Transient liquid phase bonding of Sn–Bi solder with added Cu particles

The aim of this study was to apply the transient liquid phase (TLP) bonding technique to low-temperature Sn–Bi-based solders to enable their use in high-temperature applications. The microstructure of the eutectic Sn–Bi solders with and without added Cu particles was investigated with the solders sandwiched between two Cu substrates. The flux of the Cu atoms successfully consumed the Sn phase and resulted in the formation of Sn–Cu intermetallic compounds and a Bi-rich phase in the solder joint. This caused the melting point of the solder joint to increase from 139 to 201 °C. The results of this study show the potential of using low-temperature solders in high-temperature applications. This study also provides new insight into the advantages of using particles in the TLP bonding process.     

Optimal tuning of linear controllers for power electronics/power systems applications

This paper presents a new method for tuning various linear controllers such as Proportional-Integral (PI), Proportional-Integral-Derivative (PID) and Proportional-Resonant (PR) structures which are frequently used in power electronics and power system applications. The linear controllers maintain a general structure defined by the Internal Model Principle (IMP) of control theory. The proposed method in this paper is twofold. The first perspective uses the well-known concept of the Linear Quadratic Regulator (LQR) to address the problem as a regulation problem. The Q matrix of the LQR design is then finely adjusted in order to assure the desired transient response for the system. The second perspective redefines the LQR in order to add capability to address the optimal tracking problem and is then generalized to systems with more than two states. These methods are then applied to two specific examples, one in an uninterruptible power supply (UPS) inverter system and the other one in a distributed generation (DG) system. In these examples, the tuning of PR and PI controllers is studied in great detail. These proposed design methods provide an easy and algorithmic procedure without jeopardizing stability or robustness. These tuning methods can also be utilized for linear state-space realization of any power converters. Both examples are supported via simulation and the results, which confirm analytical derivations, are presented and discussed.     

Synthesis and Structural Characterization of Two New Nano-Coordination Compounds Based on Mercury(II) NN Donor Schiff Base

Two new nano mercury(II) coordination compounds, [Hg₂(μ-L1)(μ-I)₂I₃]_n (1) and [Hg(L2)(I)₂] (2) {L1?=?(E)-N′-(pyridin-2-ylmethylene)isonicotinohydrazide and L2?=?(E)-N′-(1-(pyridin-2-yl)ethylidene)isonicotinohydrazide} have been synthesized by a sonochemical method. The new nano-structures were characterized by scanning electron microscopy, X-ray powder diffraction, elemental analysis and IR spectroscopy. The compounds were also characterized by single crystal X-ray diffraction and the results indicate a 1D fishbone-like structure containing dinuclear units for 1 and a mononuclear structure for 2. In coordination polymer 1, the two Hg(II) centers are four coordinate into a chain-axis and also in the terminal linkages. In complex 2, the Hg(II) center is four coordinate. The chains of polymer 1 interact with each other through π–π stacking interactions which create a 3D framework.     

Novel porous organic triazine‐based polyimide with high nitrogen levels for highly efficient removal of Ni(II) from aqueous solution

In this study, a porous organic triazine‐based polyimide (PPI network) was prepared from 2,4,6‐tris(hydrazino)‐s‐triazine and 3,4,9,10‐perylenetetracarboxylic dianhydride. TGA, Fourier transform infrared spectroscopy, field emission SEM, XRD and a nitrogen sorption study confirmed the PPI network structure. Then, the synthesized PPI network was used to evaluate Ni²⁺ ion removal from aqueous solution and the effective parameters on adsorption functions of Ni²⁺ ions such as initial concentration, contact time and pH of the solution in batch adsorption experiments was studied. The results showed that the maximum adsorption capacity (q_m) of Ni²⁺ ions was 36.1 mg g^?1 in only 30 min with a pH of 7. The kinetics and adsorption isotherm were identified to be better fitted by the pseudo‐second‐order model and the Langmuir model, respectively. Based on the results, the proposed adsorbent has good potential for removing Ni²⁺ ions from aqueous solutions. © 2019 Society of Chemical Industry     

Flow rate measurement of individual oil well using multivariate thermal analysis

Flow measurement of individual oil wells mainly consisted of using test-separator units with many limitations including time and cost consuming, uncertainty of well isolation, and need to closing the co-line wells. The multivariate regression of thermogravimetric data were used to predict the accurate productivity of oil wells using a single sample-point at the blend-oil pipe-line. The results revealed that the Weighted Sum Model was appropriate for oils, which their thermal traces were significantly different from each other. The thermogravimetric data was arranged in a two-way array by taking the number of oil samples and the thermal signal intensities as columns and rows, respectively. The data matrix was decomposed using the commend of Matrix Left Division in MATLAB and the rank of individual oil wells was determined as a column vector. The error vector corrected the blend equation by considering the catalytic pyrolysis and eutectic point in higher and lower temperatures, respectively. The model predicted the accurate productivity of individual oil wells in an offshore oil field after 2010.     

Electrospinning/electrospray of polyvinylidene fluoride (PVDF): piezoelectric nanofibers

Polyvinylidene fluoride (PVDF) is one of the most studied polymer systems that exhibits piezoelectric, pyroelectric, and ferroelectric properties. It is well known that PVDF is able to crystallize in four different forms that involve three different chain conformations, namely α, β, γ, and δ phases. Among the four polymorphs, the β-phase has the largest spontaneous polarization per unit cell and thus exhibits the highest electro active properties. In the past few decades, many researches have been done to increase the β-phase content in PVDF using various processing techniques and additives. One of these processing methods is electrospinning/electrospray with organic/inorganic additives, nanoparticles or carbon nanotubes. Material and structural analyses on fabricated nanofibers using instruments such as X-ray diffraction, Fourier transform infrared, Differential Scanning Calorimetry, and Scanning Electron Microscope as the characterizations of piezoelectric nanofibers are carried out. This article attempts to have an overview on the electrospinning process of PVDF as a piezoelectric polymer, method of characterization of its β-phase and its application as a nanogenerator.     

Rogue waves generation in a left-handed nonlinear transmission line with series varactor diodes

We investigate the electromagnetic wave behavior and its characterization using collective variables technique. Second-order dispersion, first- and second-order nonlinearities, which strongly act in a left-handed nonlinear transmission line with series varactor diodes, are taken into account. Four frequency ranges have been found. The first one gives the so-called energetic soliton due to a perfect combination of second-order dispersion and first-order nonlinearity. The second frequency range presents a dispersive soliton leading to the collapse of the electromagnetic wave at the third frequency range. But the fourth one shows physical conditions which are able to provoke the appearance of wave trains generation with some particular waves, the rogue waves. Moreover, we demonstrate that the number of rogue waves increases with frequency. The soliton, thereafter, gains a relative stability when second-order nonlinearity comes into play with some specific values in the fourth frequency range. Furthermore, the stability conditions of the electromagnetic wave at high frequencies have been also discussed.     

Numerical Study of Pressure Drop and Thermal Characteristics of Al2O3–Water Nanofluid Flow in Horizontal Annuli

In this paper the results of numerical study of the mixed convection heat transfer of Al₂O₃–water nanofluid in a horizontal annuli are presented. Steady, laminar flows in symmetric configurations are considered. Single-phase fluid approach is adopted for nanofluid modeling. The governing equations are discretized using the finite-volume method. A SIMPLE-like algorithm has been applied for pressure–velocity coupling on the collocated arrangement. In order to validate the code performance, the numerical results are compared with those available in the literature and good agreement is achieved. The effects of some important parameters such as nanoparticle volume fraction, aspect ratio, Grashof number, and heat flux ratio are studied and discussed in detail. In general, it is observed that the local Nusselt number increases with increase in nanoparticle concentration, Grashof number, and radius ratio. However, when increasing the nanoparticle concentration there are considerable increments in pressure drop and pumping power, which are not desirable. On the other hand, changes in the skin friction coefficient are negligible.     

Nonlinear surface waves at ferrite-metamaterial waveguide structure

A new ferrite slab made of a metamaterial (MTM), surrounded by a nonlinear cover cladding and a ferrite substrate, was shown to support unusual types of electromagnetic surface waves. We impose the boundary conditions to derive the dispersion relation and others necessary to formulate the proposed structure. We analyse the dispersion properties of the nonlinear surface waves and we calculate the associated propagation index and the film–cover interface nonlinearity. In the calculation, several sets of the permeability of the MTM are considered. Results show that the waves behaviour depends on the values of the permeability of the MTM, the thickness of the waveguide and the film–cover interface nonlinearity. It is also shown that the use of the singular solutions to the electric field equation allows to identify several new properties of surface waves which do not exist in conventional waveguide.