检索结果-南通市图书馆

Channel estimation for multi-panel millimeter wave MIMO based on joint compressed sensing

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2020年第6期27卷 1-7,29页

作者： liu xu Xie Yang College of Telecommunications and Information Engineering Nanjing University of Posts and TelecommunicationsNanjing 210023China Jiangsu Key Laboratory of Wireless Communications Nanjing University of Posts and TelecommunicationsNanjing 210023China

Channel state information(CSI)is essential for downlink transmission in millimeter wave(mmWave)multiple input multiple output(MIMO)***-panel antenna array is exploited in mmWave MIMO system due to its superior *** channel estimation algorithms are proposed in this paper,named as generalized joint orthogonal matching pursuit(G-JOMP)and optimized joint orthogonal matching pursuit(O-JOMP)for multi-panel mmWave MIMO system based on the compressed sensing(CS)theory.G-JOMP exploits common sparsity structure among channel response between antenna panels of base station(BS)and users to reduce the computational complexity in channel estimation.O-JOMP algorithm is then developed to further improve the accuracy of channel estimation by optimal panel selection based on the power of the received *** results show that the performance of the proposed algorithms is better than that of the conventional orthogonal matching pursuit(OMP)based algorithm in multi-panel mmWave MIMO system.

关键词： channel estimation multi-panel MIMO millimeter wave joint orthogonal matching pursuit common sparsity

Development of a micro gas turbine combustor with T-type vaporizers

在线全文

学校读者我要写书评

暂无评论

航空动力学报 2007年第7期22卷 1118-1126页

作者： xu Quan-hong liu Jun xu Jian LIN Yu-zhen liu Gao-en National Key Laboratory on Aero-Engines School of Jet PropulsionBeijing 13niversity of Aeronautics and Astronautics Beijing 100083 China

The study includes the experimental investigation of the evaporation performance of T-type vaporizer,mainly studied the relationship of the inlet air temperature and vaporizer wall temperature with the evaporation ***,it studied the LBO(lean blow out) and combustion efficiency of the micro aero-engine combustor with T-type vaporizer on the normal pressure test *** inlet air condition is environmental pressure and *** gas analysis method is used to study the combustion efficiency,and the inlet air temperature is 300 K,400 K and 500 *** could be concluded that the evaporation performance is improved with the increasing of the inlet air temperature and vaporizer wall temperature;the average LBO is 0.003;the combustion efficiency rises with the inlet air temperature,and it remain constant when the fuel/air ratio changed in the range from 0.008 to *** vaporization ratio is the key factor to determine the combustion performance.

关键词：离心式喷气发动机燃烧室喷雾器索特平均直径燃气涡轮

Rotor hypothesis in the time chain of atrial fibrillation

在线全文

学校读者我要写书评

暂无评论

Journal of Geriatric Cardiology 2022年第4期19卷 251-253页

作者： Chang-Hao xu xu liu Department of Cardiology Shanghai Chest HospitalShanghai Jiao Tong UniversityShanghaiChina

Atrial fibrillation(AF)is the most preval-ent arrhythmia in the aging population,with people over 75 years accounting for 70%of the AF population.[1]Over the past twe-nty years,despite tremendous progress has been made in catheter ablation for rhythm control of AF,we still cannot establish a reliable ablative target for non-paroxysmal *** of the reason is an incomplete understanding of the mechanism underlying the pro-gressive nature of *** the time chain of AF,AF bur-den increases,and the success rate of catheter abla-tion decreases as AF progresses from paroxysmal AF(PAF)to persistent AF(PerAF)and long-stand-ing persistent AF(LS-PerAF)***,with the advance in mapping technologies combined with biophysical insight,a new concept of AF mainten-ance has been introduced--the rotor(spiral waves).Meanwhile,the concept of complete electrical left atr-ial(LA)isolation has been introduced for AF with ext-ensive atrial *** innovative ideas en-riched our armamentarium to combat different AF *** article proposes a rotor hypothesis to illustrate the mechanism underlying AF progress and discuss the application of new strategies in dif-ferent AF subtypes.

关键词： fibrillation atrial hypothesis

Assessment of tree-ring mercury radial translocation and age effect in Masson pine:Implications for historical atmospheric mercury reconstruction

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2024年第4期138卷 266-276页

作者： xu liu xun Wang Dingyong Wang College of Resources and Environment Southwest UniversityChongqing 400715China State Key Laboratory of Environmental Geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China

The tree ring has been regarded as an emerging archive to reconstruct historical atmospheric mercury(Hg)trends,but with the large knowledge gaps in the *** this study,we comprehensively evaluated the Hg source,radial translocation and age effect of Masson pine(Pinus massoniana)tree ring at *** in Chongqing,to assess the suitability of such tree ring as the archive of atmospheric *** showed that distinct variabilities among Masson pine tree-ring Hg concentration *** Hg concentration significantly increased along with stem height(P<0.05),indicating the Hg in tree rings mainly derived from foliage uptake atmospheric *** found a distinct age effect that the tree ring of young trees had the higher Hg ***,we used the advection-diffusion model to demonstrate how Hg concentration shifted by the advection or/and diffusion in tree *** modeling results showed that the advection induced radial translocation during the young growth period of tree was a plausible mechanism to result in the tree-ring Hg record largely different from the trend of anthropogenic Hg emissions in *** finally suggest that in further Hg dendrochemistry,better discarding the tree-ring Hg profile of the young growth period to reduce impacts of the radial translocation and age effect.

关键词： Masson pine Tree-ring mercury Radial translocation Tree age effect

Distribution Estimation with Smoothed Auxiliary Information

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2011年第1期27卷 167-176页

作者： xu liu Ahmad Ishfaq Department of Statistics Yunnan University Kunming 650091 China Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China

Distribution estimation is very important in order to make statistical inference for parameters or its functions based on this distribution. In this work we propose an estimator of the distribution of some variable with non-smooth auxiliary information, for example, a symmetric distribution of this variable, A smoothing technique is employed to handle the non-differentiable function. Hence, a distribution can be estimated based on smoothed auxiliary information. Asymptotic properties of the distribution estimator are derived and analyzed. The distribution estimators based on our method are found to be significantly efficient than the corresponding estimators without these auxiliary information. Some simulation studies are conducted to illustrate the finite sample performance of the proposed estimators.

关键词： Auxiliary information Empirical likelihood Estimating equations Smoothed estimating function,Symmetric distribution

INVESTIGATION ON APPLICABILITY OF VARIOUS STRESS DEFINITIONS IN ATOMISTIC SIMULATION

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2009年第6期22卷 644-649页

作者： Ran xu Bin liu AML Department of Engineering Mechanics Tsinghua University Beijing 100084 China

How to correctly extract Cauchy stress from the atomistic simulations is a crucial issue in studying the mechanical behaviours of atomic systems, but is still in controversy. In this paper, three typical atomistic simulation examples are used to validate various existing stress definitions. It is found that the classical virial stress fails in predicting the stresses in these examples, because the velocity depends on the choice of the local average volume or the reference frame velocity and other factors. In contrast, the Lagrangian cross-section stress and Lagrangian virial stress are validated by these examples, and the instantaneous Lagrangian atomic stress definition is also proposed for dynamical problems.

关键词： atomic stress virial stress atomistic simulation

Selective reduction of carbon dioxide into amorphous carbon over activated natural magnetite

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2021年第2期28卷 231-237页

作者： Zhong-qing liu Jian Zheng Yi Wang xu liu School of Chemical Engineering Sichuan UniversityChengdu 610065China

Natural magnetite formed by the isomorphism substitutions of transition metals,including Fe,Ti,Co,etc.,was activated by mechanical grinding followed by H2 *** temperature-programmed reduction of hydrogen(H2-TPR)and temperature-programmed surface reaction of carbon dioxide(CO2-TPSR)were carried out to investigate the processes of oxygen loss and CO2 *** samples were characterized by X-ray diffraction(XRD),field emission scanning electron microscopy(FE-SEM),and energy-dispersive X-ray spectroscopy(EDS).The results showed that the stability of spinel phases and oxygen-deficient degree significantly increased after natural magnetite was mechanically milled and reduced in H2 ***,the activity and selectivity of CO2 reduction into carbon were *** deposited carbon on the activated natural magnetite was confirmed as *** amount of carbon after CO2 reduction at 300°C for 90 min over the activated natural magnetite was 2.87wt%higher than that over the natural magnetite.

关键词： carbon dioxide reduction natural magnetite isomorphism substitutions grind activation oxygen-deficient degree amorphous carbon

A new formula on the Fresnel reflectance and its application in microwave remote sensing

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2004年第11期47卷 1045-1052页

作者： xu Qing liu Yuguang Key Laboratory of Physical Oceanography of the Ministry of Education Ocean University of China Qingdao 266003 China Key Laboratory of Physical Oceanography of the Ministry of Education Ocean University of China Qingdao 266003 China

A new formula on the Fresnel reflectance is derived based on our understanding of the complex index of refraction and continuity condition of the E-M waves across the interface between two media. The imaginary component of the complex index of refraction is related to the attenuation of the E-M waves propagating in a medium. It does not denote the phase of the E-M waves. The traditional derivation confuses the physical meaning of the imaginary component of the complex index of refraction. The derived formula on the Fresnel reflectance can be used to obtain the emissivity of sea surface, which is useful to retrieve sea surface temperature and sea surface salinity in the microwave remote sensing.

关键词： reflectance, refraction, microwaves, optics, remote sensing.

Conversion of CH4, steam and O_2 to syngas and hydrocarbons via dielectric barrier discharge

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2009年第1期18卷 94-97页

作者： Baowei Wang xu Zhang Yongwei liu Genhui xu Key Laboratory for Green Chemical Technology of the Ministry qf Education School qf Chemical Engineering and Technology. Tianjin University Tianjin 300072 China

The conversion of CH4 with oxygen and steam in a dielectric barrier discharge （DBD） was studied in the paper to discuss the effects of different factors, such as the content of feed-in gas, the applied voltage and frequency. The results showed that a lower ratio of CH4 to O2 always resulted in a higher conversion of CH4. When it was 2, the conversion reached 32.43% without steam introduced into the system. The main effect of steam was increasing the selectivity to CO. The reaction was accelerated and the selectivities to CO and hydrocarbons were enhanced by increasing the applied voltage. It was also observed that a higher frequency led to a lower current and then restrained the reaction.

关键词： methane steam oxygen dielectric barrier discharges plasma