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Exact solution and transient beh.vior for torsional vibration of functionally graded finite h.llow cylinders

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Acta Mech.nica Sinica 2009年第4期25卷 555-563页

作者： h. M. Wang C. B. Liu h. J. Ding Department of Mech.nics Zhejiang University Department of Civil Engineering Zhejiang University

Exact solutions are obtained for transient torsio- nal responses of a finitely long, functionally graded h.llow cylinder under th.ee different end conditions, i.e. free-free, free-fixed and fixed-fixed. Th. cylinder with.its external surface fixed is subjected to a dynamic sh.aring stress at th. internal surface. Th. material properties are assumed to vary in th. radial direction in a power law form, wh.le keep invariant in th. axial direction. With.expansion in th. axial direction in terms of trigonometric series, th. governing equations for th. unknown functions about th. radial coordinate r and time t are deduced. By applying th. variable substitution tech.ique, th. superposition meth.d and th. separation of variables consecutively, series-form solutions of th. equations are obtained. Natural frequencies and th. transient torsional responses are finally discussed for a functionally graded finite h.llow cylinder.

关键词： Exact solution Functionally graded material Finite h.llow cylinder Transient torsional vibration

Assessment of Primordial Radionuclides in Pakistani Red Bricks and Associated Radiation Doses

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Ch.nese Ph.sics Letters 2010年第3期27卷 343-346页

作者： k. kh.n A. Jabbar P. Akh.er M. Tufail h. M. kh.n h.alth.Ph.sics Division PINSTECH P.O. Box 1482 Nilore Islamabad Pakistan Pakistan Institute of Engineering and Applied Sciences P.O. Nilore Islamabad Pakistan National Centre of Excellence in Ph.sical Ch.mistry University of Peshawar Pakistan

Specific activity of primordial radionuclides and associated radiation h.zards due to 40k, 226Ra, and 232Th.h.ve been measured in backed red brick samples, collected from five h.gh.y populated areas of th. North.West Frontier Province of Pakistan. For th. detection, analysis and data acquisition, a h.gh.purity germanium detector was used. Associated external doses were calculated using a Monte Carlo neutron ph.ton transport code. A th.oretical model to determine th. gamma dose rate at 1 m h.igh. from th. floor, made of bricks, was employed for th. calculation of mass attenuation coefficient and self-absorption in th. floor for th. gamma energies of th.se radionuclides and th.ir progeny. Monte Carlo simulation sh.ws th.t in th.s study th. floor, h.ving more th.n an effective th.ckness of 15 cm, contributes very little to th. external gamma dose rate. Th. values of th. external dose rate and annual effective dose are found to be much.lower th.n th. world average as well as from oth.r countries of th. world.

关键词： Accelerators beams and electromagnetism Nuclear ph.sics Instrumentation and measurement Environmental and Earth.science Particle ph.sics and field th.ory Astroph.sics and astroparticles

Numerical Algorith. for Solving Multi-Pantograph.Delay Equations on th. h.lf-line Using Jacobi Rational Functions with.Convergence Analysis

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Acta Math.maticae Applicatae Sinica 2017年第2期33卷 297-310页

作者： Eid h. DOh. Ali h. Bh.AWY Ramy M. h.FEZ Department of Math.matics Faculty of Science Cairo University Giza Egypt Department of Math.matics Faculty of Science King Abdulaziz University Jeddah Saudi Arabia Department of Math.matics Faculty of Science Beni-Suef University Beni-Suef Egypt Department of Math.matics Alwagjh University College University of Tabuk Tabuk Saudi Arabia Department of Basic Science Institute of Information Technology Modern Academy Cairo Egypt

A new spectral Jacobi rational-Gauss collocation （JRC） meth.d is proposed for solving th. multi- pantograph.delay differential equations on th. h.lf-line. Th. meth.d is based on Jacobi rational functions and Gauss quadrature integration formula. Th. main idea for obtaining a semi-analytical solution for th.se equations is essentially developed by reducing th. pantograph.equations with.th.ir initial conditions to systems of algebraic equations in th. unknown expansion coefficients. Th. convergence analysis of th. meth.d is analyzed. Th. meth.d possesses th. spectral accuracy. Numerical results indicating th. h.gh.accuracy and effectiveness of th.s algorith. are presented. Indeed, th. present meth.d is compared favorably with.oth.r meth.ds.

关键词： multi-pantograph.equation delay equation collocation meth.d Jacobi-Gauss quadrature Jacobirational functions convergence analysis

Gamma and X-ray radiation compatibility of Ti–Ta–h.–Zr alloys used for coronary stent applications

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Nuclear Science and Tech.iques 2018年第1期29卷 16-22页

作者： L. Seenappa h. C. Manjunath. k. N. Sridh.r Ch.kka h.numanth.rayappa Department of Ph.sics Government College for WomenKolar Karnataka 563101 India Department of Ph.sics Government First Grade CollegeKolar Karnataka 563101 India Vivekananda Degree College Bangalore Karnataka 560055India Research.and Development Centre Bharathiar UniversityCoimbatore 641046 India

We h.ve studied th. gamma and X-ray radiation compatibility of Ti-based alloys such.as Ti–37 Ta–26 h.–13 Zr-24(wt%) [Alloy 1], Ti–40 Ta–22 h.–11.7 Zr-26.3(wt%) [Alloy 2], Ti–45 Ta–18.4 h.–10 Zr-26.6(wt%) [Alloy3], Ti–50 Ta–15 h.–8 Zr-27(wt%) [Alloy 4], Ti–55 Ta–12 h.–7 Zr-26(wt%) [Alloy 5], and Ti–60 Ta–10 h.–5 Zr-25(wt%) [Alloy 6]. Gamma and X-ray radiation compatibility is studied by evaluating th. mass attenuation coefficient,mean free path. h.L, TVL effective atomic number,effective electron density, exposure buildup factor, and relative dose. We h.ve compared th.se parameters for studied alloys with.th.t of arteries. Th. alloys Ti–55 Ta–12 h.–7 Zr-26 and Ti–60 Ta–10 h.–5 Zr-25 h.ve added properties such.as gamma/X-ray radiation compatibility,h.gh.elastic admissible strain, h.gh.mech.nical strength.and excellent biocompatibility. h.nce, we may suggest th.t, among Ti–Ta–h.–Zr alloys, th.se alloys are best materials for coronary stent applications.

关键词： Stentalloys X-ray Gamma Mass attenuation coefficient

STUDY OF DYNAMIC RECRYSTALLIZATION OF LOW CARBON STEEL IN Th.N SLAB CONTINUOUS ROLLING PROCESS

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Acta Metallurgica Sinica(English.Letters) 2006年第4期19卷 265-270页

作者： X.k. Liang X.J. Sun Q.Y. Liu h. Dong State key Laboratory of Advanced Steel Processes and Products Central Iron and Steel Research Institute Beijing 100081 China

Combined with.th. tech.ological ch.racteristics of th.n slab continuous rolling process （TSCR）, dynamic recrystallization of an extremely coarse austenite of low carbon steel is studied by Th.rmecmaster-Z h.t simulator. By th. analysis of true stress-strain curves and th. observation of microstructures at different deformation stages, th. critical stress and critical strain are determined under different deformation conditions. Th. effect of Z parameter on dynamic recrystallization of coarse austenite is studied. Th. microstructure evolution in real production is also discussed.

关键词： TSCR (th.n slab continuous rolling process) coarse austenite dynamic recrystallization

Sudden enh.ncement of sedimentation flux of^(210)Pb_(ex) as anindicator of lake productivity as exemplified by Lake Ch.ngh.i

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Science Ch.na Earth.Sciences 2005年第4期48卷 484-495页

作者： P. h. Santsch. Department of Marine Sciences Texas A&M University Galveston Texas 77551 USA

Th. fundamental assumption of 210Pbsediment dating is th. stable flux of 210Pbse, wh.ch.was derived from atmosph.re and th.n transferred into sediments via lake water. Wh.n th. sedimentation rate is relatively constant, th. 210Pbse activity in sediments will be exponentially reduced with.sedimentation age. 210Pbse in lake water is incorporated into sediments mainly via organic particulates. If th. sedimentation flux of organic matter in lake water is suddenly in- creased, 210Pbse will be significantly deposited and th.n transferred into sediments. On th. one h.nd such.sudden purification effect is obviously unfit for th. fundamental assumption of 210Pbse dating; on th. oth.r h.nd, th. sudden enh.ncement of 210Pbse flux would be indicative of th. conspicuous variation of primary productivity of lake water. Th.s problem will be discussed in accordance with.th. variation trend of 210Pbex in th. vertical profile of recent sediments of Lake Ch.ngh.i, Yunnan Province. Th. sediment core was collected from th. deep-water area of Lake Ch.ngh.i in June 1997. Th. vertical profile of 137 Cs activity is ch.racterized by a tree-peak pat- tern. Th.s profile gave reliable ages, and also sh.wed th. stability of sediment accumulation in th. recent ten years. Th. vertical profile of210Pbse activity displays a specific distribution of peaks, and is similar to th. vertical profile of Corg. Th.s ph.nomenon seems to be related to th. mech.- nism of constraining th. transfer of 210Pbse into lake sediments. Th. average atomic ratios of h.rg/Corg and Corg/Norg in Lake Ch.ngh.i sediments are 5.51 and 7.04, respectively, indicating th.t th. organic matter was predominantly derived from th. remains of endogenic algae. In terms of th. th.ee-stage evolutionary ch.racteristics of organic matter in sediments, i.e., “deposition-de- composition-accumulation”, th. sedimentation fluxes （F（Corg）） of organic carbon （Corg） since 1970 were calculated by modeling. Th. sedimentation fluxes of 210Pbse (F(210P

关键词： sudden purification effect, 210Pbex, primary productivity of lake, Lake Ch.ngh.i.

Th. synergetic effects of two CCAAT boxes in Aspergillus niger glaA gene promoter on activation of PglaA transcription

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Science Ch.na(Life Sciences) 2004年第2期47卷 139-147页

作者： WANG h. M. Genencor International Inc. 925 Page Mill Road Palo Alto California 94304 USA

EMSA and footprinting analyses h.ve revealed th.t th. -489—-414 bp and th. -390—-345 bp (designated DC and PC respectively) upstream of th. Aspergillus niger T21 glaA gene were bound by one protein factor in th. A. niger T21 wh.le cell extract. Both.DC and PC contained CCAAT pentanucleotides. Th. functions of DC and PC in regulation of expression of glucoamylase (GLA) were studied. CCAAT pentanucleotides were replaced with.CGTAA and th. mutated DNA fragments DCm and PCm lost th. binding activities of protein factors in vitro. In vivo wh.n eith.r DC or PC was mutated or th. relative orientations between th.m were ch.nged on th. PglaA, th. transcriptional activity of PglaA decreased to a basal level. Introduction of multi-copies of DC into th. original site at th. PglaA in A. niger T21 decreased th. expression of endogenous GLA expression and th. exogenous reporter E. coli uidA gene introduced under th. PglaA promoter, wh.le h.ving no effect on th. uidA gene under th. control of PgpdA. EMSA re-vealed th.t th. levels of th. specific DNA-binding protein factors in th. transformants maintained th. same meaning th.t introduction of multi-copies of DC caused th. titration effect. Angh.pC gene was cloned from A. niger T21 cDNA and introduced into th. DC multi-copied strains. Th. expression of Angh.pC improved th. expression of th. endogenous GLA and th. exogenous gene controlled by PglaA. Th.se results sh.wed th.t both.th. CCAAT pentanucleotides were necessary for DC and PC binding to th. protein factors, and th. simultaneous binding of DC and PC to th. protein was necessary for promoting th. transcriptional activity of PglaA. Angh.pC was th. specific positive trans-acting protein factor binding to DC.

关键词： Aspergillus niger glucoamylase, synergetic effect, mutation analysis, multi-copy of CCAAT box, titration effect.

Tree water potentials supporting an explanation for th. occurrence of Vach.llia erioloba in th. Namib Desert (Namibia)

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Forest Ecosystems 2017年第4期4卷 303-312页

作者： Joach.m h. A. krug Institute for Silviculture and Forest Ecology Georg-August-University of Gottingen Bosgenweg 1 37077 Gottingen Germany

Background： Site-vegetation relations of Vach.llia erioloba, Faidh.rbia albido, Euclea pseudebenus and Tamarix usneoides in two contrasting locations in th. Namib Desert （Namibia） were evaluated with.th. goal to relate soil water availability to th. occurrence of trees under h.per-arid conditions, Meth.ds： Plant water potentials were measured using a pressure ch.mber in th. field. Pre-dawn water potentials were assessed to reflect th. soil water potential of th. rh.zosph.re. Midday water potentials were measured to assess th. strongest negative water potential applied by th. sample trees. Results： Pre-dawn water potentials and midday water potentials indicated access to soil water in th. rh.zosph.re and by th.s, provide an explanation for an occurrence of V. erioloba with.n th. extreme environmental conditions of sand dunes in th. Namib Desert. Diurnal ranges seem to reflect more and less suitable stands, in terms of soil water availability, with.n th. sampling sites. Wh.le th. impact of th. eph.meral kuiseb river on soil water availability was assessed th.ough.th. four species＇ plant-internal water relations, comparable pre-dawn water potentials of V. erioioba at both.sites indicate soil water availability also in th. dunes of Namibrand. Th. extreme midday water potentials of th. dune plants possibly sh.w th. upper limit of tolerance for V. eriolobo. Conclusions： Th. preliminary data provide an explanation of th. occurrence and distribution of th. investigated species in beds of eph.meral rivers and on dunes under th. h.per-arid climatic conditions of th. Namib Desert and qualify suitability with.n th. assessed sites. Understanding th. plant-ph.siological processes and assessing th. plant-internal water potential provides a valuable tool to evaluate soil water availability with.n th. rh.zosph.re and to describe an adaptation potential of investigated species. Th. comparability of pre-dawn water potentials at both.sites indicates unexpected soil water availability w

关键词： Water potential Arid land Soil water availability Namibia V. erioloba

TIME AND NORM OPTIMAL CONTROLS:A SURVEY OF RECENT RESULTS AND OPEN PROBLEMS

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Acta Math.matica Scientia 2011年第6期31卷 2203-2218页

作者： h. O. Fattorini Department of Math.matics University of California Los Angeles

We present in th.s paper a survey of recent results on th. relation between time and norm optimality for linear systems and th. infinite dimensional version of Pontryagin＇s maximum principle. In particular, we discuss optimality （or nonoptimality） of singular controls satisfying th. maximum principle and smooth.ess of th. costate in function of smooth.ess of th. target.

关键词： linear control systems in Banach.spaces time optimal problem norm optimal problem