A Tutorial on Multiplierless Design of FIR Filters: Algorithms and Architectures

Finite impulse response (FIR) filtering is a ubiquitous operation in digital signal processing systems and is generally implemented in full custom circuits due to high-speed and low-power design requirements. The complexity of an FIR filter is dominated by the multiplication of a large number of filter coefficients by the filter input or its time-shifted versions. Over the years, many high-level synthesis algorithms and filter architectures have been introduced in order to design FIR filters efficiently. This article reviews how constant multiplications can be designed using shifts and adders/subtractors that are maximally shared through a high-level synthesis algorithm based on some optimization criteria. It also presents different forms of FIR filters, namely, direct, transposed, and hybrid and shows how constant multiplications in each filter form can be realized under a shift-adds architecture. More importantly, it explores the impact of the multiplierless realization of each filter form on area, delay, and power dissipation of both custom (ASIC) and reconfigurable (FPGA) circuits by carrying out experiments with different bitwidths of filter input, design libraries, reconfigurable target devices, and optimization criteria in high-level synthesis algorithms.     

Characterization of products evolved from supercritical water gasification of xylose (principal sugar in hemicellulose)

The catalyst decomposition of xylose (the principal sugar in hemicellulose) was examined in supercritical water for temperature from 400 to 600°C. Experiments were performed in the absence and presence of three main types of catalysts [alkali catalysts (K₂CO₃ and KOH) and metal impregnated activated carbons (Ni/AC) and (Ru/AC)] with a reaction time of 1h. Gasification yield reaches maximum values by using K₂CO₃ and KOH at the highest temperature of 600°C. The highest H₂ yield and the highest CH₄ yield were obtained by using Ru/AC and Ni/AC, respectively. Acetic acid and 5-methyl furfural were determined as the main aqueous products and reached maximum value by using Ru/AC.     

Mode I fracture toughness determination with straight notched disk bending method

A new method called the straight notched disk bending method is developed for mode I fracture toughness determination using rock cores. Disk specimens of andesite and marble having a single straight edge notch were subjected to three-point bending loads. Dimensionless stress intensity factor estimations and fracture toughness tests were conducted for different notch lengths, span lengths, thicknesses and diameters of the cylindrical rock specimens. Stress intensity factors were computed by three-dimensional finite element modeling and the results were presented for a wide range of specimen geometrical parameters. Results of experiments were compared to the results of well-known mode I fracture toughness testing methods. For specimens having thickness equal to the radius, mode I fracture toughness was lower and close to the results obtained by semi-circular bending method. When thickness was increased and doubled, mode I fracture toughness increased and approached to the value found by the suggested cracked chevron notched Brazilian disk method. Advantages of the new method included easy specimen preparation and testing procedure, stiffer specimen geometry, smaller fracture process zone, and flexibility of the specimen geometry for the investigation of the size effect behavior.     

Damage to n-MOSFETs from electrical stress Relationship to processing damage and impact on device reliability

The study reported herein examines and compares damage to n-channel and p-channel metal-oxide-silicon field-effect transistors (MOSFETs) from direct current (d.c.) and alternating current (a.c.) electrical stresses as well as the relationship of this damage to plasma processing damage in MOSFETs. The lightly-doped drain (LDD) MOSFETs used are of 0.5 μm channel length and with a 90 Å thick thermally grown gate oxide fabricated using a full flow CMOS process up to and including metal-1 processes and post-metallization annealing (PMA). The damage to MOSFETs is assessed using transistor parameter characterization and charge-to-breakdown measurements on the gate oxide. It is found that manifestations of d.c. stress-induced damage and a.c. stress-induced damage to transistors are fairly similar in that both forms of damage are passivated by PMA and are reactivated by a subsequent d.c. electrical stress. However, a.c. stress-induced damage is observed to occur at much lower electric fields across the gate oxide than those necessary for d.c. stress-induced damage to be significant. This is attributed to a.c. currents, caused by carrier hopping, occurring at relatively low electric fields. One implication of our results is that plasma-charging damage, often attributed to d.c. electrical stress alone, may comprise an a.c. electrical stress component too.     

What determines static friction and controls the transition to sliding?

We studied the shear response of a confined lubricant layer on approach of the transition to sliding with a surface force apparatus modified for oscillatory shear. In a given experiment, we found that the transition to sliding occurred always around the same deformation amplitude although the shear stress needed to initiate sliding varied up to a factor of two depending on sample history. This suggests the concept of deformation-controlled switching from rest to sliding. The elastic spring-constant, in the stick state, weakened with increasing deformation amplitude. This decrease can be described by a power law when plotted versus the distance to a critical deformation amplitude. The build-up of solid-like behavior after sliding stopped was also gradual and was consistent with a logarithmic time dependence. We suggest a model relating the gradual decrease of stiffness to weakening of the boundary layer, specifically to destruction of some elastic links between molecules or between molecules and the solid surfaces. Static friction (the force that must be overcome at the onset of kinetic motion) is proportional to the number of such links formed during the time of stick.     

Distributed call rerouting in multiclass broadband networks

Broadband integrated services digital networks (B-ISDN) must handle multiclass traffic with diverse quality of service requirements. We consider a multiclass routing model in which routes are calculated in a distributed fashion by the call originating nodes. Within this general context, we address the problem of rerouting a set of previously routed calls to avoid a failed link. Under the approach we propose, a single node executes an aggregate, global rerouting of all affected calls and then converts the set of aggregate routes into an allocation of bandwidth on each link to call origination nodes for the purpose of rerouting. The bandwidth allocation is distributed to each origination node, which in turn then calculates routes for the individual calls. The problem faced by each call origination node is a variant of the socalled bandwidth packing problem. We develop and analyze an approximate algorithm for solving this problem in the specific context that arises in our setting.The research was supported by IBM Corporation and by NSF Grant No. CDR-8803012.On personal leave from IBM RTP.     

Effects of Ultrasonic Vibration on the Electroinitiated Copolymerisation of Styrene and Isoprene

Copolymerisation of styrene and isoprene by constant potential electrolysis in dichloromethane was achieved at different polymerisation potentials. Effect of ultrasonic vibration on the rate and the yield of polymerisation has been discussed. The composition of the copolymers was found to be affected by the vibration as well as the polymerisation potential (E_pol). At E_pol=+3.30 V we found that r₁=r₂ and mole percents of isoprene and styrene in copolymer were equal to each other. Equality was also observed on reacted monomer concentrations, at that potential, which can be called critical polymerisation potential. At E_pol values above or below the critical polymerisation potential none of the above-mentioned properties were equal. Monomer reactivity ratios were determined by the integrated Lewis-Mayo equation. Ultrasonic vibration as well as polymerisation potential was found to affect reactivity ratios.     

Reliability and validity of the Social Phobia and Anxiety Inventory for adolescents.

Although social anxiety is known to be common among adolescents, there are no self-report measures with demonstrated reliability and validity for this population. The Social Phobia and Anxiety Inventory (SPAI) is a measure of social anxiety developed for adults. The purpose of this study was to determine the reliability and validity of the SPAI for adolescents. The sample consisted of 223 adolescents (aged 12–18 yrs) from both clinical and community sources. Confirmatory factor analysis established the validity of the 2 separate factors of Social Phobia and Agoraphobia. Reliability estimates by Cronbach alpha were acceptable for the SPAI subscales and total. The SPAI demonstrated good construct validity, showing statistically significant relationships with independent measures of social phobia and other anxiety variables. The results demonstrate that the SPAI is a reliable and valid measure of social phobia for adolescents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)