIU Rui LI Lei YIN Zong-Sheng 2021Chinese Journal of Natural Medicines2021,19,10:10
17Inlet Recirculation Influence to the Flow Structure of Centrifugal Impeller显示文摘Inlet recirculation is proved as an effective way for centrifugal compressor surge margin extension,and is successively used in some engineering applications.Unfortunately its working mechanism is still not being well understood,which leads to redesigning of inlet recirculation mostly by experience.Also,most study about inlet recirculation is steady to date.It is necessary to study surge margin extension mechanism about inlet recirculation.To expose the mechanism in detail,steady and unsteady numerical simulations were performed on a centrifugal compressor with and without inlet recirculation.The results showed that,with inlet recirculation,the inlet axial velocity is augmented,relative Mach number around blade tip leading edge area is significantly reduced and so is the flow angle.As the flow angle decreased,the incidence angle reduced which greatly improves the flow field inside the impeller.Moreover,inlet recirculation changes the blade loading around blade tip and restrains the flow separation on the blade suction side at the leading edge area.The unsteady results of static pressure around blade surface,entropy at inlet crossflow section and vorticity distributions at near tip span surface indicated that,at near stall condition,strong fluctuation exists in the vicinity of tip area due to the interaction between tip leakage flow and core flow.By inlet recirculation these strong flow fluctuations are eliminated so the flow stability is greatly enhanced.All these improvements mentioned above are the reason for inlet recirculation delays compressor stall.This research reveals the surge margin extension reason of inlet recirculation from an unsteady flow viewpoint and provides important reference for inlet recirculation structure design.YANG Ce CHEN Shan LI Du YANG Changmao WANG Yidi 2010Chinese Journal of Mechanical Engineering2010,23,5:10
18Potential of multi-pass ECAP on improving the mechanical properties of a high-calcium-content Mg-Al-Ca-Mn alloy显示文摘In this study,the multi-pass equal channel angular pressing(ECAP)was employed on a high-calcium-content Mg-Al-Ca-Mn alloy to tailor its microstructure and mechanical properties.The obtained results showed that the network-shaped Mg2Ca and(Mg,Al)2Ca eutectic compounds in as-cast alloy were gradually crushed into ultra-fine particles after ECAP,which exhibited a bimodal particle size distribution and most aggregated at original grain boundaries.Dynamic recrystallization(DRX)of α-Mg occurred during hot deformation via a particle stimulated mechanism,and the almost complete DRX with an average grain size around 1.5μm was obtained after 12p-ECAP.Moreover,abundant nano-sized acicular and spherical precipitates were dynamically precipitated withinα-Mg grains during ECAP.Tensile test results indicated that the maximum strength and ductility were acquired for 12p-ECAP alloy with ultimate tensile strength of 372 MPa and fracture elongation of 8%.The enhanced strength of the alloy could be ascribed to fine DRX grains,ultra-fine Ca-containing particles and dynamically precipitated nano-precipitates,while the improved ductility was mainly due to the refined and homogeneous microstructure,and weak texture with high average Schmid factors.He Huang Huan Liu Ce Wang Jiapeng Sun Jing Bai Feng Xue Jinghua Jiang Aibin Ma 2019Journal of Magnesium and Alloys2019,7,4:10
19Numerical and experimental research on different inlet configurations of high speed centrifugal compressor显示文摘Three different inlet configurations,including a original straight pipe and two bend pipes with different axial length,for a high speed low mass flow centrifugal compressor were modeled with whole blade passages and simulated unsteadily by 3D viscous Navier-Stokes equations.The performance disparities of compressor stage were tested and verified by experiments in which dynamic pressure data acquisition of internal flow field was performed.As the result shows,the choke point decreases to lower mass flow rate due to the distortion caused by bend-pipe inlet and is aggravated as the rotation speed increases.The distortion effect spreads circumferentially in impeller and makes the flow structure varied.The longer axial distance bent inlet leads to larger radial distortion and heavy blockage at mid-span under large mass flow mainly causes compressor choke margin nar-rowed.Bend pipe distortion brings an impact up to diffuser on unsteady pressure pulsation caused by blades sweep and the impact appears more powerful when it is closer to volute tongue.LI Du YANG Ce ZHOU Mi ZHU ZhiFu WANG Hang 2012Science China(Technological Sciences)2012,55,1:9
20Landuse/landcover changes in Zhangye oasis of Hexi Corridor显示文摘Taking two f alse color composite Landsat 5 TM (Thematic Mapper) images of band 4,3,2 taken in 1995 and 2000 as data resources, this paper carried out study on LUCC of Zhan gye oasis in recent five years by interpretation according to land reso urces classification system of 1:100,000 Resources and Environmental Data base of the Chinese Academy of Sciences. The results show that great changes have taken place in landuse/landcover in Zhangye oasis since 1 995: (1) Changes of landuse structure show that cropland and land for urban c onstruction and built-up area increased, on the contrary, water area an d grassland decreased. These changes reflect the deterioration of eco-e nvironment and the acceleration of urbanization, and also indicate the problems existing in the arrangement of water and land resources betw een the upper and lower reaches of the Heihe River. (2) Regional diff erences of landuse/landcover are evident, characterized by following asp ects: in Sunan County located in Qilian Mountain area, unused land an d grassland decreased, but cropland and land for urban construction an d built-up area increased. In Minle and Shandan counties located in f oothills, unused land, water area and cropland decreased, but grassland and land for urban construction and built-up area increased. In Zhan gye City, Linze County and Gaotai County located in plain area of th e middle reaches of the Heihe River, unused land, water area and gra ssland decreased, while woodland, cropland and land for urban construction and built-up area increased.MENG Jijun,WU Xiuqin,LI Zhengguo(Department of Urban and Environmental Scien ce, Peking University, Laboratory of Analysis and Simulation of Earth Surface P rocesses, the Ministry of Education, Beijing 100871, China) 2003Journal of Geographical Sciences2003,13,1:9
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