Preparation and Evaluation of Some Polymeric Basalt Composites

Unsaturated polyester based on poly(ethylene, 1,2, propylene ma-leate-phthalate-adipate) was synthesized and used with the styrene monomer as a binder to produce polymeric basalt composites (PBC). The physical properties of the styrenated polyester resin (SP) were determined. Because the aggregate type and composition do affect the durability properties of the composites, the minerological, textural, and chemical composition of the basalt Filler were studied. The mix design for the PBC systems was optimized for workability, strength, and economy. The optimum composition was 10wt% resin and 90wt% oven-dried basalt.

The mechanical and durability properties of the prepared PBC have been investigated. The physical, mechanical, and thermal properties of the composites appear to be satisfactorily good. Excellent chemical resistance to most chemical environments was also noted. The dielectric constant (?′) values indicated that the use of basalt as a filler enhances the electrical characteristics of the PBC as insulators as compared to the SP resin. Obviously, the obtained PBC would be excellent candidates for several potential applications.     

Elemental chlorine-free bleaching halfa pulp

Halfa, also known as Stipa tenacissima, is grown in North Africa and south Spain. Due to its short fiber length, paper of halfa remains bulk and takes the block letters well. In this study halfa was evaluated for bleached pulp production. Two cellulose pulps with different chemical compositions were pulped by conventional Kraft process: one from the original halfa material and the other from halfa pretreated by diluted acid. The pulp produced from halfa pretreated by diluted acid was bleached by elemental chlorine-free sequences, DEPD and DEDP. Yield, Kappa number, brightness and α-cellulose contents of bleached and unbleached pulps were evaluated. The results show that during the chemical pulping process, treated halfa was easily cooked than that original halfa. Treated halfa pulp also showed very good bleaching, showing brightness level of 94.8% ISO, yield 93.6% and α-cellulose content 96.8% with DEDP bleaching sequence compared to 83.2% ISO brightness level, 92.8% yield and 95.1% α-cellulose content for bleached pulp with DEPD bleaching sequence. On the other hand, the physicomechanical properties of pulp were not notably reduced by the bleaching process. Breaking length, tear and burst index of paper sheets were acceptable. Therefore, this halfa material could be a worthwhile choice for cellulosic fiber supply.     

Rapid prototyping of MIMO‐OFDM based on parity bit selected and permutation spreading

In this paper, a novel MIMO‐OFDM transmission scheme is developed to effectively enable multi‐access by joint code design across multiple antennas, subcarriers, OFDM frames, and users. It achieves better spectrum efficiency while improving bit error rate performance. The proposed scheme uses either parity bit selected or permutation techniques to assign spreading codes at the transmitter side. As a result, the detection at the receiver is greatly improved because of the fact that identifying the spreading code(s) directly yields the transmitted data symbols. The paper also investigates the field‐programmable gate array implementation of the proposed algorithms; optimization techniques are proposed to reduce area, power, and time. These techniques include a pipelined architecture for inverse FFT/FFT blocks, an efficient low complexity algorithm for despreading based on counters and comparators and an optimized architecture for complex matrix inversion using Gauss–Jordan elimination (GJ‐elimination). Finally, the fixed‐point optimized field‐programmable gate array architecture for MIMO‐OFDM transceiver is developed, where the maximum allowed performance loss because of quantization is defined, the tradeoffs between BER performance and area reduction are investigated. Copyright © 2015 John Wiley & Sons, Ltd.     

Development of heat-resistant anticorrosion urethane siloxane paints

Three two-layer heat-resistant and anticorrosion paints have been formulated from urethane siloxane binder and traditional anticorrosion pigments such as micaceous iron oxide (MIO), zinc phosphate (ZP), and aluminum oxide. These pigments were used as the dominant components of different undercoats or topcoats. Heat-resistant pigments such as silicon nitride and glass-spheres were used in the composition of the topcoats. Thermogravimetric analysis of paints shows that the paint with ZP as dominant component of the undercoat have the highest heat-resistance and stability in inert gas and oxygen. The paint with a combination of MIO and ZP has the best hardness as well as the best protective and anticorrosion properties based on the electrochemical impedance spectroscopy. A maximum synergic effect of the properties of pigments seems to appear in this paint. Surface morphology of paints was studied by means of scanning electron microscopy. Heated at different temperatures and for several hours, paint containing MIO as the dominant component in the undercoat exhibits the best mechanical and adhesion properties.     

Study of hydrogen production system by using PV solar energy and PEM electrolyser in Algeria

Hydrogen fuel can be produced by using solar electric energy from photovoltaic (PV) modules for the electrolysis of water without emitting carbon dioxide or requiring fossil fuels.     

Templating polyacrylamide hydrogel for interconnected microstructure and improved performance

In this study, the pressure and temperature are monitored during acrylamide polymerization and their effects on the mechanical properties and swelling of the resulting hydrogel are investigated. The polymerization kinetic and network formation mechanism are correlated to the environmental thermodynamic conditions under which the hydrogels are polymerized. Then, the swelling and Young's modulus are measured and shown to be tunable along a wide range of values. The swelling ratio varies between 50 and 2262 while Young's modulus varies between 10.99 and 40.70 kPa. In addition, the formation of macroporous hydrogel with channel like structures along the vacuum direction under a reduced pressure of 5 mbar is reported. The macroporous hydrogel has a modulus of 40.70 kPa and shrink approximatively three times faster than the hydrogel polymerized under normal pressure and has a modulus of 10.99 kPa. Hence, this interconnected network can overcome the fluid diffusion limitations of bulk hydrogels without compromising the mechanical properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46205.     

A New Linear Group-Wise SIC Multiuser Detector

In this work, we introduce a new linear group-wise SIC multi-user detector that can converge to either the decorrelator or the least minimum mean-square error (LMMSE) detector. We study the convergence behavior of the proposed scheme and show that the latter is equivalent to the block Gauss-Seidel iterative method if the group-detection scheme used is the decorrelator detector. Moreover, we prove that the latter is convergent if the group-detection matrix is positive definite. Our simulation results are in excellent agreement with the proposed theory     

Simulating the performance of supply chain with various alliances

Many models of supply chain management (SCM) have been popularly developed in recent years. However, this study focuses on the supply chain (SC) performance with respect to various alliances among partners. First, this study explores the game theory for formulating the SCM problem as a multi-objective programming problem. Second, various alliances, e.g., union, extreme competition, and Stackelberg competition among partners will be considered in such a problem so as to compare the SC performance under different alliances. Third, a numerical example is illustrated by two material supplier partners, three manufacturing partners, two logistics partners, and three customers, where each partner in the SC has its own objective and constraints. This SC problem is resolved across three different time periods. Finally, study results show that the maximum global benefits can be obtained only when all partners form a single union, but the inefficient partners lose significantly in such a union. The minimal global benefits exist in the extreme competition.     

Properties of metakaolin based geopolymer incorporating calcium carbonate

An alkaline solution, thermally activated kaolinite clay and a mineral additive (calcium carbonate) were mixed with the aim to elaborate a geopolymer material with physical and mechanical properties comparable to those of classical construction materials.The starting reagents were characterized by quantitative chemical analyses (XRF), mineralogical analyses (XRD), thermal gravimetric analyses (TGA), and grain size distribution measurements. The setting of the mixture (polymerization) was implemented by measuring the evolution of the viscosity as a function of time at different temperatures.The geopolymers were synthesized at a temperature of 40 °C. The investigation of the mechanical behavior reveals that these materials display acceptable characteristics: the flexural and compression strength are around 4.6 and 26 MPa respectively, for an added calcium carbonate over dry matter ration up to 12% by weight.The promising results exposed in this paper show that the geopolymer formulations can be adapted for applications in construction and civil engineering structures as an alternative to conventional materials.