Search results for: results

Authors: Reem I. Al-Ya' Goub, Nasim Shatarat

Abstract:

This paper presents the results of analytical and comparative study among software programs' outputs in analysis of some two way solid slabs; flat plate, flat slab with beams and flat slab with drop panels problems that already been analyzed using Classical Equivalent Frame Method (CEFM) by several reinforced concrete book authors. The primary objective of this research is to determine the moment results using various software programs. Then, a summary of the results and differences percentages were obtained to show how analysis procedure effects the outputs of calculations that vary from software program to another when comparing them with the results of CEFM. Moment values were obtained using either the Equivalent Frame Method (EFM) or Finite Element Method (FEM) that's used among many software programs. The results of the analyses demonstrate that software programs vary markedly in terms of the information they provide to the structural designer regarding values of the model insertion, stiffness, effective moment of inertia used and specially the moment values.

Keywords: two-way solid slabs, flat plate, flat slab with beams, flat slab with drop panels, analysis, modeling, EFM, CEFM, FEM

Procedia PDF Downloads 412

Authors: Bahloul Amel

Abstract:

The main aim of this research was to investigate the perspectives of English language teachers and learners on the effect of test techniques on reading comprehension, test performance and assessment. The research has also aimed at finding the differences between teacher and learner perspectives, specifying the test techniques which have the highest effect, investigating the other factors affecting reading comprehension, and comparing the results with the similar studies. In order to achieve these objectives, perspectives and findings of different researchers were reviewed, two different questionnaires were prepared to collect data for the perspectives of teachers and learners, the questionnaires were applied to 26 learners and 8 teachers from the University of Batna (Algeria), and quantitative and qualitative data analysis of the results were done. The results and analysis of the results show that different test techniques affect reading comprehension, test performance and assessment at different percentages rates.

Keywords: reading comprehension, reading assessment, test performance, test techniques

Procedia PDF Downloads 460

Authors: Rasheed O. Oloyede, Joseph O. Adelusi, Peter O. Akinbile

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This study was conducted to investigate the extent with which knowledge of results influences the performance of cricket players. A sample of 160 fresh students in the Department of Physical and Health Education who are novice in the game were randomly assigned into two groups. The first group of eighty (80) subjects was classified as experimental group while the second group of eighty (80) subjects was the control group. Subjects in both groups were asked to bowl and bat ten times each for a period of six weeks. After the first round, the subjects in the experimental group were allowed feedback on their performance in the first trial while those in the control group were denied feedback. Two null hypotheses generated for the study were tested using percentages and chi-square statistical analysis at 0.05 level of significance. Analysis of data showed that knowledge of results influenced the performance of cricket players. It was concluded that knowledge of results is pertinent for effective skill acquisition and could enhance better performance among unskilled cricket players. Hence, it is suggested that immediate feedback on the level of skill acquisition by the prospective and unskilled cricket players would inspire them for better performance in cricket tournaments.

Keywords: batting, bowling, knowledge of results, performance, skill acquisition

Procedia PDF Downloads 466

Authors: Jan Barak, Karel Frana, Joerg Stiller

Abstract:

This work presents results of moist air condensation in heat exchanger. It describes theoretical knowledge and definition of moist air. Model with geometry of square canal was created for better understanding and post processing of condensation phenomena. Different approaches were examined on this model to find suitable software and model. Obtained knowledge was applied to geometry of real heat exchanger and results from experiment were compared with numerical results. One of the goals is to solve this issue without creating any user defined function in the applied code. It also contains summary of knowledge and outlook for future work.

Keywords: condensation, exchanger, experiment, validation

Procedia PDF Downloads 403

Authors: Tazvin Ijaz, Rabia Khan

Abstract:

The current study was conducted to identify the predictors of burnout among university students. The sample for the study was collected through simple random sampling. The tools to measure burnout and personality characteristics included Indigenous burnout scale and Eysenck personality inventory respectively. Results indicated that neurotic personality traits significantly predicts burnout among university students while extraversion does not lead to burnout. Results also indicated female students experience more burnout than male students. It was also found that family size and birth order did not affected the level of burnout. Results of the study are discussed to explain association between etiological factors and burnout with in Pakistani cultural context.

Keywords: burnout, students, neuroticism, extraversion

Procedia PDF Downloads 297

Authors: Elham Zamiri

Abstract:

In this research, we have focused on numeral simulation of a fuel rod in order to examine distribution of heat temperature in components of fuel rod by Fluent software by providing steady state, single phase fluid flow, frequency heat flux in a fuel rod in nuclear reactor to numeral simulation. Results of examining different layers of a fuel rod consist of fuel layer, gap, pod, and fluid cooling flow, also examining thermal properties and fluids such as heat transition rate and pressure drop. The obtained results through analytical method and results of other sources have been compared and have appropriate correspondence. Results show that using heavy water as cooling fluid along with few layers of gas and pod have the ability of reducing the temperature from above 300 ^◦C to 70 ^◦C. This investigation is developable for any geometry and material used in the nuclear reactor.

Keywords: nuclear fuel fission, numberal simulation, fuel rod, reactor, Fluent software

Procedia PDF Downloads 166

Authors: Leila Torkaman, Nasser Ghassembaglou

Abstract:

Significant quota of Municipal Electrical Energy consumption is related to Decentralized Air Conditioning which is mostly provided by evaporative coolers. So the aim is to optimize design of air conditioners to increase their efficiencies. To achieve this goal, results of practical standardized tests for 40 evaporative coolers in different types collected and simultaneously results for same coolers based on one of EER (Energy Efficiency Ratio) modeling styles are figured out. By comparing experimental results of different coolers standardized tests with modeling results, preciseness of used model is assessed and after comparing gained preciseness with international standards based on EER for cooling capacity, aeration and also electrical energy consumption, energy label from A (most effective) to G (less effective) is classified. finally needed methods to optimize energy consumption and cooler's classification are provided.

Keywords: cooler, EER, energy label, optimization

Procedia PDF Downloads 345

Authors: Y. Chiang, W. Y. Li, J. R. Wang, S. W. Chen, W. S. Hsu, J. H. Yang, Y. S. Tseng, C. Shih

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In this research, the HABIT code was used to estimate the concentration under the CO₂ and H₂SO₄ storage burst conditions for Kuosheng nuclear power plant (NPP). The Final Safety Analysis Report (FSAR) and reports were used in this research. In addition, to evaluate the control room habitability for these cases, the HABIT analysis results were compared with the R.G. 1.78 failure criteria. The comparison results show that the HABIT results are below the criteria. Additionally, some sensitivity studies (stability classification, wind speed and control room intake rate) were performed in this study.

Keywords: BWR, HABIT, habitability, Kuosheng

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Authors: Nuradeen Abdullahi Nadabo, Kasali Adewale Bello, Chindo Istifanus

Abstract:

A series of ten bi functional mono-chloro-s-triazine vinyl sulphone reactive dyes were synthesized based on H-acid with varied substituents coded as (BRD). These dyes were characterized by IR spectroscopy. The results revealed an incorporation of various substituents. The visible absorption spectra of these dyes were examined in various solvents and results shows positive and negative salvatochromism as the solvent polarity; changes, melting point, percentage yield and molar extinction co-efficient of these dyes were also evaluated and the results obtained are within a reasonable range acceptable for commercial dyeing.

Keywords: bifunctional, characterization, reactive dyes, synthesis

Procedia PDF Downloads 436

Authors: Radostina Popova

Abstract:

The paper presents an analysis of the innovation performance of small and medium-sized furniture enterprises in Bulgaria, accounting for over 97% of the companies in the sector. It contains advanced features of innovation in enterprises, specific features of the furniture industry in Bulgaria and analysis of the results of studies on the topic. The results from studies of three successive periods - 2006-2008; 2008-2010; 2010-2012, during which were studied 594 small and medium-sized furniture enterprises. There are commonly used in the EU definitions and indicators (European Commission, OECD, Oslo Manual), which allows for the comparability of results.

Keywords: innovation activity, competitiveness of innovation, furniture enterprises in Bulgaria

Procedia PDF Downloads 272

Authors: Bib Paruhum Silalahi, Djihad Wungguli, Sugi Guritman

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Steepest descent method is a simple gradient method for optimization. This method has a slow convergence in heading to the optimal solution, which occurs because of the zigzag form of the steps. Barzilai and Borwein modified this algorithm so that it performs well for problems with large dimensions. Barzilai and Borwein method results have sparked a lot of research on the method of steepest descent, including alternate minimization gradient method and Yuan method. Inspired by previous works, we modified the step size of the steepest descent method. We then compare the modification results against the Barzilai and Borwein method, alternate minimization gradient method and Yuan method for quadratic function cases in terms of the iterations number and the running time. The average results indicate that the steepest descent method with the new step sizes provide good results for small dimensions and able to compete with the results of Barzilai and Borwein method and the alternate minimization gradient method for large dimensions. The new step sizes have faster convergence compared to the other methods, especially for cases with large dimensions.

Keywords: steepest descent, line search, iteration, running time, unconstrained optimization, convergence

Procedia PDF Downloads 540

Authors: Hudson Akewe

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We prove that the convergence of explicit Mann, explicit Ishikawa, explicit Noor, explicit SP, explicit multistep and explicit multistep-SP fixed point iterative procedures are equivalent for the classes of multi-valued phi-contraction, phi-Zamfirescu and phi-quasi-contractive mappings in the framework of modular function spaces. Our results complement equivalence results on normed and metric spaces in the literature as they elegantly cut out the triangle inequality.

Keywords: multistep iterative procedures, multivalued mappings, equivalence results, fixed point

Procedia PDF Downloads 132

Authors: A. van Staden, A. A. van Rhyn

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The numerous challenges South African, ESL learners experience were highlighted by the results of several literacy surveys and tests, which demonstrated that our learners’ literacy abilities are far below standard and very weak compared to other international countries. This study developed and implemented an interactive storybook intervention program to support the reading development of ESL learners. The researchers utilized an experimental pre-test/post-test research design, whereby 80 ESL learners from five participating schools, were purposively sampled to take part in this study. This paper, inter alia, discusses the key features of this intervention program whilst also reporting the results of the experimental investigation. Results are promising and show a significant improvement in the mean scores of the learners in the experimental group. Moreover, the results show the value of interactive storybook reading in creating responsive literacy environments to develop the literacy skills of ESL learners.

Keywords: ESL learners, reading comprehension, Interactive story book reading, South Africa

Procedia PDF Downloads 135

Authors: Naim Ismajli, Ilir Rexhepi

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The article presents the results of the study about the motives and efficiency of quality management system (Quality System, QS) implementation in Kosovo companies. The main purpose of the study was to find out why Kosovo companies seek the implementation and certification of QS in accordance with the requirements of the ISO 9001 series of the standards and what has changed after the QS implementation. Furthermore, the results of the research were compared with similar performed in the other European countries. The performed research revealed that the implementation of QS mostly results in the benefits of an intangible nature that are internal to the company. In addition, although the main reasons to start implementing QS are the expectations of the external advantages, the implementation results mostly in the increase of the internal benefits such as an improvement in the definition of the responsibilities and obligations of the employees, a decrease in the nonconformities, better communication among the employees, and increased efficiency.

Keywords: quality management systems, ISO 9001, total quality management, environmental management system, ISO 14000, competitiveness, efciency

Procedia PDF Downloads 366

Authors: O. Kahraman, M. S. Alatas, O. B. Citil

Abstract:

In determination of values of feeds which, are used in ruminant nutrition, different methods are used like in vivo, in vitro, in situ or in sacco. Generally, the most reliable results are taken from the in vivo studies. But because of the disadvantages like being hard, laborious and expensive, time consuming, being hard to keep the experiment conditions under control and too much samples are needed, the in vitro techniques are more preferred. The most widely used in vitro techniques are two-staged digestion technique and gas production technique. In vitro gas production technique is based on the measurement of the CO2 which is released as a result of microbial fermentation of the feeds. In this review, the factors affecting the results obtained from in vitro gas production technique (Hohenheim Feed Test) were discussed. Some factors must be taken into consideration when interpreting the findings obtained in these studies and also comparing the findings reported by different researchers for the same feeds. These factors were discussed in 3 groups: factors related to animal, factors related to feeds and factors related with differences in the application of method. These factors and their effects on the results were explained. Also it can be concluded that the use of in vitro gas production technique in feed evaluation routinely can be contributed to the comprehensive feed evaluation, but standardization is needed in this technique to attain more reliable results.

Keywords: In vitro, gas production technique, Hohenheim feed test, standardization

Procedia PDF Downloads 600

Authors: S. Sina, B. Zeinali, M. Karimipourfard, F. Lotfalizadeh, M. Sadeghi, E. Zamani, M. Zehtabian, R. Faghihi

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Proper dosimetery is very essential in diagnostic radiology. The goal of this study is to verify the application of LiF:Mg, Cu, P (TLD100H) in obtaining the entrance skin dose (ESD) of patients undergoing diagnostic radiology. The results of dosimetry performed by TLD-100H were compared with those obtained by TLD100, which is a common dosimeter in diagnostic radiology. The results show a close agreement between the dose measured by the two dosimeters. According to the results of this study, the TLD-100H dosimeters have higher sensitivities (i.e. signal(nc)/dose) than TLD-100. Therefore, it is suggested that the TLD-100H are effective dosimeters for dosimetry in low dose fields.

Keywords: entrance skin dose, TLD, diagnostic radiology, dosimeter

Procedia PDF Downloads 475

Authors: Songul Cinaroglu

Abstract:

Machine learning regression methods are recommended as an alternative to classical regression methods in the existence of variables which are difficult to model. Data for health expenditure is typically non-normal and have a heavily skewed distribution. This study aims to compare machine learning regression methods by hyperparameter tuning to predict health expenditure per capita. A multiple regression model was conducted and performance results of Lasso Regression, Random Forest Regression and Support Vector Machine Regression recorded when different hyperparameters are assigned. Lambda (λ) value for Lasso Regression, number of trees for Random Forest Regression, epsilon (ε) value for Support Vector Regression was determined as hyperparameters. Study results performed by using 'k' fold cross validation changed from 5 to 50, indicate the difference between machine learning regression results in terms of R², RMSE and MAE values that are statistically significant (p < 0.001). Study results reveal that Random Forest Regression (R² ˃ 0.7500, RMSE ≤ 0.6000 ve MAE ≤ 0.4000) outperforms other machine learning regression methods. It is highly advisable to use machine learning regression methods for modelling health expenditures.

Keywords: machine learning, lasso regression, random forest regression, support vector regression, hyperparameter tuning, health expenditure

Procedia PDF Downloads 226

Authors: Ayman M. Mansour, Bilal Hawashin, Hesham Alsalem

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Faster delivery of laboratory test results is one of the most noticeable signs of good laboratory service and is often used as a key performance indicator of laboratory performance. Despite the availability of technology, the delivery time of clinical laboratory test results continues to be a cause of customer dissatisfaction which makes patients feel frustrated and they became careless to get their laboratory test results. The Medical Clinical Laboratory test results are highly sensitive and could harm patients especially with the severe case if they deliver in wrong time. Such results affect the treatment done by physicians if arrived at correct time efforts should, therefore, be made to ensure faster delivery of lab test results by utilizing new trusted, Robust and fast system. In this paper, we proposed a distributed Multi-Agent System to enhance and faster the process of laboratory test results delivery using SMS. The developed system relies on SMS messages because of the wide availability of GSM network comparing to the other network. The software provides the capability of knowledge sharing between different units and different laboratory medical centers. The system was built using java programming. To implement the proposed system we had many possible techniques. One of these is to use the peer-to-peer (P2P) model, where all the peers are treated equally and the service is distributed among all the peers of the network. However, for the pure P2P model, it is difficult to maintain the coherence of the network, discover new peers and ensure security. Also, security is a quite important issue since each node is allowed to join the network without any control mechanism. We thus take the hybrid P2P model, a model between the Client/Server model and the pure P2P model using GSM technology through SMS messages. This model satisfies our need. A GUI has been developed to provide the laboratory staff with the simple and easy way to interact with the system. This system provides quick response rate and the decision is faster than the manual methods. This will save patients life.

Keywords: multi-agent system, delivery process, GSM technology, clinical laboratory results

Procedia PDF Downloads 250

Authors: Mohamed Abdelfattah Meawad Hamza, H. A. Bosila, M. A. Zewil

Abstract:

This research aims to study the effect of different sources of elicitors for increase growth and active ingredients in callus of Echinacea purpurea plant. Callus that have been obtained from leaf explant, was used to conduct the following studies. A study of the impact of both the phenylalanine and tyrosine (50, 100,150 and 200 mg/l.) individually and casein hydrolysate (100, 200 and 300 mg/l.) supplemented to MS medium. Results show that Casein hydrolysate 100 mg/l. has achieved the better results in both callus fresh weight 1.881 g/explant after 8 weeks of the incubation period and callus growth rate 0.398 g/explant after 6 weeks of the incubation period, while gave add 200 mg/l. The best results in total carbohydrate 2.444 mg/ 100 mg dry weight. Phenylalanine 150 mg/l. has achieved the best results in callus dry weight 0.156 g/explant after 8 weeks of incubation period. Tyrosine 200 mg/l. recorded the best result for positive production of caffeic acid 0.460 mg/ 100 mg dry weight after 4 weeks incubation period.

Keywords: tissue culture, echinacea, tyrosine, casein

Procedia PDF Downloads 273

Authors: Narumol Chintaganun

Abstract:

In this paper we present the second-order central differencing scheme with the staggered version (STG) for solving the advection equation and Burger's equation. This scheme based on staggered evolution of the re-constructed cell averages. This scheme results in the second-order central differencing scheme, an extension along the lines of the first-order central scheme of Lax-Friedrichs (LxF) scheme. All numerical simulations presented in this paper are obtained by finite difference method (FDM) and STG. Numerical results are shown that the STG gives very good results and higher accuracy.

Keywords: central differencing scheme, STG, advection equation, burgers equation

Procedia PDF Downloads 558

Authors: J. Karthik, G. Vinayagamurthy

Abstract:

Aerodynamic flow control is achieved by interaction of flowing medium with corresponding structure so that its natural flow state is disturbed to delay the transition point. This paper explains the aerodynamic effect and optimized design of Vortex Generators on the turbine blade to achieve maximum flow control. The airfoil is chosen from NREL [National Renewable Energy Laboratory] S-series airfoil as they are characterized with good lift characteristics and lower noise. Vortex generators typically chosen are Ogival, Rectangular, Triangular and Tapered Fin shapes attached near leading edge. Vortex generators are typically distributed from the primary to tip of the blade section. The design wind speed is taken as 6m/s and the computational analysis is executed. The blade surface is simulated using k- ɛ SST model and results are compared with X-FOIL results. The computational results are validated using Wind Tunnel Testing of the blade corresponding to the design speed. The effect of Vortex generators on the flow characteristics is studied from the results of analysis. By comparing the computational and test results of all shapes of Vortex generators; the optimized design is achieved for effective flow control corresponding to the blade.

Keywords: flow control, vortex generators, design optimisation, CFD

Procedia PDF Downloads 408

Authors: Mohammad Hadi Mahmoodi, Mojtaba Farahani

Abstract:

The present study aimed at investigating whether reflective thinking differentiates Iranian EFL learners regarding language learning strategy use, beliefs about language learning and teaching, and L2 proficiency. To this end, the researcher adopted a mixed method approach. First, 94 EFL learners were asked to complete Reflective Thinking Questionnaire (Kember et al., 2000), Beliefs about Language Learning and Teaching Inventory (Horwitz, 1985), Strategy Inventory for Language Learning (Oxford, 1990), and Oxford Quick Placement Test. The results of three separate one-way ANOVAs indicated that reflective thinking significantly differentiates Iranian EFL learners concerning: (a)language learning strategy use, (b) beliefs about language learning and teaching, and (c) general language proficiency. Furthermore, to see where the differences lay, three separate post-hoc Tukey tests were run the results of which showed that learners with different levels of reflectivity (high, mid, and low) were significantly different from each other in all three dependent variables. Finally, to increase the validity of the findings thirty of the participants were interviewed and the results were analyzed through template organizing style method (Crabtree & Miller, 1999). The results of the interview analysis supported the results of quantitative data analysis.

Keywords: reflective thinking, language learning strategy use, beliefs toward language learning and teaching

Procedia PDF Downloads 656

Authors: Yog Raj Sood, Rajnish Shrivastava, Anchal Wadhwa

Abstract:

Power transformer is one of the electrical equipment that has a central and critical role in the power system. In order to avoid power transformer failure, information system that provides the transformer condition is needed. This paper presents an information system to know the exact situations prevailing within the transformer by declaring its health index. Health index of a transformer is decided by considering several diagnostic tools. The current work deals with UV-Vis, IFT, FP, BDV and Water Content. UV/VIS results have been pre-accessed using separate FL controller for concluding with the Furan contents. It is broadly accepted that the life of a power transformer is the life of the oil/ paper insulating system. The method relies on the use of furan analysis (insulation paper), and other oil analysis results as a means to declare health index. Fuzzy logic system is used to develop the information system. The testing is done on 5 samples of oil of transformers of rating 132/66 KV to obtain the results and results are analyzed using fuzzy logic model.

Keywords: interfacial tension analyzer (ift), flash point (fp), furfuraldehyde (fal), health index

Procedia PDF Downloads 636

Authors: H. Ozbasaran

Abstract:

IPN and IPE sections, which are commonly used European I shapes, are widely used in steel structures as cantilever beams to support overhangs. A considerable number of studies exist on calculating lateral torsional buckling load of I sections. However, most of them provide series solutions or complex closed-form equations. In this paper, a simple equation is presented to calculate lateral torsional buckling load of IPN and IPE section cantilever beams. First, differential equation of lateral torsional buckling is solved numerically for various loading cases. Then a parametric study is conducted on results to present an equation for lateral torsional buckling load of European IPN and IPE beams. Finally, results obtained by presented equation are compared to differential equation solutions and finite element model results. ABAQUS software is utilized to generate finite element models of beams. It is seen that the results obtained from presented equation coincide with differential equation solutions and ABAQUS software results. It can be suggested that presented formula can be safely used to calculate critical lateral torsional buckling load of European IPN and IPE section cantilevers.

Keywords: cantilever, IPN, IPE, lateral torsional buckling

Procedia PDF Downloads 541

Authors: Mostafa Zandi, Ramin Mansouri

Abstract:

Spillways are one of the most important hydraulic structures of dams that provide the stability of the dam and downstream areas at the time of flood. Morning-Glory spillway is one of the common spillways for discharging the overflow water behind dams, these kinds of spillways are constructed in dams with small reservoirs. In this research, the hydraulic flow characteristics of a morning-glory spillways are investigated with CFD model. Two dimensional unsteady RANS equations were solved numerically using Finite Volume Method. The PISO scheme was applied for the velocity-pressure coupling. The mostly used two-equation turbulence models, k- and k-, were chosen to model Reynolds shear stress term. The power law scheme was used for discretization of momentum, k , and  equations. The VOF method (geometrically reconstruction algorithm) was adopted for interface simulation. The results show that the fine computational grid, the input speed condition for the flow input boundary, and the output pressure for the boundaries that are in contact with the air provide the best possible results. Also, the standard wall function is chosen for the effect of the wall function, and the turbulent model k -ε (Standard) has the most consistent results with experimental results. When the jet is getting closer to end of basin, the computational results increase with the numerical results of their differences. The lower profile of the water jet has less sensitivity to the hydraulic jet profile than the hydraulic jet profile. In the pressure test, it was also found that the results show that the numerical values of the pressure in the lower landing number differ greatly in experimental results. The characteristics of the complex flows over a Morning-Glory spillway were studied numerically using a RANS solver. Grid study showed that numerical results of a 57512-node grid had the best agreement with the experimental values. The desired downstream channel length was preferred to be 1.5 meter, and the standard k-ε turbulence model produced the best results in Morning-Glory spillway. The numerical free-surface profiles followed the theoretical equations very well.

Keywords: morning-glory spillway, CFD model, hydraulic characteristics, wall function

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Authors: Shiva Kumar, G. S. Vijay, Srinivas Pai P., Shrinivasa Rao B. R.

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In the present study RBF neural networks were used for predicting the performance and emission parameters of a biodiesel engine. Engine experiments were carried out in a 4 stroke diesel engine using blends of diesel and Honge methyl ester as the fuel. Performance parameters like BTE, BSEC, Tech and emissions from the engine were measured. These experimental results were used for ANN modeling. RBF center initialization was done by random selection and by using Clustered techniques. Network was trained by using fixed and varying widths for the RBF units. It was observed that RBF results were having a good agreement with the experimental results. Networks trained by using clustering technique gave better results than using random selection of centers in terms of reduced MRE and increased prediction accuracy. The average MRE for the performance parameters was 3.25% with the prediction accuracy of 98% and for emissions it was 10.4% with a prediction accuracy of 80%.

Keywords: radial basis function networks, emissions, performance parameters, fuzzy c means

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Authors: A. Naamane, M. Hasnaoui

Abstract:

Numerical modeling of fluid flows, whether compressible or incompressible, laminar or turbulent presents a considerable contribution in the scientific and industrial fields. However, the development of an approximate model of a supersonic flow requires the introduction of specific and more precise techniques and methods. For this purpose, the object of this paper is modeling a supersonic flow of inviscid fluid around a dihedral airfoil. Based on the thin airfoils theory and the non-dimensional stationary Steichen equation of a two-dimensional supersonic flow in isentropic evolution, we obtained a solution for the downstream velocity potential of the oblique shock at the second order of relative thickness that characterizes a perturbation parameter. This result has been dealt with by the asymptotic analysis and characteristics method. In order to validate our model, the results are discussed in comparison with theoretical and experimental results. Indeed, firstly, the comparison of the results of our model has shown that they are quantitatively acceptable compared to the existing theoretical results. Finally, an experimental study was conducted using the AF300 supersonic wind tunnel. In this experiment, we have considered the incident upstream Mach number over a symmetrical dihedral airfoil wing. The comparison of the different Mach number downstream results of our model with those of the existing theoretical data (relative margin between 0.07% and 4%) and with experimental results (concordance for a deflection angle between 1° and 11°) support the validation of our model with accuracy.

Keywords: asymptotic modelling, dihedral airfoil, supersonic flow, supersonic wind tunnel

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Authors: A. A. Ahmadi, A. R. Pishevar, M. Nili

Abstract:

As the test gas in a gun tunnel is non-isentropically compressed and heated by a light weight piston. Here, first consideration is the optimum piston weight. Although various aspects of the influence of piston weight on gun tunnel performance have been studied, it is not possible to decide from the existing literature what piston weight is required for optimum performance in various conditions. The technique whereby the piston is rapidly brought to rest at the end of the gun tunnel barrel, and the resulted peak pressure is equal in magnitude to the final equilibrium pressure, is called the equilibrium piston technique. The equilibrium piston technique was developed to estimate the equilibrium piston mass; but this technique cannot give an appropriate estimate for the optimum piston weight. In the present work, a gun tunnel with diameter of 3 in. is described and its performance is investigated numerically to obtain the effect of piston and its weight. Numerical results in the present work are in very good agreement with experimental results. Significant influence of the existence of a piston is shown by comparing the gun tunnel results with results of a conventional shock tunnel in the same dimension and same initial condition. In gun tunnel, an increase of around 250% in running time is gained relative to shock tunnel. Also, Numerical results show that equilibrium piston technique is not a good way to estimate suitable piston weight and there will be a lighter piston which can increase running time of the gun tunnel around 60%.

Keywords: gun tunnel, hypersonic flow, piston, shock tunnel

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Authors: Z. Abdollahnejad, P. Torgal, J. Barroso Aguiar

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Publications on the field of alkali-activated binders, state that this new material is likely to have high potential to become an alternative to Portland cement. Classical alkali-activated cements could be made more eco-efficient if the use of sodium silicate is avoided. Besides, most alkali-activated cements suffer from severe efflorescence originated by the fact that alkaline and/or soluble silicates that are added during processing cannot be totally consumed. This paper presents experimental results on hybrid alkaline cements. Compressive strength results and efflorescence’s observations show that the new mixes already analyzed are promising. SEM results show that no traditional porous ITZ was detected in these binders.

Keywords: hybrid alkaline cements, compressive strength, efflorescence, SEM, ITZ

Procedia PDF Downloads 293

Authors: J. R. Wang, Y. Chiang, W. S. Hsu, H. C. Chen, S. H. Chen, J. H. Yang, S. W. Chen, C. Shih

Abstract:

In this study, the RASCAL and ALOHA codes are used to establish an analysis methodology for hydrogen fluoride (HF) evaluation. There are three main steps in this study. First, the UF₆ data were collected. Second, one postulated case was analyzed by using the RASCAL and UF₆ data. This postulated case assumes that fire occurring and UF₆ is releasing from a building. Third, the results of RASCAL for HF mass were as the input data of ALOHA. Two postulated cases of HF were analyzed by using ALOHA code and the results of RASCAL. These postulated cases assume fire occurring and HF is releasing with no raining (Case 1) or raining (Case 2) condition. According to the analysis results of ALOHA, the HF concentration of Case 2 is smaller than Case 1. The results can be a reference for the preparing of emergency plans for the release of HF.

Keywords: RASCAL, ALOHA, UF₆, hydrogen fluoride

Procedia PDF Downloads 751