Thermal properties and morphology of isotactic polypropylene/acrylonitrile–butadiene rubber blends in the presence and absence of a nanoclay

A thermoplastic elastomer (TPE) nanocomposite based on polypropylene (PP), acrylonitrile–butadiene rubber (NBR), and a nanoclay (NC) was prepared in a laboratory mixer with a 54/40/6 weight ratio. The effects of NC on the thermal properties, crystalline structure, and phase morphology of the TPE nanocomposite were studied in this work. The results obtained from the nonisothermal crystallization of PP, PP/NBR, and PP/NBR/NC, which was carried out with differential scanning calorimetry, revealed that the overall rate of crystallization of PP decreased with the addition of NBR to PP and increased when NC was incorporated into the nanocomposite. In addition, the crystallite size distribution was more uniform for the PP phase crystallized in the nanocomposite versus the PP itself. Also, although the PP in the reference blend (PP/NBR) crystallized only in the α form, the crystalline structure of the PP incorporated into the nanocomposite was a mixture of α‐ and γ‐crystalline forms. The effects of NC on the phase morphology of PP/NBR blends prepared with three different cooling methods (quenching in liquid nitrogen, cooling between two metal plates at room temperature, and molding at a high temperature in a hot press) were studied. For the samples quenched in liquid nitrogen or cooled between metal plates, a particulate–cocontinuous morphology formed. However, for the samples prepared under a hot press, a laminar‐like morphology was observed. In all three cases, a similar particulate–cocontinuous morphology formed for the reference blend, but the rubber inclusions were always smaller than those of the TPE nanocomposite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of Osmotic Dehydration and Air Drying on Physicochemical Properties of Dried Kiwifruit and Modeling of Dehydration Process Using Neural Network and Genetic Algorithm

In this study, effect of osmotic dehydration and hot air-drying conditions on shrinkage, rehydration capacity, and moisture content of dried kiwifruit was investigated and artificial neural network and genetic algorithm were applied as an intelligent modeling system to predict these physicochemical properties. Kiwifruit slices were immersed in osmotic solutions (30%, 40%, 50%, and 60%) at different temperatures (20, 40, and 60 °C) and were dried at 60, 70, and 80 °C for 5, 6, and 7 h. The results showed that increasing drying time and temperature caused an increase in shrinkage, while rehydration capacity and moisture content were decreased. Neural network model with one hidden layer, four inputs (operating conditions) was developed to predict three outputs (shrinkage, rehydration capacity as a well as moisture content) and genetic algorithm was used to optimize network structure and learning parameters. Artificial neural network models were then tested against an independent dataset and results showed the ability of optimized intelligent model to estimate shrinkage, rehydration capacity, and moisture content with high correlation coefficients (0.94, 0.93, and 0.96, respectively). Moreover, sensitivity analysis indicated that the most sensitive input variable toward such predictions was drying time.     

Rheological and Textural Characteristics of Date Paste

The rheological properties of two commercial date pastes were investigated in the temperature range of 20–70°C. From typical flow behavior curves, it was observed that date pastes exhibited pseudoplastic behavior. The shear stress-shear rate data were fitted using six common rheological models. The Casson model best described the experimental data at all temperatures. The Arrhenius model described successfully the temperature dependence of apparent viscosity of date pastes (R² > 0.99) with an E_a value in the range of 25,392.6–25,485.7 kJ/kmol. The textural attributes measured were: hardness, springiness, gumminess, cohesiveness, chewiness, and adhesiveness for the texture profile analysis test, and firmness, adhesive force, mean load, and total positive area for the Ottawa test. There was a significant difference in textural attributes between two varieties of date paste studied. Texture profile analysis results showed that all parameters obtained for black date pastes were higher than golden date pastes except for springiness and cohesiveness. However, the Ottawa results showed that golden date pastes were firmer and less adhesive than black date pastes.     

Applications of hyperspectral imaging in grains and nuts quality and safety assessment: a review

Quality of foods is generally controlled with traditional methods such as microbiological and chemical tests. However, the necessity of a non-destructive, rapid and accurate on-line method to monitor the product quality and safety is the key topic of many research studies. Hyperspectral imaging (HSI) has emerged as a powerful tool to handle the afore-mentioned goals. It is a novel technique that combines simultaneous advantages of imaging and spectroscopy. HSI is an analytical method that simultaneously delivers chemical, structural and functional information from the sample. This technique can be used to analyze both individual kernels and bulk samples and simultaneously determine quality parameters of grains and nuts. Nuts and grains are nutrient dense foods with complex matrices rich in mono- and poly-unsaturated fatty acids, vegetable proteins, fiber, vitamins, minerals etc. Therefore, nuts and grains are useful dietary sources to decrease the risk of diabetes, cancer and cardiovascular disease. In this paper, recent applications of hyperspectral imaging in quality and safety inspection of nuts and grains such as classification, compositions prediction, texture analysis, and detection of varietal impurities, damages, and infections are reviewed.     

Emission and absorption of optical phonons in Multigate Silicon Nanowire MOSFETs

In this paper we study the influence of emission/absorption processes due to optical phonons on the electrical properties of multigate silicon nanowire transistors. We show that low-energy phonons reduce drain current through backscattering of carriers by emission/absorption processes while high-energy phonons redistribute the current energy spectrum along the nanowire channel through phonon emission without significantly reducing the drain current drive. The influence of emission/absorption is investigated in different multigate silicon FET structures with uniform channel, single impurity, random doping atom distribution and oxide tunnel barriers. A three-dimensional quantum mechanical device simulator based on the NEGF formalism in coupled mode-space approach is used to model electron transport in the presence of optical phonon scattering mechanism. Electron-phonon scattering is accounted for by adopting the self-consistent Born approximation and using the deformation potential theory.     

Fabrication of PEBA/ceramic nanocomposite membranes in gas sweetening

Poly (ether-block-amide) (PEBA)/ceramic nanocomposite hybrid membranes were fabricated by dip-coating of ceramic nanocomposite porous support in PEBA solution and their performance in gas separation (CO₂ and N₂) was examined. Tubular supports were used as substrates for hybrid membranes and Poly (ether-block-amide) was applied as a selective layer. PEBA based on N6 and PEO was synthesized via a two step process. The formation of new ester bond between N6 and PEO in the synthesized copolymer was proved by FT-IR spectroscopy. AFM micrographs indicated that the morphology is the dispersion of high stiffness nanostructured PA domains in the amorphous region of PEO matrix. Experimental results showed that at high concentration of coating solution, a uniform PEBA layer was formed on the porous ceramic support with higher performance for the separation of CO₂/N₂ binary gas mixture.     

A 12-b 5-Msample/s two-step CMOS A/D converter

Two-step flash architectures are an effective means of realizing high-speed high-resolution analog-to-digital converters (ADCs) because they can be implemented without the need for operational amplifiers having either high gain or a large output swing. Moreover, with conversion rates approaching half those of fully parallel designs, such half-flash architectures provide both a relatively small input capacitance and low power dissipation. The authors describe the design of a 12-b 5-Msample/s A/D converter that is based on a two-step flash topology and has been integrated in a 1-μm CMOS technology. Configured as a fully differential circuit, the converter performs a 7-b coarse flash conversion followed by a 6-b fine flash conversion. Both analog and digital error correction are used to achieve a resolution of 12 b. The converter dissipates only 200 mW from a single 5-V supply and occupies an area of 2.5 mm × 3.7 mm     

Performance of optical bit rate limiters with pre- or post-optical amplification

A communication system incorporating a bit rate limiter (BRL) device is analyzed using recently proposed statistical models for power splitters and combiners. We also consider the possible optical attenuation and amplification before and after BRL device. We obtain the total output moment generating function (MGF) of the number of photoelectrons at the receiver end for two possible synchronization procedures. Furthermore, we use saddle-point approximation method to evaluate the system performance considering the effects of shot-noise, thermal noise, and source extinction ratio.     

A 2-GHz, 6-mW BiCMOS frequency synthesizer

A 128-channel pulse-swallow frequency synthesizer includes a 3-mW VCO, a 2.2-mW 16/17 dual-modulus prescaler, a 9-b program counter, and a 7-b swallow counter. The circuit is fully integrated with the exception of the loop-filter capacitor. The ECL prescaler incorporates current sharing and circuit stacking techniques to reduce power consumption. Fabricated in a 1-μm, 20-GHz BiCMOS process, the circuit operates from a 3-V supply and occupies an active area of 0.28 mm²     

Comprehensive power swing detection by current signal modeling and prediction using the GMDH method.

Power swing is an undesirable variation in power flow. This can be caused by large disturbances in demand load, switching, disconnection or reclosing lines. This phenomenon may enter the zones of distance relays and cause relay malfunction leading to the disconnection of healthy lines and undermining network reliability. Accordingly, this paper presents a new power swing detection method based on the prediction of current signal with a GMDH (Group Method of Data Handling) artificial neural network. The main advantage of the proposed method over its counterparts is the immunity to noise effect in signals. In addition, the proposed method can detect stable, unstable, and multi-mode power swings and is capable of distinguishing them from the variety of permanent faults occurring simultaneously. The method is tested for different types of power swings and simultaneous faults using DIgSILENT and MATLAB, and compared with some latest power swing detection methods. The results demonstrate the superiority of the proposed method in terms of response time, the ability to detect power swings of different varieties, and the ability to detect different faults that may occur simultaneously with power swings.