Papers by Keyword: Transmission

Abstract: This research developed a performance improvement of power transmission system to enhance performance during line disturbance using model Predictive control (MPC) control scheme. This research work was implemented using MATLAB 2023a. However, the parameters of these controllers are usually adjusted based on a linearized model of the power system, which typically depends on the system's operating point or state. To assess the performance of the developed scheme, multiple simulation studies were carried out under conditions where the voltage magnitude of the infinite bus and the transmission line reactance changed due to faults at the infinite bus and sending terminals. The results from the waveform analyses indicate that the dynamic characteristics of the system under investigation have significantly improved. settling time, at post fault of the transmission and from fault recovery settled time to its stable state value of 1.8sec compared to 2.8sec with minimal control effort that fluctuated between faults and system stability before settling time at the shortest time value of 2. 6305s in 2.42s compared to 4.28, in 1.92s compared, and 3.32s.

Abstract: Radiative cooling (RC) technology is becoming crucial with several prospective applications, either as a standalone or in conjunction with conventional cooling systems. The RC flux can be enhanced by tailoring selective spectral emissivity and suitable surface orientation (i.e., azimuth and tilting orientation). However, it has not been studied extensively from the perspective of emissivity modification in the composite layers. Polymer and ceramic particle composite’s emissivity (i.e. selective wavelength dependent spectrum) is based on the effective refractive index estimation. In this article we estimate the effective refractive index of the composite structures using Mie theory and the layer transmissivity approach. In the Mie theory, forward scattering from a composite sphere is monitored with respect to background refractive index. In the layer transmissivity approach, refractive index of composite is estimated from the transmission spectrum (i.e. Fresnel equations) of number of layers with different thickness. The refractive index from these two approaches is in the close agreement at large wavelengths (non-dimensional size parameter x=2πr/λ is below 1). However, the layer transmissivity approach yields a higher effective refractive index for the wavelength comparable to particle size (x =>1) inclusions with lots of fluctuations. The effective refractive index estimation aids in the designs of distributed Bragg stack and quasi-amorphous structure. The selective emissivity within the solar spectrum is also expected from quasi-amorphous structures of these existing polymer and ceramic particles composites. The potential applications of these findings are synthesis of coatings for radiative cooling of residential buildings and solar PV panel. Additionally, implementation of these coatings based radiative cooling phenomena would be very effective in terms of reduction of global warming and heat island effect.

Abstract: Africa's energy dynamics are marked by a blend of rapid urbanization, burgeoning populations, and growing industrialization, all against the backdrop of limited and often unreliable conventional energy infrastructure. This complex scenario prompts an exploration of the viability of hydrogen as a transformative energy solution. The continent's diverse renewable resources, from abundant solar and wind potential to hydropower capabilities, provide fertile ground for hydrogen production. However, Africa's energy transition journey is further complicated by the challenge of retrofitting or establishing sustainable energy systems in regions heavily reliant on fossil fuels. The tension between these established energy supply backbones and the imperatives of reducing carbon emissions necessitates innovative solutions. Hydrogen, with its potential for clean energy storage, emissions-free power generation, and industrial applications, offers a promising bridge between the need for modern energy access and environmental stewardship Drawing from case studies, the study delves the technological feasibility of harnessing hydrogen, considering existing energy infrastructure and emerging renewable technologies, the infrastructural challenges and opportunities presented by establishing hydrogen supply chains across diverse African regions. In conclusion, this paper underscores the significance of hydrogen as a pivotal pillar of Africa's sustainable energy future. This study aims to support policymakers, researchers, and industry stakeholders in navigating the path towards a hydrogen-powered Africa.

Abstract: This work describes a theoretical and analytical study of a temperature and pressure sensor based on II-VI semiconductors with a simple multi-quantum wells (MQWs) structure. The proposed sensor operates by detecting changes in the intensity (transmission coefficient) and energy of localized electronic states inside gaps under external perturbations of hydrostatic pressure and temperature. Specifically, the proposed MQWs structure is ZnO/Zn_1-XMg_XO with 10 cells, each containing two materials that form the wells and barriers, respectively. The structure is perturbed by a staircase defect consisting of three defects of the same material or geomaterial. The Green function method is used to study the transmittance of the structure, with cleavage and coupling operators employed. The objective of the work is to explore a new type of defect for use in sensing applications such as multi-quantum well sensors. Key parameters for evaluating the sensor's performance include full width at half maximum (FWHM), sensor sensitivity (S), quality factor (QF), detection limit (DL), signal-to-noise ratio (SNR), dynamic range (DR), detection accuracy (DA), the figure of merit (MF), and standard deviation. These parameters can be optimized by adjusting structural parameters such as the thickness of the staircase or material concentration. The study found that a geomaterial staircase defect provides higher sensitivity to pressure and temperature changes. Additionally, the step (δx) of the staircase defect influences the sensitivity of the localized states: with increasing steps, δx improves sensitivity to temperature and decreases sensitivity to pressure.

Abstract: In this paper using the transfer matrix method (TMM), we consider an electronic comb-like waveguides system composed by the periodicity of segment semiconductor (GaAs type) of length and grafted in its extremity by one semiconductor resonator (GaAlAs type) of length . These segments and resonators are considered quantum wires. The perfect system in question presents the electronic pass bands and electronic band gaps which allow to control and manipulate the electrons waves whose energy is identical to the energy of the gaps. We insert the defect at the resonator level in the middle of this system in question. Hence, very narrow localized defect states are created in the electronic band gaps, with probably high transmission rate and very important quality factor. These localized defect states shift to low energy by increasing the resonator defect length, while is move to high energy when the resonator defect concentration increases. In this study, we consider that the segments and resonators lengths are very small in front of their sections, so that the propagation of electronic waves occurs only in a single dimension.

Abstract: The transmission polarization metasurface converter is an effective method to realize the polarization manipulation of the transmission waves, and it is also the research hotspot of metasurfaces. A new broadband transmissive polarization converter was proposed based on the metasurfaces converted incident linearly polarized waves into circularly polarized waves of transmission. The top and bottom layers of the unit were axisymmetric metal patches. The top and bottom layers of metal patches were overlapped and the shape was like an arrow. The thickness of the substrate was 4mm. The polarization conversion mechanism of metasurface was illustrated by parameter optimization and current analysis. The simulation results show that when the metasurface works in the frequency band of 6.71GHz~8.45GHz, the linearly polarized incident wave can be converted into a circularly polarized transmitted wave with axial ratio less than 3dB, and the relative bandwidth can reach 23%. The designed polarization converter has a simple structure and the potential application value in electromagnetic wave control of radio frequency devices.

Abstract: The present study investigated effects of fabric parameters on the water vapor transmission of socks fabric, which was measured by the cup method. It was found that the water vapor transmission of fabric was negatively proportional to the content of cotton and yarn count, before washing. Meanwhile, washing was found to increase the water vapour transmission.

Abstract: This article is dedicated to the questions of development of technological bases for the manufacturing blanks of friction disks with molybdenum gas-thermal coating applied by plasma spraying, for working in oil in the transmission units of transport machines. For ensure high performance indicators, there is has been offered a technological scheme for manufacturing friction disk blanks: short blasting preparation of the surface of the disk’s steel base, applying a molybdenum coating, that characterized by high adhesion to the ferrous metals, mechanical processing of the coating by grinding, monitoring the coating’s quality. The developed technological bases for manufacturing blanks of friction disks with molybdenum gas-thermal coating, applied by plasma spraying, for working in oil in transmission units of transport machines are contributed to the creation of efficient products with enhanced performance indicators for friction coefficient, wear resistance, reliability in modern conditions at the enterprises.

Abstract: In this paper, we research the relief of surfaces of wedge bodies of freewheeling mechanisms. The results obtained by scanning probe microscope let us correct predicted deterioration parameters of a wedge body and consider the effect of surfaces’ altitude quality indicators while designing mechanisms. Mark out relative area of bearing.

Abstract: Methods of the optical metallography, TEM, SEM-technique, tests for hardness and wear resistance are used to investigated the structural - phase transformation in metal blanks from alloy VT23 at cutting treatment in an interval of speeds 2...120 m/min are given. The patterns of interaction of dynamic plastic deformation and destructions on macro-, meso-, micro-and nanolevels are determined. It is shown that the formation in metal blank of modulated high-tensile secondary nanostructures promotes a heightening of a protective wearproofity of treated metal blank, but cutting edge, lowering a wearproofity, of the cutting tool.