Search results for: finite state method

Authors: R. Nasrin, M. Ferdows

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Among the renewable energy sources, photovoltaic (PV) is a high potential, effective, and sustainable system. Irradiation intensity from 200 W/m2 to 1000 W/m2 has been considered to observe the performance of PV module. Generally, this module converts only about 15% - 20% of incident irradiation into electrical energy and the rest part is converted into heat energy. Finite element method has been used to solve the problem numerically. Simulation has been performed by considering the ambient temperature 30°C. Higher irradiation increase solar cell temperature and electrical power. The electrical efficiency of PV module decreases with the variation of solar radiation. The efficiency of PV module can be increased if cell temperature is reduced. Thus the effect of irradiation is significant to enhance the efficiency of PV module if the solar cell temperature is kept at a certain level.

Keywords: PV module, solar radiation, efficiency, cell temperature

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Authors: Marilou Cadatal-Raduban, Minh Hong Pham, Duong Van Pham, Tu Nguyen Xuan, Mui Viet Luong, Kohei Yamanoi, Toshihiko Shimizu, Nobuhiko Sarukura, Hung Dai Nguyen

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There is a great deal of interest in developing all-solid-state tunable ultrashort pulsed lasers emitting in the ultraviolet (UV) region for applications such as micromachining, investigation of charge carrier relaxation in conductors, and probing of ultrafast chemical processes. However, direct short-pulse generation is not as straight forward in solid-state gain media as it is for near-IR tunable solid-state lasers such as Ti:sapphire due to the difficulty of obtaining continuous wave laser operation, which is required for Kerr lens mode-locking schemes utilizing spatial or temporal Kerr type nonlinearity. In this work, the transient cavity method, which was reported to generate ultrashort laser pulses in dye lasers, is extended to a solid-state gain medium. Ce:LiCAF was chosen among the rare-earth-doped fluoride laser crystals emitting in the UV region because of its broad tunability (from 280 to 325 nm) and enough bandwidth to generate 3-fs pulses, sufficiently large effective gain cross section (6.0 x10⁻¹⁸ cm²) favorable for oscillators, and a high saturation fluence (115 mJ/cm²). Numerical simulations are performed to investigate the spectro-temporal evolution of the broadband UV laser emission from Ce:LiCAF, represented as a system of two homogeneous broadened singlet states, by solving the rate equations extended to multiple wavelengths. The goal is to find the appropriate cavity length and Q-factor to achieve the optimal photon cavity decay time and pumping energy for resonator transients that will lead to ps UV laser emission from a Ce:LiCAF crystal pumped by the fourth harmonics (266nm) of a Nd:YAG laser. Results show that a single ps pulse can be generated from a 1-mm, 1 mol% Ce³⁺-doped LiCAF crystal using an output coupler with 10% reflectivity (low-Q) and an oscillator cavity that is 2-mm long (short cavity). This technique can be extended to other fluoride-based solid-state laser gain media.

Keywords: rare-earth-doped fluoride gain medium, transient cavity, ultrashort laser, ultraviolet laser

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Authors: Rishabh Agrawal, S. C. Kaushik, T. S. Bhatti

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In order to reduce energy consumption for sustainable development, continuous energy consumption tracking of building energy systems are essential. In this paper an assessment study has been done to identify the energy consumption & energy conservation potential for commercial buildings sector in Karnataka state, India. There are a total of 326 commercial buildings in the state of Karnataka who has qualified as designated consumers (i.e., having a Contract Demand ≥ 600 KVA), was consider for the study. It has estimated that the annual electricity sale to commercial sector is 3.62 Billion Units (BU) in alone Karnataka State, India, which is an account for 9.57 % of the total electricity sold. The commercial sector constitutes Government & private establishments, hospitals, hotels, restaurants, educational institutions, malls etc. Total 326 commercial buildings in the state accounting for annual energy consumption of 1295.72 Million Units (MU) which works out to about 35% of the sectoral consumption. The annual energy savings potential for 326 commercial buildings is assessed to be 0.25 BU.

Keywords: commercial buildings, connected load, energy conservation studies, energy savings, energy efficiency, energy conservation strategy, energy efficiency, thermal energy, HVAC system

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Authors: Can Yao, Chang Dong Sheng

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The heat released by wood pellets during storage will cause self-heating and even self-ignition. In this work, the heat release rates of pine, fir wood and mahogany pellets at 30–70℃ were measured by TAM air isothermal calorimeter, and the kinetic analysis was performed by iso-conversion ratio and non-steady-state methods to evaluate its self-heating potential. The results show that the reaction temperature can significantly affect the heat release rate. The higher the temperature, the greater the heat release rate. The heat release rates of different kinds of wood pellets are obviously different, and the order of the heat release rates for the three pellets at 70℃ is pine > fir wood > mahogany. The kinetic analysis of the iso-conversion ratio method indicates that the distribution of activation energy for pine, fir wood and mahogany pellets under the release of 0.1–1.0 J/g specific heat are 58–102 kJ/mol, 59–108 kJ/mol and 59–112 kJ/mol, respectively. Their activation energies obtained from the non-steady-state kinetic analysis are 13.43 kJ/mol, 19.19 kJ/mol and 21.09 kJ/mol, respectively. Both kinetic analyses show that the magnitude of self-heating risk for the three pellet fuels is pine pellets > fir wood pellets > mahogany pellets.

Keywords: isothermal calorimeter, kinetics, self-heating, wood pellets

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Authors: Deenadayalan Govender

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In South Africa, similar to nations globally, the prevailing tangible link between people and the state is public infrastructure. Services delivered through infrastructure to the people and to the state form a critical enabler for social development in communities and economic development in the country. In this regard, infrastructure, being the backbone to a nation’s prosperity, ideally should be effectively maintained for seamless delivery of services. South African infrastructure is in a state of deterioration, which is leading to infrastructure dysfunction and collapse and is negatively affecting development of the economy. This infrastructure deterioration stems from deficiencies in maintenance practices and strategies. From the birth of South African democracy, government has pursued socio-economic transformation and the delivery of critical basic services to decrease the broadening boundaries of disparity. In this regard, the National Infrastructure Plan borne from strategies encompassed in the National Development Plan is given priority by government in delivering strategic catalytic infrastructure projects. The National Infrastructure Plan is perceived to be the key in unlocking opportunities that generate economic growth, kerb joblessness, alleviate poverty, create new entrepreneurial prospects, and mitigate population expansion and rapid urbanisation. Socio-economic transformation benefits from new infrastructure spend is not being realised as initially anticipated. In this context, South Africa is currently in a state of weakening economic growth, with further amassed levels of joblessness, unremitting poverty and inequality. Due to investor reluctance, solicitation of strategic infrastructure funding is progressively becoming a debilitating challenge in all government institutions. Exacerbating these circumstances further, is substandard functionality of existing infrastructure subsequent to inadequate maintenance practices. This in-depth multi-sectoral study into the state of infrastructure is to understand the principal reasons for infrastructure functionality regression better; furthermore, prioritised investigations into progressive maintenance strategies is focused upon. Resultant recommendations reveal enhanced maintenance strategies, with a vision to capitalize on infrastructure design life, and also give special emphasis to socio-economic development imperatives in the long-term. The research method is principally based on descriptive methods (survey, historical, content analysis, qualitative).

Keywords: infrastructure, maintenance, socio-economic, strategies

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Authors: Isadora Bugarin, Taygoara F. de Oliveira

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Binary fluids and emulsions, in general, are present in a vast range of industrial, medical, and scientific applications, showing complex behaviors responsible for defining the flow dynamics and the system operation. However, the literature describing those highlighted fluids in non-isothermal models is currently still limited. The present work brings a detailed investigation on droplet migration due to natural convection in square enclosure, aiming to clarify the effects of drop viscosity on the flow dynamics by showing how distinct viscosity ratios (droplet/ambient fluid) influence the drop motion and the final movement pattern kept on stationary regimes. The analysis was taken by observing distinct combinations of Rayleigh number, drop initial position, and viscosity ratios. The Navier-Stokes and Energy equations were solved considering the Boussinesq approximation in a laminar flow using the finite differences method combined with the Level Set method for binary flow solution. Previous results collected by the authors showed that the Rayleigh number and the drop initial position affect drastically the motion pattern of the droplet. For Ra ≥ 10⁴, two very marked behaviors were observed accordingly with the initial position: the drop can travel either a helical path towards the center or a cyclic circular path resulting in a closed cycle on the stationary regime. The variation of viscosity ratio showed a significant alteration of pattern, exposing a large influence on the droplet path, capable of modifying the flow’s behavior. Analyses on viscosity effects on the flow’s unsteady Nusselt number were also performed. Among the relevant contributions proposed in this work is the potential use of the flow initial conditions as a mechanism to control the droplet migration inside the enclosure.

Keywords: binary fluids, droplet motion, level set method, natural convection, viscosity

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Authors: Jaan Lellep, Shahid Mubasshar

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A numerical solution is developed for simply supported nanoarches based on the non-local theory of elasticity. The nanoarch under consideration has a step-wise variable cross-section and is weakened by crack-like defects. It is assumed that the cracks are stationary and the mechanical behaviour of the nanoarch can be modeled by Eringen’s non-local theory of elasticity. The physical and thermal properties are sensitive with respect to changes of dimensions in the nano level. The classical theory of elasticity is unable to describe such changes in material properties. This is because, during the development of the classical theory of elasticity, the speculation of molecular objects was avoided. Therefore, the non-local theory of elasticity is applied to study the vibration of nanostructures and it has been accepted by many researchers. In the non-local theory of elasticity, it is assumed that the stress state of the body at a given point depends on the stress state of each point of the structure. However, within the classical theory of elasticity, the stress state of the body depends only on the given point. The system of main equations consists of equilibrium equations, geometrical relations and constitutive equations with boundary and intermediate conditions. The system of equations is solved by using the method of separation of variables. Consequently, the governing differential equations are converted into a system of algebraic equations whose solution exists if the determinant of the coefficients of the matrix vanishes. The influence of cracks and steps on the natural vibration of the nanoarches is prescribed with the aid of additional local compliance at the weakened cross-section. An algorithm to determine the eigenfrequencies of the nanoarches is developed with the help of computer software. The effects of various physical and geometrical parameters are recorded and drawn graphically.

Keywords: crack, nanoarches, natural frequency, step

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Authors: Asim Alsharif, Christophe Pinna, Hassan Ghadbeigi

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The development of next-generation advanced high strength steels (AHSS) used in the automotive industry requires a better understanding of local deformation and damage development at the scale of their microstructures. This work is focused on dual-phase DP1000 steels and involves micro-mechanical tensile testing inside a scanning electron microscope (SEM) combined with digital image correlation (DIC) to quantify the heterogeneity of deformation in both ferrite and martensite and its evolution up to fracture. Natural features of the microstructure are used for the correlation carried out using Davis LaVision software. Strain localization is observed in both phases with tensile strain values up to 130% and 110% recorded in ferrite and martensite respectively just before final fracture. Damage initiation sites have been observed during deformation in martensite but could not be correlated to local strain values. A finite element (FE) model of the microstructure has then been developed using Abaqus to map stress distributions over representative areas of the microstructure by forcing the model to deform as in the experiment using DIC-measured displacement maps as boundary conditions. A MATLAB code has been developed to automatically mesh the microstructure from SEM images and to map displacement vectors from DIC onto the FE mesh. Results show a correlation of damage initiation at the interface between ferrite and martensite with local principal stress values of about 1700MPa in the martensite phase. Damage in ferrite is now being investigated, and results are expected to bring new insight into damage development in DP steels.

Keywords: advanced high strength steels, digital image correlation, finite element modelling, micro-mechanical testing

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Authors: Latef M. Ali, Farah A. Abed

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In this paper, the effect of the Barium fluoride (BaF2) layer on the absorption efficiency of GaAs/InAs nanowire solar cells was investigated using the finite difference time domain (FDTD) method. By inserting the BaF2 as antireflection with the dominant size of 10 nm to fill the space between the shells of wires on the Si (111) substrate. The absorption is significantly improved due to the strong reabsorption of light reflected at the shells and compared with the reference cells. The present simulation leads to a higher absorption efficiency (Qabs) and reaches a value of 97%, and the external quantum efficiencies (EQEs) above 92% are observed. The current density (Jsc) increases by 0.22 mA/cm2 and the open-circuit voltage (Voc) is enhanced by 0.11 mV.

Keywords: nanowire solar cells, absorption efficiency, photovoltaic, band structures, fdtd simulation

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Authors: Arun Perumbilavil Anand

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For the past few years, the state of Kerala has been witnessing a large inflow of migrant workers from other states of the country, which emerged as a result of demographic transition and Gulf emigration. The in-migration patterns in Kerala have changed over the time with the migrants having a higher residence history bringing their families to the state, thereby making the process more complicated and divergent in its approach. These developments have led to an increase in the young migrant population at least in some parts of the state, which has opened up doubts and questions related to their future in the host society. At this juncture, the study ponders into the factors that are associated with the assimilation and wellbeing of migrant children in the society of Kerala. As one of the objectives, the study also analyzed the influence and role played by the educational institutions (both public and private) in meeting the needs and aspirations of both the children and their parents. The study gains significance as it tries to identify various impediments that hinder the cognitive skill formation and behaviour patterns of the migrant children in the host society. Data and Methodology: The study is based on the primary data collected through a series of interviews and interactions held with parents, children, and teachers of different educational institutions, including both public and private. The primary survey also made use of research techniques like observation, in-depth interviews, and case study method. The study was conducted in schools in the Kanjikode area of the Palakkad district in Kerala. The findings of the study are on the basis of a survey conducted in four schools and 40 migrant children. Findings: The study found that majority of the children have wholly integrated and assimilated into the host society. The influence of the peer group was quite visible in giving stimulus to the assimilation process. Most of the children do not have any emotional or cultural sentiments attached to their state of origin, and they consider Kerala as their ‘home state’ and the local language (Malayalam) as their ‘mother tongue'. The study could also find that the existing education system in the host society fails to meet the needs and aspirations of migrants as well as that of their children. On a comparative scale, to some extent, private schools have succeeded in fulfiling the special requirements of the migrant children. An interesting point that the study could pinpoint at is that the children of the migrants show better health conditions and wellbeing than compared to the natives, which is usually addressed as an epidemiologic paradox. As a concluding remark, the study recommends the inclusion concept of inclusive education into the education system of the state with giving due emphasis on those who are at higher risk of being excluded or marginalized, along with fostering increased interaction between diverse groups.

Keywords: assimilation, Kerala, migrant children, well-being

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Authors: Bilgehan Gultekin, Tuba Gultekin

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Diplomatic public relations gives an ideal concept for recognition of palestine state in all over the europe. The first step of official recognition is approval of palestine state in international political organisations such as United Nations and Nato. So, diplomatic public relations provides a recognition process in communication scale. One of the aims of the study titled “Diplomatic Public Relations Techniques for Recognition of Palestine State in Europe” is to present some communication projects on diplomatic way. The study also aims at showing communication process at diplomatic level. The most important level of such kind of diplomacy is society based diplomacy. Moreover,The study provides a wider perspective that gives some creative diplomatic communication strategies for attracting society. To persuade the public for official recognition also is key element of this process. The study also finds new communication routes including persuasion techniques for society. All creative projects are supporting parts in original persuasive process of official recognition of Palestine.

Keywords: diplomatic public relations, diplomatic communication strategies, diplomatic communication, public relations

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Authors: Aminu Mubarak Sadis

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This study appraised the maintenance management practice in Federal University Dutse and Jigawa State Polytechnic Dutse, in Nigeria. The Physical Planning, Works and Maintenance Departments of the two Higher Institutions (Federal University Dutse and Jigawa State Polytechnic) are responsible for production and maintenance management of their physical assets. Over–enrollment problem has been a common feature in the higher institutions in Nigeria, Data were collected by the administered questionnaires and subsequent oral interview to authenticate the completed questionnaires. Random sampling techniques was used in selecting 150 respondents across the various institutions (Federal University Dutse and Jigawa State Polytechnic Dutse). Data collected was analyzed using Statistical Package for Social Science (SPSS) and t-test statistical techniques The conclusion was that maintenance management activities are yet to be given their appropriate attention on functions of the university and polytechnic which are crucial to improving teaching, learning and research. The unit responsible for maintenance and managing facilities should focus on their stated functions and effect changes were possible.

Keywords: appraisal, maintenance management, university, Polytechnic, practices

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Authors: Alok Kumar Kamal, Vinod Kumar

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The trench gate MOSFET has shown itself as the most appropriate power device for low to medium voltage power applications due to its lowest possible ON resistance among all power semiconductor devices. In this research work a double-epilayer PSGT structure using a thin layer of N+ polysilicon as gate material. The total ON-state resistance (RON) of UMOSFET can be reduced by optimizing the epilayer thickness. The optimized structure of Double-Epilayer exhibits a 25.8% reduction in the ON-state resistance at Vgs=5V and improving the switching characteristics by reducing the Reverse transfer capacitance (Cgd) by 7.4%.

Keywords: Miller-capacitance, double-Epilayer;switching characteristics, power trench MOSFET (U-MOSFET), on-state resistance, blocking voltage

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Authors: Saeedeh Barzegar Khalilsaraei, Manoocheher Kelarestaghi, Farshad Eshghi

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The vehicle color, as a prominent and stable feature, helps to identify a vehicle more accurately. As a result, vehicle color recognition is of great importance in intelligent transportation systems. Unlike conventional methods which use only a single Convolutional Neural Network (CNN) for feature extraction or classification, in this paper, four CNNs, with different architectures well-performing in different classes, are trained to extract various features from the input image. To take advantage of the distinct capability of each network, the multiple outputs are combined using a stack generalization algorithm as an ensemble technique. As a result, the final model performs better than each CNN individually in vehicle color identification. The evaluation results in terms of overall average accuracy and accuracy variance show the proposed method’s outperformance compared to the state-of-the-art rivals.

Keywords: Vehicle Color Recognition, Ensemble Algorithm, Stack Generalization, Convolutional Neural Network

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Authors: O. Delage, H. Bencherif, T. Portafaix, A. Bourdier

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The main purpose of time series analysis is to learn about the dynamics behind some time ordered measurement data. Two approaches are used in the literature to get a better knowledge of the dynamics contained in observation data sequences. The first of these approaches concerns time series decomposition, which is an important analysis step allowing patterns and behaviors to be extracted as components providing insight into the mechanisms producing the time series. As in many cases, time series are short, noisy, and non-stationary. To provide components which are physically meaningful, methods such as Empirical Mode Decomposition (EMD), Empirical Wavelet Transform (EWT) or, more recently, Empirical Adaptive Wavelet Decomposition (EAWD) have been proposed. The second approach is to reconstruct the dynamics underlying the time series as a trajectory in state space by mapping a time series into a set of Rᵐ lag vectors by using the method of delays (MOD). Takens has proved that the trajectory obtained with the MOD technic is equivalent to the trajectory representing the dynamics behind the original time series. This work introduces the singular spectrum decomposition (SSD), which is a new adaptive method for decomposing non-linear and non-stationary time series in narrow-banded components. This method takes its origin from singular spectrum analysis (SSA), a nonparametric spectral estimation method used for the analysis and prediction of time series. As the first step of SSD is to constitute a trajectory matrix by embedding a one-dimensional time series into a set of lagged vectors, SSD can also be seen as a reconstruction method like MOD. We will first give a brief overview of the existing decomposition methods (EMD-EWT-EAWD). The SSD method will then be described in detail and applied to experimental time series of observations resulting from total columns of ozone measurements. The results obtained will be compared with those provided by the previously mentioned decomposition methods. We will also compare the reconstruction qualities of the observed dynamics obtained from the SSD and MOD methods.

Keywords: time series analysis, adaptive time series decomposition, wavelet, phase space reconstruction, singular spectrum analysis

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Authors: Mustapha Abdulkadir Gana, Jibrin Attahiru Alhassan, Adamu Musa Baba

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The exponential growth of information sources, resources and the continued Communication Technology (ICT) sophistication of libraries all over the world call for capable and ICT compliant librarians in Nigeria, this article assesses the digital literacy skills of librarians in tertiary institutions in Niger state. The survey research method was applied in the study using a random sampling technique to draw the sample. Fifty-eight copies of the questionnaire were administered while forty-nine copies were completed, returned, and used in the study, which represents 84% of the response rate. Two research questions were answered, and data were analyzed using Statistical Package for the Social Sciences (SPSS). The finding uncovered that the librarians lack the requisite digital literacy skills to access the wealth of digital information resources available. The study recommends some steps to turn around the situations amongst; librarians must be empowered with all necessary digital literacy skills, embark on rigorous training and retraining programs, workshops, conferences, and seminars, there should also be a coherent training policy for the librarians on a sustainable basis to increase their requisite digital literacy skills.

Keywords: digital, information, literacy, skills

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Authors: Duncan K. Espenshade

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Scholars have established expectations regarding how the political and economic interests of a country's people and elites can influence its migration policies. Most of the scholarship exploring the adoption of migration policies focuses on the developed world, focusing on the cultural, political, and economic influences that drive restrictive policies in developed countries. However, despite the scholarly focus on migration policies in developed countries, most internationally displaced people reside in developing countries. Furthermore, while the political and economic factors that influence migration policy in developed countries are likely at play in developing states, developing states also face unique hurdles to policy formation not present in developed states. Namely, this article explores how state capacity, or in this context, a state's de facto ability to restrict or absorb migration inflows, influences the adoption of migration policies in developing countries. Using Cox-Proportional hazard models and recently introduced data on asylum policies in developing countries, this research finds that having a greater ability to restrict migration flows is associated with a reduced likelihood of adopting liberal asylum policies. Future extensions of this project will explore the adoption of asylum policies as a two-stage process, in which the available decision set of political actors is first constrained by a state's restrictive and absorptive capacity in the first stage, with the political, economic, and cultural factors influencing the policy adopted in the second stage.

Keywords: state capacity, international relations, foreign policy, migration

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Authors: Usman Ahmed Adam, Umar Ibrahim, Ezra S. Gbaje

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This study is posed to explore the practice of Public Access Computers (PACs) in academic libraries in Kaduna State, Nigeria. The study aimed to determine the computers and other tools available, their services and challenges of the practices. Three questions were framed to identify number of public computers and tools available, their services and problems faced during the practice. The study used qualitative research design along with semi-constructed interview and observation as tools for data collection. Descriptive analysis was employed to analyze the data. The sample size of the study comprises 52 librarian and IT staff from the seven academic institutions in Kaduna State. The findings revealed that, PACs were provided for access to the Internet, digital resources, library catalogue and training services. The study further explored that, despite the limit number of the computers, users were not allowed to enjoy many services. The study recommends that libraries in Kaduna state should provide more public computers to be able to cover the population of their users; libraries should allow users to use the computers without limitations and restrictions.

Keywords: academic libraries, computers in library, digital libraries, public computers

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Authors: Louaifi Hamaili Samira, Mataoui Amina, Cheraitia Tadjeddine

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This investigation proposes a numerical analysis of two turbulent parallel jets impinging a heated plate. The heat transfer enhancement is carried out according of the main parameters of the jet-wall interaction. The numerical solution of the stationary equations (RANS) is performed by the finite volume method using the k - ε model. A parametric study is performed to evaluate simultaneously the effect of nozzle-plate distance and velocity ratios in the range 0≤λ≤1. It is found that good local cooling is obtained for λ= 0.25 when the impinging distance is between 4w and 8w than for velocity ratios λ=1 and λ= 0.75. On the other hand, for impinging distances exceeding 8w, the velocity ratio λ =0.75 is more appropriate for good local cooling of the plate.

Keywords: two unequal jets, turbulence, mixing, heat transfer, CFD

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Authors: Raza Abdulla Saeed

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In this study, the three-dimensional cavitating turbulent flow in a complete Francis turbine is simulated using mixture model for cavity/liquid two-phase flows. Numerical analysis is carried out using ANSYS CFX software release 12, and standard k-ε turbulence model is adopted for this analysis. The computational fluid domain consist of spiral casing, stay vanes, guide vanes, runner and draft tube. The computational domain is discretized with a three-dimensional mesh system of unstructured tetrahedron mesh. The finite volume method (FVM) is used to solve the governing equations of the mixture model. Results of cavitation on the runner’s blades under three different boundary conditions are presented and discussed. From the numerical results it has been found that the numerical method was successfully applied to simulate the cavitating two-phase turbulent flow through a Francis turbine, and also cavitation is clearly predicted in the form of water vapor formation inside the turbine. By comparison the numerical prediction results with a real runner; it’s shown that the region of higher volume fraction obtained by simulation is consistent with the region of runner cavitation damage.

Keywords: computational fluid dynamics, hydraulic francis turbine, numerical simulation, two-phase mixture cavitation model

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Authors: Nurudeen Oluwasola Lasisi

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The COVID-19 is an infection caused by coronavirus, which has been designated as a pandemic in the world. In this paper, we proposed a model to study the effect of distancing and wearing masks on the transmission of COVID-19 infection dynamics. The invariant region of the model is established. The COVID-19 free equilibrium and the reproduction number of the model were obtained. The local and global stability of the model is determined using the linearization technique method and Lyapunov method. It was found that COVID-19 free equilibrium state is locally asymptotically stable in feasible region Ω if R₀ < 1 and globally asymptomatically stable if R₀ < 1, otherwise unstable if R₀ > 1. More so, numerical analysis and simulations of the dynamics of the COVID-19 infection are presented.

Keywords: distancing, reproduction number, wearing of mask, local and global stability, modelling, transmission

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Authors: Ehsan Abshirini

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Rivers as one of the most important topographic factors have played a strategic role not only on the appearance of cities but they also affect the structure and morphology of cities. In this paper author intends to find out how a city in its physical network interacts with a river flowing inside. The pilot study is Angers, a city in western France, in which it is influenced by the Maine River. To this purpose space syntax method integrating with GIS is used to extract the properties of physical form of cities in terms of global and local integration value, accessibility and choice value. Simulating the state of absence of river in this city and comparing the result to the current state of city according to the effect of river on the morphology of areas located in different banks of river is also part of interest in this paper. The results show that although a river is not comparable to the city based on size and the area occupied by, it has a significant effect on the form of the city in both global and local properties. In addition, this study endorses that tracking the effect of river-cities and their interaction to rivers in a hybrid of space syntax and GIS may lead researchers to improve their interpretation of physical form of these types of cities.

Keywords: river-cities, Physical form, space syntax properties, GIS, topographic factor

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Authors: F. A. Hassona, M. D. Hashem, R. I. Melek, B. M. Hakeem

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A differential settlement at the end of a bridge near the interface between the abutment and the embankment is a persistent problem for highway agencies. The differential settlement produces the common ‘bump at the end of the bridge’. Reduction in steering response, distraction to the driver, added risk and expense to maintenance operation, and reduction in a transportation agency’s public image are all undesirable effects of these uneven and irregular transitions. This paper attempts to simulate the bump at the end of the bridge using PLAXIS finite element 2D program. PLAXIS was used to simulate a laboratory model called Bridge to Embankment Simulator of Transition (B.E.S.T.) device which was built by others to investigate this problem. A total of six numerical simulations were conducted using hardening- soil model with rational assumptions of missing soil parameters to estimate the bump at the end of the bridge. The results show good agreements between the numerical and the laboratory models. Important factors influencing bumps at bridge ends were also addressed in light of the model results.

Keywords: bridge approach slabs, bridge bump, hardening-soil, PLAXIS 2D, settlement

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Authors: Abbas Shafiee, Mohammad Taghi Ahmadian, Maryam Hoviattalab

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The biomechanical behavior of brain tissue is needed for predicting the traumatic brain injury (TBI). Each year over 1.5 million people sustain a TBI in the USA. The appropriate coefficients for injury prediction can be evaluated using experimental data. In this study, an experimental setup on brain soft tissue was developed to perform unconfined compression tests at quasistatic strain rates ∈0.0004 s-1 and 0.008 s-1 and 0.4 stress relaxation test under unconfined uniaxial compression with ∈ 0.67 s-1 ramp rate. The fitted visco-hyperelastic parameters were utilized by using obtained stress-strain curves. The experimental data was validated using finite element analysis (FEA) and previous findings. Also, influence of friction coefficient on unconfined compression and relaxation test and effect of ramp rate in relaxation test is investigated. Results of the findings are implemented on the analysis of a human brain under high acceleration due to impact.

Keywords: brain soft tissue, visco-hyperelastic, finite element analysis (FEA), friction, quasistatic strain rate

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Authors: Saheed A. Gbadegeshin

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Commercialization method is a means to make inventions available at the market for final consumption. It is described as an important tool for keeping business enterprises sustainable and improving national economic growth. Thus, there are several scholarly publications on it, either presenting or testing different methods for commercialization. However, young entrepreneurs, technologists and scientists would like to know the best method to commercialize their innovations. Then, this question arises: What is the best commercialization method? To answer the question, a systematic literature review was conducted, and practitioners were interviewed. The literary results revealed that there are many methods but new methods are needed to improve commercialization especially during these times of economic crisis and political uncertainty. Similarly, the empirical results showed there are several methods, but the best method is the one that reduces costs, reduces the risks associated with uncertainty, and improves customer participation and acceptability. Therefore, it was concluded that new commercialization method is essential for today's high technologies and a method was presented.

Keywords: commercialization method, technology, knowledge, intellectual property, innovation, invention

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Authors: Shu-Yang Zhang, Shun-Qi Zhang, Zhan-Xi Wang, Xian-Sheng Qin

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Thin-walled structures are used more and more widely in modern aircrafts and some other structures in aerospace field nowadays. Accompanied by the wider applications, the vibration of the structures has been a bigger problem. Because of the direct and converse piezoelectric effect, piezoelectric materials combined to host thin-walled structures, named as piezoelectric smart structures, can be an effective way to suppress the vibration. So, an accurate model for piezoelectric thin-walled structures in air flow is necessary and important. In our recent work, an electromechanical coupling nonlinear aerodynamic finite element model of piezoelectric smart thin-walled structures is built based on the Reissner-Mindlin plate theory and first-order piston theory for aerodynamic pressure of supersonic flow. Von Kármán type nonlinearity is considered in the present model. Finally, the model is validated by experimental and numerical results from the literature, which can describe the vibration of the structures in supersonic flow precisely.

Keywords: piezoelectric smart structures, aerodynamic, geometric nonlinearity, finite element analysis

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Authors: Gökhan Yüksel, Serdar Akça, İlker Kalkan

Abstract:

The present study is an attempt to demonstrate the significant levels of contribution of the moment-resisting beam-column connections with side plates to the earthquake behavior of special steel moment frames. To this end, the moment-curvature relationships of a regular beam-column connection and its SidePlate counterpart were determined with the help of finite element analyses. The connection stiffness and deformability values from these finite element analyses were used in the linear time-history analyses of an example structural steel frame under three different seismic excitations. The top-story lateral drift, base shear, and overturning moment values in two orthogonal directions were obtained from these time-history analyses and compared to each other. The results revealed the improvements in the system response with the use of SidePlate connections. The paper ends with crucial recommendations for the plan and design of further studies on this very topic.

Keywords: seismic detailing, special moment frame, steel structures, beam-column connection, earthquake-resistant design

Procedia PDF Downloads 85

Authors: Dirk Zapf, Bastian Leuger

Abstract:

For several years, natural gas and crude oil have been stored in salt caverns in Germany and also worldwide. The dimensioning concepts have been continuously developed from a rock mechanics point of view. In addition to the possibilities of realizing large numerical calculation models based on real survey data nowadays, especially the consideration of mechanical processes such as damage and healing played a role in the development of adequate material laws. In addition, thermodynamic aspects have had to be considered for some years in the operation of a gas storage cavern since temperature changes have a significant influence on the stress states in the vicinity of a storage cavern. The possibility of thermally induced fracturing processes is also investigated in the context of rock mechanics dimensioning. In recent years, the energy crisis and the finite nature of fossil fuel use have led to increased discussion of the use of salt caverns for hydrogen storage. In this paper, state of the art is presented, the current research work is described, and an outlook is given as to which questions still need to be answered from a rock mechanics point of view in connection with large-scale storage of hydrogen in salt caverns.

Keywords: cavern design, hydrogen, rock salt, thermomechanical coupled calculations

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Authors: H. Bhowmik, A. Faisal, Ahmed Al Yaarubi, Nabil Al Alawi

Abstract:

Experiments are conducted to analyze the steady-state and the power-on transient natural convection heat transfer from a horizontal cylinder mounted in a vertical up flow circular duct. The heat flux ranges from 177 W/m² to 2426 W/m² and the Rayleigh number ranges from 1×10⁴ to 4.35×10⁴. For natural air flow and constant heat flux condition, the effects of heat transfer around the cylinder under steady-state condition are investigated. The steady-state results compare favorably with that of the available data. The effects of transient heat transfer data on different angular position of the thermocouple (0^o, 90^o, 180^o) are also reported. It is observed that the transient heat transfer around the cylinder is strongly affected by the position of thermocouples. In the transient region, the rate of heat transfer obtained at 90^o and 180^o are higher than that of stagnation point (0^o). Finally, the dependence of the average Nusselt number on Rayleigh number for steady and transient natural convection heat transfer are analyzed, and a correlation equation is presented.

Keywords: Fourier number, Nusselt number, Rayleigh number, steady state, transient

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Authors: L. Wei Sheng, M. T. Noor Syazwanee, C. J. Carolyna, M. Amiruddin, M. Pauziah

Abstract:

This paper exhibits the alternatives towards active suspension systems revised based on the classical passive suspension system to improve comfort and handling performance. An active Magneto rheological (MR) suspension system is proposed as to explore the active based suspension system to enhance performance given its freedom to independently specify the characteristics of load carrying, handling, and ride quality. Malaysian quarter car with two degrees of freedom (2DOF) system is designed and constructed to simulate the actions of an active vehicle suspension system. The structure of a conventional twin-tube shock absorber is modified both internally and externally to comprehend with the active suspension system. The shock absorber peripheral structure is altered to enable the assembling and disassembling of the damper through a non-permanent joint whereby the stress analysis of the designed joint is simulated using Finite Element Analysis. Simulation on the internal part where an electrified copper coil of 24AWG is winded is done using Finite Element Method Magnetics to measure the magnetic flux density inside the MR damper. The primary purpose of this approach is to reduce the vibration transmitted from the effects of road surface irregularities while maintaining solid manoeuvrability. The aim of this research is to develop an intelligent control system of a consecutive damping automotive suspension system. The ride quality is improved by means of the reduction of the vertical body acceleration caused by the car body when it experiences disturbances from speed bump and random road roughness. Findings from this research are expected to enhance the quality of ride which in return can prevent the deteriorating effect of vibration on the vehicle condition as well as the passengers’ well-being.

Keywords: active suspension, FEA, magneto rheological damper, Malaysian quarter car model, vibration control

Procedia PDF Downloads 196