Voltage Application Method Research Articles

Room temperature-produced chalcogenide superlattices for interfacial phase-change memory

Phase-change memory (PCM) using chalcogenide films composed of Ge–Sb–Te alloys is the only commercially available nonvolatile memory for storage class memory. Recently, superlattice films of GeTe and Sb2Te3, called interfacial PCM (iPCM), have attracted attention for further increasing the switching speed and reducing energy consumption. It has been reported that the iPCM device exhibits both unipolar- and bipolar-type resistive switching depending on the method of voltage application, and research is being conducted to advance its applications. However, all iPCMs reported thus far have been formed at high temperatures beyond the crystallization temperatures of GeTe and Sb2Te3 using vacuum chambers equipped with a heating stage, making mass production and practical application difficult. Here, we report on fabricated superlattice composed of S-doped GeTe and Sb2Te3 layers by combining room temperature deposition with subsequent two-step annealing. Upon evaluating the performance of this superlattice film as a bipolar-type iPCM, it was found to exhibit characteristics comparable to those of bipolar-type iPCM fabricated from high-temperature deposited superlattices. This technology is expected to contribute to an increase in the throughput of iPCM device manufacturing.

Electrokinetic focusing of SARS-CoV-2 spike protein via ion concentration polarization in a paper-based lateral flow assay.

The COVID-19 pandemic highlighted the importance of designing sensitive and selective point-of-care (POC) diagnostic sensors for early and rapid detection of infection. Paper-based lateral flow assays (LFAs) are easy to use, inexpensive, and rapid, but they lack sensitivity. Preconcentration techniques can improve the sensitivity of LFAs by increasing the local concentration of the analyte before detection. Here, ion concentration polarization (ICP) is used to focus the analyte, SARS-CoV-2 Spike protein (S-protein), directly over a test line composed of angiotensin converting enzyme 2 (ACE2) capture probes. ICP is the enrichment and depletion of electrolyte ions at opposing ends of an ion-selective membrane under a voltage bias. The ion depleted zone (IDZ) establishes a steep gradient in electric field strength along its boundary. Enrichment of charged species (such as a biomolecule analyte) occurs at an axial location along this electric field gradient in the presence of a fluid flow that counteracts migration of those species - a phenomenon called ICP focusing. In this paper, running buffer composition and pretreatment solutions for ICP focusing in a paper-based LFA are evaluated, and the method of voltage application for ICP-enrichment is optimized. With a power consumption of 1.8 mW, S-protein is concentrated by a factor of 21-fold, leading to a 2.9-fold increase in the signal from the LFA compared to a LFA without ICP-enrichment. The described ICP-enhanced LFA is significant because the preconcentration strategy is amenable to POC applications and can be applied to existing LFAs for improvement in sensitivity.

Numerical and experimental studies on the effectiveness of time-varying electromagnetic fields in reducing electron density

When an aircraft or a hypersonic vehicle re-enters the atmosphere, the plasma sheath generated can severely attenuate electromagnetic wave signals, causing the problem of communication blackout. A new method based on time-varying E × B fields is proposed to improve on the existing static E × B fields and mitigate the radio blackout problem. The use of the existing method is limited by the invalid electron density reduction resulting from current density j = 0 A m−2 in plasma beyond the Debye radius. The most remarkable feature is the introduction of a time-varying electric field to increase the current density in the plasma to overcome the Debye shielding effect on static electric field. Meanwhile, a magnetic field with the same frequency and phase as the electric field is applied to ensure that the electromagnetic force is always acting on the plasma in one direction. In order to investigate the effect of time-varying E × B fields on the plasma electron density distribution, two directions of voltage application are considered in numerical simulation. The simulation results indicate that different voltage application methods generate electromagnetic forces in different directions in the plasma, resulting in repulsion and vortex effects in the plasma. A comparison of the vortex effect and repulsion effect reveals that the vortex effect is better at reducing the electron density. The local plasma electron density can be reduced by more than 80% through the vortex effect, and the dimensions of the area of reduced electron density reach approximately 6 cm × 4 cm, meeting the requirements of electromagnetic wave propagation. Besides, the vortex effect of reducing the electron density in RAM-C (radio attenuation measurements for the study of communication blackout) reentry at an altitude of 40 km is analyzed. On the basis of the simulation results, an experiment based on a rectangular-window discharge device is proposed to demonstrate the effectiveness of the vortex effect. Experimental results show that time-varying E × B fields can reduce the electron density in plasma of 3 cm thickness by 80% at B = 0.07 T and U 0 = 1000 V. The investigations confirm the effectiveness of the proposed method in terms of reducing the required strength of the magnetic field and overcoming the Debye shielding effect. Additionally, the method is expected to provide a new way to apply a magnetic window in engineering applications.

Examining Microdroplet Characteristics of Electrospray Electric Precipitation for Direct and Indirect Voltage Application Methods

Dust and fine dust exist in various forms and can lead to various problems such as dust explosion and air pollution. To reduce them, recently, research on electrospray electric precipitation, among various dust collection methods, has been actively conducted. In this study, comparative analysis experiments were performed on microdroplet generation characteristics for direct and indirect charging methods of electrospray electric precipitation. A visualization device was fabricated to generate microdroplets, and microdroplets were photographed with a high-magnification camera according to each charging method. The size and number of microdroplets were then analyzed via ImageJ software.

Suppression of decay time in transient drain current of back-gated GaN HEMT under UV exposure

Photodetectors based on an AlGaN/GaN high electron mobility transistor on Si have a long decay time after removal of light irradiation because of the large number of defects. This behavior is unsuitable for applications that require fast response. In several papers, though decay time was suppressed by thermal heating, it has problems such as fabrication complexity and power consumption. In this paper, we propose a substrate voltage (V sub) application method for suppressing decay time, which modulates the V sub immediately after the removal of UV irradiation, which promotes injecting electrons from two-dimensional electron gas to the carbon-doped GaN (C-GaN) layer. The decay time was suppressed from 75 to 2 s. Moreover, the effectiveness of reset voltage application is confirmed by a demonstration that changes the UV intensity continuously.

Investigation of specimen size, geometry and temperature effects on resistivity of electrically conductive concretes

In ECON research, it is important to determine a suitable size-geometry of specimen for resistivity measurement. In this study, specimens of three different geometries (cube, cylinder and prismatic) were produced in three different sizes using a mixture of normal concrete and ECON. In the ECON mixture, 0.8 vol% carbon fiber was used as conductivity increasing additive and carboxymethyl cellulose was used as fiber distributor agent. Resistivity (ρ) values were obtained once by applying different voltages and once directly measuring resistance (R) by ohm meters. It has shown that the resistivity values decrease with increasing voltage, according to the results obtained by the voltage application method, for both normal and ECON samples. In ECON specimens, it has been specified that the resistivity value increases with increasing cross section area (A)/length (L) ratio. Since the A/L ratios among the cylinder specimens were lower than the others, the resistivity difference of these samples was less. To determine the temperature-resistivity relationship in ECONs, the resistivity of 10 cm diameter, 20 cm long cylinder specimen was examined between −10 and room temperature. According to the results of temperature-resistivity relationship research, as the temperature increased from −10 °C to about 15 °C, the resistivity decreased, then the resistivity was fixed with increasing temperature.

Driving method for liquid crystal lens to increase focus range

A new method of voltage application is proposed to increase the focus range of a liquid crystal lens driven by two voltages. It is possible for the optical power of the liquid crystal lens to change in a wider range, while the root mean square aberration of low level is maintained. The liquid crystal lens is driven by a frequency of the voltages different in positive and negative lens states to obtain its largest optical power in each state. An obvious increase in focus range is realised.

Ammonium removal and recovery from real digestate wastewater by a modified operational method of membrane capacitive deionization unit

In this study, an extensive examination of ammonium removal and recovery from highly concentrated digestate wastewater was systematically performed. The treatability and ammonium recovery potential of the real digestate wastewater was assessed by enhanced Flowed Channel Membrane Capacitive Deionization (fcMCDI), which was introduced in our previous study. The fcMCDI cell was found efficient to remove ammonium ions from a synthetic mixture of glucose and Ca2+and Na+ ions, which are the major components of the anaerobic digestate liquid. Specific ammonium removal performance of the system was investigated in the presence of other ions. In a single cycle experiment, the process was able to remove the Mg2+, Ca2+, K+ and NH4+ ions from real digestate wastewater at percentages of 90.4%, 85%, 67.9% and 54.4%, respectively. A comparison of the conventional MCDI operation with an increased voltage application method with the fcMCDI cell was presented. Ammonium was successfully recovered in the form of ammonia gas by increasing the cell's working voltage, and simultaneous deionization of the other ions in the digestate wastewater was achieved. The obtained ammonium removal efficiencies were 89% and 67% with synthetic and real digestate wastewater, respectively. The results demonstrated that the enhanced MCDI technology holds a great potential to be an energy-efficient process for ammonium removal and recovery while also removing other contaminants effectively from highly concentrated wastewater sources.

The Dielectric Strength of Nomex 410 Paper in Liquid Nitrogen Under Boiling Situations

It is crucial for the successful application of high-temperature superconducting (HTS) power transformers that they are able to survive under abnormal operations, such as a short-circuit fault. Modeling, based on the design of a four-winding three-phase HTS power transformer, suggests severe boiling will occur on the surface of the winding during a short-circuit fault and will jeopardize the turn-to-turn insulation of the HTS power transformer. In this paper, a turn-to-turn insulation breakdown experiment platform involving the introduction of boiling on the surface of electrode has been built. Nomex 410 paper, one of the candidates for turn-to-turn insulation in the design of the HTS power transformer, was tested. The characteristics of dielectric strength of Nomex 410 in three different thicknesses (0.13, 0.18, and 0.25 mm) have been investigated, without boiling, as well as under different boiling situations, in an open bath of liquid nitrogen. The voltage application methods applied during both experiments test the electrical breakdown of Nomex 410 under a dynamic situation. The experiment results show that when under film boiling, compared to the test results for nucleate boiling, the dielectric strength of Nomex 410 paper decreases by approximately 38% of the value when no boiling is involved. Moreover, it is verified that the presence of an electric field accelerates the heat transfer between the liquid nitrogen and the heated electrode.

Development of time- and cost-effective pollution test methods applicable for different station insulation options

The Rapid Flashover pollution test method (RFO) exposes energized polluted insulators to fog and uses step changes of voltage to identify a minimum flashover voltage. The RFO method reduces test time by a factor of three or more compared to up-and-down voltage application method and is thus time- and cost-effective. In this paper the results from RFO on five ceramic and composite station insulators (line, post and hollow) with median 4.7 m leakage distance are compared closely with duplicate tests using up-anddown procedure. The tests on hydrophobic composite insulators used the preconditioning principles from CIGRE Brochure 555. Full-scale withstand testing of the same five but 420-kV class voltage insulators with median leakage distance 13.3 m are also presented. It is indicated that the flashover test results of RTV-coated station insulators should be specially analyzed and treated.

Homogeneous Field Intensity Control During Multi-Needle Electrospinning via Finite Element Analysis and Simulation

In the current study, finite element analysis is employed to simulate the process control of multi-needle electrospinning, by manipulating needle length, needle spacing, plastic casing of needle, and the way the voltage is applied to the needles, to facilitate the efficient production of homogeneous nanofibrous webs at high performance versus cost. The simulation results indicate that it is possible to control the field intensity homogeneity of multi-needle electrospinning process in terms of the vector sum of electric field intensity by adjusting the needle length, needle spacing, changing voltage application method and separating each needle with a plastic casing, etc. Measures such as capping each needle with a plastic casing, applying voltage directly to the needles, shortening the probed length of the needles at the edge sides, and reducing the distance between edge needles, as well as imparting additional voltage to the needles in the middle of the row could significantly decrease the field intensity of edge needles and thus improve the field intensity of the needles across one row and increase the potential of industrializing the needle type electrospinning technology.

PIC simulation of N 2 and C 2H 2 plasma behavior around plural objects

The plasma behavior around multiple objects has been simulated for the case of plasma immersion ion implantation (PIII) using the particle-in-cell module of the software “PEGASUS”. Simulations were performed for three types of negative pulse voltage application methods to the objects: (A) a single negative voltage pulse, (B) a negative voltage pulse after a negative voltage pulse, (C) a negative voltage pulse after a positive voltage pulse. The chamber wall was grounded. A cylindrical coordinate system was used. Effects of gas pressure and secondary electron emission by ion impact on the plasma (especially on the density and sheath shape) were studied. The gases were N 2 gas and C 2H 2 gas. The time evolution of the spatial distribution of densities of electrons, N 2 +ions, N 2⁎ radicals, and N atoms in the N 2 plasma, and C 2H 2 +, C 2H 2 2+, C 2H +, CH +, H +, C 2H 2, C 2H, CH 2, CH, H in the C 2H 2 gas plasma, was obtained. The time evolution of flux and energy distribution of electrons and ions at the object surface were also obtained. These results were compared for three types of pulsed voltage application methods, and it was concluded that the C-type was superior for obtaining conformal plasma at the objects.

New Method of Voltage Application for Improving Response Time of a Liquid Crystal Lens

ABSTRACT A new method of rapid driving of a liquid crystal lens is proposed. High external voltages are initially applied to the liquid crystal cell accompanied with an in-plane electric field. The occurring of disclination lines is prevented and the response of the lens becomes more than two times faster.

10 Tbit/inch2 Ferroelectric Data Storage with Offset Voltage Application Method

AbstractFerroelectrics are expected to become one of the next generation ultra-high density data storage media. The requirements for pulse amplitude and the duration to switch the domain were both markedly decreased by using a new domain stabilizing method; offset voltage application method. Additionally, with this method it became possible to invert a smaller domain with a diameter of less than 10 nm. Finally, significant progress was made regarding the memory density for ferroelectric data storage, and an area density of 10.1 Tera-bit/inch2 was successfully achieved. This represents the highest memory density for rewritable data storage reported to date.

Operation Simulation of an 8F21T2C-Type Ferroelectric Memory Array with a Revised Data Writing Method

A planar 1T2C-type ferroelectric memory cell structure which has a unit cell area of 8F2 (F: minimum feature length) has been proposed. In this structure, the gate area, which is covered with a floating gate electrode, is 3F in length and F in width. Through the SPICE simulation for a 2 × 2 cell array, the basic operation for 8F2 1T2C-type memory cell was identified. Also, data disturbance problem during the data writing process in the 1T2C-type ferroelectric memory array was investigated using an equivalent capacitor model. Based on the analysis, a modified V/3 rule voltage application method for reducing the data disturbance effect was proposed and its validity was verified by SPICE simulation.

Examination of theoretical models in external voltage control of capillary electrophoresis.

Control of electroosmosis by an external voltage in capillaries of varying geometry was examined and investigated. Controlled geometric factors included inner and outer radii, external electrode coverage area, and the method of voltage application. The behavior of the flow in response to the external voltage from earlier work and this study were compared to existing literature models. A noticeable lack of correlation between the current modeling theories and the published data is noted. In light of these results, suggestions for further areas of investigation of a description of external voltage flow control mechanism are suggested.

ELECTROSTATIC LEVITATION SYSTEM IN VACUUM CONDITION AIMING AT LINEAR BEARINGS

The authors are developing electrostatic levitation systems as a non-contact bearing to solve the problems that are caused by large friction force and rapid wear in high vacuum. This paper reports three experimental results that support good feasibility for practical application of electrostatic levitation in vacuum chambers. First, and aluminum disk that weighs 442g is experimentally levitated to confirm that electrostatic levitation force in vacuum is strong enough to levitate objects such as positioning tables and conveyer carriages. Secondly, to reduce the cost for amplifiers, which are essentially employed in the systems, a voltage application method that utilizes amplifiers, constant DC voltage suppliers and smooth input profile is introduced. This method successfully reduces output voltage range of amplifiers by a factor of about eighth. Thirdly, to apply electrostatic levitation technology to more practical systems such as conveyers, an electrostatic levitation system that constrains the whole motions of its levitated body except one axis of translational motion on horizontal plane.

Flashover performance of ice-covered insulators

The presence of ice on the surface of insulators is sometimes the cause of severe problems in power networks. In fact, the presence of ice reduces the electrical performance of insulators in ways that can, in some circumstances, lead to flashover, resulting in power outages. The maximum withstand voltage of ice-covered insulators is distinctly inferior to that of clean insulators. The electrical performance of insulators also depends on atmospheric conditions during the formation and development of ice deposits. Temperature liquid water content, wind speed, water droplet size, conductivity of precipitation, as well as the nature and strength of the electric field are major factors influencing the type, quantity and uniformity of ice. This paper gives an account of the research carried out on the electrical behaviour of ice-covered insulators, particularly in relation to laboratory ice simulation, voltage application methods and the major intervening factors. The paper also reports on the work being done in laboratories around the world, and highlights the results obtained at the High Voltage and Atmospheric Icing Laboratory of the University of Quebec in Chicoutimi (UQAC).

Comments on "Dielectric breakdown characteristics of cryogenic nitrogen gas above liquid nitrogen surface" [with reply

For the original article see ibid., vol. 1, no. 3, p. 538-43 (1994). In the commenter's experience, a needle electrode in mist, just over the surface of the liquid, collects liquid droplets especially under voltage stress, which cause the test results to be very variable. This situation has been found not only with liquid nitrogen, liquid hydrogen and especially liquid helium, but also in air close to the surface of a layer of oil. It is also noted that all the data in the original paper were taken as the voltage was rising at a rate of 0.5 kV/s, while during the commenter's tests the voltage was held steady for a long enough time to observe the liquid droplets collecting on the needle. It is surmised that whatever the true reason for the difference between data of Goshima et al. and the commenter's, the method of voltage application can have very significant effects, not only on the scatter but also on the mean. Finally, caution is suggested in the use of Styrofoam containers to hold cryogenic liquids for electrical tests, as an explosion is possible under certain conditions. In reply, the author clarifies the conditions under which the data were collected and agrees that the difference in the two sets of results may well arise from the voltage application method. In regards to the caution needed in the use of Styrofoam containers, the author states that he and his co-authors were already aware of this and acted accordingly.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

送電線用静電しゃへい線への電圧印加法

送電線用静電しゃへい線への電圧印加法