Off‐grid DoA estimation method of wideband signals

In this paper, an off‐grid direction of arrival (DoA) estimation method is proposed for wideband signals. This method is based on the sparse representation (SR) of the array covariance matrix. Similar to the time domain DoA estimation methods, the correlation function of the sources was assumed to be the same and known. A new measurement vector is obtained using the lower‐left triangular elements of the covariance matrix. The DoAs are estimated by quantizing the entire range of continuous angle space into discrete grid points. However, the exact DoAs may be located between two grid points; therefore, this estimation has errors. The accuracy of DoA estimation is improved by the minimization of the difference between the new measurement vector and its estimated values. Simulation results revealed that the proposed method can enhance the DoA estimation accuracy of wideband signals.     

The effect of fluorine content on the mechanical properties of poly (?-caprolactone)/nano-fluoridated hydroxyapatite scaffold for bone-tissue engineering

In this study, the effect of fluorine content on the mechanical properties of the novel poly (?-caprolactone)/nano-fluoridated hydroxyapatite nanocomposite scaffolds was investigated. Poly (?-caprolactone)/nano-fluoridated hydroxyapatite (PCL-FHA) scaffolds were produced by solvent casting/particulate leaching method. The fluoridated hydroxyapatite nanopowders had a chemical composition of Ca₁₀(PO₄)₆OH_2−xF_x (where x values were selected equal to 0.5, 1, 1.5 and 2.0). Various weight percentages (10, 20, 30 and 40) of the FHA were added to the PCL. Sodium chloride (NaCl) particles having diameter of 300-500 μm were used as porogen. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to identify the phase structure and functional groups of obtained scaffolds. Mechanical properties of the prepared scaffolds were also determined. Results showed that the compressive strength of scaffolds increases with decreasing the weight percent of fluorine in FHA.     

Sulfonated Beet Pulp as Solid Catalyst in One-Step Esterification of Industrial Palm Fatty Acid Distillate

In this research a new heterogeneous catalyst has been prepared for biodiesel production. The catalyst was prepared by sulfonating industrial sugar waste. Unlike homogeneous catalysts, which require further purification and separation from the biodiesel production reaction media, this inexpensive synthetic catalyst does not need to go through an additional separation process. This advantage consequently minimizes the total application costs. The catalyst was prepared by partially carbonizing sugar beet pulp at 400 °C. The carbonization product was then sulfonated with concentrated H₂SO₄ vapor in order to produce a solid catalyst. The prepared catalyst was used in the esterification reaction between palm fatty acid distillate (PFAD) and methanol. The effects of the temperature, methanol/PFAD ratio, reaction time and catalyst dosage on the efficiency of the production were individually investigated. The optimum biodiesel production occurred at 85 °C, a reaction time of 300 min, catalyst dosage of 3 g and methanol/PFAD ratio of 5:1 (mol/mol), lowering the acid value from 198 to 13.1 (mg KOH/g oil) or the equivalent, with a fatty acid methyl ester yield of around 92 %. The results suggest that the synthesized inexpensive catalyst is useful for biodiesel production from PFAD.     

A new blend of polymeric encapsulation of azithromycin by spray-drying with a pH responsive in drug release

The microencapsulation of macrolides with polymers has been reported to retard the release of the drug in oral cavity. However, these methods are unable to control drug release in gastrointestinal tract. The aim of the present study was to investigate the effect of formulation of a new polymeric encapsulation of azithromycin which is suitable for both masking and sustained release usage. Eudragit E100 and polyethylene glycol (PEG) 4000 were chosen as the barrier coatings. The spray drying technique was used to obtain the microcapsules containing azithromycin. To obtain the initial results, the effects of several parameters were evaluated. A 3:2:1 ratio of E100:PEG 4000:azithromycin at pH 6 gave the best coating condition. Thermogravimetric analysis and IR analysis data confirmed the encapsulation of azithromycin inside polymers. The encapsulated drug was released in different rates from the particles by changing the pH (1.7 and 7.4). An analysis of the kinetic release properties indicates that the release of the drug is a combination of swelling and diffusion mechanism. The synergistic cooperation between polymers and drug due to the existence of several hydrogen bonding is supposed to influence the pH-responsive property of the encapsulated drug. Moreover, the use of mixtures of E100 and PEG 4000 appears to offer a good balance between cost and efficiency.     

A hybrid fuzzy-ontology based intelligent system to determine level of severity and treatment recommendation for Benign Prostatic Hyperplasia

This paper deals with application of fuzzy intelligent systems in diagnosing severity level and recommending appropriate therapies for patients having Benign Prostatic Hyperplasia. Such an intelligent system can have remarkable impacts on correct diagnosis of the disease and reducing risk of mortality. This system captures various factors from the patients using two modules. The first module determines severity level of the Benign Prostatic Hyperplasia and the second module, which is a decision making unit, obtains output of the first module accompanied by some external knowledge and makes an appropriate treatment decision based on its ontology model and a fuzzy type-1 system. In order to validate efficiency and accuracy of the developed system, a case study is conducted by 44 participants. Then the results are compared with the recommendations of a panel of experts on the experimental data. Then precision and accuracy of the results were investigated based on a statistical analysis.     

Microstructural development in a low carbon Ti-microalloyed steel during deformation within the ferrite region

Microstructural evolution of ferrite in a low carbon Ti-microalloyed steel, during deformation within the ferrite region, was investigated by using torsion testing. Warm deformation characteristics of ferrite were studied by analyzing of its flow curves, optical microstructures and electron back-scattered diffraction maps. The results show that an unstable sub-boundaries network forms and then these transform into high angle boundaries, with further straining. It was found that the occurrence of continuous dynamic recrystallization is responsible for the development of very fine ferrite grains with high angle boundaries.     

[Hmim][HSO4], a Green and Recyclable Acidic Ionic Liqiud Medium for the One‐Pot Nitration of TADB to HNIW

An efficient and mild procedure for the one‐pot preparation of CL‐20 from TADB in the presence of the Brønsted acidic ionic liquid 1‐methylimidazolium hydrogen sulfate [Hmim][HSO₄] as catalyst was developed. The ionic liquid was stable during the reaction process and could also be reused several times with steady activity. In order to optimize the process parameters to obtain higher yield and purity, a study was carried out with variation of the ionic liquids and some parameters like temperature, mole ratio of [Hmim][HSO₄] and nitric acid. This procedure may be a practical alternative to the existing procedures to meet the nees of academics as well as industry.     

Effect of two-step severe plastic deformation on the microstructure and mechanical properties of commercial purity titanium

The present work investigates the microstructural and mechanical properties of commercial purity titanium after processing by a two-step severe plastic deformation procedure entailing warm equal channel angular pressing (ECAP) followed by cold rolling at liquid nitrogen temperature (LNT). The effect of subsequent cold rolling at room temperature is also investigated for comparison. After 10 passes of ECAP, an ultrafine-grained structure with average grain size of 213 nm was achieved. Subsequent cold rolling at LNT led to further refinement and decreased the grain size to 114 nm. Under these conditions, the material displayed high tensile strength of 995 MPa and high elongation to failure of 23%. These promising mechanical properties were interpreted in terms of characteristics of the microstructure: grain refinement, increased dislocation density, and a high fraction of high angle grain boundaries.     

A Multimode Transmultiplexer Structure

This paper introduces a multimode transmultiplexer (TMUX) structure capable of generating a large set of user-bandwidths and center frequencies. The structure utilizes fixed integer sampling rate conversion (SRC) blocks, Farrow-based variable interpolation and decimation structures, and variable frequency shifters. A main advantage of this TMUX is that it needs only one filter design beforehand. Specifically, the filters in the fixed integer SRC blocks as well as the subfilters of the Farrow structure are designed only once. Then, all possible combinations of bandwidths and center frequencies are obtained by properly adjusting the variable delay parameter of the Farrow-based filters and the variable parameters of the frequency shifters. The paper includes examples for demonstration. It also shows that, using the rational SRC equivalent of the Farrow-based filters, the TMUX can be described in terms of conventional multirate building blocks which may be useful in further analysis of the overall system.