Search results for "Energy engineering"
showing 10 items of 1099 documents
Controlling the Formation of Sodium/Black Phosphorus IntercalationCompounds Towards High Sodium Content
2021
The solid-state synthesis of pure sodium-black phosphorus intercalation compounds (Na-BPICs) has been optimized in bulk for two stoichiometric ratios. Specifically, in-situ X-Ray diffraction (XRD) allowed the precise identification of the optimal temperature range for the formation of Na-BPICs: 94°C–96°C. Moreover, as the undesired formation of Na3P takes place at this very same range, we succeeded in introducing a new synthetic route based on a fast-thermal ball milling implementation that results in the bulk production of BPIC without Na3P in 9 out of 10 cases. Finally, by combining XRD, Raman spectroscopy, and DFT calculations we developed a new structural model for Na-based BPICs showin…
Structure and superconducting properties of YBa2(Cu1−x Fex)3O7
1988
Fe-substituted Y-Ba-Cu superconducting oxide compounds were investigated by dc-magnetic susceptibility measurements, powder X-ray diffraction and Mdssbauer spectroscopy. Fe substitution caused a structural transformation from orthorhombic to tetragonal. Up to 4 at% Fe Tc was almost unaffected. It was found that superconductivity in Cu oxides does not depend on orthorhombic crystal symmetry.
Investigation of AC Electrical Properties of MXene-PCL Nanocomposites for Application in Small and Medium Power Generation
2021
The paper examined Ti3C2Tx MXene (T—OH, Cl or F), which is prepared by etching a layered ternary carbide Ti3AlC2 (312 MAX-phase) precursor and deposited on a polycaprolactone (PCL) electrospun membrane (MXene-PCL nanocomposite). X-ray Diffraction analysis (XRD) and Scanning Electron Microscopy (SEM) indicates that the obtained material is pure Ti3C2 MXene. SEM of the PCL-MXene composite demonstrate random Ti3C2 distribution over the nanoporous membrane. Results of capacitance, inductance, and phase shift angle studies of the MXene-PCL nanocomposite are presented. It was found that the frequency dependence of the capacitance exhibited a clear sharp minima in the frequency range of 50 Hz to o…
Time Evolution of Partial Discharges in a Dielectric Subjected to the DC Periodic Voltage
2022
Partial discharge (PD) detection can be considered one of the most useful tools for assessing the insulation conditions of the power apparatus in high-voltage systems. Under AC conditions, this analysis is widely employed in online and offline tests, such as type tests or commissioning, and can be carried out by applying the phase-resolved PD (PRPD) method, since the patterns can give information about the defect classification. Under DC voltages, the classic pattern recognition method cannot be performed, and the measurements show complexities related to the nature of the phenomena. For this reason, to date, a standard for PD measurements under DC does not exist. In previous papers, a new …
Using Search Algorithms for Modeling Economic Processes
2013
Abstract Economic issues are placed in formal practice, when is desired a modelling of the economic process, a manufacturing process, a device, etc. Each share of that economic process is denoted by a, b, c, d, these actions with defined time periods and action pairs are formed strings of the form, ab * cab * bc ., ab, bb, bc. so for them there are no other restrictions. If the graph is viewed as a system image, nodes representing components, then an immediate interpretation of an arc (xi, xj) are the component xi that is said to directly influence component xj. If nodes have the significance of possible states of a system when a spring (xi.xj) means that, the system can jump from state xi …
Taxation in Romania – Some Positive Aspects
2013
Abstract The field of taxation is often a subject of analysis, due to its importance for the formation and administration of public financial resources. By taking into account the local, national and international size of taxation, may be thus identified strengths, weaknesses, opportunities and threats. Although the taxation in Romania is often criticized both by taxpayers and by specialists, there is a progress in taxation field as a result of actions taken in forming and managing fiscal revenues. Without claiming an exhaustive approach, through this article we mention some positive aspects of Romanian taxation. We believe that these should be consolidated and continued.
Minimum power losses by using droop coefficients regulation method with voltage and frequency constraints in islanded microgrids
2018
In this paper, a droop coefficients regulation methodology is proposed for an islanded microgrid to optimize the power losses. Based on the P-f and Q-V relations to adjust the droop coefficients at every loading condition, the optimized operating set point generates minimum power losses operation while satisfying the constraints of voltage and frequency limitation. A 9-bus case study is here implemented to show the effectiveness of this new approach as well as the improved operation quality of the system.
Optimal power flow for technically feasible energy management systems in islanded microgrids
2016
This paper presents a combined optimal energy and power flow management for islanded microgrids. The highest control level in this case will provide a feasible and optimized operating point around the economic optimum. In order to account for both unbalanced and balanced loads, the optimal power flow is carried out using a Glow-worm Swarm Optimizer. The control level is organized into two different sub-levels, the highest of which accounts for minimum cost operation and the lowest one solving the optimal power flow and devising the set points of inverter interfaced generation units and rotating machines with a minimum power loss. A test has been carried out for 6 bus islanded microgrids to …
Comprensión de textos expositivos académicos en e-book Reader y en papel: influencia del conocimiento previo de dominio y la aptitud verbal
2018
espanolResumen: En un estudio del que participaron 102 estudiantes universitarios, se comparo la comprension en la lectura de textos expositivos academicos impresos versus en formato de e-book Reader. Se examinaron los efectos del soporte, del conocimiento especifico de dominio previo del lector y la aptitud verbal. Asimismo se indagaron las actitudes de los estudiantes hacia los soportes textuales antes y despues de la experiencia. Los resultados sugieren que el e-book Reader beneficiaria a los lectores competentes, y/o que podria promover mayor actividad metacognitiva en los procesos de comprension. Asimismo, las opiniones hacia el e-book Reader cambiaron despues de la experiencia, aunque…
Exergy Recovery during LNG Regasification: Electric Energy Production - Part Two
2009
In liquefied natural gas (LNG) regasification facilities, for exergy recovery during regasification, an option could be the production of electric energy recovering the energy available as cold. In a previous paper, the authors propose an innovative process which uses a cryogenic stream of LNG during regasification as a cold source in an improved combined heat and power (CHP) plant. Considering the LNG regasification projects in progress all over the World, an appropriate design option could be based on a modular unit having a mean regasification capacity of 2 × 109 standard cubic meters/year. This paper deals with the results of feasibility studies, developed by the authors at DREAM in the…