Effect of chemical substitution on the morphology and optical properties of Bi1−xCaxFeO3 films grown by pulsed-laser deposition

The morphological characteristics as well the optical properties of Ca-doped BiFeO₃ films grown by pulsed-laser deposition technique have been investigated. AFM images revealed that calcium has a radical effect on the surface features of BiFeO₃ films. By utilizing spectrophotometer, transmission behaviour of the films was investigated. Local IV characteristics of the films disclosed about three orders of magnitude enhancement concerning electrical conductivity through Ca doping. X-ray photoelectron spectroscopy results revealed that Ca can reduce the valence state of iron in the compound.     

The effect of process parameters on the size and morphology of poly(D,L‐lactide‐co‐glycolide) micro/nanoparticles prepared by an oil in oil emulsion/solvent evaporation technique

For the past few decades, there has been a considerable research interest in the area of biodegradable polymeric micro‐ and nanoparticles for tissue engineering, regenerative medicine, implants, stents, medical devices, and drug delivery systems. Poly(D,L ‐lactide‐co‐glycolide) (PLGA) is well‐known by its safety in biomedical preparations which has been approved for human use by the FDA. The goal of this study was to evaluate the influence of process parameters on size characteristics of PLGA microparticles prepared by oil in oil (o/o) solvent evaporation technique. This method has been introduced as one of the most appropriate methods for hydrophilic agents. Scanning electron microscopy showed that prepared particles were spherical with smooth surface without aggregation. Particle size varied from 570 nm to 29 μm in different experimental conditions. Stirring speed, polymer concentration, impeller type, and dropping size had a significant effect on the particle size. The polydispersity index of particles showed a strong relationship with the surfactant concentration, impeller type, and dropping size. It was concluded that increasing in temperature up to 50°C or changing in dropping rate has a little effect on reducing the size of PLGA particles. The residual solvent content in the final suspension was less than 0.1 ppm that is in appropriate range for biomedical application. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Commercial,high-impact polypropylenes: Composition and chain structure as revealed by temperature-gradient extraction fractionation

Four different grades of commercial, high-impact polypropylene (hiPP) were fractionated by temperature-gradient extraction fractionation, and the chain structure and melting behavior of the fractions were studied by Fourier transform infrared spectroscopy and differential scanning calorimetry. Furthermore, the morphology of the disperse phase in the resins was characterized by scanning electron microscopy of the microtome-cut etched and original samples. The results show that there was a strong relation between the chain structure, content, and distribution of the dispersed phase and the mechanical properties of hiPP. These parameters of the elastomeric phase are really critical in reaching the best rigidity-impact balance in hiPP. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Applying simulated annealing for designing cellular manufacturing systems using MDmTSP

The design of cellular manufacturing systems involves many structural and operational issues. One of the important design steps is the formation of part families and machine cells (cell formation). Despite a large number of papers on cell formation published worldwide, only a handful incorporates operation sequence in layout design (intra-cell move calculations). We propose a solution to solve the part-family and machine-cell formation problem considering the within-cell layout problem, simultaneously. In this paper, the cellular manufacturing system is formulated as a multiple departures single destination multiple travelling salesman problem (MDmTSP) and a solution methodology based on simulated annealing is proposed to solve the formulated model. Numerical examples show that the proposed method is efficient and effective in finding optimal solutions. The results also indicate that the proposed approach performs well compared to some well-known cell formation methods.     

An integrated model for solving cell formation and cell layout problem simultaneously considering new situations

Cellular manufacturing system (CMS) is one of the group technology (GT) usages. Among the necessary decisions for a successful CMS implementation, cell formation problem (CFP) and cell layout problem (CLP) are two most popular ones. The majority of past studies in CMS discussed on CFPs and some of those focused on CLP ones. A few researchers solve the CPF and CLP simultaneously. In this paper, we present a new integrated mathematical model considering cell formation and cell layout simultaneously. The goal of our model is to group similar parts and corresponding different machines in same cells. Machines sequence in each cell and cell positions is also specified in the system. Moreover, our proposed model considers forward and backtracking movements as well as new assumptions for distances between cells using sequence data and production volume. One appropriate adjusted measure from the literature and two new measures of performance for evaluating solutions are defined. To validate the model, two well-known critical benchmark examples are employed. Computational experiments demonstrate that our proposal is a proficient model and show the effectiveness of our implementation.     

An empirical study of the relationship between the concepts expressed in source code and dependence

Programs express domain-level concepts in their source code. It might be expected that such concepts would have a degree of semantic cohesion. This cohesion ought to manifest itself in the dependence between statements all of which contribute to the computation of the same concept. This paper addresses a set of research questions that capture this informal observation. It presents the results of experiments on 10 programs that explore the relationship between domain-level concepts and dependence in source code. The results show that code associated with concepts has a greater degree of coherence, with tighter dependence. This finding has positive implications for the analysis of concepts as it provides an approach to decompose a program into smaller executable units, each of which captures the behaviour of the program with respect to a domain-level concept.     

A branch-and-bound algorithm for single-machine scheduling with batch delivery and job release times

This paper addresses scheduling a set of jobs with specified release times on a single machine for delivery in batches to customers or to other machines for further processing. This problem is a natural extension of minimizing the sum of flow times in the presence of release time by considering the possibility of delivering jobs in batches and introducing batch delivery costs. The scheduling objective adopted is that of minimizing the sum of flow times and delivery costs. The extended problem arises in the context of coordination between machine scheduling and a distribution system in a supply chain network. Structural properties of the problem are investigated and used to devise a branch-and-bound solution scheme. Computational experiments show significant improvement over an existing dynamic programming algorithm.     

A bi-objective possibilistic programming model for open shop scheduling problems with sequence-dependent setup times, fuzzy processing times, and fuzzy due dates

We are concerned with an open shop scheduling problem having sequence-dependent setup times. A novel bi-objective possibilistic mixed-integer linear programming model is presented. Sequence-dependent setup times, fuzzy processing times and fuzzy due dates with triangular possibility distributions are the main constraints of this model. An open shop scheduling problem with these considerations is close to the real production scheduling conditions. The objective functions are to minimize total weighted tardiness and total weighted completion times. To solve small-sized instances for Pareto-optimal solutions, an interactive fuzzy multi-objective decision making (FMODM) approach, called TH method proposed by Torabi and Hassini, is applied. Using this method, an equivalent auxiliary single-objective crisp model is obtained and solved optimally by the Lingo software. For medium to large size examples, a multi-objective particle swarm optimization (MOPSO) algorithm is proposed. This algorithm consists of a decoding procedure using a permutation list to reduce the search area in the solution space. Also, a local search algorithm is applied to generate good initial particle positions. Finally, to evaluate the effectiveness of the MOPSO algorithm, the results are compared with the ones obtained by the well-known SPEA-II, using design of experiments (DOE) based on some performance metrics.     

Quantitative filter forensics: Size distribution and particulate matter concentrations in residential buildings

We applied filter forensics, the analysis of dust from the heating, ventilation, and air-conditioning (HVAC) filters, to measure particle size distribution in 21 residences in Toronto, Canada over a year. Four filters with different nominal efficiencies (Minimum Efficiency Reporting Value (MERV) 8–14 from ASHRAE Standard 52.2) were deployed in each residence each for three months, while the effective filtration volumes (the product of flow rate, runtime, and in-situ filter efficiency) were characterized over each filter lifetime. Using extraction and laser diffraction, we found that approximately 90% of the volumetric distributions were >10 µm and the volume median diameter (VMD) ranged from 23.4 to 75.1 µm. Using quantitative filter forensics (QFF), total suspended particle (TSP) concentrations ranged from 2.9 to 823.7 µg/m³ (median = 89.8 µg/m³) with a moderate correlation with the content of TSP on the filters (in terms of g) and with the TSP effective filtration volume (m³) indicating the importance of both filter forensics and HVAC metadata parameters to QFF concentration estimates. There was no strong correlation between PM₁₀ or PM_2.5 concentrations and hourly airborne particle number concentrations measured by low-cost sensors suggesting an evaluation of QFF is warranted, particularly for the exploration of smaller particles.     

A photochemical method for controlling the size of CdS nanoparticles

The optical and electrical properties of semiconductor nanoparticles are strongly dependent on their size. A flexible control of the size of the nanoparticles is of interest for tuning their properties for different applications. Here we use a coupled method to control the size of CdS nanoparticles. The method involves the photochemical growth of CdS nanoparticles together with the use of a capping agent as an inhibiting factor. CdS nanoparticles were formed through a photoinduced reaction of CdSO(4) and Na(2)S(2)O(3) in an aqueous solution. Mercaptoethanol (C(2)H(6)OS) was used as the capping agent, and we investigated the effect of illumination time, illumination intensity and the concentration of capping agent on the nanoparticle size. Transmission electron microscopy (TEM) shows crystalline nanoparticles with relatively low dispersion. Optical absorption spectroscopy was mainly used to measure the band gap and size of the nanoparticles. Increasing the illumination time or illumination intensity increases the nanoparticle size, while higher capping agent concentration leads to smaller nanoparticle size. A band gap range of 2.75-3.4?eV was possible with our experimental conditions, corresponding to a 3.2-6.0?nm size range.