Vibro-Acoustics Vol.I and Ⅱ

<正>These two volumes can really be recommended to anyone interested in vibro-acoustics or the field of sound and vibration.The two volumes include 16 chapters and some 890 pages.The work is the result of cooperation between the Key Laboratory of Acoustics,The Chinese Academy of Sciences and The Royal Institute of Technology,KTH.The topic describes how structures are excited,energy flows from an excitation point to a sound radiating surface,and     

Large Deviations, Guerra’s and A.S.S. Schemes, and the Parisi Hypothesis

We investigate the problem of computing $$\lim_{N \to \infty}\frac{1}{aN}\log EZ_N^a$$ for any value of a, where Z _N is the partition function of the celebrated Sherrington-Kirkpatrick (SK) model, or of some of its natural generalizations. This is a natural “large deviation” problem. Its study helps to get a fresh look at some of the recent ideas introduced in the area, and raises a number of natural questions. We provide a complete solution for a ≥ 0.     

Comment on ‘Structure and diffusion of clusters on Ni surfaces by C.-L. Liu and J.B. Adams’

We calculate the dissociation energy of Ni clusters containing up to 13 atoms adsorbed on Ni(111), in order to elucidate its dependence on the cluster size. As opposed to what is claimed by Liu and Adams [Surf. Sci. 268 (1992) 73] the dissociation energy of Ni/Ni(111) does not display a marked peak for N =5, its value for this cluster size being indeed very close to what is found for N = 4 and N = 6.     

Comment on ‘Cr LVV Auger emission and photoreduction of hexavalent Cr oxides by A.G. Schrott,G.S. Frankel,A.J. Davenport,H.S. Isaacs,C.V. Jahnes and M.A. Russak’

A paper by Schrott et al. [Surf. Sci. 250 (1991) 139] on the Auger Cr LVV spectra of Al/Cr alloys is commented on.The area of major disagreement regards the hypothesis that Al-alloying suppresses the Cr LVV decay. It is pointed out that the surface chemical composition of the alloys should be considered in detail, and that instrumental factors and the presence of surface contamination would account for the negligible Cr LVV intensity.     

Speculative and Hedging Interaction Model in Oil and U.S. Dollar Markets—Phase Transition

We show that there is a phase transition in the bounded rational Carfì–Musolino model, and the possibility of a market crash. This model has two types of operators: a real economic subject (Air) and one or more investment banks (Bank). It also has two markets: oil spot market and US dollar futures. Bank agents react to Air and equilibrate much more quickly than Air. Thus Air is an acting external agent due to its longer-term investing, whereas the action of the banks equilibrates before Air makes its next transaction. This model constitutes a potential game, and agents crowd their preferences into one of the markets at a critical temperature when air makes no purchases of oil futures.     

Mössbauer and N.M.R. studies of ErFe2Hx

Hydrides of Intermetallic compounds have been the object of many studies because of their potential applications/1/. Recent papers were devoted to the problem of interstitial site occupation in connection with H-H exclusion rule (d_H–H > 2.1 A). The present work deals with ErFe₂H_X, which has been investigated both by⁵⁷Fe Mössbauer Effect and by¹⁶⁷Er N.M.R. Previous studies were limited to X 2, 3.5, 4.1. Here five values of x (1.45, 1.6, 1.84, 2.6, 3.3) are considered, in order to obtain information on hydrogen location, filling and diffusion as a function of x, and also on hydrogen contribution to the electric field gradient (E.F.G.) and crystalline field at the Rare Earth.     

Extrusions and intrusions in fatigued metals. Part 1. State of the art and history†

Current state and historical progress in experimental and theoretical studies of surface relief appertaining to persistent slip bands (PSBs) and leading to fatigue crack initiation in cyclically deformed metals is presented as a thorough critical overview. A comprehensive inventory of microscopic techniques used for this study is tabulated chronologically with emphasis to their applicability to polycrystals. The most relevant experimental characteristics concerning surface relief evolution, namely the form of extrusions and intrusions in single- and polycrystalline materials, are surveyed. Theoretical models and computational simulations of extrusion and intrusion formation and fatigue crack initiation are critically reviewed.     

‘Factors of ignorance’ and the rationalized M.K.S.A. system of units

An attempt is made, by means of an allusive (rather than a systematic) historical account of the development of the subject, to exhibit the essentially unique character of the rationalized M.K.S.A. system of units. The establishment of this system involved one arbitrary decision—the determination to retain unaltered the size of the previously accepted unit of current. Thereafter, any choice of derived units, other than the choice actually made, would have destroyed the basic symmetry of the formulation.     

Comment on ‘activated chemisorption of methane and tunneling: A second look’ by T.C. Lo and G. Ehrlich

We have previously reanalyzed the data of Lo and Ehrlich on the activated chemisorption of CH₄ and CD₄ on W(211) in terms of a tunneling model. In the Letter cited above, Lo and Ehrlich criticize the tunneling model due to an insensitivity of the model with respect to the mass of the heavier isotope. In this Comment we show why the mass insensitivity is a natural consequence of the smaller tunneling probability for the deuterium isotope, and not a breakdown in the model.