Direct Current Frequency Research Articles

The Effect of Varied Time Interval and Micro-Current (Direct) on the Level of Biomarker (IL-6) and Rate of Tooth Movement: An Animal Study.

Exogenous application of direct current (DC) on piezoelectric biopolymers results in biochemical modifications in the intracellular/extracellular regions which profoundly affects the pace of bone turnover. A qualitative examination of DC (waveform and frequency) provides ideal qualities of current. 20 female Wistar rats (Rattus norvegicus) were randomly selected and divided into control (group 1-4 rats) with orthodontic appliance (OA) and experimental groups (OA + Micro-current (MC). Experimental groups were subdivided into four groups (group 2-20 μA/5 sec, 3-20 μA/10 sec, 4-15 μA/5 sec, 5-15 μA/10 sec with four rats in each). The tooth movement was recorded every 24th hours for 7 days. Gingival crevicular fluid (GCF) was collected 6 hr, 12 hr, 24 hr, 3rd day and 168 hrs with the absorbent paper points at specific location around the tooth in control and experiment groups. Histopathological analysis was done on 168 hrs to assess the osteoclastic activity around the root. Interleukin-6 (IL-6) concentration was accessed using enzyme-linked immunosorbent assay (ELISA). The data were subjected to one-way ANOVA and Tukey's posthoc test. There was a statistically significant difference in tooth movement, group 3 (20 μA/10 sec) showed an increased rate of tooth movement on the 168 hrs. The level of IL-6 was maximum on 72 hrs in experimental group 3. The study showed time interval/frequency, the waveform, and the amount of current play a significant role in determining bone turnover and rate of tooth movement.

Structure and electrochromic properties of WO3 thin films by direct current, pulsed direct current, and radio frequency magnetron sputtering from metallic and ceramic targets

The structure, morphology, and electrochromic properties of sputtered-WO3 thin films from ceramic and metallic targets were investigated. The films were produced using different types of power sources, namely, direct current (DC), pulsed DC, and radio frequency (RF) generators. Highly transparent as-deposited WO3 thin films grown at room temperature using each target changed to dark blue upon introduction of an electric field in electrolyte regardless of types of sputtering power. WO3 films obtained by sputtering the ceramic target using a pulsed DC power exhibited a large transmittance difference of 97.5% and high coloration efficiency of 55.2 cm2/C compared to the films using DC and RF powers, these films had higher response speeds and stable transmittance modulation after long-term cycle tests. WO3 thin films produced by sputtering a metallic tungsten target showed enhanced electrochromic performance when grown under DC power and a coloration efficiency of 69.1 cm2/C due to their porous microstructure. This article presents methods for the fabrication of low-cost and large-scale oxide electronic devices for various applications, such as electrochromic displays, that can be applied for mass production.

Modeling and simulation of DC and microwave characteristics of AlInN(AlGaN)/AlN/GaN MOSHEMTs with different gate lengths

AbstractIn this paper, direct current (DC) and microwave characteristics are modeled and analyzed for AlInN(AlGaN)/AlN/GaN metal‐oxide‐semiconductor high electron mobility transistors with different gate lengths. The 2‐dimensional electron gas sheet charge density (ns) model is developed by considering polarization effect and flat‐band voltage with lowest occupied energy level (E0) in the quantum well. The drain current, transconductance, and gate charge model is developed by incorporating approximation of ns as proposed in this paper. Then, the cut‐off frequency is calculated from the transconductance and gate capacitance model. The analytical model results are in good agreement with Technology Computer Aided Design simulation and experimental results from literatures for DC and microwave characteristics for the proposed gate lengths (0.1, 0.2, and 0.3 μm). From these characteristics, it is also observed that AlInN/AlN/GaN MOSHEMT shows superior DC and radio frequency performance as compared with AlGaN/AlN/GaN MOSHEMT. AlInN/AlN/GaN MOSHEMT produces high drain current (2.34 A/mm) and high cut‐off frequency (124 GHz) at smaller gate length.

Visualization of ionic wind in laminar jet flames

Electric field, when it is applied to hydrocarbon flames, generates ionic wind due to the electric body force on charge carrying species. Ionic wind has been shown to influence soot emission, propagation speed, and stability of flames; however, a detailed behavior of ionic wind and its effects on flames is still not clear. Here, we investigated the dynamic behaviors of flames and ionic wind in the presence of direct current (DC) and alternating current (AC) electric fields in nonpremixed and premixed jet flames with a jet nozzle placed between two parallel electrodes. We observed a skewed flame toward a lower potential electrode with DC and lower frequency AC (e.g., 10Hz) and a steady flame with higher frequencies AC (1000Hz), while we found that the ionic wind blew toward both the anode and cathode regardless of flame type (nonpremixed or premixed) or the source of the electric field (DC and AC).

Bond and electrochromic properties of WO3 films deposited with horizontal DC, pulsed DC, and RF sputtering

The purpose of this research was to investigate the bond and electrochromic properties of tungsten oxide (WO3) thin films deposited by three different plasmas sources: direct current (DC), pulsed DC and radio frequency (RF). The experimental results show that optical intensity increases with an increasing oxygen percentage and that all films have a 950cm−1 peak which results in a bond of W6+O in the Raman spectra. Hence, the oxygen percentage was changed from 0.3 to 0.7 to study the influence of coloring and bleaching as regards the different sputtering powers. Additionally, WO3 thin films show the best electrochromic properties as regards the oxygen/argon (O2/Ar) gas ratios of 0.7, 0.6 and 0.6 for DC, pulsed DC and RF sputtering, respectively. The transmittances of all films are over 75% as-deposited, and the deposition rates were between 0.8 and 0.1Ås−1. Simultaneously, the transmittance variations (ΔT) were 51%, 57% and 53% for DC, pulsed DC and RF sputtering at a wavelength of 550nm, respectively. The bleached/colored ability of the cyclic voltammograms (CVs) was pulsed DC>DC>RF. Since, the coloration ability of WO3 thin film deposited with plasma source of pulsed DC was better than those of the DC and RF.

Air Purifier Based on Sensorless DC Motor and Composite Photocatalyst Technique

This project is purposed to design an air purifier based on composite photocatalyst technique. Photocatalyst could work normally only in limited condition with ultraviolet light and light intensity strong enough. In order to overcome the deficiencies above, this project uses composite photocatalyst technique to improve purification efficiency of the air purifier. The composite photocatalyst technique comprehensively combines photocatalyst technique and traditional air purification technology. Moreover, the utilization of multi-thread algorithm has decreased the response time of this design to great extent. The brushless direct current motor without hall sensor charged by direct current frequency conversion technique decreases the noise of the air purifier, prolongs its life, and protects environment by saving energy.

A Wyner-Ziv Video Coding method utilizing mixture correlation noise model

In Wyner-Ziv (WZ) Distributed Video Coding (DVC), correlation noise model is often used to describe the error distribution between WZ frame and the side information. The accuracy of the model can influence the performance of the video coder directly. A mixture correlation noise model in Discrete Cosine Transform (DCT) domain for WZ video coding is established in this paper. Different correlation noise estimation method is used for direct current and alternating current coefficients. Parameter estimation method based on expectation maximization algorithm is used to estimate the Laplace distribution center of direct current frequency band and Mixture Laplace-Uniform Distribution Model (MLUDM) is established for alternating current coefficients. Experimental results suggest that the proposed mixture correlation noise model can describe the heavy tail and sudden change of the noise accurately at high rate and make significant improvement on the coding efficiency compared with the noise model presented by DIStributed COding for Video sERvices (DISCOVER).

IQ imbalance compensation scheme in the presence of frequency offset and dynamic DC offset for a direct conversion receiver

A direct conversion architecture reduces the cost and power consumption of a receiver. However, a direct conversion receiver may suffer from direct current (DC) offset, frequency offset, and IQ imbalance. This paper presents an IQ imbalance estimation scheme for orthogonal frequency division multiplexing (OFDM) direct conversion receivers. The proposed IQ imbalance estimation scheme operates in the presence of dynamic DC offset and frequency offset. The proposed scheme calculates IQ imbalance from a simple equation. It employs the knowledge of the preamble symbols of the IEEE 802.11 a/g standards, while it does not require the impulse response of the channel. Numerical results obtained through computer simulation show that the bit error rate (BER) performance for the proposed IQ imbalance estimation scheme has a degradation of about 4 dB with a large DC offset, frequency offset, and IQ imbalance.

IQ Imbalance Estimation Scheme in the Presence of DC Offset and Frequency Offset in the Frequency Domain

Direct conversion receivers in orthogonal frequency division multiplexing (OFDM) systems suffer from direct current (DC) offset, frequency offset, and IQ imbalance. We have proposed an IQ imbalance estimation scheme in the presence of DC offset and frequency offset, which uses preamble signals in the time domain. In this scheme, the DC offset is eliminated by a differential filter. However, the accuracy of IQ imbalance estimation is deteriorated when the frequency offset is small. To overcome this problem, a new IQ imbalance estimation scheme in the frequency domain with the differential filter has been proposed in this paper. The IQ imbalance is estimated with pilot subcarriers. Numerical results obtained through computer simulation show that estimation accuracy and bit error rate (BER) performance can be improved even if the frequency offset is small.

Fabrication and Characterization of NbN/AlN/NbN Junction on MgO

Using direct current (DC) or radio frequency (RF) magnetron sputtering techniques, NbN/AlN/NbN junctions or AlN/NbN bilayers are prepared on single crystal MgO [001] or MgO (111) substrates respectively, both at ambient substrate temperatures. The crystalline structures of such multilayers are characterized layer-by-layer using X-ray diffraction and transmission electron microscopy (TEM). Interestingly, the AlN barrier in NbN/AlN/NbN/ MgO [001] is amorphous while the NbN/AlN/NbN/MgO (111) is single-crystalline with [001] orientation. The electrical properties of these two structures are compared. Also discussed are the DC and high frequency behavior of NbN/AlN/NbN/ MgO [001] junction.