Stepwise fair-share buffering for gossip-based peer-to-peer data dissemination

We consider buffer management in support of large-scale gossip-based peer-to-peer data dissemination protocols. Coupled with an efficient buffering mechanism, system-wide buffer usage can be optimized while providing reliability and scalability in such protocols. We propose a novel approach, stepwise fair-share buffering, that provides uniform load distribution and reduces the overall buffer usage where every peer has a partial view of the system. We report and discuss the comparative performance results with existing buffering approaches as well as random buffering which serves as a benchmark. We present separate evaluations of bufferer selection and gossip-based data dissemination. Reliability, content dissemination time, message delay, buffering delay, and minimum buffer requirements are considered as the key metrics investigated through simulations. The performance of our approach in the case of multiple senders, link failures with multiple bufferers, and scalability to larger networks are investigated. Several power-law and hierarchical overlay topologies are considered. Analytical bounds for reliability of dissemination are also provided.     

Effect of filler content on the structure‐property behavior of poly(ethylene oxide) based polyurethaneurea‐silica nanocomposites

Poly(ethylene oxide) (PEO) based polyurethaneurea‐silica nanocomposites were prepared by solution blending and characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Differential Scanning Calorimetry and tensile testing. The colloidal silica nanoparticles with an average size of 50 nm were synthesized by modified Stöber method in isopropanol. Silica particles were incorporated into three cycloaliphatic polyurethaneurea (PUs) copolymers based on PEO oligomers with molecular weights of 2,000, 4,600, and 8,000 g/mol. Hard segment content of PUs was constant at 30% by weight. Silica content of the PU nanocomposites varied between 1 and 20% by weight. Soft segment (SS) glass transition and melting temperatures slightly increased with increasing filler content for all the copolymers. Degree of SS crystallinity first increased with 1% silica incorporation and subsequently decreased by further silica addition. Elastic modulus and tensile strengths of PU copolymers gradually increased with increasing amount of the silica filler. Elongation at break values gradually decreased in PEO‐2000 based PU copolymer with increasing silica content, whereas no significant change was observed in PUs based on PEO‐4600 and PEO‐8000. Enhancement in tensile properties of the materials was mainly attributed to the homogeneous distribution of silica filler in polymer matrices and strong polymer‐filler interactions. POLYM. ENG. SCI., 58:1097–1107, 2018. © 2017 Society of Plastics Engineers     

A comparative study of the structure-property behavior of highly branched segmented poly(urethane urea) copolymers and their linear analogs

The solid-state structure-property behavior of highly branched segmented poly(urethane urea) (PUU) copolymers and their linear analog was investigated. A limited study of their solution rheological behavior was also undertaken. The linear PUUs were synthesized by the two-step prepolymer method, whereas the oligomeric A₂+B₃ methodology was utilized to synthesize the highly branched materials. The soft segments (SS) were either poly(tetramethylene oxide) (PTMO) or poly(propylene oxide) (PPO). All copolymers utilized in this study, with one exception, contained 28 wt% hard segment (HS) content. DMA, SAXS, and AFM studies indicated that the linear as well as the highly branched PUUs were microphase separated. The SS T_g of the highly branched PUUs was nearly identical to that of their respective linear analogs. However, the linear copolymers exhibited broader and less temperature sensitive rubbery plateaus, both attributed to one or both of two reasons. The first is better hydrogen bonding organization of the HS phase as well as greater HS lengths than in the highly branched analogs. The second parameter is that of a potentially higher chain entanglement for the linear systems relative to the branched analogs. Tapping-mode AFM phase images confirmed the microphase morphology indicated by SAXS and DMA. Ambient temperature strain-induced crystallization was observed in the PUU based on PTMO 2040 g/mol at a uniaxial strain of ca. 400%, irrespective of the chain architecture. Stress-strain, stress relaxation, and mechanical hysteresis of the highly branched copolymers were in general slightly poorer than that of their linear analogs. Ambient temperature solution viscosity of the highly branched materials in dimethyl formamide was substantially lower that that of the linear samples of nearly equal molecular weight.     

Isopropyl alcohol: an unusual, powerful, ‘green’ solvent for the preparation of silicone–urea copolymers with high urea contents

Isopropyl alcohol (IPA) is used as the reaction solvent for the preparation of silicone–urea copolymers. Reactivity of isopropanol with bis(4-isocyanatocyclohexyl)methane (HMDI) was investigated at 23 °C using infrared spectroscopy. Spectroscopic studies indicated very low reactivity of IPA towards HMDI at 23 °C. High molecular weight segmented silicone–urea copolymers were prepared through the reaction of HMDI with aminopropyl and N-methylaminopropyl terminated polydimethylsiloxane (PDMS) oligomers and three different chain extenders, ethylene diamine (ED), hexamethylene diamine (HMDA) and 2-methyl-1,5-diaminopentane (Dytek A). Number average molecular weights of PDMS oligomers varied between 900 and 7000 g/mol, respectively. Reactions were carried out at room temperature in IPA. Silicone–urea copolymers with urea hard segment content between 10 and 42% by weight were prepared. Thermal and mechanical characterization of the copolymers indicated the formation of microphase-separated systems with excellent tensile strengths. Interestingly, structure of the diamine chain extender did not show any influence on the mechanical properties of the homologous series of silicone–urea copolymers.     

Current status of droplet evaporation in turbulent flows

This article reviews the available literature results concerning the effects of turbulence on the transport (heat and mass transfer) rates from a droplet. The survey emphasizes recent findings related specifically to physical models and correlations for predicting turbulence effects on the vaporization rate of a droplet. In addition, several research challenges on the vaporization of fuel droplets in turbulent flow environments are outlined.     

An improved nonlinear thermal model for MV/LV prefabricated oil-immersed power transformer substations

The largest part of the investments of transmission and distribution systems is due to transformers used in changing the voltage level. The operating life of transformers is important due to their considerable economic impact on the power systems. To ensure the economical operation and secured service it is important to have knowledge about the insulation condition, operating life, and loading capacitance of transformer. The most important parameter in transformers life expectancy is the insulation temperature level, which accelerates the rate of aging of the insulation. The modeling of the energy balance and heat transfer of transformer is a major task in transformers thermal modeling. The aim of this paper is to present improved thermal models for transformers loaded at prefabricated MV/LV transformer substations and outdoor situations. The top-oil temperature is studied both for indoor and outdoor transformers and the thermal models proposed for them are compared. Since the thermal transfer is different for indoor and outdoor transformers considering their operating conditions, their thermal models differ from each other. The proposed thermal models are verified by the results obtained from the experiments carried out on typical indoor 30 kV/0.4 kV transformer stations at different operating conditions.     

Effects of Hot Rehydration in the Presence of Hydrogen Peroxide on Microbial Quality, Texture, Color, and Antioxidant Activity of Cold-stored Intermediate-moisture Sun-dried Figs

ABSTRACT: Pectin methylesterase (PME) causes considerable softening in intermediate-moisture (IM) figs rehydrated at 30°C and cold stored at 28% to 29% moisture content. Rehydration of figs at 80°C for 16 min inactivated PME partially (25–30%), but this did not prevent the softening over 3 mo of cold storage. Also, heating did not reduce the microbial load of figs significantly and increased their browning. In contrast, rehydration of figs 1st in 2.5% H₂O₂ at 80°C for 8 min and then in water at 80°C for 8 min reduced the microbial load of IM figs significantly, turned their brown color to yellow-light brown, and maintained their desired textural properties. The residual H₂O₂ in IM figs decomposed in 3 or 1.5 wk by the in situ catalase or by application of the iron (II) sulfate-ascorbic acid residue elimination method, respectively. Hot rehydration did not affect the antioxidant activity of IM figs, but treatment of figs with H₂O₂ increased their antioxidant activity slightly. These results indicate that the hot rehydration of figs in the presence of H₂O₂ and cold storage may be applied to obtain safe and SO₂-free light-colored IM fig products.     

Treatability of cefazolin antibiotic formulation effluent with O3 and O3/H2O2 processes.

The effect of applying ozonation and perozonation to antibiotic cefazolin-Na formulation effluents were investigated in this study. Twenty minutes of ozonation at a rate of 1,500 mg/L-h was observed to remove COD by 38%, whereas a COD removal efficiency of 40% was achieved via H2O2 enhanced ozonation (same conditions + 31.25 mM H2O2). Both of the pretreatment alternatives were monitored to elevate the BOD5/COD ratio from 0.01 to 0.08. The initially inert COD was reduced by 38% using ozonation and by 60% employing H2O2 enhanced ozonation. In terms of the lowest achievable effluent COD levels after bio-treatment, ozonation was observed to yield a residual COD of 205 mgL(-1), while a residual COD of 135 mgL(-1) was involved for perozonation. According to the results of acute toxicity on Phaedactylum tricornutum, ozonated and perozonated samples exhibited more toxicity than the untreated effluent after 4 days. The activated sludge inhibition test demonstrated that both of the pretreatment alternatives efficiently eliminated the inhibition of investigated formulation effluent.     

Design and analysis of a novel zero-voltage-transition interleaved boost converter for renewable power applications

High-efficiency stepping up operation is an important feature of the converters used in renewable power applications due to the low voltage level of photo-voltaic arrays and fuel cells. Decreasing the switching losses of the converters is an effective solution for increasing the converter efficiency, especially in high-power applications. This article presents a novel zero-voltage-transition (ZVT) interleaved dc–dc boost converter that can be used in renewable power sources to reduce switching losses. The auxiliary circuit used in the proposed converter is composed of only one auxiliary switch and a minimum number of passive components without an important increase in the cost and complexity. The main advantage of the proposed converter is that it not only provides ZVT in the boost switches but also provides soft switching in the auxiliary switch. Another advantage of the proposed topology is that the semiconductor devices used in the converter do not have any additional voltage or current stresses. Also, it has a simple structure, low cost and ease of control. In this article, a detailed steady-state analysis of the proposed converter is presented. The theoretical analysis is verified via simulation and experimental studies which are in very good agreement.     

A portable fault-tolerant parallel software MPEG-1 encoder

MPEG video compression is quite difficult to achieve in real time, and hardware solutions for this problem are expensive. We present a portable, fault-tolerant, parallel, MPEG-1 encoder implemented in software. We detail the implementation strategy for the encoder and give performance results on a network of workstations and a massively parallel processor. We also show that our encoder can efficiently adapt to fluctuating processing power typical in workstation networks.