Near-field imaging and frequency tuning of a high-Q photonic crystal membrane microcavity

We discuss experimental studies of the interaction between a nanoscopic object and a photonic crystal membrane resonator of quality factor Q=55000. By controlled actuation of a glass fiber tip in the near-field of a photonic crystal, we constructed a complete spatio-spectral map of the resonator mode and its coupling with the fiber-tip. On the one hand, our findings demonstrate that scanning probes can profoundly influence the optical characteristics and the near-field images of photonic devices. On the other hand, we show that the introduction of a nanoscopic object provides a low-loss method for on-command tuning of a photonic crystal resonator frequency. Our results are in a very good agreement with the predictions of a combined numerical/analytical theory.Comment: 9 pages, 4 figure

Urgent Need for Reduction in Greenhouse Gas Emissions in Industrial Processes: Are We Past the Tipping Point for Global Warming?

In a previous Guest Editorial (Piacentini and Mujumdar, 2007) and an article (Piacentini and Mujumdar, 2009), we analyzed the relation between climate change and industrial processes, mainly related to drying.Fil: Piacentini, Ruben Dario Narciso. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Mujumdar, A. S. . Minerals, Metals & Materials Technology Centre ; Singapur. Institute of Chemical Technology; Indi

Study on Magnesium based Pyrotechnic Composition as a Priming Charge

A new pyrotechnic composition containing Mg/KNO3/phenolic resin has been formulated and studied in detail for its sensitivity, mechanical and thermal properties, moisture and environmental effects and performance in a closed vessel. The data generated reveal that this composition shows superior performance, better mechanical properties and less susceptibility to moisture as compared to gunpowder. In addition, performance of the composition under extreme hot (45 degree centigrade) and cold (-26 degree centigrade) environmental conditions is not affected at all. Differential thermal analyser results indicate that phenolic resin plays a vital role in reducing the ignition temperature of Mg/KNO/sub 3/ system

A consistency checker for memory subsystem traces

Verifying the memory subsystem in a modern shared-memory multiprocessor is a big challenge. Optimized implementations are highly sophisticated, yet must provide subtle consistency and liveness guarantees for the correct execution of concurrent programs. We present a tool that supports efficient specification-based testing of the memory subsystem against a range of formally specified consistency models. Our tool operates directly on the memory subsystem interface, promoting a compositional approach to system-on-chip verification, and can be used to search for simple failure cases – assisting rapid debug. It has recently been incorporated into the development flows of two open-source implementations – Berkeley’s Rocket Chip (RISCV) and Cambridge’s BERI (MIPS) – where it has uncovered a number of serious bugs.This work was supported by DARPA/AFRL contracts FA8750-10-C-0237 (CTSRD) and FA8750-11-C-0249 (MRC2), and EPSRC grant EP/K008528/1 (REMS).This is the author accepted manuscript

Electro-kinetic technology as a low-cost method for dewatering food by-product

Increasing volumes of food waste, intense environmental awareness, and stringent legislation have imposed increased demands upon conventional food waste management. Food byproducts that were once considered to be without value are now being utilized as reusable materials, fuels, and energy in order to reduce waste. One major barrier to the valorization of food by-products is their high moisture content. This has brought about the necessity of dewatering food waste for any potential re-use for certain disposal options. A laboratory system for experimentally characterizing electro-kinetic dewatering of food by-products was evaluated. The bench scale system, which is an augmented filter press, was used to investigate the dewatering at constant voltage. Five food by-products (brewer’s spent grain, cauliflower trimmings, mango peel, orange peel, and melon peel) were studied. The results indicated that electro-kinetic dewatering combined with mechanical dewatering can reduce the percentage of moisture from 78% to 71% for brewer’s spent grain, from 77% to 68% for orange peel, from 80% to 73% for mango peel, from 91% to 74% for melon peel, and from 92% to 80% for cauliflower trimmings. The total moisture reduction showed a correlation with electrical conductivity (R2¼0.89). The energy consumption of every sample was evaluated and was found to be up to 60 times more economical compared to thermal processing

Heat transfer enhancement by combination of chaotic advection and nanofluids flow in helically coiled tube

Abstract In this study, two passive techniques are simultaneously investigated for heat transfer improvement (i.e. chaotic advection and nanofluids) in coiled heat exchangers. Performance of these two different coils (one with normal configuration and another with chaotic configuration) is numerically analyzed and compared for both water and nanofluid as fluid. Effects of different parameters such as geometry, types of nanofluids, nanoparticle volumetric concentration and Reynolds number on heat transfer and pressure drop are studied. The CuO and Al2O3 base water nanofluids with different nanoparticle concentrations 1-3% were simulated. Equations of conservation of mass, momentum and energy were discretized using a finite element based technique and were solved using ANSYS software. Numerical results showed that heat transfer in the chaotic coil with water as fluid was higher than that in the normal coil with nanofluids at various volumetric concentrations and addition small amount of nanofluid in the chaotic coil flow resulted in significant enhancement of heat transfer

Strong Interactions in Multimode Random Lasers

Unlike conventional lasers, diffusive random lasers (DRLs) have no resonator to trap light and no high-Q resonances to support lasing. Due to this lack of sharp resonances the DRL has presented a challenge to conventional laser theory. We present a theory able to treat the DRL rigorously, and provide results on the lasing spectra, internal fields and output intensities of DRLs. Typically DRLs are highly multimode lasers, emitting light at a number of wavelengths. We show that the modal interactions through the gain medium in such lasers are extremely strong and lead to a uniformly spaced frequency spectrum, in agreement with recent experimental observations.Comment: 13 pages, 4 figures. Supplementary information available at arXiv:0805.449

Power Optimized Transceivers for Future Switched Networks

Network equipment power consumption is under increased scrutiny. To understand and decompose transceiver power consumption, we have created a toolkit incorporating a library of transceiver circuits in 45-nm CMOS and MOS current mode logic (MCML) and characterize power consumption using representative network traffic traces with digital synthesis and SPICE tools. Our toolkit includes all the components required to construct a library of different transceivers: line coding, frame alignment, channel bonding, serialization and deserialization, clock–data recovery, and clock generation. For optical transceivers, we show that photonic components and front end drivers only consume a small fraction (<22%) of total serial transceiver power. This implies that major reductions in optical transceiver power can only be obtained by paying attention to the physical layer circuits such as clock recovery and serial–parallel conversions. We propose a burst-mode physical layer protocol suitable for optically switched links that retains the beneficial transmission characteristics of 8b/10b, but, even without power gating and voltage controlled oscillator power optimization, reduces the power consumption during idle periods by 29% compared with a conventional 8b/10b transceiver. We have made the toolkit available to the community at large in the hope of stimulating work in this field

Low Power Optical Transceivers for Switched Interconnect Networks

The power-consumption of network equipment is under ever-increasing scrutiny. As part of an ensemble project seeking to reduce power-consumption within data-centers1, this work focuses on reducing the power consumption of photonic transceivers for future fast power gated and/or optical switching networks. Utilising an open-source toolkit, we show that Serializer/Deserializer (SERDES) dominates power consumption of traditional optical transceivers. This result has particular implications for the modulation format of future interconnects. At 25 Gb/s line rate, SERDES blocks of PAM-16 and 4-wavelength WDM are shown to have 53% and 79% lower power respectively compared with SERDES of serial NRZ as well as reduced power gating restoration time and energy

Drying kinetic analysis of municipal solid waste using modified page model and pattern search method

This work studied the drying kinetics of the organic fractions of municipal solid waste (MSW) samples with different initial moisture contents and presented a new method for determination of drying kinetic parameters. A series of drying experiments at different temperatures were performed by using a thermogravimetric technique. Based on the modified Page drying model and the general pattern search method, a new drying kinetic method was developed using multiple isothermal drying curves simultaneously. The new method fitted the experimental data more accurately than the traditional method. Drying kinetic behaviors under extrapolated conditions were also predicted and validated. The new method indicated that the drying activation energies for the samples with initial moisture contents of 31.1 and 17.2 % on wet basis were 25.97 and 24.73 kJ mol−1. These results are useful for drying process simulation and industrial dryer design. This new method can be also applied to determine the drying parameters of other materials with high reliability