Abstract: The present paper describes the study of paste tailings prepared in laboratory using gold tailings, produced in a Finnish gold mine with the incorporation of coal ash. Natural leaching tests were conducted with the original materials (tailings, fly and bottom ashes) and also with paste mixtures that were prepared with different percentages of tailings and ashes. After leaching, the solid wastes were physically and chemically characterized and the results were compared to those selected as blank – the unleached samples. The tailings and the coal ash, as well as the prepared mixtures, were characterized, in addition to the textural parameters, by the following measurements: grain size distribution, chemical composition and pH. Mixtures were also tested in order to characterize their mechanical behavior by measuring the flexural strength, the compressive strength and the consistency. The original tailing samples presented an alkaline pH because during their processing they were previously submitted to pressure oxidation with destruction of the sulfides. Therefore, it was not possible to ascertain the effect of the coal ashes in the acid mine drainage. However, it was possible to verify that the paste reactivity was affected mostly by the bottom ash and that the tailings blended with bottom ash present lower mechanical strength than when blended with a combination of fly and bottom ash. Surface paste disposal offer an attractive alternative to traditional methods in addition to the environmental benefits of incorporating large-volume wastes (e.g. bottom ash). However, a comprehensive characterization of the paste mixtures is crucial to optimize paste design in order to enhance engineer and environmental properties.
Abstract: Rendering light shafts is one of the important topics in computer gaming and interactive applications. The methods and models that are used to generate light shafts play crucial role to make a scene more realistic in computer graphics. This article discusses the image-based shadows and geometric-based shadows that contribute in generating volumetric shadows and light shafts, depending on ray tracing, radiosity, and ray marching technique. The main aim of this study is to provide researchers with background on a progress of light scattering methods so as to make it available for them to determine the technique best suited to their goals. It is also hoped that our classification helps researchers find solutions to the shortcomings of each method.
Abstract: The underlying principle behind the harmonization in international education does not solely aim for the comparability but also the compatibility of outputs produced. The international standard in the different professions particularly in engineering defines the required graduate attributes to attain suitable qualifications and recognitions. This study described the language practices of the Electronics Engineering students of Bulacan State University, Philippines who will be deployed for their internship program. The purpose of the study was achieved by determining the language proficiency of the students in terms of speaking, listening, reading, and writing, and checking the adherence of the University to the commitment of intensifying community building for the Association of Southeast Asian Nation Vision 2020. The analysis of variance of the variables defined the significance between the causal variables and dependent variables. Thus, this study identified the mechanism that would regulate language practices in the Electronics Engineering program.
Abstract: The traction behavior of lubricants with the linear pressure-viscosity response in EHL line contacts is investigated numerically for smooth as well as rough surfaces. The analysis involves the simultaneous solution of Reynolds, elasticity and energy equations along with the computation of lubricant properties and surface temperatures. The temperature modified Doolittle-Tait equations are used to calculate viscosity and density as functions of fluid pressure and temperature, while Carreau model is used to describe the lubricant rheology. The surface roughness is assumed to be sinusoidal and it is present on the nearly stationary surface in near-pure sliding EHL conjunction. The linear P-V oil is found to yield much lower traction coefficients and slightly thicker EHL films as compared to the synthetic oil for a given set of dimensionless speed and load parameters. Besides, the increase in traction coefficient attributed to surface roughness is much lower for the former case. The present analysis emphasizes the importance of employing realistic pressure-viscosity response for accurate prediction of EHL traction.
Abstract: This paper aims at assessing the concentrations of heavy metals and the isotopic composition of lead 210Pb in different fractions of sediment produced in the watershed that makes up the Mãe d'água dam and thus characterizing the distribution of metals along the sedimentary column and inferencing in the urbanization of the same process. Sample collection was carried out in June 2014; eight sediment cores were sampled in the lake of the dam. For extraction of the sediments core, a core sampler “Piston Core” was used. The trace metal concentrations were determined by conventional atomic absorption spectrophotometric methods. The samples were subjected to radiochemical analysis of 210Po. 210Pb activity was obtained by measuring 210Po activity. The chronology was calculated using the constant rate of supply (CRS). 210Pb is used to estimate the sedimentation rate.
Abstract: Zymomonas mobilis is known as an example of the
uncoupled growth phenomenon. This microorganism also has a
unique metabolism that degrades glucose by the Entner–Doudoroff
(ED) pathway. In this paper, a genome-scale metabolic model
including 434 genes, 757 reactions and 691 metabolites was
reconstructed to simulate uncoupled growth and study its effect on
flux distribution in the central metabolism. The model properly
predicted that ATPase was activated in experimental growth yields of
Z. mobilis. Flux distribution obtained from model indicates that the
major carbon flux passed through ED pathway that resulted in the
production of ethanol. Small amounts of carbon source were entered
into pentose phosphate pathway and TCA cycle to produce biomass
precursors. Predicted flux distribution was in good agreement with
experimental data. The model results also indicated that Z. mobilis
metabolism is able to produce biomass with maximum growth yield
of 123.7 g (mol glucose)-1 if ATP synthase is coupled with growth
and produces 82 mmol ATP gDCW-1h-1. Coupling the growth and
energy reduced ethanol secretion and changed the flux distribution to
produce biomass precursors.
Abstract: Prediction of perturbations after genetic manipulation
(especially gene knockout) is one of the important challenges in
systems biology. In this paper, a new algorithm is introduced that
integrates microarray data into the metabolic model. The algorithm
was used to study the change in the cell phenotype after knockout of
Gss gene in Escherichia coli BW25113. Algorithm implementation
indicated that gene deletion resulted in more activation of the
metabolic network. Growth yield was more and less regulating gene
were identified for mutant in comparison with the wild-type strain.
Abstract: This paper describes the design process of a 200 MHz Ground Penetrating Radar (GPR) and a battery powered concrete vertical concrete surface climbing mobile robot. The key design feature is a miniaturized 200 MHz dipole antenna using additional radiating arms and procedure records a reduction of 40% in length compared to a conventional antenna. The antenna set is mounted in front of the robot using a servo mechanism for folding and unfolding purposes. The robot’s adhesion mechanism to climb the reinforced concrete wall is based on neodymium permanent magnets arranged in a unique combination to concentrate and maximize the magnetic flux to provide sufficient adhesion force for GPR installation. The experiments demonstrated the robot’s capability of climbing reinforced concrete wall carrying the attached prototype GPR system and perform floor-to-wall transition and vice versa. The developed GPR’s performance is validated by its capability of detecting and localizing an aluminium sheet and a reinforcement bar (rebar) of 12 mm diameter buried under a test rig built of wood to mimic the concrete structure environment. The present robotic GPR system proves the concept of feasibility of undertaking inspection procedure on large concrete structures in hazardous environments that may not be accessible to human inspectors.
Abstract: In this paper, we consider a drift flux mixture model of the blood flow. The mixture consists of gas phase which is carbon dioxide and liquid phase which is an aqueous carbon dioxide solution. This model was used to determine the distributions of the mixture velocity, the mixture pressure, and the carbon dioxide pressure. These theoretical data are used to determine a measurement method of mean gas pressure through the determination of radial velocity distribution. This method can be applicable in experimental domain.
Abstract: This study describes undergraduate casual-leisure information behaviors relevant to online videos. Diaries and in-depth interviews were used to collect data. Twenty-four undergraduates participated in this study (9 men, 15 women; all were aged 18–22 years). This study presents a model of casual-leisure information behaviors and contributes new insights into user experience in casual-leisure settings, such as online video programs, with implications for other information domains.
Abstract: The impact that urban green spaces have on sustainability and quality of life is phenomenal. This is also true for the local South African environment. However, in reality green spaces in urban environments are decreasing due to growing populations, increasing urbanization and development pressure. This further impacts on the provision of child-friendly spaces, a concept that is already limited in local context. Child-friendly spaces are described as environments in which people (children) feel intimately connected to, influencing the physical, social, emotional, and ecological health of individuals and communities. The benefits of providing such spaces for the youth are well documented in literature. This research therefore aimed to investigate the concept of child-friendly spaces and its applicability to the South African planning context, in order to guide the planning of such spaces for future communities and use. Child-friendly spaces in the urban environment of the city of Durban, was used as local case study, along with two international case studies namely Mullerpier public playground in Rotterdam, the Netherlands, and Kadidjiny Park in Melville, Australia. The aim was to determine how these spaces were planned and developed and to identify tools that were used to accomplish the goal of providing successful child-friendly green spaces within urban areas. The need and significance of planning for such spaces was portrayed within the international case studies. It is confirmed that minimal provision is made for green space planning within the South African context, when there is reflected on the international examples. As a result international examples and disciples of providing child-friendly green spaces should direct planning guidelines within local context. The research concluded that child-friendly green spaces have a positive impact on the urban environment and assist in a child’s development and interaction with the natural environment. Regrettably, the planning of these child-friendly spaces is not given priority within current spatial plans, despite the proven benefits of such.
Abstract: In the field of production, characterization of surface
roughness plays a vital role in assessing the quality of a manufactured
product. The defined parameters for this assessment, each, have their
own drawbacks in describing a profile surface. From the purview of
small-scale and medium-scale industries, an increase in time spent for
manual inspection of a product for various parameters adds to the
cost of the product. In order to reduce this, a uniform and established
standard is necessary for quantifying a profile of a manufactured
product. The inspection procedure in the small and medium-scale
manufacturing units at Jigani Industrial area, Bangalore, was
observed. The parameters currently in use in those industries are
described in the paper and a change in the inspection method is
proposed.
Abstract: Knowledge management (KM) literature has mainly focused on the antecedents of KM. The purpose of this study is to investigate the effect of specific human resource management (HRM) practices on employee knowledge sharing and its outcome as individual knowledge capability. Based on previous literature, a model is proposed for the study and hypotheses are formulated. The cross-sectional dataset comes from a sample of 19 knowledge intensive firms (KIFs). This study has run an item parceling technique followed by Confirmatory Factor Analysis (CFA) on the latent constructs of the research model. Employees’ collaboration and their interpersonal trust can help to improve their knowledge sharing behaviour and knowledge capability within organisations. This study suggests that in future, by using a larger sample, better statistical insight is possible. The findings of this study are beneficial for scholars, policy makers and practitioners. The empirical results of this study are entirely based on employees’ perceptions and make a significant research contribution, given there is a dearth of empirical research focusing on the subcontinent.
Abstract: The present work aims at contributing to the study of the complex phenomenon of wear of pin on disc contact in dry sliding friction between two material couples (bronze/steel and unsaturated polyester virgin and charged with graphite powder/steel). The work consists of the determination of the coefficient of friction, the study of the influence of the tribological parameters on this coefficient and the determination of the mass loss and the wear rate of the pin. This study is also widened to the highlighting of the influence of the addition of graphite powder on the tribological properties of the polymer constituting the pin. The experiments are carried out on a pin-disc type tribometer that we have designed and manufactured. Tests are conducted according to the standards DIN 50321 and DIN EN 50324. The discs are made of annealed XC48 steel and quenched and tempered XC48 steel. The main results are described here after. The increase of the normal load and the sliding speed causes the increase of the friction coefficient, whereas the increase of the percentage of graphite and the hardness of the disc surface contributes to its reduction. The mass loss also increases with the normal load. The influence of the normal load on the friction coefficient is more significant than that of the sliding speed. The effect of the sliding speed decreases for large speed values. The increase of the amount of graphite powder leads to a decrease of the coefficient of friction, the mass loss and the wear rate. The addition of graphite to the UP resin is beneficial; it plays the role of solid lubricant.
Abstract: This paper studies a secondary voltage control
framework of the microgrids based on the consensus for a
communication network of multiagent. The proposed control is
designed by the communication network with one-way links. The
communication network is modeled by a directed graph. At this
time, the concept of sampling is considered as the communication
constraint among each distributed generator in the microgrids. To
analyze the sampling effects on the secondary voltage control of
the microgrids, by using Lyapunov theory and some mathematical
techniques, the sufficient condition for such problem will be
established regarding linear matrix inequality (LMI). Finally, some
simulation results are given to illustrate the necessity of the
consideration of the sampling effects on the secondary voltage control
of the microgrids.
Abstract: A hybrid energy system is a combination of renewable energy sources with back up, as well as a storage system used to respond to given load energy requirements. Given that the electrical output of each renewable source is fluctuating with changes in weather conditions, and since the load demand also varies with time; one of the main attributes of hybrid systems is to be able to respond to the load demand at any time by optimally controlling each energy source, storage and back-up system. The induced optimization problem is to compute the optimal operation control of the system with the aim of minimizing operation costs while efficiently and reliably responding to the load energy requirement. Current optimization research and development on hybrid systems are mainly focusing on the sizing aspect. Thus, the aim of this paper is to report on the state-of-the-art of optimal operation control of hybrid renewable energy systems. This paper also discusses different challenges encountered, as well as future developments that can help in improving the optimal operation control of hybrid renewable energy systems.
Abstract: Abstract—Attribute or feature selection is one of the basic
strategies to improve the performances of data classification tasks,
and, at the same time, to reduce the complexity of classifiers,
and it is a particularly fundamental one when the number
of attributes is relatively high. Its application to unsupervised
classification is restricted to a limited number of experiments in
the literature. Evolutionary computation has already proven itself
to be a very effective choice to consistently reduce the number
of attributes towards a better classification rate and a simpler
semantic interpretation of the inferred classifiers. We present a feature
selection wrapper model composed by a multi-objective evolutionary
algorithm, the clustering method Expectation-Maximization (EM),
and the classifier C4.5 for the unsupervised classification of data
extracted from a psychological test named BASC-II (Behavior
Assessment System for Children - II ed.) with two objectives:
Maximizing the likelihood of the clustering model and maximizing
the accuracy of the obtained classifier. We present a methodology
to integrate feature selection for unsupervised classification, model
evaluation, decision making (to choose the most satisfactory model
according to a a posteriori process in a multi-objective context), and
testing. We compare the performance of the classifier obtained by the
multi-objective evolutionary algorithms ENORA and NSGA-II, and
the best solution is then validated by the psychologists that collected
the data.
Abstract: More PV systems have been connected to the electrical network each year. As the number of PV systems increases, some issues affecting grid operations have been identified. This paper studied the impacts related to changes in solar irradiance on a distribution/sub-transmission network, considering variations due to moving clouds and daily cycles. Using MATLAB/Simulink software, a solar farm of 30 MWp was built and then implemented to a test network. From simulations, it has been determined that irradiance changes can have a significant impact on the grid by causing voltage fluctuations outside the allowable thresholds. This work discussed some local control strategies and grid reinforcements to mitigate the negative effects of the irradiance changes on the grid.
Abstract: The study was designed to examine the barriers to marital expectations among unmarried persons with hearing impairment in Oyo State, Nigeria. Descriptive survey research design was adopted. Purposive sampling technique was used to select one hundred participants made up forty-four (44) males and fifty-six (56) females, all with varying degrees of hearing impairment. Eight research questions were raised and answered. The instrument used was Marital Expectations Scale with reliability coefficient of 0.86. Data was analyzed using descriptive statistics tools of frequency count and simple percentage as well as inferential statistics tools of T-TEST and ANOVA. The findings revealed that there was a significant relationship existing among the main identified barriers (environmental barrier, communication barrier, hearing loss, unemployment and poor sexuality education) to the marital expectations of unmarried persons with hearing impairment. The joint contribution of the independent variables (identified barriers) to the dependent variable (marital expectations) was significant, F = 5.842, P < 0.05, accounting for about 89% of the variance. The relative contribution of the identified barriers to marital expectations of unmarried persons with hearing impairment is as follows: environmental barrier (β = 0.808, t = 5.176, P < 0.05), communication barrier (β = 0.533, t = 3.305, P < 0.05), hearing loss (β = 0.550, t = 2.233, P < 0.05), unemployment (β = 0.431, t = 2.102, P < 0.05), poor sexuality education (β = 0.361, t = 1.985, P < 0.05). Environmental barrier proved to be the most potent contributor to the poor marital expectations among unmarried persons with hearing impairment. Therefore, it is recommended that society dismantles the nagging environmental barrier through positive identification with individuals suffering from hearing impairment. In this connection, members of society should change their negative attitudes and do away with all the wrong notions about the marital ability of individuals with hearing impairment.
Abstract: Functional electrical stimulation (FES) is a commonly used technique in rehabilitation and often associated with rapid muscle fatigue which becomes the limiting factor in its applications. The objective of this study is to investigate the effects on the onset of fatigue of conventional synchronous stimulation, as well as asynchronous stimulation that mimic voluntary muscle activation targeting different motor units which are activated sequentially or randomly via multiple pairs of stimulation electrodes. We investigate three different approaches with various electrode configurations, as well as different patterns of stimulation applied to the gastrocnemius muscle: Conventional Synchronous Stimulation (CSS), Asynchronous Sequential Stimulation (ASS) and Asynchronous Random Stimulation (ARS). Stimulation was applied repeatedly for 300 ms followed by 700 ms of no-stimulation with 40 Hz effective frequency for all protocols. Ten able-bodied volunteers (28±3 years old) participated in this study. As fatigue indicators, we focused on the analysis of Normalized Fatigue Index (NFI), Fatigue Time Interval (FTI) and pre-post Twitch-Tetanus Ratio (ΔTTR). The results demonstrated that ASS and ARS give higher NFI and longer FTI confirming less fatigue for asynchronous stimulation. In addition, ASS and ARS resulted in higher ΔTTR than conventional CSS. In this study, we proposed a randomly distributed stimulation method for the application of FES and investigated its suitability for reducing muscle fatigue compared to previously applied methods. The results validated that asynchronous stimulation reduces fatigue, and indicates that random stimulation may improve fatigue resistance in some conditions.