A modified thermodynamic insight to deliquescence of a void‐containing nanocrystal confirmed by MD simulation

Existence of voids in crystalline structures can affect their physical and chemical properties considerably. When the size of the crystal reaches to nanoscale, experimental determination of its void fraction is difficult. In this work, a molecular dynamics approach is introduced to find equilibrium void fractions of a simple cubic (CsCl) and fcc (KCl) nanocrystals by determination of their deliquescence relative humidity (DRH) for different sizes and void fractions and extrapolation of the results to the bulk limit. To confirm the simulation results, the size dependency of DRH to the nanoparticle size was studied thermodynamically by inclusion of size‐dependent density of water nanodroplet which leads to a simple homographic equation. This method proposes the equilibrium void percents of CsCl and KCl nanoparticles to be 10 and 15%, respectively, which are obtained by extrapolation of the results to the bulk limit. The success of obtained Möbius function was also confirmed by fitting it to experimental data for deliquescence of NaCl nanoparticles which implies the importance of considering density of water nanodroplet as a size dependent quantity. Also, using the mentioned thermodynamic approach, void dependency of deliquescence for the nanoparticles was found to be as a quasi‐linear trend which is compatible with the simulation results. It is noticeable that the approach used this work for determination of equilibrium void fraction is only valid if the utilized force fields are accurate. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4066–4077, 2016     

Evaluation of Fracture Mechanisms in Al-Si Metal Matrix Nanocomposites Produced by Three Methods of Gravity Sand Casting,Squeeze Casting and Compo Casting in Semi-Solid State

Silicon - Magnetic stirring is considered to be the most useful stirring method in semi-solid casting processes which doesn’t have the restrictions of the mechanical stirring. In this...     

Remote sensing of salinity in the San Francisco Bay Delta

Salinity of the San Francisco Bay Delta has been studied for the past seven decades. There is a significant gradient in salinity within this estuarine system that influences the growth and distribution of phytoplankton as well as the abundance and migration of shrimp and fish population. Several government agencies which have jurisdictions over this area are attempting to gather extensive data for effectively monitoring of this estuary. Repetitive remotely sensed data acquired from Landsat may be considered by these agencies as having the potential to provide a cost-effective method for gathering and processing water quality related data. In this study, Landsat multispectral scanner (MSS) data and color and color infrared photographs acquired from a U-2 aircraft were combined with surface measurements for salinity mapping of the San Francisco Bay Delta. The salinity measurements and U-2 photography were obtained simultaneously and coincident with landsat overpass. A regression model was developed between the surface truth data and Landsat digital data for 29 preselected sample sites and was then extended to the entire study area. The results included a salinity map of the study area and the statistical summaries. The results were in general agreement with the reported distribution of salinity values in the literature for the same time of the year. Based on the results and the associated analyses of natural color and color infrared photographs and Landsat color composite imagery, it was concluded that: (1) it was virtually impossible, at least within this test site, to establish any quantitative judgement regarding the salinity values by visual interpretation of the imagery; and (2) the present study constitutes the first effort to successfully use Landsat digital data for salinity mapping, by means of digital processing, for this geographic area.     

Electrospray modeling of highly viscous and non‐Newtonian liquids

The electrohydrodynamic spraying of highly viscous and non‐Newtonian aqueous solutions of sodium alginate were experimentally modeled with high direct‐current electric fields. A prototype electrospray setup comprising a nozzle connected to a high‐voltage counter electrode connected to earth and a curing facility to solidify the droplets was used. The main aim was initially set to extend the knowledge of the electrospray to highly viscous liquids, where shear thinning was the main rheological feature of fluid flow through the nozzle of the spray system. To model the process, the effects on the size of beads of the electric field strength, nozzle diameter, flow rate, and the material properties of density, viscosity, surface tension, and electrical conductivity were characterized. The size distribution of the beads was obtained after the droplets were cured in a calcium chloride solution with an image analyzer system. The rheological study, carried out on different concentrations of alginate solution (i.e., 1–3 w/v %), showed a significant reduction in the viscosity as a function of the shear rate. Considering the shear‐thinning behavior of the solutions, in the modeling we applied the viscosity at the operational shear rate in the nozzle. Four dimensionless groups were introduced to obtain the relationship between the dimensionless group representing diameter and the other groups in the dripping and jet modes with statistical analysis of the experimental data. The proposed equations correlated the size of beads within ±10% deviations as compared to the experimental results. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Optimization of the fermentation conditions and partial characterization for acido-thermophilic <Emphasis Type="Italic">α</Emphasis>-amylase from <Emphasis Type="Italic">Aspergillus niger</Emphasis> NCIM 548

A high performance thermostable α-amylase at low pH values has been synthesized. Sugarcane bagasse was hydrolyzed in a dilute acid solution and utilized as carbon source for the growth of Aspergillus niger strain NCIM 548. Glucose, xylose and arabinose with the ratio of 1.0: 0.9: 0.3 (w/w/w) were detected in the hydrolyzate by HPLC analysis. Optimization of the fermentation conditions for α-amylase production was performed by varying four influential parameters such as Sugarcane bagasse hydrolyzate (SBH), NH₄Cl, pH and incubation time using a central composite design (CCD) under response surface methodology (RSM). The optimum values of SBH, NH₄Cl, pH and incubation time were 20.49, 2.34 g/l, 5.65 and 76.67 h, respectively. The acido-thermophilic enzyme showed maximum stability at 70°C and pH value of 4. The rate constant, K _m and maximum reaction rate, V _max were 18.79 g/l and 15.85 g/l·min, respectively.     

Modeling of Estuarne Chlorophyll a from an Airborne Scanner

Near simultaneous collection of 34 surface water samples and airborne multispectral scanner data provided input for regression models developed to predict surface concentrations of estuarine chlorophyll a. Two wavelength ratios were employed in model development. The ratios werechosen to capitalize on the spectral characteristics of chlorophyll a, while minimizing atmospheric influences. Models were then applied to data previously acquired over the study area thre years earlier. Results are in the form of color-coded displays of predicted chlorophyll a concentrations and comparisons of the agreement among measured surface samples and predictions basedon coincident remotely sensed data. The influence of large variations in fresh-water inflow to the estuary are clearly apparent in the results. The synoptic view provided by remote sensing is another method of examining important estuarine dynamics difficult to observe from in situ sampling alone.     

A 2.4-GHz CMOS transceiver for Bluetooth

A fully integrated CMOS transceiver tuned to 2.4 GHz consumes 46 mA in receive mode and 47 mA in transmit mode from a 2.7-V supply. It includes all the receive and transmit building blocks, such as frequency synthesizer, voltage-controlled oscillator (VCO), power amplifier, and demodulator. The receiver uses a low-IF architecture for higher level of integration and lower power consumption. It achieves a sensitivity of -82 dBm at 0.1% BER, and a third-order input intercept point (IIP3) of -7 dBm. The direct-conversion transmitter delivers a GFSK modulated spectrum at a nominal output power of 4 dBm. The on-chip voltage controlled oscillator has a close-in phase-noise of -120 dBc/Hz at 3-MHz offset     

Experimental investigation of the effects of different chemical absorbents on wetting and morphology of poly(vinylidene fluoride) membrane

Membrane wetting is of one the most important factor that affects the CO₂ absorption efficiency in membrane contactors due to the increase of mass transfer resistance. In this study, the effects of different absorbents on the wettability of poly(vinylidene fluoride) membranes were investigated. Four absorbents including monoethanolamine, potassium carbonate–piperazine (PZ), potassium carbonate–monoethanolamine, and methyldiethanolamine–PZ were applied to investigate the effects of different absorbents on membrane wetting. Membrane properties before and after contact with absorbents were investigated using methods of thermogravimetric analysis, Fourier transform infrared spectroscopy, electron scanning microscope, and contact angle measurements. The results revealed that methyldiethanolamine and mixed absorbents containing methyldiethanolamine caused the most morphological changes in membrane. The results showed that reduction percentages of contact angle for water, K2CO3/PZ, K2CO3/MEA, MEA, and MDEA/PZ solutions were 14.52, 16.9, 21.19, 23.7, and 28.33, respectively, after 30 days immersion. The results also showed that potassium carbonate–PZ solution caused the least change in membrane wettability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45543.