Alternating Current Power Source Research Articles

Improving Degradation Efficiency of Organic Pollutants through a Self-Powered Alternating Current Electrocoagulation System.

Although electrocoagulation technology has been widely researched in wastewater treatment, high energy consumption and electrode passivation are still the main challenges for its widespread applications. Here, we propose a self-powered electrocoagulation system based on a triboelectric nanogenerator (TENG) with alternating current (AC) outputs to solve these two issues, and thus enhance the removal efficiency of organic pollutants. Compared with the direct current source, the AC power source can reduce the electrode passivation, produce more aluminum hydroxide compounds after consuming an equal amount of charges, and thus improve the degradation efficiency. Moreover, the removal efficiency can be further enhanced by decreasing the frequency AC, in which a 5.7-fold improvement was achieved at 0.2 Hz compared to DC at 1.8 Hz. Inspired by the low frequency of ocean wave water, we developed a self-powered AC-electrocoagulation system to directly drive the electrocoagulation reaction by harvesting water wave energy, which can effectively remove 94.8% of xylenol orange and 98.8% of water-oil emulsion, and thus completely address the problem of energy consumption. This study further promotes the application of self-powered electrochemical systems in treating environmental pollution.

Systematic approach and mathematical development for conditional core damage probabilities under station blackout of a nuclear power plant

Station blackout (SBO), a total loss of alternating current (AC) power, is considered to contribute significantly to nuclear power plant risk. The analysis of SBO risk is complicated due to time-dependent interactions among events. Simplifying assumptions that are currently used extensively in probabilistic safety assessment may lead to an overly conservative estimation of SBO risk, which may distort the overall plant risk profile and the associated accident management strategy. To calculate more accurate SBO risk, this study first identified SBO sequences and the associated time-dependent interactions by differentiating fail-to-start and fail-to-run failures of alternative AC power source and turbine-driven pumps. Mathematical formulas were developed to calculate the conditional core damage probabilities corresponding to the identified SBO sequences. These mathematical formulas were verified via a Monte Carlo simulation. This study is expected to contribute to the development of an integrated framework for SBO risk analysis that includes all possible SBO sequences, related events, and their time-dependent interactions.

수중 방전 플라즈마를 이용한 탄소나노소재 합성 시 흑연전극의 형상과 조합의 영향

We investigated the effect of graphite electrode geometry and combination on nanocarbon material synthesis using underwater discharge plasma(UDP). The UDP system consists of two graphite electrodes and beaker filled with de-ionized water. A high voltage of 15 kV with a frequency of 25 kHz is applied to produce UDP using an alternating-current power source. The UDP system with conical electrodes produced the largest amount of products due to the concentration of electrical fields between electrodes. In addition, hollow-shaped stationary electrode and conical-shaped moving electrode stores discharge-induced bubbles and maintains longer reaction time. We found from Raman spectroscopy and electron microscopy that high quality carbon nanomaterials including carbon nanotubes are synthesized by the UDP system.

An MRI-Compatible High Frequency AC Resistive Heating System for Homeothermic Maintenance in Small Animals.

PurposeTo develop an MRI-compatible resistive heater, using high frequency alternating current (AC), for temperature maintenance of anaesthetised animals.Materials and MethodsAn MRI-compatible resistive electrical heater was formed from narrow gauge wire connected to a high frequency (10–100 kHz) AC power source. Multiple gradient echo images covering a range of echo times, and pulse-acquire spectra were acquired with the wire heater powered using high frequency AC or DC power sources and without any current flowing in order to assess the sensitivity of the MRI acquisitions to the presence of current flow through the heater wire. The efficacy of temperature maintenance using the AC heater was assessed by measuring rectal temperature immediately following induction of general anaesthesia for a period of 30 minutes in three different mice.ResultsImages and spectra acquired in the presence and absence of 50–100 kHz AC through the wire heater were indistinguishable, whereas DC power created field shifts and lineshape distortions. Temperature lost during induction of anaesthesia was recovered within approximately 20 minutes and a stable temperature was reached as the mouse’s temperature approached the set target.ConclusionThe AC-powered wire heater maintains adequate heat input to the animal to maintain body temperature, and does not compromise image quality.

Ferritin-mixed solution plasma system yielding low-dimensional carbon nanomaterials and their application to flexible conductive paper

We demonstrate the production of low-dimensional carbon nanomaterials using a solution plasma system and their application to flexible conductive paper. The solution plasma system consists of two graphite electrodes and a beaker filled with ferritin-mixed deionized water. Ferritin molecules are used as the growth catalyst of the carbon nanomaterials. A high voltage of 15 kV at a frequency of 25 kHz is supplied to the electrodes using an alternating-current power source. The effects of the graphite rod diameters and the concentration of ferritin molecules are comparatively investigated. The produced carbon nanomaterials are characterized using Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. We confirmed the synthesis of graphitic platelets, onion-like structures, and carbon nanotubes. Finally, we fabricated flexible conductive papers using the produced materials with a good electrical conductance.

Alternating-Signal-Biased System Design and Demonstration for Visible Light Communication

In the literature, previous system designs are mainly focused on the use of direct-current light-emitting diodes (DC-LEDs) with fixed voltage bias. As alternating-current (AC)-LEDs are more energy efficient and becoming more and more popular, a driving system supporting AC-LEDs providing lighting and visible light communication (VLC) functions is highly desirable. This paper investigates the alternating-signal-biased system design for VLC, which combines the AC bias voltage signal and electrical data signal to modulate both DC- and AC-LEDs. In the experiment, a 40-LED array is modulated by our proposed system that makes use of current from AC power source while maintaining nondistorted message signal transmission. On-off-keying and quadrature-phase-shift-keying formats are used, and data rates of 60 and 120 kb/s are demonstrated, respectively. The threshold voltage effect and the system extension to support AC-LED are discussed. The alternating-signal-biased system design supporting both DC- and AC-LEDs is also discussed.

Design Concepts and Principle of Operation of the HeartWare Ventricular Assist System

Implantable left ventricular assist devices provide circulatory support for patients at risk of death from refractory, end-stage heart failure. Rotary blood pumps have been designed for increased reliability and smaller size for use in a broader population of patients than the first-generation pulsatile devices. The design concepts and principle of operation of the HeartWare System are discussed. The HeartWare Ventricular Assist System (HVAD) is a small centrifugal flow pump with a displacement volume of 50 ml and an output capacity of 10 L/min. A unique wide-blade impeller is suspended by hybrid passive magnets and hydrodynamic forces. An integrated inflow cannula is inserted into the left ventricle and is held in position by an adjustable sewing ring; the pump is positioned in the pericardial space. The 10-mm outflow graft is anastomosed to the ascending aorta. External system components include the microprocessor-based controller, a monitor, lithium-ion battery packs, alternating current and direct current power adapters, and a battery charger. Physiologic control algorithms are incorporated for safe operation. Preclinical life cycle tests have shown the HVAD to be highly reliable. This system design offers reliability, portability, and ease of use for ambulatory patients.

Formation of Aluminium Oxide Film on Al Substrate by Micro-Arc-Technoloy at Alternating-Current Power Source

The objective of this study was to form a crystalline oxide film on an aluminum substrate using micro-arc oxidation (MAO) processing at half-wave rectification current. A crystalline oxide film was able to be formed on an aluminum substrate using this method. It was found that the electrolytic aqueous solution selectivity, discharge condition, oxide film surface condition and reaction mechanism observed in MAO-processing at half-wave rectification current were different from those observed in MAO-processing using a direct current. The electrolytic aqueous solution selectivity range was small, and in many instances a small discharge appeared during MAO-processing at half-wave rectification current. Furthermore, the surface of the film was generally smooth and contained small pores. Combining both of the MAO-processing was possible, with the result that the condition of the film surface was significantly influenced by the second step MAO-processing.

Semiochemicals released by electrically stimulated red imported fire ants, Solenopsis invicta.

The red imported fire ant Solenopsis invicta Buren, has evolved sophisticated chemical communication systems that regulate the activities of the colony. Among these are recruitment pheromones that effectively attract and stimulate workers to follow a trail to food or alternative nesting sites. Alarm pheromones alert, activate, and attract workers to intruders or other disturbances. The attraction and accumulation of fire ant workers in electrical equipment may be explained by their release of pheromones that draw additional worker ants into the electrical contacts. We used chemical analysis and behavioral bioassays to investigate if semiochemicals were released by electrically shocked fire ants. Workers were subjected to a 120 V, alternating-current power source. In all cases, electrically stimulated workers released venom alkaloids as revealed by gas chromatography. We also demonstrated the release of alarm pheromones and recruitment pheromones that elicited attraction and orientation. Arrestant behavior was observed with the workers not electrically stimulated but near those that were, indicating release of unkown behavior-modifying substances from the electrically stimulated ants. It appears that fire ants respond to electrical stimulus by generally releasing exocrine gland products. The behaviors associated with these products support the hypothesis that the accumulation of fire ants in electrical equipment is the result of a foraging worker finding and closing electrical contacts, then releasing exocrine gland products that attract other workers to the site, who in turn are electrically stimulated.