Search results for: recycling materials

Authors: Md Rabiul Islam, Ben Wadham

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This paper describes how indigenous students face challenges with various school activities due to inadequate equity and diversity principles in mainstream primary schools in Bangladesh. This study focuses on indigenous students’ interactions with mainstream class teachers and students through teaching-learning activities at public primary schools. Ethnographic research methods guided data collection under a case study methodology in Chittagong Hill Tracts (CHTs) region where maximum indigenous peoples’ inhabitants. The participants (class teachers) shared information through in-depth interviews about their experiences in the four selecting schools. The authors also observed the effects of school activities by use of equity and diversity lens for indigenous students’ situations in those schools. The authors argue that the socio-economic situations of indigenous families are not supportive of the educational development of their children. Similarly, the Bangladesh government does not have enough initiative programs based on equity and diversity principles for fundamental education of indigenous children at rural schools level. Besides this, the conventional teaching system cannot improve the diversification among the students in classrooms. The principles of equity and diversity are not well embedded in professional development of teachers, and using teaching materials in classrooms. The findings suggest that implementing equitable education; there are needed to arrange teachers’ education with equitable knowledge and introducing diversified teaching materials, and implementing teaching through students centered activities that promote the diversification among the multicultural students.

Keywords: case study research, chittagong hill tracts, equity and diversity, Indigenous children

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Authors: Vlad Andrei Raducanu, Mariana Lucia Angelescu, Ion Cinca, Vasile Danut Cojocaru, Doina Raducanu

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By using smart digital tools, such as generative design (GD) and digital fabrication (DF), problems of high actuality concerning resources optimization (materials, energy, time) can be solved and applications or products of free-form type can be created. In the new digital technology materials are active, designed in response to a set of performance requirements, which impose a total rethinking of old material practices. The article presents the design procedure key steps of a free-form architectural object - a column type one with connections to get an adaptive 3D surface, by using the parametric design methodology and by exploiting the properties of conventional metallic materials. In parametric design the form of the created object or space is shaped by varying the parameters values and relationships between the forms are described by mathematical equations. Digital parametric design is based on specific procedures, as shape grammars, Lindenmayer - systems, cellular automata, genetic algorithms or swarm intelligence, each of these procedures having limitations which make them applicable only in certain cases. In the paper the design process stages and the shape grammar type algorithm are presented. The generative design process relies on two basic principles: the modeling principle and the generative principle. The generative method is based on a form finding process, by creating many 3D spatial forms, using an algorithm conceived in order to apply its generating logic onto different input geometry. Once the algorithm is realized, it can be applied repeatedly to generate the geometry for a number of different input surfaces. The generated configurations are then analyzed through a technical or aesthetic selection criterion and finally the optimal solution is selected. Endless range of generative capacity of codes and algorithms used in digital design offers various conceptual possibilities and optimal solutions for both technical and environmental increasing demands of building industry and architecture. Constructions or spaces generated by parametric design can be specifically tuned, in order to meet certain technical or aesthetical requirements. The proposed approach has direct applicability in sustainable architecture, offering important potential economic advantages, a flexible design (which can be changed until the end of the design process) and unique geometric models of high performance.

Keywords: parametric design, algorithmic procedures, free-form architectural object, sustainable architecture

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Authors: Bouanati Sidi Mohammed, N. E. Chabane Sari, Mostefa Kara Selma

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It is well-known that Organic light emitting diodes (OLEDs) are attracting great interest in the display technology industry due to their many advantages, such as low price of manufacturing, large-area of electroluminescent display, various colors of emission included white light. Recently, there has been much progress in understanding the device physics of OLEDs and their basic operating principles. In OLEDs, Light emitting is the result of the recombination of electron and hole in light emitting layer, which are injected from cathode and anode. For improve luminescence efficiency, it is needed that hole and electron pairs exist affluently and equally and recombine swiftly in the emitting layer. The aim of this paper is to modeling polymer LED and OLED made with small molecules for studying the electrical and optical characteristics. The first simulation structures used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2’-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode usually an indium tin oxide (ITO) substrate, and a cathode, such as Al. In the second structure we replace MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq3). We choose MEH-PPV because of it's solubility in common organic solvents, in conjunction with a low operating voltage for light emission and relatively high conversion efficiency and Alq3 because it is one of the most important host materials used in OLEDs. In this simulation, the Poole-Frenkel- like mobility model and the Langevin bimolecular recombination model have been used as the transport and recombination mechanism. These models are enabled in ATLAS -SILVACO software. The influence of doping and thickness on I(V) characteristics and luminescence, are reported.

Keywords: organic light emitting diode, polymer lignt emitting diode, organic materials, hexoxy-phenylenevinylene

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Authors: Salvatore Brischetto, Domenico Cesare

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Major improvements in future aircraft and spacecraft could be those dependent on an increasing use of conventional and unconventional multilayered structures embedding composite materials, functionally graded materials, piezoelectric or piezomagnetic materials, and soft foam or honeycomb cores. Layers made of such materials can be combined in different ways to obtain structures that are able to fulfill several structural requirements. The next generation of aircraft and spacecraft will be manufactured as multilayered structures under the action of a combination of two or more physical fields. In multifield problems for multilayered structures, several physical fields (thermal, hygroscopic, electric and magnetic ones) interact each other with different levels of influence and importance. An exact 3D shell model is here proposed for these types of analyses. This model is based on a coupled system including 3D equilibrium equations, 3D Fourier heat conduction equation, 3D Fick diffusion equation and electric and magnetic divergence equations. The set of partial differential equations of second order in z is written using a mixed curvilinear orthogonal reference system valid for spherical and cylindrical shell panels, cylinders and plates. The order of partial differential equations is reduced to the first one thanks to the redoubling of the number of variables. The solution in the thickness z direction is obtained by means of the exponential matrix method and the correct imposition of interlaminar continuity conditions in terms of displacements, transverse stresses, electric and magnetic potentials, temperature, moisture content and transverse normal multifield fluxes. The investigated structures have simply supported sides in order to obtain a closed form solution in the in-plane directions. Moreover, a layerwise approach is proposed which allows a 3D correct description of multilayered anisotropic structures subjected to field loads. Several results will be proposed in tabular and graphical formto evaluate displacements, stresses and strains when mechanical loads, temperature gradients, moisture content gradients, electric potentials and magnetic potentials are applied at the external surfaces of the structures in steady-state conditions. In the case of inclusions of piezoelectric and piezomagnetic layers in the multilayered structures, so called smart structures are obtained. In this case, a free vibration analysis in open and closed circuit configurations and a static analysis for sensor and actuator applications will be proposed. The proposed results will be useful to better understand the physical and structural behaviour of multilayered advanced composite structures in the case of multifield interactions. Moreover, these analytical results could be used as reference solutions for those scientists interested in the development of 3D and 2D numerical shell/plate models based, for example, on the finite element approach or on the differential quadrature methodology. The correct impositions of boundary geometrical and load conditions, interlaminar continuity conditions and the zigzag behaviour description due to transverse anisotropy will be also discussed and verified.

Keywords: composite structures, 3D shell model, stress analysis, multifield loads, exponential matrix method, layer wise approach

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Authors: Parvin Berenjkar, Qiuyan Yuan, Richard Sparling, Stan Lozecznik

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Landfills highly contribute to anthropological global warming through CH₄ emissions. Landfills are usually capped by a conventional soil cover to control the migration of gases. Methane is consumed by CH₄-oxidizing microorganisms known as methanotrophs that naturally exist in the landfill soil cover. The growth of methanotrophs can be optimized in a bio-cover that typically consists of a gas distribution layer (GDL) to homogenize landfill gas fluxes and an overlying oxidation layer composed of suitable materials that support methanotrophic populations. Materials such as mature yard waste composts can provide an inexpensive and favourable porous support for the growth and activity of methanotrophs. In areas with seasonal cold climates, it is valuable to know if methanotrophs in a bio-cover can survive in winter until the next spring, and how deep they are active in the bio-cover to mitigate CH₄. In this study, a pilot bio-cover was constructed in a closed landfill cell in Winnipeg that has a very cold climate in Canada. The bio-cover has a surface area of 2.5 m x 3.5 m and 1.5 m of depth, filled with 50 cm of gravel as a GDL and 70 cm of biosolids compost amended with yard and leaf waste compost. The observed in situ potential of methanotrophs for CH₄ oxidation was investigated at a specific period of time from December 2016 to April 2017 as well as November 2017 to April 2018, when the transition to surface frost and thawing happens in the bio-cover. Compost samples taken from different depths of the bio-cover were incubated in the laboratory under standardized conditions; an optimal air: methane atmosphere, at 22ºC, but at in situ moisture content. Results showed that the methanotrophs were alive oxidizing methane without a lag, indicating that there was the potential for methanotrophic activity at some depths of the bio-cover.

Keywords: bio-cover, global warming, landfill, methanotrophic activity

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Authors: Zoe Wong

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The purpose of this paper is to develop a framework for internet education. This framework uses the personalized learning approach for everyone who can freely develop their qualifications & careers. The key components of the framework includes students, teachers, assessments and infrastructure. It allows remove the challenges and limitations of the current educational system and allows learners' to cope with progressing learning materials.

Keywords: internet education, personalized approach, information technology, framework

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Authors: A. Taoufyq, B. Bakiz, A. Benlhachemi, L. Patout, D. V. Chokouadeua, F. Guinneton, G. Nolibe, A. Lyoussi, J-R. Gavarri

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Currently, the photo catalytic reactions occurring under solar illumination have attracted worldwide attentions due to a tremendous set of environmental problems. Taking the sunlight into account, it is indispensable to develop highly effective visible-light-driver photo catalysts. Nano structured materials such as MxM’1-xWO6 system are widely studied due to its interesting piezoelectric, dielectric and catalytic properties. These materials can be used in photo catalysis technique for environmental applications, such as waste water treatments. The aim of this study was to investigate the photo catalytic activity of polycrystalline phases of bismuth tungstate of formula Bi2WO6. Polycrystalline samples were elaborated using a coprecipitation technique followed by a calcination process at different temperatures (300, 400, 600 and 900°C). The obtained polycrystalline phases have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Crystal cell parameters and cell volume depend on elaboration temperature. High-resolution electron microscopy images and image simulations, associated with X-ray diffraction data, allowed confirming the lattices and space groups Pca21. The photo catalytic activity of the as-prepared samples was studied by irradiating aqueous solutions of Rhodamine B, associated with Bi2WO6 additives having variable crystallite sizes. The photo catalytic activity of such bismuth tungstates increased as the crystallite sizes decreased. The high specific area of the photo catalytic particles obtained at 300°C seems to condition the degradation kinetics of RhB.

Keywords: Bismuth tungstate, crystallite sizes, electron microscopy, photocatalytic activity, X-ray diffraction.

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Authors: Dan Wang, Qing Ma, Xiaodan Wang, Tianjiao Qi

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The sound of peddling in Beijing, also called “yo-heave-ho” or “cry of one's ware”, is a unique folk culture and usually found in Beijing hutong. For the civilians in Beijing, sound of peddling is part of their childhood. And for those who love the traditional culture of Beijing, it is an old song singing the local conditions and customs of the ancient city. For example, because of his great appreciation, the British poet Osbert Stewart once put sound of peddling which he had heard in Beijing as a street orchestra performance in the article named "Beijing's sound and color".This research aims to collect and integrate the voice/photo resources and historical materials of sound concerning peddling in Beijing by digital technology in order to protect the intangible cultural heritage and pass on the city memory. With the goal in mind, the next stage is to collect and record all the materials and resources based on the historical documents study and interviews with civilians or performers. Then set up a metadata scheme (which refers to the domestic and international standards such as "Audio Data Processing Standards in the National Library", DC, VRA, and CDWA, etc.) to describe, process and organize the sound of peddling into a database. In order to fully show the traditional culture of sound of peddling in Beijing, web design and GIS technology are utilized to establish a website and plan holding offline exhibitions and events for people to simulate and learn the sound of peddling by using VR/AR technology. All resources are opened to the public and civilians can share the digital memory through not only the offline experiential activities, but also the online interaction. With all the attempts, a multi-media narrative platform has been established to multi-dimensionally record the sound of peddling in old Beijing with text, images, audio, video and so on.

Keywords: sound of peddling, GIS, metadata scheme, VR/AR technology

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Authors: Wiqar Hussain Shah

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The electrical and thermal properties of the doped Tellurium Telluride (Tl10Te6) chalcogenide nano-particles are mainly characterized by a competition between metallic (hole doped concentration) and semi-conducting state. We have studied the effects of Sn doping on the electrical and thermoelectric properties of Tl10-xSnxTe6 (1.00 ≤x≤ 2.00), nano-particles, prepared by solid state reactions in sealed silica tubes and ball milling method. Structurally, all these compounds were found to be phase pure as confirmed by the x-rays diffractometery (XRD) and energy dispersive X-ray spectroscopy (EDS) analysis. Additionally crystal structure data were used to model the data and support the findings. The particles size was calculated from the XRD data by Scherrer’s formula. The EDS was used for an elemental analysis of the sample and declares the percentage of elements present in the system. The thermo-power or Seebeck co-efficient (S) was measured for all these compounds which show that S increases with increasing temperature from 295 to 550 K. The Seebeck coefficient is positive for the whole temperature range, showing p-type semiconductor characteristics. The electrical conductivity was investigated by four probe resistivity techniques revealed that the electrical conductivity decreases with increasing temperature, and also simultaneously with increasing Sn concentration. While for Seebeck coefficient the trend is opposite which is increases with increasing temperature. These increasing behavior of Seebeck coefficient leads to high power factor which are increases with increasing temperature and Sn concentration except For Tl8Sn2Te6 because of lowest electrical conductivity but its power factor increases well with increasing temperature.

Keywords: Sn doping in Tellurium Telluride nano-materials, electron holes competition, Seebeck co-efficient, effects of Sn doping on Electrical conductivity, effects on Power factor

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Authors: Aliyu Damri

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This study analyzed the emergence of WhatsApp and how employees at the Federal Radio Corporation of Nigeria, Kaduna defined the concept base on their vast broadcasting experiences for over five decades and application of the phenomenon to the radio station. It also analyzed the nature, patterns, dimensions, features, challenges as well as the effects of WhatsApp as a social networking site with specific interest on the radio outlet. Also, the study identified how the radio organization responded to the challenges in an attempt to adapt to the new pattern of broadcasting characterized by many technological transformations. The study further explained in details such skills journalists need to function optimally using WhatsApp as well as the impacts of the WhatsApp on radio broadcasting. It used a combination of published materials, focus group discussion, in depth interviews and participant observation on the activities of the radio stations to address the research questions. The data generated provided insight to better understand the challenges posed to FRCN Kaduna as a result of WhatsApp application and how FRCN Kaduna responded to the challenges. It also provided information on the skills journalists need to function optimally in using WhatsApp application in the radio station. The interview and focus group discussion’s transcripts and the published materials were analyzed along thematic pattern related to the research questions in the study. The dominant response relied heavily on change in the radio station’s organizational and technical integration of newsrooms, the use of a multiskilled workforce, application of a flexible and user-friendly technology in all aspects of production, expansion of the station’s services in to new media such as internet and mobile phones as well as sharing of ideas across different units in the radio outfit.

Keywords: broadcasting, challenge, northern Nigeria, radio, WhatsApp application

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Authors: So-Young Lee, Myoung-Won Oh, Soon-Cheol Eom, Yeon-Won Suh

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Buildings produce more than one thirds of the total energy consumption and CO₂ emissions. Korean government agency pronounced and initiated Zero Energy Buildings policy for construction as of 2025. The net zero energy design features include passive (daylight, layout, materials, insulation, finishes, etc.) and active (renewable energy sources) elements. The Zero Energy House recently built in Nowon-gu, Korea is provided for 121 households as a public rental housing complex. However most of public rental housing did not include sustainable features which can reduce housing maintaining cost significantly including energy cost. It is necessary to implement net zero design features to the obsolete public rental housing during the remodeling procedure since it can reduce housing cost in long term. The purpose of this study is to investigate sustainable design elements implemented in Net Zero Energy House in Korea and passive and active housing design features in order to apply the sustainable features to the case public rental apartment for remodeling. Housing complex cases in this study are Nowan zero Energy house, Gangnam Bogemjari House, and public rental housings built in more than 20 years in Seoul areas. As results, energy consumption in public rental housing built in 5-years can be improved by exterior surfaces. Energy optimizing in case housing built in more than 20 years can be enhanced by renovated materials, insulation, replacement of windows, exterior finishes, lightings, gardening, water, renewable energy installation, Green IT except for sunlight and layout of buildings. Further life costing analysis is needed for energy optimizing for case housing alternatives.

Keywords: affordable housing, remodeling, sustainable design, zero-energy house

Procedia PDF Downloads 192

Authors: M. Ali Lotfollahi Yaghin, M. Reza Bagerzadeh Karimi, Ali Rahmani, V. Sadeghi Balkanlou

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Structural engineers have long been trying to develop solutions using the full potential of its composing materials. Therefore, there is no doubt that the structural solution progress is directly related to an increase in materials science knowledge. These efforts in conjunction with up-to-date modern construction techniques have led to an extensive use of composite floors in large span structures. On the other hand, the competitive trends of the world market have long been forcing structural engineers to develop minimum weight and labour cost solutions. A direct consequence of this new design trend is a considerable increase in problems related to unwanted floor vibrations. For this reason, the structural floors systems become vulnerable to excessive vibrations produced by impacts such as human rhythmic activities. The main objective of this paper is to present an analysis methodology for the evaluation of the composite floors human comfort. This procedure takes into account a more realistic loading model developed to incorporate the dynamic effects induced by human walking. The investigated structural models were based on various composite floors, with main spans varying from 5 to 10 m. based on an extensive parametric study the composite floors dynamic response, in terms of peak accelerations, was obtained and compared to the limiting values proposed by several authors and design standards. This strategy was adopted to provide a more realistic evaluation for this type of structure when subjected to vibration due to human walking.

Keywords: vibration, resonance, composite floors, people’s rhythmic movement, dynamic analysis, Abaqus software

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Authors: Girts Bumanis, Diana Bajare

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With demand for primary energy continuously growing, search for renewable and efficient energy sources has been high on agenda of our society. One of the most promising energy sources is biogas technology. Residues coming from dairy industry and milk processing could be used in biogas production; however, low efficiency and high cost impede wide application of such technology. One of the main problems is management and conversion of organic residues through the anaerobic digestion process which is characterized by acidic environment due to the low whey pH (<6) whereas additional pH control system is required. Low buffering capacity of whey is responsible for the rapid acidification in biological treatments; therefore alkali activated material is a promising solution of this problem. Alkali activated material is formed using SiO2 and Al2O3 rich materials under highly alkaline solution. After material structure forming process is completed, free alkalis remain in the structure of materials which are available for leaching and could provide buffer capacity potential. In this research porous alkali activated material was investigated. Highly porous material structure ensures gradual leaching of alkalis during time which is important in biogas digestion process. Research of mixture composition and SiO2/Na2O and SiO2/Al2O ratio was studied to test the buffer capacity potential of alkali activated material. This research has proved that by changing molar ratio of components it is possible to obtain a material with different buffer capacity, and this novel material was seen to have considerable potential for using it in processes where buffer capacity and pH control is vitally important.

Keywords: alkaline material, buffer capacity, biogas production, bioreactors

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Authors: Biruk Abate

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Evaporative cooling occurs when air with high temperature and reduced humidity passes over a wet porous surface and a higher degree of cooling process is achieved for storage of fruits and vegetables due to greater rate of evaporation. The main objective of this reviewed study is to understand the effect of evaporative surface pad thickness and geometric configuration on the saturation efficiency of evaporative cooler and to state some related factors affecting the performance of the system. From this overview, selection of pad thickness and geometrical shape with suitable characteristics of heat and mass transfer and water holding capacity of the pads was reviewed as these parameters are important for saturation efficiency of evaporative cooling. Increasing the cooling pad thickness through increasing the face velocity increases the effectiveness of wet-bulb saturation. Increasing ambient temperature, inlet air speed and ambient air humidity decreases the wet bulb effectiveness and it increases with increasing length of the pad. Increasing the ambient temperature and inlet air velocity decreases the humidity ratio, but increases with increasing ambient air humidity and lengths of the pad. Increasing the temperature-humidity index is possible with increasing ambient temperature, inlet air velocity, ambient air humidity and pad length. Generally, all materials having a higher wetted surface area per unit volume give higher efficiency. Materials with higher thickness increase the wetted surface area for better mix-up of air and water to give higher efficiency for the same shape and this in turn helps to store fruits and vegetables.

Keywords: Degree of cooling, heat and mass transfer, evaporative cooling, porous surface

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Authors: Fang Li, Jiazhao Wang, Jianmin Ma

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The practical application of Li-S batteries is hampered due to poor cycling stability caused by electrolyte-dissolved lithium polysulfides. Dual functionalities such as strong chemical adsorption stability and high conductivity are highly desired for an ideal host material for a sulfur-based cathode. Polypyrrole (PPy), as a conductive polymer, was widely studied as matrixes for sulfur cathode due to its high conductivity and strong chemical interaction with soluble polysulfides. Thus, a novel cathode structure consisting of a free-standing sulfur-polypyrrole cathode and a polypyrrole coated separator was designed for flexible Li-S batteries. The PPy materials show strong interaction with dissoluble polysulfides, which could suppress the shuttle effect and improve the cycling stability. In addition, the synthesized PPy film with a rough surface acts as a current collector, which improves the adhesion of sulfur materials and restrain the volume expansion, enhancing the structural stability during the cycling process. For further enhancing the cycling stability, a PPy coated separator was also applied, which could make polysulfides into the cathode side to alleviate the shuttle effect. Moreover, the PPy layer coated on commercial separator is much lighter than other reported interlayers. A soft-packaged flexible Li-S battery has been designed and fabricated for testing the practical application of the designed cathode and separator, which could power a device consisting of 24 light-emitting diode (LED) lights. Moreover, the soft-packaged flexible battery can still show relatively stable cycling performance after repeated bending, indicating the potential application in flexible batteries. A novel vapor phase deposition method was also applied to prepare uniform polypyrrole layer coated sulfur/graphene aerogel composite. The polypyrrole layer simultaneously acts as host and adsorbent for efficient suppression of polysulfides dissolution through strong chemical interaction. The density functional theory (DFT) calculations reveal that the polypyrrole could trap lithium polysulfides through stronger bonding energy. In addition, the deflation of sulfur/graphene hydrogel during the vapor phase deposition process enhances the contact of sulfur with matrixes, resulting in high sulfur utilization and good rate capability. As a result, the synthesized polypyrrole coated sulfur/graphene aerogel composite delivers a specific discharge capacity of 1167 mAh g⁻¹ and 409.1 mAh g⁻¹ at 0.2 C and 5 C respectively. The capacity can maintain at 698 mAh g⁻¹ at 0.5 C after 500 cycles, showing an ultra-slow decay rate of 0.03% per cycle.

Keywords: polypyrrole, strong chemical interaction, long-term stability, Li-S batteries

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Authors: Jagadeshvaran P. L., Kamlesh Panwar, Indumathi Ramakrishnan, Suryasarathi Bose

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The surge in the usage of wireless electronics and communication devices has engendered a different form of pollution, viz. the electromagnetic (EM) pollution and yet another serious issue, electromagnetic interference (EMI). There is a legitimate need to develop strategies and materials to combat this issue, otherwise leading to dreadful consequences. Functional textiles have emerged as the modern materials to help attenuate EM waves due to the numerous advantages – flexibility being the most important. In addition to this, there is an inherent advantage of multiple interfaces in coated fabrics that can engender significant attenuation. Herein we report a coating having multifunctional properties – capable of blocking both UV and EM radiation (predominantly of the microwave frequencies) with flame-retarding properties. The layer described here comprises iron titanate(FT) synthesized from its sustainable precursor – ilmenite sand and carbon nanotubes (CNT) dispersed in waterborne polyurethane. It is worth noting that FT's use as a multifunctional material is being reported for the first time. It was observed that a single layer of coated fabric shows EMI shielding effectiveness of -40 dB translating to 99.99% attenuation and similarly a UV blocking of 99.99% in the wavelength ranging from 200-400 nm. The microwave shielding properties of the fabric were demonstrated using a Bluetooth module – where the coated fabric was able to block the incoming Bluetooth signals to the module from a mobile phone. Besides, the coated fabrics exhibited phenomenal enhancement in thermal stability - a five percent increase in the limiting oxygen index (LOI) was observed upon the application of the coating. Such exceptional properties complement cotton fabrics' existing utility, thereby extending their use to specialty applications.

Keywords: multifunctional coatings, EMI shielding, UV blocking, iron titanate, CNT, waterborne polyurethane, cotton fabrics

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Authors: S. V. Kuznetsov, M. N. Mayakova, V. Yu. Proydakova, V. V. Pavlov, A. S. Nizamutdinov, O. A. Morozov, V. V. Voronov, P. P. Fedorov

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Increase in the share of electricity received by conversion of solar energy results in the reduction of the industrial impact on the environment from the use of the hydrocarbon energy sources. One way to increase said share is to improve the efficiency of solar energy conversion in silicon-based solar panels. Such efficiency increase can be achieved by transferring energy from sunlight-insensitive areas of work of silicon solar panels to the area of their photoresistivity. To achieve this goal, a transition to new luminescent materials with the high quantum yield of luminescence is necessary. Improvement in the quantum yield can be achieved by quantum cutting, which allows obtaining a quantum yield of down conversion of more than 150% due to the splitting of high-energy photons of the UV spectral range into lower-energy photons of the visible and near infrared spectral ranges. The goal of present work is to test approach of excitation through sensibilization of 4f-4f fluorescence of Yb3+ by various RE ions absorbing in UV and Vis spectral ranges. One of promising materials for quantum cutting luminophores are fluorides. In our investigation we have developed synthesis of nano- and submicron powders of calcium fluoride and strontium doped with rare-earth elements (Yb: Ce, Yb: Pr, Yb: Eu) of controlled dimensions and shape by co-precipitation from water solution technique. We have used Ca(NO3)2*4H2O, Sr(NO3)2, HF, NH4F as precursors. After initial solutions of nitrates were prepared they have been mixed with fluorine containing solution by dropwise manner. According to XRD data, the synthesis resulted in single phase samples with fluorite structure. By means of SEM measurements, we have confirmed spherical morphology and have determined sizes of particles (50-100 nm after synthesis and 150-300 nm after calcination). Temperature of calcination appeared to be 600°C. We have investigated the spectral-kinetic characteristics of above mentioned compounds. Here the diffuse reflection and laser induced fluorescence spectra of Yb3+ ions excited at around 4f-4f and 4f-5d transitions of Pr3+, Eu3+ and Ce3+ ions in the synthesized powders are reported. The investigation of down conversion luminescence capability of synthesized compounds included measurements of fluorescence decays and quantum yield of 2F5/2-2F7/2 fluorescence of Yb3+ ions as function of Yb3+ and sensitizer contents. An optimal chemical composition of CaF2-YbF3- LnF3 (Ln=Ce, Eu, Pr), SrF2-YbF3-LnF3 (Ln=Ce, Eu, Pr) micro- and nano- powders according to criteria of maximal IR fluorescence yield is proposed. We suppose that investigated materials are prospective in solar panels improvement applications. Work was supported by Russian Science Foundation grant #17-73- 20352.

Keywords: solar cell, fluorides, down-conversion luminescence, maximum quantum yield

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Authors: Mohammad Ebrahim Kianifar, Ehsan Ahmadi

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Reinforced concrete structures experience local defects such as cracks over their lifetime under various environmental loadings. Consequently, they are repaired by mortars to avoid detrimental effects such as corrosion of reinforcement, which in long-term may lead to strength loss of a member or collapse of structures. However, repaired structures may need multiple repairs due to changes in load distribution, and thus, lack of compatibility between mortar and substrate concrete. On the other hand, waste tire rubber alkali-activated (WTRAA)-based materials have very high potential to be used as repair mortars because of their ductility and flexibility, which may delay the failure of repair mortar and thus, provide sufficient compatibility. Hence, this work presents a pioneering study on suitability of WTRAA-based materials as mortars for the repair of concrete structures through an experimental program. To this end, WTRAA mortars with 15% aggregate replacement, alkali-activated (AA) mortars, and ordinary mortars are made to repair a number of concrete beams. The WTRAA mortars are composed of slag as base material, sodium hydroxide as an alkaline activator, and different gradations of waste tire rubber (fine and coarse gradations). Flexural tests are conducted on the concrete beams repaired by the ordinary, AA, and WTRAA mortars. It is found that, despite having lower compressive strength and modulus of elasticity, the WTRAA and AA mortars increase the flexural strength of the repaired beams, give compatible failures, and provide sufficient mortar-concrete interface bondings. The ordinary mortars, however, show incompatible failure modes. This study demonstrates the promising application of WTRAA mortars in the practical repairs of concrete structures.

Keywords: alkali-activated mortars, concrete repair, mortar compatibility, flexural strength, waste tire rubber

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Authors: M.S. El-Feky, Passant Youssef, Mohamed I. Serag

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nowadays, nanotechnology is the main trend of research in different areas due to the new potential of using nanometer materials sized less than 100nm. Nanomaterials are needed in cement composites to act as bridging for Nano and micro-cracks to increase tensile strength, reduce the permeability of gases and water in concrete to solve corrosion problem, react with excess Calcium Hydroxide, produce additional C-S-H, act as filler materials to densify the cement matrix and increase its mechanical properties. The present study focuses on the effectiveness of super-plasticizers and ultrasonic processing on the dispersion of Carbon Nanotube at first in water and then in cement composites in combination with Nano silica to enhance the mechanical properties of cement composites. A qualitative analysis using a compressive strength test is conducted with a view to investigate the influence of different dispersion techniques on the mechanical properties of cement composites containing Carbon Nanotube (CNT) and Nano Silica (NS) particles with different percentages. In addition, micro-structural analysis was carried out to understand the surface morphology and microstructure of cement composites with different dosages of NS addition. The investigational study results showed that the combination of NS with a low amount of CNT had a positive effect on the hydration reaction; on the other hand, the combination of CNT and a high amount of NS had a negative effect on the hydration reaction. The compressive strength can be improved by optimum combination 0.02% CNT and 1% NS with gain in strength by 72% and 35% after 7 and 28 days compared to control samples; these results were with an agreement with the morphology structure of composites using microstructure analysis.

Keywords: nano silica, dispersion, sonication, carbon nano tubes

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Authors: Srikrishna Pramanik, Sree Chithra, Saurabh Rai, Sameeksha Agrawal, Debanggana Shil, Saptarshi Mukherjee

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The understanding of interactions between organic chromophores and biologically useful luminescent noble metal nanoclusters (NCs) leading to an energy transfer process that has applications in light-harvesting materials is still in its nascent stage. This work describes a photoluminescent supramolecular assembly, made in two stages, employing an energy transfer process between silver (Ag) NCs as the donor and a host-guest system as the acceptor that can find potential applications in diverse fields. Initially, we explored the host-guest chemistry between a cationic guest, Ethidium Bromide and the anionic host Cucurbit[8]uril using spectroscopic and calorimetric techniques to decipher their interaction mechanism in modulating photophysical properties of the chromophore. Next, we synthesized a series of blue-emitting AgNCs using different templates such as protein, peptides, and cyclodextrin. The as-prepared AgNCs were characterized by various spectroscopic techniques. We have established that these AgNCs can be employed as donors in the FRET process with the above acceptor for FRET-based emission color tuning. Our in-depth studies revealed that surface ligands play a key role in modulating FRET efficiency. Overall, by employing a non-covalent strategy, we have tried to develop FRET pairs using blue-emitting NCs and a host-guest complex, which could find potential applications in constructing advanced white light-emitting, anti-counterfeiting materials, and developing biosensors.

Keywords: absorption spectroscopy, cavities, energy transfer, fluorescence, fluorescence resonance energy transfer

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Authors: Asad Hanif, Pavithra Parthasarathy, Zongjin Li

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Thermal insulating composites help to reduce the total power consumption in a building by creating a barrier between external and internal environment. Such composites can be used in the roofing tiles or wall panels for exterior surfaces. This study purposes to develop lightweight cement-based composites for thermal insulating applications. Waste materials like silica fume (an industrial by-product) and fly ash cenosphere (FAC) (hollow micro-spherical shells obtained as a waste residue from coal fired power plants) were used as partial replacement of cement and lightweight filler, respectively. Moreover, aerogel, a nano-porous material made of silica, was also used in different dosages for improved thermal insulating behavior, while poly vinyl alcohol (PVA) fibers were added for enhanced toughness. The raw materials including binders and fillers were characterized by X-Ray Diffraction (XRD), X-Ray Fluorescence spectroscopy (XRF), and Brunauer–Emmett–Teller (BET) analysis techniques in which various physical and chemical properties of the raw materials were evaluated like specific surface area, chemical composition (oxide form), and pore size distribution (if any). Ultra-lightweight cementitious composites were developed by varying the amounts of FAC and aerogel with 28-day unit weight ranging from 1551.28 kg/m³ to 1027.85 kg/m³. Excellent mechanical and thermal insulating properties of the resulting composites were obtained ranging from 53.62 MPa to 8.66 MPa compressive strength, 9.77 MPa to 3.98 MPa flexural strength, and 0.3025 W/m-K to 0.2009 W/m-K as thermal conductivity coefficient (QTM-500). The composites were also tested for peak temperature difference between outer and inner surfaces when subjected to heating (in a specially designed experimental set-up) by a 275W infrared lamp. The temperature difference up to 16.78 ^oC was achieved, which indicated outstanding properties of the developed composites to act as a thermal barrier for building envelopes. Microstructural studies were carried out by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) for characterizing the inner structure of the composite specimen. Also, the hydration products were quantified using the surface area mapping and line scale technique in EDS. The microstructural analyses indicated excellent bonding of FAC and aerogel in the cementitious system. Also, selective reactivity of FAC was ascertained from the SEM imagery where the partially consumed FAC shells were observed. All in all, the lightweight fillers, FAC, and aerogel helped to produce the lightweight composites due to their physical characteristics, while exceptional mechanical properties, owing to FAC partial reactivity, were achieved.

Keywords: aerogel, cement-based, composite, fly ash cenosphere, lightweight, sustainable development, thermal conductivity

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Authors: Joel Zapata

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Chicana/o Activism in the Southern Plains Through Time and Space, a digital history project available at PlainsMovement.com, helps reveal an understudied portion of the Chicana/o Civil Rights Movement: the way it unfolded on the Southern Plains. The project centers around an approachable interactive map and timeline along with a curated collection of materials. Therefore, the project provides a digital museum experience that has not emerged within the region’s museums. That is, this digital history project takes scholarly research to the wider public, making it is also a publicly facing history project. In this way, the project adds to both scholarly and socially significant conversations, showing that the region was home to a burgeoning wing of the Chicana/o Movement and that instances of police brutality largely spurred this wing of the social justice movement. Moreover, the curated collection of materials demonstrates that police brutality united the plains’ Mexican population across political ideology, a largely overlooked aspect within the study of Mexican American civil rights movements. Such a finding can be of use today since contemporary Latina/o social justice organizations generally ignore policing issues even amid a rise in national awareness regarding police abuse. In making history accessible to Mexican origin and Latina/o communities, these same communities may in-turn use the knowledge gained from historical research towards the betterment of their social positions—the foundational goal of Chicana/o history and the related field of Chicana/o Studies. Ultimately, this digital history project is intended to draw visitors to further explore the Chicana/o Civil Rights Movement within and beyond the plains.

Keywords: Chicana/o Movement, digital history, police brutality, newspapers, protests, student activism

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Authors: Eve-Andree Laramee

Abstract:

The aesthetics and ethics of the Nuclear Anthropocene are explored through artists responses to the impact of radioactive materials on ecological systems, global issues, energy policies and ourselves. This presentation tracks and reveals the invisible traces of the nuclear weapons complex and the nuclear energy industry, in relation to environmental justice. Radioactive pollution transgresses international borders, boundaries between land and water, contaminating ecological systems. Radioactive waste is never disposed of; it is dispositioned, placed out of sight and out of mind. These materials leave behind an invisible toxic legacy lasting millions of years. As we are learning post-Fukushima, when climate change occurs and vulnerability spectrums shift, nuclear sites and the life forms surrounding them are at increased risk. By visualizing this contamination through art installations, videos, and social-sculpture interventions, information is shared with the public, raising awareness, and activating community participation in remediation and nonproliferation efforts. The emerging Ecological Art genre proposes paradigms sustainable with the life forms and resources of our planet. It is comprised of artists, scientists, philosophers and activists devoted to these. EcoArt is distinguished by a focus on systems and interrelationships within our environment: the ecological, geographic, political, biological and cultural. This presentation will cover artworks addressing the recent Fukushima meltdowns, weapons proliferation, climate change, radioactive waste disposal and environmental justice. Possibilities for art-and-science collaborations will be discussed as projects that sharpen our ethics and politics in our behaviors and social interactions. The presentation will consist of a PowerPoint talk (paper presentation) accompanied by images and video clips.

Keywords: art, ecology, environment, anthropocene, nuclear

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Authors: Dagmara Malina, Katarzyna Bialik-Wąs, Klaudia Pluta

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The growing significance of transdermal systems, in which skin is a route for systemic drug delivery, has generated a considerable amount of data which has resulted in a deeper understanding of the mechanisms of transport across the skin in the context of the controlled and prolonged release of active substances. One of such solutions may be the use of carrier systems based on intelligent polymers with different physicochemical properties. In these systems, active substances, e.g. drugs, can be conjugated (attached), immobilized, or encapsulated in a polymer matrix that is sensitive to specific environmental conditions (e.g. pH or temperature changes). Intelligent polymers can be divided according to their sensitivity to specific environmental stimuli such as temperature, pH, light, electric, magnetic, sound, or electromagnetic fields. Materials & methods—The first stage of the presented research concerned the synthesis of pH-sensitive polymeric carriers by a radical polymerization reaction. Then, the selected active substance (hydrocortisone) was introduced into polymeric carriers. In a further stage, bio-hybrid sodium alginate/poly(vinyl alcohol) – SA/PVA-based hydrogel matrices modified with various carrier-drug systems were prepared with the chemical cross-linking method. The conducted research included the assessment of physicochemical properties of obtained materials i.e. degree of hydrogel swelling and degradation studies as a function of pH in distilled water and phosphate-buffered saline (PBS) at 37°C in time. The gel fraction represents the insoluble gel fraction as a result of inter-molecule cross-linking formation was also measured. Additionally, the chemical structure of obtained hydrogels was confirmed using FT-IR spectroscopic technique. The dynamic light scattering (DLS) technique was used for the analysis of the average particle size of polymer-carriers and carrier-drug systems. The nanocarriers morphology was observed using SEM microscopy. Results & Discussion—The analysis of the encapsulated polymeric carriers showed that it was possible to obtain the time-stable empty pH-sensitive carrier with an average size 479 nm and the encapsulated system containing hydrocortisone with an average 543 nm, which was introduced into hydrogel structure. Bio-hybrid hydrogel matrices are stable materials, and the presence of an additional component: pH-sensitive carrier – hydrocortisone system, does not reduce the degree of cross-linking of the matrix nor its swelling ability. Moreover, the results of swelling tests indicate that systems containing higher concentrations of the drug have a slightly higher sorption capacity in each of the media used. All analyzed materials show stable and statically changing swelling values in simulated body fluids - there is no sudden fluid uptake and no rapid release from the material. The analysis of FT-IR spectra confirms the chemical structure of the obtained bio-hybrid hydrogel matrices. In the case of modifications with a pH-sensitive carrier, a much more intense band can be observed in the 3200-3500 cm⁻¹ range, which most likely originates from the strong hydrogen interactions that occur between individual components.

Keywords: hydrogels, polymer nanocarriers, sodium alginate/poly(vinyl alcohol) matrices, wound dressings.

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Authors: Felipa M. Rico

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Linguistic oral competence plays a vital role in attaining effective communication. Since the English language is considered as universally used language and has a high demand skill needed in the work-place, mastery is the expected output from learners. To achieve this, learners should be given integrated differentiated tasks which help them develop and strengthen the expected skills. This study aimed to develop speaking instructional supplementary material to enhance the English linguistic competence of Grade 9 students in areas of pronunciation, intonation and stress, voice projection, diction and fluency. A descriptive analysis was utilized to analyze the speaking level of performance of the students in order to employ appropriate strategies. There were two sets of respondents: 178 Grade 9 students selected through a stratified sampling and chosen at random. The other set comprised English teachers who evaluated the usefulness of the devised teaching materials. A teacher conducted a speaking test and activities were employed to analyze the speaking needs of students. Observation and recordings were also used to evaluate the students’ performance. The findings revealed that the English pronunciation of the students was slightly unclear at times, but generally fair. There were lapses but generally they rated moderate in intonation and stress, because of other language interference. In terms of voice projection, students have erratic high volume pitch. For diction, the students’ ability to produce comprehensible language is limited, and as to fluency, the choice of vocabulary and use of structure were severely limited. Based on the students’ speaking needs analyses, the supplementary material devised was based on Nunan’s IM model, incorporating context of daily life and global work settings, considering the principle that language is best learned in the actual meaningful situation. To widen the mastery of skill, a rich learning environment, filled with a variety instructional material tends to foster faster acquisition of the requisite skills for sustained learning and development. The role of IM is to encourage information to stick in the learners’ mind, as what is seen is understood more than what is heard. Teachers say they found the IM “very useful.” This implied that English teachers could adopt the materials to improve the speaking skills of students. Further, teachers should provide varied opportunities for students to get involved in real life situations where they could take turns in asking and answering questions and share information related to the activities. This would minimize anxiety among students in the use of the English language.

Keywords: diction, fluency, intonation, instructional materials, linguistic competence

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Authors: M. Ravindiran, P. Shankar

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This paper deals with the comparison of two synthesis methods, namely, sol-gel, and combustion to prepare Fe doped ZnO nano material. Characterization results for structural, optical and magnetic properties were analyzed for the sol gel and combustion synthesis derived materials. Magnetic studies of the prepared compounds reveal that the combustion synthesis derived material has good magnetization of 50 emu/gm with a better hysteresis loop curve.

Keywords: DMS, combustion, ferromagnetic, synthesis methods

Procedia PDF Downloads 426

Authors: Tiziana Biasutti, Daniela Rigamonti, Lorenzo Palmiotti, Adelaide Nespoli, Paolo Bettini

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Aerospace industry is based on the continuous development of new technologies and solutions that allows constant improvement of the systems. Shape Memory Alloys are smart materials that can be used as dampers due to their pseudoelastic effect. The purpose of the research was to design a passive damper in Nitinol, manufactured by Selective Laser Melting, for space applications to reduce vibration between different structural parts in space structures. The powder is NiTi (50.2 at.% of Ni). The structure manufactured by additive technology allows us to eliminate the presence of joint and moving parts and to have a compact solution with high structural strength. The designed dampers had single or double cell structures with three different internal angles (30°, 45° and 60°). This particular shape has damping properties also without the pseudoelastic effect. For this reason, the geometries were reproduced in different materials, SS316L and Ti6Al4V, to test the geometry loss factor. The mechanical performances of these specimens were compared to the ones of NiTi structures, pointing out good damping properties of the designed structure and the highest performances of the NiTi pseudoelastic effect. The NiTi damper was mechanically characterized by static and dynamic tests and with DSC and microscope observations. The experimental results were verified with numerical models and with some scaled steel specimens in which optical fibers were embedded. The realized structure presented good mechanical and damping properties. It was observed that the loss factor and the dissipated energy increased with the angles of the cells.

Keywords: additive manufacturing, damper, nitinol, pseudo elastic effect, selective laser melting, shape memory alloys

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Authors: S. Al-Fadala, J. Chakkamalayath, S. Al-Bahar, A. Al-Aibani, S. Ahmed

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Globally, the use of pozzolan in blended cement is gaining great interest due to the desirable effect of pozzolan from the environmental and energy conservation standpoint and the technical benefits they provide to the performance of cement. The deterioration of concrete structures in the marine environment and extreme climates demand the use of pozzolana cement in concrete construction in the Gulf region. Also, natural sources of cement clinker materials are limited in the Gulf region, and cement industry imports the raw materials for the production of Portland cement, resulting in an increase in the greenhouse gas effect due to the CO₂ emissions generated from transportation. Even though the Gulf region has vast deposits of natural pozzolana, it is not explored properly for the production of high performance concrete. Hence, an optimum use of regionally available natural pozzolana for the production of blended cement can result in sustainable construction. This paper investigates the effect of incorporating natural pozzolan sourced from the Gulf region on the performance of blended cement in terms of heat evolution and strength development. For this purpose, a locally produced Ordinary Portland Cement (OPC) and pozzolan-incorporated blended cements containing different amounts of natural pozzolan (volcanic ash) were prepared on laboratory scale. The strength development and heat evolution were measured and quantified. Promising results of strength development were obtained for blends with the percentages of Volcanic Ash (VA) replacement varying from 10 to 30%. Results showed that the heat of hydration decreased with increase in percentage of replacement of OPC with VA, indicating increased retardation in hydration due to the addition of VA. This property could be used in mass concreting in which a reduction in heat of hydration is required to reduce cracking in concrete, especially in hot weather concreting.

Keywords: blended cement, hot weather, hydration, volcanic ash

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Authors: First A. Lahmar Lahbib, Second B. Abdeldjebar Rabiâ, Third C. Moudden B, forth D. Missoum L

Abstract:

Vibration tests are used to identify the elasticity modulus in two directions. This strategy is applied to composite materials glass / polyester. Experimental results made on a specimen in free vibration showed the efficiency of this method. Obtained results were validated by a comparison to results stemming from static tests.

Keywords: beam, characterization, composite, elasticity modulus, vibration.

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Authors: Khaled M. Khader, Mamdouh I. Elimy

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Reducing energy consumption became the major concern for all countries of the world during the recent decades. In general, power saving is currently the nominal goal of most industrial countries. It is well known that fossil fuels are the main pillar of development of world countries. Unfortunately, the increased rate of fossil fuel consumption will lead to serious problems caused by an expected depletion of fuels. Moreover, dangerous gases and vapors emission lead to severe environmental problems during fuel burning. Consequently, most engineering sectors especially the mechanical sectors are looking for improving any machine accompanied by reducing its energy consumption. Crank-Rocker planar mechanism is the most applied in mechanical systems. Besides, it is one of the most significant parts of the machines for obtaining the oscillatory motion. The transmission angle of this mechanism can be considered as an optimum value when its extreme values are equally varied around 90°. In addition, the transmission angle plays an important role in decreasing the required driving power and improving the dynamic properties of the mechanism. Hence, appropriate selection of mechanism links lengthens, which assures optimum transmission angle leads to decreasing the driving power. Moreover, mechanism's links manufactured from composite materials afford link's lightweight, which decreases the required driving torque. Furthermore, wear and corrosion problems can be treated through using composite links instead of using metal ones. This paper is dealing with improving the performance of crank-rocker mechanism using composite links due to their flexural elastic modulus values and stiffness in addition to high damping of composite materials.

Keywords: Composite Material, Crank-Rocker Mechanism, Transmission angle, Design techniques, Power Saving

Procedia PDF Downloads 304