Experimental and analytical study of carbon fiber-reinforced polymer (FRP)/autoclaved aerated concrete (AAC) sandwich panels

The structural behavior of hybrid fiber-reinforced polymer (FRP)–autoclaved aerated concrete (AAC) panels has been investigated. FRP laminates can be used to reinforce externally the plain AAC producing a very high stiff panel. The resulting hybrid FRP/AAC panel can be used as structural or non-structural member for the housing construction. In order to accomplish this, FRP/AAC panels have been fabricated and prepared for testing. The specimens have been processed using the advanced semi-mechanical processing technique VARTM (Vacuum Assisted Resin Transfer Molding). The concept of the FRP/AAC panel is based on the theory of sandwich construction with strong and stiff skins, like FRP composites, bonded to a core material, like AAC panel. The FRP composite material was made of carbon reinforcing fabrics embedded in an epoxy resin matrix. The panels were tested under four-point bending test to investigate their strength and ductility responses using a Tinius–Olsen Universal Testing Machine. Experimental results showed a significant influence of FRP laminates on both strength and ductility of the FRP/AAC panels. A theoretical analysis was conducted to predict the strength of the FRP/AAC member and results found were in good accordance with the experimental ones.     

Common gate cross-coupled differential amplifier for near-field sensors

A differential amplifier with an input stage of a common gate cross-coupled differential type is presented. The first and the two other common source differential stages are connected via single-ended source follower type level shifting buffers. Feedback circuitry is added to compensate the offset owing to the process, temperature and supply mismatches of the transistors at the input differential stage. The amplifier is designed using OMMIC ED02AH GaAs technology having a semi-insulating substrate which is advantageous for monolithic integration of low-loss passive elements such as loops. The realised amplifier achieves a gain of greater than 28 dB over a bandwidth of 10 GHz.     

Antioxidative Potential of the Polyphenolics of Stephania japonica var. Discolor (Blume) Forman: A Chromatographic (High-Performance Liquid Chromatography) and Spectrophotometric Measure

This study investigated the quantitative phytochemical contents, total phenolics, total flavonoids, total carotenoids, antioxidative capacity, tannin, proanthocyanidins, lycopene, chlorophyll a, and chlorophyll b of the Stephania japonica extract. Comprehensive antioxidative effects of the extract were also investigated. Quantitative assays were conducted through both spectrophotometric and high-performance liquid chromatographic methods. Antioxidative effects were measured through FeCl₃ reducing power, metal chelating power, reducing power, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) scavenging activity, N, N-dimethyl-1,4-diaminobenzene free radical scavenging activity, superoxide radical scavenging activity, and nitric oxide scavenging effect. The contents of total phenolics, total flavonoids, total carotenoids, total antioxidative capacity, tannin, proanthocyanidins, lycopene, chlorophyll a, and chlorophyll b were found to be 47.32 ± 0.75 mg tannic acid equivalent, 61.41 ± 1.58 mg catechin equivalent, 63.29 ± 2.21 mg, 22.85 ± 0.70 mg ascorbic acid equivalent, 76.17 ± 0.97 mg tannic acid equivalent, 94.96 ± 4.49 mg catechin equivalent, 22.19 ± 0.79 µg, 22.19 ± 0.79 µg, 7.52 ± 1.24 mg, and 10.43 ± 2.11 mg, respectively, in 1 g of ethanol extract. A high concentration of epicatechin, p-coumaric acid, and rutin hydrate and moderate concentration of caffeic acid and quercetin was detected in the extract. The IC₅₀ value for ferric reducing power assay, metal chelating assay, reducing power assay, ABTS scavenging assay, N, N-dimethyl-1,4-diaminobenzene scavenging assay, superoxide scavenging assay and nitric oxide (NO) assay were 465.06 ± 7.32 µmol ascorbic acid/g, 1656.52, 270.55, 457.27, 632.74, 217.5, and 464.00 µg/mL, respectively. No beta carotene was detected in the extract. The extract was demonstrated to be a very potential source of antioxidative metabolites.     

Drivers for plant species diversity in a characteristic tropical forest landscape in Bangladesh

The importance of understanding biotic patterns in managed tropical landscapes is increasingly recognised. Bangladesh is a country with a long human land-use history and constitutes almost a blind spot in vegetation science on the landscape scale. Here, we analyse patterns and drivers of plant species richness and community composition along a land-use intensity gradient in a forest landscape including tea gardens, tree plantations and nature reserves (Satchari Reserved Forest) based on multivariate approaches and variation partitioning. We find richness as well as composition of tree and understory species to directly relate to a disturbance gradient that reflects protection status and elevation. This is astonishing, as the range in elevation (70 m) is small. Topography and protection remain significant drivers of biodiversity after correcting for human disturbances. While tree and non-tree species richness were positively correlated, they differ considerably in their relation to other environmental or disturbance variables as well as in the spatial richness pattern. The disturbance regime particularly structures tree species richness and composition in protected areas. We conclude by highlighting the importance of explicitly integrating human–biosphere interactions in any nature protection strategy for the study region.     

A new approach for fuel injection into a solar receiver/ reactor: Numerical and experimental investigation

An innovative and efficient design of solar receivers/reactors can enhance the production of clean fuels via concentrated solar energy. This study presents a new jet-type burner nozzle for gaseous feedstock injection into a cavity solar receiver inspired from the combustion technology. The nozzle design was adapted from a combustion burner and successfully implemented into a solar receiver and studied the influence of the nozzle design on the fluid mixing and temperature distribution inside the solar receiver using a 7 kW solar simulator and nitrogen as working fluid. Finally, a thorough computational fluid dynamics (CFD) analysis was performed and validated against the experimental results. The CFD results showed a variation of the gas flow pattern and gas mixing after the burner nozzle adaptation, which resulted an intense effect on the heat transfer inside the solar receiver.

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Plasmodium life cycle stage classification based quantification of malaria parasitaemia in thin blood smears

Visual inspection for the quantification of malaria parasitaemiain (MP) and classification of life cycle stage are hard and time taking. Even though, automated techniques for the quantification of MP and their classification are reported in the literature. However, either reported techniques are imperfect or cannot deal with special issues such as anemia and hemoglobinopathies due to clumps of red blood cells (RBCs). The focus of the current work is to examine the thin blood smear microscopic images stained with Giemsa by digital image processing techniques, grading MP on independent factors (RBCs morphology) and classification of its life cycle stage. For the classification of the life cycle of malaria parasite the k‐nearest neighbor, Naïve Bayes and multi‐class support vector machine are employed for classification based on histograms of oriented gradients and local binary pattern features. The proposed methodology is based on inductive technique, segment malaria parasites through the adaptive machine learning techniques. The quantification accuracy of RBCs is enhanced; RBCs clumps are split by analysis of concavity regions for focal points. Further, classification of infected and non‐infected RBCs has been made to grade MP precisely. The training and testing of the proposed approach on benchmark dataset with respect to ground truth data, yield 96.75% MP sensitivity and 94.59% specificity. Additionally, the proposed approach addresses the process with independent factors (RBCs morphology). Finally, it is an economical solution for MP grading in immense testing .     

Performance of interior permanent magnet motor drive over widespeed range

This paper investigates the performance of an interior permanent magnet synchronous motor (IPMSM) drive over wide speed range for high precision industrial applications. The scheme incorporates the maximum torque per ampere (MTPA) operation in constant torque region and the flux-weakening operation in constant power region in order to expand the operating limits for an IPMSM. Improved mathematical expressions are derived to analyze the performances of the IPMSM. The power ratings of the motor and the inverter are considered. The effects of motor parameters particularly, the saliency ratio (X_q/X_d) on the voltage limit constraint and the power capability of the inverter are also investigated. The efficacy of the above mentioned drive system and the improved steady-state analysis are evaluated by both experimental and computer simulation results. The complete drive is implemented in real-time using digital signal processor (DSP) controller board DS 1102 on a laboratory 1 hp interior permanent magnet synchronous motor     

Low velocity impact response of autoclaved aerated concrete/CFRP sandwich plates

Autoclaved aerated concrete (AAC)-CFRP composites have proven to be structurally efficient combinations for lightweight structural components such as floor beams, lintels, walls or columns. Besides the need to possess adequate flexural properties, AAC/CFRP structures need to be evaluated for their ability to withstand localized damage. During service, the before mentioned structural members are subjected to impact loading that varies from localized object impact, blast due to explosions, or to high velocity impact of debris during tornados, hurricanes, or storms. The objective of this paper is to evaluate the response of AAC/CFRP sandwich structures to low velocity impact (LVI) and to compare the experimental results to the predicted energy absorptions values given by an energy balance model. AAC/CFRP panels are prone to heavy object impacts under relatively low velocities such as in the case of object/tool drops on floor beams or low velocity collisions against columns.     

Effect of neutralization of poly(methacrylic acid-co-ethyl acrylate) on drug release from enteric-coated pellets upon accelerated storage

The effect of neutralization of poly(methacrylic acid-co-ethyl acrylate) or poly(MA-EA) 1:1 (Eudragit^® L 30 D-55) on drug release from enteric-coated pellets was studied upon accelerated storage. The dissolution rate of un-neutralized poly(MA-EA)-coated pellets decreased while the neutralized polymer-coated pellets maintained a constant drug release rate. Dynamic mechanical analysis showed that both un-neutralized and neutralized poly(MA-EA) films became rigid on aging. However, the un-neutralized films were affected more than those neutralized. Neutralization of poly(MA-EA) significantly changed the mechanical properties of coating films and improved the stability of poly(MA-EA) enteric-coated pellets upon accelerated storage at the studied conditions.     

Chloride ingress and macro-cell corrosion of steel in concrete made with recycled brick aggregate

An investigation on chloride ingress and macro-cell corrosion of steel bars in concrete made with recycled brick aggregate (RBA) was carried out. As control cases, virgin brick aggregate (BA) and stone aggregate (SA) were also investigated. Both cylindrical and cracked prism specimens were studied for 16 different cases. The prism specimens were made with a segmented steel bar providing electrical connection from outside of the specimens to measure macro-cell corrosion current continuously under seawater splash exposure for a period of 30 d using a data logger. Cylindrical specimens were submerged in 3% NaCl solution at a temperature of 40°C to investigate chloride ingress in concrete made with RBA, BA, and SA after 120 and 180 d. Half-cell potential, corrosion area, and depths of corrosion were also investigated. The chloride ingress as well as corrosion of steel bars in concrete made with the different types of aggregate is ordered as RBA > BA > SA.