Analytical Model for Viscous Wall Dampers

By now, many civil engineering researchers have extensively studied the application of earthquake energy dissipation systems in seismic‐resistant buildings. Earthquake energy dissipation systems play an important role in enhancing the sustainability of structures against seismic excitation. Frame buildings are strengthened by installing damper devices as supplemental structural members. This article presents the finite‐element‐based development of an analytical model for a viscous wall damper (VWD) device, an alternative to other earthquake energy dissipation systems, which can diminish the effect of earthquakes on structures and improve the seismic performance of multistory buildings subjected to ground motion. The constitutive law of VWDs has been formulated and integrated to develop a finite element model of VWD compatible with the reinforced concrete (RC) structure analytical model. Then, the finite element algorithm has been developed for inelastic analysis of RC buildings equipped with VWD devices capable of detecting damage to both structural members and damper connections under dynamic loading. Based on the developed system, the special finite element program was codified and verified by applying it to a real model of a RC building with supplementary VWD devices. Influence of VWDs on seismic performance of the RC building during earthquake excitation was evaluated. The proposed analytical model for VWD is verified by using experimental test data and analysis result proved that this energy dissipation system succeeds by substantially diminishing and dissipating a structure's induced seismic responses. Also the parametric study indicated that the damping coefficient is very effective on performance of VWD.     

Pseudo-class-AB telescopic-cascode operational amplifier

A novel class-AB architecture for single-stage operational amplifiers is presented. The structure employs a switched-capacitor level shifter to provide a signal-dependent current in the current source of the common-source amplifier. Applying this pseudo-class-AB approach to a telescopic-cascode opamp enhances the effective values of the slew rate and the transconductance and thus the opamp speed.     

Preparation of Electrospun Electroactive Nanofibers of Four Arm Star-Shaped Poly(ε-Caprolactone)-b-Poly(2-Hydroxyethyl Methacrylate) and Its Blends with Polyaniline

A combination of ring-opening polymerization and atom-transfer radical polymerization was used to synthesize a four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate). The structure of obtained copolymer was determined by Fourier transform infrared, ¹H and ¹³C NMR spectroscopies. The uniform electroactive nanofibers consisting blend of four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate) copolymer and polyaniline were produced using electrospinning technique. The electroactivity of prepared nanofibers was investigated using cyclic voltammetry measurement. The morphologies of electrospun nanofibers produced from four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate) and their blends with polyaniline were investigated by the scanning electron microscopy. The presence of polyaniline resulted in significant decrease of sticking fibers.     

A New IIP2 Enhancement Technique for CMOS Down-Converter Mixers

The design of a CMOS mixer for cellular phone and 3G applications is challenging because of tough linearity and noise requirements. A new technique for second-order input intercept point (IIP2) enhancement of CMOS down-converter mixers is introduced in this brief. The technique is based on canceling second-order intermodulation components generated in input pseudodifferential transconductor, by injecting a nonlinear current to the mixer. Since this current is controlled by a high bandwidth feedback loop, the cancellation technique can be used in multistandard mixers for high channel bandwidth applications like UMTS and IEEE802.11 as well as GSM. A CMOS mixer demonstrating the performance for UMTS standard is designed in a 65-nm technology which can work with supplies as low as 1 V. The simulation results show that the differential and common mode IIP2 of the mixer are improved about 22 and 29 dB, respectively, while cancellation circuit consumes less than 3.3 mA. The other mixer parameters such as noise figure are not affected by the proposed technique.     

Periodic graphene nanobuds: A novel Li-storage material

The characteristics of lithium adsorption on graphene and periodic graphene nanobuds (PGNBs) have been studied by means of density functional theory calculations. All calculations have been performed within the Perdew–Burke–Erzenhof functional as implemented in the SIESTA package, with a double-ζ plus polarization basis set. Several starting configurations were considered for interacting systems. The results show that the Li atom is strongly adsorbed on a pure graphene with a binding energy of about −0.85 eV. However, the binding energy enhances to −2.58 eV when Li binds to a PGNB at the hollow site above the center of the nonagon ring. It was found that the increase in binding is due to significant charge transfer from the Li to the PGNB. The stability of the Li/PGNB system was evaluated within ab initio molecular dynamics simulation which has been carried out at room temperature. The very favorable binding energy obtained as well as high specific surface of PGNB (due to attached fullerenes) suggest a considerable possibility to experimentally apprehend these novel systems as a superior media for Li ions storage.     

Multiply-by-two gain stage with reduced mismatch sensitivity

A new multiply-by-two gain stage is presented, suppressing the gain sensitivity to capacitor mismatches. Using one operational amplifier in three phases, a gain of two, which is not highly influenced by the mismatches between the capacitors, is achieved. Circuit-level Monte-Carlo simulations support the reduction of matching requirements.     

Effect of service temperature on structure and mechanical properties of polyamide 6 & 66 tyre cords

The effect of service temperature on chemical structure and mechanical properties of polyamide 6 & 66 tyre cords was studied over the broad range of 50–200 °C and for a period of 16 h. The heat treatment of cords at below 100 °C and above 120 °C was found to reduce their tensile properties considerably. The changes in properties above 120 °C were caused by increase in width of the molecular weight distribution curve as ascertained by gel permeation chromatography (GPC) studies and increase in irregularity of the polymeric chains as ascertained by birefringence studies; this appears to be due to the fact that, by raising the temperature, both chain folding and chain scission occur. Since there was deformation of the amorphous regions as ascertained by FTIR spectroscopy and birefringence studies, the changes in properties below 100 °C were attributed mainly to the effectiveness of thermal oxidation and annealing in the amorphous phase. In other words, the degree of crystallinity increased, the tyre cord became brittle, and breaking load and elongation at break were decreased. The lower reduction of tensile properties at an intermediate temperatures of 100–120 °C was caused by the lower polydispersity and irregularity in the polymeric chains, in comparison with higher temperatures and less crystallinity than lower temperature treatments.     

Enhancement of hydrogen storage by electrophoresis deposition of CNTs into nanoscale pores of silver foams

Hydrogen storage capacity of Ag-CNTs foamed electrodes was studied by chronopotentiometry method. The CNTs (carbon nanotubes) were deposited inside pores of the nanoscale silver foam by electrophoresis deposition (EPD) method and it was believed that the interconnections between the CNTs and the Ag frames were increased and were more stable; therefore, charge transfer process through the electrode became facilitated. XRD, TGA and SEM techniques were employed to examine the purity of the CNTs and the quality of the Ag foam surface.     

High speed sample and hold design using closed-loop pole-zero cancelation

A new closed loop Sample-and-Hold (S&H) architecture is proposed for pipeline analog-to-digital converter (ADC) that breaks the precision-speed-power trade off by means of canceling out the first closed loop pole. This pole-canceling results in widening the bandwidth of the S&H up to the second pole. In this architecture, two amplifiers are used: one for accuracy with little power consumption, another one for high-speed response, which consumes most of the total power. Exploiting these two amplifiers remedies some of the tradeoffs and limitations of opamp design in S&H circuits. Simulated by HSPICE with a standard BSIM3v3 0.13 μm technology, the S&H achieves 80 dB SFDR for a 1.6 V_ppd output at 500 MHz sampling rate.