Effects of Drying Strategies and Microfibrillated Cellulose Fiber Content on the Properties of Foam-Formed Paper

A novel methodology was used to create a highly porous foam-formed paper that is bonded with highly refined cellulose fiber. In this process, cellulose pulp suspension at various consistencies (0.5, 1.0, 1.5, and 2%) was dispersed in water, followed by foam formation under high shear forces in the presence of a surfactant. Various drying methods were used to achieve foam formation. These included freeze-drying (FD), vacuum-dewatered air-drying (VAD), and dewatered freeze-drying (VFD). Increasing the pulp's consistency and changing the drying techniques from freeze-drying to air-drying resulted in a more compact morphological structure and increased density of foam-formed paper samples. Densification of foam-formed samples was measured using a Dynamic Mechanical Analysis (DMA) machine and a sample with densification at lowest strain value was obtained by a 10 wt% addition of microfibrillated cellulose fiber (MFC). At 10 wt% MFC addition, denser foam-formed paper samples with enhanced microstructure were obtained. Air filtration efficiency and acoustic properties of foam-formed paper were also characterized and optimized by the addition of MFC.     

Onset sintering-coarsening-coalescence kinetics of calcite powders

An onset sintering-coarsening-coalescence (SCC) event based on a significant decrease of specific surface area relative to the dry pressed samples after isothermal firing in the 450–600 °C range in air was determined by N₂ adsorption–desorption hysteresis isotherm for submicron-sized calcite powders. The apparent activation energy for such a rapid SCC event was estimated as 57.5 ± 1.0 kJ/mol based on the time for 50% reduction of specific surface area without appreciable phase change of calcite. The minimum temperature to activate the SCC process, as of concern to industrial CaCO₃ applications and natural limestone formation, is 317 °C based on the extrapolation of steady specific surface area reduction rates to null.     

Hydrothermal and entropy generation specifications of a hybrid ferronanofluid in microchannel heat sink embedded in CPUs

The objective of this numerical work is to evaluate the first law and second law performances of a hybrid nanofluid flowing through a liquid-cooled microchannel heatsink.The water-based hybrid nanofluid includes the Fe_3O_4 and carbon nanotubes(CNTs) nanoparticles.The heatsink includes a microchannel configuration for the flow field to gain heat from a processor placed on the bottom of the heatsink.The effects of Fe_3O_4 concentration(φFe_3O_4),CNT concentration(φ_(CNT)) and Reynolds number(Re) on the convective heat transfer coefficient,CPU surface temperature,thermal resistance,pumping power,as well as the rate of entropy generation due to the heat transfer and fluid friction is examined.The results indicated higher values of convective heat transfer coefficient,pumping power,and frictional entropy generation rate for higher values of Re,φFe_3O_4 and φ_(CNT).By increasing Re,φFe_3O_4 and φ_(CNT),the CPU surface temperature and the thermal resistance decrease,and the temperature distribution at the CPU surface became more uniform.To achieve the maximum performance of the studied heatsink,applying the hybrid nanofluid with low φFe_3O_4 and φ_(CNT) was suggested,while the minimum entropy generation was achieved with the application of nanofluid with high φFe_3O_4 and φ_(CNT).     

On the surface morphology of solution annealed Co1−xO–MgO—Effects of directional dislocation exposure and Co1−xO condensation

The sintered Co_1−xO ceramics with or without 20 mol% MgO solid solution in the rock salt type structure were annealed in the temperature range of 400–1500 °C in air for surface morphology development study. Electron microscopic observations indicated the MgO component considerably suppressed the thermal etching and the nucleation of the Co-rich spinel as expected. Surprisingly, prolonged annealing at 1500 °C caused anisotropic development of the {1 1 1}/{1 0 0}-faceted etch pits/hillocks from the cubic crystal system, which can be rationalized by the predominant exposure of 1 1 0 oriented dislocations on the {1 1 1} surfaces. Meanwhile, sublimation–condensation at this temperature caused cube-like Co_1−xO crystallites to deposit preferentially on the (1 0 0) surface following parallel or 45° off crystallographic relationship via Brownian motion of the crystallites.     

电压稳定约束的最优潮流

介绍了近年来考虑电压稳定约束的最优潮流问题的研究新进展.综述了考虑电压稳定约束的最优潮流问题.讨论了在电压稳定约束的最优潮流中考虑高级发电机及负荷模型.最后比较了求解电压稳定约束的最优潮流问题的单阶段法和多阶段法.     

Investigation of transient conduction–radiation heat transfer in a square cavity using combination of LBM and FVM

In this paper, the effect of surface radiation in a square cavity containing an absorbing, emitting and scattering medium with four heated boundaries is investigated, numerically. Lattice Boltzmann method (LBM) is used to solve the energy equation of a transient conduction–radiation heat transfer problem and the radiative heat transfer equation is solved using finite-volume method (FVM). In this work, two different heat flux boundary conditions are considered for the east wall: a uniform and a sinusoidally varying heat flux profile. The results show that as the value of conduction–radiation decreases, the dimensionless temperature in the medium increases. Also, it is clarified that, for an arbitrary value of the conduction–radiation parameter, the temperature decreases with decreasing scattering albedo. It is observed that when the boundaries reflect more, a higher temperature is achieved in the medium and on boundaries.     

On selection of samples in algebraic attacks and a new technique to find hidden low degree equations

The best way of selecting samples in algebraic attacks against block ciphers is not well explored and understood. We introduce a simple strategy for selecting the plaintexts and demonstrate its strength by breaking reduced-round KATAN32, LBlock and SIMON. For each case, we present a practical attack on reduced-round version which outperforms previous attempts of algebraic cryptanalysis whose complexities were close to exhaustive search. The attack is based on the selection of samples using cube attack and ElimLin which was presented at FSE’12, and a new technique called Universal Proning. In the case of LBlock, we break 10 out of 32 rounds. In KATAN32, we break 78 out of 254 rounds. Unlike previous attempts which break smaller number of rounds, we do not guess any bit of the key and we only use structural properties of the cipher to be able to break a higher number of rounds with much lower complexity. We show that cube attacks owe their success to the same properties and therefore can be used as a heuristic for selecting the samples in an algebraic attack. The performance of ElimLin is further enhanced by the new Universal Proning technique, which allows to discover linear equations that are not found by ElimLin.     

Selective separation of mercury(II) using magnetic chitosan resin modified with Schiff's base derived from thiourea and glutaraldehyde

Magnetic chitosan resin was chemically modified by a Schiff's base cross-linker. The interaction of the resin obtained with Hg(II) was studied and uptake value of 2.8 mmol/g was reported. The kinetic and thermodynamic parameters of the adsorption process were estimated. These data indicated that the adsorption process is exothermic and follow the pseudo-second-order kinetics. The selectivity of Hg(II) from other different metal ions in solutions using the studied resin was also reported. Breakthrough curves for the recovery of Hg(II) were studied. The critical bed height was found to be 2.05 cm. The adsorbed Hg(II) was eluted from the resin effectively using 0.1 M potassium iodide.