Electric Current Increases Research Articles

Adaptive neuro-fuzzy inference system-based controllers for smart material actuator modelling

An intelligent approach for smart material actuator modelling of the actuation lines in a morphing wing system is presented, based on adaptive neuro-fuzzy inference systems. Four independent neuro-fuzzy controllers are created from the experimental data using a hybrid method — a combination of back propagation and least-mean-square methods — to train the fuzzy inference systems. The controllers' objective is to correlate each set of forces and electrical currents applied on the smart material actuator to the actuator's elongation. The actuator experi-mental testing is performed for five force cases, using a variable electrical current. An integrated controller is created from four neuro-fuzzy controllers, developed with Matlab/Simulink software for electrical current increases, constant electrical current, electrical current decreases, and for null electrical current in the cooling phase of the actuator, and is then validated by comparison with the experimentally obtained data.

PH front tracking in the electrochemical treatment (EChT) of tumors: Experiments and simulations

The extreme cathodic and anodic pH fronts induced in the electrochemical treatment of tumors (EChT) are the main cause of tumor necrosis. Here, we study pH fronts interaction in a tissue under EChT through in vitro and in silico modeling. The in vitro model considers the tumor tissue as a buffered gel with saline (NaCl) content and the cathodic treated area as the area of phenolphtalein virage. The in silico model solves the 1D Nernst–Planck equations for ion transport in a four-ion electrolyte. In silico modeling predicts an initial neutral pH profile evolving into extreme cathodic alkaline and anodic acidic fronts moving towards each other and colliding, thus excluding the existence of a biological pH region between them. Moreover, the model predicts that as electric current increases, pH front scaling grows as t 1 , unveiling a transition from a diffusion to a migration governed regime. Theory and simulations have a strong correlation with experimental measurements. Since necrotic areas correlate well with those covered by alkaline and acid fronts advance, pH front tracking can be used to predict the extent of tumor destruction and thus, the assessment of EChT effectiveness.

High-rate hydrogenotrophic denitrification in a fluidized-bed biofilm reactor using solid-polymer-electrolyte membrane electrode (SPEME)

A fluidized-bed biofilm reactor equipped with a Solid-Polymer-Electrolyte Membrane Electrode (SPEME) cell was developed in order to enhance hydrogenotrophic denitrification of groundwater. Porous cubes made of polyvinylalcohol (PVA) were used as a biofilm carrier and continuous treatments using synthetic groundwater were carried out for 105 days. Electric current was changed step-wise from 0.4 to 4.0 A. Experimental results showed that efficient production and dissolution of hydrogen were achieved by application of electric current as well as high-rate denitrification simultaneously. Denitrification rates of nitrite increased with the increase of electric current. Overall denitrification rates attained to about 90 mg-N/L/h, which was 3 to 9 times as high as those reported in former studies. Supplying electric current of about two times of stoichiometric equivalent to the cell considered necessary for complete denitrification. Water quality in effluent was very stable and electrolytic voltage was low around 3 V. In addition, simple and secure operation was demonstrated over the experiment. From these results, it was concluded that the present fluidized-bed biofilm reactor equipped with a SPEME cell could be very feasible for high-rate hydrogenotrophic denitrification of ground water.

J. Cosmet. Sci., 58, 599–620 (November/December 2007) Ranking of aqueous surfactant–humectant systems based on an analysis of in vitro and in vivo skin barrier perturbation measurements

Accepted for publication July 19, 2007SynopsisWe propose that skin electrical current measurements can be used in vitro to effectively rank aqueous solutions containing surfactants and humectants (the enhancer) contacting the skin, relative to a PBS aqueous solution (the control) contacting the skin, based on their ability to perturb the skin aqueous pores. Specifically, we develop an in vitro ranking metric using the increase in the skin electrical current induced by an enhancer relative to the control. Aqueous contacting solutions containing (i) surfactants [SDS (sodium dodecyl sulfate)] and C12E6 [dodecyl hexa (ethylene oxide)], (ii) humectants (glycerol and propylene glycol), and (iii) a control (PBS) were studied. Utilizing the new in vitro ranking metric, these aqueous contacting solutions were ranked as follows (from the mildest to the harshest): glycerol < propylene glycol < PBS < C12E6 < SDS. In order to further develop this ranking methodology, which can potentially lead to the reduction, or elimination, of costly and time‐consuming procedures, such as human and animal testing and trial‐and‐error screening in vivo, it was important to correlate the findings of the in vitro ranking metric with direct in vivo skin barrier measurements. For this purpose, in vivo soap chamber measurements, including transepidermal water loss, visual skin dryness, and chromameter erythema measurements, were carried out on human volunteers using the aqueous surfactant–humectant solutions described above. The results of these in vivo measurements were found to be consistent with the ranking results obtained using the in vitro ranking metric. To further explore the validity of our model and to verify the skin barrier mitigating effect of glycerol, in vivo soap chamber measurements were carried out for aqueous SDS solutions containing 10 wt% added glycerol. These in vivo measurements support our recent in vitro finding that glycerol reduces the average radius and the pore number density of the skin aqueous pores, such that SDS micelles are hindered from penetrating into the skin and inducing skin barrier perturbation.

Lactate Transport in Soil by DC Fields

Electrokinetic injection of lactate, a negatively charged biodegradable organic, in homogeneous soils is evaluated. Net lactate migration rate on the order of 5 cm2 ∕V day is measured in sand from cathode towards the anode. The ionic injection in sand was dependent on current density; however, the increase in electric current did not result in an equivalent increase in lactate transport due to development of an appreciable electroosmotic (EO) flow from the anode to the cathode. While high EO flow ( ke on the order 10−6 to 10−5 cm2 ∕V s ) occurred in clay samples, ion migration from cathode to anode is the dominant transport process under relatively high current density ( 5.3 A∕ m2 in this study) and can be used as an effective transport mechanism for negatively charged additives. An effective lactate reactive transport rate of more than 3 cm∕d (under 1 V∕cm ) can be achieved in clays, which is at least two orders of magnitude greater than hydraulic injection under unit hydraulic gradient. Even though lact...

Effects of processing variables on microstructure formation in AZ31 magnesium alloys solidified with an electromagnetic vibration technique

In the present study, we solidified magnesium-based AZ31 alloys by an electromagnetic vibration technique in a superconducting magnetic field at a vibration frequency of 500 Hz. Two groups of processing variables were used to carry out experiments; one is that the electric current is set as 60 A so as to testify to the influence of magnetic flux density on microstructure development from 1 up to 10 T. The other is that the electric current increases from 10 up to 120 A in the static magnetic field of 10 T, from which the dependence of structure formation on electric current is revealed. It is found that with the increase of both magnetic flux density and the level of electric current, solidified structures experience a transition from coarse dendrites to equiaxed grains. The melt fluid induced by the vibration force during solidification may promote the dendrite to a fragment. Meanwhile, the solids can be driven to move out of the operating region of the solute redistribution boundary. These effects make it difficult to form a complete dendrite but a refined structure. Furthermore, the vibration force can result in the formation of deformation twins in the alloy that has a low critical stress for basal slip. Regarding the effect of the electric current on microstructure, heat (measured in joules) can be produced when a large electric current is imposed, which can ripen the microstructure and induce a nonuniform structure. The slow cooling rate also makes the number fraction of deformation twinning decrease due to a rapid migration rate of atoms at high temperatures.

Measurement of a 2-MeV Electron Beam Flux by Using an Aluminum-Nitride Detector

A small aluminum-nitride detector of 3 mm × 3 mm × 0.387 mm in size fabricated at the Oak Ridge National Laboratory is used to measure the 1 MeV ∼ 2 MeV electron beam from a beam facility at the Korea Atomic Energy Research Institute. Our objective is to check the linearity of the generated electric current relative to the electron beam intensity and to see if the electric current generated can be used as a measurement of the flux intensity. The results show that if the electric voltage applied to the detector is 2,000 V or higher and if the data are taken in a sufficiently short period of time so that the heat build up inside the detector is negligible, then the measured electric current increases linearly as the flux intensity increases. Hence, the measured value can be used as an estimate of the flux intensity, provided that one prior measurement of the beam with the given energy is available.

The size effect in current–voltage characteristic of VO2-based ceramics in the on-state

Current–voltage characteristics of (wt.%) 45VO2–15VPG–5Cu–35SnO2 ceramics in the on-state were investigated in the electric current interval between 0.3 A and 5 A. Transition from the region with negative differential resistance to the region with positive differential resistance is observed in current–voltage characteristic when electric current increases. The reason of such behaviour is the limitation of lateral expansion for the filament of VO2 metal phase by the sample’s size. The change in the sign of differential resistance occurs, when the cross-section area of the filament reaches the sample’s cross-section area. In this case the phase transition of VO2 into metal state is completed in the whole volume of the sample. Therefore at further increasing of current the current–voltage characteristic has the positive differential resistance.

Sub- and supersonic expansion of an arc channel in liquid

Post-breakdown expansion of a submerged discharge was considered taking into account the curvature of the plasma boundary and the sound and shock wave fronts. Numerical calculations were performed for an inter-electrode gap of 10−5 m, electrical current and voltage of 10 A and 100 V, respectively and a water medium. With an initial temperature of T0 = 2 × 104 K, a subsonic solution was found. The maximum expansion velocity is 1200 m s−1. The electrical current increases up to 9 A during ∼60 ns. With an initial temperature of T0 = 3 × 104 K, the plasma channel expansion starts as subsonic but after ∼5 ns it reaches the sonic velocity and transits it. The maximum velocity of the plasma boundary of about 2000 m s−1 is reached after ∼17 ns, and a shock wave appears in the undisturbed water. At this stage, water intensively evaporates into the plasma cavity. The electrical current jumps at the sonic transition point up to 10 A. The calculated pressure maximum is about 8 × 1010 Pa.

The influence of temperature hysteresis at metal-semiconductor phase transition on current-voltage characteristic of VO2–based ceramics

The current-voltage characteristics of ceramics (wt%) 80VO2-15VPG-5Cu and 45VO2-15VPG-5Cu-35SnO2 were investigated (VPG—vanadium phosphate glass). After switching to high electric current, these characteristics show a hysteresis loop in the electric current increase-decrease cycle. The cause of hysteresis is the different phase transition temperatures in VO2 crystallites for transition from semiconductor phase to metallic phase and for the reverse transition. The distinction of phase transition temperatures leads to the different equilibrium temperatures in the filament of the metallic VO2 phase, when ‘electric current increases and decreases. As the result, different power dissipated by electric current in ceramics sample is necessary for ensuring thermal equilibrium in the filament. This is the reason why current-voltage characteristic registered at electric current increase do not coincide with characteristic registered at electric current decrease.

Role of Na-K-2Cl cotransporter-1 in gastric secretion of nonacidic fluid and pepsinogen

Na-K-2Cl cotransporter-1 (NKCC) has been detected at exceptionally high levels in the gastric mucosa of several species, prompting speculation that it plays important roles in gastric secretion. To investigate this possibility, we 1) immunolocalized NKCC protein in the mouse gastric mucosa, 2) compared the volume and composition of gastric fluid from NKCC-deficient mice and their normal littermates, and 3) measured acid secretion and electrogenic ion transport by chambered mouse gastric mucosa. NKCC was localized to the basolateral margin of parietal cells, mucous neck cells, and antral base cells. In NKCC-deficient mice, gastric secretions of Na+, K+, Cl-, fluid, and pepsinogen were markedly impaired, whereas secretion of acid was normal. After stimulation with forskolin or 8-bromo-cAMP, chambered corpus mucosa vigorously secreted acid, and this was accompanied by an increase in transmucosal electrical current. Inhibition of NKCC with bumetanide reduced current to resting levels but had no effect on acid output. Although prominent pathways for basolateral Cl- uptake (NKCC) and apical Cl- exit [cystic fibrosis transmembrane conductance regulator (CFTR)] were found in antral base cells, no impairment in gastric secretion was detected in CFTR-deficient mice. Our results establish that NKCC contributes importantly to secretions of Na+, K+, Cl-, fluid, and pepsinogen by the gastric mucosa through a process that is electrogenic in character and independent of acid secretion. The probable source of the NKCC-dependent nonacidic electrogenic fluid secretion is the parietal cell. The observed dependence of pepsinogen secretion on NKCC supports the concept that a nonacidic secretory stream elaborated from parietal cells facilitates flushing of the proenzyme from the gastric gland lumen.

Ar 가스 압력과 RF 전력에 따른 유도결합형 플라즈마의 전기적 및 광학적 특성

In this paper, the electrical and emission properties of electrodeless fluorescent lamp were discussed using the inductively coupled plasma (ICP) with the variation of argon gas pressure and RF power. The RF output was applied to the antenna in the range of 5∼50 W at 13.56 MHz. The internal plasma voltage of the chamber and the probe current were measured while varying the supply voltage to the Langmuir probe in the range of －100V∼＋100V. When the pressure of argon gas was increased, electric current was decreased. There was a significant electric current increase from 10 to 30 W. Also, when the RF power was increased, electron density was increased. Also, the emission spectrum, Ar- I lins, luminance were investigated. At this time, the input parameter for ICP RF plasma, Ar gas pressure and RF power were applied in the range of 10∼60 mTorr, 10∼300 W, respectively. This implies that this method can be used to find an optimal RF power for efficient light illumination in an electrodeless fluorescent lamp.

STUDIES ON THE PROCESS OF NITRATES CONTENT DECREASING IN SIMULATED SOLUTIONS DURING ELECTROCHEMICAL TREATMENT

We have studied the process of electrochemical reduction of nitrates that was observed during the treatment of simulated solutions and of natural waters within the cell with soluble aluminum anodes, depending on the initial concentration of the nitrates, the quantity of electricity, the intensity of the electrical current and the value of pH. It has been established that during the electrochemical treatment of the simulated solution that contain nitrates: the concentration of the nitrates from the cell with soluble anodes of aluminum reduces, if the quantity of electricity increases. The effect of the nitrates reduction is almost the same, at the intensity of 1A and 3A, but the time of treatment is different. The time of treatment decreases when the intensity of the electrical current increases (while the quantity of electricity is the same). Based on the obtained result, we calculated the rate constant of the reduction reaction the half time and the total time of treatment of the simulated solutions up to the admitted residual concentration, foreseen for the nitrates of the drinking water. It has been fount that the total time for the reduction depends on the initial concentration of the nitrates and this very time increases together with the initial concentration, but the specific expenses of energy used to remove 1g of nitrates decreases. It was established that the effect of reduction of the nitrates at the electrochemical treatment of the simulated solutions and the natural waters greatly depends on the value of pH. When the value of the pH decreases, the above-mentioned effect increases up to 60%. In order to achieve the experiment, it is recommended that the initial value of the waters subdued to the electrochemical treatment should be between 3,75 4,00 units of pH.

Piezoelectric effect of hardened cement paste

Abstract The piezoelectric effect of hardened cement paste was studied in this paper. As compressive stress was applied on the specimen, an electrical current was observed. The electrical current increases nonlinearly with compressive stress. The average sensitivity constant reached is 1.0 × 10 −8 A/MPa. Through investigation of the variation of piezoelectric effect with absorbed water content in specimens, the mechanism of this phenomenon was analyzed. Piezoelectric effect of hardened cement paste is related to the transportation of mobile ions along with water in the hydrated cement product under stress.

Use of plasma polymerized highly hydrophobic hexamethyldissilazane (HMDS) films for sensor development

Hexamethyldissilazane (HMDS) plasma polymerized films can be used in a wide variety of applications due to the facility on plasma polymerization of HMDS molecule and the high resistance to acid or basic corrosion of the formed film. Nonetheless, the hydrophobic character, as well as the possibility of adsorption of organic molecules, did not receive attention yet. In this work HMDS plasma polymerized films, presenting high organic character, were obtained in order to analyze their properties as sensors for organic compounds in N 2 and aqueous solutions. The films showed to be not only highly resistant to corrosion in a wide scan of pH, but also presented high water contact angle (approximately 90°). The organic character of the films leads to a high adsorption characteristic for polar and non-polar compounds. The water contact angle measurements vary for 2-propanol aqueous solutions from 90° (0% of 2-propanol) to about 0° (50% of 2-propanol). When HMDS films were deposited on two different substrates, dielectric and porous silicon (PS), two main issues were found. The films suffered degradation by heating and porous silicon was planarized by the plasma deposition, as shown by infrared spectroscopy, optical and Raman microscopy. Deposition on piezoelectric quartz crystal (PQC) showed adsorption of polar and non-polar organic compounds carried by N 2 and chloroform aqueous solutions. HMDS films deposited on silicon were electrically characterized showing quickly and reversible response for 2-propanol carried by N 2. In saturated environment, the electrical current increases about five times when a range of −5 to 0 V was applied. For n-hexane drops, no reversible electrical characteristics were found. Although some issues were revealed, HMDS highly hydrophobic films showed promising characteristics for sensor development.

Back‐Extraction of Carboxylic Acids by Two‐Phase Electrophoresis

In this work, two‐phase electrophoresis as a more highly effective back‐extraction method was studied. With 33% TOA in n‐hexanol as organic solvent, citric acid and succinic acid can be back‐extracted to the aqueous phase by two‐phase electrophoresis. Compared with the traditional back‐extraction ways, there is no phase mixing, phase separation, or other chemicals requirement. So, the process can be called an environmentally friendly process. Some influence factors, such as the distance between the electrode to the interface, time, initial concentration, and electric current density, are discussed. Our experimental results show that the distance from the upper electrode to the interface has little influence on the mass transfer performance. Hence, it is better to keep the distance as low as possible, but the interface cannot be destroyed. The overall mass transfer quantity increases but the electric current efficiency decreases with an increase in the time. A higher electric current density gives better mass transfer performance. With the initial concentration increasing, both the overall mass transfer quantity and electric current efficiency increase. For the acids with lower distribution coefficient at normal conditions, a much higher back‐extraction ratio can be reached.

P-type semiconducting properties in lithium-doped MgO single crystals

The phenomenally large enhancement in conductivity observed when Li-doped MgO crystals are oxidized at elevated temperatures was investigated by dc and ac electrical measurements in the temperature interval 250-673 K. The concentration of ([Li]^{0}) centers (Li^{+} ions each with a trapped hole) resulting from oxidation was monitored by optical absorption measurements. Both dc and ac experiments provide consistent values for the bulk resistance. The electricalconductivity of oxidized MgO:Li crystals increases linearly with the concentration of ([Li]^{0}) centers. The conductivity is thermally activated with an activation energy of (0.70 +/- 0.01) eV, which is independent of the ([Li]^{0}) content. The \textit{standard semiconducting} mechanism satisfactorily explains these results. Free holes are the main contribution to band conduction as they are trapped at or released from the ([Li]^{0})-acceptor centers. In as-grown MgO:Li crystals, electrical current increases dramatically with time due to the formation of ([Li]^{0}) centers. The activation energy values between 1.3 and 0.7 eV are likely a combination of the activation energy for the creation of ([Li]^{0}) centers and the activation energy of ionization of these centers. Destruction of ([Li]^{0}) centers can be induced in oxidized crystals by application of an electric field due to Joule heating up to temperatures at which ([Li]^{0}) centers are not stable.

Effect of Electrode Morphology on the Behaviour of Electrorheological Fluids in Torsional Flow

In this study, we report experiments on experimental and commercial electrorheological (ER)-fluids in torsional flow. A torsional flow device (clutch) suitable for ER-fluids was designed and constructed. The flow curves measured with this device were compared with flow curves from a conventional rotational viscometer (a concentric-cylinders system). The agreement between the two devices was encouraging. To study the influence of inhomogeneous flow conditions besides the influence of the inhomogeneity of the electric field on the behaviour of an ER-fluid in a clutch mechanism, a set of smooth plates and three further sets of plates with different surface finishes were used in this investigation. Relative to the smooth plates, an increase in the relative ER-effect resulted from both ER-fluids used, when the oblique plates were used in an AC-and DC-field. This improvement in ER-effect seems to be tied to the increase in local field strength at the thick rim of the oblique plate. The addition of metal sheets to the smooth plates of the clutch provided a small increase in ER-effect under AC conditions. But in DC-field, the increase in ER-effect relative to that for smooth plates was rather pronounced, but so was the increase in electric current.

The role of electroosmotic flow in transdermal iontophoresis

Iontophoresis enhances transdermal drug delivery by three mechanisms: (a) the ion-electric field interaction provides an additional force which drives ions through the skin; (b) flow of electric current increases permeability of skin; and (c) electroosmosis produces bulk motion of the solvent itself that carries ions or neutral species, with the solvent ‘stream’. The relative importance of electroosmotic flow is the subject of this review. Experimental observations and theoretical concepts are reviewed to clarify the nature of electroosmotic flow and to define the conditions under which electroosmotic flow is an important effect in transdermal iontophoresis. Electroosmotic flow is bulk fluid flow which occurs when a voltage difference is imposed across a charged membrane. Electroosmotic flow occurs in a wide variety of membranes, is always in the same direction as flow of counterions and may either assist or hinder drug transport. Since both human skin and hairless mouse skin are negatively charged above about pH 4, counterions are positive ions and electroosmotic flow occurs from anode to cathode. Thus, anodic delivery is assisted by electroosmosis, but cathodic delivery is retarded. Water carried by ions as ‘hydration water’ does not contribute significantly to electroosmotic flow. Rather electroosmotic flow is caused by an electrical volume force acting on the mobile counterions. The simple ‘limiting law’ theory commonly given in textbooks and some research articles is a very poor approximation for transdermal systems. However, several extensions of the limiting law are compatible with each other and with the available experimental data. One of these theories, the Manning theory, has been incorporated into a theory for the effect of electroosmotic flow on iontophoresis, the latter theory being in good agreement with experiment. Both theory and experimental data indicate that electroosmotic flow increases in importance as the size of the drug ion increases. The ‘ionic’ or Nernst–Planck effect is the largest contributor to flux enhancement for small ions. Increased skin permeability or the skin ‘damage effect’, is a significant factor for both large and small ions, particularly for experiments at high current density. For monovalent ions with Stokes radii larger than about 1 nm, electroosmotic flow is the dominant flow mechanism. Because of electroosmotic flow, transdermal delivery of a large anion (or negatively charged protein) from the anode compartment can be more effective than delivery from the cathode compartment.

Weak-Localization Analysis for the Upper-Hubbard Transport in Si:Sb

Magnetoresistance (MR) in Si:Sb just below the critical concentration of metal–insulator transition has been carried out as stepping foot into the non-ohmic region of the electric current density. In the ohmic region, the resistivity at low temperatures obeys Efros-Shklovskii type variable-range hopping and the positive MR is observed. As the electric current density increases, the positive MR is depressed and then the negative one appears. This behavior has been explained by the transfer of electrons, due to the rise of the electron temperature, from the strongly localized states to the upper Hubbard band whose state is assumed to be the weakly localized one.