Catalyst effectiveness factor for redox model kinetic equation

A generalized isothermal effectiveness factor correlation has been proposed for catalytic reactions whose intrinsic kinetics are based on the redox model. In this correlation which is exact for asymptotic values of the Thiele parameter the effect of the parameters appearing in the model, the order of the reaction and particle geometry are incorporated in a modified form of Thiele parameter. The relationship takes the usual form:

and predicts effectiveness factor with an error of less than 2% in a range of Thiele parameter that accommodates both the kinetic and diffusion control regimes.     

Fundamental Limits of Organic Packages and Boards and the Need for Novel Ceramic Boards for Next Generation Electronic Packaging

The system-on-a-package (SOP) paradigm proposes a package level integration of digital, RF/analog and opto-electronic functions to address future convergent microsystems. Two major components of SOP fabrication are sequential build-up of multiple layers (4–8) of conducting copper patterns with interlayer dielectrics on a board and multiple ICs flip-chip bonded on the top layer. A wide range of passives, wave-guides and other RF and opto-electronic components buried within the dielectric layers provide the multiple functions on a single microminiaturized platform.The routing of future nanoscale ICs with 10,000+ I/Os require multiple build-up layers of ultra fine board feature sizes of 10 m lines/space widths and 40 m pad diameters. Current FR4 boards cannot achieve this build-up technology because of dimensional instability during processing. These boards also undergo high warpage during the sequential build-up process which limits the fine-line lithography and also causes misalignment between the vias and their corresponding landing pads. In addition, the CTE mismatch between the silicon die and the board leads to IC-package interconnect reliability concerns, particularly in future fine-pitch assemblies where underfilling becomes complicated and expensive.This work reports experimental and analytical work comparing the performance of organic and novel ceramic boards for SOP requirements. The property requirements as deduced from these results indicate that a high stiffness and tailorable CTE from 2–4 ppm/C is required to enable SOP microminiaturized board fabrication and assembly without underfill. A novel ceramic board technology is proposed to address these requirements.     

Evaluation of microchamber geometries and surface conditions for electrokinetic driven mixing

The paper presents numerical simulations and analysis of electrokinetic induced mixing in a microchamber in the presence of a fluctuating electric field. Two microchamber geometries are investigated; one plain and the other with strategically placed microbaffles. Both geometries are tested for two extreme surface conditions: a charged surface with induced electrokinesis and another with a neutral or passive surface. Through order of magnitude analysis and numerical experiments it is found that there is an optimal choice of nondimensional frequency and driving potential which leads to the best mixing characteristics. This is given by the relationship Re(eof)/f*< 5 and the condition that f*= O(1), where Re(eof) is the ratio of electrokinetic forces to viscous forces and f*is the nondimensional frequency. Optimal mixing is shown to occur at Re(eof) = 100 and f*= 30. In all cases, best mixing is found to occur when conditions are favorable for the establishment and sustenance of a rotational cell in the chamber driven by the fluctuating ac current. It is shown that the plain microchamber performs better under conditions of surface neutrality while microbaffles enhance mixing substantially in a charged microchamber. In the presence of a rotational cell, the characteristic time scale for mixing is reduced by 2-3 orders of magnitude compared to plain diffusion and is calculated to be between 5 and 10 s for aqueous buffers.     

High-transfer-rate high-capacity holographic disk data-storage system

We describe the design and implementation of a high-data-rate high-capacity digital holographic storage disk system. Various system design trade-offs that affect density and data-rate performance are described and analyzed. In the demonstration system that we describe, high-density holographic recording is achieved by use of high-resolution short-focal-length optics and correlation shift multiplexing in photopolymer disk media. Holographic channel decoding at a 1-Gbit/s data rate is performed by custom-built electronic hardware. A benchmark sustained optical data-transfer rate of 10 Gbits/s has been successfully demonstrated.     

Effect of a high energy electrical pulse on the dynamic stress-strain behavior of a copper alloy

Electromagnetic launchers (EML) dispatch projectiles at extreme velocities (Mach 7-8), using copper/copper alloy rails which are subjected to high rates of loading under a high energy electrical pulse. Results from Split Hopkinson Pressure Bar (SHPB) testing of a copper alloy at high strain rates in the order of 10³ s^− 1 with simultaneous application of a high energy electrical pulse show that the plastic deformation of the copper alloy is increased and a higher degree of work hardening is observed under these conditions.     

Dynamics of growth and weight transitions in a pediatric cohort from India

Background  

There is paucity of information regarding time trends of weight status in children from rapidly developing economies like India. The aim of the study was to analyse the dynamics of growth and weight transitions in a cohort of school children from India.     

A non-quasi-static small-signal model for metal-semiconductor junction diodes

The quasi-static approximation, which assumes that free-carrier propagation delay in the semiconductor device is zero, is often used in device modeling. Consequently, the quasi-static model is adequate only for low-frequency excitations for which free-carrier propagation delay is very small compared to the variation of the excitations. This paper develops a non-quasi-static model suitable for metal-semiconductor junction diodes subjected to small-signal excitation. We show that the predictions of the non-quasi-static model agree more favourably with experimental data taken from Al---Si diodes than that of the quasi-static model, particularly when the frequency of the excitation is high.     

MATLAB modelling and examination of the effect of heat capacity of basin and glass cover on performance of solar still by thermal models

There are numerous researcher-developed mathematical models for single slope passive solar stills which considered the effect of heat capacities of basin and glass cover as negligible. The negligence parameter also plays a vital role in the prediction of the thermal performance of the system. In this paper, an effort has been made to evaluate the cumulative yield, energy efficiency and exergy efficiency of a single slope passive solar still with and without considering the heat capacities of basin and glass cover by using various thermal models such as Dunkle’s model, Zheng Hongfei et al.’s model and Tsilingiris model. These models were studied and compared with and without considering the heat capacity of solar components such as basin and glass cover. The thermodynamic model of this system is developed, and executed in a MATLAB code. By comparing the theoretical values of the cumulative yield, energy efficiency and exergy efficiency, it was found that consideration of the heat capacities of glass cover and basin gives a higher output in all the thermal models.