Unglazed Fiberglass Reinforced Polyester Solar Water Heater with Integrated Storage System

Theoretical and experimental investigations on an unglazed solar hot water heater with integrated storage system were conducted. The system was comprised of a collector and storage tank which was integrated into one unit. All parts of the system have been fabricated from fiberglass reinforced polyester (GFRP). The absorber plate has water tubes of semielliptical shape. The width and length of the absorber plate were 1.4 and 1.8?m, respectively. The absorber plate was fabricated from GFPR using a special resin composition that provides good thermal conductivity and absorptivity. The storage tank has a capacity of 496?L. The storage tank is of sandwich construction with a core material made of polyurethane foam that combines stiffness and lightness of the structure with very good thermal insulation properties. An average tank temperature of 53°C was achieved at an average solar radiation level of 700?W/m2 and ambient temperature of 28°C. The thermal efficiencies of the system were evaluated at 48 and 57% for cloudy and clear days, respectively. Transient performance of the system was predicted by solving the mathematical models consisting of energy balance equations of the system that have been converted to finite difference form and solved by a personal computer. The experimental results were in close agreement as has been found with the theoretical predictions.     

Constant and high switching frequency torque controller for DTC drives

The letter presents a new method of increasing the switching frequency of a direct torque control (DTC) of induction machines. The method simply replaces the hysteresis comparator of the conventional DTC drives with a triangular waveform-based constant switching frequency controller. By synchronizing the digital signal processor (DSP) sampling with a triangular waveform and with an appropriate systematic controller design, a high switching frequency DTC drive is possible without requiring a high-frequency space-vector modulator. The implementation of the controller is simple and operates based on waveform comparisons; in this letter it is implemented using a combination of a DSP and a field programmable gate array device. Simulation and experimental results indicate that the controller both reduces the torque ripple and maintains a constant switching frequency.     

Project management deployment: The role of cultural factors

This paper investigates the role of cultural factors as possible partial explanation of the disparity in terms of project management deployment observed between various studied countries. The topic of culture has received increasing attention in the management literature in general during the last decades and in the project management literature in particular during the last few years. The globalization of businesses and worldwide Governmental/International organizations collaborations drives this interest in the national culture to increase more and more. Based on Hofstede national culture framework, the study hypothesizes and tests the impact of the culture and development of the country on the PM deployment. Seventy-four countries are selected to conduct a correlation and regression analysis between Hofstede’s national culture dimensions and the used PM deployment indicator. The results show the relations between various national culture dimensions and development indicator (GDP/Capita) on the project management deployment levels of the considered countries.     

Failure Analysis of Seawater Inlet Pipe

A seawater inlet pipe failed in service. The visual examination showed that the backing bar was present inside the pipe and the failure was characterized by leaks at approximately 4–8 o’clock position near that backing bar. The finite element analysis of fluid in the seawater inlet pipe showed that the eddy zone was formed near the backing bar. The leaks and crater-like surfaces were noticed on the inner pipe surface at which the finite element analysis modeled the possibility of the formation of eddy zone.     

Crystal Structure and Physicochemical Properties of Two Supramolecular Compounds: (C4H8NH2)4[Mo8O26] and (NH4)Na2[AsIIIMo6O21(O2CCH2NH3)3]·8H2O

Two inorganic–organic hybrid supramolecular compounds based on polyoxometalates formulated as (C₄H₈NH₂)₄[Mo₈O₂₆] (1) and (NH₄)Na₂[As^IIIMo₆O₂₁(O₂CCH₂NH₃)₃]·8H₂O (2) have been synthesized by conventional solution method and characterized by infrared, UV–Vis and single-crystal X-ray diffraction analyses. Thermal analysis was performed to study their thermal stability. The atomic arrangement in compound (1) can be described as inorganic layers built by [Mo₈O₂₆]^4?, pyrrolidinium cations are embedded into layers. The fascinating structural feature of compound (2) is that the glycine molecules are bounded to two edge-sharing Mo centers via their carboxylate functionality leading to functionalized heteropolymolybdate [As^IIIMo₆O₂₁(O₂CCH₂NH₃)₃]^3?, extensive net hydrogen bonds between cations and anions contribute to the crystal packing. The electrochemical behavior of compound (2) has been studied.     

Performance analysis of a double-pass photovoltaic/thermal (PV/T) solar collector with CPC and fins

The use of PV/T in combination with concentrating reflectors has a potential to significantly increase power production from a given solar cell area. A prototype double-pass photovoltaic-thermal solar air collector with CPC and fins has been designed and fabricated and its performance over a range of operating conditions was studied. The absorber of the hybrid photovoltaic/thermal (PV/T) collector under investigation consists of an array of solar cells for generating electricity, compound parabolic concentrator (CPC) to increase the radiation intensity falling on the solar cells and fins attached to the back side of the absorber plate to improve heat transfer to the flowing air. Energy balance equations have been developed for the various nodes of the system. Both thermal and electrical performance of the collector are presented and discussed.     

Transport properties study of supplementary cementitious materials: case of tuff,limestone filler and granodiorite

The aim of this research is to determine the effects of replacing cement with tuffs on the transport properties and service life of cement-based materials. Specimens were prepared replacing 5% and 15% by weight of cement with both white and brown tuffs. Additional specimens were prepared replacing cement with 5% and 15% limestone filler and granodiorite to compare the effects of these types of materials. For these four types of specimen as well as a control mortar with no cement replacement transport properties (gas permeability and chloride ingress) were measured as well as porosity and pore diameter. The transport properties were compared the changes in these porosity and pore diameter. Based on the results, white tuff significantly improves the transport properties of the mortars due to its pozzolanic reaction and that white tuff may be an economically and functionally viable replacement for cement where concrete durability is important. Pore diameter and porosity did not correlate well with transport properties.     

Polymeric Microspheres/Cells/Extracellular Matrix Constructs Produced by Auto-Assembly for Bone Modular Tissue Engineering

Modular tissue engineering (MTE) is a novel “bottom-up” approach to create engineered biological tissues from microscale repeating units. Our aim was to obtain microtissue constructs, based on polymer microspheres (MSs) populated with cells, which can be further assembled into larger tissue blocks and used in bone MTE. Poly(L-lactide-co-glycolide) MS of 165 ± 47 µm in diameter were produced by oil-in-water emulsification and treated with 0.1 M NaOH. To improve cell adhesion, MSs were coated with poly-L-lysine (PLL) or human recombinant collagen type I (COL). The presence of oxygenated functionalities and PLL/COL coating on MS was confirmed by X-ray photoelectron spectroscopy (XPS). To assess the influence of medium composition on adhesion, proliferation, and osteogenic differentiation, preosteoblast MC3T3-E1 cells were cultured on MS in minimal essential medium (MEM) and osteogenic differentiation medium (OSG). Moreover, to assess the potential osteoblast–osteoclast cross-talk phenomenon and the influence of signaling molecules released by osteoclasts on osteoblast cell culture, a medium obtained from osteoclast culture (OSC) was also used. To impel the cells to adhere and grow on the MS, anti-adhesive cell culture plates were utilized. The results show that MS coated with PLL and COL significantly favor the adhesion and growth of MC3T3-E1 cells on days 1 and 7, respectively, in all experimental conditions tested. On day 7, three-dimensional MS/cell/extracellular matrix constructs were created owing to auto-assembly. The cells grown in such constructs exhibited high activity of early osteogenic differentiation marker, namely, alkaline phosphatase. Superior cell growth on PLL- and COL-coated MS on day 14 was observed in the OSG medium. Interestingly, deposition of extracellular matrix and its mineralization was particularly enhanced on COL-coated MS in OSG medium on day 14. In our study, we developed a method of spontaneous formation of organoid-like MS-based cell/ECM constructs with a few millimeters in size. Such constructs may be regarded as building blocks in bone MTE.     

A new efficient backward BSS crosstalk-resistant algorithm for automatic blind speech quality enhancement

In last 10 years, several noise reduction (NR) algorithms have been proposed to be combined with the blind source separation techniques to separate speech and noise signals from blind noisy observations. More often, techniques use voice activity detector (VAD) systems for the optimal solution. In this paper, we propose a new backward blind source separation (BBSS) structure that uses the input correlation properties to provide: (i) high convergence rates and good tracking capabilities, since the acoustic environments imply long and time-variant noise paths, and (ii) low misalignment and robustness against different noise type variations and double-talk. The proposed algorithm has an automatic behavior to enhance noisy speech signals, and do not need any VAD systems to separate speech and noise signals. The obtained results in terms of several objective criteria show the good performance properties of the proposed algorithm in comparison with state-of-the-art algorithms.