Artykuły (WFTIiMS)

Stały URI dla kolekcjihttp://hdl.handle.net/11652/174

Przeglądaj

Teraz wyświetlane 1 - 20 z 209

Field emission and microstructural characterization of diamond films deposited by HF CVD method
(Wydawnictwo Politechniki Łódzkiej, 2007) Jarzyńska, Dagmara; Staryga, Elżbieta; Znamirowski, Zbigniew; Fabisiak, Kazimierz; Gotszalk, Teodor; Woszczyna, Mirosław; Strzelecki, Włodzimierz; Dłużniewski, Maciej
Electron emission from diamond films (DF) deposited using HF CVD technique on silicon substrates has been studied. The field emission characteristics were analyzed using the Fowler-Nordheim model. The diamond films were also characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Raman Spectroscopy (RS) and Electron Spin Resonance (ESR) techniques. The correlation between electron field emission of investigated films, Raman spectra and concentration of paramagnetic centres has been discussed. The electron emission properties of diamond films improved after doping with nitrogen. The field emission was obtained at turn-on electric field equal to about 10 V/µm and about 3 V/µm, for undoped diamond films and N-doped diamond films, respectively. It seems that the change of turn-on field values and other emissive properties of thin diamond layers may be caused by different content of non-diamond phase (e.g. graphite phase) induced by doping.
On the contribution of the quadratic electrooptic effect to the nonlinear response proportional to the fourth power of modulating field
(Wydawnictwo Politechniki Łódzkiej, 2007) Izdebski, Marek; Kucharczyk, Włodzimierz
It is shown that the fourth-order electrooptic effect cannot be measured without a background of the contribution that is proportional to the square of the quadratic electrooptic coefficient. The contribution manifests on the fourth power of the modulating field and may be calculated. Thus, if the contribution is found to be comparable with the measured fourth-order electrooptic response, this apparent fourth-order effect should be taken into account in the interpretation ofthe results of the measurement.
Microscopic investigations of Gold Basin and El Hammani chondrites
(Wydawnictwo Politechniki Łódzkiej, 2007) Szurgot, Marian; Polański, Krzysztof
Elemental and mineral composition of Gold Basin and El Hammami meteorites discovered in 1995 and 1997 have been studied by analytical electron microscopy and optical microscopy. It was established that the main meteorite minerals: olivines, pyroxenes, kamacite and taenite as well as troilite identified in the samples represent extraterrestrial minerals typical of the ordinary chondrites. Feldspars represented by plagioclase, orthoclase, magnetite, calcite, chromite and silica have been also present in the studied samples. Chemical and mineral composition, iron content, petrologic types of chondrules, their abundance and sizes, the presence of troilite veins and abundance of nonoxidised iron phases confirm H class of El Hammami chondrite, i.e.. olvine-bronzite class, and L class of Gold Basin, i.e. olivine-hyperstene class.
Some of the photothermal properties of one- and two-layer structures
(Wydawnictwo Politechniki Łódzkiej, 2007) Pieszyński, Krzysztof
The results of numerical calculations of temperature on a multi-layer structures' surface illuminated with intensity periodically-modulated beam of light are presented. In fact the influence of some geometrical and thermal properties such structures on the amplitude of time-dependant temperature component is shown. Moreover, only one- and two-layer structures are taken into account.
Hole drift mobility in antrachinon layers
(Wydawnictwo Politechniki Łódzkiej, 2007) Kania, Sylwester
The drift mobility of holes in the antrachinon layers were determined. The layers were evaporated in the vacuum of the order of 10-5Torr. Due to the substrate temperature the layers were in the structure polycrystalline or the quasi-amorphous. There were no obtained the effect of the layers structure on the magnitude of the mobility of the carriers and on the transport mechanism.
What is the true order of magnitude of the quadratic electrooptic coefficient |g1111-g1122| in RDP crystal?
(Wydawnictwo Politechniki Łódzkiej, 2007) Górski, Piotr; Kilański, Łukasz; Ledzion, Rafał; Kucharczyk, Włodzimierz
Measurements based on the dynamic polarimetric technique of the electrooptic coefficient |g1111-g1122| are applied to determine the order of magnitude of the quadratic electrooptic effect in RDP. The results obtained confirm that the effect is two orders of magnitude smaller than widely quoted in the literature data obtained previously by the static polarimetric method.
Dielectric relaxation modes in antiferroelectric liquid crystal mixture
(Politechnika Łódzka, 2007) Wojciechowski, Marek
Mixture of liquid crystals, with induced antiferroelectric phase has been studied by means of dielectric spectroscopy. The dielectric measurements were carried out in a cell with gold electrodes at planar orientation. The characteristic of dielectric relaxation modes in all phases existing in the mixture are presented. The results are compared with the results obtained for the same mixture in the cell with ITO electrodes.
Thermodynamic properties of solid neon in the reduced all-neighbours approximation of the self-consistent phonon theory
(Wydawnictwo Politechniki Łódzkiej, 2007) Tomaszewski, Janusz; Malinowska-Adamska, Cecylia; Słoma, Piotr
The results of studies of physical properties of solid neon with the help of the reduced, all-neighbours approximation of the self-consistent phonon theory are presented. The interatomic interactions are described by the generalized Buckingham, Lennard-Jones and Morse self-consistent potentials. The parameters of these potentials in highest approximation with the number of nearest-neighbours are determined using experimental values for the lattice constant, cohesive energy, bulk modulus and the Debye characteristic temperature. Numerical results of our calculations for temperature and pressure dependence of selected physical properties are given and compared with available experimental data for Ne-20 fcc lattice.
Curing process and the curing product of a nematic epoxy resin containing ester groups
(Wydawnictwo Politechniki Łódzkiej, 2007) Włodarska, Magdalena; Mossety-Leszczak, Beata; Bąk, Grzegorz; Galina, Henryk
Curing process and the product of curing of one liquid crystalline epoxy monomer with a standard omine were examined. The reactions were monitored by DSC measurement and dielectric spectroscopy. Progress of curing of the examined mixture at different temperatures was shown. Influence of curing conditions on the final product was discussed and compared with other similar systems. DSC thermograms of the curing product were also analysed.
Laser surface melting of cobalt monocrystal
(Wydawnictwo Politechniki Łódzkiej, 2007) Rożniakowski, Kazimierz
The paper presents a concise description of laser surface melting of cobalt monocrystal and some related phenomena. Pulses of electromagnetic radiation of nano and mili-second duration, generated by Nd:YAG laser were used for surface heating. Light was incident on (0001) plane of cobalt monocrystal. The influence of surface roughness on the domain image observed with SEM ( type I magnetic contrast) was examined. Roughness of the surface was changed by polishing with diamond powders and superficial melting with nanosecond pulse of laser energy. The r.m.s. profile deviation σ of the examined surfaces was determined with reflexometric method. The depth of layer melted with nanosecond light pulse was evaluated for the isotropic model of metal and on the assumption that material constants are not temperature-dependent. Qualitative discussion of the phenomena associated with laser surface melting, i.e. generation of capillary waves and refinement of the Kittel type magnetic domains was included.
Self-consistent calculations of the dynamic, thermodynamic and elastic properties of a lattice of atomic crystals
(Wydawnictwo Politechniki Łódzkiej, 2007) Malinowska-Adamska, Cecylia; Słoma, Piotr
The application of the self-consistent phonon theory (SCPT) formulated by Plakida and Siklós on the basis of the double-time Green's function method to the atomic crystals: rare gas solids (RGS), quantum crystals (QC) and metallic crystals (MC) is discussed. The special attention is given in theoretical investigation of the dynamic, thermodynamic and elastic properties of fcc and bcc structures using the reduced all-neighbours approximation of SCPT. The interatomic interactions in the mentioned crystals are described by the various models, among them by the generalized (exp,m) Buckingham, (n,m) Lennard-Jones and (exp,exp) Morse self-consistent potentials. The potential parameters are determined self-consistently with the help of the zero-point experimental data: the lattice constant, sublimation energy, compressibility and Debye characteristic temperature. Within numerical calculations we study the influence of the number of "important" shells of neighbours on temperature and pressure variations of the selected physical properties of atomic crystals. The computed results are compared with available experimental data.
Kerr constant of Fomblin Z
(Wydawnictwo Politechniki Łódzkiej, 2008) Ledzion, Rafał; Karolczak, Stefan; Górski, Piotr; Kucharczyk, Włodzimierz
The Kerr constant B of polyperfluoroethylenemethylene oxide Fomblin Z has been determined within the temperature range 295-323K. At 300K the constant B was found to be equal to 1.7 10(-15) m/V2. The results obtained indicate usefulness of this oligomeric compound as an immersion liquid in measurements of the quadratic electrooptic effect and electrostriction in crystals.
Electrooptic modulation of light beams deviated far from normal incidence
(Wydawnictwo Politechniki Łódzkiej, 2008) Izdebski, Marek
It is shown that the electrooptic modulation of the phase difference for the light beams propagating oblique through the crystalline plane-parallel plate appears not only as the direct result of the field-induced changes in the refractive indices of refracted waves but also the modulation is due to the changes in the directions and paths lengths of the waves in the crystal. This indirect modulation may become important for light beams deviated significantly from the normal to the entrance and emergence crystal faces. Configurations with the light beams passing oblique through the plane normal to the optic axis are interesting in measurements of the linear electrooptic coefficients r41 and r42 in uniaxial crystals. Although in some crystals symmetries the coefficients r11 or r22 may contribute to phase difference, it is shown that the results obtained for different signs of the incidence angle allow to separate such contribution from that caused by r41 or r42.
Microstructure of NWA 4435 meteorite
(Politechnika Łódzka, 2008) Szurgot, Marian; Polański, Krzysztof
Elemental composition, mineral composition and microstructure of NWA 4435 meteorite found in 2006 has been studied by analytical electron microscopy and optical microscopy. It was established that the main meteorite minerals: olivines, pyroxenes, troilite, and graphite identified in the sample represent extraterrestrial minerals typical of carbonaceous chondrites. Chemical and mineral composition, petrologic type of chondrules, their abundance and sizes, the presence of troilite, and abundance of oxidized iron phases confirm CV3 class of this chondrite.
Gaussian light beam propagation in inhomogeneous medium
(Wydawnictwo Politechniki Łódzkiej, 2008) Pieszyński, Krzysztof
In this work the results of numerical calculations describing propagation of Gaussian light beam in inhomogeneous media is presented. Numerical calculation was based on scalar wave approximation. Additionally the split-step beam propagation method was exploited.
Role of ions mobility in flexoelectric deformations of conductive homeotropic nematic layers
(Wydawnictwo Politechniki Łódzkiej, 2008) Buczkowska, Mariola; Derfel, Grzegorz
Numerical studies of d.c. electric field induced deformations of homeotropic layers of flexoelectric nematics containing ions are presented. It is shown that anomalous dependencies of threshold voltage for deformations on ion concentration, which were found in our previous papers, are due to difference between mobilities of cations μ + and anions μ -. The influence of this difference on the deformations is analyzed. The set of equations describing the director orientation, the electric potential and the ion concentrations as functions of the coordinate normal to the layer, is solved. The calculations are performed for four types of nematic materials characterized by both signs of dielectric anisotropy and of the sum of flexoelectric coefficients. Finite surface anchoring strength is assumed. It is shown that the anomalies concerning the threshold vanish if μ + becomes equal to μ - results are explained by means of qualitative analysis of the electric field distributions.
Dielectric characteristics of antiferroelectric liquid crystalline mixture
(Wydawnictwo Politechniki Łódzkiej, 2008) Wojciechowski, Marek
Mixture of liquid crystals, with induced antiferroelectric phase has been studied by means of dielectric spectroscopy. The dielectric measurements were carried out in a cell with gold electrodes at planar orientation. The characteristic of dielectric relaxation modes in all phases existing in the mixture are presented.
Charge carrier conductivity mechanism for activated tetracene layers
(Wydawnictwo Politechniki Łódzkiej, 2008) Kania, Sylwester; Kuliński, Janusz
The activation process and the transport process for electrons in the tetracene layers is considered. Obtained results may suggests the hopping transport through the localized states near the Fermi level as a dominant kind of transport. Observed dependence of the conductivity on the vapor concentration of the activator molecules may suggest some ability to utilize.
Numerical investigation of deformations of planar flexoelectric nematic layers containing ions
(Wydawnictwo Politechniki Łódzkiej, 2008) Buczkowska, Mariola; Wasilewski, Grzegorz
Deformations of planar nematic layers of conducting nematic liquid crystal possessing flexoelectric properties and subjected to external d.c. voltage were studied numerically. Various kinds of electrodes, from strongly blocking to well conducting, were assumed. The calculations were performed for nematic material characterized by positive dielectric anisotropy and by positive sum of flexoelectric coefficients. The threshold voltages for deformations were computed for various ion concentrations and for several rates of electrode processes. The enhancement as well as reduction of the threshold were observed. Well defined dependence of layer behaviour on the kind of electrodes and on the ion concentration was found. These effects are due to interactions between flexoelectric polarization and strong electric field of high gradient.
Sliding mode approach to congestion control in connection-oriented communication networks
(Wydawnictwo Politechniki Łódzkiej, 2009) Bartoszewicz, Andrzej; Żuk, Justyna
In this paper, a novel sliding mode flow controller design for the connection-oriented communication networks is proposed. The networks are modeled as discrete time systems with the available bandwidth acting as disturbance. The proposed controller is designed in such a way that the closed-loop system stability and fast, finite time error convergence are ensured. In order to avoid the problem of excessive control signal magnitude, a sliding mode controller with saturation is proposed. When this controller is applied no bottleneck link buffer overflow and full utilization of its available bandwidth are guaranteed. Furthermore, transmission rates generated by the controller are always upper bounded and nonnegative.