Sharif Digital Repository

A 1-V CMOS current steering digital to analog converter with enhanced static and dynamic linearity is presented. The 14-bit static linearity is achieved by a novel background analog self calibration technique which is suitable for low voltage applications and does not require error measurement and correction circuits. To improve dynamic linearity at high frequencies, a new low power track/attenuate output stage is used at the DAC output. Integral and differential nonlinearities of the proposed DAC corresponding, to 14-bit specification are less than 0.35LSB and 0.25LSB, respectively. The DAC is functional up to 400MS/S with SFDR better than 71dB in the Nyquist band. The circuit has been... 

A new, ultra low-voltage, linear CMOS OTA will be described. A 4th order, 18 MHz low pass Butterworth Gm-C filter has been designed with this new OTA stage for video applications. In this filter a new, fully digital approach has been used for frequency tuning. The THD of the filter for input signal 0.5 VPPis better than -60 dB. All of circuits are designed based on 0.25 um CMOS process technology with a single 1-volt power supply  

A low voltage bandgap reference (BGR) in CMOS technology, with high power supply rejection ratio (PSRR) is presented. The proposed circuit uses a regulated current mode structure and some feedback loops to reach a low voltage, low power and high PSRR voltage reference. The circuit was designed and simulated in 0.25um CMOS technology, with a power supply of 1 volt. The results show PSRR is below -70dB at 1MHz and the output voltage variation versus temperature (0-70) is less than 0.3%. This circuit shows robustness against process variation  

A new single-bit cascaded 2-2 σ/δ (Sigma-Delta) modulator with only two op-amps, instead of four ones in conventional modulators, to decrease the static power consumption and area, is designed for GSM transceiver applications. The circuit consists of two new single op-amp, second-order, and low-pass loop filters to achieve a fourth-order quantization noise shaping. The modulator shows 84dB DR (Dynamic Range) for GSM signal bandwidth, while consuming 2.3mW from a 2.5V supply voltage. © 2003 IEEE  

In this paper a new low-voltage two-stage class-AB line driver for ADSL applications is presented. The new proposed line-driver consists of only two stages with a new method to control the quiescent current of the output stage. The low-voltage full-CMOS high-linear line driver shows -77 dB THD for a load as low as 20 ohms. The line driver has variable gain, attenuating the input signal from 0dB to -14dB with 2dB steps. The peak to peak differential output swing is 4.2-V from a 2.5-V Supply voltage in a 0.25um standard CMOS technology  

A 12 bit 25 MS/S pipelined analog-to-digital (A/D) converter was designed and simulated using 0.35 μm CMOS technology. The proposed new high speed class AB opamp makes it possible to achieve requirements of 12 bit resolution and settling in 20 ns within 0.05% accuracy. However, pipeline ADCs are tolerant to comparator's offset, but using dynamic comparators, power dissipation can be reduced. So a dynamic comparator is designed which is more power efficient. Total power dissipation is about 76 mW from a single 3 V supply, where INL and DNL are 0.8 LSB and 0.6 LSB respectively. A SNDR of 70.1 dB is achieved. © 2003 IEEE  

An ultra-low-voltage low-power high-speed class-AB operational amplifier with a new structure is presented. A new technique called "Slew Boost" is introduced to improve amplifier's large-signal settling behavior, most useful in switched-capacitor circuits such as pipelined ADCs, sigma delta modulators, etc. The proposed op-amp has been designed to be employed in the first stage of a 10bit 150MSamples/sec pipelined analog-to-digital converter. Simulation results of the proposed fully-differential class-AB op-amp using 0.18um CMOS process models, confirm that it has an output swing of 1.5 Vp-p and consumes less than 1mW from a single supply of 1 volt  

An ultra-low-voltage low-power high-speed class-AB operational amplifier with a new structure is presented. A new technique called 'Slew Boost' is introduced to improve amplifier's large-signal settling behavior, most useful in switched-capacitor circuits such as pipelined ADCs, sigma delta modulators, etc. The proposed op-amp has been designed to be employed in the first stage of a 10 bit 150 MSamples/sec pipelined analog-to-digital converter. Simulation results of the proposed fully-differential class-AB op-amp, using 0.18 μm CMOS process models, confirm that it has an output swing of 1.5 Vp-p and consumes less than I mW from a single supply of I volt. © 2003 ACM  

A 1.8-v 13-bit 25MS/S pipelined analog-to-digital (A/D) converter was designed and simulated using 0.18um CMOS technology. The proposed new high speed low power class AB opamp makes it possible to achieve requirements of 13-bit resolution and settling in 12ns within 0.01% accuracy. An optimum architecture for noise and power consideration is also selected to reduce power. Total Power dissipation is about 82 mw from a single 1.8 v supply, where INL and DNL are 0.7 LSB and 0.6 LSB respectively. SNDR of 75.5 dB is achieved  

In this paper, we evaluate the capacity of Multiple-Input Multiple-Output (MIMO) systems using directional antennas in non-isotropic scattering environments. Our analytical analysis approach results in closed-form approximate formulas in low Signal to Noise Ratio (SNR) regime (in contrast to previous research works which have investigated the same problem by employing experimental or simulation frameworks). We propose an upper bound for the introduced approximate error. Our results show that MIMO systems equipped with directional antennas may have much higher capacity in nonisotropic scattering environments compared to MIMO systems equipped with omni-directional antennas. We also evaluate... 

This paper addresses dynamic cell formation problem (DCFP) which has been explored vastly for several years. Although a considerable body of literature in this filed, two remarkable aspects have been significantly ignored so far, as uncertainty and human-related issues. In order to compensate such a shortage, this paper develops a bi-objective stochastic model. The first objective function of the developed model seeks to minimize total cost of machine procurement, machine relocation, inter-cell moves, overtime utilization, worker hiring/laying-off, and worker moves between cells; while the second objective function maximizes labor utilization of the cellular manufacturing system. In the... 

In this paper, trace locality of reference (LoR) is identified as a mechanism to predict the behavior of a variety of systems. If two objects were accessed nearby in the past and the first one is accessed again, trace LoR predicts that the second one will be accessed in near future. To capture trace LoR, trace graph is introduced. Although trace LoR can be observed in a variety of systems, but the focus of this paper is to characterize it for data accesses in memory management systems. In this field, it is compared with recency-based prediction (LRU stack) and it is shown that not only the model is much simpler, but also it outperforms recency-based prediction in all cases. The paper... 

It is now known that at least 10% of samples with pancreatic cancers (PC) contain a causative mutation in the known susceptibility genes, suggesting the importance of identifying cancer-associated genes that carry the causative mutations in high-risk individuals for early detection of PC. In this study, we develop a statistical pipeline using a new concept, called gene-motif, that utilizes both mutated genes and mutational processes to identify 4211 3-nucleotide PC-associated gene-motifs within 203 significantly mutated genes in PC. Using these gene-motifs as distinguishable features for pancreatic cancer subtyping results in identifying five PC subtypes with distinguishable phenotypes and... 

This paper has been prepared, based on reports regarding extraordinary induced ac voltage on buried gas pipelines in residential and industrial areas of the capital city of Tehran, especially in densely populated central areas. Also, some reports are considered on the existence of ac induced voltage in buried gas pipelines under the overhead transmission lines, for example, one case located 80 Km to the west of Tehran, in an agricultural region of the town of Abyek. In this paper, the results of an extensive theoretical, experimental and practical investigation and implementation of methods carried out during the last two years are introduced. Furthermore, this paper includes evaluation of... 

The axial turbine is one of the most challenging components of gas turbines for industrial and aerospace applications. With the ever-increasing requirement for high-aerodynamic performance blades, three-dimensional aerodynamic shape optimization is of great importance. In this research, the rear part of a gas turbine consisting of a one-stage axial turbine is optimized numerically. A useful optimization algorithm is presented to improve the efficiency and/or pressure ratio of the axial turbine with two different objective functions. The three-dimensional blade-shape optimization is employed to study the effects of the turbine stator and rotor lean and sweep angles on the turbine performance.... 

A high quality joint of zinc based pressure die cast alloys can be hardly achieved by conventional fusion welding. In this study, a novel technique to achieve the globular weld structure using stirring the localized semisolid zone during butt joining of Zamak-3 pressure die cast alloy is proposed and effect of welding parameters on mechanical and microstructural properties are investigated. A gas heating system was designed to heat up the nitrogen gas to desired temperature accurately to create a localized semisolid pool. At this stage a fine stirrer was introduced into the weld seam in order to mix the two sides into a single uniform joint. By presented process, globular microstructure of... 

The human protein disulfide isomerase (hPDI), is an essential four-domain multifunctional enzyme. As a result of disulfide shuffling in its terminal domains, hPDI exists in two oxidation states with different conformational preferences which are important for substrate binding and functional activities. Here, we address the redox-dependent conformational dynamics of hPDI through molecular dynamics (MD) simulations. Collective domain motions are identified by the principal component analysis of MD trajectories and redox-dependent opening-closing structure variations are highlighted on projected free energy landscapes. Then, important structural features that exhibit considerable differences... 

Background MicroRNAs (miRNAs) are frequently deregulated in various types of cancer. While antisense oligonucleotides are used to block oncomiRs, delivery of tumour-suppressive miRNAs holds great potential as a potent anti-cancer strategy. Here, we aim to determine, and functionally analyse, miRNAs that are lowly expressed in various types of tumour but abundantly expressed in multiple normal tissues. Methods The miRNA sequencing data of 14 cancer types were downloaded from the TCGA dataset. Significant differences in miRNA expression between tumor and normal samples were calculated using limma package (R programming). An adjusted p value < 0.05 was used to compare normal versus tumor miRNA... 

As noteworthy properties of amine aqueous solutions, the densities and viscosities of aqueous N-Methyldiethanolamine (MDEA) solutions and mixtures of MDEA with 2-Amino-2-methyl-1-propanol (AMP), Diisopropanolamine (DIPA), Monoethanolamine (MEA), and Diethanolamine (DEA) were estimated under CO2 gas loading using Adaptive Neuro-Fuzzy Inference System (ANFIS), Multi-Layer Perceptron Artificial Neural Network (MLPANN), Support Vector Machine (SVM), and Least Square Support Vector Machine (LSSVM). The density and viscosity were estimated as a function of temperature, CO2 loading, pressure, and molecular weight of mixtures. In this regard, the actual data points were collected from the...