Search results for "Direct current"
showing 10 items of 88 documents
Systematical, experimental investigations on LiMgZ (Z= P, As, Sb) wide band gap semiconductors
2011
This work reports on the experimental investigation of the wide band gap compounds LiMgZ (Z = P, As, Sb), which are promising candidates for opto-electronics and anode materials for Lithium batteries. The compounds crystallize in the cubic (C1_b) MgAgAs structure (space group F-43m). The polycrystalline samples were synthesized by solid state reaction methods. X-ray and neutron diffraction measurements show a homogeneous, single-phased samples. The electronic properties were studied using the direct current (DC) method. Additionally UV-VIS diffuse reflectance spectra were recorded in order to investigate the band gap nature. The measurements show that all compounds exhibit semiconducting be…
The effect of the axial heat transfer on space charge accumulation phenomena in HVDC cables
2020
To date, it has been widespread accepted that the presence of space charge within the dielectric of high voltage direct current (HVDC) cables is one of the most relevant issues that limits the growing diffusion of this technology and its use at higher voltages. One of the reasons that leads to the establishment of space charge within the insulation of cables is the temperature dependence of its conductivity. Many researchers have demonstrated that high temperature drop over the insulation layer can lead to the reversal of the electric field profile. In certain conditions, this can over-stress the insulation during polarity reversal (PR) and transient over voltages (TOV) events accelerating …
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 …
Investigation of Different Iontophoretic Currents Profiles for Short-Term Applications in Cosmetics.
2018
[EN] This study aimed at investigating the effect of electrical current profile upon the iontophoretic transport of (i) ascorbic acid (AA) and (ii) ellagic acid (EA), into porcine skin in vitro, and the impact of the physicochemical properties of both actives on their mechanism of transport when formulated in cosmetic compositions. The experiments were performed using a proprietary iontophoretic device containing a roller to apply the formulation. Three current profiles were tested: (i) galvanic direct current (DC), (ii) square unipolar pulse current (SPC), and (iii) galvanic direct current (DC) + pulse current (PC). The skin samples were collected at different sampling points, extracted an…
Energy Storage by using HVDC Power Cables
2018
The development of HVDC (high voltage direct current) systems closely follow the growth of global energy requirements. In particular, HVDC cables are conveniently used for the interconnection of geographical areas which need a low environmental impact and/or when submarines interconnections have to be built up. The paper investigates the stored energy value in an HVDC cable during its normal duty and if it is possible to take advantage of this energy when the cable is disconnected for some reason. In particular, the idea is to store the cable energy, which would be dissipated uselessly, by using a dedicated system and then reuse it when favorable conditions hold, e.g a convenient economic s…
Performance evaluation of directly photovoltaic powered DC PM (direct current permanent magnet) motor – propeller thrust system
2013
Photovoltaic (PV) powered directly coupled electro-mechanical system has wide applications (e.g. PV powered cooling fans in green houses, PV water pumping system, solar vehicles). The objective of this work is to analyse the operation of directly PV powered DC PM (direct current permanent magnet) motor – propeller system for selection of motor parameters. The performance of such system mainly depends on the incident solar radiation, operating cell temperature, DC motor and propeller load parameters. It is observed that the operating points of the PV DC PM motor – propeller system matches very closely with the maximum power points (MPPs) of the PV array, if the DC PM motor – propeller parame…
Progression of adverse effects over consecutive sessions of transcranial direct current stimulation
2017
final draft
Study of a new direct current atmospheric pressure glow discharge in helium
2011
Abstract In this study a new DC-APGD operated in He was developed and characterized. The discharge is operated at 0.9 kV and about 25–35 mA and at a gas flow of 100 ml/min. The source was spectroscopically studied and parameters such as the rotational temperature (Trot), the excitation temperature (Texc), the ionization temperature (Tion) and the electron number density (ne) were determined. The current–voltage characteristic of the source was studied as well. At optimized conditions the discharge operates in the normal region of the current–voltage characteristic. Rotational and excitation temperatures determined with the use of OH band and Fe I lines as thermometric species were of the or…
Primary Frequency Control in the Power System of Continental Europe including the Dynamics of the HVDC Link France-Great Britain
2020
The paper presents a study of primary frequency control within the power system of Continental Europe (CE) including the dynamics of the high voltage direct current (HVDC) link between France and Great Britain (GB). The large-scale dynamic model of the CE system originally provided by ENTSO-E is extended with a more detailed representation of the whole HVDC interconnection. The dynamics of the GB synchronous area is also considered in the analysis, implementing a system equivalent suitable for primary frequency control studies. The opportunity of frequency containment reserve exchange between the two areas through the link is also investigated, considering supplementary frequency controls w…
In vitro pulsatile and continuous transdermal delivery of buserelin by iontophoresis
1993
Abstract Transdermal delivery of buserelin, a nonapeptide, from hydroxyethylcellulose hydrogel through isolated human stratum comeum was studied. In vitro studies were carried out in a drug release apparatus (DAB 10/USP XII) using self designed rotary disk cells equipped with platinum electrodes. Different forms of current were examined. A pulsatile application of continuous current resulted in a step-like permeation profile. Different on/off ratios (5 min/55 min; 10 min/50 min; 15 min/45 min)) were studied. When continuous non-interrupted current with different current densities (0.1–0.3 mA·cm −2 ) was applied, linear dependence of the final cumulative amount of buserelin on current durati…