Thermal diffusion, marking

The reaction of the two systems to an ignition stimulus is markedly dissimilar the cohesive material presents a combustible surface wherein the rate of regression is controlled by thermal diffusivity into the propellant the non-cohesive system offers flame paths of convection into the explosive bulk, which if ignited produce gases to fracture the ma-... 

Satterfield (S2, S3) carried out a number of interesting macroscopic studies of simultaneous thermal and material transfer. This work was done in connection with the thermal decomposition of hydrogen peroxide and yielded results indicating that for the relatively low level of turbulence experienced the thermal transport did not markedly influence the material transport. However, the results obtained deviated by 10 to 20 from the commonly accepted macroscopic methods of correlating heat and material transfer data. The final expression proposed by Satterfield (S3), neglecting the thermal diffusion effect (S19) in the boundary layer, was written as... 

The simplest recording medium is a bilayer structure. It is constructed by first evaporating a highly reflective aluminum layer onto a suitable disk substrate. Next, a thin film (15-50 nm thick) of a metal, such as tellurium, is vacuum deposited on top of the aluminum layer. The laser power required to form the mark is dependent on the thermal characteristics of the metal film. Tellurium, for example, has a low thermal diffusivity and a melting point of 452 °C which make it an attractive recording material. The thermal diffusivity of the substrate material should also be as low as possible, since a significant fraction of the heat generated in the metal layer can be conducted to the substrate. For this reason, low cost polymer substrates such as poly (methylmethacrylate) or poly (vinyl chloride) are ideal. 

Wada and others (1966) indicated that the piezoelectricity of poly-oxymethylene (POM) markedly increases when a temperature gradient has been applied during the casting process, probably because of the thermal diffusion of ions in the film. 

Fig. 8 Diffusion (D) and thermal diffusion (Dj) coefficient of PDMS/PEMS (16.4/48.1) left) and Soret coefficient right) for different PDMS mass fractions given in the legends. Binodal points mark the intersection with the binodal. The dashed line segments are extrapolations into the two-phase regime. Figures from [100], Copyright (2007) by The American Physical Society...

Uncertainties of the conventional parameters of H-atoms have been addressed since the early applications of X-ray charge density method. Support from ND measurements appears to be essential, because the neutron scattering power is a nuclear property (it is independent of the electronic structure and the scattering angle). The accuracy of nuclear parameters obtained from ND data thus depends mainly on the extent to which dynamic effects (most markedly thermal diffuse scattering) and extinction are correctable. Problems associated with different experimental conditions and different systematic errors affecting the ND and XRD measurements have to be addressed whenever a joint interpretation of these data is attempted. This has become apparent in studies which aimed either to refine XRD and ND data simultaneously [59] (commonly referred to as the X+N method), or to impose ND-derived parameters directly into the fit of XRD data (X—N method) [16]. In order to avoid these problems, usually only the ND parameters of the H-atoms are used and fixed in the XRD refinement (X-(X+N) method). 

Nguyen, M. Beckett, R. Determination of thermal diffusion coefficients using thermal field-flow fractionation and Mark-Houwink constants. Anal. Chem. 2004, 76, 2382-2386. 

There was another enrichment plant that was built near K-25, the S-50 thermal diffusion planf, developed by fhe US Navy. If operated only 1 year, from September 1944 until September 1945, 1 month after the end of World War II. These events marked the beginning of uranium enrichmenf. 

The cooling rates of trans-stilbene have been measured in a number of molecular liquids as well as in ionic liquids tFig. 8.111 [8]. The results show a marked contrast between the molecular and ionic liquids, in molecular liquids, including alkanes (heptane, hexane, octane, nonane, decane), alcohols (methanol, ethanol, ethylene glycol) and others (chloroform, toluene), a clear linear relation is observed between the cooling rate k and the bulk thermal diffusivity k (right-hand box in Fig. 8.111. Thermal diffusivity k is defined in the diffusion equation of heat. Equation 8.1 ... 

Injection molding consists of squirting a molten polymer into a cold mold. en thick parts are molded from a crystalline polymer, e.g polypropylene, they sometimes exhibit sink marks, where the surface of the part has actually sunk away from the mold waE Explain why. Hint. Polymers have very low thermal diffusivities. 

IHP) (the Helmholtz condenser formula is used in connection with it), located at the surface of the layer of Stem adsorbed ions, and an outer Helmholtz plane (OHP), located on the plane of centers of the next layer of ions marking the beginning of the diffuse layer. These planes, marked IHP and OHP in Fig. V-3 are merely planes of average electrical property the actual local potentials, if they could be measured, must vary wildly between locations where there is an adsorbed ion and places where only water resides on the surface. For liquid surfaces, discussed in Section V-7C, the interface will not be smooth due to thermal waves (Section IV-3). Sweeney and co-workers applied gradient theory (see Chapter III) to model the electric double layer and interfacial tension of a hydrocarbon-aqueous electrolyte interface [27]. 

Thermal Printing. Thermal printing is a generic name for methods that mark paper or other media with text and pictures by imagewise heating of special-purpose consumable media. Common technologies are direct thermal thermal, ie, wax, transfer and dye-sublimation, ie, diffusion, transfer. Properties and preferred appHcations are diverse, but apparatus and processes are similar (87—89). 

Summary of experimental data Film boiling correlations have been quite successfully developed with ordinary liquids. Since the thermal properties of metal vapors are not markedly different from those of ordinary liquids, it can be expected that the accepted correlations are applicable to liquid metals with a possible change of proportionality constants. In addition, film boiling data for liquid metals generally show considerably higher heat transfer coefficients than is predicted by the available theoretical correlations for hc. Radiant heat contribution obviously contributes to some of the difference (Fig. 2.40). There is a third mode of heat transfer that does not exist with ordinary liquids, namely, heat transport by the combined process of chemical dimerization and mass diffusion (Eq. 2-162). 

The subsequent thermal processes201 give rise to diffusion of the polycarbonate substrate into the dye layer, decomposition of the dye, and mechanical deformation of the film due to thermal contraction. Each of these processes can contribute to a reduction in the optical path length of the low-intensity readout beam. The optics within the detector are designed such that phase differences due to the optical path length differences cause the light intensity falling on the detector to be reduced when the beam passes over a recorded mark .196... 

There are shown in Fig. 19 values of the eddy diffusivity calculated from the measurements by Sherwood (SI6). These data show the same trends as were found in thermal transport, indicating that the values of eddy diffusivity are determined primarily from the transport of momentum for situations where the molecular Schmidt numbers of the components do not differ markedly from each other. 

The increased understanding of turbulence and the extension of the analysis of potential flow have made possible the consideration of many thermal and material transfer problems which formerly were not susceptible to analysis. However, at present the application of such methods is hampered by the absence of adequate information concerning the thermal conductivities and diffusion coefficients of the components of petroleum. The diffusion coefficient in particular is markedly influenced by the state of the phase. For this reason much experimental effort will be required to obtain the requisite experimental background to permit the quantitative application of the recent advances in fluid mechanics and potential theory to dynamic transfer problems of practical interest. 

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