Distributed balanced photodetectors for high-performance RFphotonic links

A novel velocity-matched distributed balanced photodetector with a 50-Ω coplanar waveguide output transmission line has been experimentally demonstrated in the InP-InGaAs material system. Distributed absorption and velocity matching are employed to achieve high-saturation photocurrent. A common mode rejection ratio of 27 dB has been achieved. The RF link experiment conducted at 6.48 GHz shows that the laser intensity noise has been suppressed by more than 17 dB     

On a problem in real-time computing

Proving that a real-time system is capable of handling a peak processing load is a difficult problem, especially when a large number of devices are connected at different priority levels. In this paper we first provide a good solution for the case where the maximum frequency of inputs from each device and the maximum processing times for each input are both known. This is then used to estimate response times and to deal with buffered computation.     

Evaluating combustion,performance and emission characteristics of diesel engine using karanja oil methyl ester biodiesel blends enriched with HHO gas

With a specific end goal to take care of the worldwide demand for energy, a broad research is done to create alternative and cost effective fuel. The fundamental goal of this examination is to investigate the combustion, performance and emission characteristics of diesel engine using biodiesel blends enriched with HHO gas. The biodiesel blends are gotten by blending KOME obtained from transesterification of karanja oil in various proportions with neat diesel. The HHO gas is produced by the electrolysis of water in the presence of sodium bicarbonate electrolyte. The constant flow of HHO gas accompanied with biodiesel guarantees lessened brake specific fuel consumption by 2.41% at no load and 17.53% at full load with increased the brake thermal efficiency by 2.61% at no load and 21.67% at full load contrasted with neat diesel operation. Noteworthy decline in unburned hydrocarbon, carbon monoxide, carbon-dioxide emissions and particulate matter with the exception of NO_x discharge is encountered. The addition of EGR controls this hike in NO_x with a slight decline in the performance characteristics. It is clear that the addition of HHO gas with biodiesel blends along with EGR in the test engine improved the overall characterization of engine.     

Recovery and reuse of TiO<Subscript>2</Subscript> photocatalyst from aqueous suspension using plant based coagulant - A green approach

Separation of TiO₂ from aqueous suspension is a major constraint in heterogeneous photocatalytic water treatment. As an alternative for existing less effective immobilization techniques, the application of plant based coagulant for the recovery and reuse of TiO₂ was investigated for the first time. Aqueous extract derived from seeds of Strychnos potatorum was found to be an effective coagulant for the sedimentation of TiO₂. Further, the potential for recovery and reuse of the sedimented photocatalysts TiO₂, was investigated by photocatalytic degradation of rhodamine B and terephthalic acid tests. The photocatalytic degradation experiments with recovered catalyst obey pseudo first-order kinetics with enhanced photocatalytic activity than that of the pure TiO₂. The investigation of recovered catalysts with XRD, BET, SEM etc., suggests that there is no change in surface and morphological properties when compared with pure TiO₂ and the recovered catalysts are highly suitable for recycle and reuse.     

Effect of pre-soaking treatments on the nutritional profile and browning index of sweet potato and yam flours

The use of sweet potato and yams for product development is hindered by the discoloration from enzymatic and non-enzymatic browning. The effect of pre-soaking treatments on the nutritional changes and browning index (BI) of sweet potato and yam (greater yam and white yam) flours was investigated. Ascorbic acid (AsA), citric acid (CA), acetic acid (AA) and sodium metabisulfite (SMS) were used for soaking at three concentrations (0.25%, 0.50% and 1.00%) and two durations (1 h and 2 h). AsA and SMS removed more starch during soaking of sweet potato, while CA and AA removed more starch from greater yam and CA removed more starch from white yam. Highest removal of reducing sugars was observed in sweet potato in AA, while CA removed maximum reducing sugars from both the yams. Phenol and total free amino acid (TFA) levels were more in SMS treatment than the control sweet potato flour, and least in AA (2 h). Whilst AsA raised the phenols and TFA in greater yam, it removed phenols to the maximum in white yam. Maximum BI was in AsA treatment for the three crops, and least for flour from CA (0.25%) treated yams and AA (1.00%) treated sweet potato.Industrial RelevanceBrowning resulting from enzymatic and non-enzymatic reactions is a major drawback in the processing of sweet potato and yams for product development. The study showed that this could be successfully tackled through soaking the slices in low cost chemicals like acetic acid or citric acid and sodium metabisulfite at low concentrations. The treated slices yielded flour with very low browning indices compared to the respective native flours, which could enhance the potential of such flours in the development of food products.     

Molecular motifs for additives that retard PEO crystallization

We investigate the influence of several bifunctional phenol additives (resorcinol: RES, hydroquinone: HYD, p‐hydroxybenzoic acid: PHBA, and p‐nitrophenol: PNP) on the crystallization of matrix polymer, polyethyleneoxide. We employ solid state Nuclear Magnetic Resonance spectroscopy (NMR), Differential Scanning Calorimetry (DSC), optical microscopy, and Small Angle X‐ray Scattering (SAXS) to investigate crystallization of the additivated PEO and compare with Density Functional Theory (DFT) calculations of additive‐PEO interactions. Additive‐polymer interactions are a function of the functional groups on the additive. Temperature‐dependent spherulitic growth rate measurements from optical microscopy and SAXS lamellar long spacings indicate a distinct trend in the effect of additives on PEO crystallization. Change in PEO crystallization is most pronounced with PNP, followed by PHBA and finally RES and HYD. This trend correlates qualitatively with the binding energies of additive‐PEO interactions from DFT studies. Our results suggest that DFT calculations might be a useful screening tool to evaluate the influence of additives on polymer crystallization. POLYM. ENG. SCI., 57:857–864, 2017. © 2016 Society of Plastics Engineers     

Effect of full and partial-bed configuration on carbon removal performance of biological aerated filters

A comparative study to explore the characteristics of partially and fully packed biological aerated filters (BAFs) in the removal of carbon pollutant, reveals that the partial-bed reactor can perform comparably well with the full-bed reactor. The organic removal rate was 5.34 kg COD m(-3) d(-1) at Organic Loading Rates (OLR) 5.80+/-0.31 kg COD m(-3) d(-1) for the full-bed, and 5.22 kg COD m(-3) d(-1) at OLR 5.79+/-0.29 kg COD m(-3) d(-1) for the partial-bed. In the partial-bed system, where the masses of biomass were only 41-51% of those of the full-bed, the maximum carbon removal limit was still between 5 to 6 kg COD m(-3) d(-1). At organic loadings above 5.0 kg COD m(-3) d(-1), the carbon removal capacity in both systems was limited by the mass and activity of microorganisms. The SRT in the full and partial-bed reactors was primarily controlled by the biomass loss in the effluent and during backwash operation. The SRT was reduced from 20.08 days at OLR 4.18+/-0.20 kg COD m(-3) d(-1) to 7.62 days at OLR 5.80+/-0.31 kg COD m(-3) d(-1) in the full-bed, and from 7.17 days to 4.21 days in the partial-bed. After all, SRT values in the partial-bed were always lower than those in the full-bed.     

Dual-cavity spectrometer for monitoring broadband light extinction by atmospheric aerosols

Abstract

Atmospheric Aerosols affect Earth’s climate directly by scattering and absorbing solar radiation. In order to study the optical properties of aerosols, we developed a broadband cavity-enhanced spectrometer that uses a supercontinuum laser source and a compact spectrometer, to measure simultaneously the extinction coefficient of aerosols over a broad wavelength region from 420 to 540?nm. The system employs a dual cavity approach with a reference and a sample cavity, accounting for changes in gases background and for laser spectral and intensity fluctuations. We tested the system with aerosolized salt particles and polystyrene latex spheres. We performed calculations using Mie theory and found good agreement with the measured extinction. We also found that the extinction coefficient of non-absorbing aerosol favorably compares with the scattering coefficient measured by a nephelometer. Finally, we generated soot particles and found an extinction Ångström exponent in good agreement with values reported in the literature. Wavelength dependent detection limits (1σ) for the instrument at 5?nm wavelength resolution and for an integration time of ～10?min were found to be in the range ～5?Mm^?1 to 13?Mm^?1. The broadband dual-cavity extinction spectrometer is simple and robust and might be particularly useful for laboratory measurements of the extinction coefficient of brown carbon aerosol. The laboratory tests suggest that the prototype is promising for future developments of a field-deployable instrument.

Copyright © 2020 American Association for Aerosol Research     

Preparation and mechanical properties of crosslinked 1,2,3‐triazole‐polymers as potential propellant binders

Thirteen triazole polymers were prepared as potential rocket propellant binders by the reactions of various diacetylenes and diazides. The reaction of E300 dipropiolate ( 1 ) with diazide ( 2 ) obtained from tetraethylene glycol was selected to study the effects of concentration of the tetraacetylene functionalized crosslinker ( 3 ) on the mechanical properties of resulting triazole polymers. The modulus of the polymers increased, whereas the strain (% elongation at failure) decreased with increasing percentage of crosslinker. The resulting triazole polymers also showed that the desired mechanical properties could be obtained by adjusting the crosslinker concentration during the polymerization. Addition of 43 wt % aluminum filler did not significantly affect the strain. The modulus of these triazole polymers was comparable with typical polyurethane elastomeric matrices for rocket propellants. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

P — A logic — a compositional proof system for distributed programs

Summary This paper describes a compositional proof system called P-A logic for establishing weak total correctness and weak divergence correctness of CSP-like distributed programs with synchronous and asynchronous communication. Each process in a network is specified using logical assertions in terms of a presuppositionPre and an affirmationAff as a triple {Pre}S{Aff}. For purely sequential programs, these triples reduce to the familiar Hoare triples. In distributed programs, P-A triples allow the behaviour of a process to be specified in the context of assumptions about its communications with the other processes in the network. Safety properties of process communications, and progress properties such as finiteness and freedom from divergence can be proved. An extension of P-A logic allowing proof of deadlock freedom is outlined. Finally, proof rules for deriving some liveness properties of a program from its P-A logic specification are discussed; these properties have the form Q untilR, whereQ, R are assertions over communication traces. Other liveness properties may be derived from these properties using the rules of temporal logic. Paritosh Kulin Pandya received his Master's degree in Computer Science from the Indian Institute of Technology, Kanpur in 1982, and a Ph.D. from the Tata Institute of Fundamental Research in 1988 where he is currently employed. He has worked as a Research Officer in the Programming Research Group of the Oxford University from 1988 to 1991. Mathai Joseph has since 1985 been professor of Computer Science at the University of Warwick where he leads a group working on developing formal techniques for specifying and implementing realtime and fault-tolerant systems.Supported in part by Visiting Fellowships awarded by the Science and Engineering Research Council (research grant GR/D 90918) and the British Council