Optimum architecture for input queuing ATM switches

An input queueing ATM switch architecture employing the contention resolution called 'scheduling algorithm' is described. A high efficiency of over 90% can be achieved without any considerable increase in the amount of hardware or contention control speed.<>     

Microwell device for targeting single cells to electrochemical microelectrodes for high-throughput amperometric detection of quantal exocytosis

Electrochemical microelectrodes are commonly used to detect spikes of amperometric current that correspond to exocytosis of oxidizable transmitter from individual vesicles, i.e., quantal exocytosis. We are developing transparent multielectrochemical electrode arrays on microchips in order to automate measurement of quantal exocytosis. Here, we report development of an improved device to target individual cells to each microelectrode in an array. Efficient targeting (~75%) is achieved using cell-sized microwell traps fabricated in SU-8 photoresist together with patterning of poly(l-lysine) in register with electrodes to promote cell adhesion. The surface between electrodes is made resistant to cell adhesion using poly(ethylene glycol) in order to facilitate movement of cells to electrode "docking sites". We demonstrate the activity of the electrodes using the test analyte ferricyanide and perform recordings of quantal exocytosis from bovine adrenal chromaffin cells on the device. Multiple cell recordings on a single device demonstrate the consistency of spike measurements, and multiple recordings from the same electrodes demonstrate that the device can be cleaned and reused without degradation of performance. The new device will enable high-throughput studies of quantal exocytosis and may also find application in rapidly screening drugs or toxins for effects on exocytosis.     

Study of oil sorption behavior of filled and structured fiber assemblies made from polypropylene, kapok and milkweed fibers

This article reports on oil sorption behavior of fiber assemblies made up of single natural and synthetic fibers as well as blend of natural and synthetic fibers when tested with high density oil and diesel oil. A series of filled fiber assemblies were prepared from 100% polypropylene, kapok, and milkweed fibers and another series of bonded structured fiber assemblies were prepared from a 70/30 blend of kapok and polypropylene fibers and a 70/30 blend of milkweed and polypropylene fibers. It was observed that the porosity of the fiber assemblies played a very important role in determining its oil sorption capacity. The polypropylene fiber assembly exhibited the highest sorption capacity (g/g) followed by the kapok and milkweed fiber assemblies at porosity <0.98. At higher porosities (above 0.98), polypropylene filled fiber assembly has poor sorption capacity due to large sized inter fiber pore. The kapok and milkweed fibers have intra fiber porosities of 0.81 and 0.83, respectively. All the fiber assemblies showed higher oil sorption capacity with the high density oil as compared to the diesel oil. As the kapok and milkweed fiber have low cellulose content, hence their slow degradation is an advantage in fresh and marine water applications. The good sorption capacity of kapok and milkweed fiber assemblies along with their bio-degradable nature offer great scope for structuring them into fiber assemblies with large porosity and uniform pores to have efficient oil sorbents.     

A new metal-to-metal antifuse with amorphous carbon

We report the development of a new metal-to-metal antifuse with amorphous carbon as the dielectric. Amorphous carbon antifuses have several characteristics making them superior to amorphous silicon antifuses, including lower values of OFF-state leakage current, ON-state resistance, dielectric constant, and breakdown voltage. Most importantly, amorphous carbon antifuses do not show ON-OFF switching, which is observed in amorphous silicon antifuses. A new model is proposed to explain the breakdown mechanism and ON-state reliability of amorphous carbon antifuses     

Effect of nonuniform laser FM response on the performance ofmultichannel heterodyne FSK systems using optical amplifiers

A theoretical analysis is provided to evaluate the performance of optical frequency division multiplexed systems taking into considerations the combined effect of receiver noise, laser phase noise and nonuniform FM response characteristic of a practical DFB laser. To overcome the effect of nonuniform frequency modulation characteristic of semiconductor lasers, two different linecoding schemes are used for the laser driving signal. The crosstalk penalty due to the combined effect of nonuniform FM response and phase noise of lasers is evaluated. The improvement in receiver sensitivity due to optical preamplifier is also estimated. The computed results show that the performance of the system is highly degraded due to the effect of laser nonuniform fm response and can be reduced substantially by using linecoding. Further, there is considerable improvement in receiver sensitivity due to the use of an optical preamplifier in the absence of phase noise. In the presence of phase noise there is a reduction in receiver sensitivity     

A novel low cost texturization method for large area commercial mono-crystalline silicon solar cells

Texturization of mono-crystalline silicon for solar cell fabrication is still a key issue due to consumption of large amount of costly isopropyl alcohol (IPA) in conventional NaOH/KOH solution. The need of IPA arises due to the improvement in the uniformity of pyramidal structures and elimination of spots caused by bubbles sticking on the wafer surface during the texturization process. We investigated a new texturization technique for mono-crystalline silicon solar cells with tribasic sodium phosphate (Na₃PO₄, 12H₂O) solution with much less amount of IPA. The proposed texturization method of this paper is cost effective due to reduction in the consumption of expensive IPA. The cost comparison of our novel texturization approach with conventional NaOH texturization has also been reported in this paper. We are reporting for the first time such a novel approach of using tribasic sodium phosphate for texturization of mono-crystalline silicon surface with which solar cells of efficiency 14–14.8% are fabricated with more than 90% yield.     

Comparison of the Effects of Biodiesel and Mineral Diesel Fuel Dilution on Aged Engine Oil Properties

Dilution of engine oil occurs when fuel is injected late in the combustion cycle to regenerate the diesel particulate filter used for trapping particulate emissions. Fuel dilution reduces oil viscosity and the concentration of engine oil additives, potentially compromising lubricant performance. Biodiesel usage may compound these issues due to its oxidative instability, and its higher boiling point compared to mineral diesel potentially causes it to concentrate more in the oil sump.

In this work, different amounts of mineral diesel and biodiesel (soy methyl ester, SME) were combined with 15W-40 CJ-4 diesel engine oil in laboratory oil aging experiments. Fuel was added and oil samples were withdrawn at periodic intervals. The oils were analyzed using typical oil analysis procedures to determine their condition, and wear evaluations under boundary lubricating conditions were determined using a high-frequency reciprocating rig (HFRR). Results showed that fuel dilution accelerated engine oil degradation, with biodiesel having a larger effect. However, friction remained unchanged with dilution, and wear actually decreased for fuel-diluted oils after 48 h of aging compared to aging without fuel dilution. Examination of the tribofilms by ultraviolet (UV) and visible Raman spectroscopy as well as Auger electron spectroscopy showed that additional carbon-containing components were present on tribofilms formed from fuel-diluted oils. These fuel-derived components may be responsible for the decreased wear observed.     

Combustion Characteristics of Silicon‐Based Nanoenergetic Formulations with Reduced Electrostatic Discharge Sensitivity

This paper details the synthesis and combustion characteristics of silicon‐based nanoenergetic formulations. Silicon nanostructured powder (with a wide variety of morphologies such as nanoparticles, nanowires, and nanotubes) were produced by DC plasma arc discharge route. These nanostructures were passivated with oxygen and hydrogen post‐synthesis. Their structural, morphological, and vibrational properties were investigated using X‐ray diffractometry, transmission electron microscopy (TEM), nitrogen adsorption‐desorption analysis, Fourier transform infrared (FTIR) spectrometry and Raman spectroscopy. The silicon nanostructured powder (fuel) was mixed with varying amounts of sodium perchlorate (NaClO₄) nanoparticles (oxidizer) to form nanoenergetic mixtures. The NaClO₄ nanoparticles with a size distribution in the range of 5–40 nm were prepared using surfactant in a mixed solvent system. The combustion characteristics, namely (i) the combustion wave speed and (ii) the pressure‐time characteristics, were measured. The observed correlation between the basic material properties and the measured combustion characteristics is presented. These silicon‐based nanoenergetic formulations exhibit reduced sensitivity to electrostatic discharge (ESD).