Trade‐offs in integer data envelopment analysis

If production trade‐offs—which represent simultaneously feasible exchanges in the inputs and outputs of decision‐making units (DMUs)—are added to an integer production possibility set (IPPS), a new IPPS is produced; conventional axioms of production do not generate a new IPPS, however. This paper develops the axiomatic foundation for data envelopment analysis (DEA) for integer‐value inputs and outputs in the presence of production trade‐offs by introducing a new axiom of “natural trade‐offs.” First, a mixed‐integer linear programming formula called an integer DEA trade‐off (IDEA‐TO) is presented for computing efficiency scores and reference points. The numeration algorithm (NA) method presented in this concept is improved, and an improved numeration algorithm (INA) method for solving integer DEA (IDEA) models is developed. Finally, comparison between the two methods and a generalized INA method for solving the IDEA‐TO model are presented.     

Preparation of synthesized sulfide polymer through phase-transfer catalyzed polycondensation of ethylene dibromide and sodium tetrasulfide: characterization,thermal and rheological properties

Sulfide polymers were obtained through the interfacial polymerization of sodium tetrasulfide and ethylene dibromide. The polymerization process was carried out under interfacial condition using two phase-transfer catalysts: methyl-tributyl ammonium bromide and methyl-tributyl ammonium chloride. The polymer characteristics were examined by attenuated total reflectance- fourier transform infrared spectroscopy, elemental analysis (CHNS/O) and X-ray diffraction methods. Thermal characteristics were investigated by differential scanning calorimetry and thermogravimetric analysis methods. The rheological behavior of the synthesized sulfide polymer during curing reaction, and isothermal time dependency of elastic storage modulus, G^′, at different temperatures and constant shear frequency was studied using a stress-controlled rheometer. Moreover, the solvent resistance of synthesized polymer was investigated through the swelling method.     

Evaluation of the mechanical properties,in vitro biodegradability and cytocompatibility of natural chitosan/hydroxyapatite/nano-Fe3O4 composite

The main goal of this research was the preparation and evaluation of the mechanical properties, in vitro biodegradability and cytocompatibility, of natural chitosan/hydroxyapatite/nano magnetite (nano-Fe₃O₄) composite. Different ratios of these components were investigated, including chitosan/hydroxyapatite: 4/4 (S1), chitosan/hydroxyapatite: 4/6 (S2), and chitosan/hydroxyapatite: 6/4 (S3). Mechanical properties of fabricated composites were examined using bending and compression tests before immersion, and after 2 and 9 weeks of immersion in the Ringer's solution. Scanning electron microscope (SEM) was employed for observing the bending fracture surface and analyzing the degradation morphology. Human mesenchymal stem cells (hMSC) were also cultured on the samples in order to assess the cytocompatibility. The obtained results revealed that S1 had the highest bending strength before immersion, while S3 had the highest bending strength after 9 weeks immersion. Compressive strength of S2 was greater than that of S1 and S3 not only before immersion, but also after 9 weeks immersion. Although the bio-minerals were deposited on the surface of all samples during the immersion in Ringer's solution, S2 appeared to have the highest quantity of bio-minerals. According to the weight loss percentage (ΔW(%)), the biodegradation resistance of S1 was the lowest. Finally, the cytocompatibility of S1 was greater than that of S2 and S3.     

The evolution of soot morphology in a laminar coflow diffusion flame of a surrogate for Jet A-1

An experimental study is performed to investigate the evolution of soot morphology in an atmospheric pressure laminar coflow diffusion flame of a three-component surrogate for Jet A-1. The laser extinction measurement method and the rapid thermocouple insertion technique are used to obtain soot volume fraction profiles and temperature profiles, respectively. Thermophoretic sampling followed by transmission electron microscopy and atomic force microscopy is used to study the morphology of soot particles at different locations inside the flame. Soot formation on the centerline appears to be different from conventional models. Liquid-like particles, which are transparent at the wavelength of 623 nm, are formed and grow up to a volume equivalent diameter of d_p = 60 nm at temperatures below T = 1500 K. When the temperature exceeds 1500 K, transition of the transparent particles to the mature agglomerated particles happens immediately, i.e. in less than 12 ms. The volume of the liquid-like particles just before the start of their transformation to solid is about five times larger than the volume of mature primary particles. This significant size difference suggests that a large liquid-like particle does not transform into a single primary particle. In addition, multiple dark nuclei are observed in the liquid-like particles prior to carbonization. The significant size discrepancy and the presence of multiple dark nuclei may indicate that primary particle formation and agglomeration on the centerline happen inside the liquid-like particles. In contrast to the centerline, on another streamline with a significantly different temperature history, soot particles form from relatively small liquid-like particles. These particles have the same size as mature primary particles. Carbonization happens early on the streamline. A single dark nucleus grows inside each liquid-like particle and primary particles agglomerate after carbonization is completed. Most of the currently used computational soot models consider a single evolution process for all of the streamlines inside the flame which may not be an accurate assumption. This study shows that soot evolution processes may be different across the flame and are a function of temperature and the concentration of specific species inside the flame.     

Recent advances in core/shell bicomponent fibers and nanofibers: A review

There has been a steady progress in developing synthetic fibers in the past few years. Bicomponent fibers and nanofibers in a core/shell (C/S) configuration, including two dissimilar materials have presented unusual potential for use in many novel applications. These fibers can be produced using a variety of materials via different techniques i.e., coaxial melt spinning and electrospinning. In this review, we discuss the recent advances in C/S fibers and nanofibers’ production. The first part has been assigned to the bicomponent fibers manufacturing technology, while production and applications of C/S nanofibers have been described in the second part. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46265.     

pH-responsive polymer in a core–shell magnetic structure as an efficient carrier for delivery of doxorubicin to tumor cells

A pH-responsive polymer derived from polyethyleneimine with zwitterionic function was used as a shell around super paramagnetic iron oxide nanoparticles (SPIONs), to introduce an efficient drug carrier for cancer drug delivery and imaging. Core–shell magnetic Fe₃O₄@FA-PEI-SUC (SUC: Succinate conjugated) nanoparticles were attained and characterized. Right chemical attachments, 61.34% modification of primary amino groups of poly(ethyleneimine) (PEI) in PEI–SUC, spherical shape, core–shell structure, crystal structure of SPIONs, 18.23% polymer coating of NPs, 8% decrease in magnetization following polymer coating around SPIONs, doxorubicin loading efficiency 85.19%, two times more released amount in acidic pH, and proper toxicity results were obtained by different analysis methods.     

A Rapid Photopatterning Method for Selective Plating of 2D and 3D Microcircuitry on Polyetherimide

In this work, a method for the rapid synthesis of metallic microtracks on polyetherimide is presented. The method relies on the photosynthesis of silver nanoparticles on the surface of the polymer substrates from photosensitive silver chloride (AgCl), which is synthesized directly on the polyetherimide surface. The study reveals that the use of AgCl as a photosensitive intermediate accelerates the reactions leading to the formation of silver nanoparticles by up to two orders of magnitude faster than other photodecomposition schemes. The patterning can be conducted under blue light, with notable advantages over UV exposure. Polymers of significant interest to the microelectronics and 3D printing industries can be directly patterned by light using this photography‐inspired technique at throughputs high enough to be commercially advantageous. Light exposures as short as a few seconds are sufficient to allow the direct metallization of the illuminated polyetherimide surface. The results show that the silver required for the seed layer is minimal, and the later copper electroless plating results in the selective growth of conductive tracks for circuitry on the light‐patterned areas, both on flexible films and 3D printed surfaces.     

Simulation of an orifice scrubber performance based on Eulerian/Lagrangian method

A mathematical model based on Eulerian/Lagrangian method has been developed to predict particle collection efficiency from a gas stream in an orifice scrubber. This model takes into account Eulerian approach for particle dispersion, Lagrangian approach for droplet movement and particle-source-in-cell (PSI-CELL) model for calculating droplet concentration distribution. In order to compute fluid velocity profiles, the normal k− turbulent flow model with inclusion of body force due to drag force between fluid and droplets has been used. Experimental data of Taheri et al. [J. Air Pollut. Control Assoc. 23 (11) (1973) 963] have been used to test the results of the mathematical model. The results from the model are in good agreement with the experimental data. After validating the model the effect of operating parameters such as liquid to gas flow rate ratio, gas velocity at orifice opening, and particle diameter were obtained on the collection efficiency.