Optimum shapes of tire‐treads for avoiding lateral slippage between tires and roads

Optimum design of tire‐tread sections is an important practical issue. However, useful study of the problem that can suggest a reliable guideline for determining the optimum tread sections had hardly been made in the past. The present paper describes a new analysis of the state of stresses in tire‐tread sections in contact with the road surface, taking special care of the boundary conditions. Based on the analysis, a method is proposed to determine the optimum tread shapes for avoiding lateral slippage between tires and roads. The displacement potential function formulation, an ideal mathematical model for the practical stress problems, has been used in conjunction with finite‐difference method of solution. For the present analysis, lateral slipping in absence of frictional resistance as well as the no‐slip conditions of the tire‐tread contact surface have been considered along with a large number of tread aspect ratios. The present computational approach proves to be a powerful tool for determining the optimum tread shapes for avoiding the lateral slippage of tire‐treads. Copyright © 2005 John Wiley & Sons, Ltd.     

Interesting aspects of the analysis of resistivity in Li irradiated Bi-2212

Differently heat treated and 55 MeV Li³⁺ beam irradiated Bi₂Sr₂Ca₁Cu₂O_8+δ (Bi-2212) high temperature superconductors have been studied from the analysis of resistivity in the normal state as well as near the superconducting transition. For all the unirradiated and irradiated samples the so-called linear temperature dependence of the normal state resistivity, in a wide temperature range, can well be understood within the variable range hopping (VRH) conduction scenario. Near and above the bulk superconducting transition, the fluctuation enhanced conductivity (paraconductivity) analysis shows a noteworthy modification of the conduction process due to radiation induced defects.     

GALDS: a complete framework for designing multiclock ASICs and SoCs

A Globally Asynchronous, Locally Synchronous (GALS) system with dynamic voltage and frequency scaling can use the slowest frequency possible to accomplish a task with minimal power consumption. With the mechanism for implementing dynamic voltage scaling at each synchronous domain left up to the designer, our Globally Asynchronous, Locally Dynamic System (GALDS) provides a top-down, system-level means to maximize power reduction in an integrated circuit and facilitate system-on-a-chip (SoC) design. Our solution includes three distinct components: a novel bidirectional asynchronous FIFO to communicate between independently clocked synchronous blocks , an all-digital dynamic clock generator to quickly and glitchlessly switch between frequencies and a digitally controlled oscillator to generate the global fixed frequency clocks required by the all-digital dynamic clock generator. In addition to being capable of reducing power consumption when combined with dynamic voltage scaling, a GALDS design benefits from numerous other advantages such as simplified clock distribution, high performance operation and faster time-to-market through the modular nature of the architecture.     

Allocation of unit start-up costs using Cooperative game theory

This paper discusses a three-part generation offer strategy that enables generators to put in unbundled variable operating costs and fixed start-up/no-load costs. We then propose methods based on cost sharing axioms to allocate fixed start-up/no-load costs among electricity consumers/load/retailers that take into account equity and rationality considerations. We focus on the single period cost allocation first. We apply three well-known game theoretic axioms: the core, the nucleolus, and the Shapley value. We discuss the relative merits and demerits of each criterion and also explore certain theoretical conditions for the existence of the core and the Shapley value lying inside the core. Finally, the multiperiod start-up cost allocation problem is studied. Allocations based on individual periods vis-a/spl grave/-vis composite allocation for all periods are compared and contrasted. Numerical examples are used to illustrate all theoretical concepts.     

Feed horn coupled bolometer arrays for SPIRE - design, simulations, and measurements

In this paper, we present the design, modeling, and measurements of feed horn coupled large bolometer arrays being developed for the Herschel Space Observatory's Spectral and Photometric Imaging REceiver (SPIRE) instrument. SPIRE has five arrays of feed horn coupled silicon-nitride micromesh "spider-web" bolometers in two instruments, a three-band photometer, and a two-band Fourier transform spectrometer, each covering the 430-GHz-1.5-THz band. The optical coupling efficiency, bandwidth, and crosstalk between adjacent pixels of the arrays were investigated with numerical electromagnetic-field simulators, and prototype arrays were measured extensively in a test facility. The measured results were found to be in good agreement with simulation predictions, and the simulation results were used as a benchmark for the design goals of the instrument.     

Effect of copper additions in directly quenched titanium–boron steels

The present study concerns the effect of copper additions on the microstructural evolution and mechanical properties of directly quenched Ti–B steels. Ti and B are added as microalloying elements with an aim of achieving adequate austenite hardenability and Cu is added to retard the austenite (γ) → ferrite (α) transformation. Therefore, the microalloying and Cu additions together allow the transformation of austenite to occur at a lower temperature, resulting in a finer microstructure containing martensitic constituents. The direct-quenching route is adopted with an aim of facilitating the nucleation of the constituent phases from the deformed austenite. In order to circumvent the hot-shortness due to the Cu addition, 0.79 wt% Ni has been added to one of the 1.5 wt% Cu microalloyed steels. The present study has demonstrated that the Ni-containing 1.5Cu–Ti–B steel is capable of providing an attractive combination of strength and ductility comparable to the high strength varieties of HSLA steels in directly quenched condition.     

Study of microstructure in vanadium-palladium alloys by X-ray diffraction technique

Present study considers microstructural characterization of vanadium-based palladium (V-Pd) alloys, which are widely used in marine environment due to their high corrosion resistance. The X-ray diffraction line profile analysis (XRDLPA) have been used to assess the microstructure in body centred cubic (bcc) V-Pd alloys having four different nominal compositions in wt.%. X-ray diffraction line broadening analysis on V-Pd alloys has been performed by using different methods like the Warren-Averbach, double-Voigt and Rietveld methods. Finally microstructural defect parameters such as domain size (D), r.m.s. microstrain 〈ɛ ²〉^1/2, twin fault (β′), spacing fault (αɛ) and deformation stacking fault (α) were evaluated in these alloys by Fourier line shape analysis using Rietveld method in which the X-ray diffraction profiles of these alloys were described by the pseudo-Voigt function to fit the experimental data. From analysis it has been observed that twin fault, β′, and the spacing fault, αɛ, are totally absent in these bcc alloy systems because the twin fault, β′, has been observed to be either negative or very small (within experimental error limit) for these alloy systems and the spacing fault, αɛ, appears to be negative. This analysis also revealed that the deformation stacking fault, α, is significantly present in this alloy system and increases with Pd content.     

Local oscillator chain for 1.55 to 1.75THz with 100-/spl mu/W peak power

We report on the design and performance of a fix-tuned /spl times/2/spl times/3/spl times/3 frequency multiplier chain that covers 1.55-1.75THz. The chain is nominally pumped with 100mW at W-band. At 120K the measured output power is larger than 4/spl mu/W across the band with a peak power of 100/spl mu/W at 1.665THz. A similar chain operated at room temperature produced a peak power of 21/spl mu/W. These power levels now make it possible to deploy multipixel heterodyne imaging arrays in this frequency range.     

Simulation and experimental study of interharmonic performance of a Cycloconverter-FedSynchronous motor drive

High-power synchronous motor drives are usually fed from naturally commutated cycloconverters. The output voltage of the cycloconverter contains interharmonics/subharmonics which affect the power quality and restrict the allowable frequency range. Further, a practical circulating current-free cycloconverter usually gives rise to stator current discontinuities. The present paper deals with a simulation method to study the performance of a cycloconverter-fed synchronous motor drive in the presence of interharmonics/subharmonics taking into account the discontinuities in the output current as well as the effect of ripple in the output current on the input current of the cycloconverter. Interharmonics in output phase voltage, output phase current, input supply current, and the field current are estimated and verified with experimental results on a laboratory prototype. The significant oscillating torque components due to these interharmonics are identified in a typical case. The simulation results are useful in power quality studies for such drives and in devising methods for suppression of these interharmonics/subharmonics.