Phase Representation and Property Determination of Raw Materials of Solid Lubricant

The composition, microstructure, mechanical and frictional properties of PTFE and its fillers were represented and analyzed by XRD, SEM, DSC, XPS and large-scale polarizing microscope. The results show that PTFE has a flocculent structure with high melt temperature and decomposition temperature, big contact angle and crystallinity, and low surface hardness, compression strength, friction coefficient, wearing capacity and surface energy. Cooling rate influenced the friction coefficient and wear resistance. Graphite and molybdenum disulfide have a flake structure, and molybdenum disulfide has a big contact angle and low surface energy. Copper powder has a globular structure and its chief component is Cu-Pb alloy, and there is a loose layer on the surface. Carbon fiber has a rod structure and there are C=O and C-O-C polar groups on the skeleton surface. The decreasing order of water absorption capacity is graphite, carbon fiber, molybdenum disulfide, PTFE and copper powder.

Determination of Elastic and Creep Properties of Thin-film Systems from indentation Experiments

Based on the detailed computer simulation of the indentation testing on the thin-film systems, the present paper explores the detailed procedure of determining elastic properties (elastic modulusE^(f) and Poisson ratio v(f)) and creep parameters (CCREEP^(f) and nCREEP^(f)) for a simple Norton law (ε=CCREEP^(f)σ^n CREE^(f), where e is creep strain rate, and a is the stress) material for a thin film coated on a creep substrate, whose elastic properties(E^(s) and v^(s)) and creep properties (CCREEP^(s) and nCREEP^(s)) of the substrate are known, from indentation elastic and creep testing,respectively. The influences of the thickness of the thin-film and the size of the indenter on the indentation behavior have been discussed. It is shown that the boundary between the thin film and the substrate has great influence on the indentation creep behavior. The relative sizes of indentation systems are chosen so that the behavior of the indentation on the film is influenced by the substrate. The two elastic parameters E^(f) and v^(f) of the film are coupled on the influence of the elastic behavior of indentation. With the two different size indenters, the two elastic parameters E^(f) and v^(f) of the film can be uniquely determined by the indentation experimental slopes of depth to applied net section stress results. The procedure of determining of the two Norton law parameters CCREEP^(f) and nCREEP^(f) includes the following steps by the steady indentation rate d. The first step to calculate the creep indentation rate on certain loads of the two different sizes of indenters on a set of assumed values of CCREEP^(f) and nCREEP^(f)Then to build relationship between the creep indentation rate and the assumed CCREEP^(f) and nCREEP^(f) With the experimental creep indentation rate to intersect two sets of which have the same values of d. The last step is to build the CCREEP^(f) and nCREEP^(f)curves from the intersection points for the two indenters. These two curves CCREEP^(f) and nCREEP^(f)

Electronic and Optical Properties of TiS2 Determined from Generalized Gradient Approximation Study

The electronic and optical properties of TiS2 are studied of density functional theory. A linearized and augmented by using an ab-initio calculation within the frame plane wave basis set with the generalized gradient approximation as proposed by Perdew et al. is used for the energy exchange-correlation determination. The results show a metallic character of TiS2, and the plots of total and partial densities of states of TiS2 show the metallic character of the bonds and a strong hybridization between the states d of Ti and p of S below the Fermi energy. The optical properties of the material such as real and imaginary parts of dielectric constant （ε（w） = ε1（w） ＋ iε2（w））, refractive index n（w）, optical reflectivity R（w）, for E / /x and E / /z are performed for the energy range of 0-.14 eV.

Origin of potential errors in the quantitative determination of terahertz optical properties in time-domain terahertz spectroscopy

We demonstrate theoretically and experimentally how changes of a terahertz （THz） beam induced by the sample affect the accuracy of the determination of THz dielectric properties in THz time-domain transmission spectros- copy （TDTS）. We apply a Gaussian beam and the ABCD matrix formalism to describe the propagation of the THz beam in a focused beam setup. The insertion of the sample induces a focus displacement which is absent in the reference t without a sample. We show how the focus displacement can be corrected. The THz optical properties after focus displacement correction reported in this Letter are in quantitative agreement with those obtained using collimated beam THz-TDTSinpreviouswork.

New Approach for Noninvasive Determination of Tissue Optical Properties

A state-of-the-art radiative transfer model for the coupled air/tissue system is introduced. We then present a feasibility study of a new method for determining the tissue optical properties.

On Banach Spaces Whose Unit Sphere Determines Polynomials

In this paper we study the problem of characterizing the real Banach spaces whose unit sphere determines polynomials, i.e., if two polynomials coincide in the unit sphere, is this sufficient to guarantee that they are identical？ We show that, in the frame of spaces with unconditional basis, non- reflexivity is a sufficient, although not necessary, condition for the above question to have an affirmative answer. We prove that the only lp^n spaces having this property are those with p irrational, while the only lp spaces which do not enjoy it are those with p an even integer. We also introduce a class of polynomial determining sets in any real Banach space.