摘要:

AbstractIn the field of Scanning Force Microscopy several dynamical contact and noncontact modes have been introduced increasing the range of detectable surface and interface properties, and allowing to detect material properties such as elasticity and mass density on the nanometer scale. A detailed understanding of tip/surface interactions and the dynamic processes involved is required to understand the origin of a material contrast using these techniques. Here a general method to solve the equation of motion of a vibrating SFM cantilever/tip system in an external force field is presented. Contact modes as well as intermittent contact modes are discussed using a single set of equations describing the cantilever/tip motion, and by varying the size of amplitudes of the vibrating cantilever/tip system. To quantitatively describe the oscillation behavior of the SFM cantilever at large amplitudes the computer simulations are based on the MYD/BHW model providing a realistic contact model with respect to the contact area, the size of the contact forces as well as the transition from repulsive to attractive forces. The results are compared with the experiment and with different approaches based on analytical and numerical models.

ISSN:0003-3804    

DOI:10.1002/andp.19975090502

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractInvestigating a polycrystalline gold layer on glass by a scanning tunneling microscope in air, tunneling current oscillations were found, which are excited by the DC voltage across the gap. The oscillation amplitude is dependent on the place on the surface of the sample and correlates with its topography. The frequency spectra of these oscillations are influenced by resonances of the mechanical system (z‐piezo/sample holder/transducer/sample). A piezoelectric transducer is able to detect alternating forces originating from the tunnel junction. The resonances in the spectrum of the AC tunneling current and the mechanical resonances of the STM system seem to be related.Trapping and subsequent delayed desorption of charge carriers at localized surface states could play a role in generating the observed time‐dependent forces across the gap and thereby creating tunneling current oscillati

ISSN:0003-3804    

DOI:10.1002/andp.19975090503

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractIn the paper we propose a new method of constructing cryptosystems utilising a nonpredictability property of discrete chaotic systems. We formulate the requirements for such systems to assure their safety. We also give examples of practical realisation of chaotic cryptosystems, using a generalisation of the method presented in [7]. The proposed algorithm of encryption and decryption is based on multiple iteration of a certain dynamical chaotic system. We assume that some part of the initial condition is a plain message. As the secret key we assume the system parameter(s) and additionally another part of the initial condition.

ISSN:0003-3804    

DOI:10.1002/andp.19975090504

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractHuang and Yang replace a hard core of radiuscby their pseudopotential (HYPP), which can be used in perturbation theory. I show that HYPP and boundary value perturbation theory give the same energy shift, to first order inc. I model a two‐body potential as an oscillator potential (angular frequency ω) and a hard core. For an A‐body system, the ratio of the first order energy correction to the unperturbed energy is 0.448 A3/4c a, wherea= (Mω/2

ISSN:0003-3804    

DOI:10.1002/andp.19975090505

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractStarting from the Weisskopf theory decay rates for the evaporation of cluster atoms from hot liquid alkali metal clusters are derived. The crucial input quantity is the level density which is determined from empirical properties of the bulk, namely from the specific heat and the thermal expansion coefficient. The resulting rate expression is compared with decay rate formulas given by Engelking, Klots and Gspann. Furthermore, critical (appearance) sizes of multiply charged clusters are calculated by equating the rates for neutral monomer and light charged particle emission. Also shrinking and cooling rates of large hot clusters are determined by treating multiple emission of cluster atoms, thus establishing a time scale for the decay of clusters theoretically.

ISSN:0003-3804    

DOI:10.1002/andp.19975090506

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

ISSN:0003-3804    

DOI:10.1002/andp.19975090501

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY