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731.
Vahid Shabafrooz Sudheer Bandla Masoud Allahkarami Jay C. Hanan 《Journal of Polymer Research》2018,25(12):256
Nanocomposites made of poly(ethylene terephthalate) (PET) and graphene nanoplatelets (GNPs) were fabricated through micro-compounding and micro-injection molding. With an objective of improving the interactions between GNP sheets and PET chains, PET pellets were ground into a fine powder. PET pellets and powders were mixed with GNPs at 2%, 5%, 7.5%, and 10% (wt.%), molded to fabricate the nanocomposites, and then tested using several analytical characterization tools. Mechanical testing showed greater improvement through powder mixing, resulting in a 58% increase in the elastic modulus of the nanocomposites at 10% weight fraction. Thermal behavior of the nanocomposites was evaluated through differential scanning calorimetry (DSC), and it was observed that addition of GNPs into PET powders at 10% increased the crystallinity of the PET 50%. Confocal microscopy confirmed that mixing GNP with PET powders results in a more uniform distribution of the GNPs in the matrix compared to the mixture with PET pellets. X-ray diffraction (XRD) analysis confirmed the presence of GNPs with preferred orientation within the PET matrix. 相似文献
732.
Wireless sensor networks as the key infrastructure of the new networking paradigm are vulnerable against different kinds of attacks. Therefore, ensuring a secure communication between the sensor nodes is important. One of the most critical issues in this regard is the key distribution mechanism. Due to the random deployment of the sensors in the target area, key pre-distribution is a promising approach, in which a list of keys, so-called key-ring, is pre-distributed to each sensor node before deployment. To establish a secure communication, two nodes must share a common key from their key-rings. In this paper, we consider a hybrid key pre-distribution approach based on the symmetric design. We propose a new scheme, which is a modification of the hybrid symmetric design in order to improve the connectivity and resilience. Considering the trade-off between resilience and connectivity, we introduce a new parameter based on the application requirement. The experimental results and analytical analysis approve the efficiency of our proposed approach and introduced parameter. 相似文献
733.
Hossein Barzegar Samaneh Shahsavarifar Vahid Vatanpour Majid Masteri-Farahani 《应用聚合物科学杂志》2021,138(31):50764
Poly(ethersulfone) (PES) is one of the polymers most widely used for the fabrication of ultrafiltration or nanofiltration membranes in various applications, but its membrane suffers from fouling. In this study, preparation, characterization, and performance of PES nanocomposite membrane comprising peroxopolyoxometalate nanoparticles was studied to provide improved permeability and anti-fouling properties. The high oxygen ratio of the PW4 nanoparticles could enhance the hydrophilicity of the membranes. The PW4 nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction analyses. The mixed matrix membranes were fabricated using a non-solvent induced phase-separation method. The fabricated membranes were characterized using atomic force microscopy, attenuated total reflection, SEM, EDX mapping, total average porosity, thermogravimetric analyze, and water contact angle experiments. The dye flux and rejection, pure water permeability and anti-fouling properties of the membranes were investigated. All of the membranes blended by different contents of the PW4 nanoparticles presented better performance compared to the unmodified membrane. The filtration performance of the membranes in reactive green 19 (RG19) and reactive yellow 160 (RY160) dye separation showed that all of the PW4 blended membranes possessed dye rejection greater than 86% and 96% for RY160 and RG19, respectively. The reusability test using bovine serum albumin (BSA) protein and RG19 dye solutions in five cycle experiments presented good reproductivity of the PW4 blended membranes. The PES membrane containing 1 wt% of PW4 nanoparticles showed the highest flux recovery ratio (75%) as well as reduced irreversible fouling ratio (8%) through BSA protein filtration. 相似文献
734.
In this work, several experiments were conducted at isobaric and isothermal condition in a CSTR reactor to study the kinetics of methane hydrate formation and dissociation. Experiments were performed at five temperatures and three pressure levels (corresponding to equilibrium pressure). Methane hydrate formation and dissociation rates were modeled using mass transfer limited kinetic models and mass transfer coefficients for both formation and dissociation were calculated. Comparison of results, shows that mass transfer coefficients for methane hydrate dissociation are one order greater than formation conditions. Mass transfer coefficients were correlated by polynomials as relations of pressure and temperature. The results and the method can be applied for prediction of methane production from naturally occurring methane hydrate deposits. 相似文献
735.
In this research, zinc sulfide nanoparticles (NPs) with various morphologies such as spherical, flower-like, microspheres decorated with nanoparticles and nanorods were synthesized by two distinct, simple and efficient methods. These approaches include reflux and hydrothermal methods. Zinc nitrate hexahydrate ().6H2O were used as Zn source and thioacetamide (TAA) was used as S source. The effects of TAA to zinc ion mole ratio were investigated on the morphology, particle size, optical and photocatalytic properties of ZnS nanocrystals. In hydrothermal synthesis with increasing Zn2+:TAA mole ratio from 1:1 to 1:2 dendrite-like nanocrystals changed to semi-spherical nanoparticles with average particle size 50–60?nm, with different effect as photocatalysts. But any change at morphology were didn’t observed with changing Zn2+:TAA mole ratio from 1:1 to 1:30 in the reflux method. In the reflux method with increasing in Zn2+:TAA mole ratio, dispersed semi-sphere nanoparticles were observed. The synthesized nanocrystals were characterized by infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. XRD analysis and FESEM images show that the size of synthesized ZnS NPs is in the range of 15–25?nm. UV–vis spectra showed that by increasing the amount of sulfur source and increasing the reaction time, shifted towards lower wavelengths, and the band gap was in the range of ~ 3.9–4.8?eV for all of the samples. Also, photoluminescence (PL) analysis showed by increasing particle size and degree of agglomeration, emission intensity () decreased. The photocatalytic activity of the as-prepared samples has been compared for the photocatalyst degradation of reactive blue 21. The sample with low Pl intensity has higher photocatalyst efficiency. 相似文献
736.
Protein Corona Influences Cell–Biomaterial Interactions in Nanostructured Tissue Engineering Scaffolds 下载免费PDF全文
Vahid Serpooshan Morteza Mahmoudi Mingming Zhao Ke Wei Senthilkumar Sivanesan Khatereh Motamedchaboki Andrey V. Malkovskiy Andrew B. Goldstone Jeffrey E. Cohen Phillip C. Yang Jayakumar Rajadas Daniel Bernstein Y. Joseph Woo Pilar Ruiz‐Lozano 《Advanced functional materials》2015,25(28):4379-4389
Biomaterials are extensively used to restore damaged tissues, in the forms of implants (e.g., tissue engineered scaffolds) or biomedical devices (e.g., pacemakers). Once in contact with the physiological environment, nanostructured biomaterials undergo modifications as a result of endogenous proteins binding to their surface. The formation of this macromolecular coating complex, known as “protein corona,” onto the surface of nanoparticles and its effect on cell–particle interactions are currently under intense investigation. In striking contrast, protein corona constructs within nanostructured porous tissue engineering scaffolds remain poorly characterized. As organismal systems are highly dynamic, it is conceivable that the formation of distinct protein corona on implanted scaffolds might itself modulate cell–extracellular matrix interactions. Here, it is reported that corona complexes formed onto the fibrils of engineered collagen scaffolds display specific, distinct, and reproducible compositions that are a signature of the tissue microenvironment as well as being indicative of the subject's health condition. Protein corona formed on collagen matrices modulated cellular secretome in a context‐specific manner ex vivo, demonstrating their role in regulating scaffold–cellular interactions. Together, these findings underscore the importance of custom‐designing personalized nanostructured biomaterials, according to the biological milieu and disease state. The use of protein corona as in situ biosensor of temporal and local biomarkers is proposed. 相似文献
737.
Nabih Alaoui Vahid Meghdadi Jean‐Pierre Cances 《International Journal of Communication Systems》2015,28(6):1001-1016
Optimization of large sensor network architecture in order to improve the overall system performance at the end processing station is an important challenge. Many architectures have been designed to optimize the bit error rate. Conventionally, this optimization is performed by inserting relays between sensors and destination. These relays insert redundant information by mixing the incoming streams from sensor nodes hence creating parity check information which is very useful to help decode the transmit information from sensors. The goal is to combine network and channel coding to match network on graph to code on graph, and this is called adaptive network coded cooperation. Compared with the previous works in the field, we propose a new transmit protocol based on the use of beamforming technique, which is very efficient in terms of throughput and is fully compatible with the physical network coding (PNC) principles. Furthermore, we propose a distributed coding scheme where the relay, the destination, and the sensors are all equipped with repeat accumulate (RA) channel code structures. The relay has a special RA structure to suit the need of the PNC multiple‐access channel. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
738.
Alireza Khataee Behrouz Vahid Behzad Behjati Mahdieh Safarpour Sang Woo Joo 《Chemical Engineering Research and Design》2014
The treatment of C.I. Acid Blue 5 solution by electrochemical process was studied under recirculation mode with a cathode containing multi walled carbon nanotubes in the presence of sodium sulfate electrolyte. Comparison of electro-Fenton and photoelectro-Fenton processes at pH 3.0 revealed that 23.04 and 98.25% of the dye was decolorized at 60 min, respectively. The kinetic of dye removal by photoelectro-Fenton process was studied with nonlinear regression analysis. A kinetic model was developed for estimation of pseudo-first order rate constant (kapp) as a function of operational parameters including initial concentration of the dye (10–50 mg/L), flow rate (5–20 L/h), pH (3–9), initial concentration of Fe3+ (0.05–0.2 mM) and applied current (0.05–0.45 A). The calculated results, which were obtained from kinetic model, were in consistent with the experimental data (R2 = 0.9934). The calculated and experimental data were applied for prediction of the electricity consumption in decolorization processes. 相似文献
739.
A first approximation method for smoke detector placement based on design fire size,critical velocity,and detector aerosol entry lag time 总被引:1,自引:0,他引:1
Elman Brozovsky graduate student Vahid Motevalli Richard L. P. Custer 《Fire Technology》1995,31(4):336-354
An analog light-scattering-type smoke detector was tested in a wind tunnel at various low velocities. The air flow in the wind tunnel contained an aerosol concentration that resulted in a high ambient optical density, simulating smoke well above threshold optical detector density. The objective of this research was to determine the lag time to alarm, t, associated with difficulty of smoke entry into a detector. A critical velocity was identified for the smoke detector, below which the lag time increased exponentially with decreasing velocity. Increased lag time results in the detector responding unacceptably late—or not at all—even when ambient obscuration is well above limits defined in UL standard tests.A preliminary method for placing smoke detectors has been developed, based on a user-defined design fire size and the detector aerosol-entry lag time. The preliminary method applies only to flaming fires producing smoke, with the detector far from a wall and mounted on smooth ceilings. The critical velocity value used in the examples in this paper applies only to the smoke detector configuration tested in this work, at the evaluated sensitivity setting, with the optical densities reached using the generated artificial smoke. Any variation in detector housing, design, operation principle, or application with different aerosols requires specific tests to determine a different critical velocity.This paper provides the basis for further development of a smoke detector placement method based on a design fire size and the proposed detector critical velocity concept. It does not presume to report a unique critical velocity for all smoke detectors, but suggests that such a value may indeed exist, but with differing values among different smoke detectors. 相似文献
740.
Hashem Moradmand Ziyabar Mahnaz Sinaie Ali Payandeh Vahid Tabataba Vakili 《Signal, Image and Video Processing》2014,8(7):1263-1272
Recently, arithmetic coding has attracted the attention of many scholars because of its high compression capability. Accordingly, in this paper, a method that adds secrecy to this well-known source code is proposed. Finite state arithmetic code is used as source code to add security. Its finite state machine characteristic is exploited to insert some random jumps during source coding process. In addition, a Huffman code is designed for each state to make decoding possible even in jumps. Being prefix-free, Huffman codes are useful in tracking correct states for an authorized user when he/she decodes with correct symmetric pseudo-random key. The robustness of our proposed scheme is further reinforced by adding another extra uncertainty by swapping outputs of Huffman codes in each state. Several test images are used for inspecting the validity of the proposed Huffman finite state arithmetic coding (HFSAC). The results of several experimental key space analyses, statistical analyses, key and plaintext sensitivity tests show that HFSAC with a little effect on compression efficiency provides an efficient and secure method for real-time image encryption and transmission. 相似文献