Differential near-field scanning optical microscopy

We theoretically and experimentally illustrate a new apertured near-field scanning optical microscopy (NSOM) technique, termed differential NSOM (DNSOM). It involves scanning a relatively large (e.g., 0.3-2 mum wide) rectangular aperture (or a detector) in the near-field of an object and recording detected power as a function of the scanning position. The image reconstruction is achieved by taking a two-dimensional derivative of the recorded power map. Unlike conventional apertured NSOM, the size of the rectangular aperture/detector does not determine the resolution in DNSOM; instead, the resolution is practically determined by the sharpness of the corners of the rectangular aperture/detector. Principles of DNSOM can also be extended to other aperture/detector geometries such as triangles and parallelograms.     

A P-invariant-based algorithm for simple assembly line balancing problem of type-1

A simple assembly line balancing problem of type-1 (SALBP-1) concerns minimizing the number of workstations on an assembly line for a given cycle time. In this problem only a single product with deterministic task times is considered. Since the SALBP-1 is known as an NP-hard, considerable research effort has been spent to develop heuristic approaches. In this study we develop a different heuristic approach based on the P-invariants of Petri nets. The algorithm is coded in MATLAB, and its efficiency is tested on Talbot’s and Hoffmann’s benchmark datasets according to some performance measures and classifications. A computational study validates its effectiveness on Tonge’s 70-task problem by comparison with solutions of traditional heuristics and a genetic algorithm reported to perform well.     

Propham mineralization in aqueous medium by anodic oxidation using boron-doped diamond anode: influence of experimental parameters on degradation kinetics and mineralization efficiency

This study aims the removal of a carbamate herbicide, propham, from aqueous solution by direct electrochemical advanced oxidation process using a boron-doped diamond (BDD) anode. This electrode produces large quantities of hydroxyl radicals from oxidation of water, which leads to the oxidative degradation of propham up to its total mineralization. Effect of operational parameters such as current, temperature, pH and supporting electrolyte on the degradation and mineralization rate was studied. The applied current and temperature exert a prominent effect on the total organic carbon (TOC) removal rate of the solutions. The mineralization of propham can be performed at any pH value between 3 and 11 without any loss in oxidation efficiency. The propham decay and its overall mineralization reaction follows a pseudo-first-order kinetics. The apparent rate constant value of propham oxidation was determined as 4.8×10⁻⁴ s⁻¹ at 100 mA and 35 °C in the presence of 50 mM Na₂SO₄ in acidic media (pH: 3). A general mineralization sequence was proposed considering the identified oxidation intermediates.     

Lensfree color imaging on a nanostructured chip using compressive decoding

We demonstrate subpixel level color imaging capability on a lensfree incoherent on-chip microscopy platform. By using a nanostructured substrate, the incoherent emission from the object plane is modulated to create a unique far-field diffraction pattern corresponding to each point at the object plane. These lensfree diffraction patterns are then sampled in the far-field using a color sensor-array, where the pixels have three different types of color filters at red, green, and blue (RGB) wavelengths. The recorded RGB diffraction patterns (for each point on the structured substrate) form a basis that can be used to rapidly reconstruct any arbitrary multicolor incoherent object distribution at subpixel resolution, using a compressive sampling algorithm. This lensfree computational imaging platform could be quite useful to create a compact fluorescent on-chip microscope that has color imaging capability.     

Kinetics and equilibrium studies for the adsorption of Acid Red 57 from aqueous solutions onto calcined-alunite

The adsorption of Acid Red 57 (AR57) onto calcined-alunite was examined in aqueous solution in a batch system with respect to contact time, pH and temperature. The first-order, pseudo-second-order kinetic and the intraparticle diffusion models were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted very well the pseudo-second-order kinetic model and also followed the intraparticle diffusion model up to 90 min. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were also determined. The equilibrium data are successfully fitted to the Langmuir adsorption isotherm. The Langmuir isotherm constant, K(L), was used to evaluate the changes of free energy, enthalpy and entropy of adsorption for the adsorption of AR57 onto calcined-alunite. The results indicate that calcined-alunite could be employed as low-cost material for the removal of acid dyes from textile effluents.     

Minimum-phase-function-based processing in frequency-domain optical coherence tomography systems

We present a simple processing technique that uses the concept of minimum-phase functions to improve frequency-domain optical coherence tomography systems. Our approach removes the autocorrelation noise and therefore increases both the accessible depth range and the recovery accuracy. To our knowledge, this is the first time that the concept of minimum-phase functions has been applied to improve optical coherence tomography.     

Non-linear model predictive control to improve transient production of a hot dip galvanising line

A numerical transient model was designed to describe the dynamics of the annealing process prior to coating in a hot dip galvanising (HDG) line. The model was integrated into a model predictive controller developed in a previous work, including an adaptation mechanism to retain the model accuracy in operation. Complex transient production was studied to formulate proper constraints as input for the optimisation problem to be solved in real time. Simulations and online tests were carried out to verify the transient model and the controller design principles. The new controller has been implemented on a HDG line which annually produces 400 000 t of coated strip products mainly for the automotive and construction markets. Production using this controller proves its ability to correctly predict the future operation and optimise the control automation of the heating, the cooling and the line speed. Detailed data analysis shows significant improvements in terms of strip transition control precision, temperature control accuracy (50% increase inside tolerances), throughput maximisation (3–8% increase) and production consistency through the full automation.     

Surface Treatment of S355JR Carbon Steel Surfaces with ZrB<Subscript>2</Subscript> Nanocrystals by CO<Subscript>2</Subscript> Laser

To improve mechanical properties of S2355JR carbon steel, pre-synthesized ZrB₂ nanocrystals were used to coat the metal surface by laser cladding using 2000 W CO₂ laser. ZrB₂ nanocrystals were synthesized by mechanochemical process. The effect of laser power on the coating layers was examined for optimizing the most effective coating conditions. Microstructural studies were carried out using optical microscope, scanning electron microscope and X-ray diffraction to analyze phase structures of the coated layers. Mechanical characteristics of the laser coated layers were evaluated by studying microhardness, wear and scratch resistance properties. Maximum hardness of the coated layers was observed while cladding with 75 and 125 W laser powers, when other processing parameters and conditions were kept at optimum levels. EDS analysis of these laser cladded layers indicated the formation of complex boro-nitrides, nitrides and carbides of Zr and Fe that contributed to vast increase in hardness of the laser-clad coating on S2355JR steel. Depending upon the laser powers used, the thickness of the coated layers was found to be in the range of 15–37 µm. The wear and micro-scratch tests results revealed significant improvement in wear properties.     

Firing sequences backward algorithm for simple assembly line balancing problem of type 1

The objective of simple assembly line balancing problem type-1 (SALBP-1) is to minimize the number of workstations on an assembly line for a given cycle time. Since SALBP-1 is NP-hard, many iterative backtracking heuristics based on branch and bound procedure, tabu search, and genetic algorithms were developed to solve SALBP-1. In this study, a new heuristic algorithm based on Petri net approach is presented to solve the problem. The presented algorithm makes an order of firing sequence of transitions from Petri net model of precedence diagram. Task is assigned to a workstation using this order and backward procedure. The algorithm is coded in MATLAB, and its efficiency is tested on Talbot’s and Hoffmann’s benchmark datasets according to some performance measures and classifications. Computational study validates its effectiveness on the benchmark problems. Also comparison results show that the algorithm is efficiency to solve SALBP-1.