Search results for: solid state
Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 9111

Search results for: solid state

8031 Applying Napoleoni's 'Shell-State' Concept to Jihadist Organisations's Rise in Mali, Nigeria and Syria/Iraq, 2011-2015

Authors: Francesco Saverio Angiò

Abstract:

The Islamic State of Iraq and the Levant / Syria (ISIL/S), Al-Qaeda in the Islamic Maghreb (AQIM) and People Committed to the Propagation of the Prophet's Teachings and Jihad, also known as ‘Boko Haram’ (BH), have fought successfully against Syria and Iraq, Mali, Nigeria’s government, respectively. According to Napoleoni, the ‘shell-state’ concept can explain the economic dimension and the financing model of the ISIL insurgency. However, she argues that AQIM and BH did not properly plan their financial model. Consequently, her idea would not be suitable to these groups. Nevertheless, AQIM and BH’s economic performances and their (short) territorialisation suggest that their financing models respond to a well-defined strategy, which they were able to adapt to new circumstances. Therefore, Napoleoni’s idea of ‘shell-state’ can be applied to the three jihadist armed groups. In the last five years, together with other similar entities, ISIL/S, AQIM and BH have been fighting against governments with insurgent tactics and terrorism acts, conquering and ruling a quasi-state; a physical space they presented as legitimate territorial entity, thanks to a puritan version of the Islamic law. In these territories, they have exploited the traditional local economic networks. In addition, they have contributed to the development of legal and illegal transnational business activities. They have also established a justice system and created an administrative structure to supply services. Napoleoni’s ‘shell-state’ can describe the evolution of ISIL/S, AQIM and BH, which has switched from an insurgency to a proto or a quasi-state entity, enjoying a significant share of power over territories and populations. Napoleoni first developed and applied the ‘Shell-state’ concept to describe the nature of groups such as the Palestine Liberation Organisation (PLO), before using it to explain the expansion of ISIL. However, her original conceptualisation emphasises on the economic dimension of the rise of the insurgency, focusing on the ‘business’ model and the insurgents’ financing management skills, which permits them to turn into an organisation. However, the idea of groups which use, coordinate and grab some territorial economic activities (at the same time, encouraging new criminal ones), can also be applied to administrative, social, infrastructural, legal and military levels of their insurgency, since they contribute to transform the insurgency to the same extent the economic dimension does. In addition, according to Napoleoni’s view, the ‘shell-state’ prism is valid to understand the ISIL/S phenomenon, because the group has carefully planned their financial steps. Napoleoni affirmed that ISIL/S carries out activities in order to promote their conversion from a group relying on external sponsors to an entity that can penetrate and condition local economies. On the contrary, ‘shell-state’ could not be applied to AQIM or BH, which are acting more like smugglers. Nevertheless, despite its failure to control territories, as ISIL has been able to do, AQIM and BH have responded strategically to their economic circumstances and have defined specific dynamics to ensure a flow of stable funds. Therefore, Napoleoni’s theory is applicable.

Keywords: shell-state, jihadist insurgency, proto or quasi-state entity economic planning, strategic financing

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8030 Bacteriological Culture Methods and its Uses in Clinical Pathology

Authors: Prachi Choudhary, Jai Gopal Sharma

Abstract:

Microbial cultures determine the type of organism, its abundance in the tested sample, or both. It is one of the primary diagnostic methods of microbiology. It is used to determine the cause of infectious disease by letting the agent multiply in a predetermined medium. Different bacteria produce colonies that may be very distinct from the bacterial species that produced them. To culture any pathogen or microorganism, we should first know about the types of media used in microbiology for culturing. Sometimes sub culturing is also done in various microorganisms if some mixed growth is seen in culture. Nearly 3 types of culture media based on consistency – solid, semi-solid, and liquid (broth) media; are further explained in the report. Then, The Five I's approach is a method for locating, growing, observing, and characterizing microorganisms, including inoculation and incubation. Isolation, inspection, and identification. For identification of bacteria, we have to culture the sample like urine, sputum, blood, etc., on suitable media; there are different methods of culturing the bacteria or microbe like pour plate method, streak plate method, swabbing by needle, pipetting, inoculation by loop, spreading by spreader, etc. After this, we see the bacterial growth after incubation of 24 hours, then according to the growth of bacteria antibiotics susceptibility test is conducted; this is done for sensitive antibiotics or resistance to that bacteria, and also for knowing the name of bacteria. Various methods like the dilution method, disk diffusion method, E test, etc., do antibiotics susceptibility tests. After that, various medicines are provided to the patients according to antibiotic sensitivity and resistance.

Keywords: inoculation, incubation, isolation, antibiotics suspectibility test, characterizing

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8029 Review of Affected Parameters on Flexural Behavior of Hollow Concrete Beams Reinforced by Steel/GFRP Rebars

Authors: Shahrad Ebrahimzadeh

Abstract:

Nowadays, the main efforts of the researchers aim to constantly evolve new, optimized and efficient construction materials and methods related to reinforced concrete beams. Due to the fewer applied materials and offering a higher structural efficiency compared to solid concrete beams with the same concrete area, hollow reinforced concrete beams (HRCB) internally reinforced with steel rebars have been employed extensively for bridge structural members and high-rise buildings. Many experimental studies have been conducted to investigate the behavior of hollow beams subjected to bending loading and found that the structural performance of HRCBs is critically affected by many design parameters. While the proper design of the HRCBs demonstrated comparable behavior to solid sections, inappropriate design leads beams to be extremely prone to brittle failure. Another potential issue that needs to be further investigated is the replacement of steel bars with suitable materials due to their susceptibility to corrosion. Hence, to develop a reliable construction system, the application of GFRP bars as a non-corroding material has been utilized. Furthermore, this study aims to critically review the different design parameters that affect the flexural performance of the HRCBs and recognize the gaps of knowledge in the better design and more effective use of this construction system.

Keywords: design parameters, experimental investigations, hollow reinforced concrete beams, steel, GFRP, flexural strength

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8028 Impacts of Teachers’ Cluster Model Meeting Intervention on Pupils’ Learning, Academic Achievement and Attitudinal Development in Oyo State, Nigeria

Authors: Olusola Joseph Adesina, Abiodun Ezekiel Adesina

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Efforts at improving the falling standard of education in the country call for the need-based assessment of the primary tier of education in Nigeria. Teachers’ cluster meeting intervention is a step towards enhancing the teachers’ professional competency, efficient and effective pupils’ academic achievement and attitudinal development. The study thus determined the impact of the intervention on pupils’ achievement in Oyo State, Nigeria. Three research questions and four hypotheses guided the study. Pre-test, post-test control group, quasi-experimental design was adopted for the study. Eight intact classes from eight different schools were randomly selected into treatment and control groups. Two response instruments, pupils academic achievement test (PAAT; r = 0.87) and pupils attitude to lesson scale (PALS; r = 0.80) were used for data collection. Mean, standard deviation and analysis of covariance (ANCOVA) were used to analyse the collected data. The results showed that the teachers’ cluster meeting have significant impact on pupils academic achievement (F (1,327) =41.79; p<0.05) and attitudinal development (F (1,327) =26.01; p<0.05) in the core subjects of primary schools in Oyo State, Nigeria. The study therefore recommended among others that teachers’ cluster meeting should be sustained for teachers’ professional development and pupils’ upgradement in the State.

Keywords: teachers’ cluster meeting, pupils’ academic achievement, pupils’ attitudinal development, academic achievement

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8027 Magnetic Structure and Transitions in 45% Mn Substituted HoFeO₃: A Neutron Diffraction Study

Authors: Karthika Chandran, Pulkit Prakash, Amitabh Das, Santhosh P. N.

Abstract:

Rare earth orthoferrites (RFeO₃) exhibit interesting and useful magnetic properties like multiferroicity, magnetodielectric coupling, spin reorientation (SR) and exchange bias. B site doped RFeO₃ are attracting attention due to the complex and tuneable magnetic transitions. In this work, 45% Mn-doped HoFeO₃ polycrystalline sample (HoFe₀.₅₅Mn₀.₄₅O₃) was synthesized by a solid-state reaction method. The magnetic structure and transitions were studied by magnetization measurements and neutron powder diffraction methods. The neutron diffraction patterns were taken at 13 different temperatures from 7°K to 300°K (7°K and 25°K to 300°K in 25°K intervals). The Rietveld refinement was carried out by using a FULLPROF suite. The magnetic space groups and the irreducible representations were obtained by SARAh module. The room temperature neutron diffraction refinement results indicate that the sample crystallizes in an orthorhombic perovskite structure with Pnma space group with lattice parameters a = 5.6626(3) Ǻ, b = 7.5241(3) Ǻ and c = 5.2704(2) Ǻ. The temperature dependent magnetization (M-T) studies indicate the presence of two magnetic transitions in the system ( TN Fe/Mn~330°K and TSR Fe/Mn ~290°K). The inverse susceptibility vs. temperature curve shows a linear behavior above 330°K. The Curie-Weiss fit in this region gives negative Curie constant (-34.9°K) indicating the antiferromagnetic nature of the transition. The neutron diffraction refinement results indicate the presence of mixed magnetic phases Γ₄(AₓFᵧG

Keywords: neutron powder diffraction, rare earth orthoferrites, Rietveld analysis, spin reorientation

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8026 The Risk Assessments of Water Quality in Selected White Water River in Malaysia

Authors: Jaffry Zakaria, Nor Azlina Hasbullah

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The research on water quality based on 'Water Quality Index' (WQI) has been on the run along Kampar River in Perak State of Malaysia. This study was conducted to achieve several key objective that determe the value of the parameters that were studied based on Water Quality Index (WQI). The parameters include Dissolved Oxygen (DO), pH, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Suspended Solids. In this study, three sampling stations were selected. Through observations from the researchers, several pollutions were found occurring along the research area such as the disposal of waste water directly without treatment from villagers, widespread dumping of solid waste and the development of the surrounding areas that contributed to the pollution of Sungai Kampar in Perak, Malaysia. Sungai Kampar is commonly used for water recreational activities as well as for bathing purposes. Results showed that Sungai Kampar is classified under category III. According to Interim National Water Quality Standard for Malaysia (INWQS), rivers in the third grade are clean but not suitable for river recreational activities. Therefore, there is a requirement to investigate and analysis the water quality of all white water rivers in Malaysia focusing on the area of water activities. The combination of technology and risk management based on risk assessments can help the recreational industry to survive in future.

Keywords: risk assessments, White Water River, water quality index (WQI), Interim National Water Quality Standard for Malaysia (INWQS)

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8025 Contribution of Urban Agriculture to the Livelihood of Urban Dwellers in Ilorin West Local Government Area of Kwara State, Nigeria

Authors: Okunola Solomon Olufemi

Abstract:

The study focused on the contribution of urban agriculture to the livelihood of 107 respondents in Kwara State of Nigeria. The study employed structured questionnaire to collect relevant data for the study while descriptive statistics such as frequency distribution and percentage were employed to analyses the objectives. Most respondents (82.9%), were one time or the other in a married state and they had formal education (80.4%) while many of the lot (58.9%) had superior education ranging from OND to Ph.D level. These farmers were either retired government workers or those trying to argument their family income or trying to be food sufficient. Most of the respondents (77.4%) had a farm size of less than or equal to 3 hectares showing that most the urban farmers were smallholders which might be as a result of stiff completion for land resource. Most of the respondents had a relatively large family size of 6 and above members. Most respondents used family labor (59.8%). Respondents in the study area also made use of the cooperatives and daily contributions for loanable funds, while few respondents utilized the formal sector. .Urban agriculture accounted for 84.4% of the Livelihood outcomes of the respondents. While non-farming activities contributed 17.6%.Most of the respondents (31.8%) participated in non-farming activities to generate extra income while their major constraints were shortage of land both in term of access and tenure (34.1%), limited access to resource and agricultural inputs (29.3%), and prohibitive urban policies and regulation (23.2%).

Keywords: poverty throes, urban agriculture, rigors of farming, non-farming, married state

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8024 The Role of the Internal Audit Unit in Detecting and Preventing Fraud at Public Universities in West Java, Indonesia

Authors: Fury Khristianty Fitriyah

Abstract:

This study aims to identify the extent of the role of the Satuan Pengawas Intern (Internal Audit Unit) in detecting and preventing fraud in public universities in West Java under the Ministry of Research, Technology and Higher Education. The research method applied was a qualitative case study approach, while the unit of analysis for this study is the Internal Audit Unit at each public university. Results of this study indicate that the Internal Audit Unit is able to detect and prevent fraud within a public university environment by means of red flags to mark accounting anomalies. These stem from inaccurate budget planning that prompts inappropriate use of funds, exacerbated by late disbursements of funds, which potentially lead to fictitious transactions, and discrepancies in recording state-owned assets into a state property management system (SIMAK BMN), which, if not conducted properly, potentially causes loss to the state.

Keywords: governance, internal control, fraud, public university

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8023 42CrMo4 Steel Flow Behavior Characterization for High Temperature Closed Dies Hot Forging in Automotive Components Applications

Authors: O. Bilbao, I. Loizaga, F. A. Girot, A. Torregaray

Abstract:

The current energetical situation and the high competitiveness in industrial sectors as the automotive one have become the development of new manufacturing processes with less energy and raw material consumption a real necessity. As consequence, new forming processes related with high temperature hot forging in closed dies have emerged in the last years as new solutions to expand the possibilities of hot forging and iron casting in the automotive industry. These technologies are mid-way between hot forging and semi-solid metal processes, working at temperatures higher than the hot forging but below the solidus temperature or the semi solid range, where no liquid phase is expected. This represents an advantage comparing with semi-solid forming processes as thixoforging, by the reason that no so high temperatures need to be reached in the case of high melting point alloys as steels, reducing the manufacturing costs and the difficulties associated to semi-solid processing of them. Comparing with hot forging, this kind of technologies allow the production of parts with as forged properties and more complex and near-net shapes (thinner sidewalls), enhancing the possibility of designing lightweight components. From the process viewpoint, the forging forces are significantly decreased, and a significant reduction of the raw material, energy consumption, and the forging steps have been demonstrated. Despite the mentioned advantages, from the material behavior point of view, the expansion of these technologies has shown the necessity of developing new material flow behavior models in the process working temperature range to make the simulation or the prediction of these new forming processes feasible. Moreover, the knowledge of the material flow behavior at the working temperature range also allows the design of the new closed dies concept required. In this work, the flow behavior characterization in the mentioned temperature range of the widely used in automotive commercial components 42CrMo4 steel has been studied. For that, hot compression tests have been carried out in a thermomechanical tester in a temperature range that covers the material behavior from the hot forging until the NDT (Nil Ductility Temperature) temperature (1250 ºC, 1275 ºC, 1300 ºC, 1325 ºC, 1350ºC, and 1375 ºC). As for the strain rates, three different orders of magnitudes have been considered (0,1 s-1, 1s-1, and 10s-1). Then, results obtained from the hot compression tests have been treated in order to adapt or re-write the Spittel model, widely used in automotive commercial softwares as FORGE® that restrict the current existing models up to 1250ºC. Finally, the obtained new flow behavior model has been validated by the process simulation in a commercial automotive component and the comparison of the results of the simulation with the already made experimental tests in a laboratory cellule of the new technology. So as a conclusion of the study, a new flow behavior model for the 42CrMo4 steel in the new working temperature range and the new process simulation in its application in automotive commercial components has been achieved and will be shown.

Keywords: 42CrMo4 high temperature flow behavior, high temperature hot forging in closed dies, simulation of automotive commercial components, spittel flow behavior model

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8022 Climate Change Adaptation Strategy Recommended for the Conservation of Biodiversity in Western Ghats, India

Authors: Mukesh Lal Das, Muthukumar Muthuchamy

Abstract:

Climate change Adaptation strategy (AS) is a scientific approach to dealing with the impacts of climate change (CC). Efforts are being made to contain the global emission of greenhouse gas within threshold limits, thereby limiting the rise of global temperature to an optimal level. Global Climate change is a spontaneous process; therefore, reversing the damage would take decades. The climate change adaptation strategy recommended by various stakeholders could be a key to resilience for biodiversity. The Indian Government has constituted the panel to synthesize the climate change action report at the federal and state levels. This review scavenged the published literature on the Western Ghats hotspots. And highlight the adaptation strategy recommended by diverse scientific actors to conserve biodiversity. It also reviews the grey literature adopted by state and federal governments and its effectiveness in mitigating the impacts on biodiversity. We have narrowed the scope of interest to the state action report by 6 Indian states such as Gujarat, Maharashtra, Goa, Karnataka, Kerala and Tamil Nadu, which host Western Ghats global biodiversity hotspot. Western Ghats(WGs) act as the water tower to the peninsular part of India, and its extensive watershed caters to the water demand of the Industry sector, Agriculture and urban community. Conservation of WGs is the key to the prosperity of Peninsular India. The global scientific community suggested more than 600+ Climate change adaptation strategies for the policymakers, stakeholders, and other state actors to take proactive actions. The preliminary analysis of the federal and the state action plan on climate change in the wake of CC indicate inadequacy in motion as per recommended scientific adaptation strategies. Tamil Nadu and Kerala state constitute nine effective adaptation strategies out of the 40+ recommended for Western Ghats conservation. And other four states' adaptation strategies are deficient, confusing and vague. Western Ghats' resilience capacity will soon or might have reached its threshold, and the frequency of severe drought and flash floods might upsurge manifold in the decades to come. The lack of a clear roadmap to climate change adaptation strategies in the federal and state action stirred us to identify the gap and address it by offering a holistic approach to WGs biodiversity conservation.

Keywords: adaptation strategy, biodiversity conservation, climate change, resilience, Western Ghats

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8021 Effect Different Moisture States of Surface-treated Recycled Concrete Aggregate on Properties of Fresh and Hardened Concrete

Authors: Sallehan Ismail, Mahyuddin Ramli

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This study examined the properties of fresh and hardened concretes as influenced by the moisture state of the coarse recycled concrete aggregates (RCA) after surface treatment. Surface treatment was performed by immersing the coarse RCA in a calcium metasilicate (CM) solution. The treated coarse RCA was maintained in three controlled moisture states, namely, air-dried, oven-dried, and saturated surface-dried (SSD), prior to its use in a concrete mix. The physical properties of coarse RCA were evaluated after surface treatment during the first phase of the experiment to determine the density and the water absorption characteristics of the RCA. The second phase involved the evaluation of the slump, slump loss, density, and compressive strength of the concretes that were prepared with different proportions of natural and treated coarse RCA. Controlling the moisture state of the coarse RCA after surface treatment was found to significantly influence the properties of the fresh and hardened concretes.

Keywords: moisture state, recycled concrete aggregate, surface treatment

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8020 A Study in Optimization of FSI(Floor Space Index) in Kerala

Authors: Anjali Suresh

Abstract:

Kerala is well known for its unique settlement pattern; comprising the most part, a continuous spread of habitation. The notable urbanization trend in Kerala is urban spread rather than concentration which points out the increasing urbanization of peripheral areas of existing urban centers. This has thrown a challenge for the authorities to cater the needs of the urban population like to provide affordable housing and infrastructure facilities to sustain their livelihood; which is a matter of concern that needs policy attention in fixing the optimum FSI value. Based on recent reports (Post Disaster Need Analysis –PDNA) from the UN, addressing the unsafe situation of the carpet FAR/FSI practice in the state showcasing the varying geological & climatic conditions should also be the matter of concern. The FSI (Floor space index- the ratio of the built-up space on a plot to the area of the plot) value is certainly one of the key regulation factors in checking the land utilization for the varying occupancies desired for the overall development of a state with limitation in land availability when compared to its neighbors. The pattern of urbanization, physical conditions, topography, etc., varies within the state and can change remarkably over time which identifies that the practicing FSI norms in Kerala does not fulfils the intended function. Thus the FSI regulation is expected to change dynamically from location to location. So for determining the optimum value of FSI /FAR of a region in the state of Kerala, the government agencies should consider the optimum land utilization for the growing urbanization. On the other hand, shall keep in check the overutilization of the same in par with environmental and geographic nature. Therefore the study identifies parameters that should be considered for assigning FSI within the Kerala context, and through expert surveys; opinions arrive at a methodology for assigning an optimum FSI value of a region in the state of Kerala.

Keywords: floor space index, urbanization, density, civic pressure, optimization

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8019 Cover Layer Evaluation in Soil Organic Matter of Mixing and Compressed Unsaturated

Authors: Nayara Torres B. Acioli, José Fernando T. Jucá

Abstract:

The uncontrolled emission of gases in urban residues' embankment located near urban areas is a social and environmental problem, common in Brazilian cities. Several environmental impacts in the local and global scope may be generated by atmospheric air contamination by the biogas resulted from the decomposition of solid urban materials. In Brazil, the cities of small size figure mostly with 90% of all cities, with the population smaller than 50,000 inhabitants, according to the 2011 IBGE' census, most of the landfill covering layer is composed of clayey, pure soil. The embankments undertaken with pure soil may reach up to 60% of retention of methane, for the other 40% it may be dispersed into the atmosphere. In face of this figures the oxidative covering layer is granted some space of study, envisaging to reduce this perceptual available in the atmosphere, releasing, in spite of methane, carbonic gas which is almost 20 times as less polluting than Methane. This paper exposes the results of studies on the characteristics of the soil used for the oxidative coverage layer of the experimental embankment of Solid Urban Residues (SUR), built in Muribeca-PE, Brazil, supported of the Group of Solid Residues (GSR), located at Federal University of Pernambuco, through laboratory vacuum experiments (determining the characteristics curve), granularity, and permeability, that in soil with saturation over 85% offers dramatic drops in the test of permeability to the air, by little increments of water, based in the existing Brazilian norm for this procedure. The suction was studied, as in the other tests, from the division of prospection of an oxidative coverage layer of 60cm, in the upper half (0.1 m to 0.3 m) and lower half (0.4 m to 0.6 m). Therefore, the consequences to be presented from the lixiviation of the fine materials after 5 years of finalization of the embankment, what made its permeability increase. Concerning its humidity, it is most retained in the upper part, that comprises the compound, with a difference in the order of 8 percent the superior half to inferior half, retaining the least suction from the surface. These results reveal the efficiency of the oxidative coverage layer in retaining the rain water, it has a lower cost when compared to the other types of layer, offering larger availability of this layer as an alternative for a solution for the appropriate disposal of residues.

Keywords: oxidative coverage layer, permeability, suction, saturation

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8018 The Use of Substances and Sports Performance among Youth: Implications for Lagos State Sports

Authors: Osifeko Olalekan Remigious, Adesanya Adebisi Joseph, Omolade Akinmade Olatunde

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The focus of this study was to determine the factors associated with the use of substances for sport performance of youth in Lagos state sport. Questionnaire was the instrument used for the study. Descriptive research method was used. The estimated population for the study was 2000 sport men and women. The sample size was 200 respondents for purposive sampling techniques were used. The instrument was validated in it content and constructs value. The instrument was administered with the assistance of the coaches. Same 200 copies administered were returned. The data obtained was analysed using simple percentage and chi-square (x2) for stated hypothesis at 0.05 level of significance. The finding reveal that sport injuries exercise induced and anaphylaxis and asthma and feeling of loss of efficacy associated with alcohol used on sport performance among the users of substances. Alcohol users are recommended to partake in sport like swimming, basketball and volleyball because they have space of time for resting while at play. Government should be fully in charge of the health of sport men and women.

Keywords: implications, Lagos state, substances, sports performance, youth

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8017 Checklist of Odonata of Shasha Forest Reserve, Ife Southern, Osun State, Nigeria

Authors: Ehikhamele Isaac Erhomosele, Ogbogu Sunday Sylvester

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A biodiversity survey was conducted in Shasha Forest Reserve, Ife southern, Osun State, Nigeria between May 2019 to April 2021 with a view to determining the nature of Odonata fauna of the forest. A total number of 1055 individuals of adult dragonflies and damselflies belonging to 8 families (Aeshnidae, Calopterygidae, Chlorocyphidae, Coenagrionidae, Gomphidae, Lestidae, Libellulidae and Platycnemididae) were recorded. Five (5) of these families of which belong to the suborder Zygoptera, and the remaining three (3) to Anisoptera. Libellulidae was the most abundant family while Gomphidae recorded the least representative. No new species of Odonata was recorded. Most of the families reported were previously been documented in the tropical region. Logging activities and human disturbance have been attributed to the nature of Odonata species in the Forest. It is therefore recommended that logging should be restricted to designated areas of the forest and regulated by the Department of Forestry of Osun State Ministry of Agriculture and Natural Resources in conjunction with the Federal Ministry of Environment.

Keywords: checklist, Odonata, Shasha, families

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8016 Direct Measurements of the Electrocaloric Effect in Solid Ferroelectric Materials via Thermoreflectance

Authors: Layla Farhat, Mathieu Bardoux, Stéphane Longuemart, Ziad Herro, Abdelhak Hadj Sahraoui

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Electrocaloric (EC) effect refers to the isothermal entropy or adiabatic temperature changes of a dielectric material induced by an external electric field. This phenomenon has been largely ignored for application because only modest EC effects (2.6

Keywords: electrocaloric effect, thermoreflectance, ferroelectricity, cooling system

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8015 Spin-Dependent Transport Signatures of Bound States: From Finger to Top Gates

Authors: Yun-Hsuan Yu, Chi-Shung Tang, Nzar Rauf Abdullah, Vidar Gudmundsson

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Spin-orbit gap feature in energy dispersion of one-dimensional devices is revealed via strong spin-orbit interaction (SOI) effects under Zeeman field. We describe the utilization of a finger-gate or a top-gate to control the spin-dependent transport characteristics in the SOI-Zeeman influenced split-gate devices by means of a generalized spin-mixed propagation matrix method. For the finger-gate system, we find a bound state in continuum for incident electrons within the ultra-low energy regime. For the top-gate system, we observe more bound-state features in conductance associated with the formation of spin-associated hole-like or electron-like quasi-bound states around band thresholds, as well as hole bound states around the reverse point of the energy dispersion. We demonstrate that the spin-dependent transport behavior of a top-gate system is similar to that of a finger-gate system only if the top-gate length is less than the effective Fermi wavelength.

Keywords: spin-orbit, zeeman, top-gate, finger-gate, bound state

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8014 Examining Terrorism through a Constructivist Framework: Case Study of the Islamic State

Authors: Shivani Yadav

Abstract:

The Study of terrorism lends itself to the constructivist framework as constructivism focuses on the importance of ideas and norms in shaping interests and identities. Constructivism is pertinent to understand the phenomenon of a terrorist organization like the Islamic State (IS), which opportunistically utilizes radical ideas and norms to shape its ‘politics of identity’. This ‘identity’, which is at the helm of preferences and interests of actors, in turn, shapes actions. The paper argues that an effective counter-terrorism policy must recognize the importance of ideas in order to counter the threat arising from acts of radicalism and terrorism. Traditional theories of international relations, with an emphasis on state-centric security problematic, exhibit several limitations and problems in interpreting the phenomena of terrorism. With the changing global order, these theories have failed to adapt to the changing dimensions of terrorism, especially ‘newer’ actors like the Islamic State (IS). The paper observes that IS distinguishes itself from other terrorist organizations in the way that it recruits and spreads its propaganda. Not only are its methods different, but also its tools (like social media) are new. Traditionally, too, force alone has rarely been sufficient to counter terrorism, but it seems especially impossible to completely root out an organization like IS. Time is ripe to change the discourse around terrorism and counter-terrorism strategies. The counter-terrorism measures adopted by states, which primarily focus on mitigating threats to the national security of the state, are preoccupied with statist objectives of the continuance of state institutions and maintenance of order. This limitation prevents these theories from addressing the questions of justice and the ‘human’ aspects of ideas and identity. These counter-terrorism strategies adopt a problem-solving approach that attempts to treat the symptoms without diagnosing the disease. Hence, these restrictive strategies fail to look beyond calculated retaliation against violent actions in order to address the underlying causes of discontent pertaining to ‘why’ actors turn violent in the first place. What traditional theories also overlook is that overt acts of violence may have several causal factors behind them, some of which are rooted in the structural state system. Exploring these root causes through the constructivist framework helps to decipher the process of ‘construction of terror’ and to move beyond the ‘what’ in theorization in order to describe ‘why’, ‘how’ and ‘when’ terrorism occurs. Study of terrorism would much benefit from a constructivist analysis in order to explore non-military options while countering the ideology propagated by the IS.

Keywords: constructivism, counter terrorism, Islamic State, politics of identity

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8013 Temperature Evolution, Microstructure and Mechanical Properties of Heat-Treatable Aluminum Alloy Welded by Friction Stir Welding: Comparison with Tungsten Inert Gas

Authors: Saliha Gachi, Mouloud Aissani, Fouad Boubenider

Abstract:

Friction Stir Welding (FSW) is a solid-state welding technique that can join material without melting the plates to be welded. In this work, we are interested to demonstrate the potentiality of FSW for joining the heat-treatable aluminum alloy 2024-T3 which is reputed as difficult to be welded by fusion techniques. Thereafter, the FSW joint is compared with another one obtained from a conventional fusion process Tungsten Inert Gas (TIG). FSW welds are made up using an FSW tool mounted on a milling machine. Single pass welding was applied to fabricated TIG joint. The comparison between the two processes has been made on the temperature evolution, mechanical and microstructure behavior. The microstructural examination revealed that FSW weld is composed of four zones: Base metal (BM), Heat affected zone (HAZ), Thermo-mechanical affected zone (THAZ) and the nugget zone (NZ). The NZ exhibits a recrystallized equiaxed refined grains that induce better mechanical properties and good ductility compared to TIG joint where the grains have a larger size in the welded region compared with the BM due to the elevated heat input. The microhardness results show that, in FSW weld, the THAZ contains the lowest microhardness values and increase in the NZ; however, in TIG process, the lowest values are localized on the NZ.

Keywords: friction stir welding, tungsten inert gaz, aluminum, microstructure

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8012 Development of Entrepreneurship in Industry on the Basis of Regulation of Transnational Production Chains in the Russian Arctic

Authors: E. N. Vetrova, L.V. Lapochkina, N. V. Nikulina

Abstract:

In the national economy, entrepreneurship plays the role of a buffer between economy and policy for it contributes to improving budget effectiveness and decreasing dependence of economy on the state. Entrepreneurship in industry makes it possible to increase the added value that is formed in production chains and to decrease dependence on import. Under the current circumstances, when sanctions are being imposed, this is especially relevant for Russia and for the realization of projects in the Russian Arctic. However, development of entrepreneurship in industry requires an enlightened state policy. The purpose of the research is elaboration of recommendations for improving economic effectiveness of the realization of the Arctic projects on the basis of conceptual proposals for the development of entrepreneurship in industry. The paper presents the studies of the extractive industry role in the Russian economy and proves its raw material character. The analysis of production chains in industry on the basis of the conception of the added value global chains demonstrated a low added value formed by Russian companies. The study of changes in the structure of economy based on systemic, statistical and comparative analyses revealed no positive changes in the structure of economy over the period under consideration. This is a manifestation of ineffectiveness of the Russian industrial policy in general and within the Arctic region in particular. The authors identified the problems information and implementation of the state industrial policy in the Arctic region and in the development of national entrepreneurship, analyzed the shortcomings of the current state policy in the sphere of the Russian industry. On the basis of the conducted studies, the authors formulated conceptual approaches to change the state policy in the Arctic. The basic idea of the authors is to substantiate the focus of the state regulation on the development of entrepreneurship in industry in the process of the Russian Arctic exploration. At the same time another problem is solved–that of the development of the manufacturing industry in the southern regions of the northwestern part of Russia. The criterion of effectiveness in this case is the economic effectiveness.

Keywords: entrepreneurship in industry, global chains of the added value, government regulation, industrial policies, production chains in the arctic region, economic effectiveness

Procedia PDF Downloads 386
8011 Offline Parameter Identification and State-of-Charge Estimation for Healthy and Aged Electric Vehicle Batteries Based on the Combined Model

Authors: Xiaowei Zhang, Min Xu, Saeid Habibi, Fengjun Yan, Ryan Ahmed

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Recently, Electric Vehicles (EVs) have received extensive consideration since they offer a more sustainable and greener transportation alternative compared to fossil-fuel propelled vehicles. Lithium-Ion (Li-ion) batteries are increasingly being deployed in EVs because of their high energy density, high cell-level voltage, and low rate of self-discharge. Since Li-ion batteries represent the most expensive component in the EV powertrain, accurate monitoring and control strategies must be executed to ensure their prolonged lifespan. The Battery Management System (BMS) has to accurately estimate parameters such as the battery State-of-Charge (SOC), State-of-Health (SOH), and Remaining Useful Life (RUL). In order for the BMS to estimate these parameters, an accurate and control-oriented battery model has to work collaboratively with a robust state and parameter estimation strategy. Since battery physical parameters, such as the internal resistance and diffusion coefficient change depending on the battery state-of-life (SOL), the BMS has to be adaptive to accommodate for this change. In this paper, an extensive battery aging study has been conducted over 12-months period on 5.4 Ah, 3.7 V Lithium polymer cells. Instead of using fixed charging/discharging aging cycles at fixed C-rate, a set of real-world driving scenarios have been used to age the cells. The test has been interrupted every 5% capacity degradation by a set of reference performance tests to assess the battery degradation and track model parameters. As battery ages, the combined model parameters are optimized and tracked in an offline mode over the entire batteries lifespan. Based on the optimized model, a state and parameter estimation strategy based on the Extended Kalman Filter (EKF) and the relatively new Smooth Variable Structure Filter (SVSF) have been applied to estimate the SOC at various states of life.

Keywords: lithium-ion batteries, genetic algorithm optimization, battery aging test, parameter identification

Procedia PDF Downloads 268
8010 Survey of Indoor Radon/Thoron Concentrations in High Lung Cancer Incidence Area in India

Authors: Zoliana Bawitlung, P. C. Rohmingliana, L. Z. Chhangte, Remlal Siama, Hming Chungnunga, Vanram Lawma, L. Hnamte, B. K. Sahoo, B. K. Sapra, J. Malsawma

Abstract:

Mizoram state has the highest lung cancer incidence rate in India due to its high-level consumption of tobacco and its products which is supplemented by the food habits. While smoking is mainly responsible for this incidence, the effect of inhalation of indoor radon gas cannot be discarded as the hazardous nature of this radioactive gas and its progenies on human population have been well-established worldwide where the radiation damage to bronchial cells eventually can be the second leading cause of lung cancer next to smoking. It is also known that the effect of radiation, however, small may be the concentration, cannot be neglected as they can bring about the risk of cancer incidence. Hence, estimation of indoor radon concentration is important to give a useful reference against radiation effects as well as establishing its safety measures and to create a baseline for further case-control studies. The indoor radon/thoron concentrations in Mizoram had been measured in 41 dwellings selected on the basis of spot gamma background radiation and construction type of the houses during 2015-2016. The dwellings were monitored for one year, in 4 months cycles to indicate seasonal variations, for the indoor concentration of radon gas and its progenies, outdoor gamma dose, and indoor gamma dose respectively. A time-integrated method using Solid State Nuclear Track Detector (SSNTD) based single entry pin-hole dosimeters were used for measurement of indoor Radon/Thoron concentration. Gamma dose measurements for indoor as well as outdoor were carried out using Geiger Muller survey meters. Seasonal variation of indoor radon/ thoron concentration was monitored. The results show that the annual average radon concentrations varied from 54.07 – 144.72 Bq/m³ with an average of 90.20 Bq/m³ and the annual average thoron concentration varied from 17.39 – 54.19 Bq/m³ with an average of 35.91 Bq/m³ which are below the permissible limit. The spot survey of gamma background radiation level varies between 9 to 24 µR/h inside and outside the dwellings throughout Mizoram which are all within acceptable limits. From the above results, there is no direct indication that radon/thoron is responsible for the high lung cancer incidence in the area. In order to find epidemiological evidence of natural radiations to high cancer incidence in the area, one may need to conduct a case-control study which is beyond this scope. However, the derived data of measurement will provide baseline data for further studies.

Keywords: background gamma radiation, indoor radon/thoron, lung cancer, seasonal variation

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8009 Ethical Considerations in the Execution of Post-Fuel Subsidy Removal Support Initiatives in Kwara State, Nigeria: A Focus from Islamic Principles

Authors: Muhammad Jum’at Dasuki

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This study investigates the ethical implications of post-fuel subsidy removal support initiatives in Kwara State, Nigeria, with a focus on the application of Islamic principles. The contentious issue of subsidy removal carries significant social and economic consequences, emphasizing the crucial role of ethical considerations in policy implementation. The research provides a comprehensive background on fuel subsidy removal in Nigeria and its implications. Examining post-fuel subsidy removal palliative measures in Kwara State, the study focuses on design and implementation challenges, ethical considerations, transparency, equity, and public trust. Utilizing a case study approach offers insights and best practices. The methodology includes primary sources through in-depth oral interviews and secondary sources like textbooks and journals, aiming for a holistic understanding of the ethical dimensions of support initiatives within the context of Islamic principles in Kwara State. The objective is to contribute to policy decisions and community development. The study recommends an ethically sound implementation of post-fuel subsidy removal support initiatives, emphasizing transparency, accountability, and inclusivity. It advocates for the inclusiveness of governmental palliatives, reaching both civil servants and common individuals in the state. Continuous distribution during fuel subsidy removal challenges is deemed vital. Additionally, extending free or subsidized transportation beyond higher institutions to the general populace is suggested. Consideration should also be given to reducing governmental hospital bills or providing free health services. The study underscores the importance of Islamic ethics in Nigerian governance and employs a case study approach to assess palliative measures in Kwara State, offering practical insights for policymakers and stakeholders.

Keywords: considerations, ethical, palliative, post-fuel subsidy removal

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8008 Application and Regeneration of CuMnCeO Catalyst Supporting K₂CO₃ Sorbent Adapted to CO Oxidation and CO₂ Absorption

Authors: Jin Lin, Shouxiang Lu, Kim Meow Liew

Abstract:

The requirement for the long-term mission of the submarine and spacecraft has made the removal of CO₂ and trace CO the critical technology to ensure the health and life of the crews. In this work, CuMnCe, a metal oxide catalyst, supporting K₂CO₃ sorbent was prepared by the wet-solid state impregnation method to realize the integrated CO and CO₂ removal, which might also reduce the volume/mass load of the purification units in the limited space. The as-prepared samples with different addition amount of K₂CO₃ were tested using the fixed bed reactor to reveal the CO oxidation and CO₂ absorption behavior. And the regeneration and stability experiments were also conducted. The results showed that the samples realized the catalyst and sorbent integration to capture CO and CO₂ at the same time. The addition amount of the sorbent had a weak influence on the CO oxidation performance. While the addition amount affected the CO₂ sorption efficiency and capacity significantly. Meanwhile, the presence of water vapor could reduce the CO oxidation activity of the samples similarly, whether with K2CO3 sorbent addition or not. Furtherly, regeneration and stability experiment results showed that the samples after 3-5 times regeneration exhibited almost the same performance of CO and CO₂ removal. Summarily, CuMnCe catalyst supporting K₂CO₃ sorbent could be a good attempt to control CO and CO₂ pollutants generated from the daily equipment running and staff breathing in the confined space such as submarine and spacecraft.

Keywords: CO oxidation, CO₂ absorptio, potassium carbonate, CuMnCe metal oxide, confined space

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8007 An Efficient Hybrid Feedstock Pretreatment Technique for the Release of Fermentable Sugar from Cassava Peels for Biofuel Production

Authors: Gabriel Sanjo Aruwajoye, E. B. Gueguim Kana

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Agricultural residues present a low-cost feedstock for bioenergy production around the world. Cassava peels waste are rich in organic molecules that can be readily converted to value added products such as biomaterials and biofuels. However, due to the presence of high proportion of structural carbohydrates and lignin, the hydrolysis of this feedstock is imperative to achieve maximum substrate utilization and energy yield. This study model and optimises the release of Fermentable Sugar (FS) from cassava peels waste using the Response Surface Methodology. The investigated pretreatment input parameters consisted of soaking temperature (oC), soaking time (hours), autoclave duration (minutes), acid concentration (% v/v), substrate solid loading (% w/v) within the range of 30 to 70, 0 to 24, 5 to 20, 0 to 5 and 2 to 10 respectively. The Box-Behnken design was used to generate 46 experimental runs which were investigated for FS release. The obtained data were used to fit a quadratic model. A coefficient of determination of 0.87 and F value of 8.73 was obtained indicating the good fitness of the model. The predicted optimum pretreatment conditions were 69.62 oC soaking temperature, 2.57 hours soaking duration, 5 minutes autoclave duration, 3.68 % v/v HCl and 9.65 % w/v solid loading corresponding to FS yield of 91.83g/l (0.92 g/g cassava peels) thus 58% improvement on the non-optimised pretreatment. Our findings demonstrate an efficient pretreatment model for fermentable sugar release from cassava peels waste for various bioprocesses.

Keywords: feedstock pretreatment, cassava peels, fermentable sugar, response surface methodology

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8006 Modeling of Hot Casting Technology of Beryllium Oxide Ceramics with Ultrasonic Activation

Authors: Zamira Sattinova, Tassybek Bekenov

Abstract:

The article is devoted to modeling the technology of hot casting of beryllium oxide ceramics. The stages of ultrasonic activation of beryllium oxide slurry in the plant vessel to improve the rheological property, hot casting in the moulding cavity with cooling and solidification of the casting are described. Thermoplastic slurry (hereinafter referred to as slurry) shows the rheology of a non-Newtonian fluid with yield and plastic viscosity. Cooling-solidification of the slurry in the forming cavity occurs in the liquid, taking into account crystallization and solid state. In this work is the method of calculation of hot casting of the slurry using the method of effective molecular viscosity of viscoplastic fluid. It is shown that the slurry near the cooled wall is in a state of crystallization and plasticity, and the rest may still be in the liquid phase. Nonuniform distribution of temperature, density and concentration of kinetically free binder takes place along the cavity section. This leads to compensation of shrinkage by the influx of slurry from the liquid into the crystallization zones and plasticity of the castings. In the plasticity zone, the shrinkage determined by the concentration of kinetically free binder is compensated under the action of the pressure gradient. The solidification mechanism, as well as the mechanical behavior of the casting mass during casting, the rheological and thermophysical properties of the thermoplastic BeO slurry due to ultrasound exposure have not been well studied. Nevertheless, experimental data allow us to conclude that the effect of ultrasonic vibrations on the slurry mass leads to it: a change in structure, an increase in technological properties, a decrease in heterogeneity and a change in rheological properties. In the course of experiments, the effect of ultrasonic treatment and its duration on the change in viscosity and ultimate shear stress of the slurry depending on temperature (55-75℃) and the mass fraction of the binder (10 - 11.7%) have been studied. At the same time, changes in these properties before and after ultrasound exposure have been analyzed, as well as the nature of the flow in the system under study. The experience of operating the unit with ultrasonic impact has shown that at the same time, the casting capacity of the slurry increases by an average of 15%, and the viscosity decreases by more than half. Experimental study of physicochemical properties and phase change with simultaneous consideration of all factors affecting the quality of products in the process of continuous casting is labor-intensive. Therefore, an effective way to control the physical processes occurring in the formation of articles with predetermined properties and shapes is to simulate the process and determine its basic characteristics. The results of the calculations show the whole stage of hot casting of beryllium oxide slurry, taking into account the change in its state of aggregation. Ultrasonic treatment improves rheological properties and increases the fluidity of the slurry in the forming cavity. Calculations show the influence of velocity, temperature factors and structural data of the cavity on the cooling-solidification process of the casting. In the calculations, conditions for molding with shrinkage of the slurry by hot casting have been found, which makes it possible to obtain a solidifying product with a uniform beryllium oxide structure at the outlet of the cavity.

Keywords: hot casting, thermoplastic slurry molding, shrinkage, beryllium oxide

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8005 Conduits of Political Corruption and Patronage in South African Government

Authors: Sandiso Mahlala, Fulufhelo Netswera

Abstract:

Anecdotes of corruption and clear-cut lines of patronage in political parties and the government are frequently featured in South African newspapers and news media. Such graft and favouritism have institutionalised themselves more and more, resulting in the phenomenon of governmental capture and the diversion of Covid-19 relief monies. In order to further their own interests, political elites and those working in the public and private sectors influenced government decisions in this way. This paper presents examples of state capture, Covid-19 corruption, and patronage, as well as how these have a negative impact on broader governance and society at large. The fact that such corruption and patronage are occurring at a time when the South African economy is stagnating is particularly troubling since it implies that more people are getting less and raises concerns about the country's future political stability. This article further examines how party patronage as one method by which political parties exploit the state. The conceptual nature of the study is supported by a survey of the relevant literature from a range of sources, such as government regulations, media excepts, and scholarly works.

Keywords: political corruption, political patronage, patronage, state capture, COVID-19, corruption, South Africa

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8004 A Comparative Analysis of an All-Optical Switch Using Chalcogenide Glass and Gallium Arsenide Based on Nonlinear Photonic Crystal

Authors: Priyanka Kumari Gupta, Punya Prasanna Paltani, Shrivishal Tripathi

Abstract:

This paper proposes a nonlinear photonic crystal ring resonator-based all-optical 2 × 2 switch. The nonlinear Kerr effect is used to evaluate the essential 2 x 2 components of the photonic crystal-based optical switch, including the bar and cross states. The photonic crystal comprises a two-dimensional square lattice of dielectric rods in an air background. In the background air, two different dielectric materials are used for this comparison study separately. Initially with chalcogenide glass rods, then with GaAs rods. For both materials, the operating wavelength, bandgap diagram, operating power intensities, and performance parameters, such as the extinction ratio, insertion loss, and cross-talk of an optical switch, have also been estimated using the plane wave expansion and the finite-difference time-domain method. The chalcogenide glass material (Ag20As32Se48) has a high refractive index of 3.1 which is highly suitable for switching operations. This dielectric material is immersed in an air background with a nonlinear Kerr coefficient of 9.1 x 10-17 m2/W. The resonance wavelength is at 1552 nm, with the operating power intensities at the cross-state and bar state around 60 W/μm2 and 690 W/μm2. The extinction ratio, insertion loss, and cross-talk value for the chalcogenide glass at the cross-state are 17.19 dB, 0.051 dB, and -17.14 dB, and the bar state, the values are 11.32 dB, 0.025 dB, and -11.35 dB respectively. The gallium arsenide (GaAs) dielectric material has a high refractive index of 3.4, a direct bandgap semiconductor material highly preferred nowadays for switching operations. This dielectric material is immersed in an air background with a nonlinear Kerr coefficient of 3.1 x 10-16 m2/W. The resonance wavelength is at 1558 nm, with the operating power intensities at the cross-state and bar state around 110 W/μm2 and 200 W/μm2. The extinction ratio, insertion loss, and cross-talk value for the chalcogenide glass at the cross-state are found to be 3.36.19 dB, 2.436 dB, and -5.8 dB, and for the bar state, the values are 15.60 dB, 0.985 dB, and -16.59 dB respectively. This paper proposes an all-optical 2 × 2 switch based on a nonlinear photonic crystal using a ring resonator. The two-dimensional photonic crystal comprises a square lattice of dielectric rods in an air background. The resonance wavelength is in the range of photonic bandgap. Later, another widely used material, GaAs, is also considered, and its performance is compared with the chalcogenide glass. Our presented structure can be potentially applicable in optical integration circuits and information processing.

Keywords: photonic crystal, FDTD, ring resonator, optical switch

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8003 Microstructural Characterization of Bitumen/Montmorillonite/Isocyanate Composites by Atomic Force Microscopy

Authors: Francisco J. Ortega, Claudia Roman, Moisés García-Morales, Francisco J. Navarro

Abstract:

Asphaltic bitumen has been largely used in both industrial and civil engineering, mostly in pavement construction and roofing membrane manufacture. However, bitumen as such is greatly susceptible to temperature variations, and dramatically changes its in-service behavior from a viscoelastic liquid, at medium-high temperatures, to a brittle solid at low temperatures. Bitumen modification prevents these problems and imparts improved performance. Isocyanates like polymeric MDI (mixture of 4,4′-diphenylmethane di-isocyanate, 2,4’ and 2,2’ isomers, and higher homologues) have shown to remarkably enhance bitumen properties at the highest in-service temperatures expected. This comes from the reaction between the –NCO pendant groups of the oligomer and the most polar groups of asphaltenes and resins in bitumen. In addition, oxygen diffusion and/or UV radiation may provoke bitumen hardening and ageing. With the purpose of minimizing these effects, nano-layered-silicates (nanoclays) are increasingly being added to bitumen formulations. Montmorillonites, a type of naturally occurring mineral, may produce a nanometer scale dispersion which improves bitumen thermal, mechanical and barrier properties. In order to increase their lipophilicity, these nanoclays are normally treated so that organic cations substitute the inorganic cations located in their intergallery spacing. In the present work, the combined effect of polymeric MDI and the commercial montmorillonite Cloisite® 20A was evaluated. A selected bitumen with penetration within the range 160/220 was modified with 10 wt.% Cloisite® 20A and 2 wt.% polymeric MDI, and the resulting ternary composites were characterized by linear rheology, X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). The rheological tests evidenced a notable solid-like behavior at the highest temperatures studied when bitumen was just loaded with 10 wt.% Cloisite® 20A and high-shear blended for 20 minutes. However, if polymeric MDI was involved, the sequence of addition exerted a decisive control on the linear rheology of the final ternary composites. Hence, in bitumen/Cloisite® 20A/polymeric MDI formulations, the previous solid-like behavior disappeared. By contrast, an inversion in the order of addition (bitumen/polymeric MDI/ Cloisite® 20A) enhanced further the solid-like behavior imparted by the nanoclay. In order to gain a better understanding of the factors that govern the linear rheology of these ternary composites, a morphological and microstructural characterization based on XRD and AFM was conducted. XRD demonstrated the existence of clay stacks intercalated by bitumen molecules to some degree. However, the XRD technique cannot provide detailed information on the extent of nanoclay delamination, unless the entire fraction has effectively been fully delaminated (situation in which no peak is observed). Furthermore, XRD was unable to provide precise knowledge neither about the spatial distribution of the intercalated/exfoliated platelets nor about the presence of other structures at larger length scales. In contrast, AFM proved its power at providing conclusive information on the morphology of the composites at the nanometer scale and at revealing the structural modification that yielded the rheological properties observed. It was concluded that high-shear blending brought about a nanoclay-reinforced network. As for the bitumen/Cloisite® 20A/polymeric MDI formulations, the solid-like behavior was destroyed as a result of the agglomeration of the nanoclay platelets promoted by chemical reactions.

Keywords: Atomic Force Microscopy, bitumen, composite, isocyanate, montmorillonite.

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8002 A Review on the Studies on Mechanical and Tribological Properties of Aluminum and Magnesium Alloys Welded by Friction Stir Welding

Authors: Sukhdeep Singh Gill, Gurbhinder Singh Brar

Abstract:

In recent years, friction stir welding (FSW) has attracted the main attention of the concerned researcher especially in case of joining of nonferrous alloys like aluminum and magnesium due to its unmatchable properties with respect to other welding techniques. Friction stir welding is a solid state welding process which is most suitable for the welding of nonferrous alloys, especially aluminum and magnesium alloys. Aluminum and magnesium alloys are widely used for structural applications of all types of automobiles due to their superior mechanical properties with their low density. This paper deals with the critical review of the different properties (like tensile strength, microhardness, impact strength, corrosion resistance, and metallurgical investigation on SEM) obtained by the FSW of aluminum and magnesium alloys. After a critical review of the existing published literature on concerned topics, all the properties of welding joins are compared in the tabulated manner to optimize the selection of materials and FSW parameters according to mechanical and tribological properties. Different tool designs used for the FSW process are also thoroughly studied, and the influence of the design of the tool used in FSW on the different properties has also been incorporated in this paper. It has been observed from the existing published literature that FSW is the most effective and practical technique for joining the non ferrous alloys especially aluminum and magnesium alloys, and among the different FSW tools, left hand threaded tri-flute (LHTTF) tool is best for the welding of non ferrous alloys like aluminum and magnesium alloys which gives the superior mechanical properties to welding joint.

Keywords: aluminum, friction stir welding, magnesium, structural applications, tool design

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