检索结果-南通市图书馆

TDOA estimation of dual-satellites interference localization based on blind separation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2019年第4期30卷 696-702页

作者： su Ting GAO yong College of Electronics and Information Engineering Sichuan University

The time difference of arrival(TDOA)estimation plays a crucial role in the accurate localization of the satellite interference *** the dual-satellites interference source localization system,the target signal from the adjacent satellite is likely to be interfered by the normal communication signal with the same ***,the signal to noise ratio(SNR)of the target signal would become too low,and the TDOA estimation through cross-correlation processing would be unreliable or even *** paper proposes a technique based on blind separation to solve the co-channel interference problem,where separation of the mixed signal can be carried out by the particle filter(PF)*** experimental results show that the proposed method could achieve more accurate TDOA *** measured data obtained by using the software radio platform at 915 MHz and 2 GHz respectively verify the effectiveness of the proposed method.

关键词： time difference of arrival(TDOA) co-channel interference blind separation particle filter(PF)

Analytic derivation of Monin-Obukhov similarity function for open atmospheric surface layer

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2021年第3期64卷 73-83页

作者： yong Ji Zhen-su She State Key Laboratory for Turbulence and Complex Systems and Department of Mechanics and Engineering Science College of EngineeringPeking UniversityBeijing100871China

The Monin-Obukhov(MO)similarity functionφm of the atmospheric surface layer(ASL)describing the deviation from the log law of the canonical turbulent boundary layer because of thermal stratification has been traditionally determined *** study presents a unified analytic expression derived from a symmetry-based theory of wall turbulence,called structural ensemble dynamics(SED),which postulates a generalized dilation symmetry principle expressing the effect of the wall on turbulence,leading to an analytic multi-regimes expression for the mixing *** ASL in unstable and stable conditions(i.e.,UC and SC),a unified two-regime formula of the mixing length is proposed,leading to aφm,similar to the Businger-Dyer(BD)formula;with a simplified model energy balance equation,φm is completely specified with no free ***,the theory allows the study of the open ASL’s underlying additional physical processes such as bottom-up or top-down flux due to pressure variations *** that Tp is decomposed into shear-like and buoyancy-like components,we propose new explanations for two important features of typical ASL:a significantly smaller Karman constant of 0.36 and a varyingφm for SC mean speed *** theory is validated by the data obtained at Kansas and also at Qingtu Lake Observation Array in Northern China for a variety of heat flux *** conclusion,due to pressure variations,we assert that ASL is intrinsically open and that the current theory offers a new basis for its quantification.

关键词： Monin-Obukhov similarity theory open atmospheric surface layer boundary layer turbulence symmetry-based analysis

Structural designs and mechanism insights into electrocatalytic oxidation of 5-hydroxymethylfurfural

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2025年第1期 792-814页

作者： Jing Lei Huijie Zhang jian Yang Jia Ran Jiqiang Ning Haiyan Wang yong Hu Key Laboratory of the Ministry of Education for Advanced Catalysis Materials Department of Chemistry Zhejiang Normal University Jinhua Advanced Research Institute Department of Optical Science and Engineering Fudan University College of Chemistry and Materials Engineering Zhejiang A&F University

Biomass conversion offers an efficient approach to alleviate the energy and environmental *** oxidation of 5-hydroxymethylfurfural(HMF) has attracted tremendous attention in the latest few years for the mild synthesis conditions and high conversion efficiency to obtain 2,5-furan dicarboxylic acid(FDCA), but there still remain problems such as limited yield, short cycle life,and ambiguous reaction mechanism. Despite many reviews highlighting a variety of electrocatalysts for electrochemical oxidation of HMF, a detailed discussion of the structural modulation of catalyst and the underlying catalytic mechanism is still lacking. We herein provide a comprehensive summary of the recent development of electrochemical oxidation of HMF to FDCA, particularly focusing on the mechanism studies as well as the advanced strategies developed to regulate the structure and optimize the performance of the electrocatalysts, including heterointerface construction, defect engineering,single-atom engineering, and in situ reconstruction. Experimental characterization techniques and theoretical calculation methods for mechanism and active site studies are elaborated, and challenges and future directions of electrochemical oxidation of HMF are also prospected. This review will provide guidance for designing advanced catalysts and deepening the understanding of the reaction mechanism beneath electrochemical oxidation of HMF to FDCA.

关键词：

UREA-BASED POLYACETYLENES AS AN OPTICAL SENSOR FOR FLUORIDE IONS

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2013年第4期31卷 620-629页

作者： Ming-jian su Wen Wan Xue yong Xin-wei Lu 刘瑞源瞿金清 School of Chemistry and Chemical Engineering South China University of Technology School of Pharmaceutical Science Southern Medical University

Novel acetylenes carrying urea groups, 1-（4-ethynylphenyl）-3-（4-nitrophenyl） urea （1）, 1-（4-propargyl）-3-（4- nitrophenyl） urea （2）, were synthesized and polymerized with rhodium catalyst. Polymers [poly（1） and poly（2）] with moderate molecular weights were obtained in good yields. The anion sensing ability of poly（1） and poly（2） was estimated using the tetra-n-butylammonium （TBA） salts of a series of anions in DMF. Upon the addition of F, the color of the DMF solution of poly（1） and poly（2） immediately turned to a different color, while the color of solution changed slightly upon addition of C1, HSO4-, Br-, and NO3-, indicating the F- sensing ability of poly（1） and poly（2）. The 1H-NMR titrations of poly（1） revealed that the colorimetric response of poly（1） was triggered by the urea/F interaction through the hydrogen bonding and/or deprotonation process. The absorption spectra titration and Hill plot analysis were carried out to measure the F binding ability, and the Hill coefficient in the poly（1）/F complexation was found to be 5.8. This result clearly indicated that this binding mode between poly（1） and F was based on a positive homotropic allosterism.

关键词： Polyacetylenes Urea Fluoride ion Ion recognition.

Numerical simulation of temperature field in horizontal core-filling continuous casting for copper cladding aluminum rods

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2013年第7期20卷 684-692页

作者： Ya-jun su Xin-hua Liu yong-fu Wu Hai-you Huang jian-xin Xie Key Laboratory for Advanced Materials Processing (Ministry of Education) Institute of Advanced Materials and Technology Uni- versity of Science and Technology Beijing

The steady-state temperature field of horizontal core-filling continuous casting （HCFC） for producing copper cladding aluminum rods was simulated by finite element method to investigate the effects of key processing parameters on the positions of solid-liquid interfaces （SLIs） of copper and aluminum. It is found that mandrel tube length and mean withdrawing speed have significant effects on the SLI positions of both copper and aluminum. Aluminum casting temperature （TAI）（1003-1123 K） and secondary cooling water flux （600-900 L.h-1） have little effect on the SLI of copper but cause the SLI of aluminum to move 2-4 mm. When TA1 is in a range of 1043-1123 K, the liquid aluminum can fill continuously into the pre-solidified copper tube. Based on the numerical simulation, reasonable processing parameters were determined.

关键词： metal cladding copper aluminum continuous casting interfaces computer simulation

Parameter estimation for rigid body after micro-Doppler removal based on L-statistics in the radar analysis

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2015年第3期26卷 457-467页

作者： yong Wang jian Kang School of Electronics and Information Engineering Harbin Institute of Technology

In traditional inverse synthetic aperture radar （ISAR） imaging of moving targets with rotational parts, the micro-Doppler （m-D） effects caused by the rotational parts influence the quality of the radar images. Recently, L. Stankovic proposed an m-D removal method based on L-statistics, which has been proved effective and simple. The algorithm can extract the m-D effects according to different behaviors of signals induced by rotational parts and rigid bodies in time-frequency （T-F） domain. However, by removing m-D effects, some useful short time Fourier transform （STFT） samples of rigid bodies are also extracted, which induces the side lobe problem of rigid bodies. A parameter estimation method for rigid bodies after m-D removal is proposed, which can accurately re- cover rigid bodies and avoid the side lobe problem by only using m-D removal. Simulations are given to validate the effectiveness of the proposed method.

关键词： parameter estimation L-statistics micro-Doppler (m-D) radar imaging.

Finite element analysis for die casting parameters in high-pressure die casting process

在线全文

学校读者我要写书评

暂无评论

China Foundry 2019年第4期16卷 272-276页

作者： Xin-yu Qin yong su jian Chen Lan-jun Liu School of Materials Science and Engineering Hefei University of Technology

The gating system and the overflow system were designed according to the casting structure during high pressure die casting(HPDC) process. The simulation was carried out by ProCAST software to visualize the injection chamber pre-crystallization and the flow of molten metal. The main work is to research four die casting process parameters, i.e. injection temperature, low-pressure velocity, high-and low-pressure velocity’s switching position, and high-pressure velocity. Experimental results show that the higher injection temperature and lowpressure velocity can mitigate the pre-crystallization of the injection chamber. However, when the low-pressure velocity exceeds 0.2 m·s-1, the air entrapment in the chamber occurs. Besides, when the high-pressure velocity is greater than 2.5 m·s-1, the overflow channel at the final filling position is covered by the liquid metal too early. Finally, the injection temperature of 650 °C, the low-pressure velocity of 0.2 m·s-1, the high-and low-pressure velocity’s switching position of 320 mm and the high-pressure velocity of 2 m·s-1 are obtained as the optimal parameters by the software simulation, which has been verified by actual production.

关键词： aluminum alloy die casting process simulation optimization

Catastrophic Debris Flows on July 10^(th) 2013 along the Min River in Areas Seriously-hit by the Wenchuan Earthquake

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2015年第1期12卷 186-206页

作者： GE yong-gang CUI Peng ZHANG jian-qiang ZENG Chao su Feng-huan Key Laboratory of Mountain Hazards and Earth surface Processes/Chengdu Institute of Mountain Hazards and Environment Chinese Academy of Sciences CAS Center for Excellence in Tibetan Plateau Earth Sciences Sichuan Engineering Research Center for Emergency Mapping & Disaster Reduction

Over 240 debris flows occurred in hill-slopes, gullies （ indicated those with single-channel） and watersheds （indicated those with tributaries and channels） on July 10th 2013 in the Wenchuan county, and caused 29 casualties and about 633×10^6 USD losses. This work aimed to analyze characteristics, hazards and causes of these events and explore mitigating measures based on field investigation and remote sensing images interpretation. The debris flows contained clay content of 0.1%~3.56%, having densities of 1.72-2.14 t/m^3, velocities of 5.0-m.7 m/s, discharges of 335-2353 m^3/s and sediment yields of 0.10-1.26×10^6 m^3, and also numerously occurred in large watersheds with the area over lo km^2. Large debris flows formed 3 hazard-chains in slopes, gullies, watersheds and rivers, which all evolved in dammed lakes and outburst flood, and 26 dammed lakes and lO newly ones were generated along the rivers of Min and Yuzi. The remarkable spatial difference of loose solid materials accumulation and intense rainfall, with the cumulative of about or more than 150 mm and the hourly of over 16mm, caused debris flows in the sections from Yingxiu to Miansi and Gengda. The damages on buildings, reconstructions, highways,factories and hydro power station originated from the impacting, scouring, burying of debris flows, the submerging of dammed lake and the scouring of outburst flood, and the huge losses came from the ruinous destructions of control engineering works of debris flows as well as the irrational location and low- resistant capabilities of reconstructions. For hazards mitigating of debris flows in long term, the feasible measures for short term, including risk-reassessing of foregone and potential hazard sites, regional alarming system establishing and integrated control in disastrous sites, and middle-long term, including improving reconstruction standard, rationally disposing river channel bed rise and selecting appropriate reconstruction time and plans, were strongly

关键词： Debris flows Wenchuan Earthquake Characteristics Damages Causes Preventions

Reflectance Spectral Characteristics of Lunar surface Materials

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2004年第1期4卷 97-104页

作者： yong-LiaoZou jian-ZhongLiu jian-JunLiu TaoXu NationalAstronomicalObservatories ChineseAcademyofSciencesBeijin100012 InstituteofGeochemistry ChineseAcademyofSciencesGuiyang550002

Based on a comprehensive analysis of the mineral composition of major lunarrocks (highland anorthosite, lunar mare basalt and KREEP rock), we investigate the reflectancespectral characteristics of the lunar rock-forming minerals, including feldspar, pyroxene andolivine. The affecting factors, the variation of the intensity of solar radiation with wavelengthand the reflectance spectra of the lunar rocks are studied. We also calculate the reflectivity oflunar mare basalt and highland anorthosite at 300 nm, 415 nm, 750 nm, 900 nm, 950 nm and 1000 nm. Itis considered that the difference in composition between lunar mare basalt and highland anorthositeis so large that separate analyses are needed in the study of the reflectivity of lunar surfacematerials in the two regions covered by mare basalt and highland anorthosite, and especially in theregion with high Th contents, which may be the KREEP-distributed region.

关键词： moon mineral lunar rock