Reconfigurable filter bank structures for low complexity digital channelizer using fractional interpolation and MFIR filters with cosine modulation

A low complexity digital reconfigurable filter bank structure which is suitable for digital channelizers in software defined radio is proposed in this paper. In order to get a sharp transition width with low hardware complexity, multiplicative finite impulse response (MFIR) filter is used as the prototype filter in the proposed structure. A masking stage and a channel generation stage constitute the two stages of the proposed structure. In the masking stage, 5 sub-bands are generated by performing cosine modulation technique on the prototype filter. In the channel generation stage, different channels are generated by doing spectral addition/subtraction operations on the interpolated versions of the MFIR filter. Hence, the basic techniques used in the proposed structure are, cosine modulation and fractional interpolation technique. By adjusting a 3-bit control signal, different regions and channels, generated by the two stages, can be obtained. The proposed structure has a hardware complexity, which is much lesser than that of the state-of-the art techniques used for SDR channelizers. The number of channels generated using the proposed structure is also more. The main advantage of the proposed structure is that the hardware complexity of the proposed structure remains the same even if the number of channels is increased.     

Synthesis and Characterization of Platinum Impregnated Zn-ZSM5 Nanocatalysts for Xylene Isomerization Reactions

The influence of zinc to the synthesis of ZSM-5 nanocatalysts (Si/Al?=?24) was investigated in xylene isomerization reactions. Pt was doped through partial vacuum impregnation method on both the parent and Zn-ZSM-5. The synthesized nanocatalyst were characterized by ICP, BET, XRD, FE-SEM, XPS, ²⁷Al MAS NMR, FTIR, NH₃-TPD, and TG analysis. The concentration of weak acid sites of ZSM-5 nanocatalyst slightly decreased while that of strong acid sites increased with the addition of Zn to the nano zeolite structure. Reducing weak acidity resulted in lower coke formation and remarkable catalytic stability in Zn-ZSM-5 nanocatalysts. The precence of Pt on the Zn-containing ZSM-5 illustrated simultaneous high PX yield and high catalytic stability. (0.1 wt%)Pt/(0.8 wt%) Zn-ZSM-5 as an active and stable nanocatalyst for xylene isomerization reactions demonstrated high PX yield (32.6 wt%), high level of EB conversion (68%) and low xylene loss (2.1%).

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Enhancement of gasoline selectivity in combined reactor system consisting of steam reforming of methane and Fischer-Tropsch synthesis

A two-stage, one-dimensional configuration model including the steam reforming of methane (SRM) and Fischer-Tropsch (FT) synthesis has been developed for the production of hydrocarbons. This configuration is used to investigate hydrocarbon product distribution, such as gasoline. The first SRM reactor is fed by methane and steam, and the products are converted to hydrocarbons by the second FT reactor. The model was solved numerically by applying the finite difference approximation, and the set of first-order ODEs was solved in the axial direction. The results show that complete conversion of hydrogen in the second reactor can be achieved although a small amount of carbon monoxide remains. Furthermore, at higher H₂O/CH₄ ratio (and low CO in feed), lower C₂-C₅ yield and selectivity is obtained.     

Keratoconus presenting with bilateral simultaneous acute corneal hydrops

PurposeTo report a case of unknown keratoconus presenting with bilateral simultaneous acute corneal hydrops.MethodsCase report.ResultsA case of a 12-year-old male patient with Leber congenital amaurosis (LCA) presented with sudden whitening and lacrimation for 2 days in both eyes simultaneously. At the initial examination, there were bilateral acute corneal hydrops, enophthalmic eyes and roving nystagmus. Ultrasonography revealed clear crystalline lenses and attached retina. Initial management consisted of topical hypertonic solutions, steroids and artificial tears.ConclusionBilateral simultaneous acute corneal hydrops has not been reported before in the literature. It may be the presenting sign of keratoconus.     

Optimum Coverage/Capacity in MIMO Indoor Channel with Minimum Transmitters

In this paper, we consider a transmitter location finding problem for the best coverage and capacity in an indoor Multi-Input Multi-Output (MIMO) channel. Hence, a multi-objective optimization problem is solved in order to achieve the above targets. A weighted combination of Receive Signal Strength (RSS) and channel capacity is defined as fitness function for this optimization problem. The proposed optimization method contains a jointly designed Ray Tracing Engine (RTE) and Genetic Algorithm (GA). The algorithm is applied on a sample environment which is fully simulated with RTE. The results show that the proposed method perfectly finds the best locations of the minimum number of MIMO transmitters at different weights for RSS and channel capacity.     

Low Reynolds number mixed convection in vertical tubes with uniform wall heat flux

Upward mixed convection of air in a long, vertical tube with uniform wall heat flux has been studied numerically for Re=1000, Re=1500 and Gr?10⁸ using a low Reynolds number k-ε model. The results for the fully developed region identify two critical Grashof numbers for each Reynolds number, which correspond to laminar-turbulent transition and relaminarization of the flow. They also distinguish the Re-Gr combinations that result in a pressure decrease over the tube length from those resulting in a pressure increase. A correlation expressing the fully developed Nusselt number in terms of the Grashof and Reynolds numbers is proposed. It is valid for laminar and turbulent flows in the range 1000?Re?1500, Gr?5×10⁷.     

A hybrid bio-inspired learning algorithm for image segmentation using multilevel thresholding

Multimedia Tools and Applications - In the field of image analysis, segmentation is one of the most important preprocessing steps. One way to achieve segmentation is the use of threshold selection,...     

Transport properties of dilute ammonia-noble gas mixtures from new intermolecular potential energy functions

Previously we have determined the dilute mixture transport properties of slightly polar fluorocarbons using the inverted intermolecular potential energies(Ind.Eng.Chem.Res.45(2006)9211-9223).In the present paper,the corresponding states correlations for reduced viscosity collision integrals were employed to obtain effective un-like interaction potential models for dilute binary mixtures of highly polar molecule ammonia with noble gases. The inverted potentials were fitted to the Morse-Spline-van der Waals(MSV),model potential.The method of least-squares fitting was then applied to identify best consistence force parameters for each ammonia-noble gas mixture,taking advantage of experimental viscosities,diffusion coefficients and thermal conductivities. The proposed potential models were compared with those obtained from other sources,in order to assess the ex-tent of their validity. The potentials were later employed to calculate transport properties of the studied mixtures.Then,results were compared with those reported in the literature,which led to the acceptable agreement.     

Modeling of the Fischer–Tropsch process using a Fe–Cu–K catalyst

In a bid to increase Fischer–Tropsch product selectivity, inorganics substances, such as copper, potassium, and others, were added to the catalyst. Although this approach in Fischer–Tropsch synthesis is very important, it has not been discussed widely. Isothermal product models in this type of synthesis and effective parameters are the same as pressure, while the H₂/CO feed ratio and space velocity have been studied over the spray-dried Fe–Cu–K catalyst by using statistical methods with experimental data. P = 1.0–2.5 MPa, H₂/CO feed ratio = 0.6–2.0, and space velocity = 0.07–0.1 1/h are the range of operating conditions in the spinning basket reactor. The experiment was carried out at a constant temperature of 523 K. The models can predict the reaction's product. Through these the optimal conditions in the reactor models can be determined, while the maximum and minimum amounts of products for oil, wax, and water are obtained under the optimized conditions. The models showed that the interaction between parameters played a key role. The main interactions for products are pressure and space velocity.