Experimental and numerical investigations of low velocity impact behavior of high-performance fiber-reinforced cement based composite

Fiber-reinforced concrete (FRC) has been used in structural applications in order to enhance the structural performance under dynamic loading and reduce cracking and spalling phenomena by increasing toughness, ductility, and tensile strength of the concrete. High-performance fiber-reinforced cement based composite (HPFRC) is a high-strength FRC with enhanced high-performance characteristics. Recent studies have shown that HPFRC has higher impact resistance than other types of concrete. Therefore, it has been widely considered as a promising material for the construction of important and strategic structures. HPFRC panels are tested by drop projectiles up to an impact at which failure occurs. Mechanical properties of HPFRC are obtained to define material parameters in the MAT_SOIL_CONCRETE model in LS-DYNA, which is used to simulate the behavior of HPFRC panel under impact loading and perform parametric studies. Predicted crack and failure patterns on both sides of the HPFRC panel based on finite element simulation are in good agreement with their corresponding experimental results.     

Benefits valuation of potable water quality improvement in Malaysia: the case of Kajang Municipality

This article estimates the benefits of potable water quality improvements in Kajang Municipality in the state of Selangor, Malaysia, using the avertive cost method. Households were willing to pay MYR 322 annually to improve potable water quality. This represents about 80% of their average annual water bill. The present value of aggregate benefits over a period of 30 years at various social discount rates ranged from MYR 301 million to MYR 768 million. These estimates can be used as a reference for public investment criteria. The findings suggest that there is merit in an upward revision of water tariffs if they provide improvements in water quality.     

Synthesis and characterization of alumina supported sub-nanoporous SiO2–10 wt%TiO2 membrane for nitrogen separation

Membrane of SiO₂–10TiO₂ was produced by dip coating on mesoporous-titania-coated macroporous alumina support. The amorphous SiO₂–10TiO₂ top layer with thickness of 0.9 μm was obtained as a homogenous and defect free surface. Gas permeation tests show a decrease in permeation in order of CH₄ > N₂ for the support, and N₂ > CH₄ for the multilayer membrane. The membrane delivering promised single gas separation factor for N₂/CH₄ (1.75). It was also observed that the membrane separation factor in binary gas mixture was 12–15% of the single gas separation factor, while the permeation revealed a decrease in gas mixture.     

High‐yield synthesis of multi‐walled carbon nanotube by hydrothermal method

The evolution of multi‐walled carbon nanotubes (MWCNTs) under hydrothermal condition was investigated, because the hydrothermal method (HTM) has been utilised for commercial production of advanced engineering materials. To synthesise MWCNTs by hydrothermal process using mixed aqueous solution diethylenetriamine, polyethyleneglycol (PEG) and NaOH were used as starting materials. We investigated the effect of hydrothermal temperature, time, and amount of formative compounds. Hydrothermal reaction temperature was in the range from 150 to 180°C. The aim of the present work is to presentation hydrothermal synthesis as a new processing method for fabrication of MWCNTs, without the addition of metal catalyst. The homogeneity of hydrothermal processes, cheapness, and availability of amorphous carbon materials, without the need of catalyst, are advantages favouring the scaling‐up of the new method. The treatment of higher volumes would only require autoclaves with increasing load‐bearing capacity. Synthesised MWCNTs were analysed with a scanning electron microscope (SEM), a high resolution transmission electron microscope (HRTEM), thermo‐gravimetric analysis (TGA), and Raman spectroscopy. This result also presented a controllable way to synthesise MWCNTs with high purity. Indeed, present work will introduce new chapter in synthesising MWCNTs for scientific and engineering.     

Copper-phthalocyanine and nickel nanoparticles as novel cathode catalysts in microbial fuel cells

In this study, four different catalysts (i.e., carbon black, nickel nanoparticle (Ni)/C, Phthalocyanine/C and copper-phthalocyanine/C), were tested in a two-chamber Microbial Fuel Cell (MFC) and their performances were compared with Pt as the common cathode catalyst in MFC. The characterization of catalysts was done by TEM, XPS and EDX and their electrochemical characteristics were compared by cyclic voltammetry (CV) and Linear Sweep Voltammetry (LSV). The results proved that copper phthalocyanine and nickel nanoparticles are potential alternatives catalyst for Pt. Even copper-phthalocyanine generated power is almost the same as Pt. The CV and LSV results reported high electrochemical activity of these catalysts. The maximum power density and coulombic efficiency was achieved by copper-phthalocyanine/C as 118.2 mW/m² and 29.3%.     

A novel bandwidth efficient SOC-based turbo coding scheme mid reduced complexity MUD for SA-based MC-CDMA systems

Multiuser-detection (MUD), turbo coding and smart-antennas (SA) are powerful techniques for enhancing the performance and capacity of MC-CDMA systems. Among the MUD algorithms, the maximum-likelihood (ML) method has the best performance but its complexity increases exponentially with the number of users and constellation size. In this paper, we first propose a novel bandwidth-efficient-channel-coding-scheme (BECCS) for a super-orthogonal-code (SOC)-based serially concatenated turbo code (SCSOC) so that by using it, the coded system without extra bandwidth significantly improves the performance of an uncoded system over a fading channel. Second, in order to reduce the complexity of the ML-based turbo MUD technique, an ML algorithm based on the sensitive-bits-algorithm (SBA) and a less-complex-norm-approximation (LCNA) based Euclidean distance is proposed for a SCSOC-based BECCS assisted coded MC-CDMA system accompanied by SA techniques at the receiver. Our analytical and simulation results show that from a performance perspective, at BER=10^?2, the proposed SCSOC-based BECCS assisted MC-CDMA system performs 4?dB better than SOC-based coded systems. The latter system has 5?dB gain in comparison with an uncoded one, all in the same bandwidth and over fading channels.     

Thermochemical principles of the production of lightweight aggregates from waste coal bottom ash

Manufacturing lightweight aggregate (LWA) (ie, porous ceramics) by means of a sintering technique requires a delicate balance among three conditions: (a) forming a sufficient amount of molten liquid phase during sintering, (b) reaching an appropriate viscosity for solid-liquid suspension, and (c) emitting a sufficient amount of gas that can be entrapped by the liquid phase to form pores. This study evaluates these three conditions in the production of LWAs made from two types of waste coal bottom ash (low-calcium and high-calcium), and relates them to the formation of LWA pore structure. A thermochemical analytical approach, including thermodynamic modeling and the Browning viscosity model, was used to quantify the extent of the liquid phase and calculate its viscosity. In conjunction with thermochemical analysis, an experimental approach including quantitative x-ray diffractometry, thermogravimetric analysis, and x-ray computed tomography was also used to identify the candidate chemical compounds that contribute to gas emission during sintering and to evaluate the LWA pore structure. The results indicated that a mass fraction of at least 50% for the liquid phase is required for a successful entrapment of emitted gaseous phases during sintering. Larger pores were observed in the microstructure of LWA samples made using high-calcium bottom ash in comparison to those made with low-calcium bottom ash. This observation was mainly attributed to the high-calcium samples forming liquid phases with lower viscosities and emitting higher amounts of gaseous phase during sintering than did the low-calcium samples. It was found that the gaseous phase was generated by hematite reduction and anhydrite decomposition, which led to the release of O₂ and SO₂.     

Kinetic Study of the Reduction Step for Chemical Looping Steam Methane Reforming by CeO2-Fe2O3 Oxygen Carriers

The reduction stage of chemical looping steam methane reforming was investigated to determine the kinetics of the reduction reaction for CeO₂-Fe₂O₃ mixed oxides. CeO₂, Fe₂O₃, and CeO₂-Fe₂O₃ mixed oxides with different molar ratios were prepared by chemical precipitation. Characterization tests indicated the lowest Brunauer-Emmett-Teller surface area for samples with higher Fe content. The largest area under reduction peaks during hydrogen temperature-programmed reduction measurements was also related to the samples with highest Fe content. Reduction of the oxygen carriers with lower Fe content was well represented by a phase boundary-controlled model.