检索结果-南通市图书馆

Resource allocation in downlink OFDMA distributed multipoint systems with incoherent and coherent transmitters

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 2011年第3期18卷 62-68页

作者： WANG tan WANG ying ZHANG Ping Wireless Technology Innovation Institute Key Laboratory of Universal Wireless Communication Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

Distributed multipoint systems （DMS） are important and timely for the move to future broadband wireless communication systems. Traditional studies on DMS have mainly focused on the issues with the spatial division multiple access such as precoding techniques, which only consider a narrowband case. This paper addresses the downlink radio resource management of the orthogonal frequency division multiple access DMS （OFDMA-DMS）, including power allocation between users or subcarriers, and distributed antenna selection. Signal models with incoherent and coherent transmitters are built. To maximize the system throughput, for the incoherent transmitter case, a strategy based on the iterative water-filling power allocation is proposed to approach the optimality. As for the coherent case, where coherent additions of the signal could occur at the users, the problem is transformed into an integer programming which is solvable. Numerical results show that the gain from the coherent transmitter is promising. And to achieve a near-optimal solution, only part of the DA ports will be used, which have better channel conditions.

关键词： DMS orthogonal frequency division multiple access (OFDMA) power allocation antenna port selection

A New Risk Measure MMVaR:Properties and Empirical Research

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2023年第5期36卷 2026-2045页

作者： tan Keqi CHEN yu CHEN Dan Department of Statistics and Finance School of ManagementUniversity of Science and Technology of ChinaHefei 230026China

The paper presents the properties of an alternative method,which measures market risk over time-horizon exceeding one day:Mark to market value at risk(MMVaR).Relying on the minimal returns during the time interval,this method not only considers the non-normality of data and information about sample size,but also meets the requirement of increasing the minimal capital ratio in BaselⅢ,*** authors theoretically prove the translation invariance,monotonicity and subadditivity of MMVaR as a risk measure under some conditions,and study its finite sample properties through Monte Carlo *** empirical analysis shows that MMVaR can measure multi-period risk accurately.

关键词： MMVaR multi-period risk risk measure subadditive

Efficient and rapid capture of uranium(Ⅵ) in wastewater via multiamine modified β-cyclodextrin porous polymer

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2024年第4期68卷 144-155页

作者： Xing Zhong yubin tan Siyuan Wu Caixia Hu Kai Guo Yongchuan Wu Neng yu Mingyang Ma ying Dai School of Chemistry and Materials Science East China University of TechnologyNanchang 330013China

It is quite important to ensure the safety and sustainable development of nuclear energy for the treatment of radioactive wastewater. To treat radioactive wastewater efficiently and rapidly, two multi-amine β-cyclodextrin polymers(diethylenetriamine β-cyclodextrin polymer(DETA-TFCDP) and triethylenetetramine β-cyclodextrin polymer(TETA-TFCDP)) were prepared and applied to capture uranium. Results exhibited that DETA-TFCDP and TETA-TFCDP displayed the advantages of high adsorption amounts(612.2and 628.2 mg·g-1, respectively) and rapid adsorption rates, which can reach(88 ± 1)% of their equilibrium adsorption amounts in 10 min. Moreover, the adsorbent processes of DETA-TFCDP and TETATFCDP on uranium(Ⅵ) followed the Langmuir model and pseudo-second-order model, stating they were mainly chemisorption and self-endothermic. Besides, TETA-TFCDP also showed excellent selectivity in the presence of seven competing cations and could be effectively reused five times via Na2CO3as the desorption reagent. Meanwhile, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy illustrated that the enriched multi-amine groups and oxygen-containing functional groups on the surface of TETA-TFCDP were the main active sites for capturing uranium(Ⅵ). Hence, multi-amine β-cyclodextrin polymers are a highly efficient, rapid, and promising adsorbent for capturing uranium(Ⅵ)from radioactive wastewater.

关键词： Adsorption Waste water Pollution Uranium(VI) b-Cyclodextrin

Electrodeposited transparent PEDOT for inverted perovskite solar cells:improved charge transport and catalytic performances

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2021年第9期40卷 2402-2414页

作者： Cong-tan Zhu ying Yang Fei-yu Lin yuan Luo Shu-Peng Ma Liu Zhu Xue-Yi Guo School of Metallurgy and Environment Central South UniversityChangsha 410083China First Rare Materials Co. LtdQingyuan 511517China

The acidic, corrosive effect of sodium polystyrene sulfonate(PSS) in poly 3,4-ethylenedioxythiophene:sodium polystyrene sulfonate(PEDOT:PSS) limits the stability of inverted perovskite solar cells(PSCs) based on the ITO/PEDOT:PSS/perovskite/PCBM/BCP/Ag structure. In this work, a poly 3,4-ethylenedioxythiophene(PEDOT) hole transport layer(HTL) with high hole mobility and good catalytic performance was prepared by electrochemical cyclic voltammetry(CV) method for inverted PSCs. By controlling the CV cycles(from 1 to 5 cycles) and EDOT monomer solution concentration(from0.5 to 2.0 mmol·L^(-1)) of electrochemical deposition, the thickness, morphology, optical and electrochemical properties of PEDOT could be accurately adjusted. The optimal photovoltaic performance with current density(J_(sc)) of 22.19 mA·cm^(-2), open circuit voltage(V_(oc)) of 0.94 V, fill factor(FF) of 0.65 and photoelectric conversion efficiency of 13.56% was obtained when deposition of PEDOT with 1 CV cycle and EDOT concentration of 0.5 mmol·L^(-1). At this point, the perovskite showed good crystallization,optimal optical, charge transport and recombination performance, resulting in better V_(oc)and photoelectric conversion efficiency(PCE) compared to the devices with higher CV cycle numbers and 3,4-ethylenedioxythiophene(EDOT) concentration. For comparison with spin-coated PEDOT:PSS, the device with electrodeposited PEDOT showed improved J_(sc)and comparable V_(oc), which may result from its better charge transport and catalytic *** device with spin-coated PEDOT:PSS showed photoelectric conversion efficiency of 12.25%, which was lower than that based on electrodeposited PEDOT(13.56%) with1 CV cycles and 0.5 mmol·L^(-1) EDOT concentration. And the device with electrodeposited PEDOT as HTLs showed more excellent air stability. In ambient air((32 ± 5) ℃ and RH: 70% ± 20%), it still maintained more than 80%of the initial photoelectric conversion efficiency after1000 h. In comparison, the photoe

关键词： Electrochemically cyclic voltammetry Inverted perovskite solar cells Electrodeposited PEDOT Hole mobility Tafel analysis

Numerical Simulation and Vertical Motion Control of Rolls for Variable Gauge Rolling

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2015年第8期22卷 703-708页

作者： yu ZHANG Jian tan School of Mechatronics and Automotive Engineering Chongqing Jiaotong University Rolling Mill Chongqing Iron & Steel Co. Ltd.

The vertical motion control of the roll was studied in order to improve the accuracy in simulation of variable gauge rolling. The discretization was carried out in the transition zone of TRB according to the principle of volume invariance. Based on this assumption, the formula for time step of vertical motion of rolls was proposed and the time-displacement curve of the verti- cal motion of rolls was established. In the preliminary simulation, the time-displacement curve was used as an initial method to control the vertical motion of rolls. Based on the simulation result, the formula for vertical velocity of roll in variable gauge rolling was derived from the common rolling principle. According to the formula, reasonable vertical velocity of rolls in the subsequent simulation was determined. It can accurately control the motion of rolls along the vertical direction. The desired thickness and out- line profile of transition zone were acquired and the formula proved effective by the simulation. Further analysis shows that the di fference of thickness in the thick zone and the thin zone of TRB, length of the transition zone of TRB, radius of work rolls and rota- tion speed of rolls have a significant effect on the vertical velocity of rolls.

关键词： variable gauge rolling tailor rolled blank vertical velocity numerical simulation

Cancer Is A Survival Process under Persistent Microenvironmental and Cellular Stresses

在线全文

学校读者我要写书评

暂无评论

Genomics, Proteomics & Bioinformatics 2023年第6期21卷 1260-1265页

作者： Renbo tan Yi Zhou Zheng An ying Xu Cancer Systems Biology Center China-Japan Union Hospital of Jilin UniversityChangchun 130000China College of Computer Science and Technology Jilin UniversityChangchun 130000China Department of Biochemistry and Molecular Biology and Institute of BioinformaticsUniversity of GeorgiaAthensGA 30602USA

What defines cancer?Numerous factors have been found to be associated with cancer onset and *** Virchow suggested some 150 years ago that cancer was causally linked to persistent *** studies have revealed that overexposure to radiation,persistent microbial infection,genetic mutations,and chronic(sterile)inflammation could all potentially lead to cancer,and the same has been observed about intermittent hypoxia,iron overload,and intake of certain “carcinogens”.In parallel,considerable information has been collected regarding animals that never or rarely develop cancer,such as blind mole rats and *** no general frameworks have been published that can functionally link potential drivers to the formation and progression of cancer in a predictable manner,which is consistent with the aforementioned and other epidemiological ***,we outline one such framework.

关键词： Survival Virchow intake

Implications of the cosmic infrared background excess for the cosmic star formation

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

Science China(Physics,Mechanics & Astronomy) 2013年第5期56卷 1029-1034页

作者： tan WeiWei yu yunWei Institute of Astrophysics Central China Normal University

By phenomenologically describing the high-redshift star formation history, i.e., ,ρ.（z） oc [（1 ＋z）/4.5]-% and semi-analytically calculating the fractions of high-redshift Pop I/II and Pop II! stars, we investigate the contributions from both high-redshfit Pop I/II and Pop II/stars to the observed near-infrared （3 μm 〈// 〈 5 μm） excess in the cosmic infrared background emission. In order to account for the observational level of the near-infrared excess, the power-law index or of the assumed star formation history is constrained to within the range of 0 ≤a≤1. Such a constraint is obtained under the condition that the viral temperature of dark matter halos belongs to the range of 500 K ≤ Tvir≤ 104 K.

关键词： infrared background star formation dark matter

Acute and chronic excitotoxicity in ischemic stroke and late-onset Alzheimer's disease

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第7期20卷 1981-1988页

作者： Shan Ping yu Emily Choi Michael QJiang Ling Wei Department of Anesthesiology Emory University School of MedicineAtlantaGAUSA Center for Visual and Neurocognitive Rehabilitation Atlanta Veterans Affairs Medical CenterDecaturGAUSA

Stroke and Alzheimer's disease are common neurological disorders and often occur in the same *** comorbidity of the two neurological disorders represents a grave health threat to older *** review presents a brief background of the development of novel concepts and their clinical *** activity of glutamatergic N-methyl-D-aspartate receptors and N-methyl-D-aspartate receptor-mediated Ca^(2+)influx is critical for neuronal *** ischemic insult induces prompt and excessive glutamate release and drastic increases of intracellular Ca^(2+)mainly via N-methyl-D-aspartate receptors,particularly of those at the extrasynaptic *** Ca^(2+)-evoked neuronal cell death in the ischemic core is dominated by necrosis within a few hours and days known as acute ***,mild but sustained Ca^(2+)increases under neurodegenerative conditions such as in the distant penumbra of the ischemic brain and early stages of Alzheimer's disease are not immediately toxic,but gradually set off deteriorating Ca^(2+)-dependent signals and neuronal cell loss mostly because of activation of programmed cell death *** on the Ca^(2+)hypothesis of Alzheimer's disease and recent advances,this Ca^(2+)-activated“silent”degenerative excitotoxicity evolves from years to decades and is recognized as a unique slow and chronic *** N-methyl-D-aspartate receptor subunit GluN3A,primarily at the extrasynaptic site,serves as a gatekeeper for the N-methyl-D-aspartate receptor activity and is neuroprotective against both acute and chronic *** stroke and Alzheimer's disease,therefore,share an N-methyl-D-aspartate receptor-and Ca^(2+)-mediated mechanism,although with much different time *** is thus proposed that early interventions to control Ca^(2+)homeostasis at the preclinical stage are pivotal for individuals who are susceptible to sporadic late-onset Alzheimer's disease and Alzheimer's disease-related

关键词： Ca^(2+)hypothesis cognitive deficits hyperactivity late-onset Alzheimer's disease neurodegeneration N-methyl-D-aspartate receptors N-methyl-D-aspartate receptor subunits pathogenesis preventive treatment

Influence of laser parameters on the microstructures and surface properties in laser surface modification of biomedical magnesium alloys

在线全文

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2024年第1期12卷 72-97页

作者： Chee ying tan Cuie Wen Hua Qian Ang School of Engineering RMIT UniversityMelbourneVictoria 3001Australia

Biodegradable implants from magnesium(Mg)alloys have emerged in the biomedical field especially in the orthopedic and cardiovascular stent applications owing to their low density,high specific strength,excellent machinability,good biocompatibility,and *** primary shortcoming of Mg-based implants is their low corrosion resistance in the physiological environment,which results in premature mechanical integrity loss before adequate healing and the production of excessive hydrogen gas,which is harmful to the body tissues and negatively affects the biocompatibility of the *** surface modification has recently received attention because it can improve the surface properties such as surface chemistry,roughness,topography,corrosion resistance,wear resistance,hydrophilicity,and thus cell response to the surface of the *** composition and microstructures including textures and phases of laser-treated surfaces depend largely on the laser processing parameters(input laser power,laser scan velocity,frequency,pulse duration,pressure,gas circulation,working time,spot size,beam focal position,and laser track overlap)and the thermophysical properties of the substrate(solubility,melting point,and boiling point).This review investigates the impacts of various laser surface modification techniques including laser surface melting,laser surface alloying,laser cladding,laser surface texturing,and laser shock peening,and highlights their significance in improving the surface properties of biodegradable Mg alloys for implant ***,we explore how different laser process parameters affect its composition,microstructure,and surface properties in each laser surface modification technique.

关键词： Biocompatibility Biodegradability Corrosion Implant applications Laser surface modification Magnesium alloys