Search results for: earthquake resistant structural design

Authors: Heba Abdelmotaal, Magdy Abdel-Kader

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Purpose: This study explores whether a firm’s effective political risk management is preventing real and accrual earnings management . Design/methodology/approach: Based on a sample of 130 firms operating in Egypt during the period 2008-2013, two hypotheses are tested using the panel data regression models. Findings: The empirical findings indicate a significant relation between real and accrual earnings management and political risk. Originality/value: This paper provides a statistically evidence on the effects of the political risk management failure on the mangers’ engagement in the real and accrual earnings management practices, and its impact on the firm’s performance.

Keywords: political risk, risk management failure, real activities manipulation, accrual earnings management

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Authors: Timine Suoware, Sylvester Edelugo, Charles Amgbari

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Natural fibre composites (NFC) are becoming very attractive especially for automotive interior and non-structural building applications because they are biodegradable, low cost, lightweight and environmentally friendly. NFC are known to release high combustible products during exposure to heat atmosphere and this behaviour has raised concerns to end users. To improve on their fire response, flame retardants (FR) such as aluminium tri-hydroxide (ATH) and ammonium polyphosphate (APP) are incorporated during processing to delay the start and spread of fire. In this paper, APP was modified with Gum Arabic powder (GAP) and synergized with carbon black (CB) to form new FR species. Four FR species at 0, 12, 15 and 18% loading ratio were added to oil palm fibre polyester composite (OPFC) panels as follows; OPFC12%APP-GAP, OPFC15%APP-GAP/CB, OPFC18%ATH/APP-GAP and OPFC18%ATH/APPGAP/CB. The panels were produced using hand lay-up compression moulding and cured at room temperature. Specimens were cut from the panels and these were tested for ignition time (Tig), peak heat released rate (HRRp), average heat release rate (HRRavg), peak mass loss rate (MLRp), residual mass (Rm) and average smoke production rate (SPRavg) using cone calorimeter apparatus as well as the available flame energy (ɸ) in driving the flame using radiant panel flame spread apparatus. From the ignitability data obtained at 50 kW/m2 heat flux (HF), it shows that the hybrid FR modified with APP that is OPFC18%ATH/APP-GAP exhibited superior flame retardancy and the improvement was based on comparison with those without FR which stood at Tig = 20 s, HRRp = 86.6 kW/m2, HRRavg = 55.8 kW/m2, MLRp =0.131 g/s, Rm = 54.6% and SPRavg = 0.05 m2/s representing respectively 17.6%, 67.4%, 62.8%, 50.9%, 565% and 62.5% improvements less than those without FR (OPFC0%). In terms of flame spread, the least flame energy (ɸ) of 0.49 kW2/s3 for OPFC18%ATH/APP-GAP caused early flame regression. This was less than 39.6 kW2/s3 compared to those without FR (OPFC0%). It can be concluded that hybrid FR modified with APP could be useful in the automotive and building industries to delay the start and spread of fire.

Keywords: flame retardant, flame regression, oil palm fibre, composite panel

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Authors: Mohammad R. Rahim, Shagil Akhtar, Prem K. Bharti, Syed Muneeb Iqbal

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Deformation and energy absorption studies with corrugated tubes where corrugation is perpendicular to the line of action which coincides exactly with the unstrained axis of the tubes. In the present study, several specimens with various geometric parameters are prepared and compressed quasi-statistically in ANSYS Workbench. It is observed that tubes with perpendicular corrugation alters the deformation condition considerably and culminates in a substantial escalation in energy absorption scope in juxtaposed with the tubes having a circular cross-section. This study will help automotive, aerospace and various other industries to design superior components with perpendicular corrugated tubes and will reduce the experimental trials by conducting the numerical simulations.

Keywords: ANSYS Workbench, deformation and energy absorption, corrugated tubes, quasi-static compression

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Authors: Gi-Young Park, Dong Rak Kwon, Sung Cheol Cho

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Objective: The synovium is known to be involved in many pathological characteristic processes. Also, synovitis is common in advanced osteoarthritis. We aimed to evaluate the clinical, radiographic, and ultrasound findings in patients with knee osteoarthritis and to compare the clinical and imaging findings between knee osteoarthritis with and without synovial hypertrophy confirmed by ultrasound. Methods: One hundred knees (54 left, 46 right) in 95 patients (64 women, 31 men; mean age, 65.9 years; range, 43-85 years) with knee osteoarthritis were recruited. The Visual Analogue Scale (VAS) was used to assess the intensity of knee pain. The severity of knee osteoarthritis was classified according to Kellgren and Lawrence's (K-L) grade on a radiograph. Ultrasound examination was performed by a physiatrist who had 24 years of experience in musculoskeletal ultrasound. Ultrasound findings, including the thickness of joint effusion in the suprapatellar pouch, synovial hypertrophy, infrapatellar tendinosis, meniscal tear or extrusion, and Baker cyst, were measured and detected. The thickness of knee joint effusion was measured at the maximal anterior-posterior diameter of fluid collection in the suprapatellar pouch. Synovial hypertrophy was identified as the soft tissue of variable echogenicity, which is poorly compressible and nondisplaceable by compression of an ultrasound transducer. The knees were divided into two groups according to the presence of synovial hypertrophy. The differences in clinical and imaging findings between the two groups were evaluated by independent t-test and chi-square test. Results: Synovial hypertrophy was detected in 48 knees of 100 knees on ultrasound. There were no significant differences in demographic parameters and VAS score except in sex between the two groups (P<0.05). Medial meniscal extrusion and tear were significantly more frequent in knees with synovial hypertrophy than those in knees without synovial hypertrophy. K-L grade and joint effusion thickness were greater in patients with synovial hypertrophy than those in patients without synovial hypertrophy (P<0.05). Conclusion: Synovial hypertrophy in knee osteoarthritis was associated with greater suprapatellar joint effusion and higher K-L grade and maybe a characteristic ultrasound feature of late knee osteoarthritis. These results suggest that synovial hypertrophy on ultrasound can be regarded as a predictor of rapid progression in patients with knee osteoarthritis.

Keywords: knee osteoarthritis, synovial hypertrophy, ultrasound, K-L grade

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Authors: Xinyan Zhang, Zhipeng Tan, Shan Fan

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The first layer of defense against data loss is the backup data. This paper implements an agent-based network backup system used the backup, server-storage and server-backup agent these tripartite construction, and we realize the snapshot and hierarchical index in the NSBS. It realizes the control command and data flow separation, balances the system load, thereby improving the efficiency of the system backup and recovery. The test results show the agent-based network backup system can effectively improve the task-based concurrency, reasonably allocate network bandwidth, the system backup performance loss costs smaller and improves data recovery efficiency by 20%.

Keywords: agent, network backup system, three architecture model, NSBS

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Authors: Sandra Baez, Mariana Pino, Mildred Berrio, Hernando Santamaria-Garcia, Lucas Sedeno, Adolfo Garcia, Sol Fittipaldi, Agustin Ibanez

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Schadenfreude refers to the perceiver’s experience of pleasure at another’s misfortune. This is a multidetermined emotion which can be evoked by hostile feelings and envy. The experience of Schadenfreude engages mechanisms implicated in diverse social cognitive processes. For instance, Schadenfreude involves heightened reward processing, accompanied by increased striatal engagement and it interacts with mentalizing and perspective-taking abilities. Patients with Huntington's disease (HD) exhibit reductions of Schadenfreude experience, suggesting a role of striatal degeneration in such an impairment. However, no study has directly assessed the relationship between regional brain atrophy in HD and reduced Schadenfreude. This study investigated whether gray matter (GM) atrophy in HD patients correlates with ratings of Schadenfreude. First, we compared the performance of 20 HD patients and 23 controls on an experimental task designed to trigger Schadenfreude and envy (another social emotion acting as a control condition). Second, we compared GM volume between groups. Third, we examined brain regions where atrophy might be associated with specific impairments in the patients. Results showed that while both groups showed similar ratings of envy, HD patients reported lower Schadenfreude. The latter pattern was related to atrophy in regions of the reward system (ventral striatum) and the mentalizing network (precuneus and superior parietal lobule). Our results shed light on the intertwining of reward and socioemotional processes in Schadenfreude, while offering novel evidence about their neural correlates. In addition, our results open the door to future studies investigating social emotion processing in other clinical populations characterized by striatal or mentalizing network impairments (e.g., Parkinson’s disease, schizophrenia, autism spectrum disorders).

Keywords: envy, Gray matter atrophy, Huntigton's disease, Schadenfreude, social emotions

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Authors: Amir Ngah, Masita Abdul Jalil, Zailani Abdullah

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The aim of software maintenance is to maintain the software system in accordance with advancement in software and hardware technology. One of the early works on software maintenance is to extract information at higher level of abstraction. In this paper, we present the process of how to design an information extraction tool for software maintenance. The tool can extract the basic information from old program such as about variables, based classes, derived classes, objects of classes, and functions. The tool have two main part; the lexical analyzer module that can read the input file character by character, and the searching module which is user can get the basic information from existing program. We implemented this tool for a patterned sub-C++ language as an input file.

Keywords: extraction tool, software maintenance, reverse engineering, C++

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Authors: Sleman Yahya Rasul

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Due to their transparency, various types of glass are utilized in numerous applications where clear visibility is essential. One such application involves environments where radiography, radiotherapy, and X-ray devices are used, all of which involve exposure to radiation. As is well-known, radiation can be lethal to humans. Consequently, there is a need for glass that can absorb and block these harmful rays in such settings. Effective protection from radiation typically requires materials with high atomic numbers and densities. Currently, lead oxide-infused glasses are commonly used for this purpose, but due to the toxicity of lead oxide, there is a demand for safer alternatives. HfO2 has been selected as an additive for boro-tellurite (M1-M2-M3) glasses intended for radiation shielding because it has a high atomic number, high density, and is non-toxic. In this study, new glasses will be developed as alternatives to leaded glasses by incorporating x mol% HfO2 into the boro-tellurite glass structure. The glass compositions will be melted and quenched using the traditional method in an alumina crucible at temperatures between 900–1100°C. The resulting glasses will be evaluated for their elastic properties (including elastic modulus, shear modulus, bulk modulus, and Poisson ratio), density, hardness, and fracture toughness. X-ray diffraction (XRD) will be used to examine the amorphous nature of the glasses, while Differential Thermal Analysis (DTA) will provide thermal analysis. Optical properties will be assessed through UV-Vis and Photoluminescence Spectroscopy, and structural properties will be studied using Raman spectroscopy and FTIR spectroscopy. Additionally, the radiation shielding capabilities will be investigated by measuring parameters such as mass attenuation coefficient, half-value thickness, mean free path, effective atomic number (Z_eff), and effective electron density (N_e). The aim of this study is to develop new, lead-free glasses with excellent optical properties and high mechanical strength to replace the leaded glasses currently used for radiation shielding.

Keywords: boro-tellurite glasses, hfo2, radiation shielding, mechanical properties, elastic properties, optical properties

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Authors: Saraswati Suna

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The outbreak of the COVID-19 epidemic and the subsequent lockdown have significantly impacted India's political, structural, and economic systems and a rising gap between the rich and the disadvantaged, upper and lower caste. For Dalit women, such forms of subjugation were followed by socioeconomic uncertainty due to the pandemic's economic shutdown and labour oppressions. Dalit women have been the victims of the most oppression among the nation's underprivileged groups. Dalit women undergo systemic oppression at the hands of the state, caste, class, gender, and religious hegemons historically. Dalit women hold a subordinate position within the gender to their male counterparts and caste to their upper-caste counterparts. This paper examines how Brahminical patriarchy and state power severely affected Dalit/Adivasi women during COVID-19 in Odisha, India. In order to understand caste-based sexual violence, a total of five cases have been analysed from newspapers. Findings revealed that Covid-19 appears to have a significant physical, psychological, and economic impact on Dalit women. The intention of sexual harassment and rape perpetrated by upper caste men is to maintain power and patriarchal culture in society. Dalit women are economically, socially, and culturally marginalised, which effectively exacerbates the sense of impunity by perpetrators of violence against Dalit women. This issue requires special attention to end atrocities against Dalit women. Dalit women become the target of rape, sexual assault, and murder. Sexual violence against Dalit women cannot be fully explained without linkage to caste, gender, and power. Dominant caste comes through caste privilege-socio-economic and politically; these factors contribute to sexual violence against Dalit women. The findings revealed that state police manipulate sexual violence, and in so doing, they create and deny access to both services to get justice. This article has argued that understanding Brahminical culture and the legal impacts of state police on Dalit women's identity requires a nuanced analysis.

Keywords: COVID-19, dalit women, sexual violence, brahminical patriarchy, power

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Authors: S. Ghasemi, K. Khorasani

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In this paper, the problem of fault detection and isolation in the attitude control subsystem of spacecraft formation flying is considered. In order to design the fault detection method, an extended Kalman filter is utilized which is a nonlinear stochastic state estimation method. Three fault detection architectures, namely, centralized, decentralized, and semi-decentralized are designed based on the extended Kalman filters. Moreover, the residual generation and threshold selection techniques are proposed for these architectures.

Keywords: component, formation flight of satellites, extended Kalman filter, fault detection and isolation, actuator fault

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Authors: Anwar Jarndal

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In this paper, a genetic-neural-network (GNN) based large-signal model for GaN HEMTs is presented along with its parameters extraction procedure. The model is easy to construct and implement in CAD software and requires only DC and S-parameter measurements. An improved decomposition technique is used to model self-heating effect. Two GNN models are constructed to simulate isothermal drain current and power dissipation, respectively. The two model are then composed to simulate the drain current. The modeling procedure was applied to a packaged GaN-on-Si HEMT and the developed model is validated by comparing its large-signal simulation with measured data. A very good agreement between the simulation and measurement is obtained.

Keywords: GaN HEMT, computer-aided design and modeling, neural networks, genetic optimization

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Authors: Hamida Qumber Ali, Waseem Muhammad Arain, Shama Siddiqui, Sayeed Ghani

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We present an implementing of RMAC in TinyOS 1.x. RMAC is a cross layer and Duty-cycle MAC protocols that was proposed to provide energy efficient transmission services for wireless sensor networks. The protocol has a unique and efficient packet transmission scheduling mechanism that enables it to overcome delivery latency and overcome traffic congestion. Design details and implementation challenges are divulged. Experiments are conducted to show the correctness of our implementation with numerous assumptions. Simulations are performed to compare the performance of RMAC and SMAC. Our results show that RMAC outperforms SMAC in energy efficiency and delay.

Keywords: MAC protocol, performance, RMAC, wireless sensor networks

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Authors: M. Chen, S-Q. Zhang, X. Wang, D. Tate

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This paper presents a numerical solution, namely limit and shakedown analysis, to predict the safety state of smart structures made of heterogeneous materials under unknown cyclic loadings, for instance, the flexure hinge in the micro-positioning stage driven by piezoelectric actuator. In combination of homogenization theory and finite-element method (FEM), the safety evaluation problem is converted to a large-scale nonlinear optimization programming for an acceptable bounded loading as the design reference. Furthermore, a general numerical scheme integrated with the FEM and interior-point-algorithm based optimization tool is developed, which makes the practical application possible.

Keywords: limit state, shakedown analysis, homogenization, heterogeneous structure

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Authors: P. Kavuma, J. Mukasa, M. Lusunku

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Background and Problem: The widespread poverty in Africa- together with the negative impacts of climate change-are two great global challenges that call for everyone’s involvement including Architects. This in particular places serious challenges on architects to have additional skills in both Entrepreneurship and Environmental Design (SEED). Regrettably, while Architectural Training in most African Universities including those from Uganda lack comprehensive implementation of SEED in their curricula, regulatory bodies have not contributed towards the effective integration of SEED in their professional practice. In response to these challenges, Nkumba University (NU) under Architect Kavuma Paul supported by the Uganda Chambers of Architects– initiated the SEED integration in the undergraduate Architectural curricula to cultivate SEED know-how and examples of best practices. Main activities: Initiated in 2007, going beyond the traditional Architectural degree curriculum, the NU Architect department offers SEED courses including provoking passions for creating desirable positive changes in communities. Learning outcomes are assessed theoretically and practically through field projects. The first set of SEED graduates came out in 2012. As part of the NU post-graduation and alumni survey, in October 2014, the pioneer SEED graduates were contacted through automated reminder emails followed by individual, repeated personal follow-ups via email and phone. Out of the 36 graduates who responded to the survey, 24 have formed four (4) private consortium agencies of 5-7 graduates all of whom have pioneered Ugandan-own-cultivated Architectural social projects that include: fishing farming in shipping containers; solar powered mobile homes in shipping containers, solar powered retail kiosks in rural and fishing communities, and floating homes in the flood-prone areas. Primary outcomes: include being business self –reliant in creating the social change the architects desired in the communities. Examples of the SEED project returns to communities reported by the graduates include; employment creation via fabrication, retail business, marketing, improved diets, safety of life and property, decent shelter in the remote mining and oil exploration areas. Negative outcomes-though not yet evaluated include the disposal of used-up materials. Conclusion: The integration of SEED in Architectural Training has established a baseline benchmark and a replicable model based on best practice projects.

Keywords: architectural training, entrepreneurship, environment, integration

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Authors: Armando A. Rodríguez, Emilio Salceda, Anoland Garateix, André J. Zaharenko, Steve Peigneur, Omar López, Tirso Pons, Michael Richardson, Maylín Díaz, Yasnay Hernández, Ludger Ständker, Jan Tytgat, Enrique Soto

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Acid-sensing ion channels are cation (Na+) channels activated by a pH drop. These proteins belong to the ENaC/degenerin superfamily of sodium channels. ASICs are involved in sensory perception, synaptic plasticity, learning, memory formation, cell migration and proliferation, nociception, and neurodegenerative disorders, among other processes; therefore those molecules that specifically target these channels are of growing pharmacological and biomedical interest. Sea anemones produce a large variety of ion channels peptide toxins; however, those acting on ligand-gated ion channels, such as Glu-gated, Ach-gated ion channels, and acid-sensing ion channels (ASICs), remain barely explored. The peptide PhcrTx1 is the first compound characterized from the sea anemone Phymanthus crucifer, and it constitutes a novel ASIC inhibitor. This peptide was purified by chromatographic techniques and pharmacologically characterized on acid-sensing ion channels of mammalian neurons using patch-clamp techniques. PhcrTx1 inhibited ASIC currents with an IC50 of 100 nM. Edman degradation yielded a sequence of 32 amino acids residues, with a molecular mass of 3477 Da by MALDI-TOF. No similarity to known sea anemone peptides was found in protein databases. The computational analysis of Cys-pattern and secondary structure arrangement suggested that this is a structurally ICK (Inhibitor Cystine Knot)-type peptide, a scaffold that had not been found in sea anemones but in other venomous organisms. These results show that PhcrTx1 represents the first member of a new structural group of sea anemones toxins acting on ASICs. Also, this peptide constitutes a novel template for the development of drugs against pathologies related to ASICs function.

Keywords: animal toxin, inhibitor cystine knot, ion channel, sea anemone

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Authors: Sumanta Das, Miroslav Gašparík, Tomáš Kytka, Anil Kumar Sethy

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In this modern century, Cross-laminated timber (CLT) evolved as an excellent material for building and high load-bearing structural applications worldwide. CLT is produced mainly from softwoods such as Norway spruce, White fir, Scots pine, European larch, Douglas fir, and Swiss stone pine. The use of hardwoods in CLT production is still at an early stage, and the utilization of hardwoods is expected to provide the opportunity for obtaining higher bending stiffness and shear resistance to CLT panels. In load-bearing structures like CLT, bonding is an important character that is needed to evaluate. One particular issue with using hardwood lumber in CLT panels is that it is often more challenging to achieve a strong, durable adhesive bond. Several researches in the past years have already evaluated the bonding properties of CLT panels from hardwood both from higher and lower densities. This research aims to identify the effect of pressure and glue spread and evaluate which poplar lumber characteristics affect adhesive bond quality. Three-layered CLT panels were prepared from poplar wood with one-component polyurethane (PUR) adhesive by applying pressure of 0.6 N/mm2 and 1 N/mm2 with a glue spread rate of 160 and 180 g/m2. The delamination and block shear tests were carried out as per EN 16351:2015, and the wood failure percentage was also evaluated. The results revealed that glue spread rate and applied pressure significantly influenced both the shear bond strength and wood failure percentage of the CLT. However, samples with lower pressure 0.6 N/mm2 and less glue spread rate showed delamination, and in samples with higher pressure 1 N/mm2 and higher glue spread rate, no delamination was observed. All the properties determined by this study met the minimum requirement mentioned in EN 16351:2015 standard.

Keywords: cross-laminated timber, delamination, glue spread rate, poplar, pressure, PUR, shear strength, wood failure percentage

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Authors: Jezza Mae T. Francisco, Marianet R. Delos Santos, Crisjame C. Toribio

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This study aims to determine the reading preference for English enrichment and reading comprehension among primary students and the difference in the reading preference and comprehension for English enrichment among primary students. This study employed a Descriptive-Quantitative Correlational Research Design. This study yielded the following findings: (1) It reveals that primary students got fair on their reading comprehension, and (2) It shows that there is no significant relationship between the reading preference for English enrichment and reading comprehension of the students. It is safe to conclude that the students’ reading preference is growing evidently in various milieus. This can inform the English department curriculum planners to consider their students’ text preferences that interest them to maximize engagement within a dynamic interactive learning process.

Keywords: reading preferences, reading comprehension, primary student, English enrichment

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Authors: Younghyun Jeon, Seungjoo Maeng

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In the Ad-hoc network, the great interests regarding MIMO scheme leads to their combination, which is also utilized into its applicable network. We manage the field of the problem into Reverse-link MIMO Ad-hoc Network (RMAN) and propose the methodology to maximize the data rate with its power consumption using Node-Cooperative beamforming technique. Based on the result of mathematical optimization formulation, we design the algorithm to construct optimal orthogonal weight vector according to channel feedback and control its transmission power according to QoS-pricing value level. In simulation results, we show the validity of the proposed mathematical optimization result and algorithm which mean that the sum-rate of each link is converged into some point.

Keywords: ad-hoc network, MIMO, cooperative beamforming, transmit power

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Authors: S. Arun Prakash, V. Malathi, M. S. Mani Rajan

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The analytical bright two soliton solution of the 3-coupled nonlinear Schrödinger equations with variable coefficients in birefringent optical fiber is obtained by Darboux transformation method. To the design of ultra-speed optical devices, Soliton interaction and control in birefringence fiber is investigated. Lax pair is constructed for N coupled NLS system through AKNS method. Using two soliton solution, we demonstrate different interaction behaviors of solitons in birefringent fiber depending on the choice of control parameters. Our results shows that interactions of optical solitons have some specific applications such as construction of logic gates, optical computing, soliton switching, and soliton amplification in wavelength division multiplexing (WDM) system.

Keywords: optical soliton, soliton interaction, soliton switching, WDM

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Authors: Farouk Lawan Gambo, Hamada Mohammad

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Data compression shrinks files into fewer bits than their original presentation. It has more advantage on the internet because the smaller a file, the faster it can be transferred but learning most of the concepts in data compression are abstract in nature, therefore, making them difficult to digest by some students (engineers in particular). This paper studies the learning preference of engineering students who tend to have strong, active, sensing, visual and sequential learning preferences, the paper also studies the three shift of technology-aided that learning has experienced, which mobile learning has been considered to be the feature of learning that will integrate other form of the education process. Lastly, we propose a design and implementation of mobile learning application using software engineering methodology that will enhance the traditional teaching and learning of data compression techniques.

Keywords: data compression, learning preference, mobile learning, multimedia

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Authors: Kristina Pflug, Markus Busch

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Being able to predict polymer properties and processing behavior based on the applied operating reaction conditions in one of the key challenges in modern polymer reaction engineering. Especially, for cost-intensive processes such as the high-pressure polymerization of low-density polyethylene (LDPE) with high safety-requirements, the need for simulation-based process optimization and product design is high. A multi-scale modelling approach was set-up and validated via a series of high-pressure mini-plant autoclave reactor experiments. The approach starts with the numerical modelling of the complex reaction network of the LDPE polymerization taking into consideration the actual reaction conditions. While this gives average product properties, the complex polymeric microstructure including random short- and long-chain branching is calculated via a hybrid Monte Carlo-approach. Finally, the processing behavior of LDPE -its melt flow behavior- is determined in dependence of the previously determined polymeric microstructure using the branch on branch algorithm for randomly branched polymer systems. All three steps of the multi-scale modelling approach can be independently validated against analytical data. A triple-detector GPC containing an IR, viscosimetry and multi-angle light scattering detector is applied. It serves to determine molecular weight distributions as well as chain-length dependent short- and long-chain branching frequencies. 13C-NMR measurements give average branching frequencies, and rheological measurements in shear and extension serve to characterize the polymeric flow behavior. The accordance of experimental and modelled results was found to be extraordinary, especially taking into consideration that the applied multi-scale modelling approach does not contain parameter fitting of the data. This validates the suggested approach and proves its universality at the same time. In the next step, the modelling approach can be applied to other reactor types, such as tubular reactors or industrial scale. Moreover, sensitivity analysis for systematically varying process conditions is easily feasible. The developed multi-scale modelling approach finally gives the opportunity to predict and design LDPE processing behavior simply based on process conditions such as feed streams and inlet temperatures and pressures.

Keywords: low-density polyethylene, multi-scale modelling, polymer properties, reaction engineering, rheology

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Authors: Syrine lahmadi, Jamel Bel Hadj Tahar

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In this paper, a rectangular antenna with slots integrated on silicon substrate operating in 60GHz, is studied and optimized. The effect of different parameter of the antenna (width, length, the position of the microstrip-feed line...) and the parameter of the substrate (the thickness, the dielectric constant) on gain, frequency is presented. Also, the paper presents a solution to ameliorate the bandwidth. The maximum simulated radiation gain of this rectangular dual band antenna is 5, 38 dB around 60GHz. The simulation studied id developed based on advanced design system tools. It is found that the designed antenna is 19 % smaller than a rectangular antenna with the same dimensions. This antenna with dual band can function for many communication systems as automobile or radar.

Keywords: dual band, enlargement of bandwidth, miniaturized antennas, printed antenna

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Authors: Lorena C. Cintra, Izadora M. De Oliveira, Amanda G. Fernandes, Francieli Colussi, Rosália S. A. Jesuíno, Fabrícia P. Faria, Cirano J. Ulhoa

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Xylan is the main component of hemicellulose and for its complete degradation is required cooperative action of a system consisting of several enzymes including endo-xylanases (XYN), β-xylosidases (XYL) and α-L-arabinofuranosidases (ABF). The recombinant hemicellulolytic enzymes an endoxylanase (HXYN2), β-xylosidase (HXYLA), and an α-L-arabinofuranosidase (ABF3) were used in hydrolysis tests. These three enzymes are produced by filamentous fungi and were expressed heterologously and produced in Pichia pastoris previously. The aim of this work was to evaluate the effect of recombinant hemicellulolytic enzymes on the enzymatic hydrolysis of sugarcane bagasse (SCB). The interaction between the three recombinant enzymes during SCB pre-treated by steam explosion hydrolysis was performed with different concentrations of HXYN2, HXYLA and ABF3 in different ratios in according to a central composite rotational design (CCRD) 23, including six axial points and six central points, totaling 20 assays. The influence of the factors was assessed by analyzing the main effects and interaction between the factors, calculated using Statistica 8.0 software (StatSoft Inc. Tulsa, OK, USA). The Pareto chart was constructed with this software and showed the values of the Student’s t test for each recombinant enzyme. It was considered as response variable the quantification of reducing sugars by DNS (mg/mL). The Pareto chart showed that the recombinant enzyme ABF3 exerted more significant effect during SCB hydrolysis, with higher concentrations and with the lowest concentration of this enzyme. It was performed analysis of variance according to Fisher method (ANOVA). In ANOVA for the release of reducing sugars (mg/ml) as the variable response, the concentration of ABF3 showed significance during hydrolysis SCB. The result obtained by ANOVA, is in accordance with those presented in the analysis method based on the statistical Student's t (Pareto chart). The degradation of the central chain of xylan by HXYN2 and HXYLA was more strongly influenced by ABF3 action. A model was obtained, and it describes the performance of the interaction of all three enzymes for the release of reducing sugars, and can be used to better explain the results of the statistical analysis. The formulation capable of releasing the higher levels of reducing sugars had the following concentrations: HXYN2 with 600 U/g of substrate, HXYLA with 11.5 U.g-1 and ABF3 with 0.32 U.g-1. In conclusion, the recombinant enzyme that has a more significant effect during SCB hydrolysis was ABF3. It is noteworthy that the xylan present in the SCB is arabinoglucoronoxylan, due to this fact debranching enzymes are important to allow access of enzymes that act on the central chain.

Keywords: experimental design, hydrolysis, recombinant enzymes, sugar cane bagasse

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Authors: M. S. Nandana, K. Udaya Bhat, C. M. Manjunatha

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In this study aluminum alloy 7010 was subjected to three different ageing treatments i.e., peak ageing (T6), over-ageing (T7451) and retrogression and re ageing (RRA) to study the influence of precipitate microstructure on the fatigue crack growth rate behavior. The microstructural modification was studied by using transmission electron microscope (TEM) to examine the change in the size and morphology of precipitates in the matrix and on the grain boundaries. The standard compact tension (CT) specimens were fabricated and tested under constant amplitude fatigue crack growth tests to evaluate the influence of heat treatment on the fatigue crack growth rate properties. The tests were performed in a computer-controlled servo-hydraulic test machine applying a load ratio, R = 0.1 at a loading frequency of 10 Hz as per ASTM E647. The fatigue crack growth was measured by adopting compliance technique using a CMOD gauge attached to the CT specimen. The average size of the matrix precipitates were found to be of 16-20 nm in T7451, 5-6 nm in RRA and 2-3 nm in T6 conditions respectively. The grain boundary precipitate which was continuous in T6, was disintegrated in RRA and T7451 condition. The PFZ width was lower in RRA compared to T7451 condition. The crack growth rate was higher in T7451 and lowest in RRA treated alloy. The RRA treated alloy also exhibits an increase in threshold stress intensity factor range (∆Kₜₕ). The ∆Kₜₕ measured was 11.1, 10.3 and 5.7 MPam¹/² in RRA, T6 and T7451 alloys respectively. The fatigue crack growth rate in RRA treated alloy was nearly 2-3 times lower than that in T6 and was one order lower than that observed in T7451 condition. The surface roughness of RRA treated alloy was more pronounced when compared to the other conditions. The reduction in fatigue crack growth rate in RRA alloy was majorly due to the increase in roughness and partially due to increase in spacing between the matrix precipitates. The reduction in crack growth rate and increase in threshold stress intensity range is expected to benefit the damage tolerant capability of aircraft structural components under service loads.

Keywords: damage tolerance, fatigue, heat treatment, PFZ, RRA

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Authors: M. Lobzhanidze, N. Damenia

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The article analyzes the current structural changes in the economy of Georgia, liberalization and integration processes of the economy. In accordance with this analysis, the peculiarities and the problems of youth employment are revealed. In the paper, the Georgian labor market and its contradictions are studied. Based on the analysis of materials, the socio-economic losses caused by the long-term and mass unemployment of young people are revealed, the objective and subjective circumstances of getting higher education are studied. The youth employment and unemployment rates are analyzed. Based on the research, the factors that increase unemployment are identified. According to the analysis of the youth employment, it has appeared that the unemployment share in the number of economically active population has increased in the younger age group. It demonstrates the high requirements of the labour market in terms of the quality of the workforce. Also, it is highlighted that young people are exposed to a highly paid job. The following research methods are applied in the presented paper: statistical (selection, grouping, observation, trend, etc.) and qualitative research (in-depth interview), as well as analysis, induction and comparison methods. The article presents the data by the National Statistics Office of Georgia and the Ministry of Agriculture of Georgia, policy documents of the Parliament of Georgia, scientific papers by Georgian and foreign scientists, analytical reports, publications and EU research materials on similar issues. The work estimates the students and graduates employment problems existing in the state development strategy and priorities. The measures to overcome the challenges are defined. The article describes the mechanisms of state regulation of youth employment and the ways of improving this regulatory base. As for major findings, it should be highlighted that the main problems are: lack of experience and incompatibility of youth qualification with the requirements of the labor market. Accordingly, it is concluded that the unemployment rate of young people in Georgia is increasing.

Keywords: migration of youth, youth employment, migration management, youth employment and unemployment

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Authors: Martin Hagan

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Teacher identity has been recognised as a crucial field of research which supports understanding of the ways in which teachers navigate the complexities of professional life in order to grow in competence, knowledge and practice. As a field of study, teacher identity is concerned with understanding: how identity is defined; how it develops; how teachers make sense of their emerging identity; and how the act of teaching is mediated through the individual teacher’s values, beliefs and sense of professional self. By comparing two particular, socially constructed learning contexts or ‘learning milieu’, one in Northern Ireland and the other in the United States of America, this study aims specifically, to gain better understanding of how teacher identity develops during the initial phase of teacher education. The comparative approach was adopted on the premise that experiences are constructed through interactive, socio-historical and cultural negotiations with others within particular environments, situations and contexts. As such, whilst the common goal is to ‘become’ a teacher, the nuances emerging from the different learning milieu highlight variance in discourse, priorities, practice and influence. A qualitative, interpretative research design was employed to understand the world-constructions of the participants through asking open-ended questions, seeking views and perspectives, examining contexts and eventually deducing meaning. Data were collected using semi structured interviews from a purposive sample of student teachers (n14) in either the first or second year of study in their respective institutions. In addition, a sample of teacher educators (n5) responsible for the design, organisation and management of the programmes were also interviewed. Inductive thematic analysis was then conducted, which highlighted issues related to: the participants’ personal dispositions, prior learning experiences and motivation; the influence of the teacher education programme on the participants’ emerging professional identity; and the extent to which the experiences of working with teachers and pupils in schools in the context of the practicum, challenged and changed perspectives on teaching as a professional activity. The study also highlights the varying degrees of influence exercised by the different roles (tutor, host teacher/mentor, student) within the teacher-learning process across the two contexts. The findings of the study contribute to the understanding of teacher identity development in the early stages of professional learning. By so doing, the research makes a valid contribution to the discourse on initial teacher preparation and can help to better inform teacher educators and policy makers in relation to appropriate strategies, approaches and programmes to support professional learning and positive teacher identity formation.

Keywords: initial teacher education, professional learning, professional growth, teacher identity

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Authors: Shing-Cheng Chang, Cheng-Hao Yang, Wen-Sheng Chang, Chih-Chia Lin, Chun-Han Li

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The solid oxide fuel cell (SOFC) is a promising green technology which can achieve a high electrical efficiency. Due to the high operating temperature of SOFC stack, the off-gases at high temperature from anode and cathode outlets are introduced into an afterburner to convert the chemical energy into thermal energy by combustion. The heat is recovered to preheat the fresh air and fuel gases before they pass through the stack during the SOFC power generation system operation. For an afterburner of the SOFC system, the temperature control with a good thermal uniformity is important. A burner with a well-designed geometry usually can achieve a satisfactory performance. To design an afterburner for an SOFC system, the computational fluid dynamics (CFD) simulation is adoptable. In this paper, the hydrogen combustion characteristics in an afterburner with simple geometry are studied by using CFD. The burner is constructed by a cylinder chamber with the configuration of a fuel gas inlet, an air inlet, and an exhaust outlet. The flow field and temperature distributions inside the afterburner under different fuel and air flow rates are analyzed. To improve the temperature uniformity of the afterburner during the SOFC system operation, the flow paths of anode/cathode off-gases are varied by changing the positions of fuels and air inlet channel to improve the heat and flow field synergy in the burner furnace. Because the air flow rate is much larger than the fuel gas, the flow structure and heat transfer in the afterburner is dominated by the air flow path. The present work studied the effects of fluid flow structures on the combustion characteristics of an SOFC afterburner by three simulation models with a cylindrical combustion chamber and a tapered outlet. All walls in the afterburner are assumed to be no-slip and adiabatic. In each case, two set of parameters are simulated to study the transport phenomena of hydrogen combustion. The equivalence ratios are in the range of 0.08 to 0.1. Finally, the pattern factor for the simulation cases is calculated to investigate the effect of gas inlet locations on the temperature uniformity of the SOFC afterburner. The results show that the temperature uniformity of the exhaust gas can be improved by simply adjusting the position of the gas inlet. The field synergy analysis indicates the design of the fluid flow paths should be in the way that can significantly contribute to the heat transfer, i.e. the field synergy angle should be as small as possible. In the study cases, the averaged synergy angle of the burner is about 85̊, 84̊, and 81̊ respectively.

Keywords: afterburner, combustion, field synergy, solid oxide fuel cell

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Authors: Charu Sharma

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San Francisco Public Utilities Commission’s Headquarters was listed in the 2013-American Institute of Architects Committee of the Environment (AIA COTE) Top Ten Green Projects. This 13-story, 277,000-square-foot building, housing more than 900 of the agency’s employees was completed in June 2012. It was designed to achieve LEED Platinum Certification and boasts a plethora of green features to significantly reduce the use of energy and water consumption, and provide a healthy office work environment with high interior air quality and natural daylight. Key sustainability features include on-site clean energy generation through renewable photovoltaic and wind sources providing $118 million in energy cost savings over 75 years; 45 percent daylight harvesting; and the consumption of 55 percent less energy and a 32 percent less electricity demand from the main power grid. It uses 60 percent less water usage than an average 13-story office building as most of that water will be recycled for non-potable uses at the site, running through a system of underground tanks and artificial wetlands that cleans and clarifies whatever is flushed down toilets or washed down drains. This is one of the first buildings in the nation with treatment of gray and black water. The building utilizes an innovative structural system with post tensioned cores that will provide the highest asset preservation for the building. In addition, the building uses a “green” concrete mixture that releases less carbon gases. As a public utility commission this building has set a good example for resource conservation-the building is expected to be cheaper to operate and maintain as time goes on and will have saved rate-payers $500 million in energy and water savings. Within the anticipated 100-year lifespan of the building, our ratepayers will save approximately $3.7 billion through the combination of rental savings, energy efficiencies, and asset ownership.

Keywords: energy efficiency, sustainability, resource conservation, asset ownership, rental savings

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Authors: Henry Okechukwu Onyeiwu, Arfah Ab. Majid

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To fully understand the critical role of marriage in society, it is important to view it as a social institution that provides some basic social needs for society. A ‘social institution’ is the network of shared meanings, norms, definitions, expectations, and understandings held by the members of society. It is what guides and governs how the members of the society are expected to act and interact, what is socially desirable and legitimate, what they should be striving for, and so on. One of the major social institutions is marriage. Marriage is and has often focused on children and what is best for them because the rising generation literally is the future of every society. However, according to the aforementioned definition, which notes that marriage may also be a union between two persons of the same sex with legal support, this study stands with the definitions that are based on marriage being a union between a man and woman that is the most appropriate in Igbo land and not the other way round. The issue to be evaluated concerns marriage as it associates with Igbo Catholic Christians in Nigeria. Pasts of Igbo culture should be better organized into the Christian faith. Igbo Christians actually convey a significant number of their customary thoughts, customs, and social qualities, particularly regarding marriage, in the aftermath of switching to Christianity. The analyst agrees that marriage among Igbo Christians warrants adequate evolution. This study, therefore, concentrates on the Igbo community’s interpretation of the concept of culture and religion and the religious implications of traditional marriage and Christian marriage ceremonies in Igbo. The research design of this study is a qualitative design that provides in-depth information on the dual religious identity of the Igbo people on the rite of marriage in Imo state. The study population was composed of both male and female members from each selected local government area in Imo State. Thematic analysis was used to elaborate on the result from the respondents. This survey found that reputation is a major concern for Ibo people. Parental discomfort can lead to the use of coping strategies such as displacement, in which parents pass on their own vulnerable sentiments to their children. Those who participate in marriage negotiations feel the pain of their parents because they are unable to communicate their own feelings. As a result, participants experience increased stress and a range of negative emotions related to their marriage, including worry, dissatisfaction, and ambivalence. It was concluded that when it comes to Igbo culture, marriage is seen as a need for the continuation of the family’s lineage of descent, according to the outcome. The Task at hand was to discover how the locals preparing to get married define the impending transition. Imo State is home to the practice of Igba-nkwu, where the woman is either inherited or taken in the place of another.

Keywords: Igbo, culture, Christianity, traditional marriage, Christian wedding

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Authors: Guerich Mohamed, Assaf Samir

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The application of viscoelastic materials in the form of constrained layers in mechanical structures is an efficient and cost-effective technique for solving noise and vibration problems. This technique requires a design tool to select the best location, type, and thickness of the damping treatment. This paper presents a finite element model for the vibration of beams partially or fully covered with a constrained viscoelastic damping material. The model is based on Bernoulli-Euler theory for the faces and Timoshenko beam theory for the core. It uses four variables: the through-thickness constant deflection, the axial displacements of the faces, and the bending rotation of the beam. The sandwich beam finite element is compatible with the conventional C1 finite element for homogenous beams. To validate the proposed model, several free vibration analyses of fully or partially covered beams, with different locations of the damping patches and different percent coverage, are studied. The results show that the proposed approach can be used as an effective tool to study the influence of the location and treatment size on the natural frequencies and the associated modal loss factors. Then, a parametric study regarding the variation in the damping characteristics of partially covered beams has been conducted. In these studies, the effect of core shear modulus value, the effect of patch size variation, the thickness of constraining layer, and the core and the locations of the patches are considered. In partial coverage, the spatial distribution of additive damping by using viscoelastic material is as important as the thickness and material properties of the viscoelastic layer and the constraining layer. Indeed, to limit added mass and to attain maximum damping, the damping patches should be placed at optimum locations. These locations are often selected using the modal strain energy indicator. Following this approach, the damping patches are applied over regions of the base structure with the highest modal strain energy to target specific modes of vibration. In the present study, a more efficient indicator is proposed, which consists of placing the damping patches over regions of high energy dissipation through the viscoelastic layer of the fully covered sandwich beam. The presented approach is used in an optimization method to select the best location for the damping patches as well as the material thicknesses and material properties of the layers that will yield optimal damping with the minimum area of coverage.

Keywords: finite element model, damping treatment, viscoelastic materials, sandwich beam

Procedia PDF Downloads 136