Kinetics studies of nano-structured cobalt–manganese oxide catalysts in Fischer–Tropsch synthesis

The nano-structured cobalt/manganese oxide catalyst was prepared by thermal decomposition of [Co(NH₃)₄CO₃]MnO₄ precursor, and was tested for the Fischer–Tropsch reaction (hydrocarbon forming) in a fixed-bed micro-reactor. Experimental conditions were varied as follow: reaction pressure 1–10 bar, H₂/CO feed ratio of 1–2 and space velocity of 3600 h^?1 at the temperature range of 463.15–523.15 K. On the basis of carbide and/or enolic mechanisms and Langmuir–Hinshelwood–Hougen–Watson (LHHW) type rate equations, 30 kinetic expressions for CO consumption were tested and interaction between adsorption HCO and dissociated adsorption hydrogen as the controlling step gave the most plausible kinetic model. The kinetic parameters were estimated with non-linear regression method and the activation energy was 80.63 kJ/mol for optimal kinetic model. Kinetic results indicated that in Fischer–Tropsch synthesis (FTS) rate expression, the rate constant (k) has been increased by decreasing the catalyst particle size. The catalyst characterization was carried out using different methods including powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area measurements.     

Thermodynamic analysis of fluidized bed drying of carrot cubes

In this study, the energy and exergy analyses of fluidized bed drying of carrot cubes were investigated. Drying experiments were conducted at inlet air temperatures of 50, 60, and 70 °C, BD (bed depths) of 30, 60, and 90 mm and square-cubed carrot dimensions of 4, 7, and 10 mm. The effects of drying variables on energy utilization, energy utilization ratio, exergy loss and exergy efficiency were studied. The energy utilization and energy utilization ratio varied between 0.105–1.949 kJ/s and 0.074–0.486, respectively. The exergy loss and exergy efficiency were found to be in the range of 0.206–1.612 kJ/s and 0.103–0.707, respectively. The results showed that small particles, deep beds and high inlet air temperatures increased energy utilization, energy utilization ratio, and exergy loss due to high value of heat and mass transfer. Also, the exergy efficiency had maximum value when higher drying air temperature, larger CS (cube size) and shorter BD were used for drying experiment.     

Continuous production of fullerenes by pyrolysis of acetylene at a glassy carbon surface

A reactor is described for generating fullerenes from hydrocarbon gas or vapor. Distinguishing features are a thermal system in which the fullerene product is not exposed to destructive energetic photons (as in an arc) and ease of control. Acetylene was chosen as the first feedstock to reduce the hydrogen content. Argon is the carrier gas. The reactor is a radio-frequency induction heated cylinder of glassy polymeric carbon having multiple holes through which the gas mixture passes. Operation as high as 2500 K is possible, but fullerene production is seen only below 1500 K. Preliminary tests give <1% yield, but improvement is expected by manipulation of the temperature, dwell time at temperature, feedstock species and partial pressure. A hydrogen scavenger may also be useful.     

Comparison of artificial neural network and combined models in estimating spatial distribution of snow depth and snow water equivalent in Samsami basin of Iran

Snow water equivalent (SWE) is a key parameter in hydrological cycle, and information on regional SWE is required for various hydrological and meteorological applications, as well as for hydropower production and flood forecasting. This study compares the snow depth and SWE estimated by multivariate linear regression (MLR), discriminant function analysis, ordinary kriging, ordinary kriging-multivariate linear regression, ordinary kriging-discriminant function analysis, artificial neural network (ANN) and neural network-genetic algorithm (NNGA) models. The analysis was performed in the 5.2 km² area of Samsami basin, located in the southwest of Iran. Statistical criteria were used to measure the models’ performances. The results indicated that NNGA, ANN and MLR methods were able to predict SWE at the desirable level of accuracy. However, the NNGA model with the highest coefficient of determination (R ² = 0.70, P value < 0.05) and minimum root mean square error (RMSE = 0.202 cm) provided the best results among the other models. The lower SWE values were registered in the east of study area and higher SWE values appeared in the west of study area where altitude was higher.     

Bit rate of HSDPA in tunnel’s cigar-shaped microcells

This paper presents the bit rate of High Speed Downlink Packet Access (HSDPA) mode for cigar-shaped microcells deployed at tunnels. The hybrid propagation loss model with log-normal shadowing is used to calculate the signal to interference plus noise ratio taking into account the expected value and the variance of the interference. A model of ten cigar-shaped microcells is used in the analysis. The effect of the propagation parameters on the HSDPA performance (coverage and bit rate) is studied. It is found that, with a sector transmitted power of 1 W, a sector with a range of 1 km can be deployed with the worst case propagation parameters values. It is shown that it is impossible to support more than 6 HSDPA codes for full coverage within the sector what ever the power assigned to the HSDPA service.     

Design,Synthesis, and Fabrication of Chitosan/Hydroxyapatite Composite Scaffold for Use as Bone Replacement Tissue by Sol–Gel Method

Journal of Inorganic and Organometallic Polymers and Materials - Injuries or bone defects are phenomena that are harmful to human health. In the field of bone scaffold tissue engineering,...     

Investigation of nanosized alumina-binder feedstock rheology for ceramics injection molding (CIM) and survey spark plasma sintering of output green body to obtain transparent alumina

The purpose of this work is to optimize the feed containing alumina-binder nanoparticles for ceramics injection molding to create transparent alumina parts. In this research, two Alumina with and without MgO as sintering aid fabricated via the spark plasma sintering method. Feed fluidity, fracture toughness, density, IR, and visible transmission of SPSed bodies of the sintered pieces were measured. Furthermore, a pin on the disc test was used on the disk to examine the alumina friction coefficient. The results of feed rheology showed that the sample prepared at 90°C had the best conditions as a pseudoplastic fluid for the ceramic injection molding (CIM) method. The results showed that a combination of CIM and spark plasma sintering (SPS) methods cause more visible transmission than conventional SPS of alumina nanopowder. Also, the fracture toughness and hardness of as-obtained transparent alumina were in the range of 3.6 MPa m^0.5 and 20.1 MPa, respectively. The wear rate of the as-obtained transparent sample (4.5 × 10⁻⁷ mm³/N m) was proportional to the alumina grain size (1–4 μm).     

Failure mechanism of polyamide 66 nanofiber yarns under fatigue and static tensile loading

This work aims at fractography of polyamide 66 nanofiber yarns. The yarns are produced with three twist levels via electrospinning. In order to study the fracture modes of nanofiber yarns, fatigue, and static tensile tests including monotonic, low cycle fatigue, and postcyclic monotonic tensile tests are performed. It is observed that the catastrophic failure of yarns is associated with axial splitting in the three categories. The nanofibers within the yarn structure show a ductile fracture and buckle after tensile stress release. In comparison of postcyclic monotonic tensile tests with other categories, nanofibers show severe plastic buckling in response to release of the same applied force. Fractography studies reveal that twisting causes construction of a layered structure in the yarns which is similar to the ideal yarn structure as well. Applying cyclic loading causes the separation of these structural layers which is more considerable under higher number of cycles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41925.     

Towards Quantifying Interfacial Adhesion in the Ternary Blends with Matrix/Shell/Core-Type Morphology

We quantified interfacial adhesion in ternary blends with matrix/shell/core microstructure based on mechanical properties assessments. Various HDPE-based ternary blends containing PA-6/EVOH core/shell droplets were prepared by changing composition and processing temperature. The theoretical predictions of tensile properties were compared with experimental data; thereby considerable shift in experimental modulus from lower to upper limit observed over a 10°C increase in melting temperature. This confirmed the impact of blending temperature on matching the predicted values with experimental data. The meaningful trend observed in tensile characteristics of ternary blends simply gives an understanding of interfacial adhesion degree in ternary blend showing matrix/shell/core microstructure.