A translinear principle based low-power high-precision RMS-to-DC converter in CMOS technology

Analog Integrated Circuits and Signal Processing - In the present study, a low-power high-precision current-mode CMOS true root mean square (RMS)-to-DC converter is presented based on the...     

A pseudo‐differential current‐reuse structure for opamp‐sharing pipelined analog‐to‐digital converters

In this paper, a power efficient pseudo‐differential (PD) current‐reuse structure is presented to alleviate the memory effects of opamp‐sharing in pipelined analog‐to‐digital converters. To implement the PD current‐reuse structure, a switched‐capacitor circuit is introduced for multiplying digital‐to‐analog converter, which has a slight modification compared with the conventional switching scheme with no power penalty. In the proposed multiplying digital‐to‐analog converter circuit, the common‐mode offset amplification of the PD structures is eliminated. Moreover, a PD current‐reuse amplifier is developed from the telescopic structure with an inverter‐based gain‐boosting circuit. The effectiveness of the proposed structure is evaluated in comparison with existing current‐reuse techniques. Copyright © 2014 John Wiley & Sons, Ltd.     

Audio watermarking based on synergy between Lucas regular sequence and Fast Fourier Transform

Multimedia Tools and Applications - The growth of digital technology over the recent years has led to increased sending and saving of electronic media. Taking advantage of digital works without...     

Surface and structure characteristics of commercial K-Feldspar powders: Effects of temperature and leaching media

This study presents morphological and structural variations of K-Feldspar mineral after acid treatment. Both organic and inorganic acids such as C₂H₂O₄, HCl, HNO₃ and H₂SO₄ were employed for this purpose. Another aim of this study was to find an optimum experimental condition for iron (Fe) removal with a minimum damage on the structure of K-Feldspar in which high whiteness index is obtained. The effect of different parameters such as concentration, pH and temperature on the final structure of this mineral was investigated. To find out the chemical composition of powder, XRF was utilized. FTIR, XRD and SEM were employed to study the structure of mineral. Spectrophotometry was chosen to analyze whiteness index of powder after acid treatment. It was found that O—Al—O bond at 647 cm^-1 for H₂SO₄ and HNO₃ treated sample disappeared. However, HCl and C₂H₂O₄ were ineffective at this band. In addition, the results revealed an increase in K-Feldspar content, a decrease in Fe content, an increase in whiteness index and no significant structural change for C₂H₂O₄ leached sample. Whiteness index of 91% was obtained for C₂H₂O₄ leached sample with the pH of 2.5 to 3 at temperature of 50℃ and during 1 h.     

Seismic Performance Evaluation of SSMF with Simple Beam–Column Connections Under the Base Level

Simple beam–column connections are simpler and cheaper in construction than rigid beam–column connections, moreover, beams under the base level are only carrying gravity loads because of high rigidity of basement walls; therefore, seismic performance of special steel moment frame with basement wall is investigated in two cases in this paper. First, as the normal case of design, rigid beam–column connections are used under the base level, then all of the beam–column connections under the base level are changed to simple connections. The seismic performance of these two types is evaluated by FEMA P695 method. For predicting the collapse capacity of each archetype, adjusted collapse margin ratios are evaluated based on several nonlinear analyses and compared to acceptance criteria. Finally, seismic performance of these two kinds of structures is compared with each other. Despite the structural system’s change in height, seismic performance factors of special steel moment frames are considered for designing whole of the structures. Finally all two types of structures pass the acceptability checks and all the initial assumption are proved.     

CHESDA: continuous hybrid and energy-efficient secure data aggregation for WSN

The Journal of Supercomputing - Data aggregation is an effective mechanism to prolong lifetime in the wireless sensor networks by preventing extra data transmission. However, it may have some...     

Local hardness and density variation in glass substrates machined with Spark Assisted Chemical Engraving (SACE)

Spark Assisted Chemical Engraving (SACE) is an unconventional technique for surface micro-machining of non-conductive materials specially glass. SACE offers many advantages for fabrication of microfluidic and Lab on Chip devices. However the exact mechanism of material removal in this technique is not fully understood. Besides, the changes in the properties of the machined sample have not been studied so far. In this letter, the material removed from glass surface is evaluated and the results of nano-indentation test for measurement of the hardness of machined micro-channels surface is reported. Based on the amount of removed mass during machining and results of nano-indentation test on machined samples it is concluded that hardness and density of the machined zones decrease during the process.     

Numerical Investigation of Engineering Systems: Analysis of Accuracy Reduction Due to Model Oversimplification

When faced with the mathematical modeling of any engineering system, whether for design, performance assessment, optimization, or control, the engineer has to determine the level of accuracy versus the simplicity of the mathematical formulation. Although it is universally accepted that the more complex the formulation, the more accurate the results will be, these usually come at the expense of larger CPU times, a substantial amount of computer resources, and are generally limited by the capacity of computers and computing power, which most times precludes their use in favor of simpler models. Many times, however, engineers do not realize the potential risk that oversimplification of a problem generates in terms of accuracy of the results; that is, the model solution does not resemble the system behavior. Through a demonstrative example, the present study addresses the issue of oversimplification of the resulting mathematical model and the corresponding accuracy of its solution. After constructing three sets of models of the physical system, each with a different level of detail, the solutions are then compared to experimental data. The results show that the accuracy of the numerical approximation depends directly on the level of complexity of the mathematical model used, and that oversimplification may result in up to a ninefold degradation of the results. In addition, minor changes in the inlet boundary condition and geometry result in significant changes in the flow pattern, up to a fivefold difference between different models in the recirculation bubble relative error. This information is fundamental for engineering professionals to consider during the modeling process in applications.     

The effect of foundation flexibility and structural strength on response reduction factor of RC frame structures

Current force‐based design procedure adopted by most seismic design codes allows the seismic design of building structures to be based on static or dynamic analyses of elastic models of the structure using elastic design spectra. The codes anticipate that structures will undergo inelastic deformations under strong seismic events; therefore, such inelastic behaviour is usually incorporated into the design by dividing the elastic spectra by a factor, R, which reduces the spectrum from its original elastic demand level to a design level. The most important factors determining response reduction factors are the structural ductility and overstrength capacity. For a structure supporting on flexible foundation, as Soil Structure Interaction (SSI) extends the elastic period and increases damping of the structure‐foundation elastic system, the structural ductility could also be affected by frequency‐dependent foundation‐soil compliances. For inelastic systems supporting on flexible foundations, the inelastic spectra ordinates are greater than for elastic systems when presented in terms of flexible‐base structure's period. This implies that the reduction factors, which are currently not affected by the SSI effect, could be altered; therefore, the objective of this research is to evaluate the significance of foundation flexibility on force reduction factors of RC frame structures. In this research, by developing some generic RC frame models supporting on flexible foundations, effects of stiffness and strength of the structure on force reduction factors are evaluated for different relative stiffnesses between the structure and the supporting soil. Using a set of artificial earthquake records, repeated linear and nonlinear analyses were performed by gradually increasing the intensity of acceleration time histories to a level, where first yielding of steel in linear analysis and a level in which collapse of the structure in nonlinear analysis are observed. The difference between inelastic and elastic resistance in terms of displacement ductility factors has been quantified. The results indicated that the foundation flexibility could significantly change the response reduction factors of the system and neglecting this phenomenon may lead to erroneous conclusions in the prediction of seismic performance of flexibly supported RC frame structures. Copyright © 2010 John Wiley & Sons, Ltd.