A Continuous Time Auto-Zero Offset Compensated Switched Capacitor Integrator

A continous mode CMOS switched capacitor integrator with almost zero offset is presented. The offset is compensated using an auto-zero technique and proper circut elements have been used to attenuate disturbances due to charge injection and clock feedthrough. The circuit includes two parallel paths which operate alternately in order to integrate in one path while compensating the offset in the other path. The circuit is capable of removing the offset voltage and its integral, and many other spurious signals at the output. The designed integrator has an initial offset of about –250 V which raises to an amount of about –400 V after one second of integration.     

3-D CMOS Circuits Based on Low-Loss Vertical Interconnects on Parylene-N

parylene-N is used as a dielectric layer to create ultra low-loss 3-D vertical interconnects and coplanar waveguide (CPW) transmission lines on a CMOS substrate. Insertion loss of 0.013 dB for a 3-D vertical interconnect through a 15-$mu$ m-thick parylene-N layer and 0.56 dB/mm for a 50- $Omega$ CPW line on the parylene-N layer (compared to 1.85 dB/mm on a standard CMOS substrate) are measured at 40 GHz. L-shaped, U-shaped, and T-junction CPW structures are also fabricated with underpasses that eliminate the discontinuities arisen from the slot-line mode and are characterized up to 40 GHz. A 3-D low-noise amplifier using these post-processed structures on a 0.13-$mu$ m CMOS technology is also presented along with the investigation of parasitic effects for accurate simulation of such a 3-D circuit. The 3-D circuit implementation reduces the attenuation per unit length of the transmission lines, while preserving the CMOS chip area (in this specific design) by approximately 25%. The 3-D amplifier measures a gain of 13 dB at 2 GHz with 3-dB bandwidth of 500 MHz, noise figure of 3.3 dB, and output 1-dB compression point of ${+}$ 4.6 dBm. Room-temperature processing, simple fabrication, low-loss performance, and compatibility with the CMOS process make this technology a suitable choice for future 3-D CMOS and BiCMOS monolithic microwave integrated circuit applications that currently suffer from high substrate loss and crosstalk.      

The City in the Traumatic Scene of Modernity

This essay critically analyzes the current notion of ‘reconstruction’ of the contemporary city, dominated by the historicist conception of history and the naive notions of memory and modernity. In first part, it attempts to provide an alternative theoretical framework by advancing the idea of the ‘Traumatic Memory of the City’ through the writings of Walter Benjamin on the city. This first part then provides the ground for the second part which critically examines the recent reconstruction of the center of Berlin as a case of a historicist act that has succeeded in abolishing and erasing much of the ‘traumatic memory’ of the city of Berlin in its modern history. The essay ends by questioning the validity of the current conception of ‘reconstitution’ and suggest it be coupled with the notions of ‘re-making’ and ‘iteration’¹     

Adhesive surface interactions of cellulose nanocrystals from different sources

Adhesion plays an important role in the final properties of nanocomposites. This study explored the surface interaction of cellulose nanocrystals (CNCs) and the effect of CNC sources on adhesion between individual CNCs and the Si tip of an AFM cantilever using a force mapping technique called FMap. The adhesion between CNCs and a Si tip from five different sources has been studied: cotton, Whatman filter paper, hemp, softwood chemical kraft pulp, and softwood-dissolving pulp (alistaple). Mica was used as the background substrate to act as an internal standard. This study’s findings suggest that adhesion is not the same for all CNCs. Transmission electron microscopy and atomic force microscopy were used to determine the size and shape of each CNC. The experimental quantitative data showed that adhesion between CNCs and the Si tip has a close correlation with the diameter of the CNCs. X-ray photoelectron spectroscopy confirmed the presence of sulfate groups on the surface of the CNCs and a correlation between adhesion and surface chemistry of the CNCs was observed.     

GaN nanorod Schottky and p-n junction diodes

Conductive atomic force microscopy has been used to characterize single GaN nanorod Schottky and p-n junction diodes. The ideality factor, reverse breakdown voltage, and the Schottky barrier height of individual nanorod diodes were compared to those from conventional thin-film diodes. Large-area contacts, enabling diodes with arrays of GaN nanorods in parallel, were also fabricated and their electrical characteristics investigated. The defect-free nature of the GaN nanorods and enhanced tunneling effects due to nanoscale contacts have been invoked to explain the electrical behavior of the nanorod diodes.     

Reduced-Memory Direct Digital Frequency Synthesizer Using Parabolic Initial Guess

Based on the parabolic approximation, which was recently introduced by the authors, a new architecture for sine-output direct digital frequency synthesizers has been developed. Due to using this approximation, and also considering several memory-reduction techniques, the proposed architecture is so designed that needs only 728 bits read-only memory for mapping a 12-bit phase address to 10-bit sine amplitude. The synthesizer has also been implemented and the experimental results show its desired operation and performance.     

Oligodeoxyribonucleotide association with single-walled carbon nanotubes studied by SPM

Studies have been performed on both as-received and chemically oxidized single-walled carbon nanotubes (SWCNTs) grown by two different growth methods to better understand the preferential association of the oligodeoxyribonucleotide T30 (ODN) with SWCNTs. Samples of T30 ODN:SWCNT were examined under ambient conditions using non-contact scanning probe microscope (SPM) techniques. The resulting images show different morphologies ranging from tangled networks of SWCNTs to individual, well-dispersed isolated SWCNTs as the sonication time is increased. SPM images of well-dispersed, as-received SWCNTs reveal isolated features that are 1.4 to 2.8 nm higher than the bare SWCNT itself. X-ray photoemission spectroscopy (XPS) confirmed these features to be T30 ODN in nature. Chemically oxidizing the SWCNTs before sonication is found to be an effective way to increase the number of T30 ODN features.     

Adsorption of cerium and lanthanum from aqueous solutions by chitosan/polyvinyl alcohol/3-mercaptopropyltrimethoxysilane beads in batch and fixed-bed systems

Adsorption of La(III) and Ce(III) from aqueous solutions by novel chitosan modified with poly(vinyl alcohol) as a promoter of mechanical and chemical properties and 3-mercaptopropyltrimethoxysilane as a promoter of the functional group was investigated in batch and continuous modes. The FTIR analyses showed that mecapto groups have been successfully added to chitosan/poly(vinyl alcohol). The BET surface area, pore diameter, and pore volume of adsorbents were 1.68?m² g^?1, 2.516?nm, and 0.058?cm³ g^?1, respectively. The effects of the operating parameters such as pH, contact time, initial metal ion concentration, adsorbent dosage, and temperature were studied in batch mode operation. Optimum pH was found to be 5. According to the Langmuir model, the maximum adsorption capacities for La(III) and Ce(III) ions were 263.16 and 251.41?mg?g^?1, respectively. The thermodynamic study showed that the adsorption process of both metal ions was endothermic and spontaneous favored at the higher temperature. In the column study, the effects of the flow rate and initial concentration were investigated. The maximum adsorption capacities based on the Thomas model for La(III) and Ce(III) ions were 460.94 and 374.83?mg?g^?1 at a flow rate of 4?mL min^?1 and an initial metal concentration of 300?mg?L^?1, respectively.     

Effects of in‐cycle strength degradation on collapse capacity of steel moment frames

In this study, the effects of in‐cycle strength degradation of steel moment connections are investigated on global behavior of multiple degree‐of‐freedom structures. Two types of degrading connection models are defined and compared with a bilinear non‐degrading model. Due to dispersion of the experimental test results on connections performance, two models are considered for each type. A probability assessment is carried out by implementation of incremental dynamic analysis to find the capacity of the structures for various performance levels. A sensitivity study is conducted on hysteresis parameters of connection models to investigate the effect of these parameters on global behavior of the structures. Due to increased dispersion of displacement demands observed in degrading cases, a reliability analysis is carried out to consider the effect of uncertainty on confidence level of the structures. Results show that in‐cycle strength degradation can lead to abrupt dynamic instability and as a consequence decrease in reliability of the system against collapse. Copyright © 2013 John Wiley & Sons, Ltd.     

Low power and high gain current reuse LNA with modified input matching and inter-stage inductors

In this paper we present a fully integrated current reuse CMOS LNA (low noise amplifier) with modified input matching circuitry and inductive inter-stage architecture in 0.18 μm CMOS technology. To reduce the large spiral inductors that actually require larger surface area for their fabrication, two parallel LC circuits are used with two small spiral on-chip inductors. Using cascode configuration equipped by parallel inter-stage LCs, we achieved lower power consumption with higher power gain. In this configuration we used two cascoded transistors to have a good output swing suitable for low voltage technology compared to other current reuse configurations. This configuration provides better input matching, lower noise figure and more reverse isolation which is vital in LNA design. Complete analytical simulation of the circuit results in center frequency of 5.5 GHz, with 1.9 dB NF, 50 Ω input impedance, 1 GHz 3 dB power bandwidth, 20.5 dB power gain (S₂₁), high reverse isolation (S₁₂)<−48 dB, −18.5 dB input matching (S₁₁) and −21.3 dB output matching (S₂₂), while dissipating as low power as 2 mW at 1.8 V power supply.