A 4.5-GHz 130-nm 32-KB L0 cache with a leakage-tolerant self reverse-bias bitline scheme

This paper describes a 32-KB two-read, one-write ported L0 cache for 4.5-GHz operation in 1.2-V 130-nm dual-V/sub TH/ CMOS technology. The local bitline uses a leakage-tolerant self reverse-bias (SRB) scheme with nMOS source-follower pullup access transistors, while preserving robust full-swing operation. Gate-source underdrive of -220 mV on the bitline read-select transistors is established without external bias voltages or gate-oxide overstress. Device-level measurements in the 130-nm technology show 72/spl times/ bitline active leakage reduction, enabling low-V/sub TH/ usage, 40% bitline keeper downsizing, and 16 bitcells/bitline. 11% faster read delay and 2/spl times/ higher dc noise robustness are achieved compared with high-performance dual-V/sub TH/ bitline scheme. Sustained performance and robustness benefits of the SRB technique against conventional dynamic bitline with scaling to 100- and 70-nm technology is also presented.     

Growth of ZnSe∶Mn Nanocrystals from Vapour Phase

ZnSe∶Mn nanocrystals were grown by chemical vapour transport method using the matrix of SiO2 aerogels. The cubic structure of the nanocrystals was confirmed by powder X-ray diffraction (XRD) and electron diffraction (ED) studies. The size of the crystals was observed using transmission electron microscope (TEM). The oxidation state of Mn in ZnSe nanocrystal was found using electron spin resonance (ESR) spectrum. The room temperature luminescence measurements show the peaks corresponding to both bandgap of the material and Mn in ZnSe.     

Theoretical Investigation of Metal Cladding for Nanowire and Cylindrical Micropost Lasers

We investigate the transverse modal properties of cylindrical subwavelength metal-clad nanowire and micropost lasers via rigorous theoretical waveguide analysis, including the effects of finite thickness metal cladding and gain in the core. The results of this analysis show that air-metal surface guided TM₀₁ and some hybrid surface guided modes suffer less loss but are less confined to the core, while core-metal surface guided modes are better confined to the core but suffer greater loss. An increase in the thickness of the metal cladding reduces the loss of the core-metal surface guided modes. The modal gain and confinement of the metal-clad cavity are compared to an unclad cavity.     

Unconstrained and constrained motion control of a planar two-link structurally flexible robotic manipulator

Unconstrained and constrained motion control of a planar two-link structurally-flexible robotic manipulator are considered in this study. The dynamic model is obtained by using the extended Hamilton's principle and the Galerkin criterion. A method is presented to obtain the linearized equations of motion in Cartesian space for use in designing the control system. The approach to solving the control problem is to use feedforward and feedback control torques. The feedforward torques maneuver the flexible manipulator along a nominal trajectory and the feedback torques minimize any deviations from the nominal trajectory. The feedforward and feedback torques are obtained by solving the inverse dynamics problem for the rigid manipulator and designing linear quadratic Gaussian with loop transfer recovery (LQG/LTR) compensators, respectively. The LQG/LTR design methodology is exploited to design a robust feedback control system that can handle modeling errors and sensor noise, and operate on Cartesian space trajectory errors. Computer simulated results are presented for an example planar, two-link, structurally flexible robotic manipulator. © 1994 John Wiley & Sons, Inc.     

VOID FRACTION PROFILES IN PLANE-POISEUILLE FLOW OF VISCOELASTIC FOAMS

This investigation focuses on slow, isothermal, two-phase flow of gas bubble suspensions in Separan solutions, prepared with the help of a sodium borohydride blowing agent at room temperature. The total residence time in these experiments is much smaller than characteristic times for growth or rise of bubbles. The variation of bubble volume fraction across a narrow gap between two planes, is recorded at two locations along the flow direction. This is done with a Cesium gamma-radiation source focused on a region of area.012 cm² in the flow plane, and a Sodium iodide detector across the channel yielding a resolution of.01 over the range of void fractions investigated from.02 to.08. This measurement allows us to identify conditions under which the two-phase flow may be described by a two fluid model with a uniform bubbly core and a bubble free wall layer. With this two phase flow structure, a relative viscosity equation for the suspension is used to compute an apparent viscosity. Such calculations indicate that the observed reduction in apparent viscosity for the two phase flow may be attributed to a bubbly core which is more shear thinning than the medium. The additional shear thinning factor for the suspension is related to the elasticity of the medium.     

Compositional trend analysis on poly(phenylene ether) based thermoplastic elastomers

Detailed statistical trend analysis of thermoplastic elastomers based on poly (phenylene ether) (PPE), polystyrene (PS), ethylene vinyl acetate (EVA) and styrene‐ethylene‐butylene‐styrene (SEBS) was done through Design Expert software by Stat‐Ease. D optimal crossed design was followed to capture the interaction with the parameters. Effect of blend ratio, vinyl acetate (VA) content of EVA, molecular weight (MW) of SEBS and intrinsic viscosity (IV) of PPE on the blend performance (response) was studied in detail. Design of Experiment (DOE) analysis showed the “optimized formulation” of the blend. Increase in PPE‐polystyrene (PS) content increased tensile strength and modulus of the blend, followed by a decrease in strain at break. However, EVA had a reverse effect on tensile strength and modulus. Strain at break increased significantly with increasing SEBS content in the blend. Graphical and numerical optimization showed that superior mechanical properties (tensile strength, strain at break and modulus) could be achieved at VA content ～ 50% at a particular loading of EVA. Low MW SEBS was found to be more compatible with the other components of the blend. Mechanical properties of the quaternary blend were marginally affected with change in IV of PPE in the range of 0.33 to 0.46. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Quality characteristics of edible vegetable oil blends

Two edible oil blends, namely groundnut oil:rice-bran oil and mustard oil:rice-bran oil, were prepared in different proportions and stored for a period of three years. Their physicochemical characteristics were determined. The results agreed with expected values except for free fatty acid percents and butyrorefrac-tometer readings, presumably due to rancidity. Fatty acid compositions of the blends were determined and ratios of characteristic fatty acids, like lignoceric to palmitic for groundnut oil:rice-bran oil blends, and erucic to palmitic for mustard oil:rice-bran oil blends, were calculated to identify individual oils in the blend.     

Synthesis and characterization of liquid crystalline polymers containing aromatic ester mesogen and a nonmesogenic ferrocene unit in the spacer

A new series of liquid crystalline polymers containing aromatic triad ester mesogen and 1,1′‐disubstituted ferrocene as a nonmesogenic unit along with polymethylene spacer was synthesized. The polymer was synthesized by a room temperature polycondensation reaction between bis(4‐chloroformyl phenyloxy alkyl ferrocene dicarboxylate) and quinol. The alkyl groups have been varied by an even number of methylene groups with a range from two to ten groups. All the polymers were found to possess liquid crystalline properties. The identification of the mesophase is more transparent with an increase in the spacer. The thermal characteristics were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results reveal that the thermal stability of the polymers was decreased with increasing spacer length. The T_g, T_m, and T_i of the polymers decreased with increasing methylene groups. The incorporation of the ferrocene moiety also has a considerable effect on the glass transition temperature. The char yield of the polymer decreases with an increasing methylene chain length. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3494–3501, 2002     

Performance models of storage contention in cloud environments

We propose simple models to predict the performance degradation of disk requests due to storage device contention in consolidated virtualized environments. Model parameters can be deduced from measurements obtained inside Virtual Machines (VMs) from a system where a single VM accesses a remote storage server. The parameterized model can then be used to predict the effect of storage contention when multiple VMs are consolidated on the same server. We first propose a trace-driven approach that evaluates a queueing network with fair share scheduling using simulation. The model parameters consider Virtual Machine Monitor level disk access optimizations and rely on a calibration technique. We further present a measurement-based approach that allows a distinct characterization of read/write performance attributes. In particular, we define simple linear prediction models for I/O request mean response times, throughputs and read/write mixes, as well as a simulation model for predicting response time distributions. We found our models to be effective in predicting such quantities across a range of synthetic and emulated application workloads.