Numerical Modeling of Heat Transfer for Gas-Solid Flow in Vertical Pipes

A two-fluid model (TFM) based on the kinetic theory was used to study the heat transfer of gas-solid flows in a vertical pneumatic conveyor. A 2-D, vertical pipe with 1.1 m length and 0.017 m internal diameter was chosen as the computation domain. Pipeline has 0.86 m heat transfer section after a 0.28 m developing section. It was found that the voidage has minimum and dimensionless velocities, and temperatures have maximum values in the centerline. A convective heat transfer coefficient decreases along the pipeline, and it was found that the heat transfer coefficient of gas-solid flow is greater than clean gas.     

Enhanced Secure Error Correction Code Schemes in Time Reversal UWB Systems

In this paper, secure channel coding schemes based on turbo codes are suggested for time reversal ultra wideband (TR-UWB) systems. Turbo code has the capability of error correction near Shannon’s limit. Adding security to turbo code is an attractive idea since it could reduce the overall processing cost of providing secure coded data and enjoys the advantages of high-speed encryption and decryption with high security, smaller encoder and decoder size and greater efficiency. The proposed turbo code schemes are labeled as follows: secure puncturing rate, secure frame length, and secure interleaving. Using these scenarios, secure turbo code is defined in a way that the redundant information used for error correction is not pre-determined by the nature of the error correction part of the algorithm but it can be chosen arbitrarily out of the whole set of possible strings. The lower bound of bit error probability for secure turbo code schemes in AWGN and TR-UWB systems are evaluated. Analytical and simulation results show secure turbo code performance is very satisfying. Various crypto-analytical attacks are investigated against these schemes. Based on this analysis, secure turbo code structures changed during the encryption procedure to increase the complexity of linear and differential cryptanalysis. It is seen that the performance of conventional turbo code and random frame length with Poisson distribution are the same. Comparing these schemes shows, secure interleaving approach has the best performance and secure puncturing rate the worst, but the latter provides the most security. The enhanced security of UWB, due to rich multipath nature of UWB channel, could be exploited. Due to space-time focusing property of time reversal UWB, there is an environmental confidentiality (or spatial security), which is additional security for secure turbo code in this system. Using secure turbo code, it is possible to increase the transmission range of UWB systems.     

Developing a new approach for evaluating a de-oiling hydrocyclone efficiency

In this study, a new mathematical approach for evaluating of a de-oiling hydrocyclone efficiency has been developed. This new model uses the flow pattern of disperse phase and the boundary layer separation theory. In the present model unlike the other existing models, it is assumed that the droplet concentration in the radial direction is not uniform within the hydrocyclone. The hydrocyclone separation efficiency is calculated considering the droplet size distribution of the feed and the boundary layer thickness. The present approach considers the effects of droplet load, hydrocyclone geometry, mean droplet size and flow rate on the efficiency. The model is validated by comparison of the calculated separation efficiency with several previous experimental studies.     

Access to New Cytotoxic Triterpene and Steroidal Acid-TEMPO Conjugates by Ugi Multicomponent-Reactions

Multicomponent reactions, especially the Ugi-four component reaction (U-4CR), provide powerful protocols to efficiently access compounds having potent biological and pharmacological effects. Thus, a diverse library of betulinic acid (BA), fusidic acid (FA), cholic acid (CA) conjugates with TEMPO (nitroxide) have been prepared using this approach, which also makes them applicable in electron paramagnetic resonance (EPR) spectroscopy. Moreover, convertible amide modified spin-labelled fusidic acid derivatives were selected for post-Ugi modification utilizing a wide range of reaction conditions which kept the paramagnetic center intact. The nitroxide labelled betulinic acid analogue 6 possesses cytotoxic effects towards two investigated cell lines: prostate cancer PC3 (IC₅₀ 7.4 ± 0.7 μM) and colon cancer HT29 (IC₅₀ 9.0 ± 0.4 μM). Notably, spin-labelled fusidic acid derivative 8 acts strongly against these two cancer cell lines (PC3: IC₅₀ 6.0 ± 1.1 μM; HT29: IC₅₀ 7.4 ± 0.6 μM). Additionally, another fusidic acid analogue 9 was also found to be active towards HT29 with IC₅₀ 7.0 ± 0.3 μM (CV). Studies on the mode of action revealed that compound 8 increased the level of caspase-3 significantly which clearly indicates induction of apoptosis by activation of the caspase pathway. Furthermore, the exclusive mitochondria targeting of compound 18 was successfully achieved, since mitochondria are the major source of ROS generation.     

Effect of molybdenum tri-oxide molar ratio on the optical and some physical properties of tellurite-vanadate-molybdate glasses

Glasses with composition (60 − x)V₂O₅-40TeO₂ − x MoO₃ with 20 ? x ? 60 (in mol%) have been prepared using the usual melt quenching method. The optical absorption spectra of the glasses have been recorded in the wavelength range 300-800 nm. The position of the absorption edge and therefore the optical band gap values were found to be depend on the glass composition. For these glasses, the optical band gap was found to be in the range 2.03-2.86 eV with increasing of MoO₃ concentration. The absorption spectrum fitting method was employed to obtain the energy gap. In this method, only the measurement of the absorbance spectrum of the glass is needed. For each sample, the width of the band tail was determined. Also, the density and glass transition temperature values indicate that the rigidity and packing of the samples increase with increase in MoO₃ concentration as a network former.     

Preparation of Silica-Based Ionic Liquid an Efficient and Recyclable Catalyst for One-Pot Synthesis of α-Aminonitriles

Abstract  

Preparation of N-(3-silicapropyl) imidazolium hydrogen sulfate ([Sipim]HSO₄) as a heterogeneous acidic ionic liquid is described. This heterogeneous ionic liquid was used as catalyst for the synthesis of α-aminonitriles by a one-pot condensation of aldehydes, amines, and trimethylsilyl cyanide at room temperature. Catalyst could be recycled for several times without any additional treatment.     

Experimental and theoretical investigation of shelled corn drying in a microwave-assisted fluidized bed dryer using Artificial Neural Network

Drying characteristics of shelled corn (Zea mays L) with an initial moisture content of 26% dry basis (db) was studied in a fluidized bed dryer assisted by microwave heating. Four air temperatures (30, 40, 50 and 60 °C) and five microwave powers (180, 360, 540, 720 and 900 W) were studied. Several experiments were conducted to obtain data for sample moisture content versus drying time. The results showed that increasing the drying air temperature resulted in up to 5% decrease in drying time while in the microwave-assisted fluidized bed system, the drying time decreased dramatically up to 50% at a given and corresponding drying air temperature at each microwave energy level. As a result, addition of microwave energy to the fluidized bed drying is recommended to enhance the drying rate of shelled corn. Furthermore, in the present study, the application of Artificial Neural Network (ANN) for predicting the drying time (output parameter for ANN modeling) was investigated. Microwave power, drying air temperature and grain moisture content were considered as input parameters for the model. An ANN model with 170 neurons was selected for studying the influence of transfer functions and training algorithms. The results revealed that a network with the Tansig (hyperbolic tangent sigmoid) transfer function and trainrp (Resilient back propagation) back propagation algorithm made the most accurate predictions for the shelled corn drying system. The effects of uncertainties in output experimental data and ANN prediction values on root mean square error (RMSE) were studied by introducing small random errors within a range of ±5%.     

Energy and Quality Attributes of Combined Hot-Air/Infrared Drying of Paddy

The kinetics of combined hot-air/infrared thin-layer drying of paddy was studied. The mechanical quality aspects of paddy kernels dried at different drying conditions were evaluated in terms of percentage of cracked kernels and also required failure force obtained from bending tests. The well-known Artificial Neural Network (ANN) modeling technique was applied to predict the drying time, variations in paddy moisture content, the percentages of cracked kernels, and the values of required failure force of paddy at different drying conditions. The best ANN topologies, transfer functions, and training algorithms were determined for prediction of the mentioned parameters. In addition to the product quality aspects, the specific energy consumption (SEC) was estimated for all drying conditions. The results indicated that application of a low-intensity IR radiation (2000 W/m²), together with lower values of inlet air temperature (30°C) and moderate values of inlet air velocity (0.15 m/s), can effectively improve the final quality of paddy (as a heat-sensitive product) with a reasonable SEC.     

Application of Seismic Attribute Technique to estimate the 3D model of Hydraulic Flow Units: A case study of a gas field in Iran

One of the most important steps in evaluation and development of hydrocarbon reservoirs is the mapping of their characteristics. Nowadays, Seismic Attribute Technique is used to build parameters of hydrocarbon reservoirs in inter-well spaces. One of these parameters is the Flow Zone Index (FZI) that has a significant effect on different stages of evaluation, completion, primary and secondary production, reservoir modeling and reservoir management. The aim of this study is to introduce an equation using seismic attribute and FZI log in wells and then generalize it to predict FZI throughout the reservoir. For this purpose, acoustic impedance (AI) volume as an external attribute was created while internal attributes were computed from seismic data. After that, The best set of attributes was determined using stepwise regression after which seismic attributes were applied to multi-attribute analysis to predict FZI. Then, the attribute map resulted from multi-attribute analysis was used to interpret the spatial distribution of the gas bearing carbonate layers. Finally, the optimum number of Hydraulic Flow Units (HFU) was determined by analyzing the break point in the plot of cumulative frequency of FZI for wells and was generalized all over the reservoir by using the 3D HFU model. The results demonstrated that multi-attribute analysis was a striking technique for HFU estimation in hydrocarbon reservoirs that reduces cost and increases rate of success in hydrocarbon exploration. Distribution of producible hydrocarbon zones along with the seismic lines around the reservoir was characterized by studying this model which can help us in choosing the location of new wells and more economical drilling operations.     

Jitter and metastability analysis and modeling of multilevel bang-bang phase detector

Bang-bang phase detector (BBPD) is one of the essential blocks in the phase-locked loop and clock and data recovery that are used in transceivers. But BBPD has the metastability problem as data change in timing window. It suffers from not only metastability failure but also quantization noise, which causes output jitter. In this paper, the novel model is presented to evaluate the effect of both metastability and jitter on ML-BBPD, and also, it is shown that multilevel BBPD (ML-BBPD) has the improved quantization noise in comparison with the Alexander BBPD. In this model, it is shown that by increasing the oversampling ratio, the quantization noise is decreased, and with the metastability effect and the increment of quantization steps, the characteristic curve of the ML-BBPD becomes more smoothed. Also, the output jitter of ML-BBPD, in which metastability failure is diminished, is modeled. The error function in the model is simulated at system level and compares with the results achieved from simulation at circuit level to prove the validity of the proposed model. The simulation is done in TSMC 65-nm CMOS technology under 1-V supply voltage to compare the characteristic of ML-BBPD for various number of sampling clocks.