Search results for: quality properties

Authors: Dong Zhang, Kang Hai Tan, Aravind Dasari

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Increasing concern on environmental sustainability and waste management has driven the construction and building sector towards renewable materials. In this work, we have explored the usage of natural fibers as an alternative to synthetic fibers like polypropylene (PP) in ultra-high performance concrete (UHPC). PP fibers are incorporated into concrete to resist explosive thermal spalling of UHPC during a fire exposure scenario. Experimental studies on the effect of natural fiber on the mechanical properties and spalling resistance of UHCP were conducted. The residual mechanical properties of UHPC with natural fibers were tested after heating to different temperatures. Spalling behavior of UHPC with natural fibers is also assessed by heating the samples according to ISO 834 fire curve. A range of analytical, physical and microscopic characterization techniques was also used on the concrete samples before and after being subjected to elevated temperature to investigate the phase and microstructural change of the sample. The findings show that natural fibers are able to improve fire resistance of UHPC. Adding natural fibers can prevent UHPC from spalling at high temperature. This study provides an alternative, which is at low cost and environmentally friendly, to prevent spalling of UHPC.

Keywords: high temperature, natural fiber, spalling, ultra-high performance concrete

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Authors: Sohaib Z. Khan, Farrukh Mustahsan, Essam R. I. Mahmoud, S. H. Masood

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Materials or structures that contract laterally on the application of a compressive load and vice versa are said to be Auxetic materials which exhibit Negative Poisson’s Ratio (NPR). Numerous auxetic structures are proposed in the literature. One of the most studied periodic auxetic structure is the re-entrant honeycomb model. In this paper, a modified re-entrant model is proposed to enhance the auxetic behavior. The paper aimed to investigate the elastic behaviour of the proposed model to improve Young’s modulus and NPR by evaluating the analytical model. Finite Element Analysis (FEA) is also conducted to support the analytical results. A significant increment in Young’s modulus and NPR can be achieved in one of the two orthogonal directions of the loading at the cost of compromising these values in other direction. The proposed modification resulted in lower relative densities when compared to the existing re-entrant honeycomb structure. A trade-off in the elastic properties in one direction at low relative density makes the proposed model suitable for uni-direction applications where higher stiffness and NPR is required, and strength to weight ratio is important.

Keywords: 2D model, auxetic materials, re-entrant honeycomb, negative Poisson's ratio

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Authors: Zhong-Dan Tu, Wang-Xi Fan, Yi-Chen Huang, Jen-Taut Yeh

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Novel ultrahigh molecular weight polyethylene (UHMWPE)/cellulose nanofiber (CNF) (F100CNFy) and UHMWPE/modified cellulose nanofiber (MCNF) (F100MCNFxy) as-prepared nanocomposite fibers were prepared by spinning F100CNFy and F100MCNFxy gel solutions, respectively. Cellulose nanofibers were successfully prepared by proper acid treatment of cotton fibers using sulfuric acid solutions. The best prepared CNF is with specific surface areas around 120 m2/g and a nanofiber diameter of 20 nm. Modified cellulose nanofiber was prepared by grafting maleic anhydride grafted polyethylene (PE-g-MAH) onto cellulose nanofibers. The achievable draw ratio (Dra) values of each F100MCNFxy as-prepared fiber series specimens approached a maximal value as their MCNF contents reached the optimal value at 0.05 phr. In which, the maximum Dra value obtained for F100MCNFx0.05 as-prepared fiber specimen prepared at the optimal MCNF content reached another maximum value as the weight ratio of PE-g-MAH to CNF approach an optimal value at 6. Similar to those found for the achievable drawing properties of the as-prepared fibers, the orientation factor, tensile strength (σ f) and initial modulus (E) values of drawn F100MCNF6y fiber series specimens with a fixed draw ratio reach a maximal value as their MCNF contents approach the optimal value, wherein the σ f and E values of the drawn F100MCNFxy fiber specimens are significantly higher than those of the drawn F100 fiber specimens and corresponding drawn F100CNFy fiber specimens prepared at the same draw ratios and CNF contents but without modification. To understand the interesting ultradrawing, thermal, orientation and tensile properties of F100CNFy and F100MCNFxy fiber specimens, Fourier transform infra-red, specific surface areas, and transmission electron microcopic analyses of the original and modified CNF nanofillers were performed in this study.

Keywords: ultradrawing, cellulose nanofibers, ultrahigh molecular weight polyethylene, nanocomposite fibers

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Authors: Kajori Banerjee, Laxmi Kant Dwivedi

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“Health transition” is defined to be “a process through which high levels of mortality, morbidity and disability are reduced to low levels by influencing cultural, social and behavioural factors”. Life expectancy in India has been on the rise and parallel the burden of disease and disability has also risen noticeably. Borrowing data from Indian Census (2001, 2011), this study identifies the gender-wise burden of disability by calculating disability free life expectancy (DFLE) and life lived with disability (LWD). Sullivan’s method of calculating DFLE using proportion of disabled is used for this purpose. The change in person years lived with disability in the decade 2001-11 is further decomposed using Arriaga’s method into mortality and disability effects (ME and DE) to check the magnitude and direction of contribution of mortality and disability. Nationally, along with DFLE, LWD has amplified too. Despite having the highest life expectancy and DFLE, LWD in Kerala, was highest for both sexes in 2001. But in 2011, the LWD was highest among the males of Orissa and females of Rajasthan. For the overall population, DE is positive for the prime working age groups of 20-40years indicating that there has been an increase in the disability proportion holding mortality constant for 2001-2011. Females exhibit higher positive DE implying greater loss of healthy years due to disability than males. The findings call for an immediate attention to the causes of rising disability burden among the working population, especially females, as this might heavily effect the availability of quality labour force and its relative economic output in the Indian labour market. This also hints at the degrading quality of the elongated life and needs to be given the required attention to enhance the quality of life lead in the Nation.

Keywords: disability-free life expectancy, disability effect, life expectancy, mortality effect

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Authors: Haibo Zhao, Thomas Andre, Katherine Avery, Alper Kiziltas, Deborah Mielewski

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Silica aerogels were fabricated through a modified rapid supercritical extraction (RSCE) process. The silica aerogels were made using a tetramethyl orthosilicate precursor and then placed in a hot press and brought to the supercritical point of the solvent, ethanol. In order to control the pressure release without a pressure controller, a needle valve was used. The resulting aerogels were then characterized for their physical and chemical properties and compared to silica aerogels created using similar methods. The aerogels fabricated using this modified RSCE method were found to have similar properties to those in other papers using the unmodified RSCE method. Silica aerogel infused glass blanket composite, graphene reinforced silica aerogel composite were also successfully fabricated by this new method. The modified RSCE process and system is a prototype for better gas outflow control with a lower cost of equipment setup. Potentially, this process could be evolved to a continuous low-cost high-volume production process to meet automotive requirements.

Keywords: aerogel, automotive, rapid supercritical extraction process, low cost production

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Authors: Mario M. J. Musonda

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Access to health care is a human right, which includes having timely access to affordable and quality essential medicines at the right place and in sufficient quantity. However, inefficient public sector supply chain management contributes to constant shortages of essential medicines at health facilities. Literature review involved a desktop study of published research studies and reports on risk management, supply chain management of essential medicines and their integration to increase the efficiency of the latter. The research was conducted on a sample population of offices under Ministry of Health Headquarters, Lusaka Provincial and District Offices, selected health facilities in Lusaka, Medical Stores Limited, Zambia Medicines Regulatory Authority and Cooperating Partners. Individuals involved in study were selected judgmentally by their functions under selection and quantification, regulation, procurement, storage, distribution, quality assurance, and dispensing of essential medicines. Structured interviews and discussions were held with selected experts and self-administered questionnaires were distributed. Collected and analysed data of 35 returned and usable questionnaires from the 50 distributed. The highest prioritised risks were; inadequate and inconsistent fund disbursements, weak information management systems, weak quality management systems and insufficient resources (HR and infrastructure) among others. The results for this research can be used to increase the efficiency of the public sector supply chain of essential medicines and other pharmaceuticals. The results of the study showed that there is need to implement effective risk management systems by participating institutions and organisations to increase the efficiency of the entire supply chain in order to avoid and/or reduce shortages of essential medicines at health facilities.

Keywords: essential medicine, risk assessment, risk management, supply chain, supply chain risk management

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Authors: Seyed Mohammad Asgharzadeh, Moein Biglari

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Asphalt overlay is the most commonly used technique of pavement rehabilitation. However, the reflective cracks which occur on the overlay surface after a short period of time are the most important distresses threatening the durability of new overlays. Stress Absorbing Membrane Interlayers (SAMIs) are used to postpone the reflective cracking in the overlays. Sand asphalt mixtures, in unmodified or crumb rubber modified (CRM) conditions, can be used as an SAMI material. In this research, the performance properties of different SAMI applications were evaluated in the laboratory using an Indirect Tensile (IDT) fracture energy. The IDT fracture energy of sand asphalt samples was also evaluated and then compared to that of the regular dense graded asphalt used as an overlay. Texas boiling water and modified Lottman tests were also conducted to evaluate the moisture susceptibility of sand asphalt mixtures. The test results showed that sand asphalt mixtures can stand higher levels of energy before cracking, and this is even more pronounced for the CRM sand mix. Sand asphalt mixture using CRM binder was also shown to be more resistance to moisture induced distresses.

Keywords: SAMI, sand asphalt, crumb rubber, indirect tensile test

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Authors: Jie Ren, Siyao Guo

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Laden with phosphates at a low pH value, sewage wastewater aggressive environments constitute a great threat to concrete-based pipes which is made of alkaline cementitious materials such as ordinary Portland cement (OPC). As a promising alternative for OPC-based binders, alkali-activated slag/fly ash (AASF) cementitious binders are generally believed to gain similar or better properties compared to OPC-based counterparts, especially durability. However, there is limited research on the performance of AASF binders in phosphoric acid solution. Moreover, the behavior of AASF binders composited with epoxy resin/TiO₂ when exposed to acidic media has been rarely explored. In this study, the performance of AASF paste with the precursor slag:fly ash (50:50 in mass ratio) enhanced with epoxy resin/TiO₂ composite in phosphoric acid solution (pH = 3.0-4.0) was investigated. The exposure towards acid attack lasted for 90 days. The same AASF mixture without resin/TiO₂ composite was used as a reference. The compressive strength and porous-related properties prior to acidic immersion were tested. The mass variations and degradation depth of the two mixtures of binders were also monitored which is based on phenolphthalein-videomicroscope method. The results show that the binder with epoxy resin/TiO₂ addition gained a higher compressive strength and lower water absorption than the reference. In addition, it also displayed a higher resistance towards acid attack indicated by a less mass loss and less degradation depth compared to the control sample. This improvement can be attributed to a dense microstructure evidenced by the higher compressive strength and related porous structures. It can be concluded that the microstructure can be improved by adding epoxy resin/TiO₂ composite in order to enhance the resistance of AASF binder towards acid attacks.

Keywords: alkali-activated paste, epoxy resin/TiO₂, composites, mechanical properties, phosphoric acid

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Authors: Aneesh Joshi, Sagil James

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Cold Spray (CS) process is deposition of solid particles over a substrate above a certain critical impact velocity. Unlike thermal spray processes, CS process does not melt the particles thus retaining their original physical and chemical properties. These characteristics make CS process ideal for various engineering applications involving metals, polymers, ceramics and composites. The bonding mechanism involved in CS process is extremely complex considering the dynamic nature of the process. Though CS process offers great promise for several engineering applications, the realization of its full potential is limited by the lack of understanding of the complex mechanisms involved in this process and the effect of critical process parameters on the deposition efficiency. The goal of this research is to understand the complex nanoscale mechanisms involved in CS process. The study uses Molecular Dynamics (MD) simulation technique to understand the material deposition phenomenon during the CS process. Impact of a single crystalline copper nanoparticle on copper substrate is modelled under varying process conditions. The quantitative results of the impacts at different velocities, impact angle and size of the particles are evaluated using flattening ratio, von Mises stress distribution and local shear strain. The study finds that the flattening ratio and hence the quality of deposition was highest for an impact velocity of 700 m/s, particle size of 20 Å and an impact angle of 90°. The stress and strain analysis revealed regions of shear instabilities in the periphery of impact and also revealed plastic deformation of the particles after the impact. The results of this study can be used to augment our existing knowledge in the field of CS processes.

Keywords: cold spray process, molecular dynamics simulation, nanoparticles, particle impact

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Authors: N. Belhadj, M. Hadj Youcef, T. Benabdallah, Belbachir Ibtissem, N. Boceiri

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This work deals with the synthesis, the structural elucidation and the exploration the extracting properties of a series of ortho-hydroxy Schiff base in sulfate medium. After the synthesis and characterization of their structures, the study of their behavior in solution was carried out by pH-metric titration in different media homogeneous and heterogeneous solution. This allowed to explore and to quantify in each of these media, some of their properties in solution such as, their acid-base behavior (determination and comparison of pKa), their distribution powers (determination and comparison of logKd), and their thermodynamic constants (determining ∆H°, ΔS° and ∆G°moy) by optimizing both the temperature and ionic strength. Study of the extraction of nickel (II) and cobalt(II) separately was undertaken in the aqueous-organic system, chloroform-water. Different extraction parameters have been thus optimized such, the pH, the concentration of extractant and the ionic strength, and the extraction constants established in each case. The extracted metal complexes have been isolated and their spatial configurations elucidated. The selective extraction of the couple cobalt (II)/nickel (II) was finally performed by our series of Schiff base in the chloroforme/water.

Keywords: selective extraction, Schiff base, distribution, cobalt(II), nickel(II)

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Authors: Feng Zhang, Li Chen, Desong Kong, Xiaoping Zhang, Xiaojing Zhu, Yin Lu, Shizhong Zheng

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Sinusoidal pathological angiogenesis is a novel therapeutic target for liver fibrosis. We demonstrated that curcumin ameliorated fibrotic injury and sinusoidal angiogenesis in rat liver with fibrosis caused by carbon tetrachloride. Curcumin reduced the expression of angiogenic markers in fibrotic liver. Experiments in vitro showed that the viability and vascularization of rat liver sinusoidal endothelial cells (LSECs) were not impaired by curcumin. Further investigations showed that curcumin inhibited VEGF expression in hepatic stellate cells (HSCs) by disrupting PDGF-βR/ERK and mTOR pathways. HSC motility and vascularization were also suppressed by curcumin via blocking PDGF-βR/FAK/RhoA cascade. Gain- or loss-of-function analyses revealed that activation of PPARγ was required for curcumin to inhibit angiogenic properties of HSCs. We concluded that curcumin attenuated sinusoidal angiogenesis in liver fibrosis possibly by targeting HSCs via a PPARγ activation-dependent mechanism. PPARγ could be a target molecule for reducing pathological angiogenesis during liver fibrosis.

Keywords: angiogenesis, hepatic stellate cell, curcumin, peroxisome proliferator-activated receptor-γ

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Authors: Nissa Phloimontri

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This research explores the current physical conditions of motorcycle taxi stands located near the BTS stations in the central business district (CBD) and the comfort conditions of motorcycle taxi drivers. The criteria set up for physical stand survey and assessment are the integration of multimodal access design guidelines. After the survey, stands that share similar characteristics are classified into a series of typologies. Based on the environmental comfort model, questionnaires and in-depth interviews are conducted to evaluate the comfort levels of drivers including physical, functional, and psychological comfort. The results indicate that there are a number of motorcycle taxi stands that are not up to standard and are not conducive to the work-related activities of drivers. The study concludes by recommending public policy for integrated paratransit stops that support the multimodal transportation and seamless mobility concepts within the specific context of Bangkok as well as promote the quality of work life of motorcycle taxi drivers.

Keywords: motorcycle taxi, paratransit stops, environmental comfort, quality of work life

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Authors: Piyush Hajela

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The significance of public spaces is on a rise in Indian cities as a strong interaction space across cultures and community. It is a pertinent gathering space for people across age and gender, where the face keeps changing with time. A public space is directly related to the social dimension, people, comfort, safety, and security, that, it proposes to provide, as inherent qualities. The presence of these and other dimensions of space, together with related equitable environments, impart certain quality to a public space. The higher the optimum contents of these dimensions, the better the quality of public space. Public is represented by PEOPLE through society and community, and space is created by dimensions. Society contains children, women and the elderly, community is composed of social, and religious groups. These behave differently in a different setting and call for varied quality of spaces, created and generated. Public spaces are spread across a city and have more or less established their existence and prominence in a social set up. While few of them are created others are discovered by the people themselves in their constant search for desirable interactive public spaces. These are the most sought after gathering spaces that have the quality of promoting social interaction, providing free accessibility, provide desirable scale etc. The emergence of public space dates back to the times when people started forming communities, display cultures and traditions publicly, gathered for religious observations and celebrations, and address the society. Traditional cities and societies in India were feudal and orthodox in their nature and yet had public spaces. When the gathering of people at one point in a city became more frequent the point became more accessible and occupied. Baras (large courts, Chowks (public squares) and Maidans (large grounds) became well-known gathering spaces in the towns and cities. As the population grew such points grew in number, each becoming a public space in itself and with a different and definite social character. The author aims at studying the various dimensions of public spaces with which a public space has power to hold people for a significant period of time. The human senses here are note referred to as taste, sight, hearing, touch or smell, but how human senses collectively respond to when stationed in a given public space. The collectives may reflect in dimensions like comfort, safety, environment, freedom etc. Various levels of similar other responses would be studied through interviews, observations and other scientific methods for both qualitative and quantitative analysis.

Keywords: society, interaction, people, accessibility, comfort, enclosure

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Authors: Sheng-Long Lee, Tse-An Pan

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In this study, an optical microscope (OM), electron microscope (SEM), electrical conductivity meter (% IACS), hardness test, and wear test were subjected to analyze the microstructure of the wrought Al-11Si-3Cu-0.5Mg alloys. The effect of eutectic silicon morphology and alloy hardness on wear properties was investigated. The results showed that in the cast state, the morphology of eutectic silicon modified by strontium and antimony is lamellar and finer fibrous structure. After homogenization, the eutectic Si modified by Sr coarsened, and the eutectic Si modified by Sb refined due to fragmentation. The addition of modifiers, hot rolling, and solution aging treatment can control eutectic silicon morphology and hardness. The finer eutectic silicon and higher hardness have better wear resistance. During the wearing process, a protective oxide layer, also known as Mechanical Mixed Layer (MML), is formed on the surface of the alloy. The MML has higher stability and cracking resistance in Sr-modified alloys than in Sb-modified alloys. The study found that the wearing behavior of Al-11Si-3Cu-0.5Mg alloy was enhanced by the combination of adding Sr with lower solution time and T6 peak aging.

Keywords: Al-Si-Cu-Mg alloy, eutectic silicon, heat treatment, wear property

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Authors: Chu Chen, Giorgio Gotti, Tony Kang, Michael Wolfe

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This study examines the role of codes of ethics in reducing the extent to which managers’ act opportunistically in reporting earnings. Corporate codes of ethics, by clarifying the boundaries of ethical corporate behaviors and making relevant social norms more salient, have the potential to deter managers from engaging in opportunistic financial reporting practices. In a sample of international companies, we find that the quality of corporate codes of ethics is associated with higher earnings quality, i.e., lower discretionary accruals. Our results are confirmed for a subsample of firms more likely to be engaging in opportunistic reporting behavior, i.e., firms that just meet or beat analysts’ forecasts. Further, codes of ethics play a greater role in reducing earnings management for firms in countries with weaker investor protection mechanisms. Our results suggest that corporate codes of ethics can be a viable alternative to country-level investor protection mechanisms in curbing aggressive reporting behaviors.

Keywords: corporate ethics policy, code of ethics, business ethics, earnings discretion, accruals

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Authors: Azad Hussain, Andrew Cobley

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The demand for lightweight parts with high mechanical strength(s) and integrity, in sectors such as the aerospace and automotive is ever increasing, motivated by the need for weight reduction in order to increase fuel efficiency with components usually manufactured using a high grade primary metal or alloy. For components manufactured using the squeeze casting process, this alloy is usually A356 aluminium (Al), it is one of the most versatile Al alloys; and is used extensively in castings for demanding environments. The A356 castings provide good strength to weight ratio making it an attractive option for components where strength has to be maintained, with the added advantage of weight reduction. In addition, the versatility in castabilitiy, weldability and corrosion resistance are other attributes that provide for the A356 cast alloy to be used in a large array of industrial applications. Conversely, it is rare to use remelted Al in these cases, due the nature of the applications of components in demanding environments, were material properties must be defined to meet certain specifications for example a known strength or ductility. However the use of remelted Al, especially primary grade Al such as A356, would offer significant cost and energy savings for manufacturers using primary alloys, provided that remelted aluminium can offer similar benefits in terms of material microstructure and mechanical properties. This study presents the results of the material microstructure and properties of 100% primary A356 Al and 100% remelt Al cast, manufactured via the direct squeeze cast method. The microstructures of the castings made from remelted A356 Al were then compared with the microstructures of primary A356 Al. The outcome of using remelting Al on the microstructure was examined via different analytical techniques, optical microscopy of polished and etched surfaces, and scanning electron microscopy. Microstructural analysis of the 100% remelted Al when compared with primary Al show similar α-Al phase, primary Al dendrites, particles and eutectic constituents. Mechanical testing of cast samples will elucidate further information as to the suitability of utilising 100% remelt for casting.

Keywords: A356, microstructure, remelt, squeeze casting

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Authors: S. Vanker, A. Aaver, A. Roio, L. Nuut

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To be sure about the effective and less effective/ineffective approaches to course instruction, we hold the opinion that the faculty members need regular feedback from their students in order to be aware of how well or unwell their teaching styles have worked when instructing the courses. It can be confirmed without a slightest hesitation that undergraduate students’ motivated-ness can be sustained when continually improving the quality of teaching and properly sequencing the academic courses both, in the curricula and timetables. At Estonian Aviation Academy, four different forms of feedback are used: Lecture monitoring, questionnaires for all students, study information system subject monitoring and direct feedback received by the lecturer. Questionnaires for all students are arranged once during a study year and separately for the first year and senior students. The results are discussed in academic departments together with student representatives, analyzed with the teaching staff and, if needed, improvements are suggested. In addition, a monitoring system is planned where a lecturer acts in both roles – as an observer and as the lecturer. This will foster better exchange of experience and through this help to make the whole study process more interesting.

Keywords: learner motivation, feedback, student support, undergraduate education

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Authors: Muhammad Zubair, Aman Ullah, Jianping Wu

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During the last decades, petroleum derived synthetic polymers like polyethylene terephthalate, polyvinylchloride, polyethylene, polypropylene and polystyrene has extensively been used in the field of food packaging and mostly are non-degradable. Biopolymers are a good fit for single-use or short-lived products such as food packaging. Spent hens, a poultry by-product which is of little economic value and their disposal are environmentally harmful. Through current study, we have explored the possibility to transform proteins from spent fowl into green food packaging material. Proteins from spent fowl were extracted within 1 hour using pH shift method with recovery of about 74%. Different plasticizers were tried like glycerol, sorbitol, glutaraldehyde, 1,2 ethylene glycol and 1,2 butanediol. Glycerol was the best plasticizer among all these plasticizers. A naturally occurring and non-toxic cross-linking agent, chitosan, was used to form the chitosan/glycerol/protein blend by casting and compression molding techniques. The mechanical properties were characterized using tensile strength analyzer. The nano-reinforcements with homogeneous dispersion of nanoparticles lead to improved physical properties suggesting that these materials have great potential for food packaging applications.

Keywords: differential scanning calorimetry, dynamic mechanical analysis, scanning electron microscopy, spent hen

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Authors: Turin Datta, Kisor K. Sahu

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Structural materials used in today’s oil and gas exploration and drilling of both onshore and offshore oil and gas wells must possess superior tensile properties, excellent resistance to corrosive degradation that includes general, localized (pitting and crevice) and environment assisted cracking such as stress corrosion cracking and hydrogen embrittlement. The High Pressure and High Temperature (HPHT) wells are typically operated at temperature and pressure that can exceed 300-3500F and 10,000psi (69MPa) respectively which necessitates the use of exotic materials in these exotic sources of natural resources. This research investigation is focussed on the evaluation of tensile properties and corrosion behavior of AISI 4140 High-Strength Low Alloy Steel (HSLA) possessing tempered martensitic microstructure and Duplex 2205 Stainless Steel (DSS) having austenitic and ferritic phase. The selection of this two alloys are primarily based on economic considerations as 4140 HSLA is cheaper when compared to DSS 2205. Due to the harsh aggressive chemical species encountered in deep oil and gas wells like chloride ions (Cl-), carbon dioxide (CO2), hydrogen sulphide (H2S) along with other mineral organic acids, DSS 2205, having a dual-phase microstructure can mitigate the degradation resulting from the presence of both chloride ions (Cl-) and hydrogen simultaneously. Tensile properties evaluation indicates a ductile failure of DSS 2205 whereas 4140 HSLA exhibit quasi-cleavage fracture due to the phenomenon of ‘tempered martensitic embrittlement’. From the potentiodynamic polarization testing, it is observed that DSS 2205 has higher corrosion resistance than 4140 HSLA; the former exhibits passivity signifying resistance to localized corrosion while the latter exhibits active dissolution in all the environmental parameters space that was tested. From the Scanning Electron Microscopy (SEM) evaluation, it is understood that stable pits appear in DSS 2205 only when the temperature exceeds the critical pitting temperature (CPT). SEM observation of the corroded 4140 HSLA specimen tested in aqueous 3.5 wt.% NaCl solution reveals intergranular cracking which appears due to the adsorption and diffusion of hydrogen during polarization, thus, causing hydrogen-induced cracking/hydrogen embrittlement. General corrosion testing of DSS 2205 in acidic brine (pH~3.0) solution at ambient temperature using coupons indicate no weight loss even after three months whereas the corrosion rate of AISI 4140 HSLA is significantly higher after one month of testing.

Keywords: DSS 2205, polarization, pitting, SEM

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Authors: Adya Uluwita, Fernando Pedrosa, Georgi Georgiev, Christian Bernard, Raoul Masterson

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CERN is an international organisation founded by 23 countries that provide the particle physics community with excellence in particle accelerators and other related facilities. Founded in 1954, CERN has a wide range of accelerators that allow groundbreaking science to be conducted. Accelerators bring particles to high levels of energy and make them collide with each other or with fixed targets, creating specific conditions that are of high interest to physicists. A chain of accelerators is used to ramp up the energy of particles and eventually inject them into the largest and most recent one: the Large Hadron Collider (LHC). Among this chain of machines is, for instance the Proton Synchrotron, which was started in 1959 and is still in operation. These machines, called "injectors”, keep evolving over time, as well as the related infrastructure. Massive decommissioning of obsolete cables started in 2015 at CERN in the frame of the so-called "injectors de-cabling project phase 1". Its goal was to replace aging cables and remove unused ones, freeing space for new cables necessary for upgrades and consolidation campaigns. To proceed with the de-cabling, a project co-ordination team was assembled. The start of this project led to the investigation of legacy cables throughout the organisation. The identification of cables stacked over half a century proved to be arduous. Phase 1 of the injectors de-cabling was implemented for 3 years with success after overcoming some difficulties. Phase 2, started 3 years later, focused on improving safety and structure with the introduction of a quality assurance procedure. This paper discusses the implementation of this quality assurance procedure throughout phase 2 of the project and the transition between the two phases. Over hundreds of kilometres of cable were removed in the injectors complex at CERN from 2015 to 2023.

Keywords: CERN, de-cabling, injectors, quality assurance procedure

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Authors: Azza Mohsin Al-Hashami, Reginald Victor

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Treatment of wastewater involves physical, chemical, and biological processes to remove the pollutants from wastewater. This study evaluates of the effectiveness of sewage treatment plants (STP) in Samail, Oman. Samail STP has tertiary treatment using conventional activated sludge with surface aeration. The collection of wastewater is through a network with a total length of about 60 km and also by tankers for the areas outside the network. Treated wastewater from this STP is used for the irrigation of vegetation in the STP premises and as a backwash for sand filters. Some treated water is supplied to the Samail municipality, which uses it for the landscaping, road construction, and 'the Million Date Palms' project. In this study, homogenous samples were taken from eight different treatment stages along the treatment continuum for one year, at a frequency of once a month, to evaluate the physical, chemical, and biological parameters. All samples were analyzed using the standard methods for the examination of water and wastewater. The spatial variations in water quality along the continuum are discussed. Despite these variations, the treated wastewater from Samail STP was of good quality, and most of the parameters are within class A category in Oman Standards for wastewater reuse and discharge.

Keywords: wastewater, STP, treatment, processes

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Authors: Diego Diaz H., Cristian Larroulet

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Although a large earthquake has clear and immediate consequences such as deaths, destruction of infrastructure and displacement (at least temporary) of part of the population, scientific research about the impact of a geological disaster in economic activity is inconclusive, especially when looking beyond the very short term. Estimating the economic impact years after a disaster strike is non-trivial since there is an unavoidable difficulty in attributing the observed effect to the disaster and not to other economic shocks. Case studies are performed that determine the impact of earthquakes in Chile, Japan, and New Zealand at a regional level by applying the synthetic control method, using the natural disaster as treatment. This consisted in constructing a counterfactual from every region in the same country that is not affected (or is slightly affected) by the earthquake. The results show that the economies of Canterbury and Tohoku achieved greater levels of GDP per capita in the years after the disaster than they would have in the absence of the disaster. For the case of Chile, however, the region of Maule experiences a decline in GDP per capita because of the earthquake. All the results are robust according to the placebo tests. Also, the results suggest that national institutional quality improve the growth process after the disaster.

Keywords: earthquake, economic growth, institutional quality, synthetic control

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Authors: Abhijit Pattnayak, Abhijith N.V, Deepak Kumar, Jayant Jain, Vijay Chaudhry

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Hard and dense ceramic coatings deposited on the surface provide the ideal solution to the poor tribological properties exhibited by some popular stainless steels like EN-36, 17-4PH, etc. These steels are widely used in nuclear, fertilizer, food processing, and marine industries under extreme environmental conditions. The present study focuses on the development of Al₂O₃-CeO₂-rGO-based coatings on the surface of 17-4PH steel using High-Velocity Oxygen Flame (HVOF) thermal spray process. The coating is developed using an oxyacetylene flame. Further, we report the physical (Density, Surface roughness, Surface energetics), Metallurgical (Scanning electron microscopy, X-ray diffraction, Raman), Mechanical (Hardness(Vickers and Nano Hard-ness)), Tribological (Wear, Scratch hardness) and Chemical (corrosion) characterization of both As-sprayed coating and the Substrate (17-4 PH steel). The comparison of the properties will help us to understand the microstructure-property relationship of the coating and reveal the necessity and challenges of such coatings.

Keywords: thermal spray process, HVOF, ceramic coating, hardness, wear, corrosion

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Authors: Iftikhar Ahmad, Mohammad Islam

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Thermally exfoliated graphene nanomaterial was reinforced into Al2O3 ceramic and the nanocomposites were consolidated using rapid high-frequency induction heat sintering route. The resulting nanocomposites demonstrated higher mechanical properties due to efficient GNS incorporation and chemical interaction with the Al2O3 matrix grains. The enhancement in mechanical properties is attributed to (i) uniformly-dispersed GNS in the consolidated structure (ii) ability of GNS to decorate Al2O3 nanoparticles and (iii) strong GNS/Al2O3 chemical interaction during colloidal mixing and pullout/crack bridging toughening mechanisms during mechanical testing. The GNS/Al2O3 interaction during different processing stages was thoroughly examined by thermal and structural investigation of the interfacial area. The formation of an intermediate aluminum oxycarbide phase (Al2OC) via a confined carbothermal reduction reaction at the GNS/Al2O3 interface was observed using advanced electron microscopes. The GNS surface roughness improves GNS/Al2O3 mechanical locking and chemical compatibility. The sturdy interface phase facilitates efficient load transfer and delayed failure through impediment of crack propagation. The resulting nanocomposites, therefore, offer superior toughness.

Keywords: ceramics, nanocomposites, interfaces, nanostructures, electron microscopy, Al2O3

Procedia PDF Downloads 343

Authors: Nenashev Yaroslav, Russkin Oleg

Abstract:

The mixing process is one of the most important and critical stages in many industrial sectors, such as chemistry, pharmaceuticals, and the food industry. When designing equipment with mixing impellers, technology developers often encounter working environments with complex physical properties and rheology. In such cases, the use of computational fluid dynamics tools is an excellent solution to mitigate risks and ensure the stable operation of the equipment. The research focuses on one of the designed reactors with mixing impellers intended for polymer synthesis. The study describes an approach to modeling reactors of similar configurations, taking into account the complex properties of the mixed liquids using the computational fluid dynamics (CFD) method. To achieve this goal, a complex 3D model was created, accurately replicating the functionality of chemical equipment. The model allows for the assessment of the hydrodynamic behavior of the reaction mixture inside the reactor, consideration of heat release due to the reaction, and the heat exchange between the reaction mixture and the cooling medium. The results indicate that the choice of the type and size of the mixing device significantly affects the efficiency of the mixing process inside the chemical reactor.

Keywords: CFD, mixing, blending, chemical reactor, non-Newton liquids, polymers

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Authors: Ziwei Huang, Jian Ge, Jie Shen, Jiantao Weng

Abstract:

Retrofitting of existing buildings plays a critical role to achieve sustainable development. This is being considered as one of the approaches to achieving sustainability in the built environment. In order to evaluate the different air-conditioning systems effectiveness and user satisfaction of the existing building which had transformed into green building effectively and accurately. This article takes the green office building in Zhejiang province, China as an example, analyzing the energy consumption, occupant satisfaction and indoor environment quality (IEQ) from the perspective of the thermal environment. This building is special because it combines ground source heat pump system and Variable Refrigerant Flow (VRF) air-conditioning system. Results showed that the ground source heat pump system(EUIa≈25.6) consumes more energy than VRF(EUIb≈23.8). In terms of a satisfaction survey, the use of the VRF air-conditioning was more satisfactory in temperature. However, the ground source heat pump is more satisfied in air quality.

Keywords: post-occupancy evaluation, green office building, air-conditioning systems, ground source heat pump system

Procedia PDF Downloads 183

Authors: M. Tazky, R. Hela, P. Novosad, L. Osuska

Abstract:

This paper deals with the possibility of safe incorporation fluidised bed combustion fly ash (waste material) into cement matrix together with next commonly used secondary raw material, which is high-temperature fly ash. Both of these materials have a very high pozzolanic ability, and the right combination could bring important improvements in both the physico-mechanical properties and the better durability of a cement composite. This paper tries to determine the correct methodology for designing green concrete by using modern methods measuring rheology of fresh concrete and following hydration processes. The use of fluidised bed combustion fly ash in cement composite production as an admixture is not currently common, but there are some real possibilities for its potential. The most striking negative aspect is its chemical composition which supports the development of new product formation, influencing the durability of the composite. Another disadvantage is the morphology of grains, which have a negative effect on consistency. This raises the question of how this waste can be used in concrete production to emphasize its positive properties and eliminate negatives. The focal point of the experiment carried out on cement pastes was particularly on the progress of hydration processes, aiming for the possible acceleration of pozzolanic reactions of both types of fly ash.

Keywords: high temperature fly ash, fluidized bed combustion fly ash, pozzolan, CaO (calcium oxide), rheology

Procedia PDF Downloads 194

Authors: Alejandro Carrasco-Pena, Mahmoud Omer, Nina Orlovskaya

Abstract:

The results of studies of microstructure, mechanical behavior, vibrational response, and flow field analysis of critically endangered staghorn coral (Acropora cervicornis) skeletons are reported. The CaCO₃ aragonite structure of a chemically-cleaned coral skeleton of A. cervicornis was studied by optical microscopy and computer tomography. The mechanical behavior was studied using uniaxial compression and Vickers hardness technique. The average maximum stress measured during skeleton uniaxial compression was 10.7 ± 2.24 MPa and Vickers hardness was 3.56 ± 0.31 GPa. The vibrational response of the aragonite structure was studied by micro-Raman spectroscopy, which showed a substantial dependence of the structure on applied compressive stress. The flow-field around a single coral skeleton forming vortices in the wake of the moving skeleton was measured using Particle Image Velocimetry (PIV). The results are important for further analysis of time-dependent mechanical fatigue behavior and predicting the lifetime of staghorn corals.

Keywords: failure, mechanical properties, microstructure, Raman spectroscopy

Procedia PDF Downloads 140

Authors: Stepan Hysek, Premysl Sedivka, Petra Gajdacova

Abstract:

Currently, structural composite materials contain cellulose-based particles (wood chips, fibers) bonded with synthetic adhesives containing formaldehyde (urea-formaldehyde, melamine-formaldehyde adhesives and others). Formaldehyde is classified as a volatile substance with provable carcinogenic effects on live organisms, and an emphasis has been put on continual reduction of its content in products. One potential solution could be the development of an agglomerated material which does not contain adhesives releasing formaldehyde. A potential alternative to formaldehyde-based adhesives could be polyurethane adhesives containing no formaldehyde. Such adhesives have been increasingly used in applications where a few years ago formaldehyde-based adhesives were the only option. Advantages of polyurethane adhesive in comparison with others in the industry include the high elasticity of the joint, which is able to resist dynamic stress, and resistance to increased humidity and climatic effects. These properties predict polyurethane adhesives to be used in OSB/EPS panel production. The objective of this paper is to develop an adhesive for bonding of sandwich panels made of material based on wood and other materials, e.g. SIP) and optimization of input components in order to obtain an adhesive with required properties suitable for bonding of the given materials without involvement of formaldehyde. It was found that polyurethane recyclate as a filler is suitable modification of polyurethane adhesive and results have clearly revealed that modified adhesive can be used for OSB/EPS panel production.

Keywords: adhesive, polyurethane, recyclate, SIP

Procedia PDF Downloads 253

Authors: Fryanto Anugrah Rhamdhani Rhamdhani, Hana Riana Permatasari

Abstract:

The aim of this study analyzes the inclusive of economic growth and analyzes the inclusive of economic growth determinant in regency and city (West Java Province). The background this study Economic Growth can do not afford to reduce poverty, Disparity and expand The Workforce. Referring Central Bureau Of Statistic West Java Province report in 2015 recorded only 5 regions able reduce poverty, 3 regions able reduce Gini Ratio and 7 regions able Workforce Absorption, meanwhile, 11 regions was improved Economic Growth. The Inclusive of Economic Growth definition based on various literature means the quality Economic Growth able reduce Poverty, Gini Ratio, and Workforce absorption. This study adopted the measurement Inclusive Economic of Growth Klassen and analyzes factor in Term Reducing Poverty, Gini Ratio, and the workforce Absorption. Data used panels data composite time series and cross-section including 25 regency and cities regions from Central Bureau Of Statistic West Java Province during 2014-2015. As a result, the measurement inclusive economic of growth Klassen 2014-2015 from 25 regency and cities shows all region does not inclusive reducing Poverty, only 2 regions able reduce Gini Ratio and 3 regions able increase Workforce absorption. Different from the result the measurement Inclusive Economic of Growth for workforce absorption, several regions shows a negative coefficient indicates Economic Growth decline Workforce absorption. The outcome of this study analyzes factor of Inclusive economic of Growth, so that give recommendations for government achieve inclusive economic of growth toward Sustainable Economic. Can be Concluded above low-quality Economic Growth, that due to all region does not inclusive Economic of Growth.

Keywords: inclusive economic growth, Gini ratio, poverty, workforce

Procedia PDF Downloads 250