A Novel Method for Bandwidth and Phase Margin Enhancement of Folded-Cascode Amplifier

This article describes a method to enhance bandwidth and phase margin of conventional folded-cascode op amps. It achieves a larger bandwidth and/or phase margin in folded-cascode CMOS op amps than those of a conventional one in a given CMOS process. For the same bandwidth the new method allows a larger phase margin, and for a given phase margin a larger bandwidth can be obtained. Also, for equal bandwidth, power consumption of the new folded-cascode is lower than the traditional one with similar load.     

CMOS design of a four-quadrant multiplier based on a novel squarer circuit

In this paper a CMOS current-mode analog multiplier circuit based on a novel current-mode squarer circuit is proposed. The circuit is simulated using HSPICE simulator and designed in 0.35 µm standard CMOS technology with ± 1.5 V supply voltage. The simulation results of proposed multiplier for input current range of ±10 μA demonstrate a ?3 dB bandwidth of 24.5 MHz, 475 μW as maximum power consumption, nonlinearity of 1.3 % and a THD of 0.87 % at 1 MHz.     

An ANFIS based fuzzy controller for corner compensation

As threshold voltage of CMOS transistors is the main parameter that takes effect from process variations, in this paper a novel method for corner detection is presented which senses the variations of fabrication process through threshold voltage of the devices. A new general purpose 2-input, 2-output, 25 rules, ANFIS based fuzzy controller is proposed to compensate the variations subsequently. In this controller novel structures are presented for each block including membership function generator, Min–Max selector and defuzzifier. As an application, bias points of comparators of a typical flash ADC are controlled through introduced system in order to compensate the process variation effects and minimizing total power consumption consequently. Due to differential structures used in the architecture of the blocks, major part of the power supply noise is rejected. The Hspice (level 49) simulation results are given using a generic 0.35 μm standard CMOS technology parameters and power supply of 3.3 V with total power consumption of 15.6 mW for 7.4 MFLIPS. Because of simple and symmetrical circuitry, layout of the proposed controller is very compact, about 410 μm × 210 μm.     

Experimental investigation and flow analysis of clear-water scour around pier and abutment in proximity

Local scour around bridge piers and abutments is one of the most significant causes of bridge failure. Despite a plethora of studies on scour around individual bridge piers or abutments, few studies have focused on the joint impact of a pier and an abutment in proximity to one another on scour. This study conducted laboratory experiments and flow analyses to examine the interaction of piers and abutments and their effect on clear-water scour. The experiments were conducted in a rectangular laboratory flume. They included 18 main tests (with a combination of different types of piers and abutments) and five control tests (with individual piers or abutments). Three pier types (a rectangular pier with a rounded edge, a group of three cylindrical piers, and a single cylindrical pier) and two abutment types (a wing–wall abutment and a semi-circular abutment) were used. An acoustic Doppler velocimeter was used to measure the three-dimensional flow velocity for analyses of streamline, velocity magnitude, vertical velocity, and bed shear stress. The results showed that the velocity near the pier and abutment increased by up to 80%. The maximum scour depth around the abutment increased by up to 19%. In contrast, the maximum scour depth around the pier increased significantly by up to l71%. The presence of the pier in the vicinity of the abutment led to an increase in the scour hole volume by up to 87% relative to the case with a solitary abutment. Empirical equations were also derived to accurately estimate the maximum scour depth at the pier adjacent to the abutment.     

Photoactive behavior of polyacrylonitrile fibers based on silver and zirconium co‐doped titania nanocomposites: Synthesis,characterization, and comparative study of solid‐phase photocatalytic self‐cleaning

Silver and zirconium co‐doped and mono‐doped titania nanocomposites were synthesized and deposited onto polyacrylonitrile fibers via sol–gel dip‐coating method. The resulted coated‐fibers were characterized by X‐ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, thermogravimetric analysis, and BET surface area measurement. Photocatalytic activity of the TiO₂‐coated and TiO₂‐doped coated fibers were determined by photomineralization of methylene blue and Eosin Y under UV–vis light. The progress of photodegradation of dyes was monitored by diffuse reflectance spectroscopy. The XRD results of samples indicate that the TiO₂, Ag‐TiO₂, Zr‐TiO₂, and Ag‐Zr‐TiO₂ consist of anatase phase. All samples demonstrated photo‐assisted self‐cleaning properties when exposed to UV–vis irradiation. Evaluated by decomposing dyes, photocatalytic activity of Ag–Zr co‐doped TiO₂ coated fiber was obviously higher than that of pure TiO₂ and mono‐doped TiO₂. Our results showed that the synergistic action between the silver and zirconium species in the Ag‐Zr TiO₂ nanocomposite is due to both the structural and electronic properties of the photoactive anatase phase. These results clearly indicate that modification of semiconductor photocatalyst by co‐doping process is an effective method for increasing the photocatalytic activity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Pure Commercial Titanium Color Anodizing and Corrosion Resistance

In order to improve titanium corrosion behavior, we can increase the thickness of oxide layer on titanium surface during anodizing process and by electrochemistry. In this research, self-color anodizing of Ti in sulfuric acid was done, and anodizing layers were created in different colors. The highest value of chromaticity was 37.8 for the anodized sample in 10 V, and the lowest value was 8.6 at 15 V. The oxide layer thickness was calculated by optical method (light refraction). The anodic film thickness increased by increasing the anodizing voltage. The highest thickness of anodic film was 190 nm in sulfuric acid solution for the anodized sample in 80 V. Corrosion resistance of anodized Ti was studied by potentiodynamic polarization curves in biological solution of Ringer’s at 37 °C. On increasing the anodizing voltage further, corrosion rate of the alloy increased from its lowest rate. The lowest rate of corrosion was for the sample anodized in 10 V, which was 0.96 × 10⁻³ mpy.     

Monitoring dependent process steps using robust cause‐selecting control charts

Cause‐selecting control charts are believed to be invaluable for monitoring and diagnosing multistage processes where the output quality of some stages is significantly impacted by the output quality of preceding stages. To establish a relationship between input and output variables, a standard procedure uses historical data, which are often prone to hold outliers. The presence of outliers tends to decrease the effectiveness of monitoring procedures because the regression model is distorted and the control limits become stretched. To dampen the negative repercussions of outliers, robust fitting techniques based on M‐estimators are implemented instead of the ordinary least‐squares method and two robust monitoring approaches are presented. An example is given to illustrate the application and performance of the proposed control charts. Furthermore, a simulation‐based study is included to investigate and compare the average run length of robust and non‐robust schemes. The results reveal that the robust procedure far outperforms the non‐robust counterpart due to its prompt detection of out‐of‐control conditions when outliers exist. Copyright © 2009 John Wiley & Sons, Ltd.     

Guided Ultrasonic Wave Imaging for Immersed Plates Based on Wavelet Transform and Probabilistic Analysis

We propose a nondestructive evaluation method for immersed structures based on the propagation of ultrasonic waves induced by means of laser pulses and detected with an array of immersion transducers. In the study presented in this article, a laser operating at 532 nm is employed to excite leaky guided waves on an aluminum plate immersed in water. An array of immersion transducers is used to record the waves radiating from the laser-illuminated point. The detected signals are processed with an imaging algorithm based on continuous wavelet transform and probabilistic analysis to localize the presence of artificial defects machined in the plate. With respect to the existing imaging methods for plates, the proposed algorithm is pseudo baseline free, because it does not require data recorded from a pristine plate, but it requires that only a portion of the plate is free from defects. We find that the proposed algorithm enables the detection of surface cracks. Advantages and limitations of the algorithm for the nondestructive evaluation of underwater structures are discussed.