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1Towards 6G wireless communication networks:vision,enabling technologies,and new paradigm shifts显示文摘The fifth generation(5G)wireless communication networks are being deployed worldwide from 2020 and more capabilities are in the process of being standardized,such as mass connectivity,ultra-reliability,and guaranteed low latency.However,5G will not meet all requirements of the future in 2030 and beyond,and sixth generation(6G)wireless communication networks are expected to provide global coverage,enhanced spectral/energy/cost efficiency,better intelligence level and security,etc.To meet these requirements,6G networks will rely on new enabling technologies,i.e.,air interface and transmission technologies and novel network architecture,such as waveform design,multiple access,channel coding schemes,multi-antenna technologies,network slicing,cell-free architecture,and cloud/fog/edge computing.Our vision on 6G is that it will have four new paradigm shifts.First,to satisfy the requirement of global coverage,6G will not be limited to terrestrial communication networks,which will need to be complemented with non-terrestrial networks such as satellite and unmanned aerial vehicle(UAV)communication networks,thus achieving a space-airground-sea integrated communication network.Second,all spectra will be fully explored to further increase data rates and connection density,including the sub-6GHz,millimeter wave(mmWave),terahertz(THz),and optical frequency bands.Third,facing the big datasets generated by the use of extremely heterogeneous networks,diverse communication scenarios,large numbers of antennas,wide bandwidths,and new service requirements,6G networks will enable a new range of smart applications with the aid of artificial intelligence(AI)and big data technologies.Fourth,network security will have to be strengthened when developing 6G networks.This article provides a comprehensive survey of recent advances and future trends in these four aspects.Clearly,6G with additional technical requirements beyond those of 5G will enable faster and further communications to the extent that the boundary between physical and cyber worlds disappears.Xiaohu YOU Cheng-Xiang WANG Jie HUANG Xiqi GAO Zaichen ZHANG Mao WANG Yongming HUANG Chuan ZHANG Yanxiang JIANG Jiaheng WANG Min ZHU Bin SHENG Dongming WANG Zhiwen PAN Pengcheng ZHU Yang YANG Zening LIU Ping ZHANG Xiaofeng TAO Shaoqian LI Zhi CHEN Xinying MA Chih-Lin I Shuangfeng HAN Ke LI Chengkang PAN Zhimin ZHENG Lajos HANZO Xuemin(Sherman)SHEN Yingjie Jay GUO Zhiguo DING Harald HAAS Wen TONG Peiying ZHU Ganghua YANG Jun WANG Erik GLARSSON Hien Quoc NGO Wei HONG Haiming WANG Debin HOU Jixin CHEN Zhe CHEN Zhangcheng HAO Geoffrey Ye LI Rahim TAFAZOLLI Yue GAO HVincent POOR Gerhard P.FETTWEIS Ying-Chang LIANG 2021Science China(Information Sciences)2021,64,1:122
2Effects of water management on arsenic and cadmium speciation and accumulation in an upland rice cultivar显示文摘Pot and field experiments were conducted to investigate the effects of water regimes on the speciation and accumulation of arsenic(As) and cadmium(Cd) in Brazilian upland rice growing in soils polluted with both As and Cd. In the pot experiment constant and intermittent flooding treatments gave 3–16 times higher As concentrations in soil solution than did aerobic conditions but Cd showed the opposite trend. Compared to arsenate, there were more marked changes in the arsenite concentrations in the soil solution as water management shifted, and therefore arsenite concentrations dominated the As speciation and bioavailability in the soil. In the field experiment As concentrations in the rice grains increased from 0.14 to 0.21 mg/kg while Cd concentrations decreased from 0.21 to 0.02 mg/kg with increasing irrigation ranging from aerobic to constantly flooding conditions. Among the various water regimes the conventional irrigation treatment produced the highest rice grain yield of 6.29 tons/ha. The As speciation analysis reveals that the accumulation of dimethylarsinic acid(from 11.3% to 61.7%) made a greater contribution to the increase in total As in brown rice in the intermittent and constant flooding treatments compared to the intermittent-aerobic treatment. Thus, water management exerted opposite effects on Cd and As speciation and bioavailability in the soil and consequently on their accumulation in the upland rice. Special care is required when irrigation regime methods are employed to mitigate the accumulation of metal(loid)s in the grain of rice grown in soils polluted with both As and Cd.Pengjie Hu Younan Ouyang Longhua Wu Libo Shen Yongming Luo Peter Christie 2015Journal of Environmental Sciences2015,27,1:43
3Energy analysis for damage and catastrophic failure of rocks显示文摘The development history and current state of studies on the characteristics and mechanisms of deformation and failure of rock materials were briefly reviewed from the viewpoint of energy.The main scope and the achievable objectives of the energy-based research system were expatiated.It was validated by experiments that the damage process of rocks can be well described by the rock damage evolution equation established based on energy dissipation.It was found from the uniaxial compression and biaxial compression tests that only a small proportion of the total input energy in hard rocks is dissipated before peak load and a large proportion in soft rocks is dissipated before peak load.For both hard and soft rocks,the energy dissipated after peak load accounts for a greater proportion.More energy would be required for rock failure under equal biaxial compression than under unequal biaxial compression.The total absorbed energy is different for rock failure under high-rate loading and low-rate loading.More fragmented failure pattern usually corresponds to higher energy absorption.The mesoscopic analysis on the damage and failure of bedded salt rocks showed that the energy dissipation is prominent and the total absorbed energy for rock failure is low when cracks propagate in the weak mud interlayer while it is contrary when cracks propagate in the salt rock.The energy accumulation,transfer,dissipation and release during the failure process of tunnel with impending failure under disturbance were analyzed theoretically based on the elastoplastic mechanics theory.Furthermore,the spatial distribution of energy dissipation and energy release of fractured rocks under unloading was simulated numerically.It was demonstrated that energy is likely to be released from the weakest surface under compression,which triggers the global failure of rocks.XIE HePing 1,2,LI LiYun 2,1,JU Yang 2,PENG RuiDong 2 & YANG YongMing 2 1 Sichuan University,Chengdu 610065,China 2 State Key Laboratory of Coal Resources and Safe Mining,Beijing Key Laboratory of Fracture and Damage Mechanics of Rock and Concrete,China University of Mining and Technology,Beijing 100083,China 2011Science China(Technological Sciences)2011,54,S1:29
4Occurrence and assessment of veterinary antibiotics in swine manures:A case study in East China显示文摘We investigated the occurrence of 14 selected antibiotics including five therapeutic classes of tetracyclines,sulfonamides,macrolides,fluoroquinolones and chloramphenicols in manures collected from four swine farms of different sizes in eastern China.Tetracyclines(tetracycline,oxytetracycline,chlortetracycline,and doxycycline) and sulfadiazine were the most prominent contaminants in the manure samples,with maximum concentrations reaching 98.2 × 10 3,354.0 × 10 3,139.4 × 10 3,37.2× 10 3,and 7.1× 10 3 μg/kg,respectively.The occurrence of these compounds was dependent on breeding scale,animal type,and breeding season.Manure storage and vermiculture were not able to effectively deplete the heavier contaminants(tetracyclines and sulfadiazine),resulting in high levels of these chemicals remaining in manures.Therefore,the occurrence of these antibiotics in agricultural soils(0.1-205.1 μg/kg) collected from four types of agricultural land(pear orchard,tea plantation,bamboo forest,and paddy field) near the studied farms,was a reflection of manure application.However,the extremely high concentrations of antibiotics in manures were unlikely from feed consumption,but from other direct forms of medicine application.CHEN YongShan ZHANG HaiBo LUO YongMing SONG Jing 2012Chinese Science Bulletin2012,57,6:29
5An experimental investigation on the mechanism of fluid flow through single rough fracture of rock显示文摘The structure of fractures in nature rock appears irregular and induces complicated seepage flow behavior.The mechanism and quantitative description of fluid flow through rock fractures is a difficult subject that has been greatly concerned in the fields of geotechnical,mining,geological,and petroleum engineering.In order to probe the mechanism of fluid flow and the effects of rough structures,we conducted a few laboratory tests of fluid flow through single rough fractures,in which the Weierstrass-Mandelbrot fractal function and PMMA material were employed to produce the fracture models with various fractal roughnesses.A high-speed video camera was employed to record the fluid flow through the entire single rough fracture with a constant hydraulic pressure.The properties of fluid flow varying with the fracture roughness and the influences of the rough structure were analyzed.The components of flow resistance of a single rough fracture were discussed.A fractal model was proposed to relate the fluid resistance to the fracture roughness.A fractal equivalent permeability coefficient of a single rough fracture was formulated.This study aims to provide an experimental basis and reference for better understanding and quantitatively relating the fluid flow properties to the structures of rock fractures.JU Yang ZHANG QinGang YANG YongMing XIE HePing GAO Feng WANG HuiJie 2013Science China(Technological Sciences)2013,56,8:28
6Computation of fractal dimension of rock pores based on gray CT images显示文摘The characterization of pore structure in rocks is relevant in determining their various mechanical behaviors. Digital image processing methods integrated with fractal theory were applied to analyze images of rock slices obtained from industry CT, elucidating the characteristics of rock pore structure and the relationship between porosity and fractal dimensions. The gray values of pixels in CT images of rocks provide comprehensive results with respect to the attenuation coefficients of various materials in corresponding rock elements, and these values also reflect the effect of rock porosity at various scales. A segmentation threshold can be determined by inverse analysis based on the pore ratios that are measured experimentally, and subsequently binary images of rock pores can be obtained to study their topological structures. The fractal dimension of rock pore structure increases with an increase in rock pore ratio, and fractal dimensions might differ even if pore ratios are the same. The more complex the structure of a rock, the larger the fractal dimension becomes. The experimental studies have validated that fractal dimension calculated directly from gray CT images of rocks can give an effective complementary parameter to use alongside pore ratios and they can suitably represent the fractal characteristics of rock pores.PENG RuiDong YANG YanCong JU Yang MAO LingTao YANG YongMing 2011Chinese Science Bulletin2011,56,31:25
7Microwave photocatalytic degradation of Rhodamine B using TiO_2 supported on activated carbon:Mechanism implication显示文摘The photocatalytic degradation of Rhodamine B(RhB) was carried out using TiO2 supported on activated carbon(TiO2-AC) under microwave irradiation.Composite catalyst TiO2-AC was prepared and characterized using X-ray diffraction(XRD),transmission electron microscopy(TEM) and Brunauer-Emmett-Teller(BET).In the process of microwave-enhanced photocatalysis(MPC),RhB(30 mg/L) was almost completely decoloured in 10 min,and the mineralization effciency was 96.0% in 20 min.The reaction rate constant of RhB in MPC using TiO2-AC by pseudo first-order reaction kinetics was 4.16 times of that using Degussa P25.Additionally,according to gas chromatography/mass spectrometry(GC/MS) and liquid chromatography/mass spectrometry(LC/MS) identification,the major intermediates of RhB in MPC included two kinds of N-de-ethylation intermediates(N,N-diethyl-N'-ethyl-rhodamine(DER)),oxalic acid,malonic acid,succinic acid,and phthalic acid,maleic acid,3-nitrobenzoic acid,and so on.The degradation of RhB in MPC was mainly attributed to the destruction of the conjugated structure,and then the intermediates transformed to acid molecules which were mineralized to water and carbon dioxide.HE Zhong,YANG Shaogui,JU Yongming,SUN Cheng State Key Laboratory of Pollution Control and Resource Reuse,School of the Environment,Nanjing University,Nanjing 210093,China. 2009Journal of Environmental Sciences2009,21,2:22
8Prognostic nutritional index is an independent prognostic factor for gastric cancer patients with peritoneal dissemination显示文摘Objective: The predictive and prognostic role of prognostic nutritional index(PNI) in gastric cancer patients with peritoneal dissemination remains unclear. This study aims to explore the role of the PNI in predicting outcomes of gastric cancer patients with peritoneal dissemination.Methods: A total of 660 patients diagnosed with gastric adenocarcinoma with peritoneal metastasis between January 2000 and April 2014 at Sun Yat-sen University Cancer Center and the Sixth Affiliated Hospital of Sun Yatsen University were retrospectively analyzed. The clinicopathologic characteristics and clinical outcomes of patients with peritoneal dissemination were analyzed.Results: Compared with PNI-high group, PNI-low group was correlated with advanced age(P=0.036), worse performance status(P<0.001), higher frequency of ascites(P<0.001) and higher frequency of multisite distant metastasis(P<0.001). Kaplan-Meier survival curves showed that PNI-high group had a significantly longer median overall survival than PNI-low group(13.13 vs. 9.03 months, P<0.001). Multivariate survival analysis revealed that Borrmann type IV(P=0.014), presence of ascites(P=0.017) and lower PNI(P=0.041) were independent poor prognostic factors, and palliative surgery(P<0.001) and first-line chemotherapy(P<0.001) were good prognostic factors. For patients receiving palliative surgery, the postoperative morbidity rates in the PNI-low group and PNIhigh group were 9.1% and 9.9%, respectively(P=0.797). The postoperative mortality rate was not significantly different between PNI-low and PNI-high groups(2.3% vs. 0.9%, P=0.362).Conclusions: PNI is a useful and practical tool for evaluating the nutritional status of gastric cancer patients with peritoneal dissemination, and is an independent prognostic factor for these patients.Runcong Nie Shuqiang Yuan Shi Chen Xiaojiang Chen Yongming Chen Baoyan Zhu Haibo Qiu Zhiwei Zhou Junsheng Peng Yingbo Chen 2016Chinese Journal of Cancer Research2016,28,6:19
9Modeling study of residence time and water age in Dahuofang Reservoir in China显示文摘Understanding the dynamics of water renewal in a reservoir is essential when the transport and fate of dissolved substances are evaluated.A three-dimensional hydrodynamic model was implemented to compute average residence time and water age in Dahuofang Reservoir in China.The model was verified for a one-year time period in 2006.A simulation reproduced intra-annual variation of mixing represented by the fall/winter mixing and the spring/summer stratification.The simulated variation of vertical thermal structures also matched observation.The spatially varying average residence times and age distribution were investigated through a series of numerical experiments using a passively dissolved and conservative tracer as a surrogate.Residence time estimations yield a broad range of values depending on the position.The average residence time for a tracer placed at the head of the reservoir under high-,mean-,and low flow conditions was found to be about 125,236 and 521 days,respectively.The age simulation reveals that the age distribution is a function of the freshwater discharge.In the vertical direction,the age of the surface layers is larger than that of the bottom layers and the age difference between the surface and bottom layers decreases further downstream.The density-induced circulation plays an important role in the circulation in the reservoir,and can generate vertical age distribution in the reservoir.These findings provide useful information for understanding the transport process in Dahuofang Reservoir that can be used to assist the water quality management of the reservoir.SHEN YongMing WANG JinHua ZHENG BingHui ZHEN Hong FENG Yu WANG ZaiXing YANG Xu 2011Science China(Physics,Mechanics & Astronomy)2011,54,1:18
10Observer-based adaptive fuzzy backstepping control of uncertain nonlinear pure-feedback systems显示文摘In this paper,a new fuzzy adaptive control approach is developed for a class of SISO uncertain pure-feedback nonlinear systems with immeasurable states.Fuzzy logic systems are utilized to approximate the unknown nonlinear functions;and the filtered signals are introduced to circumvent algebraic loop systems encountered in the implementation of the controller,and a fuzzy state adaptive observer is designed to estimate the immeasurable states.By combining the adaptive backstepping technique,an adaptive fuzzy output feedback control scheme is developed.It is proven that the proposed control approach can guarantee that all the signals of the resulting closed-loop system are semi-globally uniformly ultimately bounded(SGUUB),and the observer and tracking errors converge to a small neighborhood of the origin by appropriate choice of the design parameters.Simulation studies are included to illustrate the efectiveness of the proposed approach.TONG ShaoCheng LI YongMing 2014Science China(Information Sciences)2014,57,1:17
11Development and validation of a three-dimensional,wave-current coupled model on unstructured meshes显示文摘Using unstructured meshes provides great flexibility for modeling the flow in complex geomorphology of tidal creeks,barriers and islands,with refined grid resolution in regions of interest and not elsewhere.In this paper,an unstructured three-dimensional fully coupled wave-current model is developed.Firstly,a parallel,unstructured wave module is developed.Variations in wave properties are governed by a wave energy equation that includes wave-current interactions and dissipation representative of wave breaking.Then,the existing Finite-Volume Coastal Ocean Model(FVCOM) is modified to couple with the wave module.The couple procedure includes depth dependent wave radiation stress terms,Stokes drift,vertical transfer of wave-generated pressure transfer to the mean momentum equation,wave dissipation as a source term in the turbulence kinetic energy equation,and mean current advection and refraction of wave energy.Several applications are presented to evaluate the developed model.In particular the wind and wave-induced storm surge generated by Hurricane Katrina is investigated.The obtained results have been compared to the in situ measurements with respect to the wave heights and water level elevations revealing good accuracy of the model in reproduction of the investigated events.In a comparison to water level measurements at Dauphin Island,inclusion of the wave induced water level setup reduced the normalized root mean square error from 0.301 to 0.257 m and increased the correlation coefficient from 0.860 to 0.929.Several runs were carried out to analyze the effects of waves.The experiments show that among the processes that represent wave effects,radiation stress and wave-induced surface stress are more important than wave-induced bottom stress in affecting the water level.The Hurricane Katrina simulations showed the importance of the inclusion of the wave effects for the hindcast of the water levels during the storm surge.WANG JinHua SHEN YongMing 2011Science China(Physics,Mechanics & Astronomy)2011,54,1:16
12Flexible fiber-shaped supercapacitors based on hierarchically nanostructured composite electrodes显示文摘新奇所有固态的、同轴的、塑造纤维的不对称的 supercapacitor 被在 MnO 上包一张进行的复写纸制作了 < 潜水艇 class= “ a-plus-plus ” > 2 -modified nanoporous 金牌电线。这根精力电线展出 12 mFHenghui Xu Xianluo Hu Yongming Sun Huiling Yang Xiaoxiao Liu Yunhui Huang 2015Nano Research2015,8,4:14
13A Collinearity-Incorporating Homology Inference Strategy for Connecting Emerging Assemblies in the Triticeae Tribe as a Pilot Practice in the Plant Pangenomic Era显示文摘Plant genome sequencing has dramatically increased,and some species even have multiple high-quality reference versions.Demands for clade-specific homology inference and analysis have increased in the pangenomic era.Here we present a novel method,GeneTribe(http://gffzz6c7fcf032cb94ff5s99vxoppcbuqn6oq6.ffgz.tsg.suse.edu.cn/genetribe/),for homology inference among genetically similar genomes that incorporates gene collinearity and shows bet-ter performance than traditional sequence-similarity-based methods in terms of accuracy and scalability.The Triticeae tribe is a typical allopolyploid-rich clade with complex species relationships that includes many important crops,such as wheat,barley,and rye.We built Triticeae-GeneTribe(http://gffzzaeec8df70e7c4b21h99vxoppcbuqn6oq6.ffgz.tsg.suse.edu.cn/TGT/),a homology database,by integrating 12 Triticeae genomes and 3 outgroup model genomes and implemented versatile analysis and visualization functions.With macrocollinearity analysis,we were able to construct a refined model illustrating the structural rearrangements of the 4A-5A-7B chromosomes in wheat as two major translocation events.With collinearity analysis at both the macro-and microscale,we illustrated the complex evolutionary history of homologs of the wheat vernalization gene Vm2,which evolved as a combined result of genome translocation,duplication,and polyploidization and gene loss events.Our work provides a useful practice for connecting emerging genome assemblies,with awareness of the extensive polyploidy in plants,and will help researchers efficiently exploit genome sequence re-sources.Yongming Chen Wanjun Song Xiaoming Xie Zihao Wang Panfeng Guan Huiru Peng Yuannian Jiao Zhongfu Ni Qixin Sun Weilong Guo 2020Molecular Plant2020,13,12:14
14Numerical study of pollutant movement in waves and wave-induced long-shore currents in surf zone显示文摘Water waves,wave-induced long-shore currents and movement of pollutants in waves and currents have been numerically studied based on the hyperbolic mild-slope equation,the shallow water equation,as well as the pollutant movement equation,and the numerical results have also been validated by experimental data. It is shown that the long-shore current velocity and wave set-up increase with the increasing incident wave amplitude and slope steepness of the shore plane; the wave set-up increases with the increasing incident wave period;and the pollutant morement proceeds more quiekly with the increasing incident wave amplitude and slope steepness of the shore palane. In surf zones,the long-shore currents induced by the inclined incident waves have effectively affected the pollutant movement.TANG Jun SHEN Yongming QIU Dahong 2008Acta Oceanologica Sinica2008,27,1:13
15Reactive adsorption of thiophene on Ni/ZnO adsorbent:Effect of ZnO textural structure on the desulfurization activity显示文摘To better understand the nature of reactive adsorption of thiophene on Ni/ZnO adsorbent,the effect of ZnO textural structure on the desulfurization activity was investigated.ZnO materials were synthesized by low-temperature solid-state reaction and the corresponding Ni/ZnO adsorbents were prepared by incipient impregnation method.The analysis results showed that the crystalline sizes of ZnO as-synthesized as well as the BET surface areas varied obviously with the calcination temperature.The activity evaluations indicated that the Ni/ZnO adsorbents prepared with ZnO possessed a favorable textural structure as active component exhibited good activity of removing thiophene.The evolutions of the main crystalline phases of Ni/ZnO adsorbents before and after reaction confirmed that ZnO played a crucial role in taking up S element and converting it into ZnS in the reactive adsorption process.It was concluded that ZnO with larger surface area and smaller crystal particles resulted in better desulfurization activity,which may be the main reason for the different activities of the Ni/ZnO adsorbents prepared with ZnO calcined at different temperatures.Jingcheng Zhang Yunqi Liu Shuang Tian Yongming Chai Chenguang Liu 2010Journal of Natural Gas Chemistry2010,19,3:13
16Complex variable method for an anti-plane elliptical cavity of one-dimensional hexagonal piezoelectric quasicrystals显示文摘Based on the fundamental equations of piezoelasticity of quasicrystal media, using the symmetry operations of point groups, the linear piezoelasticity behavior of one-dimensional(1D)hexagonal quasicrystals is investigated and the piezoelasticity problem of 1D hexagonal quasicrystals is decomposed into two uncoupled problems, i.e., the classical plane elasticity problem of conventional hexagonal crystals and the phonon–phason-electric coupling elasticity problem of1 D hexagonal quasicrystals.The final governing equations are derived for the phonon–phasonelectric coupling anti-plane elasticity of 1D hexagonal quasicrystals.The complex variable method for an anti-plane elliptical cavity in 1D hexagonal piezoelectric quasicrystals is proposed and the exact solutions of complex potential functions, the stresses and displacements of the phonon and the phason fields, the electric displacements and the electric potential are obtained explicitly.Reducing the cavity into a crack, the explicit solutions in closed forms of electro–elastic fields,the field intensity factors and the energy release rate near the crack tip are derived.Yu Jing Guo Junhong Xing Yongming 2015Chinese Journal of Aeronautics2015,28,4:13
17Occurrence and distribution of antibiotic resistance genes in the sediments of the East China Sea bays显示文摘The coastal area of the East China Sea has experienced rapid urbanization and industrialization in China since 1980 s, resulting in severe pollution of its environments.Antibiotic resistance genes(ARGs) are regarded as a kind of emerging pollutant with potential high risk. The sediment samples were collected from Hangzhou Bay(HB),Xiangshan Bay(XB), and Taizhou Bay(TB) to investigate the spatial occurrence and distribution of 27 ARGs and class I integron–integrase gene(intI1) in the coastal area of the East China Sea. The PCR results showed the frequent presence of 11 ARGs and intI1 in the sediments of the three bays. The qPCR results further showed that sulfonamide resistance was the most prevalent ARG type and antibiotic target replacement and protection were the most important resistance mechanisms in the sediments. Regarding the subtype of ARGs, sulI, tetW, and dfrA13 were the most abundant ARGs, in which sulI was higher in TB(based on both the absolute and relative abundances) and dfrA13 was higher in HB(based on the relative abundances). The network analysis revealed that intI1 had significant correlations with tetC, sulI, sulII, and blaPSE-1. Oil was the key connected factor, which had positive connections with sulI, sulII, and blaPSE-1. In addition, the joint effect of heavy metals and nutrients & organic pollutants might be crucial for the fate of ARGs in the coastal sediments.Jiayu Chen Zhiguo Su Tianjiao Dai Bei Huang Qinglin Mu Yongming Zhang Donghui Wen 2019Journal of Environmental Sciences2019,31,7:13
18NgAgo-based fabplla gene knockdown causes eye 3evelopmental defects in zebrafish显示文摘Yinyin Qin Yongming Wang Dong Liu 2016Cell Research2016,26,12:13
19Laboratory investigation on mechanisms of stress wave propagations in porous media显示文摘A number of porous models having the similar statistical characteristics of pores and physical properties with natural sandstones have been produced using reactive powder concrete(RPC) and polystyrenes.Spit-Hopkinson-Pressure-Bar tests and CT scans have been carried out on the models with the various porosities to probe the performance of wave propagations and the responses of pores and the matrix during wave propagations.It is shown that porosities significantly influence wave propagations.For an identical impact strain rate,the greater the porosity is,the larger the amplitude of the reflected wave appears,the more the peak in the reflected wave presents,and the smaller the amplitude of the trans-mitted wave turns out.A single peak emerges in the reflected wave when the porosity falls down to 5%.The larger the impact strain rate,the much remarkable the phenomena.The energy-dissipated ratio of porous models,i.e.,WJ /WI,linearly increases with the increment of porosities.The ratio is sensitive to the impact strain rate.Differences in the performance of wave propagations and energy dissipation result from the varied mechanisms that pores response to impacts.For the porosity less than 10%,the mechanism appears to be a process fracturing the matrix to generate new surfaces or pores.Energy has primarily been dissipated in creating new surfaces or pores.No apparent pore deformation takes place.The impact strain rate takes little effect on pore geometry.For the porosity of 15% or more,the mechanism works depending on the impact strain rate.When a low impact strain rate applies,the mechanism still appears to crack the matrix to generate surfaces or pores,but the amount is lower as compared to the case with a low porosity.If a large impact stain rate applies,the mechanism combines both fracturing the matrix and deforming the pores,with the deforming pores predominating.The vast majority of energy has been dissipated to deform pores.Only high porosity and impact strain rate can bring significant deformation to the pores.The proposed eccentricity of pores is capable of character-izing the geometry of pores and its change during wave propagations.JU Yang YANG YongMing MAO YanZhe LIU HongBin WANG HuiJie 2009Science China(Technological Sciences)2009,52,5:13
20Robust adaptive fuzzy backstepping output feedback tracking control for nonlinear system with dynamic uncertainties显示文摘In this paper, an adaptive fuzzy output feedback control approach based on backstepping design is proposed for a class of SISO strict feedback nonlinear systems with unmeasured states, nonlinear uncertainties, unmodeled dynamics, and dynamical disturbances. Fuzzy logic systems are employed to approximate the nonlinear uncertainties, and an adaptive fuzzy state observer is designed for the states estimation. By combining backstepping technique with the fuzzy adaptive control approach, a stable adaptive fuzzy output feedback robust control is constructed recursively, in which nonlinear damping terms and a dynamical signal are introduced to counteract the nonlinear uncertainties and dominate the dynamic disturbances, respectively. It is proved that the proposed adaptive fuzzy control approach guarantees that all the signals of the closed-loop system are semi-globally uniformly bounded, and the tracking error converges to a small neighborhood of the origin. Simulation studies are included to illustrate the effectiveness of the proposed approach.TONG ShaoCheng & LI YongMing Department of Basic Mathematics, Liaoning University of Technology, Jinzhou 121001, China 2010Science China(Information Sciences)2010,53,2:13
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