Spectroscopic evidence for the bulk polymerization of N-vinyl carbazole in the presence of single-walled carbon nanotubes

The bulk polymerization reaction of N-vinylcarbazole (VK) at 70 °C in the presence of single-walled carbon nanotubes (SWNTs) leads to a new composite, whose optical properties were studied by photoluminescence (PL), surface enhanced Raman scattering (SERS) and Fourier transform infrared (FTIR) spectroscopies. A dramatic reduction of the poly(N-vinylcarbazole) (PVK) PL efficiency and a change in the vibrational structure of the PL spectrum of this polymer were observed by adding SWNTs to the synthesis mixture. Steric hindrance effects were evidenced both in SERS spectra of the VK when it interacts mechanico-chemically with SWNTs and in FTIR spectra of the un-doped PVK/SWNTs' composites. Cyclic voltammetry was used to demonstrate the doping process of PVK in PVK/SWNTs' composite.     

A Binary Gas Transport Model Improves the Prediction of Mass Transfer in Freeze Drying

Monitoring partial vapor pressure in the freeze-drying chamber is a cheap, global, and non-intrusive way to assess the end of the primary drying stage. Most existing dynamic freeze-drying models which predict this partial pressure describe mass transfer between the product and the condenser via a mass transfer resistance or a mass transfer coefficient. Experimental evidence suggests that such models can be significantly in error for some values of the sublimation flux, leading to physically inconsistent predictions and possibly incorrect assessment of primary drying termination, with potential risk of product damage if moving to secondary drying and increasing shelf temperature while some ice is still present. Assuming a binary gas transport model for vapor and inert gas leads to improved and consistent predictions and explains the apparent variation of the mass transfer resistance with total pressure, shelf temperature, and product sublimation area.     

Exploiting multi‐cores for efficient interchange of large messages in distributed systems

Conventional data serialization tools assume that objects to be coded are usually small in size so a single CPU core can encode it in a timely manner. In the era of Big Data, however, object gets increasingly complex and larger, which makes data serialization become a new performance bottleneck. This paper describes an approach to parallelize data serialization by leveraging multiple cores. Parallelizing data serialization introduces new questions such as how to split the (sub)objects, how to allocate the available cores, and how to minimize its overhead in practice. In this paper we design a framework for parallelly serializing large objects and analyze the design tradeoffs under different scenarios. To validate the proposed approach, we implemented parallel protocol buffers—the parallel version of Google's Protocol Buffers, a widely‐used data serialization utility. Experimental results confirm the effectiveness of Parallel Protocol Buffers: multiple cores employed in data serialization achieve highly scalable performance and incur negligible overhead. Copyright © 2015 John Wiley & Sons, Ltd.     

Multifunctional formaldehyde resins as curing agent for epoxy resins

Formaldehyde resins (FR) at 1/1/2 molar ratios of monomers (Cl‐phenol/amino monomers/p‐formaldehyde) were synthesized under acid catalysis. The obtained resins were characterized using elemental analysis, FTIR and RMN spectroscopic methods, being used as crosslinking agents for epoxy resin formulations. The curing of epoxy resins with FR were investigated. The glass transition temperature (T_g) and decomposition behavior of crosslinked resins were studied by differential scanning calorimetry (DSC) and thermogravimetric (TGA) techniques. All DSC scans show two exothermic peaks, which implied the occurrence of cure reactions between epoxy ring and amine or carboxylic protons, in function of chemical structures of FR. The crosslinked products showed good thermal properties, high glass transitions, and low water absorption. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Chemical oxidation of residual carbon from ZnAl2O4 powders prepared by combustion synthesis

The removal of carbon residue from ZnAl₂O₄ nanopowders by annealing at 500–800 °C leads to a decrease of specific surface area from 228.1 m²/g to 47.6 m²/g. At the same time, the average crystallite size increased from 5.1 nm to 14.9 nm. In order to overcome these drawbacks, a new solution for removing the carbon residue has been suggested: chemical oxidation using hydrogen peroxide. In terms of carbon removal, a H₂O₂ treatment for 8 h at 107 °C proved to be equivalent to a heat treatment of 1 h at 600 °C. The benefits of chemical oxidation over thermal oxidation were obvious. The specific surface area was much larger (188.1 m²/g) in the case of the powder treated with H₂O₂. The average crystallite size (5.8 nm) of ZnAl₂O₄ powder treated with H₂O₂ was smaller than the crystallite size (8.2 nm) of the ZnAl₂O₄ powder annealed at 600 °C.     

Models and algorithms for coscheduling compute-intensive taks on a network of workstations

The problem of using the idle cycles of a number of high performance workstations, interconnected by a high speed network, for solving computationally intensive tasks is discussed. The classes of distributed applications examined require some form of synchronization among the subtasks, hence the need for coscheduling to guarantee that subtasks start at the same time and execute at the same pace on a group of workstations. A model of the system is presented that allows the definition of an objective function to be maximized. Then a quadratic time and linear space algorithm is derived for computing the optimal coschedule, for the given model and class of applications addressed.