Improved Thomson Coefficient Measurements Using an AC Method

Compared to direct current (DC) methods, alternating current (AC) methods have rarely been used in the field of electrodermal research. AC methods, however, have the advantage of enabling analysis of electrodermal activity, including capacitive properties. To establish an easy AC method, a computer-controlled measurement system was developed in this study. The system can automatically measure impedances at three different frequencies on the basis of phase detection and determine an impedance locus. Performance tests using RC parallel circuits showed that the system has sufficient accuracy. Palmar skin impedance was also measured and temporal changes in parameters of the circular arc law were investigated. It was demonstrated that the system can obtain impedance data with a data acquisition time of less than 0.2 s and can easily determine an impedance locus. It is expected that the new system, due to its high level of accuracy and ease of operation, will be used as an AC method of measuring electrodermal activity.

An accurate and non-destructive evaluation method for the hydraulic measure impact range in coal seams is urgently needed. Aiming at the application demands, a theoretical study and field test are presented using the direct current (DC) method to evaluate the impact range of coal seam hydraulic measures. We firstly analyzed the law of the apparent resistivity response of an abnormal conductive zone in a coal seam, and then investigated the principle of non-destructive testing of the coal seam hydraulic measure impact range using the DC method, and used an accurate evaluation method based on the apparent resistivity cloud chart. Finally, taking hydraulic fracturing and hydraulic flushing as examples, field experiments were carried out in coal mines to evaluate the impact ranges. The results showed that: (1) in the process of hydraulic fracturing, coal conductivity was enhanced by high-pressure water in the coal seam, and after hydraulic fracturing, the boundary of the apparent resistivity decrease area was the boundary impact range. (2) In the process of hydraulic flushing, coal conductivity was reduced by holes and cracks in the coal seam, and after hydraulic flushing, the boundary of the apparent resistivity increase area was the boundary impact range. (3) After the implementation of the hydraulic measures, there may be some blind zones in the coal seam; in hydraulic fracturing blind zones, the apparent resistivity increased or stayed constant, while in hydraulic flushing blind zones, the apparent resistivity decreased or stayed constant. The DC method realized a comprehensive and non-destructive evaluation of the impact range of the hydraulic measures, and greatly reduced the time and cost of evaluation.

Recording electrodermal activity is a well-accepted physiological measurement for clinical approaches and research. Historically, applying a DC (direct current) signal to the skin to measure the conductance is the most common practice for exogenous recordings. However, this method can be subject to error due to electrode polarization even with "nonpolarizing" electrodes-a problem that can be eliminated with alternating current (AC) methodology. For that reason, Boucsein et al. () called for research demonstrating an AC method that is validated by comparison to standard DC methodology. Additionally, the complex structure of human skin has electrical properties that include both resistance and capacitance, and AC recording enables the measurement of skin susceptance (associated with current flow through capacitors). Finally, AC recording permits the simultaneous recording of the endogenous skin potential. In this paper, the results from a direct comparison between both methods are presented, which has not been reported previously. The results demonstrated excellent agreement between a 20 Hz AC method and a standard DC method, supporting the validity of the AC recording methodology employed. The results also showed that an applied voltage of 0.2 V is sufficient for DC recordings.

The present investigation has been carried out to determine the usefulness of direct current (DC) and alternating current (AC) electrochemical methods for corrosion monitoring of unlacquered and lacquered tinplate samples. Evaluation was performed with 5-(μm and 7-μm coatings of an epoxy-phenolic lacquer in citrate buffer solution, pH = 4. The steady-state corrosion conditions for these epoxy-phenolic lacquers were established after 8 to 10 days of accelerated corrosion at 37°C. Electrochemical impedance spectroscopy (EIS) was used to obtain Rp in the Stern-Geary equation. The data indicate that the corrosion rate in the cans is completely due to the tin dissolution process. For the electrolytes chosen for this study, the iron content of the solution was found to be very low. Icorr values were obtained by DC and AC methods and the results agreed well.

A simple and low-cost alternating current (AC)-based method, without electrolyte correction, is proposed (Electrochemical Impedance Spectroscopy (EIS)-Zero Gap Cell) for the determination of ohmic contribution of diaphragms. The effectiveness of the proposed methodology was evaluated by using a commercial Alkaline Water Electrolysis (AWE) diaphragm (Zirfon®). Furthermore, the results were compared with two conventional electrochemical methodologies for calculating the separator resistance, based on direct current (DC), and AC measurements, respectively. Compared with the previous techniques, the proposed approach reported more accurate and precise values of resistance for new and aged samples. Compared with the manufacturer reference, the obtained error values for new samples were 0.33%, 5.64%, and 41.7%, respectively for EIS-Zero gap cell, AC and DC methods, confirming the validity and convenience of the proposed technique.

Effects of alternating current iontophoresis on drug delivery

Percussion and electrical stunning of Atlantic salmon ( Salmo salar) after dewatering and subsequent effect on brain and heart activities

Development of a real-time AC/DC data acquisition technique for studies of AC corrosion of pipelines

For several decades, electromagnetic brain stimulation for clinical applications has been investigated mainly with invasive techniques, such as deep brain stimulation (DBS), and this has limited its applicability. recent research has focused on transcranial magnetic stimulation (TMS) or electric current stimulation using direct current (DC), alternating current (AC), or more general current stimulation methods [i.e., generalized transcranial current stimulation (tCS)]. To explore the possibilities and limitations of these approaches, for a state-of-the-art assessment and looking into the future, we called for papers in the field and asked the authors to present new experimental and clinical findings on noninvasive transcranial electromagnetic brain stimulation. The submitted papers were subjected to a rigorous peer-review process, according to the IEEE Transactions on Neural Systems and Rehabilitation Engineering (TNSRE) guidelines, and the accepted papers form this special issue of TNSRE. After a general introductory article on the current state-of-the-art in the use of biophysical models and related technologies in tCS, the remaining articles are arranged in three main categories of topics: (1) specific modeling approaches for the study of noninvasive electromagnetic brain stimulation (2) techniques proposed for efficacy and reliability in transcranial magnetic stimulation (TMS) applications; and (3) specific applications of tCS and TMS in epilepsy, depression and brain-computer interfaces (BCI). We believe that this special issue, despite the relatively small number of papers, is a testament to the potential and promise that noninvasive electromagnetic brain stimulation presents for clinical and other applications. One may further comment that this issue reflects the promise of neuroengineering in general for effective applications in biomedicine.

With the expansion of today's digital era, the use of electronic equipment is increasing exponentially at home, office, and plants. The common denominator of these electronic equipment is that they all use Direct current (DC) power internally by converting Alternating Current (AC) power to DC power using local converters. All these converters produce losses, heat, and are prone to failures which in turn impact the equipment efficiency, life span, and reliability. In addition, these converters increase the cost of equipment they are powering and their required footprint. The issue of reliability and cost reduction is more stressing for data centers where servers, Uninterruptable Power Supply (UPS) systems, and IT equipment constituting the majority of the load can be powered directly through a DC grid. This paper presents a case study that compares AC and DC technologies for powering a typical data center and outlines the main advantages and limitations of each technology. This study will present a comparative analysis of a DC power system against a typical AC distribution for critical datacenter loads. It also presents a real case study of existing AC powered data center and compare the benefits of powering the center via DC instead of AC. Analytical reliability, safety and efficiency models are developed, and quantitative results are obtained based on a set of real data. The study indicates that the DC system would be more reliable, efficient and will achieve less Capex and Opex values than the AC.

Bulk barium titanate (BaTiO3 ) ceramic specimens with bimodal microstructures are prepared and their dielectric and fatigue strengths are investigated under an alternating current (AC) electric field and a direct current (DC) electric field. It is found that under AC electrical loading, both the dielectric and fatigue strengths decrease with increasing amount of coarse abnormal grains. The scatter of the AC fatigue strength is characterized with the Weibull statistics. The extent of scatter of the AC fatigue strength data correlates strongly with the size distribution of the coarse grains. Such correlation is resulted from the presence of intrinsic defects within the microstructure. For DC electrical loading, the time to failure of the specimens with coarse abnormal grains is significantly shorter than the lifetimes of the specimens with only small normal grains. It is found that under a DC electric field of 6 MVm−1, the BaTiO3 specimens would fail within 200 h when abnormal grains are present in the microstructure. However, the lifetimes of the specimens containing abnormal grains vary significantly from one to another. The Weibull statistical analysis indicates that the amount of abnormal grains has little influence on the lifetime performance of bulk BaTiO3 ceramics under large DC electric fields. In most of the failed BaTiO3 specimens under DC electrical loading, regardless of their lifetimes, large through-thickness round holes with recrystallization features are present. A mixed failure mode consisting of avalanche and thermal breakdowns is proposed for the failed specimens.

Electrical stunning is considered one of less stressful fish stunning method. However, for its efficiency, it is important to determine the best way of application of the electrical variables. The aim of this study was to evaluate the effect of different voltages (100, 150, and 200 V) of alternating current (AC) or direct current (DC), frequency of 50 Hz, for 180 s exposure, concerning the aspects of behavior and meat quality of pacu (Piaractus mesopotamicus). Fish subjected to AC remained unconscious longer, evaluated by behavior analysis, when compared to DC. The pacu subjected to 100 AC, 200 AC and 100 DC showed less bleeding in the fillets. The lightness (L*) of the fillets were higher in 150 AC, 150 DC and 100 DC, followed by 200 and 100 AC. The redness (a*) in pacu fillets were moderate in treatments 200 and 150 AC and less intense in treatments 100 DC and 100 AC. The yellowness (b*) was higher in fish fillets treatment 150 DC and lower in 100 AC. Therefore, the 200 V alternating current (AC) used in water stunning caused apparent unconsciousness of up to 4 min. after exposure and less bleeding in fillets, thus it is a suitable stunning method to be recommended for the pacu processing industry.

Increasing electronic appliances in residential buildings have caused researchers to study direct current (DC) powered systems in homes. In this paper, we state a scenario that a home with traditional alternating current (AC) powered appliances are replaced with DC devices. The questions which devices can be replaced, how much savings in terms of energy and electric bill is provided, what are economical, technical, social and environmental problems in this AC-DC transition and which system between DC and AC for residential buildings are much preferable based on the AHP method are answered in the presented study. Results show that 74.126-percentage cost saving in the electric bill is provided. However, the problems that nonexistence in some residential DC devices in the market, immaturity of DC system in terms of technical issue, added system costs, less information about DC by experts and related people, and a public bias that DC is unsafe to exist. In this study, based on these defined advantages and disadvantages of DC and AC system, criteria and sub-criteria have been determined for the analytic hierarchy process (AHP) method. By way of AHP, the result that DC system is much preferable than the AC system for residential buildings has been reached.KeywordsDirect currentAlternating currentAnalytic hierarchy process

A series of ethylene–octene copolymer (EOC) composites have been prepared by melt‐mixing with different weight ratios of expandable graphite filler (0–50% by weight). Electrical conductivity [both alternating current (AC) and direct current (DC)] and thermal conductivity studies were carried out. Effect of filler loading and frequency on electrical conductivity was studied. DC conductivity has increased from 1.51 × 10 −13 S cm −1 to 1.17 × 10 −1 S cm −1 . Percolation threshold by DC and also AC methods was observed at about 16 vol% of the filler. Real part of permittivity was found to be decreasing with increase in frequency while conductivity was increasing. Thermal conductivity was also found to be increasing gradually from 0.196 to 0.676 Wm −1 K −1 which is about 245% increase. Graphite not only increases the electrical and thermal conductivities but at and above 40 wt%, also acts as a halogen‐free, environmental friendly flame retardant. Shore‐A hardness of EOC/graphite composites shows that even with high graphite loading, the hardness is increased from about 50–68 only so that the rubbery nature of the composite is not affected very much. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Direct Current (DC) and Pulse current (PC) methods were used to get nanocrystalline Ni-ZrO2 composites from tri-ammonium citrate bath. In the electrocomposite formation, the ZrO2 particles were transported to the surface by mechanical action and got entrapped in the nickel matrix. Incorporation of ZrO2 in the nickel matrix was found to increase with current densities when DC was employed. Beyond 2 A/dm2, their incorporation became saturated when PC was used. PC method offered better electrocomposites than DC method producing finer grains and uniform surface. Scanning electron micrographs (SEM) reveals that smaller grains and uniform distribution of Zirconia particles in the nickel matrix. The increased hardness of Ni-ZrO2 electrocomposite coatings is due to incorporation of ZrO2 particles in the nickel matrix and also changes in grain size. Incorporation of ZrO2 particles in Ni-matrix favoured the enhanced microhardness and corrosion resistance of the deposit.