Light-reflecting characteristics of optically rewritable electronic paper

Light-reflecting characteristics play a crucial role in optically rewritable liquid crystal display (electronic paper). By using a special optimizer software, light-reflecting characteristics of the twisted nematic cell were calculated. The achieved values of the normalized reflection coefficients range within ∼ 0.03 - 0.43, which is comparable or better than other commercial technologies. The calculated contrast ratio of the device is 10 : 1. A 2D image, which can be displayed on the electronic paper was obtained. Comparison of the simulated background color and contrast ratio is very similar with the results, which were obtained in experimental cells of other studies. Our calculations indicate that angular dependence of the reflectance coefficient is almost uniform within a wide range of viewing angles.

Multiband and Low-Profile Frequency Reconfigurable Microstrip Patch Antenna Design Using Single PIN diode for WiFi/GPS applications

The novel and simple approach for achieving frequency tunability is presented. The frequency tunability is achieved using a single PIN diode. PIN diode located on the upper side of the structure to reduces the biasing complexity. The superstrate structure along with the corner truncation helps for enhancing the performance parameters, as well the location of feed and slot of the patch is varied for locating best performing points. This design provides the multiband frequency tunability behavior with the maximum frequency tunability of 100 MHz. The design provides the minimum reflectance coefficient of -22.56 dB, the directivity of 6.98 dB, the total gain of 3.683 dB, normalized directivity of 88 0 using the low profile (FR-4) substrate which helps for the cost reduction and mass production. The simulation is carried out using the HFSS tool. The fabrication of the proposed design is also presented. This design suitable for Wifi, GPS, and many more wireless communication applications.

Optically Rewritable Liquid Crystal Displays: Characteristics and Performance

Recent achievements in the photoalignment technique for fabrication of optically rewritable electronic paper with high performance characteristics are surveyed with emphasis on temporal constraints on the exposure process. The possibility of creating electrode-free electronic paper has very important practical aspects. However, many existing studies do not include sufficient analysis on how to achieve acceptable reflective characteristics within short exposure time. In order to achieve this goal, we have applied the rotational diffusion model. We find that the parameters of the diffusion model can be adjusted to get acceptable light-reflecting characteristics within 10 s of exposure. In comparison with the long-time exposure, the reflectance coefficient reduces by 24%. The route to material improvements for optimized e-paper device is discussed.

Preparation, structural investigation and optical properties determination of composite films based on PAZO polymer doped with GeTe4-Cu chalcogenide particles

The work presents preparation, structural investigation and optical properties characterization of composite films based on the azopolymer (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2- ethanediyl, sodium salt]), shortly PAZO, doped with 1 wt.% particles of the previously synthesized by us new tellurium containing chalcogenide system (GeTe4)100-xCux, where x = 5, 10, 15 and 20 mol.%. X-Ray diffraction (XRD) was applied to analyze the structure of the chalcogenide bulk material. Transmission electron microscopy (TEM) has been used to study the particles and the composite films morphology. The transmittance coefficient (T), the reflectance coefficient (R), the refractive index (n), the extinction coefficient (k), the optical absorption coefficient (α) and the optical band gap (E_g^opt) of the composite films were determined. Birefringence was induced by a He-Cd laser with a wavelength 442 nm and measured with probe Diode Pumped Solid State (DPSS) laser at 635 nm. The influence of the dopants concentration on the optical performance of the composite films has been discussed.

Structural, Thermal, Optical Characterizations of PANI/PMMA Composite Doped by TiO2 as an Application in Optoelectronic Devices

The casting method was employed for the preparation of polymer blend films doped with TiO2 (0.5, 1, 1.5, and 2.3 wt.%). The XRD outcomes show that TiO2 phase formation is anatase, with an average crystal size of 20.25 nm. PANI/PMMA-TiO2 nanocomposites samples have an amorphous nature. In addition, the degree of amorphousity is increased with the increase of the content of the TiO2 NPs. The FTIR method was employed for presenting the vibrational bands of the nanocomposites and the intermolecular bonding of the blend with the TiO2 NPs. The applied investigation involved the optical constant like absorption as well as t90-etransmission spectra, refractive index, reflectance, coefficient extinction, dielectric constant’ imaginary and real parts, the susceptibility (χ3) of third order and the optical band gaps. The optical band gap (Eg) values of the films of fabricated nanocomposites was lower upon doping (≤ 1.5 wt.%). The reduction of the value happened due to the introduction of the preselected TiO2 NPs into thin films. Such values significantly match the values which were revealed by the Tauc technique. It was proved through DSC and TGA techniques that TiO2 NPs can lead to the enhancement of the polymer blend in terms of thermal stability. As displayed by the DSC analysis, there is a single Tg of the polymer blend (PANI/PMMA), which prove their miscibility. The optical constants displayed by the experimental results show noticeable changes upon raising the doping concentrations. The resultant doped thin films indicate that the fabricating high-efficient optoelectronic machines are greatly promising.

Drying out conifers classification employing TripleSat satellite data

<p>Drying out of coniferous trees (Picea abies) due to bark beetle infestation and other diseases leads to a high rate of conifers mortality. The coniferous forests in Belarus are largely exposed to damage by the bark beetle, the early symptoms of which are the changes in the color and loss of shine of the needles.  </p><p>Purpose of the work is to identify drying out stages combining the TripleSat multispectral satellite data (spatial resolution 3.2 m MS, 0.8 m PAN, bands R, G, B, NIR) for the test coniferous forest area in Belarus (53.65419º N, 27.640213º E) with quasi-synchronous airborne photo-spectral measurements which have been used as a reference data. Airborne measurements of reflectance coefficient function of underlying coniferous trees have been carried out by employing two spectrometers (wavelength range 400-900 nm, spectral resolution 4.3 nm) and photo-camera (visible range, FOV 50º) mounted on board of Diamond DA40NG aircraft in nadir geometry.  </p><p>Airborne RGB-images have been used for visual identification of the type of underlying surface and for subsequent training data set formation. Training data consist of several sets (10 – 20) of vegetation indexes for each type of underlying surface. The linear discriminant analysis (LDA) classification algorithm has been applied in this study for distinguishing the conifers drying out stages. A set of vegetation indices evaluated for each reflectance coefficient function has been applied as input data for LDA classification algorithm.</p><p>LDA classification algorithm has been employed to the TripleSat image for identification drying out stages of coniferous trees. The reference data for LDA classification algorithm of the TripleSat image included the combination of coordinates and corresponding types of underlying surface obtained from the results of the airborne experiment classification. A set of vegetation indices has been derived for each pixel of the image and used as input data for LDA algorithm; also vegetation indices calculated for the reference pixels have been applied for training data set formation.</p><p>The classification accuracy of three conifers drying out stages based on the airborne experiment is estimated to be in a range of 27 - 74%. The verification of TripleSat classification results has been performed by visual comparison with high resolution aerial images.</p>

Influence of Coccolithophore Blooms on the Bio-Optical Characteristics of the Black Sea Waters according to Observations in 2012 and 2017

This paper presents and discusses the results of optical and biological measurements performed during the coccolithophore blooms. This study uses data of measurements from a stationary oceanographic platform (near the Southern coast of Crimea, 44°23' N, 33°59' E) in July 2012 (7–16 July) and in May 2017 (24–31 May), and data obtained during the R/V “Professor Vodyanitsky” expedition to the northern part of the Black Sea in June 2017 (14–30 June). Observation periods coincided with intensive blooms of coccolithophore. The measurements of the Secchi disk depth, light beam attenuation coefficient and reflectance coefficient, as well as biological determinations of the coccolithophore cells number in water samples, are considered and analyzed. In addition to field data, satellite information on the sea reflectance and backscattering are used. The beam attenuation coefficient, reflectance coefficient, backscattering coefficient and coccolithophore concentrations were increased as compared with no bloom period. The Secchi disk depth was abnormally low. The number of coccolithophore cells, according to biological data, varied from 150 thousand cells/L to 1.7 million cells/L and averaged 0.6 ± 0.4 million cells/L. According to these data, the estimated concentration of shed coccoliths was (1.46 ± 0.42) 1011 m-3 . The average coccolith concentrations calculated from satellite data were (1.29 ± 0.23) 1011 m-3 in July 2012, (1.32 ± 0.12) 1011 m-3 in May 2017, and (2.37 ± 0.69) 1011 m-3 in June 2017. During blooms, high variability was observed not only in optical properties, but also in biological properties, and the relationship between their spatial distribution was weak. From the optical point of view, the indicator of bloom is the number of coccoliths, not cells, which can lead to an incorrect description of the biological situation.

Examining the Diffuse Reflectance Spectra and the Radiation Stability for the Mixtures of BaSO4 Micropowders and SiO2 Nanopowders with Various Specific Surface Area

The paper is devoted to studying the effect of the specific surface area (SSA) of SiO2nanopowders (3 wt.%) added to BaSO4powders of a micron size on grain size distribution and diffuse reflectance spectra (ρλ) within the UV, visible, and near IR regions. Additionally, the authors have examined the spectra alteration (Δρλ) after irradiating with electrons (E=30 KeV). It has been established that mere mixing of the powders at a low concentration of nanoparticles leads to the post-irradiation decrease in the reflective power and to the subsequent increase in the reflectance coefficient stability.