A low-power, second-order Δ/Σ modulator using a single class-AB op-amp for voice-band applications

The design of a power-efficient second-order Δ/Σ modulator for voice-band is presented. At system level, a new single-loop, single-stage modulator is proposed. The modulator employs only one class-AB op-amp to realize a second-order noise shaping for voice-band applications. The modulator is designed in a 0.25μm standard CMOS process, and exhibits 86 dB dynamic range (DR) for a 4 kHz voice-bandwidth. The proposed modulator consumes 125μW from a 2.5 V supply. Aminghasem Safarian received the B.S. and M.S. degrees in electrical engineering from the Sharif University of Technology, in 2000, 2002, respectively. Since 2003 he is a research assistant at University of California, Irvine, working toward his Ph.D. degree in electrical engineering emphasizing on RF IC design for wireless communication systems. During the summer of 2005, he was with Broadcom Corporation, Irvine, CA, where he developed integrated receivers for RFID and WCDMA applications. Farzad Sahandiesfanjani was born in Tabriz, Iran in 1976. He received the B.S. and M.S. degrees in electronics from Sharif University of Technology, Tehran, Iran, in 1998 and 2000, respectively. The subject of his thesis was the design of 4th order cascade delta-sigma modulator for ADSL Analog Front End. From 1998 to 2003, he was with Emad Semicon Co., Tehran, Iran, where he designed circuits for voice application such as CODEC and SLIC chip. He also designed a 3rd order single loop class-D delta-sigma modulator for audio application. He joined Tripath Technology Inc., San Jose, CA, in 2003 and has been working on the design of analog and mixed-signal circuits for class-T audio power amplifier. He is also author of one patent for inductor-less switching audio power amplifier and also co-author of 3 more pending patents and 4 papers. Payam Heydari (S'98–M'00) received the B.S. and M.S. degrees (with honors) in electrical engineering from the Sharif University of Technology, in 1992, 1995, respectively. He received the Ph.D. degree in electrical engineering from the University of Southern California, in 2001. During the summer of 1997, he was with Bell-Labs, Lucent Technologies, Murray Hill, NJ, where he worked on noise analysis in deep submicron very large-scale integrated (VLSI) circuits. During the summer of 1998, he was with IBM T. J. Watson Research Center, Yorktown Heights, NY, where he worked on gradient-based optimization and sensitivity analysis of custom-integrated circuits. Since August 2001, he has been an Assistant Professor of Electrical Engineering at the University of California, Irvine, where his research interest is the design of high-speed analog, radio-frequency (RF), and mixed-signal integrated circuits. Dr. Heydari has received the 2005 National Science Foundation (NSF) CAREER Award, the 2005 IEEE Circuits and Systems Society Darlington Award, the 2005 Henry Samueli School of Engineering Teaching Excellence Award, the Best Paper Award at the 2000 IEEE International Conference on Computer Design (ICCD), the 2000 Honorable Award from the Department of EE-Systems at the University of Southern California, and the 2001 Technical Excellence Award in the area of Electrical Engineering from the Association of Professors and Scholars of Iranian Heritage (APSIH). He was recognized as the 2004 Outstanding Faculty at the EECS Department of the University of California, Irvine. His name was included in the 2006 Who's Who in America. Dr. Heydari is an Associate Editor of the IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—part I. He currently serves on the Technical Program Committees of Custom Integrated Circuits Conference (CICC), International Symposium on Low-Power Electronics and Design (ISLPED), International Symposium on Quality Electronic Design (ISQED), and the Local Arrangement Chair of the ISLPED conference. He was the Student Design Contest Judge for the DAC/ISSCC Design Contest Award in 2003, the Technical Program Committee member of the IEEE Design and Test in Europe (DATE) from 2003 to 2004, and International Symposium on Physical Design (ISPD) in 2003. Mojtaba Atarodi received his Ph.D degree from USC (the University of Southern California, Los Angeles), in electrical engineering Electro-physics in 1993, his M.S from University of California at Irvine, and his B.SEE from the Tehran Polytechnic University with first Grade honor. Following his Ph.D completion, he was with Linear Technology Corporation from 1993 to 1996 as an analog design engineer. He has been with Sharif University of Technology as an Assistant and Visiting Professor since 1997. The Author of more than 50 technical journal and conference papers an a book on Analog CMOS IC Design, Dr Atarodi’s main research interests are analog and RF IC system, circuit, and signal processing design as well as analog synthesis tools. Having held several management and consulting positions during the last 15 years in the US industry, he holds one US patent in analog highly linear tunable Operational Transconductance Amplifiers and has applied for 5 more US patents as well.     

Neuro-Adaptive Output Feedback Control for a Class of Nonlinear Non-Minimum Phase Systems

This paper presents an adaptive output-feedback control method for non-affine nonlinear non-minimum phase systems that have partially known Lipschitz continuous functions in their arguments. The proposed controller is comprised of a linear, a neuro-adaptive and an adaptive robustifying control term. The adaptation law for the neural network weights is obtained using the Lyapunov’s direct method. One of the main advantageous of the proposed method is that the control law does not depend on the state estimation. This task is accomplished by introducing a strictly positive-real augmented error dynamic and using the Leftshetz–Kalman–Yakobuvich lemma. The ultimate boundedness of the error signals will be shown analytically using the extension of Lyapunov theory. The effectiveness of the proposed scheme will be shown in simulations for the benchmark problem Translational Oscillator/Rotational Actuator (TORA) system.     

Effect of fatty amine and perfluorocarbon as anti‐fouling agent on the catalyst activity and titanium oxidation state in slurry polymerization of ethylene

In this work, the effect of two antifouling materials on the activity of catalyst used to produce polyethylene in a 1‐L slurry reactor and on the titanium oxidation state of the catalyst was investigated. Armostat 300 with the formula alkyl C₁₄‐C₁₈ bis(2‐hydroxyethyl)amine is an antistatic agent that reduces static electricity of the polymer particles. It was found that within the concentration of 0.16–1.32 g/mmol Ti, Armostat 300 helps to increase the catalyst activity to 1.3–2 times. The variation of the titanium oxidation state of the catalyst in the presence of Armostat 300 at 80°C with Al/Ti molar ratio of 100 showed that Ti (III) species increased. The effect of Armostat 300 on T_m, % X_c, density, bulk density, and MFI of polymer was insignificant. In this work, Zonyl FSN‐100 with the formula R_f(CH₂CH₂O)_xH, R_f = F(CF₂CF₂)_y, y = 1–9, x = 1–26 was used as antifouling agent in copolymerization of ethylene with 1‐butene. It was found that Zonyl FSN‐100 at the concentration range of 5–20 ppm reduces the catalyst activity to 1.11–1.9 times. It was also shown that Ti (III) species in the presence of Zonyl FSN 100 decreased. This antifouling agent slightly decreased the properties of polymer including % X_c, density, and M_w. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 257–260, 2006     

Analysis of catalyst particle strength by impact testing: The effect of manufacturing process parameters on the particle strength

The mechanical strength of porous alumina catalyst carrier beads, used in the reforming units with continuous catalytic regeneration, was measured by impact testing. With this testing method particle strength can be measured at higher strain rates than the traditional crushing test method, hence providing a better simulation of pneumatic conveying and chute flow conditions, and also a large number of particles can be tested quickly. This is important for particles with a brittle failure mode such as the alumina particles used in this work as a wide distribution of mechanical strength usually prevails. Extensive impact testing was carried out first with an industrial sample, in order to understand the failure mechanism of this type of particles and to develop a methodology for analysing the extent of breakage by impact. Then the method was used to analyse the effect of a number of process parameters, such as filler, macroporosity and drying procedure on the particle strength with the aim of optimising the manufacturing process. The impact test results were then used to test the model of breakage behaviour of particulate solids proposed by Vogel and Peukert [Vogel and Peukert, Breakage behaviour of different materials—construction of a mastercurve for the breakage probability. Powder Technol., 129 (2003) pp. 101-110].     

A Wide Tuning Range, Fractional Multiplying Delay-Locked Loop Topology for Frequency Hopping Applications

This paper introduces a low-jitter and wide tuning range delay-locked loop (DLL) -based fractional clock generator (CG) topology. The proposed fractional multiplying DLL (FMDLL) architecture overcomes some disadvantages of phase-locked loops (PLLs) such as jitter accumulation while maintaining the advantageous of a PLL as a multi-rate fractional frequency multiplier. Based on this topology, a CG with 1–2.5 GHz output frequency tuning range has been designed in a digital 0.18 um CMOS technology while the multiplication ratios are M+k/(2N_C) in which M, k, and N_C are adjustable. To generate some finer ratios, k is changed periodically or randomly (by a digital delta-sigma modulator) between two consecutive integer numbers. Operating in 2.5 GHz, total circuit including digital part consumes 15.5 mW from 1.8 V supply voltage. At the proposed architecture, reference clock is injected into a ring oscillator in specified times and to the specified delay-stages to synthesize the fractional frequency multiplication as well as resetting the accumulated jitter during previous cycles. Operating in maximum speed, simulated RMS (root-mean-square) and PTP (peak-to-peak) jitter values are 1.8 and 14.5 ps, respectively, while the settling time is 5 us. Armin Tajalli received the B.Sc. from Sharif University of Technology (SUT), Tehran, Iran, in 1997, and M.Sc. from Tehran Polytechnic University, Tehran, Iran, in 1999. From 1998 he has joint Emad Co. as a senior design engineer where he has worked on several industrial and R&D projects on analog and mixed-mode ICs. He received the award of the Best Design Engineer from Emad Co., 2001, the Kharazmi Award of Industrial Research and Development, Iran, 2002, and Presidential Award of the Best Iranian Researchers, in 2003. He is now working toward his Ph.D. degree at SUT. His current interests are design of high speed circuits for telecommunication systems. Pooya Torkzadeh was born in Isfahan, on April 21, 1980. He received the B.Sc. degree from Isfahan University of Technology (IUT), Isfahan, in 2002 and the M.Sc. degree from Sharif University of Technology (SUT), Tehran, in 2004, both in electrical engineering. From 2002 to 2004, he was an Assistant with SUT and the member of Sharif Integrated Circuit And System Group (SICAS). His major activities are in Electronics Integrated Circuit Designing and Digital Signal Processing (DSP). He specializes in CMOS Integrated Circuits particularly for Clock Generation, Clock-Data Recovery Systems, and Sigma-Delta Analogue to Digital Converter Applications. Mojtaba Atarodi received the B.S.E.E. from Amir Kabir University of Technology (Tehran Polytechnic) in 1985, and M.Sc. degree in electrical engineering from the University of California, Irvine, in 1987. He received the Ph.D. degree from the University of Southern California (USC) on the subject of analog IC design in 1993. From 1993 to 1996 he worked with Linear Technology Corporation as a senior analog design engineer. Since then, he has been consulting with different IC companies. He is currently a visiting professor at Sharif University of Technology. He has published more than 30 technical papers in the area of analog and mixed-signal integrated circuit design as well as analog CAD tools.     

Effects of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nano-Particles on Corrosion Performance of Plasma Electrolytic Oxidation Coatings Formed on 6061 Aluminum Alloy

Corrosion resistance improvement of plasma electrolyte oxidation coatings on 6061 aluminum alloy in silicate electrolyte containing Al₂O₃ nano-particles was studied, with particular emphasis on the microstructure, coating growth, and corrosion behavior in 3.5 wt.% NaCl solution. The microstructure of coatings, their thickness, and phase composition were characterized using scanning electron microscopy and x-ray diffraction. All characterization data showed that the maximum coating thickness and lowest amount of porosity were obtained in a low concentration of KOH, a high concentration of Na₂SiO₃, and moderate concentration of Al₂O₃ nano-particles in the electrolyte. This combination describes the optimum plasma electrolytic oxidation electrolyte, which has the best conductivity and oxidizing state, as well as the highest incorporation of electrolyte components in the coating growth process. On the other hand, incorporation and co-deposition of Al₂O₃ nano-particles were more pronounced than SiO₃ ^2? ions in some level of molar concentration, which is due to the higher impact of electron discharge force on the adsorption of Al₂O₃ nano-particles. The electrochemical results showed that the best protective behavior was obtained in the sample having a coat with the lowest porosity and highest thickness.     

Porous Carrageenan-<Emphasis Type="Italic">g</Emphasis>-polyacrylamide/bentonite superabsorbent composites: swelling and dye adsorption behavior

A novel superabsorbent composite based on kappa-Carrageenan (κC) was prepared by graft copolymerization of acrylamide (AAm) onto κC in the presence of bentonite powder using methylenebisacrylamide (MBA) as a crosslinking agent, ammonium persulfate (APS) as an initiator, and sodium carbonate as a pore-forming agent. The swelling behavior in distilled water and in solutions with different pH values was investigated. The results indicated that with increasing carrageenan/bentonite weight ratio, the swelling capacity is increased but the gel content is decreased. The swelling rate of the hydrogels was improved by introducing sodium carbonate as pore-forming agent. The prepared superadsorbent composites were used as adsorbent for a cationic dye, methylene blue. Isotherm of adsorption and the effect of pH, adsorption dosage, contact time and initial dye concentration on dye adsorption were also studied. The results showed that maximum adsorption capacity of methylene blue on the prepared adsorbents is 156.25 mg g^?1 and adsorption is well-described by Langmuir isotherm model.     

Microencapsulation of 1-methylimidazole using solid epoxy resin: study on microcapsule residence time and properties of the system

In this study for the first time 1-methylimidazole was microencapsulated successfully by solid epoxy resin using solvent evaporation method. Fourier transform infrared spectroscopy, scanning electron microscopy, thermal gravimetric and differential scanning calorimetry were used for characterization of microcapsule and epoxy resin/microcapsule systems. The results revealed that although the solid epoxy shell was in contact with imidazole curing agent for a long time, it still remained as a thermoplastic. The chain length of the solid epoxy resin was grown in anionic polymerization process which led to an increase in the melting temperature from 64 to 78 °C. On the other hand, all epoxy functional groups of the shell did not participate in the curing reaction of resin with core curing agent of the microcapsule. The results showed that by increasing the residence time of the microcapsules, the number of epoxy groups of liquid epoxy decreased slightly but the rate of complex viscosity increase or the rate of curing reaction was increased and the cured epoxy system exhibited a single-phase morphology. On the other hand, in the presence of microcapsules the curing reaction of epoxy resin was successfully carried out and the curing temperature and the onset of viscosity increase or gel time at 120 °C were not more or less affected by sufficiently long contact time of epoxy and microcapsule.     

Optimization of a subsonic wind tunnel nozzle with low contraction ratio via ball-spine inverse design method

The goal of wind tunnel design is to generate a uniform air flow with minimum turbulence intensity and low flow angle. The nozzle is the main component of wind tunnels to create a uniform flow with minimal turbulence. Pressure distribution along nozzle walls directly affects the boundary layer thickness, pressure losses and non-uniformity of flow velocity through the test section. Although reduction of flow turbulences and non-uniformity through the test section can be carried out by nozzles with high contraction ratio, it increases the construction cost of the wind tunnel. For decreasing the construction cost of nozzle with constant test section size and mass flow rate, the contraction ratio and length of nozzle should be decreased; that causes the non-uniformity of outlet velocity to increase. In this study, first, three types of nozzle are numerically investigated to compare their performance. Then, Sargison nozzle with contraction ratio of 12.25 and length of 7 m is scaled down to decrease its weight and construction cost. Having scaled and changed to a nozzle with contraction ratio of 9 and length of 5 m, its numerical solution reveals that the non-uniformity of outlet velocity increases by 21%. By using the Ballspine inverse design method, the pressure distribution of the original Sargison nozzle is first scaled and set as the target pressure of the scaled down nozzle and geometry correction is done. Having reached the target nozzle, numerical solution of flow inside the optimized nozzle shows that the non-uniformity just increases by 5% in comparison with the original Sargison nozzle.     

Sensitivity analysis for failure assessment of concrete pipes subjected to sulphide corrosion

Sulphide corrosion in concrete sewers is the most common form of deterioration and should be investigated in failure assessment of sewage systems. Corrosion parameters are considered as random variables because of data scarcity and uncertainties involved in the corrosion affected concrete sewers. Sensitivity analysis is widely accepted as a necessary part of failure assessment of structures and infrastructure, in which the effect of random variables on the failure can be analysed.

In the current study, the results of sensitivity analysis of a corrosion affected concrete sewer in the UK showed that among eight random variables, alkalinity of concrete and relative depth of the flow have the most effect on the probability of sewer failure. The analysis showed less significant contribution of some variables in failure functions. Therefore, it would not be necessary to consider those parameters as random variables and they can be treated as deterministic constant values for further studies.