Wyniki wyszukiwania - BazTech

1

Optical properties of a liquid crystal with small ordinary and extraordinary refractive indices and small optical anisotropy

Kędzierski J., Garbat K, Raszewski Z., Kojdecki M. A., Kowiorski K., Jaroszewicz L. R., Miszczyk E., Dąbrowski R., Zieliński J., Piecek W.

Opto-Electronics Review

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2014

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Vol. 22, No. 3

162-165

EN

Optical properties of a nematic liquid crystal with small refractive index and small birefringence were studied. The ordinary and extraordinary refractive indices and birefringence were measured as functions of temperature by using an Abbe refractometer and wedge nematic cells. From values of these indices the nematic orientational order parameter was calculated by using several methods and corresponding mathematical models. Kuczyński et al. method was found to be suitable for determining the order parameter also for materials featuring small ordinary refractive index, with unknown density.

2

Measurement of elastic constants of nematic liquid crystals with use of hybrid in-plane-switched cell

Nowinowski-Kruszelnicki E., Kędzierski J., Raszewski Z., Jaroszewicz L., Kojdecki M. A., Piecek W., Perkowski P., Olifierczuk M., Miszczyk E., Ogrosnik K., Morawiak P.

Opto-Electronics Review

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2012

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Vol. 20, No. 3

255-259

EN

A new method for quick and pretty accurate measurements of splay, twist and bend elastic constants of nematic liquid crystals is experimentally verified. The main concept relies on exploiting only the electric field and determining magnitudes of nematic elastic constants from threshold fields for Freedericksz transitions in only one hybrid in-plane-switched cell. In such cell the deformations of an investigated liquid crystal are controlled by three separated pairs of electrodes confining measurement domains. In two of them inter-digital electrodes are mounted on one cell cover. Splay, twist and bend elastic constants can be measured by a proper choice of electrodes' configuration together with orienting cover coatings (without applying magnetic fields). In this paper, we describe layout of our cells and results of experimental tests by using different liquid crystals: 5CB and 6CHBT (with positive dielectric anisotropy), Demus' esters (with negative dielectric anisotropy) and new liquid crystals mixtures produced in our university.

3

Determination of ordinary and extraordinary refractive indices of nematic liquid crystals by using wedge cells

Kędzierski J., Raszewski Z., Kojdecki M. A., Kruszelnicki-Nowinowski E., Perkowski P., Piecek W., Miszczyk E., Zieliński J., Morawiak P., Ogrodnik K.

Opto-Electronics Review

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2010

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Vol. 18, No. 2

214-218

EN

A new accurate and fast interference method for determining ordinary and extraordinary refractive indices of nematic liquid crystals is presented and discussed. The method relies on microscopic measurements of distances between interference fringes appearing in polarised parallel coherent monochromatic light beam transmitted normally to the surfaces through a wedge cell filled with a nematic. Both glass plates confining the cell are coated with a partly transparent thin film of metal which is deposited by evaporation in vacuum. Owing to the multiple reflections between the surfaces and a small edge angle, the interference fringes observed near the wedge apex edge are sharp and equidistant. To apply this method one needs only small amount of an investigated liquid crystal. Basic mathematical formulae and results of an experiment are briefly discussed.

4

Flexoelectric effect modelling

Kapanowski A.

Opto-Electronics Review

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2008

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Vol. 16, No. 4

375-378

EN

A statistical theory of dipole flexoelectric (FE) polarization in liquid crystals is used to calculate temperature dependence of order parameters, elastic constants and FE coefficients. Two systems with polar wedge-shaped and banana-shaped molecules are investigated. In both cases, the FE coefficients are proportional to the dipole moment component parallel to the molecule symmetry axis. It results from the symmetries of interactions and of the Mayer function. The origin of the FE effect and microscopic pictures of the distorted phases are discussed.

5

Modeling of material continua with defected and ordered microstructures

Rymarz Cz.

Journal of Technical Physics

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2002

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Vol. 43, no 3

277-285

EN

The paper contains a short presentation of some models of material continua with microstructure applying the methods of differential geometry. Two main kinds of microstructure are considered: dislocation, disclination, and unholonomic defects in plasticity, nematic liquid crystal as an example of oriented medium. The aim of this presentation is to illustrate the effectiveness of the methods of differential geometry in construction of the theory of microstructural media.

6

The order parameter of liquid-crystalline mixture with dichroic dye for TN LCD

Olifierczuk M., Kędzierski J., Raszewski Z., Zieliński J., Miszczyk E.

Biuletyn Wojskowej Akademii Technicznej

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1999

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Vol. 48, nr 4

99-106

EN

Paper contains results of studies on TL LC mixture with a black dichroic dye. The general information concerning a principle of an action of TN display with the dye is presented. The effect of the dye on temperature dependence of LC order parameter is discussed. The order parameter is confirmed by several methods (Lorentz-Lorenz's, Vuks-Chandrasekhar-Madhusudana's, Neugebauer-Saupe-Maier's procedures and extrapolation by Haller and Subramhanyam) for PCB.

PL

Praca zawiera wyniki badań nad efektem TN z czarnym barwnikiem dichroicznym. Podane są ogólne informacje na temat zasady działania displeja TN z barwnikiem chroicznym. Przedyskutowano wpływ barwnika na temperaturową charakterystykę parametru uporządkowania warstwy. Parametr uporządkowania otrzymano różnymi metodami (procedury Lorentz-Lorenz, Vuks-Chandrasekhar-Madhusudana, Neugebauer-Saupe-Maier i ekstrapolacje Hallera i Subramhanyamy) i sprawdzono dla PCB.

7

On discrete coefficient inverse problem

Kojdecki M. A., Kędzierski J., Raszewski Z.

Biuletyn Wojskowej Akademii Technicznej

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1999

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Vol. 48, nr 4

107-112

PL

Przedstawiono metodę określania zbioru dyskretnych parametrów charakteryzujących model matematyczny ośrodka fizycznego (ciągłego) - na przykład stałych materiałowych lub współczynników w równaniu różniczkowym. Zaproponowano wariacyjne sformułowanie dyskretnego współczynnikowego zagadnienia odwrotnego, umożliwiające rozwiązanie go za pomocą standardowych algorytmów. Jako przykład podana jest metoda wyznaczania stałych materiałowych nematycznego ciekłego kryształu.

EN

A method for determination of a set of discrete parameters characterising a mathemal model of a physical (continuous) medium, e.g. material constants or coefficients in differential equation, is presented. A variational formulation of a discrete coefficient inverse problem, which enables finding its solution by standard algorithms, is proposed. A method for determining material constants of nematic liquid crystal is demonstrated as an example.

8

Evaluation of polyimide aligning layers with high anchoring energy

Okulska-Bożek M., Borycki J., Prot T., Kędzierski J.

Biuletyn Wojskowej Akademii Technicznej

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1999

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Vol. 48, nr 4

57-66

EN

The group of poly(ester imides) characterized by various chemical structure has been synthesized. The quality of model nematic liquid crystal alignment of the polyimide layers using the interference wedge method has been tested. The relationship between the chemical structure of examined polyimides and their properties, especially the alignment depth, is discussed.

PL

Zsyntezowano szereg poli(estroimidów), charakteryzujących się zróżnicowaną budową chemiczną. Oceniano ich właściwości powłokotwórcze, adhezję do powierzchni szkła, odporność termiczną oraz właściwości ciekłokrystaliczne. Badano zdolność porządkowania modelowych nematycznych substancji ciekłokrystalicznych (NLC) przez otrzymane warstwy poliimidowe przy wykorzystaniu metody klina interferencyjnego (interference wedge method). Poszukiwano zależności pomiędzy chemiczną budową badanych poliimidów a ich wybranymi właściwościami, zwłaszcza głębokością porządkowania (alignmen depth). Planuje się kontynuację badań w celu potwierdzenia tezy, mówiącej że im wyższa jest głębokość porządkowania NLC przez warstwę poliimidową, tym większa powinna być wartość energii kotwiczenia danej powierzchni.