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81.
This paper develops a generalization of the linear quadratic control problem with partial information. As in the standard partial information setting, it is assumed that the state variable is only observed with noise. The idea in this paper is that the information level may be chosen optimally. In real life information is costly to acquire. It is therefore a trade off between the costs of getting detailed information and the increased value this information gives. We believe that the technique we present should have potential for application within both economics and engineering. 相似文献
82.
M.J. Cordill M.S. Lund J. Parker C. Leighton A.K. Nair D. Farkas N.R. Moody W.W. Gerberich 《International Journal of Plasticity》2009
Because of its ease of implementation and insensitivity to indenter drift, dynamic indentation techniques have been frequently used to measure mechanical properties of bulk and thin film materials as a function of indenter displacement. However, the actual effect of the oscillating tip on the material response has not been examined. Recently, it has been shown that the oscillation used with dynamic indentation techniques alters the measured hardness value of ductile metallic materials, especially at depths less than 200 nm. The alteration in the hardness is due to the added energy associated with the oscillation which assists dislocation nucleation. Atomistic simulations on nickel thin films agree with experiments that more dislocations are nucleated during dynamic indents than with quasi-static indents. Through the analysis of quasi-static and dynamic indents made into nickel single crystals and thin films, a theory to describe this phenomenon is presented. This is coined the Nano-Jackhammer effect, a combination of dislocation nucleation and strain rate sensitivity caused by indentation with a superimposed dynamic oscillation. 相似文献
83.
Esben Lindgaard Erik Lund Kim Rasmussen 《International Journal of Solids and Structures》2010,47(22-23):3186-3202
Nonlinear buckling optimization is introduced as a method for doing laminate optimization on generalized composite shell structures exhibiting nonlinear behaviour where the objective is to maximize the buckling load. The method is based on geometrically nonlinear analyses and uses gradient information of the nonlinear buckling load in combination with mathematical programming to solve the problem. Thin-walled optimal laminated structures may have risk of a relatively high sensitivity to geometric imperfections. This is investigated by the concepts of “worst” imperfections and an optimization method to determine the “worst” shape imperfections is presented where the objective is to minimize the buckling load subject to imperfection amplitude constraints. The ability of the nonlinear buckling optimization formulation to solve the laminate problem and determine the “worst” shape imperfections is illustrated by several numerical examples of composite laminated structures and the application of both formulations gives useful insight into the interaction between laminate design and geometric imperfections. 相似文献
84.
R.H. Kraus W. Loveland K. Aleklett P.L. McGaughey T.T. Sugihara G.T. Seaborg T. Lund Y. Morita E. Hagebø I.R. Haldorsen 《Nuclear Physics A》1985,432(2):525-554
Target-fragment angular distributions were measured using radiochemical techniques for 69 different fragments (44 ? A ? 196) from the interaction of 86 MeV/A12C with 197Au. The angular distributions in the laboratory system are forward-peaked with some distributions also showing a backward peaking. The shapes of the laboratory system distributions were compared with the predictions of the nuclear firestreak model. The measured angular distributions differed markedly from the predictions of the firestreak model in most cases. This discrepancy could be due, in part, to overestimation of the transferred longitudinal momentum by the firestreak model, the assumption of isotropic angular distributions for fission and particle emission in the moving frame and incorrect assumptions about how the lightest (A < 60) fragments are produced. No evidence was found for any significant number of target fragments moving sidewise to the beam direction in apparent contradiction to the expectation of hydrodynamical-model calculations. The laboratory-frame angular distributions were transformed into the moving frame using various assumptions about the moving frame velocity. The resulting light-fragment distributions showed an asymmetry in the moving frame indicative of their production in a fast process without the establishment of statistical equilibrium. No evidence was found for any production of the light fragments by a very asymmetric fission mechanism. The fission-fragment distributions were compared to standard formulas and an average fissioning-system angular momentum of was deduced. It was not possible to find a moving frame in which the heavy (A > 145) fragment distributions were symmetric about 90°. 相似文献
85.
W. Bell K. Braune G. Glaesson D. Drijard M. A. Faessler H. G. Fischer H. Frehse S. Garpman W. Geist C. Gruhn P. Hanke M. Heiden W. Herr P. G. Innocenti T. J. Ketel E. E. Kluge I. Lund G. Mornacchi T. Nakada I. Otterlund B. Povh A. Putzer B. Rensch E. Stenlund T. J. M. Symons M. Szczekowski R. Szwed O. Ullaland M. Wunsch 《Zeitschrift fur Physik C Particles and Fields》1985,27(2):191-203
Momenta of charged particles produced in inelastic αα, αp, andpp collisions were measured using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. Inclusive and semi-in-clusive spectra are presented as a function of rapidityy, Feynman-x, and transverse momentump T . The inclusivey distributions agree well with predictions of the dual parton model; the highest particle densities are reached aty?0 and the momenta of leading protons decrease significantly for increasing total multiplicity. ‘Temperatures’ are equal in αα, αp, andpp interactions. Thep T distributions depend weakly on the multiplicity. 相似文献
86.
W. Bell A. Breakstone G. Claesson H. B. Crawley G. M. Dallavalle K. Doroba D. Drijard F. Fabbri A. Firestone M. A. Faessler H. G. Fischer S. Y. Fung S. Garpman W. Geist G. Giacomelli R. Gokieli M. Gorbics C. R. Gruhn P. Hanke M. Heiden W. Herr T. J. Ketel E. E. Kluge J. W. Lamsa T. Lohse I. Lund R. Mankel W. T. Meyer G. Mornacchi T. Nakada I. Otterlund M. Panter H. Pugh A. Putzer K. Rauschnabel B. Rensch F. Rimondi M. Schmelling L. Schroeder R. Sosnowski E. Stenlund T. J. M. Symons M. Szczekowski R. Szwed O. Ullaland R. Walczak D. Wegener M. Wunsch 《Zeitschrift für Physik A Hadrons and Nuclei》1986,325(1):7-14
Inelasticαα anddd collisions were studied at a centre-of-mass energy √S NN=31.2 GeV per nucleon-nucleon collision, using the Split-Field Magnet (SFM) detector at the CERN ISR. In this paper we show the inclusive and semi-inclusive rapidity distributions of protons, compare them with predictions of the Lund model, and calculate the average rapidity loss for participant protons. From the negative particles we calculate the inelasticity of the interaction, the average energy per particle, and the degree of isotropy of the produced hadrons. 相似文献
87.
88.
This article describes a dynamic model for formation and stability of CO2-hydrate on the interface of liquid CO2(LCO2) and ocean water at large depths. Experimental results indicate that a thin film of hydrate naturally forms on the interfaces between LCO2 and water, and inhibits diffusion between the two phases. Experiments further shows that the flux of CO2 through the hydrate film is dependent of the CO2-concentration in the ambient sea water. The model proposed here explains these phenomena by introducing four major mechanisms; diffusion of water to the LCO2-phase, formation of hydrate in the LCO2-hydrate interface, decay of hydrate in the water-hydrate interface, and diffusion of CO2 through the water phase. The model explains the CO2 flux not by diffusion through the hydrate film, but suggest a mechanism of continuous hydrate formation and decay. The overall effect is a “moving,” pseudo-steady-state hydrate film due to transport of CO2 through the film. The film velocity is dependent of liquid-liquid diffusivity parameters and reaction constant, and lacking experimental values of these parameters, an order–of-magnitude analysis is done by fitting the model to experimentally obtained data for the overall film velocity. The motivation for this work is to elucidate options for CO2 depositions in deep oceans, of which liquid CO2 sequestration is believed to be one of the most feasible. Spreading of CO2 from a liquid CO2-lake and associated lowering of pH in the ecosystem surrounding the lake is of large concern. The work presented here concludes that diffusion of CO2 in the ocean is largely reduced by the hydrate film and suggests that hydrate formation may alleviate some of the environmental concerns regarding deep ocean sequestration of liquid CO2. © 1994 John Wiley & Sons, Inc. 相似文献
89.
R. Bock K. G. R. Doss H. H. Gutbrod K. -H. Kampert B. Kolb I. Lund H. R. Schmidt T. Siemiarczuk W. Wiślicki 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(3):293-299
We report transverse,R
T
, and longitudinal,R
L
, source sizes extracted from two-pion interferometry analysis in the Au+Au and Nb + Nb interactions at 650 A MeV. For the Nb+Nb interactions, both,R
T
andR
L
, do not exceed the niobium nucleus radius. In the case of Au+Au collisions, the transverse size is larger than the longitudinal one being about 12 fm for the selection ofP
+ < 120=" mev/c.=" we=" also=" corroborate=" the=" existence=" of=" the=" previously=" reported=" specific=" three-pion=">One of us (T.S.) wishes to thank Professor M.I. Podgoretsky and Professor R.M. Weiner for interesting discussions and comments. We also wish to acknowledge remarks of Dr. B. Lörstad. 相似文献
90.
Albrecht R Antonenko V Awes TC Barlag C Berger F Bloomer M Blume C Bock D Bock R Bohne E Bucher D Claesson G Claussen A Clewing G Debbe R Dragon L Dubovik Y Eklund A Fokin S Franz A Garpman S Glasow R Gustafsson HÅ Gutbrod HH Hansen O Hölker G Idh J Ippolitov M Jacobs P Kampert KH Karadjev K Kolb BW Lebedev A Löhner H Lund I Manko V Moskowitz B Nikolaev S Nystrand J Obenshain FE Oskarsson A Otterlund I Peitzmann T Plasil F Poskanzer AM Purschke M Ritter H Roters B Saini S Santo R Schlagheck H 《Physical review letters》1996,76(19):3506-3509