检索结果-南通市图书馆

Capacity Analysis of an MISO Free-Space Optical Communications Assisted by Concave ORIS

在线全文

学校读者我要写书评

暂无评论

Journal of Communications and Information Networks 2023年第3期8卷 295-302页

作者： Frank Nonso Igboamalu alain Richard Ndjiongue Khmaies Ouahada Faculty of Engineering and the Built Environment University of JohannesburgJohannesburg 2092South Africa Faculty of Engineering and Applied Science Memorial University of NewfoundlandNL A1B 3X5Canada

This paper explores the ergodic channel capacity of multiple-input single-output(MISO)free-space optical(FSO)communication systems,assisted by(optical)re-configurable intelligent surfaces[(O)RIS],made of concave *** the one hand,RIS technology mitigates dead zones in communication ***,it increases the data rate and communication range,enhances the communication channel by making it intelligent,and improves the system’s ***,the RIS technology improves the spectrum and energy efficiencies of the considered *** the other hand,transmitting diversity mitigates deep fade and helps to achieve beamforming to regulate the beam sent in a specific ***,multiple light sources help to send different versions of the same information at other time ***,compared to flat reflectors,concave mirrors provide economic advantages enabled by their natural shape,which helps converge the impinging light beams into the same focal *** this paper,we harness the full potential of ORIS and MISO technologies in an FSO system by exploiting the hollow of concave reflectors to focus the reflected beams on a single *** derive an approximated closed-form expression,provide results of the proposed ORIS-aided FSO systems’ergodic channel capacity,and discuss the suitable type of concave *** results show that all types of concave mirrors provide similar results except when the thickness of the reflector is large enough to impact the reflected light.

关键词： ORIS concave reflectors MISO FSO communication systems ergodic channel capacity

(E) Enol ethers from the stereoselective reduction of α-alkoxy-β-ketophosphonates and Wittig type reaction

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 Chemistry 2010年第9期53卷 1937-1945页

作者： DAYOUB Wissam DOUTHEAU alain Laboratoire de Catalyse et Synthèse Organique Institut de Chimie et Biochimie Moléculaires et Supramoléculaires(ICBMS)CNRSUMR5246Université Lyon 1 Institut National des Sciences Appliquées de Lyon Laboratoire de Chimie Organique et BioorganiqueICBMS UMR 5246 CNRS Université Lyon 1 INSA Lyon

When α-alkoxy-β-ketophosphonates,prepared by the Rh(Ⅱ) mediated insertion reaction of α-diazo-β-ketophosphonates into the OH bond of primary alcohols,were reduced either by NaBH4 in the presence of CaCl2 or by DIBAL,they respectively gave the corresponding anti or syn stereomeric hydroxyphosphonates with pronounced to complete *** to the action of potassium tert-butoxyde,syn isomers led to the corresponding pure(E) enol ethers in moderate to good *** the same conditions anti isomers led to a mixture of(Z) and(E) enol ethers in rather poor *** sequence was applied to the preparation of some allyl-vinyl ethers with a(E) configuration for the vinylic double bond.

关键词： α-alkoxy-β-ketophosphonates reduction insertion rhodiocarbenoids Wittig-Wadsworth-Emmons enol ethers

Urological Emergencies at the University Hospital of Brazzaville: Epidemiological, Clinical, and Therapeutic Aspects

在线全文

学校读者我要写书评

暂无评论

Open Journal of Urology 2024年第5期14卷 333-345页

作者： Roland Bertile Banga-Mouss Yannick Dimi Nyanga Irène Ondima Armel Melvin Atipo Ondongo Steve Aristide Ondziel-Opara Joseph Junior Damba Nick Arnaud Monabeka Christ Ondzé Daniella Gloire Ngassiele Gidmard Onguele Henock Songa Jetsvy Mayala Anani Wensels Severin Odzebe Prosper alain Bouya Departement of Urology and Andrology University Hospital of Brazzaville Brazzaville Republic of the Congo

Introduction: Urological emergencies play a significant role in the medical and surgical activity of a urology department. The objective of this study was to determine the hospital prevalence of urological emergencies at the University Hospital of Brazzaville (CHUB), identify the different pathologies requiring urgent care, and list the various therapeutic methods. Patients and methods: A retrospective study of patients admitted to the medical and surgical emergencies department of CHUB over a 5-year period. Patient records admitted and treated for a urological emergency were included. The variables studied were the frequency of urological emergencies, patient age at admission, gender, nature of the emergency, and various therapeutic options. Results: Urological emergencies accounted for 4.3% of all medical and surgical emergencies. The mean age was 57 ± 28 years with a range of 3 to 93 years. The male-to-female ratio was 7.1. The most common conditions were urinary retention (54.67%), hematuria (17.20%), and renal colic (8.13%). Therapeutically, surgical urinary drainage was dominated by cystostomy. Conclusion: Urological emergencies are infrequent at the University Hospital of Brazzaville. Their management is often delayed.

关键词： Urological Emergencies Urinary Retention Hematuria Renal Colic

The equilibrium stability for a smooth and discontinuous oscillator with dry friction

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2016年第2期32卷 309-319页

作者： Zhi-Xin Li Qing-Jie Cao alain Léger School of Astronautics Centre for Nonlinear Dynamics Research Harbin Institute of Technology Harbin 150001 China Laboratoire de Mecanique et d' Acoustique CNRS 31 Chemin Joseph Aiguier 13402 Marseille Cedex 20 France

In this paper,we investigate the equilibrium stability of a Filippov-type system having multiple stick regions based upon a smooth and discontinuous（SD） oscillator with dry *** sets of equilibrium states of the system are analyzed together with Coulomb friction conditions in both（ f_n,f_s） and（x,˙x） *** the stability analysis,Lyapunov functions are constructed to derive the instability for the equilibrium set of the hyperbolic type and La Salle＇s invariance principle is employed to obtain the stability of the nonhyperbolic *** demonstrates the existence of a thick stable manifold and the interior stability of the hyperbolic equilibrium set due to the attractive sliding mode of the Filippov property,and also shows that the unstable manifolds of the hyperbolic-type are that of the endpoints with their saddle *** calculations show a good agreement with the theoretical analysis and an excellent efficien y of the approach for equilibrium states in this particular Filippov ***,the equilibrium bifurcations are presented to demonstrate the transition between the smooth and the discontinuous regimes.

关键词： SD oscillator Equilibrium set Dry friction Coulomb’s cone

Topology-enhanced mechanical stability of swelling nanoporous electrodes

在线全文

学校读者我要写书评

暂无评论

npj Computational Materials 2023年第1期9卷 1161-1175页

作者： Benjamin E.Grossman-Ponemon Ataollah Mesgarnejad alain Karma Center for Interdisciplinary Research on Complex Systems Department of PhysicsNortheastern UniversityBostonMA 02115USA School of Engineering Brown UniversityProvidenceRI 02912USA

Materials like silicon and germanium offer a 10-fold improvement in charge capacity over conventional graphite anodes in lithium-ion batteries but experience a roughly threefold volume increase during lithiation,which challenges ensuring battery *** silicon,created by liquid-metal-dealloying,is a potentially attractive anode design to mitigate this challenge,exhibiting both higher capacity and extended cycle ***,how nanoporous structures accommodate the large volume change is ***,we address this question by using phase-field modeling to produce nanoporous particles and to investigate their elastoplastic swelling behavior and *** simulations show that enhanced mechanical stability results from the network topology consisting of ligaments connected by bulbous,sphere-like *** ligaments forcefully resist elongation while the nodes,behaving like isolated spherical particles,experience large stresses driving ***,being smaller compared to a sphere of the same volume as the entire nanoporous particle,the nodes are more protected against fracture.

关键词： swelling stability attractive

Towards high-efficiency of hydrogen purification in metal hydride

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2023年第3期33卷 301-308页

作者： Koua alain Jesus Koua Jiahe Peng Arramel Arramel Neng Li State Key Laboratory of Silicate Materials for Architectures School of Materials Science and Engineering Wuhan University of Technology Shenzhen Research Institute of Wuhan University of Technology Nano Center Indonesia Jalen Raya PUSPIPTEK South Tangerang School of Chemistry and Environmental Engineering School of Environmental Ecology and Biological Engineering Novel Catalytic Materials of Hubei Engineering Research Center Wuhan Institute of Technology

Recent advancement on hydrogen(H2) retrieval in a mixture gas of H2/CO2based on the metal hydride(MH)technique has attracted numerous interests. In this work, we implement the lumped element model simulation to conduct a theoretical approach on the hydrogen purification process. The influence of orifice geometry and temperature of the tank, and inflow gas rate(fin) is investigated. The results show that the discharge coefficient(DC) is affected by the tank’s orifice geometry. The orifice shape is increasing the value of DC, as a result, the CO2(impurity) outflow rate heightens during the venting process and thereby promoting to obtain a high hydrogen purity. By overcoming the exothermic/endothermic effect in the absorption/desorption step and a proper finselection, we find an improvement in the hydrogen storage capacity(wt%) into MH and consequently the hydrogen recovery rate increases. A sharp improvement in orifice geometry and thermal conditions of the tank,and finenhances the main targeted results(hydrogen purity and recovery rate) and ensures the proper operation of the MH technique.

关键词： Hydrogen purification Metal hydride Discharge coefficient Lumped model simulation Carbon dioxide

Evaluating organic acids as alternative leaching reagents for rare earth elements recovery from NdFeB magnets

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Rare Earths 2023年第4期41卷 621-631页

作者： Sahar Belfqueh alain Seron Simon Chapron Guilhem Arrachart Nourredine Menad BRGM Direction de l'Eaude l'Environnementdes Procédés et AnalysesOrleansFrance ICSM Univ.MontpellierCEACNRSENSCMMarcouleFrance

This study proposes an advanced leaching method using organic acids to recover rare earth elements(REEs)from NdFeB permanent magnets from end-of-life computers hard disk drives(HDDs).The end-oflife HDDs were first dismantled in order to recover NdFeB magnets,which were then thermally demagnetized at 350℃during 30 min before crushing in a ball mill under inert *** electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS)analyses performed on the NdFeB magnets show the heterogeneous structure containing the major matric phase Nd_(2)Fe_(14)B and the REEsrich phase containing Nd and Pr ***,X-ray diffraction(XRD)and Mossbauer spectroscopy(MS)analyses on the ground NdFeB magnet show that grinding NdFeB magnets under inert atmosphere helps to minimize its *** analysis shows that the composition of the ground sample is Nd:22.8 wt%,Pr:3.3 wt%,Dy:1.2 wt%,Fe:62.6 wt%,Co:1.5 wt%,B:0.9 wt%,Ni:0.6 wt%.Diagrams of speciation and equilibrium phases(E_(h) ***)were calculated to determine the predominance of the formed species in the REEs-organic acids *** influence of the organic acid type(acetic acid,formic acid,citric acid and tartaric acid),the acid concentration(10 vol%,up to saturation),and the solid/liquid(S/L)ratio(0.5%-10%)on NdFeB magnets leaching was investigated employing an optimal experimental design conceived by the statistical software *** acid(CH_(3)COOH)shows the highest leaching performance of REEs,allowing leaching yields over 90%for Nd,Dy and Pr in the acid concentration range of 1.6-10 mol/L and the S/L ratio range of 0.5%-5%at a temperature of 60℃.The results presented in this investigation suggest that REEs can be recovered from magnets of end-of-life HDDs using an eco-friendly method assisted by organic acids.

关键词： NdFeB magnets Rare earth elements Leaching Organic acids Acetic acid

Lead-free textured piezoceramics using tape casting:A review

在线全文

学校读者我要写书评

暂无评论

Journal of Materiomics 2018年第4期4卷 277-303页

作者： alain D.Moriana Shujun Zhang ISEM Australian Institute of Innovative MaterialsUniversity of WollongongWollongongNSW2500Australia Defence Materials Technology Centre 24 Wakefield StreetHawthornVIC3122Australia

In this review,the evolution of textured lead-free piezoceramics has been explored,primarily focusing on the technique of templated grain growth(TGG)and reactive-templated grain growth(RTGG),as an alternative to single *** mechanics and properties of using template in guiding and orienting the ceramic grains into the same crystal orientation allow for piezoelectric properties approaching those of their single-crystal *** fabrication process was surveyed in depth,with focus placed on the tape casting process and numerous variables associated with aligning the template seeds in the ceramic *** piezoelectric and ferroelectric properties of the textured ceramics are supposed to be a function of all parameters(tape casting,slurry formation,sintering profile,template properties)in an effort to determine the significance of their contributions to the properties.

关键词： Piezoelectric Textured Tape casting Template Lead-free

On the size of the intersection of two Lucas sequences of distinct type Ⅱ

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 Mathematics 2011年第7期54卷 1299-1316页

作者： CIPU Mihai MIGNOTTE Maurice TOGB alain Institute of Mathematics of the Romanian Academy Bucharest RO-014700 Romania U. F. R. de Mathmatiques Universit de Strasbourg Strasbourg 67084 France Department of Mathematics Purdue University North Central Westville IN 46391 USA

Let a and b be positive integers, with a not perfect square and b > 1. Recently, He, Togband Walsh proved that the Diophantine equation x2-a((bk-1)/(b-1))2=1 has at most three solutions in positive integers. Moreover, they showed that if max{a,b} > 4.76·1051, then there are at most two positive integer solutions (x,k). In this paper, we sharpen their result by proving that this equation always has at most two solutions.

关键词： Diophantine equation exponential equation linear forms in logarithms