Experiments Design for Hardness Optimization of the Ni-Cr Alloy Electrodeposited by Pulse Plating

The hardness of the Ni-Cr alloy which is electrodeposited in chloride solution,is optimized by design of experiment method(central composite design).Various parameters were evaluated in order to find significant factors in this process.Frequency,duty cycle,current density and temperature were selected as efective factors.Analyses of variance(ANOVA)were performed on the results of the designed experiments.The best model which can predict the hardness of the Ni-Cr alloy electrodeposits was found whereas the frequency and quadratic behaviour of the current density were the most significant model terms.Serious interaction of the current density with frequency and duty cycle also were found in this model.Finally the optimum conditions of the factors for obtaining the maximum hardness of the Ni-Cr alloy were found.Ni-Cr alloy with hardness828 HV(electrodeposited with frequency 63 Hz,current density 1800 A/m2,duty cycle 75%and temperature31℃ bath)were assessed as the optimum deposit.The deposit under the optimum condition was investigated by scanning electron microscopy(SEM),EDX analysis,polarization method and microhardness.     

Artificial latex-based opals prepared by spin casting of monodispersed nano particles

Organoclay nanocomposites based on cyclic olefin copolymer (COC) with various contents of layered silicate nanoparticles were prepared via melt blending. The influence of processing conditions and nanoclay content on solid state viscoelastic and melt rheological properties as well as thermal degradation behavior was studied. The state of dispersion was investigated using X-ray diffraction technique which showed a strong dependence on composition, where an exfoliated morphology was identified in high nanoclay loading. Besides, the processing conditions, i.e., screw rotation speed and mixing time were also found to strongly influence the state of nanophase dispersion. The rheological investigations revealed a remarkable increase in storage shear modulus and complex viscosity values upon nanoclay incorporation. Furthermore, dynamic mechanical analysis gave an evidence of increasing stiffness after nanoclay was added into COC matrix; however, no detectable change in glass transition peak was brought about. The results from thermogravimetry also exhibited a rising trend in thermal stability values as nanophase organoclay was incorporated, for which the random chain scission was suggested as the prevailing mechanism based on a theoretical analysis.     

A nickel hexacyanoferrate and poly(1-naphthol) hybrid film modified electrode used in the selective electroanalysis of dopamine

A mixed-valent nickel hexacyanoferrate and poly(1-naphthol) hybrid (NiHCF–PNH) film was prepared on a gold (Au) electrode by a galvanostatic method, which led to stable and homogeneous hybrid film. The film was characterized using scanning electronic microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. This electrode showed excellent catalytic properties toward dopamine (DA) detection, using cyclic voltammetry and differential pulse voltammetry methods. The electrocatalytic oxidations of DA at different electrodes, such as a bare Au electrode or a poly(1-naphthol)/Au-, or NiHCF–PNH/Au-modified electrode, were investigated in a phosphate buffer solution (pH 7). Interestingly, the NiHCF–PNH-modified electrode facilitated the oxidation of DA, but it did not responded to other electroactive biomolecules, such as ascorbic acid and uric acid_. The DA electrochemical sensor exhibited a linear response from 0.1 to 4.3 μM (R² = 0.9984) and from 4.3 to 9.6 μM (R² = 0.9969), with a detection limit of 2.1 × 10^?8 M, and a short response time (3 s) for DA determination. In addition, the NiHCF–PNH-modified electrode exhibited distinct advantages by its simple preparation, specificity, and stability.     

Recognition of the Communication Signals Using Particle Swarm Optimization and Support Vector Machine Based on the Multi-Resolution Wavelet Analysis

Automatic recognition of the communication signals plays an important role for various applications. This paper presents a novel intelligent system for recognition of digital communication signals. This system includes three main modules: feature extraction module, classifier module and optimization module. In the feature extraction module, multi-resolution wavelet analysis is proposed for extraction the suitable features. In the classifier module, a multi-class support vector machine (SVM) based classifier is proposed as the multi-class classifier. For optimization module, a particle swarm optimization algorithm is proposed to improve the generalization performance of the recognizer. In this module, it is optimized the SVM classifier design by searching for the best value of the parameters that tune its discriminant function, and upstream by looking for the best subset of features that feed the classifier. Simulation results show that the proposed hybrid intelligent system has high performance even at very low signal to noise ratios (SNRs).     

Bilateral Markov mesh random field and its application to image restoration

This paper introduces bilateral Markov mesh random field to overcome the shortcomings of the conventional Markov random fields in image modeling. These shortcomings consist of (a) the computational intractability of such fields when expressing the image probability function in the form of the Gibbs distribution function, and (b) the formulation of the image probability function via the product of low-dimensional densities at the expense of obtaining non-symmetrical image models. The properties of bilateral Markov mesh random field are presented and used to derive an image model to address the above shortcomings. As an application, a framework for image restoration is then provided. Restoration results based on this new bilateral Markov mesh random field are compared to the conventional fields to demonstrate its effectiveness.     

Numerical study of blowing and suction slot geometry optimization on NACA 0012 airfoil

The effects of jet width on blowing and suction flow control were evaluated for a NACA 0012 airfoil. RANS equations were employed in conjunction with a Menter’s shear stress turbulent model. Tangential and perpendicular blowing at the trailing edge and perpendicular suction at the leading edge were applied on the airfoil upper surface. The jet widths were varied from 1.5% to 4% of the chord length, and the jet velocity was 0.3 and 0.5 of the free-stream velocity. Results of this study demonstrated that when the blowing jet width increases, the lift-to-drag ratio rises continuously in tangential blowing and decreases quasi-linearly in perpendicular blowing. The jet widths of 3.5% and 4% of the chord length are the most effective amounts for tangential blowing, and smaller jet widths are more effective for perpendicular blowing. The lift-to-drag ratio improves when the suction jet width increases and reaches its maximum value at 2.5% of the chord length.     

Recent Advancements in Polythiophene-Based Materials and their Biomedical,Geno Sensor and DNA Detection

In this review, the unique properties of intrinsically conducting polymer (ICP) in biomedical engineering fields are summarized. Polythiophene and its valuable derivatives are known as potent materials that can broadly be applied in biosensors, DNA, and gene delivery applications. Moreover, this material plays a basic role in curing and promoting anti-HIV drugs. Some of the thiophene’s derivatives were chosen for different experiments and investigations to study their behavior and effects while binding with different materials and establishing new compounds. Many methods were considered for electrode coating and the conversion of thiophene to different monomers to improve their functions and to use them for a new generation of novel medical usages. It is believed that polythiophenes and their derivatives can be used in the future as a substitute for many old-fashioned ways of creating chemical biosensors polymeric materials and also drugs with lower side effects yet having a more effective response. It can be noted that syncing biochemistry with biomedical engineering will lead to a new generation of science, especially one that involves high-efficiency polymers. Therefore, since polythiophene can be customized with many derivatives, some of the novel combinations are covered in this review.     

A jet mixing study in two phase gas-liquid systems

All studies concerned with jet mixing have been focused on liquid phase systems and no studies have been found on jet mixing for gas-liquid two phase systems. In the present study the use of jet fluid as a mixer in gas-liquid systems was proposed. Further by installing an experimental setup, the mixing behavior of liquid phase was studied. Gas flow and jet flow are injected to the mixing vessel countercurrently. In this study, the effect of jet injection, location of the conductivity probe, aeration rate and jet Reynolds number on the mixing time are investigated. The created flow pattern was extracted for each condition and the results often analyzed on the basis of them. It is observed that, for low aeration rates, the injection of jet decreases the mixing time considerably. By increasing the aeration rate, the difference in mixing times between the two cases of jet injection and without jet is reduced. Results also show that the closer the probe is to encounter location of the jet and airflow, the lower the mixing time obtained. Dependence of mixing time on the probe location decreases by increasing the mixing intensity and eliminating dead zones. It is obtained, on the basis of Re_j and the amount of jet travelling in the vessel, increasing the aeration rate has different effects on the performance of mixing. Generally, four different trends for the variation of mixing time with increasing the aeration rate are observed.     

Growth and optical properties of ZnO–In2O3 heterostructure nanowires

ZnO–In₂O₃ heterostructure nanowires were grown on a Si (111) substrate using the thermal evaporation method. Scanning electron microscopy results showed that the ZnO nanowires had spherical caps. The X-ray diffraction (XRD) pattern and energy-dispersive X-ray (EDX) spectrum indicated that these caps were In₂O₃. An analysis of the early growth process revealed that indium oxide might have played a self-catalytic role. Therefore, it was plausible that the vapor–liquid–solid mechanism (VLS) was responsible for the growth of the ZnO–In₂O₃ heterostructure nanowires. The optical properties of the products were characterized using a photoluminescence (PL) technique. The PL results for the ZnO–In₂O₃ heterostructure nanowires showed a strong peak in the ultraviolet region as a result of the near band emission and a negligible peak for the visible emissions that occurred as a result of the defects. Based on these PL results, it was found that the In₂O₃ nanostructures not only introduced the caps at the tips of the ZnO nanowires but also partially passivated the nanowire surfaces, leading to an improved near band edge emission and the suppression of the defect luminescence.     

Synthesis,characterization, and supercapacitor studies of manganese (IV) oxide nanowires

One-dimensional manganese (IV) oxide (MnO₂) (～20 nm in average diameter) were synthesized by cathodic electrodeposition and heat treatment. The mechanism of electrodeposition and nanowire formation were discussed. The product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR). Nanowires with varying lengths and diameters were found in TEM and SEM images of the sample. The results of N₂ adsorption–desorption analysis indicated that the BET surface area of the MnO₂ nanowires was 157 m² g^?1 and the pore size distributions were 2.5 and 4.5 nm. The electrochemical performances of the prepared MnO₂ as an electrode material for supercapacitors were evaluated by cyclic voltammetry and galvanostatic charge/discharge measurements in a solution of 0.5 M Na₂SO₄. The higher specific capacitance of 318 F g^?1 and good capacity retention of 86% were achieved after 1000 charge–discharge cycles had been observed for the MnO₂ nanowires electrode.