Investigation of stress fields occurred in the block caving process at a diasporite deposit in Western Turkey

The modeling with the finite element method was employed to study the block caving process for mining the Milas diasporite deposit in Western Turkey. The stress distribution in the vicinity of production and haulage levels is evaluated applying an elasto-plastic rock mass model. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 6, pp. 63–71, November–December, 2005.     

Immobilization of pepsin on chitosan beads

In this study, chitosan beads were prepared by using a cross-linking agent and the resulting beads were employed in immobilization process. Studies on free and immobilized pepsin systems for determination of optimum temperature, optimum pH, thermal stability, pH stability, operational stability, storage stability and kinetic parameters were carried out. The optimum temperature interval for free pepsin and immobilized pepsin were 30–40 and 40–50 °C, respectively. Free and immobilized pepsin showed higher activity at pH 2.0–4.0. Apparent K_m = 12.0 g L⁻¹ haemoglobin (1.56 mM tyrosine) and V_max = 5220 μmol (mg protein min)⁻¹ values were obtained for free pepsin, while apparent K_m = 20.0 g L⁻¹ haemoglobin (2.16 mM tyrosine) and V_max = 2780 μmol (mg protein min)⁻¹ values were obtained for immobilized pepsin. Thermal stability and storage stability of immobilized pepsin were higher than that of free pepsin. Milk clotting activity was used for evaluation of the applicability of pepsin immobilization to industrial process. Optimum milk clotting temperature was found as 40 °C for free pepsin and 50 °C for immobilized pepsin.     

Universal serially concatenated trellis coded modulation for space-time channels

This paper presents serially concatenated trellis coded modulations (SCTCMs) that perform consistently close to the available mutual information for periodic erasure channel (PEC), periodic fading channel (PFC) and the 2 times 2 compound matrix channel. We use both the maximum-likelihood decoding criteria and iterative decoding criteria to design universal SCTCMs for the PEC and the PFC. For the space-time channel, by demultiplexing the symbols across the antennas, the proposed universal SCTCMs for the period-2 PFC deliver consistent performance over the eigenvalue skew of the matrix channel. Within the family of channels having the same eigenvalue skew, a time-varying linear transformation (TVLT) is used to mitigate the performance variation over different eigenvectors. The proposed space-time SCTCMs of 1.0, 2.0 and 3.0 bits per transmission require excess mutual information in the ranges 0.11-0.15, 0.23- 0.26 and 0.35-0.53 bits per antenna, respectively. Because of their consistent performance over all channels, the proposed codes will have good frame-error-rate (FER) performance over any quasi-static fading distribution. In particular, the codes provide competitive FER performance in quasi-static Rayleigh fading.     

A new algorithm for optimization of quality of service in peer to peer wireless mesh networks

Wireless Networks - Nowadays, wireless mesh networks are known as important parts of different commercial, scientific, and industrial processes. Their prevalence increases day-by-day and the future...     

Aluminium based resistance alloys for low temperatures

The resistivity of several (AlMgMn)-alloys with a magnesium mass content of 5%, and manganese contents of 0% up to 1%, has been measured in the temperature range of 1.5 to 4.2 K. It is shown that a Mn concentration of 0.078% produces a broad resistivity minimum at about 4.2 K; this means that the resistivity only varies by about 1.3 ppm between 1.5 and 4.2 K. It is further shown that the technical aluminium alloy AlMg 5 also has a similar small temperature coefficient of resistivity (TCR), in particular, the TCR is a few parts in 10⁷/K for temperatures between 2 and 4.2 K. The fact that this alloy is commercially available and inexpensive, makes it very attractive as a low temperature resistance material for various applications.     

Theory of powdered crystal formation in electrocrystallization—occurrence of morphological instability at the electrode surface

The kinetics of cathodic electrodeposition of solid metals from an electrolytic solution were quantitatively analysed with the aid of the linear instability treatment to understand the eccentric growth of powdery crystals in a diffusion limiting current region. The powder growth could be interpreted by the instability involved in the diffusion process of depositing ions. In order to determine the conditions of instability which accelerate powder formation, some equations described the kinetic behaviors of various small perturbations imposed on an electrochemical system. It has been concluded that cathodic electrocrystallization should always be unstable; thus irregular growth of the electrode surface is expected to occur. Furthermore, the dominant growth rate and size of the irregular crystal particle are calculated under various electrolysis conditions, eg various applied overpotential and bulk concentration of the metal ion. Most of the experimental results previously reported agree with the prediction obtained here.     

Alkyd resins based on waste PET for water-reducible coating applications

Simultaneous glycolysis and neutral hydrolysis of waste PET flakes obtained from grinding post-consumer bottles was carried out in the presence of xylene and an emulsifier at 170 °C. The product was separated from ethylene glycol (EG), water, and xylene by filtration, and was extracted by water at boiling point thrice. The remaining solid was named water insoluble fraction (WIF). The filtrate was cooled to 4 °C, and the crystallized solid obtained by filtration was named water soluble crystallizable fraction (WSCF). These fractions were characterized by acid value (AV) and hydroxyl value (HV) determinations. WSCF and WIF were used for preparation of the water-reducible alkyd resins. Three long oil alkyd resins were prepared from phthalic anhydride (PA; reference alkyd resin) or depolymerization product of the waste PET (PET-based alkyd resin), glycerin (G), fatty acids (FA), and glycol (EG; reference alkyd resin) or depolymerization product of the waste PET (PET-based alkyd resin). Film properties and thermal degradation stabilities of these alkyd resins were investigated. Physical properties (drying times and hardness) and thermal degradation stabilities of the PET-based alkyd resin is better than these properties of the reference alkyd resin.     

Comparison of the mechanical,thermomechanical, thermal,and morphological properties of pumice and calcium carbonate‐filled poly(phenylene sulfide) composites

In this study, it was aimed to investigate the mechanical, thermal, thermomechanical, and morphological properties of pumice and calcium carbonate (CaCO₃)‐filled poly(phenylene sulfide) (PPS) composites and compare the effect of these filler materials on the properties of composites. Mechanical test results indicate that %1 pumice and CaCO₃ addition increased the tensile strength value of PPS. With the %1 loading level of pumice, tensile strain of composites remained unchanged, but for other loading levels of both fillers, tensile strain of composites decreased. Hardness of composites increased with the addition of pumice to PPS matrix for all loading levels of pumice. The lowest damping factor peak intensity was observed for %1 pumice included composites. Morphological analyses results revealed that pumice particles are clearly embedded in the PPS matrix and covered with matrix. On the other hand, there are a number of microvioids that can be observed in the tensile fracture surfaces of CaCO₃‐filled composites. POLYM. COMPOS., 37:3160–3166, 2016. © 2015 Society of Plastics Engineers