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Deep learning-based time-varying channel estimation with basis expansion model for MIMO-OFDM system 被引量:1
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作者 HU Bo YANG Lihua +1 位作者 REN Lulu NIE Qian 《High Technology Letters》 EI CAS 2022年第3期288-294,共7页
For high-speed mobile MIMO-OFDM system,a low-complexity deep learning(DL) based timevarying channel estimation scheme is proposed.To reduce the number of estimated parameters,the basis expansion model(BEM) is employed... For high-speed mobile MIMO-OFDM system,a low-complexity deep learning(DL) based timevarying channel estimation scheme is proposed.To reduce the number of estimated parameters,the basis expansion model(BEM) is employed to model the time-varying channel,which converts the channel estimation into the estimation of the basis coefficient.Specifically,the initial basis coefficients are firstly used to train the neural network in an offline manner,and then the high-precision channel estimation can be obtained by small number of inputs.Moreover,the linear minimum mean square error(LMMSE) estimated channel is considered for the loss function in training phase,which makes the proposed method more practical.Simulation results show that the proposed method has a better performance and lower computational complexity compared with the available schemes,and it is robust to the fast time-varying channel in the high-speed mobile scenarios. 展开更多
关键词 MIMO-OFDM high-speed mobile time-varying channel deep learning(DL) basis expansion model(BEM)
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ESTIMATION OF BASIS EXPANSION MODELS FOR DOUBLY SELECTIVE CHANNELS
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作者 Liu Yingnan Gao Yonghui +1 位作者 Zhang Nu Liang Qinglin 《Journal of Electronics(China)》 2008年第1期115-119,共5页
By analyzing the relationship between Basis Expansion Model (BEM) and Doppler spectrum, this letter proposed a quasi-MMSE-based BEM estimation scheme for doubly selective channels. Based on the assumption that the bas... By analyzing the relationship between Basis Expansion Model (BEM) and Doppler spectrum, this letter proposed a quasi-MMSE-based BEM estimation scheme for doubly selective channels. Based on the assumption that the basis coefficients are approximately independent and have the same variance for the same channel tap, the quasi-MMSE estimation shows approximately optimal performance and is robust to noise. Moreover, it can avoid a high Peak-to-Average Power Ratio (PAPR) by using continuous pilots. Performance of the proposed estimation scheme has been shown with computer simulations. 展开更多
关键词 Channel estimation Doubly selective channel Basis expansion model (BEM) Meansquare error
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An experimental study of salt expansion in sodium saline soils under transient conditions 被引量:11
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作者 WAN Xusheng YOU Zhemin +1 位作者 WEN Haiyan William CROSSLEY 《Journal of Arid Land》 SCIE CSCD 2017年第6期865-878,共14页
Salt expansion in sulfate saline soils that are widely distributed in northwestern China causes serious infrastructural damages under low-temperature conditions. However, the mechanism of salt expansion under low temp... Salt expansion in sulfate saline soils that are widely distributed in northwestern China causes serious infrastructural damages under low-temperature conditions. However, the mechanism of salt expansion under low temperatures is not clear. In this study, we conducted a series of cooling experiments combined with salt crystallization to study this mechanism, and employed an ionic model to calculate the supersaturation ratio of the solution. During the experiments, the strength and the process of salt expansion were examined under different cooling rates and various crystal morphologies. The relationship between temperature and supersaturation ratio under transient conditions was also considered. Results indicate that the initial supersaturation ratio of a sodium sulfate solution is closely related to environmental conditions, and that this ratio decreases with slowing the cooling rates and stabilizing the crystal forms. Higher initial supersaturation ratios lead to an increased non-steady-state zone, resulting in less salt expansion. On the other hand, chloride ion content has a distinct influence on the crystallization supersaturation ratio of the sodium sulfate solution, and higher chloride ion content can inhibit salt expansion in sodium saline soils. These findings help explain salt expansion mechanisms in complex conditions such as seasonally frozen soils, and thus help search for improved methods of preventing salt expansion in sulfate saline soils. 展开更多
关键词 sulfate saline soil supersaturation ratio ionic model cooling rate salt expansion
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Using Impervious Surfaces to Detect Urban Expansion in Beijing of China in 2000s 被引量:13
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作者 PENG Jian LIU Yanxu +3 位作者 SHEN Hong XIE Pan HU Xiaoxu WANG Yanglin 《Chinese Geographical Science》 SCIE CSCD 2016年第2期229-243,共15页
The change of impervious surface area(ISA) can effectively reveal the gradual process of urbanization and act as a key index for monitoring urban expansion. Experiencing rapid growth of the built environment in the 20... The change of impervious surface area(ISA) can effectively reveal the gradual process of urbanization and act as a key index for monitoring urban expansion. Experiencing rapid growth of the built environment in the 2000 s, urban expansion of Beijing has not been fully characterized through ISA. In this study, Landsat TM images of Beijing in 2001 and 2009 were obtained, and the eight-year urban expansion process in Beijing was analyzed using the ISA extracted by means of the vegetation-imperious surface-soil(V-I-S) model. From the spatial variation in ISA, the ring structure of urban expansion in Beijing was significant during the study period, with decreasing urban density from the city center to the periphery. In the ring road analysis, the most dramatic changes of ISA were found between the fifth ring and the sixth ring. This area has experienced the most new residential development, and is currently the main source of urban expansion. The typical profile lines revealed the directional characteristics of urban expansion. The east-west profile was the most urbanized axes in Beijing, while ISA change in the east-north profile was more significant than in the other five profiles. Moreover, the transition matrix of ISA levels revealed an increase in urban density in the low density built areas; the Moran′s I index showed a clear expansion of the central urban area, which spread contiguously; and the standard deviational ellipse indicated the northeast was the dominant direction of urban expansion. These findings can provide important spatial control guidelines in the next round of national economic and social development planning, overall urban and rural planning, and land use planning. 展开更多
关键词 impervious surface area(ISA) vegetation-imperious surface-soil(V-I-S) model profile line analysis urban expansion direction Beijing China
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The Observable Universe in a Simplified Cosmic Dynamic Model 被引量:1
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作者 Xiaoyun Li La Ba Sakya Genzon +2 位作者 Suoang Longzhou Youping Dai Yangsheng Xu 《Journal of Applied Mathematics and Physics》 2021年第6期1322-1328,共7页
This paper introduces a cosmic expansion model with constant speed of cosmic spatial expansion via derivation and simulations, where the speed of cosmic spatial expansion equals the speed of light <em>c</em&g... This paper introduces a cosmic expansion model with constant speed of cosmic spatial expansion via derivation and simulations, where the speed of cosmic spatial expansion equals the speed of light <em>c</em>. Simulation results show that the earliest observable universe time is <em>t</em> = 5.084 Gyrs where the current universe time <em>T</em> = 13.82 Gyrs, and the furthest observable distance at the earliest observable universe time <em>t</em> is <em>S</em> = 0.632<em>R</em>, where <em>R</em> is the cosmic radius at current universe time <em>T</em>. The above constant cosmic expansion model does not consider the inflation period in the early universe according to the Big Bang model, nor does it considered the cosmic acceleration in recent universe time. However, this simplified cosmic expansion model could be a benchmark that will be helpful to understand the cosmic expansion and the observable universe. Based on the derivation and simulation of the constant cosmic expansion model, the threshold of observable universe for the accelerated cosmic expansion model can also be calculated similarly, as far as the speed of cosmic spatial expansion at any universe time t can be provided. 展开更多
关键词 Observable Universe THRESHOLD SIMULATION Cosmic expansion model
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Various Methods for Constructing Auto-Bcklund Transformations for a Generalized Variable-Coefficient Korteweg-de Vries Model from Plasmas and Fluid Dynamics
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作者 ZHANG Chun-Yi GAO Yi-Tian +5 位作者 XU Tao LI Li-Li SUN Fu-Wei LI Juan MENG Xiang-Hua WEI Guang-Mei 《Communications in Theoretical Physics》 SCIE CAS CSCD 2008年第3期673-678,共6页
In this paper, under the Painleve-integrable condition, the auto-Biicklund transformations in different forms for a variable-coefficient Korteweg-de Vries model with physical interests are obtained through various met... In this paper, under the Painleve-integrable condition, the auto-Biicklund transformations in different forms for a variable-coefficient Korteweg-de Vries model with physical interests are obtained through various methods including the Hirota method, truncated Painleve expansion method, extendedvariable-coefficient balancing-act method, and Lax pair. Additionally, the compatibility for the truncated Painleve expansion method and extended variable-coetfficient balancing-act method is testified. 展开更多
关键词 variable-coefficient Korteweg-de truncated Painleve expansion Schwarzian derivative-scattering Vries models auto-Backlund transformation Hirota method method extended variable-coefficient balancing-act method method Lax pair
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Equatorial Wave Expansion of Instantaneous Flows for Diagnosis of Equatorial Waves from Data:Formulation and Illustration
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作者 Cory BARTON Ming CAI 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2017年第10期1219-1234,共16页
This paper presents a method for expanding horizontal flow variables in data using the free solutions to the shallow-water system as a basis set. This method for equatorial wave expansion of instantaneous flows(EWEIF... This paper presents a method for expanding horizontal flow variables in data using the free solutions to the shallow-water system as a basis set. This method for equatorial wave expansion of instantaneous flows(EWEIF) uses dynamic constraints in conjunction with projections of data onto parabolic cylinder functions to determine the amplitude of all equatorial waves.EWEIF allows us to decompose an instantaneous wave flow into individual equatorial waves with a presumed equivalent depth without using temporal or spatial filtering a priori.Three sets of EWEIF analyses are presented. The first set is to confirm that EWEIF is capable of recovering the individual waves constructed from theoretical equatorial wave solutions under various scenarios. The other two sets demonstrate the ability of the EWEIF method to derive time series of individual equatorial waves from instantaneous wave fields without knowing a priori exactly which waves exist in the data as well as their spatial and temporal scales using outputs of an equatorial β-channel shallow-water model and ERA-Interim data. The third set of demonstrations shows, for the first time, the continuous evolutions of individual equatorial waves in the stratosphere whose amplitude is synchronized with the background zonal wind as predicted by quasi-biennial oscillation theory. 展开更多
关键词 Equatorial wave expansion Instantaneous flows equatorial β-channel shallow-water model
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Joint Multi-Domain Channel Estimation Based on Sparse Bayesian Learning for OTFS System 被引量:7
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作者 Yong Liao Xue Li 《China Communications》 SCIE CSCD 2023年第1期14-23,共10页
Since orthogonal time-frequency space(OTFS)can effectively handle the problems caused by Doppler effect in high-mobility environment,it has gradually become a promising candidate for modulation scheme in the next gene... Since orthogonal time-frequency space(OTFS)can effectively handle the problems caused by Doppler effect in high-mobility environment,it has gradually become a promising candidate for modulation scheme in the next generation of mobile communication.However,the inter-Doppler interference(IDI)problem caused by fractional Doppler poses great challenges to channel estimation.To avoid this problem,this paper proposes a joint time and delayDoppler(DD)domain based on sparse Bayesian learning(SBL)channel estimation algorithm.Firstly,we derive the original channel response(OCR)from the time domain channel impulse response(CIR),which can reflect the channel variation during one OTFS symbol.Compare with the traditional channel model,the OCR can avoid the IDI problem.After that,the dimension of OCR is reduced by using the basis expansion model(BEM)and the relationship between the time and DD domain channel model,so that we have turned the underdetermined problem into an overdetermined problem.Finally,in terms of sparsity of channel in delay domain,SBL algorithm is used to estimate the basis coefficients in the BEM without any priori information of channel.The simulation results show the effectiveness and superiority of the proposed channel estimation algorithm. 展开更多
关键词 OTFS sparse Bayesian learning basis expansion model channel estimation
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一种新型钻孔采样数据管理方案 被引量:3
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作者 刘修国 赵秀忠 《计算机工程》 CAS CSCD 北大核心 2002年第5期219-221,232,共4页
论述了在进行工程勘察软件设计中实际存在的一些问题。针对这些问题在对钻孔采样数据管理时,通过进行科学的数据空间的划分和结构重组提出了一种新型的钻孔数据管理方案,并成功地利用了的维数据处理功能解决了实际存在的困难。文章就该... 论述了在进行工程勘察软件设计中实际存在的一些问题。针对这些问题在对钻孔采样数据管理时,通过进行科学的数据空间的划分和结构重组提出了一种新型的钻孔数据管理方案,并成功地利用了的维数据处理功能解决了实际存在的困难。文章就该方案实现MAPGIS2.5的数据模型以及模型中使用的关键性技术分别进行了阐述。最后讨论了该模型可能存在的问题以及相应的解决方法。 展开更多
关键词 工程勘察软件 设计 钻孔 采样 数据管理方案
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Over-sampling basis expansion model aided channel estimation for OFDM systems with ICI 被引量:3
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作者 LIU Si-yang LIU Yuan-an WANG Fei-fei XIE Gang ZHANG Ran-ran 《The Journal of China Universities of Posts and Telecommunications》 EI CSCD 2008年第4期7-13,共7页
The rapid variation of channel can induce the intercarrier interference in orthogonal frequency-division multiplexing (OFDM) systems. Intercarrier interference will significantly increase the difficulty of OFDM chan... The rapid variation of channel can induce the intercarrier interference in orthogonal frequency-division multiplexing (OFDM) systems. Intercarrier interference will significantly increase the difficulty of OFDM channel estimation because too many channel coefficients need be estimated. In this article, a novel channel estimator is proposed to resolve the above problem. This estimator consists of two parts: the channel parameter estimation unit (CPEU), which is used to estimate the number of channel taps and the multipath time delays, and the channel coefficient estimation unit (CCEU), which is used to estimate the channel coefficients by using the estimated channel parameters provided by CPEU. In CCEU, the over-sampling basis expansion model is resorted to solve the problem that a large number of channel coefficients need to be estimated. Finally, simulation results are given to scale the performance of the proposed scheme. 展开更多
关键词 OFDM ICI over-sampling basis expansion model (OBEM)
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Deep Learning-Based Symbol Detection for Time-Varying Nonstationary Channels 被引量:2
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作者 Xuantao Lyu Wei Feng +1 位作者 Ning Ge Xianbin Wang 《China Communications》 SCIE CSCD 2022年第3期158-171,共14页
The highly dynamic channel(HDC)in an extremely dynamic environment mainly has fast timevarying nonstationary characteristics.In this article,we focus on the most difficult HDC case,where the channel coherence time is ... The highly dynamic channel(HDC)in an extremely dynamic environment mainly has fast timevarying nonstationary characteristics.In this article,we focus on the most difficult HDC case,where the channel coherence time is less than the symbol period.To this end,we propose a symbol detector based on a long short-term memory(LSTM)neural network.Taking the sampling sequence of each received symbol as the LSTM unit's input data has the advantage of making full use of received information to obtain better performance.In addition,using the basic expansion model(BEM)as the preprocessing unit significantly reduces the number of neural network parameters.Finally,the simulation part uses the highly dynamic plasma sheath channel(HDPSC)data measured from shock tube experiments.The results show that the proposed BEM-LSTM-based detector has better performance and does not require channel estimation or channel model information. 展开更多
关键词 highly dynamic channel deep neural network long short-term memory basis expansion model symbol detection
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WRF/CHEM modeling of impacts of weather conditions modified by urban expansion on secondary organic aerosol formation over Pearl River Delta 被引量:25
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作者 Xuemei Wang Zhiyong Wu Guixiong Liang 《Particuology》 SCIE EI CAS CSCD 2009年第5期384-391,共8页
In this paper, the online Weather Research and Forecasting and Chemistry (WRF/CHEM) model, coupled with urban canopy (UCM) and biogenic-emission models, is used to explore impacts of urban expansion on secondary o... In this paper, the online Weather Research and Forecasting and Chemistry (WRF/CHEM) model, coupled with urban canopy (UCM) and biogenic-emission models, is used to explore impacts of urban expansion on secondary organic aerosols (SOA) formation. Two scenarios of urban maps are used in WRF/CHEM to represent early 1990s (pre-urbanization) and current urban distribution in the Pearl River Delta (PRD). Month-long simulation results using the above land-use scenarios for March 2001 show: (1) urbanization can increase monthly averaged temperatures by about 0.63 ℃, decrease monthly averaged 10-m wind speeds by 38%, increase monthly averaged boundary-layer depths by 80 m, and decrease monthly aver- aged water mixing ratio by 0.2g/kg. (2) Changes in meteorological conditions can result in detectable concentration changes of NOx, VOC, O3 and NO3 radicals. Urbanization decreases surface NOx and VOC concentrations by a maximum of 4 ppbv and 1.5 ppbv, respectively. Surface O3 and NO3 radical concentrations over major cities increase by about 2-4 ppbv and 4-12 pptv, respectively; areas with increasing O3 and NO3 radical concentrations generally coincide with the areas of temperature increase and wind speed reduction where NOx and VOC decrease. (3) Urbanization can induce 9% increase of SOA in Foshan, Zhongshan and west Guangzhou and 3% decrease in Shenzhen and Dongguan. Over PRD major cities, SOA from Aitken mode reduces by 30% but with more than 70% SOA from accumulate mode. Urbanization has stronger influence on SOA formation from Aitken mode. (4) Over the PRD, 55-65% SOA comes from aromatics precursors. Urbanization has strongest influence on aromatics precursors to produce SOA (14% increase), while there is less influence on alkane precursors. Alkene precursors have negative contribution to SOA formation under urbanization situation. 展开更多
关键词 Secondary organic aerosol Urban expansion WRF/CHEM model
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LAI scale effect research based on compact airborne spectrographic imager data in the Heihe Oasis 被引量:1
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作者 DAI Xiao-ai LIU Chao +9 位作者 LI Nai-wen WANG Mei-lian YANG Yu-wei YANG Xing-ping ZHANG Shi-qi HE Xu-wei YANG Zheng-li LU Heng LI Jing-zhong WANG Ze-kun 《Journal of Mountain Science》 SCIE CSCD 2021年第6期1630-1645,共16页
As one of the key parameters for characterizing crop canopy structure, Leaf Area Index(LAI) has great significance in monitoring the crop growth and estimating the yield. However, due to the nonlinearity and spatial h... As one of the key parameters for characterizing crop canopy structure, Leaf Area Index(LAI) has great significance in monitoring the crop growth and estimating the yield. However, due to the nonlinearity and spatial heterogeneity of LAI inversion model, there exists scale error in LAI inversion result, which limits the application of LAI product from different remote sensing data. Therefore, it is necessary to conduct studies on scale effect. This study was based on the Heihe Oasis, Zhangye city, Gansu province, China and the following works were carried out: Airborne hyperspectral CASI(Compact Airborne Spectrographic Imager) image and LAI statistic models were adopted in muti-scale LAI inversion. The overall difference of muti-scale LAI inversion was analyzed in an all-round way. This was based on two aspects, "first inversion and then integration" and "first integration and then inversion", and on scale difference characteristics of three scale transformation methods. The generation mechanism of scale effect was refined, and the optimal LAI inversion model was expanded by Taylor expansion. By doing so, it quantitatively analyzed the contribution of various inversion processes to scale effect. It was found that the cubic polynomial regression model based on NDVI(940.7 nm, 712 nm) was the optimal model, where its coefficient of determination R2 and the correlation coefficient of test samples R reached 0.72 and 0.936, respectively. Combined with Taylor expansion, it analyzed the scale error generated by LAI inversion model. After the scale effect correction of one-dimensional and twodimensional variables, the correlation coefficient of CCD-LAI(China Environment Satellite HJ/CCD images) and CASI-LAI products(Compact Airborne Spectro graphic Imager products) increased from 0.793 to 0.875 and 0.901, respectively. The mean value, standard deviation, and relative true value of the two went consistent. Compared with onedimensional variable correction method, the twodimensional method had a better correction result. This research used the effective information in hyperspectral data as sub-pixels and adopted Taylor expansion to correct the scale error in large-scale and low-resolution LAI product, achieving large-scale and high-precision LAI monitoring. 展开更多
关键词 Vegetation index Leaf Area Index Scale effect Taylor series expansion model
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THE SHRINKAGE OF EXPANSIVE CONCRETE FILLED STEEL TUBE AND ITS IMPROVEMENT METHOD
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作者 Li, Y Hu, SG +2 位作者 Ding, QJ Zhou, MK Zhang, YS 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 1999年第1期46-51,共6页
The shrinkage characteristics tics of expansive concrete filled steel tube (CFST) are analyzed, Cold shrinkage, creep and autogenous shrinkage are considered as the main reasons of causing CFST contraction. In accorda... The shrinkage characteristics tics of expansive concrete filled steel tube (CFST) are analyzed, Cold shrinkage, creep and autogenous shrinkage are considered as the main reasons of causing CFST contraction. In accordance with the shrinkage characteristics of expansive CFST, a kind of energy-stored delayed expansive agent is exploited, which can not only compensate the shrinkage of the core concrete in every stages, but also make CFST expand according to the delayed expansion mechanism. As the result, the prestress loss weill be reduced and expansive energy will be utilized effectively. 展开更多
关键词 concrete filled steel tube shrinkage mechanism expansive agent expansive model
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Development of a global high-resolution marine dynamic environmental forecasting system
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作者 WAN Li-Ying LIU Yang LING Tie-Jun 《Atmospheric and Oceanic Science Letters》 CSCD 2018年第5期379-387,共9页
A project entitled‘Development of a Global High-resolution Marine Dynamic Environmental Forecasting System’has been funded by‘The Program on Marine Environmental Safety Guarantee’of The National Key Research and D... A project entitled‘Development of a Global High-resolution Marine Dynamic Environmental Forecasting System’has been funded by‘The Program on Marine Environmental Safety Guarantee’of The National Key Research and Development Program of China.This project will accomplish its objectives through basic theoretical research,model development and expansion,and system establishment and application,with a focus on four key issues separated into nine tasks.A series of research achievements have already been obtained,including datasets,observations,theories,and model results. 展开更多
关键词 Global high-resolution marine dynamic environmental forecasting system basic theoretical research model development and expansion system establishment and application
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A model for expansion ratio in liquid-solid fluidized beds
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作者 Alok Tripathy A.K.Sahu +1 位作者 S.K.Biswal B.K.Mishra 《Particuology》 SCIE EI CAS CSCD 2013年第6期789-792,共4页
Liquid-solid fluidized beds are used in mineral processing industries to separate particles based on parti- cle size, density, and shape. Understanding the expanded fluidized bed is vital for accurately assessing its ... Liquid-solid fluidized beds are used in mineral processing industries to separate particles based on parti- cle size, density, and shape. Understanding the expanded fluidized bed is vital for accurately assessing its performance. Expansion characteristics of the fluidized bed were studied by performing several experi- ments with iron ore, chromite, quartz, and coal samples. Using water as liquid medium, experiments were conducted to study the effects of particle size, particle density, and superficial velocity on fluidized bed expansion. The experimental data were utilized to develop an empirical mathematical model based on dimensional analysis to estimate the expansion ratio of the fluidized bed in terms of particle character- istics, operating and design parameters. The predicted expansion ratio obtained from the mathematical model is in good agreement with the experimental data. 展开更多
关键词 Fluidization Bed expansion Mathematical modelling Dimensional analysis Particle processing Void fraction
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The Cosmic Radius of Observable Universe
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作者 Xiaoyun Li Suoang Longzhou La Ba Sakya Genzon 《Journal of High Energy Physics, Gravitation and Cosmology》 2022年第1期1-13,共13页
This paper introduces three cosmic expansion models with constant, decelerating and accelerating speed of expansion respectively. Then characters of these cosmic expansion models are compared. Based on these cosmic ex... This paper introduces three cosmic expansion models with constant, decelerating and accelerating speed of expansion respectively. Then characters of these cosmic expansion models are compared. Based on these cosmic expansion models, the thresholds of observable universe are calculated via simulations, where the earliest observable cosmic radius <i>R</i>(<i>t<sub>earliest</sub></i>) is always 0.368<i>R</i> (<i>R</i> is cosmic radius at current universe time) for any cosmic expansion models. 展开更多
关键词 Observable Universe THRESHOLD SIMULATION Cosmic expansion model
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Size-and temperature-dependent Young's modulus and size-dependent thermal expansion coefficient of nanowires 被引量:5
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作者 SUN HongLiang CHEN LiuYan +1 位作者 SUN Sheng ZHANG Tong-Yi 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2018年第5期687-698,共12页
Nanowires(NWs) exhibit size-dependent mechanical properties due to the high surface/volume ratio, in which temperature also plays an important role. The surface eigenstress model is further developed here to quantitat... Nanowires(NWs) exhibit size-dependent mechanical properties due to the high surface/volume ratio, in which temperature also plays an important role. The surface eigenstress model is further developed here to quantitatively predict the size-dependent mechanical properties of NWs and results in analytic formulas. Molecular dynamics(MD) simulations are conducted to study the size-dependent mechanical of [100], [110] and [111] Ni and Si nanowires within the temperature range of 100–400 K and the MD results verify perfectly the newly developed surface eigenstress model. 展开更多
关键词 surface eigenstress model size-and temperature-dependent Young's modulus size-dependent thermal expansion coefficient nanowires molecular dynamics simulations
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Deformation characterization method of typical double-walled turbine blade structure during casting process
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作者 Yi-wei Dong Peng-fei Shao +3 位作者 Xiang Guo Bo Xu Chun-ping Yin Zhi-yong Tan 《Journal of Iron and Steel Research International》 SCIE EI CAS CSCD 2023年第10期2010-2020,共11页
To address the complex structures,large out-of-tolerance issues,and inconsistent quality of double-walled turbine blades,a mapping relationship between the structure and deformation was established based on a structur... To address the complex structures,large out-of-tolerance issues,and inconsistent quality of double-walled turbine blades,a mapping relationship between the structure and deformation was established based on a structural correlation study.Numerical simulations and pouring experiments were carried out based on the designed double-walled model,and a reliable displacement field model of the double-walled blade was established.A decoupling method for the displacement field of the double-walled blade castings was proposed,which decoupled the displacement field into bending,torsion,and expansion/shrinkage deformation vectors.Based on the displacement field analysis of the theoretical and physical models,an expansion/shrinkage model of double-walled blade structure castings was established.Furthermore,an experiment to determine the mapping relationship between double-walled construction and deformation was designed,which included the characteristic distribution distance and designed angle as structural parameters.The functional relationship between the deformation and the structural parameters was established based on a nonlinear regression method. 展开更多
关键词 Turbine blade Double-walled structure Deformation decoupling expansion/shrinkage model Structure-deformation mapping
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Doubly selective fading channel estimation in MIMO OFDM systems 被引量:4
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作者 YU Xiaoyan WANG Jiaqing YANG Luxi HE Zhenya 《Science in China(Series F)》 2005年第6期795-807,共13页
High data transmission rates and high mobility give rise to time- and frequency-selectivity in wireless communication channels. This paper investigated time and frequency doubly selective channel estimation using pilo... High data transmission rates and high mobility give rise to time- and frequency-selectivity in wireless communication channels. This paper investigated time and frequency doubly selective channel estimation using pilot tones among Multi-Input Multi-Output (MIMO) orthogonal frequency division multiplexing (OFDM). Firstly, a complex exponential basis expansion channel model (BECM) was introduced to represent doubly selective channel during an OFDM symbol period; then, based on BECM, an effective MIMO-OFDM doubly selective channel estimation method was presented; finally, the optimality in designing pilot tones parameters was done according to the minimization of channel estimation MSE, mainly including the number, the placement and the structure of pilot tones. Simulation results show that the proposed estimation method has good performance in doubly selective channel scenarios and confirms the theoretical analysis findings. 展开更多
关键词 MIMO-OFDM doubly selective channels channel estimation basis expansion channel model.
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