Search results for: strength development

Authors: Ceren Ince, Berkay Zafer Erdem, Shahram Derogar, Nabi Yuzer

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Fibre cement plates, often used in construction, generally are made using quartz as an inert material, cement as a binder and cellulose as a fibre. This paper first of all investigates the mechanical properties and durability of fibre cement plates when quartz is both partly and fully replaced with diatomite. Diatomite does not only have lower density compared to quartz but also has high pozzolanic activity. The main objective of this paper is the investigation of the effects of supplementary cementing materials (SCMs) on the short and long term mechanical properties and durability characteristics of fibre cement plates prepared using diatomite. Supplementary cementing materials such as ground granulated blast furnace slug (GGBS) and fly ash (FA) are used in this study. 10, 20, 30 and 40% of GGBS and FA are used as partial replacement materials to cement. Short and long term mechanical properties such as compressive and flexural strengths as well as capillary absorption, sorptivity characteristics and mass were investigated. Consistency and setting time at each replacement levels of SCMs were also recorded. The effects of using supplementary cementing materials on the carbonation and sulphate resistance of fibre cement plates were then experimented. The results, first of all, show that the use of diatomite as a full or partial replacement to quartz resulted in a systematic decrease in total mass of the fibre cement plates. The reduction of mass was largely due to the lower density and finer particle size of diatomite compared to quartz. The use of diatomite did not only reduce the mass of these plates but also increased the compressive strength significantly as a result of its high pozzolanic activity. The replacement levels of both GGBS and FA resulted in a systematic decrease in short term compressive strength with increasing replacement levels. This was essentially expected as the total heat of hydration is much lower in GGBS and FA than that of cement. Long term results however, indicated that the compressive strength of fibre cement plates prepared using both GGBS and FA increases with time and hence the compressive strength of plates prepared using SCMs is either equivalent or more than the compressive strength of plates prepared using cement alone. Durability characteristics of fibre cement plates prepared using SCMs were enhanced significantly. Measurements of capillary absorption and sopritivty characteristics were also indicated that the plates prepared using SCMs has much lower permeability compared to plates prepared cement alone. Much higher resistance to carbonation and sulphate attach were observed with plates prepared using SCMs. The results presented in this paper show that the use of SCMs does not only support the production of more sustainable construction materials but also enhances the mechanical properties and durability characteristics of fibre cement plates.

Keywords: diatomite, fibre, strength, supplementary cementing material

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Authors: Tz-Bang Du, Cheng-Han Hsieh, Li-Ping Ju, Hung-Jie Liou

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Polyether amines synthesize by secondary hydroxyl polyether diol play an important role in epoxy hardener. The low molecular weight product is used in low viscosity and high transparent polyamine product for the logo, ground cover, especially for wind turbine blade, while the high molecular weight products are used in advanced agricultures such as a high-speed railway. High-pressure reductive amination process is required for producing these amines. In the condition of higher than 150 atm pressure and 200 degrees Celsius temperature, supercritical ammonia is used as a reactant and also a solvent. It would be a great challenge to select a catalyst support for such high-temperature alkaline circumstance. In this study, we have established a six-autoclave-type (SAT) high-pressure reactor for amination catalyst screening, which six experiment conditions with different temperature and pressure could be examined at the same time. We synthesized copper-nickel catalyst on different shaped alumina catalyst support and evaluated the catalyst activity for high-pressure reductive amination of polypropylene glycol (PPG) by SAT reactor. Ball type gamma alumina, ball type activated alumina and pellet type gamma alumina catalyst supports are evaluated in this study. Gamma alumina supports have shown better activity on PPG reductive amination than activated alumina support. In addition, the catalysts are evaluated in fixed bed reactor. The diamine product was successfully synthesized via this catalyst and the strength of the catalysts is measured. The crush strength of blank supports is about 13.5 lb for both gamma alumina and activated alumina. The strength increases to 20.3 lb after synthesized to be copper-nickel catalyst. After test in the fixed bed high-pressure reductive amination process for 100 hours, the crush strength of the used catalyst is 3.7 lb for activated alumina support, 12.0 lb for gamma alumina support. The gamma alumina is better than activated alumina to use as catalyst support in high-pressure reductive amination process.

Keywords: high pressure reductive amination, copper nickel catalyst, polyether amine, alumina

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Authors: T. Häfele, J. Kaspar, M. Vielhaber, W. Calles, J. Griebsch

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The demand for an increasing diversification of the product spectrum associated with the current huge customization desire and subsequently the decreasing unit quantities of each production lot is gaining more and more importance within a great variety of industrial branches, e.g. automotive industry. Nevertheless, traditional product development and production processes (molding, extrusion) are already reaching their limits or fail to address these trends of a flexible and digitized production in view of a product variability up to lot size one. Thus, upcoming innovative production concepts like the additive manufacturing technology basically create new opportunities with regard to extensive potentials in product development (constructive optimization) and manufacturing (economic individualization), but mostly suffer from insufficient strength regarding structural components. Therefore, this contribution presents an innovative technological and procedural conception of a hybrid additive manufacturing process (fiber-reinforced sandwich structures based on selective laser sintering technology) to overcome these current structural weaknesses, and consequently support the design of complex lightweight components.

Keywords: additive manufacturing, fiber-reinforced plastics (FRP), hybrid design, lightweight design

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Authors: Majority Oji

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The print media played a major role in the agitation for self-rule in Nigeria in the 1950s. It remains as a bastion of hope in the dark days of military rule in the country. But in the troubled waters of Nigeria’s politics, accusing fingers are pointed in the direction of the print media as problematic to the political development of the nation. Thus, Nigeria as a nation is torn between the paralyzing forces of political instability and the building powers of political stability. The press assigned a constitutional role to hold everyone, especially government officials accountable to the public, appears to be at the center of these forays. The paper takes a look at the strength and weakness of the print media as a stabilizing or destabilizing agent to the political development of Nigeria. Engaging in this study is essential and the findings fundamental to the sustainability of Nigeria’s nascent democracy. The study draws on the content analysis method. News items from major newspapers across the country were content analyzed to test the validity of the claims that the press serve as agent of political stability or political instability, and whether to accept or reject such claims. The study found that the press has published more stories that unite the people politically as found in the tested hypothesis which shows that P>0.05 implying that media publications are not significant to political instability of the nation regardless of the number of published news stories. The study recommends that all issues relating to professional and ethical standards that affect the practice of journalism in the print media should be addressed by regulatory bodies to starve of chances of information that could lead to intolerance being peddled in the print media.

Keywords: Nigeria, political instability, political stability, print media

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Authors: Pianpian Zhang, Qingping Luo

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Currently, there is a great tendency that more and more villages in China are trying to increase income by development of tourism. Especially in Zhejiang Province, 'Beautiful Rural Construction' provides an excellent opportunity for the development of tourism. In this context, development orientation, transportation routes and tourism service facilities are analyzed under the perspective of water resources protection and regional integration based on the development tourism industry of the six villages in Pujiang County, Zhejiang Province as a research object. In the program, the biggest issue is the contradiction between the ecological protection of the water and the development of economy. How to deal with the relationship between protection and development is the key to the design of this case. Furthermore, the six villages are regarded as a whole, connecting to each other by the system of five-path and the landscape along the lake. Every village has its own features, but cannot develop without one another. The article is actively exploring for suggestions and countermeasures to promote the development premised on protection and based on a regional view.

Keywords: development, integration, protection, rural tourism

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Authors: Rudra P. Pradhan

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This paper examines the Granger causal nexus between financial development and energy consumption in the group of 35 Financial Action Task Force (FATF) Countries over the period 1988-2012. The study uses two financial development indicators such as private sector credit and stock market capitalization and seven energy consumption indicators such as coal, oil, gas, electricity, hydro-electrical, nuclear and biomass. Using panel cointegration tests, the study finds that financial development and energy consumption are cointegrated, indicating the presence of a long-run relationship between the two. Using a panel vector error correction model (VECM), the study detects both bidirectional and unidirectional causality between financial development and energy consumption. The variation of this causality is due to the use of different proxies for both financial development and energy consumption. The policy implication of this study is that economic policies should recognize the differences in the financial development-energy consumption nexus in order to maintain sustainable development in the selected 35 FATF countries.

Keywords: energy consumption, financial development, FATF countries, Panel VECM

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Authors: Ajay Mandal, Jitendar Kumar Tiwari, N. Sathish, A. K. Srivastava

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A fundamental investigation is performed on the development of graphene (Gr) reinforced stainless steel 316L (SS 316L) metal matrix composite via selective laser melting (SLM) in order to improve specific strength and wear resistance property of SS 316L. Firstly, SS 316L powder and graphene were mixed in a fixed ratio using low energy planetary ball milling. The milled powder is then subjected to the SLM process to fabricate composite samples at a laser power of 320 W and exposure time of 100 µs. The prepared composite was mechanically tested (hardness and tensile test) at ambient temperature, and obtained results indicate that the properties of the composite increased significantly with the addition of 0.2 wt. % Gr. Increment of about 25% (from 194 to 242 HV) and 70% (from 502 to 850 MPa) is obtained in hardness and yield strength of composite, respectively. Raman mapping and XRD were performed to see the distribution of Gr in the matrix and its effect on the formation of carbide, respectively. Results of Raman mapping show the uniform distribution of graphene inside the matrix. Electron back scatter diffraction (EBSD) map of the prepared composite was analyzed under FESEM in order to understand the microstructure and grain orientation. Due to thermal gradient, elongated grains were observed along the building direction, and grains get finer with the addition of Gr. Most of the mechanical components are subjected to several types of wear conditions. Therefore, it is very necessary to improve the wear property of the component, and hence apart from strength and hardness, a tribological property of composite was also measured under dry sliding condition. Solid lubrication property of Gr plays an important role during the sliding process due to which the wear rate of composite reduces up to 58%. Also, the surface roughness of worn surface reduces up to 70% as measured by 3D surface profilometry. Finally, it can be concluded that SLM is an efficient method of fabricating cutting edge metal matrix nano-composite having Gr like reinforcement, which was very difficult to fabricate through conventional manufacturing techniques. Prepared composite has superior mechanical and tribological properties and can be used for a wide variety of engineering applications. However, due to the unavailability of a considerable amount of literature in a similar domain, more experimental works need to perform, such as thermal property analysis, and is a part of ongoing study.

Keywords: selective laser melting, graphene, composite, mechanical property, tribological property

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Authors: Hamed Tohidi, James W. Mahar

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One of the unknowns in the design of zoned earth dams is the percentage of sand which can be present in a clay core and still retain the necessary plasticity to prevent cracking in response to deformation. Cracks in the clay core of a dam caused by differential settlement can lead to failure of the dam. In this study, a series of Atterberg Limit tests and unconfined compression strength tests have been conducted in the ISU soil mechanics laboratory on prepared mixes of quartz sand and commercial clays (Kaolin and Smectite) to determine the relationship between sand content, plasticity and squeezing behavior. The prepared mixes have variable percentages of sand ranging between 10 and 90% by weight. Plastic limit test results in which specimens can be rolled into 1/8 in. threads without crumbling and plasticity index values which represent the range of water content over which the specimens can be remolded without cracking were used to evaluate the plasticity of the sand-clay mixtures. The test results show that the design mixes exhibit plastic behavior with sand contents up to 80% by weight. However, the plasticity of the mixes decreases with increasing sand content. For unconfined compression strength tests, the same mixtures of sand and clay (Kaolin) were made in plastic limit. The results which were concluded from the UCC tests represent the relationship between sand-clay content and chance of having squeezing behavior, also according to the results from UCC, strength of different samples and stress-strain curves can be obtained.

Keywords: clay's behaviour, plasticity, sand content, Kaolin clay

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Authors: Golda Honey Madhu, Priyanka Gupta, Anil Kumar Yadav

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The study is aimed at analyzing and understanding the design and performance properties of leno woven sacks specifically meant for holding lower weight goods under the category of lower weight capacities. The sacks are a huge part of the agro-based packaging industries which helps in keeping the perishable produce, especially fruits, fresh during transit and storage. Nowadays, Leno bags are primarily made from polypropylene, mainly due its cost-effectiveness, reusability and high strength with low weight property making it an ideal packaging solution for transportation. The design parameters are noted, and major properties like tensile strength, abrasion resistance, bursting strength, impact resistance, stiffness and bagging behaviour has been analyzed for lower weight capacities. An examination of these particular weight categories will provide valuable information on how to scale performance. Currently there are standards available for only 25 kg and 50 kg Leno sacks, and this study will further enhance the already existing testing standards and also provide tested structure-property analysis for lower weight Leno sacks. Hence the results of this research can provide significant insights for researchers, manufacturers and industry-experts with the goal of improving the quality and longevity of Leno woven sacks, thereby developing the packaging technology.

Keywords: leno bags, structure-property analysis, agro-based packaging, lower weight sacks

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Authors: Balamuralithara Balakrishnan

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This paper reports the findings of the perception and attitude towards Sustainable Development among Malaysian undergraduates. The study was carried out involving 86 engineering undergraduates from three universities in Malaysia. This research was conducted based on a survey whereby the respondents were given a questionnaire to gauge their attitude towards sustainable development. The output of the analyses showed that the respondents have an appropriate attitude towards the sustainability issues expect for economic and social equality aspects. These findings suggest that the engineering educators involved in sustainable development education need to educate undergraduate students on this important issue. This investigation serves as a cornerstone to which the current paradigm of sustainable development education can be examined for further improvement by related stakeholders.

Keywords: sustainable development, engineering education, Malaysia, attitude

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Authors: Ashraf Osman

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Effective deployable bridges that are characterized by an increased capacity to weight ratio are recently needed for post-disaster rapid mobility and military operations. In deployable bridging, replacing metals as the fabricating material with advanced composite laminates as lighter alternatives with higher strength is highly advantageous. This article presents a hierarchical optimization strategy of a composite bridge treadway considering maximum strength design and bridge weight minimization. Shape optimization of a generic deployable bridge beam cross-section is performed to achieve better stress distribution over the bridge treadway hull. The developed cross-section weight is minimized up to reserving the margins of safety of the deployable bridging code provisions. Hence, the strength of composite bridge plates is maximized through varying the plies orientation. Different loading cases are considered of a tracked vehicle patch load. The orthotropic plate properties of a composite sandwich core are used to simulate the bridge deck structural behavior. Whereas, the failure analysis is conducted using Tsai-Wu failure criterion. The naturally inspired particle swarm optimization technique is used in this study. The proposed technique efficiently reduced the weight to capacity ratio of the developed bridge beam.

Keywords: CFRP deployable bridges, disaster relief, military bridging, optimization of composites, particle swarm optimization

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Authors: Mayandi Ramanathan

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Gas turbine blades see the most aggressive thermal stress conditions within the engine, due to high Turbine Entry Temperatures in the range of 1500 to 1600°C. The blades rotate at very high rotation rates and remove a significant amount of thermal power from the gas stream. At high temperatures, the major component failure mechanism is a creep. During its service over time under high thermal loads, the blade will deform, lengthen and rupture. High strength and stiffness in the longitudinal direction up to elevated service temperatures are certainly the most needed properties of turbine blades and gas turbine components. The proposed advanced Ti alloy material needs a process that provides a strategic orientation of metallic ordering, uniformity in composition and high metallic strength. The chemical composition of the proposed Ti alloy material (25% Ta/(Al+Ta) ratio), unlike Ti-47Al-2Cr-2Nb, has less excess Al that could limit the service life of turbine blades. Properties and performance of Ti-47Al-2Cr-2Nb and Ti-6Al-4V materials will be compared with that of the proposed Ti alloy material to generalize the performance metrics of various gas turbine components. This paper will involve the summary of the effects of additive manufacturing and heat treatment process conditions on the changes in the phase composition, grain structure, lattice structure of the material, tensile strength, creep strain rate, thermal expansion coefficient and fracture toughness at different temperatures. Based on these results, additive manufacturing and heat treatment process conditions will be optimized to fabricate turbine blade with Ti-43Al matrix alloyed with an optimized amount of refractory Ta metal. Improvement in service temperature of the turbine blades and corrosion resistance dependence on the coercivity of the alloy material will be reported. A correlation of phase composition and creep strain rate will also be discussed.

Keywords: high temperature materials, aerospace, specific strength, creep strain, phase composition

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Authors: Zainab Fadhil Al Toki, Nader Ghareeb

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This study investigates how lightweight a fire resistance door will perform with under types of insulation materials. Data is initially collected from various websites, scientific books and research papers. Results show that different layers of insulation in a single door can perform better than one insulator. Furthermore, insulation materials that are lightweight, high strength and low thermal conductivity are the most preferred for fire-rated doors. Whereas heavy weight, low strength, and high thermal conductivity are least preferred for fire resistance doors. Fire-rated door specifications, theoretical test methodology, structural analysis, and comparison between five different models with diverse layers insulations are presented. Five different door models are being investigated with different insulation materials and arrangements. Model 1 contains an air gap between door layers. Model 2 includes phenolic foam, mild steel and polyurethane. Model 3 includes phenolic foam and glass wool. Model 4 includes polyurethane and glass wool. Model 5 includes only rock wool between the door layers. It is noticed that model 5 is the most efficient model, and its design is simple compared to other models. For this model, numerical calculations are performed to check its efficiency and the results are compared to data from experiments for validation. Good agreement was noticed.

Keywords: fire resistance, insulation, strength, thermal conductivity, lightweight, layers

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Authors: Ashish Kumar, T. Venkatappa Rao, Subhendu Ray Chowdhury, S. V. S. Ramana Reddy

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The main objective of this work is to determine the influence of electron beam irradiation on thermal and mechanical properties of Poly (lactic acid) (PLA)/Poly (ethylene-co-glycidyle methacrylate) (PEGM)/Hexagonal boron nitride (HBN) blend-composites. To reduce the brittleness and improve the toughness of PLA, the PLA/PEGM blend is prepared by using twin-screw Micro compounder. However, the heat deflection temperature (HDT) and other tensile properties were reduced. The HBN has been incorporated into the PLA/PEGM blend as part per hundred i.e. 5 phr and 10phr to improve the HDT. The prepared specimens of blend and blend-composites were irradiated to high energy (4.5 MeV) electron beam (E-beam) at different radiation doses to introduce the cross linking among the polymer chains and uniform dispersion of HBN particles in the PLA/PEGM/HBN blend-composites. The further improvement in the notched impact strength and HDT have been achieved in the case of PLA/PEGM/HBN blend-composites. The irradiated PLA/PEGM/HBN 5phr blend composite shows high notched impact strength and HDT as compared to other unirradiated and E-beam irradiated blend and blend-composites. The improvements in the yield strength and tensile modulus have also been noticed in the case of E-beam irradiated PLA/PEGM/HBN blend-composites as compared to unirradiated blend-composites.

Keywords: blend-composite, e-beam, HDT, PEGM, PLA

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Authors: Alma Orucevic-Alagic, Martin Höst

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Open source communities have demonstrated that complex and enterprise grade software can be produced, supported, and maintained by self-organizing groups of developers using primarily electronic form of communication. Due to the inherent nature of open source development, a specific set of open source software development practices has evolved. While there is an ongoing research on the topic of applicability of open source development practices within a company setting, still little is known about their benefits and challenges. The objective of this research is to understand if and to what degree open source development practices observed within a mature open source community are aligned with development practices within a large software and hardware company setting. For the purpose of this case study a set of open source development practices that are present in a mature open source community has been identified. Then, development practices of a large, international, hardware and software company based in Sweden were assessed and compared to the identified open source community practices. It is shown that there are many similarities between a mature open source community and a large company setting in regard to software development practices. We also identify practices that exist in open source communities and that are not standard within a company setting, but whose implementation can result in an improved software development efficiency within the company setting.

Keywords: development practices, open source software, innersource, closed open source

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Authors: Yaowaluck Ruampol, Suthakorn Wasupokin

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The research on the development of speaking using folk tales based on performance activities aimed to (1) study the development of speaking skill for early- childhood students, and (2) evaluate the development of speaking skill before and after speaking activities. Ten students of Kindergarten level 2, who have enrolled in the subject of the research for speaking development of semester 2 in 2013 were purposively selected as the research cohort. The research tools were lesson plans for speaking activities and pre-post test for speaking development that were approved as content validity and reliability (IOC=.66-1.00,α=0.967). The research found that the development of speaking skill of the research samples before using performance activities on folk tales in developing speaking skill was in the normal high level. Additionally, the results appeared that the preschoolers after applying speaking skill on performance activities also imaginatively created their speaking skill.

Keywords: speaking development, folk tales, performance activities, early-childhood students

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Authors: İsmail İnce

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The aim of this study is to determine index and mechanical properties of pyroclastic rock in a practical way by means of electrical resistivity method. For this purpose, electrical resistivity, uniaxial compressive strength, point load strength, P-wave velocity, density and porosity values of 10 different pyroclastic rocks were measured in the laboratory. A simple regression analysis was made among the index-mechanical properties of the samples compatible with electrical resistivity values. A strong exponentially relation was found between index-mechanical properties and electrical resistivity values. The electrical resistivity method can be used to assess the engineering properties of the rock from which it is difficult to obtain regular shaped samples as a non-destructive method.

Keywords: electrical resistivity, index-mechanical properties, pyroclastic rocks, regression analysis

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Authors: Lina Sinevičienė

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Arising problems of countries’ public finances, social and demographic changes motivate scientific and policy debates on public spending size, structure and efficiency in order to meet the changing needs of society and business. The concept of sustainable development poses new challenges for scientists and policy-makers in the field of public finance. This paper focuses on the investigation of the relationship between government expenditure and country’s economic development in the context of sustainable development. Empirical analysis focuses on the data of the European Union (except Croatia and Luxemburg) countries. The study covers 2003 – 2012 years, using annual cross-sectional data. Summarizing the research results, it can be stated that governments should pay more attention to the needs that ensure sustainable development in the long-run when formulating public expenditure policy, particularly in the field of environment protection.

Keywords: economic development, economic growth, government expenditure, sustainable development

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Authors: Biskri Yasmina, Laidi Babouri, Dehas Ouided, Bougherira Nadjiba, Baghloul Rahima

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Algeria is one of the countries which have extraordinary resources in vegetable fibers (Palmier, Alfa, Cotton, Sisal). Unfortunately, their valorization in the practical fields, among other things, in building materials, is still little exploited. Several works align with the fact that the use of plant fibers in mortar is an advantageous solution, given its abundance and its socio-economic and environmental impact. The idea of introducing plant fiber into the field of Civil Engineering is not new. Based on the work of several researchers in this field, we propose to study the mechanical behavior of mortar based on Sisal fibers. This work consists of the experimental characterization in the fresh state (workability) and in the hardened state (mechanical resistance to compression and traction by three-point bending) on the scale of mortar mortars based on sisal plant fibers. The main objective of this work is the study of the effect of fiber incorporation on mechanical properties (compressive strength and three-point bending strength). In this study, we varied two parameters, such as the length of the fiber (7cm, 10 cm) and the fibers percentage (0.25%, 0.5%, 0.75%, 1%, 1.25% and 1.5%). The results show that there is a slight increase in the compressive strength of the fiber-reinforced mortars compared to the reference mortar (mortar without fibers). With regard to the three-point bending tests, the fiber-reinforced mortars presented higher resistances compared to the reference mortar and this was for the different lengths and different percentages studied.

Keywords: mortar, plant fiber, experimentation, mechanical characterization, analysis

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Authors: Munir Tasdemir

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Polymer/clay composites have received great attention in the past three decades owing to their light weight coupled with significantly better mechanical and barrier properties than the corresponding neat polymer resins. An investigation was carried out on the effects of red mud powder size and ratio on the mechanical and thermal properties of polypropylene /red mud polymer composites. Red mud, in four different concentrations (0, 10, 20 and 30 wt %) and three different powder size (180, 63 and 38 micron) were added to PP to produce composites. The mechanical properties, including the elasticity modulus, tensile & yield strength, % elongation, hardness, Izod impact strength and the thermal properties including the melt flow index, heat deflection temperature and vicat softening point of the composites were investigated. The structures of the composites were investigated by scanning electron microscopy and compared to mechanical and thermal properties as a function of red mud powder content and size.

Keywords: polypropylene, powder, red mud, mechanical properties

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Authors: Nidal H. Abu-Zahra, Parisa Khoshnoud, Murtatha Jamel, Subhashini Gunashekar

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PVC foam-fly ash composites (PVC-FA) are characterized for their structural, morphological, mechanical and thermal properties. The tensile strength of the composites increased modestly with higher fly ash loading, while there was a significant increase in the elastic modulus for the same composites. On the other hand, a decrease in elongation at UTS was observed upon increasing fly ash content due to increased rigidity of the composites. Similarly, the flexural modulus increased as the fly ash loading increased, where the composites containing 25 phr fly ash showed the highest flexural strength. Thermal properties of PVC-fly ash composites were determined by Thermo Gravimetric Analysis (TGA). The micro structural properties were studied by Scanning Electron Microscopy (SEM). SEM results confirm that fly ash particles were mechanically interlocked in PVC matrix with good inter facial interaction with the matrix. Particle agglomeration and debonding was observed in samples containing higher amounts of fly ash.

Keywords: PVC foam, polyvinyl chloride, rigid PVC, fly ash composites, polymer composites

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Authors: Ehsan Mehryaar, Seyed Armin Motahari Tabari

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Coarse-grained soils are known and commonly used in a wide range of geotechnical projects, including high earth dams or embankments for their high shear strength. The most important engineering property of these soils is friction angle which represents the interlocking between soil particles and can be applied widely in designing and constructing these earth structures. Friction angle and dilative behavior of coarse-grained soils can be estimated from empirical correlations with in-situ testing and physical properties of the soil or measured directly in the laboratory performing direct shear or triaxial tests. Unfortunately, large-scale testing is difficult, challenging, and expensive and is not possible in most soil mechanic laboratories. So, it is common to remove the large particles and do the tests, which cannot be counted as an exact estimation of the parameters and behavior of the original soil. This paper describes a new methodology to simulate particles grading distribution of a well-graded gravel sample to a smaller scale sample as it can be tested in an ordinary direct shear apparatus to estimate the stress-strain behavior, friction angle, and dilative behavior of the original coarse-grained soil considering its confining pressure, and relative density using a machine learning method. A total number of 72 direct shear tests are performed in 6 different sizes, 3 different confining pressures, and 4 different relative densities. Multivariate Adaptive Regression Spline (MARS) technique was used to develop an equation in order to predict shear strength and dilative behavior based on the size distribution of coarse-grained soil particles. Also, an uncertainty analysis was performed in order to examine the reliability of the proposed equation.

Keywords: MARS, coarse-grained soil, shear strength, uncertainty analysis

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Authors: Yeo Kyeong Lee, Hae Won Min, Ji Yeon Kang, Hee Sun Kim, Yeong Soo Shin

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Fire incidents have been steadily increased over the last year according to national emergency management agency of South Korea. Even though most of the fire incidents with property damage have been occurred in building, rehabilitation has not been properly done with consideration of structure safety. Therefore, this study aims at evaluating rehabilitation effects on fire damaged normal strength concrete beams through experiments and finite element analyses. For the experiments, reinforced concrete beams were fabricated having designed concrete strength of 21 MPa. Two different cover thicknesses were used as 40 mm and 50 mm. After cured, the fabricated beams were heated for 1hour or 2hours according to ISO-834 standard time-temperature curve. Rehabilitation was done by removing the damaged part of cover thickness and filling polymeric mortar into the removed part. Both fire damaged beams and rehabilitated beams were tested with four point loading system to observe structural behaviors and the rehabilitation effect. To verify the experiment, finite element (FE) models for structural analysis were generated using commercial software ABAQUS 6.10-3. For the rehabilitated beam models, integrated temperature-structural analyses were performed in advance to obtain geometries of the fire damaged beams. In addition to the fire damaged beam models, rehabilitated part was added with material properties of polymeric mortar. Three dimensional continuum brick elements were used for both temperature and structural analyses. The same loading and boundary conditions as experiments were implemented to the rehabilitated beam models and non-linear geometrical analyses were performed. Test results showed that maximum loads of the rehabilitated beams were 8~10% higher than those of the non-rehabilitated beams and even 1~6 % higher than those of the non-fire damaged beam. Stiffness of the rehabilitated beams were also larger than that of non-rehabilitated beams but smaller than that of the non-fire damaged beams. In addition, predicted structural behaviors from the analyses also showed good rehabilitation effect and the predicted load-deflection curves were similar to the experimental results. From this study, both experiments and analytical results demonstrated good rehabilitation effect on the fire damaged normal strength concrete beams. For the further, the proposed analytical method can be used to predict structural behaviors of rehabilitated and fire damaged concrete beams accurately without suffering from time and cost consuming experimental process.

Keywords: fire, normal strength concrete, rehabilitation, reinforced concrete beam

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Authors: Paulos Meles Yihdego

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To address the environmental impact of the cement industry and road building waste, the use of chemical stabilizers in conjunction with recycled asphalt and cement components was investigated. The silica-based chemical stabilizers and their potential effects on the base layer stabilized by cement are discussed in this paper. Strength, moisture compaction interaction, and microstructural characteristics are all examined. According to the outcome, using this stabilizer has improved the mechanical properties. The inclusion of chemical stabilizers in the combination, which is responsible for the mixture's improved strength, raised the intensity of the C-S-H (Calcium Silicate Hydrate) gel, according to a microstructural study. The design was demonstrated to be durable by the little ettringites found in the later phases. The application of this stabilizer ensures a strong, eco-friendly, durable base layer.

Keywords: ettringites, microstructure analysis, durability properties, cement stabilized base

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Authors: Rafia Asghar, Abdul Hafeez

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The current research was related with natural dyes’ extraction from the powder of Neem (Azadirachta indica) bark and studied characterization of this dye under microwave radiation’s influence. Both cotton fabric and dyeing powder were exposed to microwave rays for different time intervals (2minutes, 4 minutes, 6 minutes, 8 minutes and 10 minutes) using conventional oven. Aqueous, 60% Methanol and Ethyl Acetate solubilized extracts obtained from Neem (Azadirachta indica) bark were also exposed to different time intervals (2minutes, 4 minutes, 6 minutes, 8 minutes and 10 minutes) of microwave rays exposure. Pre, meta and post mordanting with Alum (2%, 4%, 6%, 8%, and 10%) was done to improve color strength of the extracted dye. Exposure of Neem (Azadirachta indica) bark extract and cotton to microwave rays enhanced the extraction process and dyeing process by reducing extraction time, dyeing time and dyeing temperature. Microwave rays treatment had a very strong influence on color fastness and color strength properties of cotton that was dyes using Neem (Azadirachta indica) bark for 30 minutes and dyeing cotton with that Neem bark extract for 75 minutes at 30°C. Among pre, meta and post mordanting, results indicated that 5% concentration of Alum in meta mordanting exhibited maximum color strength.

Keywords: dyes, natural dyeing, ecofriendly dyes, microwave treatment

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Authors: Pim Terachinda, Witaya Wannasuphoprasit, Wasuwat Kitisomprayoonkul, Anan Srikiatkhachorn

Abstract:

Restoration of hand function and dexterity remain challenges in rehabilitation after stroke. We have developed soft exoskeleton hand robot in which using tendon-driven mechanism. Finger flexion and extension can be triggered by a foot switch and force can be adjusted manually depending on patient’s grip strength. The objective of this study is to investigate feasibility and safety of this device. The study was done in 2 stroke patients with the strength of the finger flexors/extensors grade 1/0 and 3/1 on Medical Research Council scale, respectively. Grasp and release training was performed for 30 minutes. No complication was observed. Results demonstrated that the device is safe, and therapy can be tailored to individual patient’s need. However, further study is required to determine recovery and rehabilitation outcomes after training in patients after nervous system injury.

Keywords: hand, rehabilitation, robot, stroke

Procedia PDF Downloads 291

Authors: Houssem Ayari

Abstract:

Sheet molding compounds (SMC) are high strength thermoset moulding materials reinforced with glass treated with thermocompression. SMC composites combine fibreglass resins and polyester/phenolic/vinyl and unsaturated acrylic to produce a high strength moulding compound. These materials are usually formulated to meet the performance requirements of the moulding part. In addition, the vinyl ester resins used in the new advanced SMC systems (A-SMC) have many desirable features, including mechanical properties comparable to epoxy, excellent chemical resistance and tensile resistance, and cost competitiveness. In this paper, a proposed model is used to take into account the Young modulus evolutions of advanced SMC systems (A-SMC) composite under fatigue tests. The proposed model and the used approach are in good agreement with the experimental results.

Keywords: composites SFRC, damage, fatigue, Mori-Tanaka

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Authors: Soner Guler, Eylem Guzel, Mustafa Gülen

Abstract:

Recently, concrete-filled steel tube columns are highly popular in high-rise buildings. The main aim of this study is to evaluate the axial load capacities of circular high strength concrete-filled steel tube columns according to Eurocode 4 (EC4) and American Concrete Institute (ACI) design codes. The axial load capacities of fifteen concrete-filled steel tubes stub columns were compared with design codes EU4 and ACI. The results showed that the EC4 overestimate the axial load capacity for all the specimens.

Keywords: concrete-filled steel tube column, axial load capacity, Eurocode 4, ACI design codes

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Authors: Fadeke Olu-Owolabi, Fayomi Oluyemi

Abstract:

The political and societal orders face the awesome task of overcoming the difficulties which lead to growing tensions and conflicts in Africa. At the core of analysis is the question, how stable and adaptable are established democracies, new democracies, and political and societal actors? The idea of development-democracy as implying the strong linkage between economic development and political democracy appropriately describes the distinguishing characteristic of this new demand for democracy in Africa. The theoretical study examines the political and philosophical foundation of the idea of development-democracy and the arguments presented to support the need for its adoption in Africa today. This paper critically examines the polemic between the advocates of developmental dictatorship and developmental-democracy and argues for the adoption of the latter in Africa. The paper sets out to expose for the political and philosophical foundation of developmental democracy maintaining that only democracy can facilitate development. This argument is supported further by the claim that both democracy and development are two sides of the same coin in the sense that the two are both ethical concepts. The paper also maintained that the only way by which democracy is worthwhile is when it is developmental. Finally, the paper affirms that since the two concepts of democracy and development are like the Siamese twins then the way out of Africa’s present crisis of development is to wholeheartedly embrace democracy. It posits that when genuine democracy is adopted, genuine and sustainable development can then be attained.

Keywords: democracy, development, polemic, principles

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Authors: Shan Faiz, Arfat Anis, Saeed M. Al-Zarani

Abstract:

High density polyethylene (HDPE) and poly benzimidazole fiber (PBI) composites were prepared by melt blending in a twin screw extruder (TSE). The thermo-mechanical properties of PBI fiber reinforced HDPE composite samples (1%, 4% and 8% fiber content) of fiber lengths 3 mm and 6 mm were investigated using differential scanning calorimeter (DSC), universal testing machine (UTM), rheometer and scanning electron microscopy (SEM). The effect of fiber content and fiber lengths on the thermo-mechanical properties of the HDPE-PBI composites was studied. The DSC analysis showed decrease in crystallinity of HDPE-PBI composites with the increase of fiber loading. Maximum decrease observed was 12% at 8% fiber length. The thermal stability was found to increase with the addition of fiber. T50% was notably increased to 40oC for both grades of HDPE using 8% of fiber content. The mechanical properties were not much affected by the increase in fiber content. The optimum value of tensile strength was achieved using 4% fiber content and slight increase of 9% in tensile strength was observed. No noticeable change was observed in flexural strength. In rheology study, the complex viscosities of HDPE-PBI composites were higher than the HDPE matrix and substantially increased with even minimum increase of PBI fiber loading i.e. 1%. We found that the addition of the PBI fiber resulted in a modest improvement in the thermal stability and mechanical properties of the prepared composites.

Keywords: PBI fiber, high density polyethylene, composites, melt blending

Procedia PDF Downloads 368