Characterization and lime treatment of olive mill wastewater

Seventeen olive mill wastewater (OMW) samples were characterized. For characterization of the samples, amount of total, fixed, volatile, suspended, volatile-suspended solids, COD, oil-grease, polyphenol, volatile phenol, nitrogen and reducing sugar were determined. Effects of lime treatment on the waste samples were investigated. Reduction of contents of the samples treated with the lime was described. The effect of the addition of lime on an artificial phenolic mixture was also examined.     

Frequency-dependent conductivity in unannealed thin films of As0.40Se0.40Te0.20

Direct current (d.c.) and alternating current (a.c.) conductivity measurements have been performed on unannealed amorphous As_0.40Se_0.40Te_0.20 thin films. The d.c. measurements were performed at temperatures between 143 K and 343 K. The d.c. behaviour of the samples indicates different hopping conduction mechanisms between 143 K-210 K and 210 K-343 K. The a.c. measurements were performed at temperatures between 143 K and 300 K and at frequencies between 110 Hz and 1 MHz. The a.c. conductivity of the films is well represented by the form Cω^s where C and s are found to be temperature dependent parameters. The data are found to fit the correlated barrier hopping model, especially at low temperatures. The comparison of a.c. data with the unified theory of the extended pair approximation shows that the results fit to the quasi universal law predicted by this model, however, qualitative calculations give unreasonable values for the decay parameter α and the exponent l.     

Effect of austenitization heat treatment on the magnetic properties of Fe-40wt % Ni-2wt % Mn alloy

The effect of austenitization heat treatment on magnetic properties was examined by means of M6ssbauer spectroscopy on an Fe-40wt%Ni-2wt%Mn alloy. The morphology of the alloy was obtained by using scanning electron microscopy （SEM） under different heat treatment conditions. The magnetic behavior of the non heat-treated alloy is ferromagnetic. A mixed magnetic structure including both paramagnetic and ferromagnetic states was obtained at 800℃ after 6 and 12 h heat treatments. In addition, the magnetic structure of the heat-treated alloy at 1150~C for 12 h was ferromagnetic. With the volume fraction changing, the effective hyperfine field of the ferromagnetic austenite phase and isomery shift values were also determined by Mtssbauer spectroscopy.     

Reduced myofibroblast differentiation on femtosecond laser treated 316LS stainless steel

In-stent restenosis is a common complication after stent surgery which leads to a dangerous wall narrowing of a blood vessel. Laser assisted patterning is one of the effective methods to modify the stent surface to control cell–surface interactions which play a major role in the restenosis. In this current study, 316LS stainless steel substrates are structured by focusing a femtosecond laser beam down to a spot size of 50 μm. By altering the laser induced spot density three distinct surfaces (low density (LD), medium density (MD) and high density (HD)) were prepared. While such surfaces are composed of primary microstructures, due to fast melting and re-solidification by ultra-short laser pulses, nanofeatures are also observed as secondary structures. Following a detailed surface characterization (chemical and physical properties of the surface), we used a well-established co-culture assay of human microvascular endothelial cells and human fibroblasts to check the cell compatibility of the prepared surfaces. The surfaces were analyzed in terms of cell adherence, proliferation, cell morphology and the differentiation of the fibroblast into the myofibroblast, which is a process indicating a general fibrotic shift within a certain tissue. It is observed that myofibroblast proliferation decreases significantly on laser treated samples in comparison to non-treated ones. On the other hand endothelial cell proliferation is not affected by the surface topography which is composed of micro- and nanostructures. Such surfaces may be used to modify stent surfaces for prevention or at least reduction of restenosis.     

Failure Analysis of Two-Dimensional Carbon-Epoxy Composite Plate Pinned Joint

The aim of this study is to investigate failure strength and failure mode of a mechanically fastened carbon-epoxy composite plate of arbitrary orientation. The failure load and the failure mode are analyzed numerically and experimentally. The numerical method includes two steps. First, the stress distribution in the plate is calculated by the use of finite-element method. Second, the failure load and the failure mode are predicted by means of Tsai-Hill and fiber tensile-compressive failure criteria. A computer program was developed which can be used to calculate the failure load, the failure mode, and the propagation of failure. The distance-to-diameter, E/D , and width-to-diameter, W/D , ratios in the plate are changed from 1 to 5 and 2 to 5, respectively. It is found that full bearing strength is developed when E/D and W/D ratios are equal to or greater than 4.     

Noncoherent space-time coding: An algebraic perspective

The design of space-time signals for noncoherent block-fading channels where the channel state information is not known a priori at the transmitter and the receiver is considered. In particular, a new algebraic formulation for the diversity advantage design criterion is developed. The new criterion encompasses, as a special case, the well-known diversity advantage for unitary space-time signals and, more importantly, applies to arbitrary signaling schemes and arbitrary channel distributions. This criterion is used to establish the optimal diversity-versus-rate tradeoff for training based schemes in block-fading channels. Our results are then specialized to the class of affine space-time signals which allows for a low complexity decoder. Within this class, space-time constellations based on the threaded algebraic space-time (TAST) architecture are considered. These constellations achieve the optimal diversity-versus-rate tradeoff over noncoherent block-fading channels and outperform previously proposed codes in the considered scenarios as demonstrated by the numerical results. Using the analytical and numerical results developed in this paper, nonunitary space-time codes are argued to offer certain advantages in block-fading channels where the appropriate use of coherent space-time codes is shown to offer a very efficient solution to the noncoherent space-time communication paradigm.     

Characteristics of CFRP retrofitted hollow brick infill walls of reinforced concrete frames

The mechanical characteristics of infill walls retrofitted with carbon fiber reinforced polymer (CFRP) sheets are really important for the realistic prediction of seismic performance of the vulnerable reinforced concrete (RC) frames retrofitted through CFRP strengthened infill walls. In this study, 36 hollow brick wall specimens were tested either under uniaxial compression or diagonal tension before and after retrofitting externally with CFRP sheets. The test parameters are the dimensions of the walls, the orientation of holes of bricks, the type of mortar, the amount of CFRP sheets and the details of strengthening application. At the end of the tests, a significant contribution of CFRP sheets on the mechanical characteristics of hollow brick walls was observed in terms of several important structural design parameters such as Young and shears moduli, axial and shears strengths as well as the deformation capacity. Finally, the strength and deformability characteristics of the walls and frames retrofitted with CFRP sheets were predicted analytically. The predictions were in good agreement with the experimental data.     

Second law analysis of two‐stage compression transcritical CO2 heat pump cycle

Because of the global warming impact of hydro fluorocarbons, the uses of natural refrigerants in automotive and HVAC industries have received worldwide attention. CO₂ is the most promising refrigerant in these industries, especially the transcritical CO₂ refrigeration cycle. The objective of this work is to identify the main factors that affect two‐stage compression transcritical CO₂ system efficiency. A second law of thermodynamic analysis on the entire two‐stage CO₂ cycle is conducted so that the exergy destruction of each system component can be deduced and ranked, allowing future efforts to focus on improving the components that have the highest potential for advancement. The inter‐stage pressure is used as a variable parameter in the analysis study. The second law efficiency, coefficient of cooling performance and total exergy destruction of the system variations with the inter‐stage pressure are presented graphically. It was concluded that there is an optimum inter‐stage pressure that maximizes both first law and second law efficiencies. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation and thermal properties of polyethylene terephthalate/huntite–hydromagnesite composites

In this report, it was aimed to the improve thermal stability of polyethylene terephthalate (PET) by adding huntite/hydromagnesite minerale. PET/huntite/hydromagnesite composites were prepared by adding various proportions of huntite/hydromagnesite to PET. The chemical structures of the composites were characterized by Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD) analysis. Thermal properties of the composites were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Glass‐transition temperatures and char yields increased with the increase of the huntite/hydromagnesite content in the composites. The surface morphologies of the composites were investigated by a scanning electron microscopy. The obtained results proved that the composite system is more thermally stable than the pure PET itself. POLYM. COMPOS., 37:3275–3279, 2016. © 2015 Society of Plastics Engineers     

A novel nonchemical approach to the expansion of halloysite nanotubes and their uses in chitosan composite hydrogels for broad‐spectrum dye adsorption capacity

A novel method based on cryoscopic expansion of halloysite nanotubes via frozen water molecules entrapped in their lumens and subsequent lyophilization was described. Detailed analyses confirmed that the inner and outer diameters as well as the surface area of the nanotubes could be efficiently increased without disturbing the inherent tubular structure. The benefits of cryo‐expanded nanotubes for the enhancement of chitosan hydrogel performances were discussed. The composite hydrogels, depending on their compositions and morphologies, exhibited significantly enhanced swelling and mechanical properties compared with neat chitosan hydrogel. This effect was even more pronounced in the hydrogels containing cryo‐expanded halloysite nanotubes. Although neat chitosan is a selectively good adsorbent for anionic dyes, in the presence of a small amount of cryo‐expanded halloysite, the resultant composite hydrogel can establish a relatively high adsorption capacity for anionic and cationic dyes as a broad‐spectrum dye adsorbent. POLYM. COMPOS., 37:2770–2781, 2016. © 2015 Society of Plastics Engineers