Error Analysis of Written English Compositions: The Case of Learners of Prime University in Bangladesh

This study aims at finding out that the error analyses and correction came be the best starting to develop the learners   writing skill. The researcher under takes to investigate the errors in a collection of 50 essays written by 50 students if 1st semester of B.A (Hon’s) in English in the department of English at Prime University. The researcher attempts to balance between male and female students. Errors were found and categories according to various grammatical classifications. The scrolls in this study show that the students committed 15 errors: i) Capitalization ii) Article iii)Subject Verb agreement iv)Discontinuous constituentsv)Nounvi) Pronounvii) Word of orderviii) Modalsix) Degree or Adjectivex) Verbxi) Tag question xii) Conditional xiii) Nouns in Apposition xiv) Prepositionxv) Punctuation Keywords: error analysis, essay, writing, grammatica

Multifunctional Nanomaterials for Energy Applications

In the last few decades, global energy requirements have grown exponentially, and increased demand is expected in the upcoming decades [...

Multifunctional Conductive Paths Obtained by Laser Processing of Non-Conductive Carbon Nanotube/Polypropylene Composites

Functional materials are promising candidates for application in structural health monitoring/self-healing composites, wearable systems (smart textiles), robotics, and next-generation electronics. Any improvement in these topics would be of great relevance to industry, environment, and global needs for energy sustainability. Taking into consideration all these aspects, low-cost fabrication of electrical functionalities on the outer surface of carbon-nanotube/polypropylene composites is presented in this paper. Electrical-responsive regions and conductive tracks, made of an accumulation layer of carbon nanotubes without the use of metals, have been obtained by the laser irradiation process, leading to confined polymer melting/vaporization with consequent local increase of the nanotube concentration over the electrical percolation threshold. Interestingly, by combining different investigation methods, including thermogravimetric analyses (TGA), X-ray diffraction (XRD) measurements, scanning electron and atomic force microscopies (SEM, AFM), and Raman spectroscopy, the electrical properties of multi-walled carbon nanotube/polypropylene (MWCNT/PP) composites have been elucidated to unfold their potentials under static and dynamic conditions. More interestingly, prototypes made of simple components and electronic circuits (resistor, touch-sensitive devices), where conventional components have been substituted by the carbon nanotube networks, are shown. The results contribute to enabling the direct integration of carbon conductive paths in conventional electronics and next-generation platforms for low-power electronics, sensors, and devices

Direct Selective Laser Synthesis of CuCrFeNiTiAl High Entropy Alloy from Elemental Powders through Selective Laser Melting

This study investigated the synthesis of CuCrFeNiTiAl high entropy alloy (HEA) from pure elements using selective laser melting (SLM). The objectives are to validate the feasibility of the HEA fabrication from elemental powder materials, and to examine the effect of various process conditions in SLM, such as laser power, point distance and laser exposure time, on the microstructures formed. The as-built samples under high, medium and low energy densities were characterized by X-ray diffraction (XRD), and the microstructures were observed using scanning electron microscopy (SEM). The XRD results showed that five major crystal structure phases (hexagonal, monoclinic, orthorhombic, body-centered cubic and rhombohedral) were present in all samples. Fine-grained phases were noticed on the sample surface with non-uniform microstructural distribution. Such phases in high and low energy density samples were observed polygonal while round-shaped microstructures were observed for samples prepared under medium energy density conditions. Also, the grain size was proportional to energy levels of the fabrication process. Large size and clustered structures are prominent in samples produced under high energy density

Functional materials, device architecture, and flexibility of perovskite solar cell

Perovskite solar cells (PSCs) are an emerging photovoltaic technology that promises to offer facile and efficient solar power generation to meet future energy needs. PSCs have received considerable attention in recent years, have attained power conversion efficiencies (PCEs) over 22%, and are a promising candidate to potentially replace the current photovoltaic technology. The emergence of PSCs has revolutionized photovoltaic research and development because of their high efficiencies, inherent flexibility, the diversity of materials/synthetic methods that can be employed to manufacture them, and the various possible device architectures. Further optimization of material compositions and device architectures will help further improve efficiency and device stability. Moreover, the search for new functional materials will allow for mitigation of the existing limitations of PSCs. This review covers the recently developed advanced techniques and research trends related to this emerging photovoltaic technology, with a focus on the diversity of functional materials used for the various layers of PSC devices, novel PSC architectures, methods that increase overall cell efficiency, and substrates that allow for enhanced device flexibility

Functionalized Thermoplastic Polyurethane Nanofibers: An Innovative Triboelectric Energy Generator

A triboelectric nanogenerator (TENG) is one of the most significantly innovative microdevices for built-in energy harvesting with wearable and portable electronics. In this study, the forcespinning technology was used to synthesize a nanofiber (NF) mat-based TENG. Polyvinylidene fluoride (PVDF) membrane was used as the negative triboelectric electrode/pole, and chemically designed and functionalized thermoplastic polyurethane (TPU) was used as the positive electrode/pole for the TENG. The electronic interference, sensitivity, and gate voltage of the synthesized microdevices were investigated using chemically modified bridging of multi-walled carbon nanotubes (MWCNT) with a TPU polymer repeating unit and bare TPU-based positive electrodes. The chemical functionality of TPU NF was integrated during the NF preparation step. The morphological features and the chemical structure of the nanofibers were characterized using a field emission scanning electron microscope and Fourier-transform infrared spectroscopy. The electrical output of the fabricated MWCNT-TPU/PVDF TENG yielded a maximum of 212 V in open circuit and 70 µA in short circuit at 240 beats per minute, which proved to be 79% and 15% higher than the TPU/PDVF triboelectric nanogenerator with an electronic contact area of 3.8 × 3.8 cm2, which indicates that MWCNT enhanced the electron transportation facility, which results in significantly enhanced performance of the TENG. This device was further tested for its charging capacity and sensory performance by taking data from different body parts, e.g., the chest, arms, feet, hands, etc. These results show an impending prospect and versatility of the chemically functionalized materials for next-generation applications in sensing and everyday energy harvesting technology

On the thermogravimetric analysis of polymers: Polyethylene oxide powder and nanofibers

Thermogravimetric analysis of polyethylene oxide (powder and nanofibers obtained by force spinning water or chloroform solutions of polyethylene oxide) was studied using different theoretical models such as Friedman and Flynn-Wall-Ozawa. A semiempirical approach for estimating the “sigmoid activation energy” from the thermal degradation was suggested and confirmed by the experimental data on PEO powder and nanofibers\u27 mats. The equation allowed for calculating a “sigmoid activation energy” from a single thermogram using a single heating rate without requiring any model for the actual complex set of chemical reactions involved in the thermal degradation process. For PEO (powder and nanofibers obtained from water solutions), the “sigmoid activation energy” increased as the heating rate was increased. The sigmoid activation energy for PEO mats obtained from chloroform solutions exhibited a small decrease as the heating rate was increased. Thermograms\u27 derivatives were fitted to determine the coordinates of the inflection points. The “sigmoid activation energy” was compared to the activation energy determined from the Flynn-Wall-Ozawa model. Similarities between the thermal degradation of polyethylene oxide powder and of the nanofibers obtained from water solutions were discussed. Significant differences between the sigmoid activation energies of the mats obtained from water and chloroform solutions were reported

A photoanode with hierarchical nanoforest TiO 2 structure and silver plasmonic nanoparticles for flexible dye sensitized solar cell

Due to unique photovoltaic properties, the nanostructured morphologies of TiO2 on flexible substrate have been studied extensively in the recent years for applications in dye sensitized solar cells (DSSCs). Microstructured electrode materials with high surface area can facilitate rapid charge transport and thus improve the light-to-current conversion efficiency. Herein we present an improved photoanode with forest like photoactive TiO2 hierarchical microstructure using a simple and facile hydrothermal route. To utilize the surface plasmon resonance (SPR) and hence increase the photon conversion efficiency, a plasmonic nanoparticle Ag has also been deposited using a very feasible photoreduction method. The branched structure of the photoanode increases the dye loading by filling the space between the nanowires, whereas Ag nanoparticles play the multiple roles of dye absorption and light scattering to increase the light-to-current conversion efficiency of the device. The branched structure provides a suitable matrix for the subsequent Ag deposition. They improve the charge collection efficiency by providing the preferential electron pathways. The high-density Ag nanoparticles deposited on the forest like structure also decrease the charge recombination and therefore improve the photovoltaic efficiency of the cells. As a result, the DSSC based on this novel photoanode shows remarkably higher photon conversion efficiency (ηmax = 4.0% and ηopt = 3.15%) compared to the device based on pristine nanowire or forest-like TiO2 structure. The flexibility of the device showed sustainable and efficient performance of the microcells

Surface modified hybrid ZnSnO3 nanocubes for enhanced piezoelectric power generation and wireless sensory application

Piezoelectric Nanogenerators (PENGs), which can convert ambient mechanical stimuli into electrical energy, are held in high regard due to their cost-effectiveness, energy harvesting applications, and potential as self-powered sensors. We report an aluminum-doped zinc stannate (ZnSnO3) PENG that can achieve high electrical outputs with respect to the external force. In order to enrich the piezoelectric mechanics, a low-temperature solution method was adopted in our work to synthesize ZnSnO3 nanocubes with an average side length of only 30 – 55 nm. Furthermore, ZnSnO3 was doped with 1 wt% to 5 wt% of aluminum nanoparticles. We report that 2 wt% of aluminum doped ZnSnO3 showed the highest electrical output in terms of open circuit voltages and short circuit current. The nanogenerator device achieved an average open-circuit voltage of 80 V to 175 V with a frequency range of 60 BPM (Beats Per Minute) to 240 BPM, an unprecedented electrical output in comparison to current ZnSnO3 -based PENGs. With the presented high output-to-size ratio taken into consideration, the device was mounted in a helmet and tested as an energy harvester and wireless human motion sensor, which can generate electric charge as well as detect human movements and transmit the corresponding signals wirelessly. Our work- is indicative of a promising smart helmet using organic-inorganic hybrid materials