The Effect of Oxygen Mixing Percentage on Structural, Optical and Electrical Properties of ZnTiO3 Thin-films Grown by Rf Magnetron Sputtering.

Perovskites are important composites in the area of multidisciplinary applications. It is achieved by carefully choosing and tuning the properties of the thin-film at the deposition. In this paper, ZnTiO3 (ZTO) thin-films were being deposited on quartz and N-Si substrates by RF magnetron sputtering. The thin-films were developed at room temperature, oxygen percentage levels varying from 0 to 100, and annealed at 600oC. The electrical, optical, morphological, and structural properties were analyzed as a function of oxygen mixing percentage (OMP). The crystallinity of the cubic structured ZTO thin-film is found to be high at 25 OMP, and it is gradually decreased with increased OMP. The surface morphology of the thin-film is observed, and roughness is measured from the atomic force microscope. Raman Spectroscopy investigated the phase formation and the vibrational modes of the thin-film with their spectral de-convolution. The ZTO thin-films optical properties were investigated using transmittance spectra. The ZTO thin-film indicated the highest refractive index of 2.46, at 633nm with optical bandgap values of 3.57 eV, with a thickness of 145nm and 25 OMP. The refractive index, thin-film thickness, and excitation coefficient were analyzed using the Swanepoel envelope technique. Electrical characteristics of ZTO thin-film are measured from the optimized conditions of the thin-film with conventional thermionic emission (TE) technique.

Methodology for determining permissible operating modes of DC traction motor of quarry dump truck to ensure satisfactory commutation

The article considers an approach to determining the permissible ranges of changes in the armature voltage, armature current and the excitation coefficient of the DC traction motor of a mining dump truck to ensure satisfactory commutation. When the DC motor is running in the specified modes, the probability of sparking in the collector-brush unit with a degree of 2 points will be minimal. A method for determining the permissible operating modes of a mining dump truck traction motor to ensure satisfactory commutation is proposed. The method allows, based on the analysis of experimental data, to determine the permissible ranges of changes in voltage, armature current and excitation coefficient, at which the degree of sparking does not exceed 1½ points

Mutual Coupling Effect in Unequally - Spaced Linear Antenna Array Performance

Unequally-spaced arrays can offer some advantages over equally-spaced arrays as follows: reducing the side-lobed level for the broadband array with an identical excitation coefficient. However, array design techniques do not take into account the mutual coupling effect among elements. In this article, the effect of mutual coupling on the array radiation pattern is investigated and discussed through studying the input impedance of the elements. Next, a technique for reducingmutual coupling based on radiation patterns of elements is presented. In this technique, the log-periodic dipole antenna with a frequency ranging from 900 MHz to 2500 MHz is selected as an array element. The results based on the FEKO magnetic field calculation program have shown that at 900 MHz, the proposed antenna array reaches a side-lobed level of -17.4 dB. At frequencies of 1500 MHz, 2000 MHz, 2500 MHz, the grating lobe levels of this antenna array are lower than 6.7 dB, 9.5 dBand 8.3 dB compared to those of the equally - spaced antenna array.

Электродинамическая модель системы «излучатель-корпус объекта»

В целях выработки единого подхода к оценке роли корпуса подвижного объекта (грунтового, воздушного, корабельного, железнодорожного), на котором установлен малогабаритный излучатель произвольного типа, предложен единый энергетический подход с использованием понятия добротности. Показано, что добротность системы в широких пределах изменяется в зависимости от места установки малогабаритного излучателя. Для оценки вклада корпуса объекта в общую эффективность системы предложен параметр коэффициент возбуждения корпуса объекта, определяемый соотношением идеальной добротности малогабаритного излучателя в свободном пространстве к идеальной добротности излучателя, размещенного на корпусе подвижного объекта. Проанализированы пределы изменения данного коэффициента в зависимости от координат места установки излучателя и его типа (электрического или магнитного). Указанный подход позволяет численно оценить коэффициент полезного действия системы излучатель-корпус объекта при рассмотрении антенны произвольного типа, расположенной в произвольном месте корпуса.In order to develop a unified approach to assessing the role of the body of a moving object (ground, air, ship, or rail) equipped with a small-sized radiator of an arbitrary type, a unified energy approach is proposed using the concept of quality factor. It is shown that the quality factor of the system varies widely depending on the installation location of a small-sized radiator. To assess the contribution of the objects body to the overall system efficiency, a parameter is proposed - the excitation coefficient of the objects body, which is determined by the ratio of the ideal quality factor of a small-sized radiator in free space to the ideal quality factor of a radiator mounted on the body of a moving object. The range of this coefficient is analyzed depending on the location coordinates of the installed radiator and its type (electric or magnetic). This approach allows the numerical evaluation of the efficiency of the radiator objects body system when considering an antenna of an arbitrary type located in an arbitrary location on the body.

Numerical Investigation of Vortex-Induced Vibrations of a Flexible Riser with Staggered Buoyancy Elements

This paper presents a numerical algorithm used together with a Finite-Element based Vortex-Induced Vibration (VIV) prediction software VIVANA to obtain a hydrodynamic force coefficient database based on response measurements of flexible riser VIV model test of staggered buoyancy elements. The excitation coefficient database is parameterized; and the representative parameters are systematically varied in VIVANA simulations until the predicted responses in terms of mode number, response frequency, root-mean-square (RMS) response amplitude, and RMS curvature agree well with the experimental data under same flow and boundary conditions. An optimal set of force coefficient database for both the buoyancy element and the bare riser section is obtained and a significant improvement in VIV prediction by VIVANA is achieved. The obtained hydrodynamic force coefficient database can be also applied to other empirical VIV prediction programs. The sensitivity of using the same database to predict the VIV of different configurations has also been investigated.

Prediction of Combined Inline and Crossflow Vortex-Induced Vibrations Response of Deepwater Risers

Deepwater risers are susceptible to vortex-induced vibrations (VIV) when subjected to currents. When responding at high modes, fatigue damage in the inline (IL) direction may become equally important as the crossflow (CF) components. Accurate calculation of both IL and CF responses is therefore needed. Empirical VIV prediction programs, such as VIVANA “Passano et al. (2016, “VIVANA—Theory Manual Version 4.8,” Trondheim, Norway),” SHEAR7 “(Vandiver, J. K., and Li, L., 2007, “Shear7 v4.5 Program Theoretical Manual,” Department of Ocean Engineering, Massachusetts Institute of Technology, Cambridge, MA),” and VIVA “Triantafyllou et al. (1999, “Pragmatic Riser VIV Analysis,” Offshore Technology Conference, Houston, TX, May 3–6, Paper No. OTC-10931-MS.)” are the most common tools used by the offshore industry. Progress has been seen in the prediction of CF responses. Efforts have also been made to include an IL load model in VIVANA. A set of excitation coefficient parameters were obtained from rigid cylinder test and adjusted using measured responses of one of the flexible cylinder VIV tests. This set of excitation coefficient parameters is still considered preliminary and further validation is required. Without an accurate IL response prediction, a conservative approach in VIV analysis has to be followed, i.e., all current profiles have to be assumed to be unidirectional or acting in the same direction. The purpose of this paper is to provide a reliable combined IL and CF load model for the empirical VIV prediction programs. VIV prediction using the existing combined IL and CF load model in VIVANA is validated against selected flexible cylinder test data. A case study of a deepwater top tension riser (TTR) has been carried out. The results indicate that VIV fatigue damage using two-dimensional directional current profiles is less conservative compared to the traditional way of using unidirectional current profiles.

Hydrodynamics of Flexible Pipe With Staggered Buoyancy Elements Undergoing Vortex-Induced Vibrations

Flexible pipe with staggered buoyancy elements such as lazy wave riser and drilling riser has been widely used in ocean engineering. Under the influence of sea current, both of the buoyancy elements and the riser may experience vortex induced vibrations (VIV). However, when VIV occurs, hydrodynamic characteristics of the buoyancy elements and its influence on hydrodynamic force of the bare pipe still need investigation. The purpose of this paper is to reveal the hydrodynamic characteristics of flexible pipe with staggered buoyancy elements undergoing VIV. The crossflow (CF) hydrodynamic coefficients of the flexible pipe with 25%, 50%, and 100% coverage of staggered buoyancy are obtained from model tests, using hydrodynamic forces and coefficients identification method. Then, the characteristics of added mass coefficients and excitation coefficients in CF direction are analyzed. The results show that the added-mass coefficients of bare pipe are relatively larger than those of buoyancy module, while the total mass per unit length (sum of structural mass and added mass) is consistent along the pipe. Similarly, the range of excitation coefficient on the buoyancy elements is smaller than that on the bare pipe, and their ratio is equal to the reciprocal of diameter ratio 2.5.

Prediction of Combined IL and CF VIV Response of Deepwater Risers

Deepwater risers are susceptible to Vortex Induced Vibrations (VIV) when subjected to currents. When responding at high modes, fatigue damage the in in-line (IL) direction may become equally important as the cross-flow (CF) components. If a riser experiences directional currents, fatigue damage must be evaluated at several locations on the cross-section’s circumference. Accurate calculation of both IL and CF responses are therefore needed. Empirical VIV prediction programs, such as VIVANA, SHEAR7 and VIVA, are the most common tools used by the offshore industry to design against VIV loads. Progress has been seen in the prediction of CF responses. Efforts have also been made to include an IL load model in VIVANA. A set of excitation coefficient parameters were obtained from rigid cylinder test and adjusted using measured responses of one of the flexible cylinder VIV tests. This set of excitation coefficient parameters is still considered preliminary and further validation is required. Without an accurate IL response prediction, a conservative approach in VIV analysis has to be followed, i.e. all current profiles have to assumed to be uni-directional or acting in the same direction. The purpose of the present paper is to provide a reliable combined IL and CF load model for the empirical VIV prediction programs. VIV prediction using the existing combined IL and CF load model in VIVANA is validated against selected flexible cylinder test data. A case study of a deepwater top tension riser (TTR) has been carried out. The results indicate VIV fatigue damage 1 using 2D directional current profiles is less conservative compared to the traditional way of using unidirectional current profiles.