Search results for "Control and Systems Engineering"
showing 10 items of 994 documents
Optical investigation of the OH− groups in the LiNbO3 doped by copper
2019
Doping ions and OH− groups absorption bands spatial profiles were investigated for the case of congruent LiNbO3 single crystal grown by Czochralski technique. Doping was performed after the crystal...
INFLUENCE OF MONOXIDES ADDITION ON SINTERING OF SODIUM-POTASSIUM NIOBATES SOLID SOLUTION
2008
ABSTRACT In this paper the preparation, structure and dielectric parameters of ceramics from different powders of pure potassium sodium niobate (KNN) and KNN doped with 1.0 wt% of Li2O, CdO, Bi2O3, MnO2, V2O5 and WO3 have been studied. The dopping of sintering aids did not affect the crystallographic structure of the ceramics significantly; all ceramic samples had a single-phase perovskite structure. Added elements Li2O, CdO, MnO2, V2O5 effectively decreased the sintering temperature of KNN (50°–80°C). All sintering aids influenced sinterability, microstructure and dielectric properties of ceramics. Dielectric constant for doped samples increased from 6000 up to 8000.
Drying rate control in microwave assisted processing of sliced apples
2018
The most enhanced microwave systems for the preparation of quality-dehydrated fruits continuously adjust the power level in order to maintain the product temperature above a target value. As a result, typical drying curves that exhibit high drying rates in the middle stage are obtained. This can often lead to quality damage or undesirable changes on food colour and texture. In response to these issues, a microwave system is proposed that can realise drying processes keeping drying rates constant. This approach required a continuous temperature adjustment of the apple slices under test, whose temperature was detected by a computer-aided infrared thermography system. Since temperature correct…
Effects of CuO doping on structure, microstructure and dielectric properties of BaTiO3–PbTiO3 solid solution
2019
Ba0.7Pb0.3TiO3 and Ba0.7Pb0.3TiO3+yCuO (y = 0.1 wt%, 0.5 wt%, 1 wt% and 3 wt%) samples were prepared by a solid state reaction method. High purity raw materials were used. Structural properties of the sintered pellets were studied by X-ray diffractometer X’Pert PRO (PANalytical). A single phase of perovskite structure with tetragonal phase was identified at room temperature. The surface morphology of the obtained specimens was characterized by the scanning electron microscopy (Hitachi S4700). The investigations has shown that the synthesized ceramic materials are characterized by the high density, homogeneity of microstructure and low porosity. Dielectric spectroscopy was used to study the …
Photoelectric fields in doped lithium niobate crystals
2019
Photoinduced light scattering (PILS) in nominally pure stoichiometric and congruent lithium niobate single crystals (LiNbO3), and ones doped with B³⁺, Cu²⁺, Zn²⁺, Mg²⁺, Gd³⁺, Y³⁺, Er³⁺ cations was studied. All crystals have a relatively low effect of photorefraction and are promising materials for frequency conversion, electro-optical modulators and shutters. It was found that the photovoltaic and diffusion fields for some crystals have a maximum at a wavelength of 514.5 nm. All the crystals studied are characterized by a maximum of the integral intensity of the speckle structure of the PILS at a wavelength of 514.5 nm.
Steady State Counterbalance Valve Modeling with the Influence of Synthetic Ester Oils Using CFD
2020
This study looks in details at the effects of synthetic esters being applied to a counterbalance valve from the perspective of a system engineer. There is limited literature on the subject of applied synthetic esters and as such limited unbiased sources for information. This creates reluctance against the use of these fluids in sectors and regions with no prior experience and knowledge of what to expect. This study expands the applied literature by investigating a commercially available valve using commercial oils, a basic synthetic ester, a fully saturated synthetic ester and a typical mineral oil type for benchmarking. The investigation is based on both computational fluid dynamics and ex…
FORMATION OF FRACTAL MICRO- AND NANO-STRUCTURES IN CERAMIC TANTALUM PENTOXIDE UNDER CONCENTRATED FLUX OF LIGHT AND THEIR EFFECT ON THERMAL EXPANSION
2009
ABSTRACT Oxides of weak thermal expansion are the basis for stable ceramics and artefacts resistant to sharp cyclic variations of temperature. For technical applications is a wide interest in high-temperature materials of low or negative thermal expansion and, particularly, in studies of the micromechanisms in Ta2O5. Thermal expansion of ceramic pentoxides of tantalum is affected by conditions under which they are formed. After treatment by concentrated light flows anomalous segments of zero and even negative thermal expansion appear in ceramics of Ta2O5. The effect of treatment by concentrated light flux on formation of fractal nano-structures and thermal expansion of ceramic tantalum pent…
NEUTRON IRRADIATION EFFECTS IN PZ and PZT THIN FILMS
2005
ABSTRACT Neutron irradiation effects on highly oriented antiferroelectric PbZrO3 (PZ) and ferroelectric PbZr0.53Ti0.47O3 (PZT) thin films are investigated in view of their possible application as a temperature sensitive element in a new bolometer system for fusion devices like ITER. All investigated thin films were prepared by a sol-gel technique and by pulsed laser deposition (PLD) respectively. The dielectric properties were investigated in a frequency range from 1 to 250 kHz and at temperatures up to 400°C, prior to and after irradiation to a neutron fluence of 3 * 1022 m−2 (E > 0.1 MeV). After irradiation, the films were anneald in several steps up to 400°C in order to remove the radiat…
SPECTRAL AND TEMPORAL CHARACTERISTICS OF LIQUID CRYSTAL GOGGLES FOR VISION RESEARCH
2008
ABSTRACT Spectral and switching characteristics of two manufacturer liquid crystal goggles are tested. Experimentally the human stereovision acuity and threshold were studied for the case, when one eye random dot stereo stimulus simulated on the display is continuously blurred or the stimulus contrast is decreased. In order to determine the artefacts of two eye channel crosstalk on the stereostimuli separation the contrast ratio limits for the computer display phosphors wavelengths are determined.
Residual stresses in friction stir welded parts of complex geometry
2011
Residual stresses play a key role on the mechanics underlying the fatigue crack growth propagation of welded joints. Indeed, compressive residual stresses may induce a beneficial enhancement of the fatigue life under loading condition whereas tensile residual stresses may act to increase the stress distribution at crack tip, resulting in a life-threatening condition of the welded structure. In-process distortion and final geometry of welded joints are also affected by residual stresses. In this paper, the longitudinal residual stress distributions in friction stir welding (FSW) joints were investigated for butt and skin–stringer geometries, including lap and T configurations. To measure res…