Search results for: theoretical calculations

Authors: Youmen Chaaban

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The study examined the influence of a situated professional development program (PD) aimed at enhancing English language teachers’ knowledge and skills and improving their instructional practices. The PD model under examination was developed upon sound theoretical underpinnings, taking into consideration research-based principles of effective PD. However, the implementation of the PD model within several school contexts required further investigation from the perspectives of the teachers, who were receiving the PD activities, and the instructional coaches, who were providing them. The paper, thus, presents the results of a qualitative study examining the perceptions of seventeen English language teachers and nineteen instructional coaches about the strengths of the PD program, the challenges they faced in the implementation of the program, and their suggestions for the improvement of the program’s implementation and outcomes. Comparisons were further made between the two groups of participants to uncover agreements and contradictions in their perceptions. Data were collected from the teachers through in-depth interviews and observations, while the data collected from the instructional coaches were open-ended surveys followed by focus group interviews. The findings of the study confirm the necessity of structuring PD activities around sound theoretical underpinnings. However, practical considerations specific to the contexts where the PD activities take place should be considered when evaluating the PD’s effectiveness. Finally, the study provides several recommendations for maximizing the influence of the PD program on teachers’ practices and beliefs.

Keywords: English language teachers, situated professional development, teacher beliefs, teacher practices

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Authors: Yskak Nabi, Onolkan Umankulova, Ilyas Seitov

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Tempus project about “Central Asian network for quality assurance – CANQA” had been implemented in 2009-2012. As the result of the project, two accreditation agencies were established: the agency for quality assurance in the field of education, “EdNet” in Kyrgyzstan, center of progressive technologies in Tajikistan. The importance of the research studies of the project is supported by the idea that the creation of Central-Asian network for quality assurance in education is still relevant, and results of the International forum “Global in regional: Kazakhstan in Bologna process and EU projects,” that was held in Nur-Sultan in October 2020, proves this. At the same time, the previous experience of the partnership between accreditation agencies of Central Asia shows that recommendations elaborated within the CANQA project were not theoretically justified. But there are a number of facts and arguments that prove the practical appliance of these recommendations. In this respect, joint activities of accreditation agencies of Kyrgyzstan and Kazakhstan are representative. For example, independent Kazakh agency of accreditation and rating successfully conducts accreditation of Kyrgyz universities; based on the memorandum about joint activity between the agency for quality assurance in the field of education “EdNet” (Kyrgyzstan) and Astana accreditation agency (Kazakhstan), the last one provides its experts for accreditation procedures in EdNet. Exchange of experience among the agencies shows an effective approach towards adaptation of European standards to the reality of education systems of Central Asia with consideration of not only a legal framework but also from the point of European practices view. Therefore, the relevance of the research is identified as there is a practical partnership between accreditation agencies of Central Asian countries, but the absence of theoretical justification of integrational processes in the accreditation field. As a result, the following hypothesis was put forward: “if to develop theoretical aspects for harmonization of accreditation standards, then integrational processes would be improved since the implementation of Bologna process principles would be supported with wider possibilities, and particularly, students and academic mobility would be improved.” Indeed, for example, in Kazakhstan, the total share of foreign students was 5,04% in 2020, and most of them are coming from Kyrgyzstan, Tajikistan, and Uzbekistan, and if integrational processes will be improved, then this share can increase.

Keywords: accreditation standards in education, Central Asian countries, pedagogical theory, model

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Authors: R. A. Petre, S. E. Nichifor, A. Craifaleanu, I. Stroe

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The relative motion of a robotic arm formed by homogeneous bars of different lengths and masses, hinged to each other is investigated. The first bar of the mechanism is articulated on a platform, considered initially fixed on the surface of the Earth, while for the second case the platform is considered to be in rotation with respect to the Earth. For both analyzed cases the motion equations are determined using the Lagrangian formalism, applied in its traditional form, valid with respect to an inertial reference system, conventionally considered as fixed. However, in the second case, a generalized form of the formalism valid with respect to a non-inertial reference frame will also be applied. The numerical calculations were performed using a MATLAB program.

Keywords: Lagrange equations, relative motion, inertial reference frame, non-inertial reference frame

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Authors: Jonathan D. Moore, Mark G. Reith, David S. Long

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Serious games (SGs) have been shown to be an effective teaching tool in many contexts. Because of the success of SGs, several design frameworks have been created to expedite the process of making original serious games to teach specific learning objectives (LOs). Even with these frameworks, the time required to create a custom SG from conception to implementation can range from months to years. Furthermore, it is even more difficult to design a game framework that allows an instructor to create customized game variants supporting multiple LOs within the same field. This paper proposes a refactoring methodology to apply the theoretical principles from well-established design frameworks to a pre-existing serious game. The expected result is a generalized game that can be quickly customized to teach LOs not originally targeted by the game. This methodology begins by describing the general components in a game, then uses a combination of two SG design frameworks to extract the teaching elements present in the game. The identified teaching elements are then used as the theoretical basis to determine the range of LOs that can be taught by the game. This paper evaluates the proposed methodology by presenting a case study of refactoring the serious game Battlespace Next (BSN) to teach joint military capabilities. The range of LOs that can be taught by the generalized BSN are identified, and examples of creating custom LOs are given. Survey results from users of the generalized game are also provided. Lastly, the expected impact of this work is discussed and a road map for future work and evaluation is presented.

Keywords: serious games, learning objectives, game design, learning theory, game framework

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Authors: Andrew J. Zacharias

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The forest garden approach (FGA) was established by Trees for the Future (TREES) over the organization’s 30 years of agroforestry projects in Sub-Saharan Africa. This method transforms traditional agricultural systems into highly managed gardens that produce food and marketable products year-round. The effects of the FGA on food security, dietary diversity, and economic resilience have been measured closely, and TREES has begun to closely monitor the environmental impacts through the use of sensors mounted on unmanned aerial vehicles, commonly known as 'drones'. These drones collect thousands of pictures to create 3-D models in both the visible and the near-infrared wavelengths. Analysis of these models provides TREES with quantitative and qualitative evidence of improvements to the annual above-ground biomass and leaf area indices, as measured in-situ using NDVI calculations.

Keywords: agroforestry, biomass, drones, NDVI

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Authors: Jiahui Yang, John Quigley, Lesley Walls

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In this paper, the authors develop a stochastic model regarding the investment in supplier delivery performance development from a buyer’s perspective. The authors propose a multivariate model through a Multinomial-Dirichlet distribution within an Empirical Bayesian inference framework, representing both the epistemic and aleatory uncertainties in deliveries. A closed form solution is obtained and the lower and upper bound for both optimal investment level and expected profit under uncertainty are derived. The theoretical properties provide decision makers with useful insights regarding supplier delivery performance improvement problems where multiple delivery statuses are involved. The authors also extend the model from a single supplier investment into a supplier portfolio, using a Lagrangian method to obtain a theoretical expression for an optimal investment level and overall expected profit. The model enables a buyer to know how the marginal expected profit/investment level of each supplier changes with respect to the budget and which supplier should be invested in when additional budget is available. An application of this model is illustrated in a simulation study. Overall, the main contribution of this study is to provide an optimal investment decision making framework for supplier development, taking into account multiple delivery statuses as well as multiple projects.

Keywords: decision making, empirical bayesian, portfolio optimization, supplier development, supply chain management

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Authors: Mokdad Sakhri, Youcef Bouhadda

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Thin film chalcopyrite technology is thus nowadays a solid candidate for photovoltaic cells. The currently used window layer for the solar cell Cu(In,Ga)S2 is our interest point in this work. For this purpose, we have performed a first-principles study of structural, electronic and optical properties for both delafossite transparent conductive oxides Cu (In, Ga)O2 and absorbers films Cu(In,Ga)S2. The calculations have been carried out within the local density functional (LDA) and generalized gradient approximations (GGA) combined with the hubbard potential using norm-conserving pseudopotentials and a plane-wave basis with ABINIT code. We have found the energy gap is :1.6, 2.53, 3.6, 3.8 eV for CuInS2, CuGaS2, CuInO2 and CuGaO2 respectively. The results are in good agreement with experimental results.

Keywords: ABINIT code, DFT, electronic and optical properties, solar-cell absorbers, delafossite transparent conductive oxides

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Authors: Moussa Hamdan, Abdulati Abdullah

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This paper presents an investigation of the fabrication of the optical devices in terms of their characteristics based on the use of the electromagnetic waves. Planar waveguides are used to examine the field modes (bound modes) and the parameters required for this structure. The modifications are conducted on surface plasmons based waveguides. Simple symmetric dielectric slab structure is used and analyzed in terms of transverse electric mode (TE-Mode) and transverse magnetic mode (TM-Mode. The paper presents mathematical and numerical solutions for solving simple symmetric plasmons and provides simulations of surface plasmons for field confinement. Asymmetric TM-mode calculations for dielectric surface plasmons are also provided.

Keywords: surface plasmons, optical waveguides, semiconductor lasers, refractive index, slab dialectical

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Authors: Magdalena Grudzińska

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Passive systems allow solar radiation to be converted into thermal energy thanks to appropriate building construction. Greenhouse systems are particularly worth attention, due to the low costs of their realization and strong architectural appeal. The paper discusses the energy effects of using passive greenhouse systems, such as glazed balconies, in an example residential building. The research was carried out for five localities in Poland, belonging to climatic zones different in terms of external air temperature and insolation: Koszalin, Poznań, Lublin, Białystok and Zakopane The analysed apartment had a floor area of approximately 74 m² Three thermal zones were distinguished in the flat - the balcony, the room adjacent to it, and the remaining space, for which various internal conditions were defined. Calculations of the energy demand were made using the dynamic simulation program, based on the control volume method. The climatic data were represented by Typical Meteorological Years, prepared on the basis of source data collected from 1971 to 2000. In each locality, the introduction of a passive greenhouse system led to a lower demand for heating in the apartment, and the shortening of the heating season. The smallest effectiveness of passive solar energy systems was noted in Białystok. Demand for heating was reduced there by 14.5% and the heating season remained the longest, due to low temperatures of external air and small sums of solar radiation intensity. In Zakopane, energy savings came to 21% and the heating season was reduced to 107 days, thanks to the greatest insolation during winter. The introduction of greenhouse systems caused an increase in cooling demand in the warmer part of the year, but total energy demand declined in each of the discussed places. However, potential energy savings are smaller if the building's annual life cycle is taken into consideration, and amount from 5.6% up to 14%. Koszalin and Zakopane are localities in which the greenhouse system allows the best energy results to be achieved. It should be emphasized that favourable conditions for introducing greenhouse systems are connected with different climatic conditions. In the seaside area (Koszalin) they result from high temperatures in the heating season and the smallest insolation in the summer period, while in the mountainous area (Zakopane) they result from high insolation in the winter and low temperatures in the summer. In the region of middle and middle-eastern Poland active systems (such as solar energy collectors or photovoltaic panels) could be more beneficial, due to high insolation during summer. It is assessed that passive systems do not eliminate the need for traditional heating in Poland. They can, however, substantially contribute to lower use of non-renewable fuels and the shortening of the heating season. The calculations showed diversification in the effectiveness of greenhouse systems resulting from climatic conditions, and allowed to identify areas which are the most suitable for the passive use of solar radiation.

Keywords: solar energy, passive greenhouse systems, glazed balconies, climatic conditions

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Authors: Hajer Habib, Ghazi Boulila

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The objective of this paper is to present our contribution to the theoretical literature through a simple theoretical model dealing with the effect of transferring funds on the labor market of the countries of origin and on the other hand to test this relationship empirically in the case of Tunisia. The methodology used consists of estimating a panel of the nine main destinations of the Tunisian diaspora in Europe between 1994 and 2014 in order to better value the net effect of these migratory financial flows on unemployment through population growth. The empirical results show that the main factors explaining the decision to emigrate are the economic factors related mainly to the income differential, the demographic factors related to the differential age structure of the origin and host populations, and the cultural factors linked basically to the mastery of the language. Indeed, the stock of migrants is one of the main determinants of the transfer of migratory funds to Tunisia. But there are other variables that do not lack importance such as the economic conditions linked by the host countries. This shows that Tunisian migrants react more to economic conditions in European countries than in Tunisia. The economic situation of European countries dominates the numbers of emigrants as an explanatory factor for the amount of transfers from Tunisian emigrants to their country of origin. Similarly, it is clear that there is an indirect effect of transfers on unemployment in Tunisia. This suggests that the demographic transition conditions the effects of transferring funds on the level of unemployment.

Keywords: demographic changes, international migration, labor market, remittances

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Authors: Alexander E. Hramov, Vadim V. Grubov, Alexey A. Koronovskii, Maria K. Kurovskaуa, Anastasija E. Runnova

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The perception of visual signals in the brain was among the first issues discussed in terms of multistability which has been introduced to provide mechanisms for information processing in biological neural systems. In this work the influence of the cognitive noise on the visual perception of multistable pictures has been investigated. The study includes an experiment with the bistable Necker cube illusion and the theoretical background explaining the obtained experimental results. In our experiments Necker cubes with different wireframe contrast were demonstrated repeatedly to different people and the probability of the choice of one of the cubes projection was calculated for each picture. The Necker cube was placed at the middle of a computer screen as black lines on a white background. The contrast of the three middle lines centered in the left middle corner was used as one of the control parameter. Between two successive demonstrations of Necker cubes another picture was shown to distract attention and to make a perception of next Necker cube more independent from the previous one. Eleven subjects, male and female, of the ages 20 through 45 were studied. The choice of the Necker cube projection was detected with the Electroencephalograph-recorder Encephalan-EEGR-19/26, Medicom MTD. To treat the experimental results we carried out theoretical consideration using the simplest double-well potential model with the presence of noise that led to the Fokker-Planck equation for the probability density of the stochastic process. At the first time an analytical solution for the probability of the selection of one of the Necker cube projection for different values of wireframe contrast have been obtained. Furthermore, having used the results of the experimental measurements with the help of the method of least squares we have calculated the value of the parameter corresponding to the cognitive noise of the person being studied. The range of cognitive noise parameter values for studied subjects turned to be [0.08; 0.55]. It should be noted, that experimental results have a good reproducibility, the same person being studied repeatedly another day produces very similar data with very close levels of cognitive noise. We found an excellent agreement between analytically deduced probability and the results obtained in the experiment. A good qualitative agreement between theoretical and experimental results indicates that even such a simple model allows simulating brain cognitive dynamics and estimating important cognitive characteristic of the brain, such as brain noise.

Keywords: bistability, brain, noise, perception, stochastic processes

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Authors: Naira Hakobyan, Shant Bagratyan

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This paper explores the phenomenon of management of innovations from the standpoint of work motivation. The main purpose of the theoretical research is to reveal the role of management of innovations to overcome the destructive work motivation and anomie. Systematization of the theoretical approaches and the literary sources indicates connections between destructive forms of work motivation and anomie. These connections allow an understanding of the role of innovations dedicated to decrease the motivational destructiveness of the employees. It is important to note that, in general, the presence of destructive motivation among employees can lead to work anomie. At the same time, issues related to the influence of destructive motivation on innovative processes in the management of an organization are not sufficiently studied. Exploring the factors leading to destructive work motivation and anomie manages toolkit and innovative ways of solution of the motivational destructiveness. The relevance of this scientific issue is that motivational destructiveness and work anomie are widespread phenomena in modern society. It means that previous forms of management become unusable and the way to introduce the innovations seems unclear for the employees. Investigation of the phenomenon of management of innovations is carried out in the following logical sequence: firstly, the issues of destructive work motivation and leadership are considered, and then the key points of work anomie are presented. Finally, there are explored the modern trends in the management of innovations aimed at overcoming motivational destructiveness and work anomie. The issue of management of innovations is explored by two levels: external-social and internal-organizational levels. Considering the phenomenon of management of innovations, the motivational role of the innovations is emphasized. The object of the research is the phenomenon of management of innovations in the context of overcoming motivational and anomic destructiveness. The paper presents the results of the theoretical analysis of the main factors of destructive motivation and work anomie among employees: an excessive dependence of employees on the manager, ignorance of one’s own work functions or unreasonable change by the manager, prevalence of formalism in assessing work comparing with the content and quality of work, lack of adaptive interaction among employees and low self-esteem of work activity. The paper theoretically proves that unclearly formulated innovative strategies for the development of the organization, lack of feedback from the manager to employees regarding the discussion of innovative technologies, non-compliance of working conditions with declared norms and standards, and formalism in management of innovations lead to destructiveness in a management system. The results of the research can be useful for managers, sociologists, economists, and psychologists.

Keywords: management of innovations, destructive motivation, work anomie, leadership, workaholism

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Authors: Seok Hong Min, Tae Kwon Ha

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With the increasing interest on Ti alloys, the extraction process of Ti from its typical ore, TiO₂, has long been and will be important issue. As an intermediate product for the production of pigment or titanium metal sponge, tetrachloride (TiCl₄) is produced by fluidized bed using high TiO₂ feedstock. The purity of TiCl₄ after chlorination is subjected to the quality of the titanium feedstock. Since the impurities in the TiCl₄ product are reported to final products, the purification process of the crude TiCl₄ is required. The purification process includes fractional distillation and chemical treatment, which depends on the nature of the impurities present and the required quality of the final product. In this study, thermodynamic analysis on the impurity effect in the chlorination process, which is the first step of extraction of Ti from TiO₂, has been conducted. All thermodynamic calculations were performed using the FactSage thermodynamical software.

Keywords: rutile, titanium, chlorination process, impurities, thermodynamic calculation, FactSage

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Authors: Ahmed M. Mansour, Ali M. El-Sawy, Ahmed T. Sayed

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Logarithms reduce products to sums and powers to products; they play an important role in signal processing, communication and information theory. They are primarily used for hardware calculations, handling multiplications, divisions, powers, and roots effectively. There are three commonly used bases for logarithms; the logarithm with base-10 is called the common logarithm, the natural logarithm with base-e and the binary logarithm with base-2. This paper demonstrates different methods of calculation for log2 showing the complexity of each and finds out the most accurate and efficient besides giving in- sights to their hardware design. We present a new method called Floor Shift for fast calculation of log2, and then we combine this algorithm with Taylor series to improve the accuracy of the output, we illustrate that by using two examples. We finally compare the algorithms and conclude with our remarks.

Keywords: logarithms, log2, floor, iterative, CORDIC, Taylor series

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Authors: Attila Vámosi, Tamás Mankovits, Dávid Huri, Imre Kocsis, Tamás Szabó

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Non-linear FEM calculations are indispensable when important technical information like operating performance of a rubber component is desired. Rubber bumpers built into air-spring structures may undergo large deformations under load, which in itself shows non-linear behavior. The changing contact range between the parts and the incompressibility of the rubber increases this non-linear behavior further. The material characterization of an elastomeric component is also a demanding engineering task. The shape optimization problem of rubber parts led to the study of FEM based calculation processes. This type of problems was posed and investigated by several authors. In this paper the time demand of certain calculation methods are studied and the possibilities of time reduction is presented.

Keywords: rubber bumper, data acquisition, finite element analysis, support vector regression

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Authors: Janet B. Badong-Badilla

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In Jesuit universities, laypersons, who come from the same or different faith backgrounds or traditions, are considered as collaborators in mission. The Jesuits themselves support the contributions of the lay partners in realizing the mission of the Society of Jesus and recognize the important role that they play in education. This study aims to investigate and generate particular notions and understandings of lived experiences of being a lay partner in Jesuit universities in the Philippines, particularly those involved in higher education. Using the qualitative approach as introduced by grounded theorist Barney Glaser, the lay partners’ concept of being a partner, as lived in higher education, is generated systematically from the data collected in the field primarily through in-depth interviews, field notes and observations. Glaser’s constant comparative method of analysis of data is used going through the phases of open coding, theoretical coding, and selective coding from memoing to theoretical sampling to sorting and then writing. In this study, Glaser’s grounded theory as a methodology will provide a substantial insight into and articulation of the layperson’s actual experience of being a partner of the Jesuits in education. Such articulation provides a phenomenological approach or framework to an understanding of the meaning and core characteristics of Jesuit-Lay partnership in Jesuit educational institution of higher learning in the country. This study is expected to provide a framework or model for lay partnership in academic institutions that have the same practice of having lay partners in mission.

Keywords: grounded theory, Jesuit mission in higher education, lay partner, lived experience

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Authors: Dries Dulsster

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This research we want to discuss the implications of the concept of ‘lalangue’ and illustrate its importance for lacanian psychoanalysis and its clinical practice. We will look at this concept through an in depth reading of Lacan’s later seminars, his lectures at the North-American universities and his study on James Joyce. We will illustrate the importance of this concept with a case study from a clinical practice. We will argue that the introduction of ‘lalangue’ has several theoretical and clinical implications that will radically change Lacans teachings. We will illustrate the distinction between language and lalangue. Language serves communication, but this is not the case with lalangue. We will claim that there is jouissance in language and will approach this by introducing the concept of ‘lalangue’. We will ask ourselves what the effect will be of this distinction and how we can use this in clinical practice. The concept of ‘lalangue’ will introduce a new way of thinking about the unconscious. It will force us to no longer view the unconscious as Symbolic, but as Imaginary or Real. Another implication will be the approach on the symptom, no longer approaching it as a formation of the unconscious. It will be renamed as ‘sinthome’, as function of the real. Last of all it will force us to rethink the lacanian interpretation and how we direct the treatment. The implications on a clinical level will be how we think about the lacanian interpretation and the direction of the treatment. We will no longer focus on language and meaning, but focus on jouissance and the ways in which the subject deals with this. We will illustrate this importance with a clinical case study. To summarize, the concept of lalangue forces us to radically rethink lacanian psychoanalysis, with major implications on a theoretical and clinical level. It introduces new concepts such as the real unconscious and the sinthome. It will also make us rethink the way we work as lacanian psychoanalysts.

Keywords: Lacan's later teaching, language, Lalangue, the unconscious

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Authors: Khalil Aryanfar, Shahrzad Sanjari, Pariya Gholipor, Elmira Hafez

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The present study aimed to investigate and compare the characteristics of entrepreneurship among students in senior secondary schools in the academic year 2008-2009 in Tabriz city. Research employed survey method respectively. The study population consisted of all students in the senior branch of theoretical, technical, professional and vocational (1033 patients) were included. Sample size of 493 was calculated according to Morgan table. Sampling method was random cluster and stratified sampling. Data collected by researcher made questionnaire based on the theory of MC clleland (1963) and Brvkhavs (1980). These tools would indicators be for achievement, Independence, disposition, creativity, risk-taking, self-control, tolerance for ambiguity, team work approach in the future. To determine the psychometric properties of the questionnaire, content validity of the survey was approved by relevant experts. In addition, to estimate the internal consistency of Cronbach's alpha coefficient was calculated for 84% of total inventory. Collected data Using mean, standard deviation and were analyzed by ANOVA. The results showed that there is a significant difference between students' entrepreneurial potential fields of theoretical, technical, professional and vocational level (0/01).

Keywords: entrepreneurship, achievement motivation, risk taking, creativity, self-control, independence, tolerance of ambiguity, foresight

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Authors: Edward J. Kansa, Pavel Holoborodko

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Continuously differentiable radial basis functions (RBFs) are meshfree, converge faster as the dimensionality increases, and is theoretically spectrally convergent. When implemented on current single and double precision computers, such RBFs can suffer from ill-conditioning because the systems of equations needed to be solved to find the expansion coefficients are full. However, the Advanpix extended precision software package allows computer mathematics to resemble asymptotically ideal Platonic mathematics. Additionally, full systems with extended precision execute faster graphical processors units and field-programmable gate arrays because no branching is needed. Sparse equation systems are fast for iterative solvers in a very limited number of cases.

Keywords: partial differential equations, Meshfree radial basis functions, , no restrictions on spatial dimensions, Extended arithmetic precision.

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Authors: K. M. Etmimi, A. A. Sghayer, A. M. Gsiea, A. M. Abutruma

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Relatively few chemical species can be incorporated into diamond during CVD growth, and until recently the uptake of oxygen was thought to be low perhaps as a consequence of a short surface residence time. Within the literature, there is speculation regarding spectroscopic evidence for O in diamond, but no direct evidence. For example, the N3 and OK1 EPR centres have been tentatively assigned models made up from complexes of substitutional N and substitutional oxygen. In this study, we report density-functional calculations regarding the stability, electronic structures, geometry and hyperfine interaction of substitutional oxygen in diamond and show that the C2v, S=1 configuration very slightly lower in energy than the other configurations (C3v, Td, and C2v with S=0). The electronic structure of O in diamond generally gives rise to two defect-related energy states in the band gap one a non-degenerate a1 state lying near the middle of the energy gap and the other a threefold-degenerate t2 state located close to the conduction band edges. The anti-bonding a1 and t2 states will be occupied by one to three electrons for O+, O and O− respectively.

Keywords: DFT, oxygen, diamond, hyperfine

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Authors: M. Rodionov, Z. Dedovets

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The article describes the theoretical concept of teaching secondary school students proof demonstration skills in mathematics. It describes in detail different levels of mastery of the concept of proof-which correspond to Piaget’s idea of there being three distinct and progressively more complex stages in the development of human reflection. Lessons for each level contain a specific combination of the visual-figurative components and deductive reasoning. It is vital at the transition point between levels to carefully and rigorously recalibrate teaching to reflect the development of more complex reflective understanding. This can apply even within the same age range, since students will develop at different speeds and to different potential. The authors argue that this requires an aware and adaptive approach to lessons to reflect this complexity and variation. The authors also contend that effective teaching which enables students to properly understand the implementation of proof arguments must develop specific competences. These are: understanding of the importance of completeness and generality in making a valid argument; being task focused; having an internalised locus of control and being flexible in approach and evaluation. These criteria must be correlated with the systematic application of corresponding methodologies which are best likely to achieve success. The particular pedagogical decisions which are made to deliver this objective are illustrated by concrete examples from the existing secondary school mathematics courses. The proposed theoretical concept formed the basis of the development of methodological materials which have been tested in 47 secondary schools.

Keywords: education, teaching of mathematics, proof, deductive reasoning, secondary school

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Authors: Y. Galerkin, A. Rekstin, K. Soldatova

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Universal modeling method well proven for industrial compressors was applied for design of the high flow rate supersonic stage. Results were checked by ANSYS CFX and NUMECA Fine Turbo calculations. The impeller appeared to be very effective at transonic flow velocities. Stator elements efficiency is acceptable at design Mach numbers too. Their loss coefficient versus inlet flow angle performances correlates well with Universal modeling prediction. The impeller demonstrated ability of satisfactory operation at design flow rate. Supersonic flow behavior in the impeller inducer at the shroud blade to blade surface Φdes deserves additional study.

Keywords: centrifugal compressor stage, supersonic impeller, inlet flow angle, loss coefficient, return channel, shock wave, vane diffuser

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Authors: Karel Frana, Sylvio Simon

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The objective of the paper is a numerical study of heat transfer between perforated metal plates and the surrounding air flows. Different perforation structures can nowadays be found in various industrial products. Besides improving the mechanical properties, the perforations can intensify the heat transfer as well. The heat transfer coefficient depends on a wide range of parameters such as type of perforation, size, shape, flow properties of the surrounding air etc. The paper was focused on three different perforation structures which have been investigated from the point of the view of the production in the previous studies. To determine the heat coefficients and the Nusselt numbers, the numerical simulation approach was adopted. The calculations were performed using the OpenFOAM software. The three-dimensional, unstable, turbulent and incompressible air flow around the perforated surface metal plate was considered.

Keywords: perforations, convective heat transfers, turbulent flows, numerical simulations

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Authors: Surjit Angra, Pooja Rani, Vinod Kumar

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In hydro power plant spiral casing and Stay ring is meant to guide the water flow to guide vane and runner. Spiral casing and Stay ring is subjected to static i.e. pressure load as well as fluctuating load acting on the structure due to water hammer effect in water conductor system. Finite element method has been used to calculate stresses on spiral casing and stay ring. These calculations were done for the maximum possible loading under operating condition "LC1 Quick Shut Down”. The design load is reached for the spiral casing and stay ring during the emergency closure of the guide apparatus "LC1 Quick Shut Down”. During this operation the forces from the head cover to the stay ring also reach their maximum.

Keywords: hydro-turbine, spiral casing, stay ring, structural analysis

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Authors: Alireza Ghadiri, Soheila Memarzadeh, Arash Ghadiri

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Heat pipes are efficient heat transfer devices for solar hot water heating systems. However, the effective downward transfer of solar energy in an integrated heat pipe system provides increased design and implementation options. There is a lack of literature about flat plate wicked assisted heat pipe solar collector, especially with the presence of finned water-cooled condenser wicked heat pipes for solar energy applications. In this paper, the consequence of incorporating fins arrays into the condenser region of screen mesh heat pipe solar collector is investigated. An experimental model and a transient theoretical model are conducted to compare the performances of the solar heating system at a different period of the year. A good agreement is shown between the model and the experiment. Two working fluids are investigated (water and methanol) and results reveal that water slightly outperforms methanol with a collector instantaneous efficiency of nearly 60%. That modest improvement is achieved by adding fins to the condenser region of the heat pipes. Results show that the collector efficiency increase as the number of fins increases (upon certain number) and reveal that the mesh number is an important factor which affect the overall collector efficiency. An optimal heat pipe mesh number of 100 meshes/in. With two layers appears to be favorable in such collectors for their design and operating conditions.

Keywords: heat pipe, solar collector, capillary limit, mesh number

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Authors: L. Raczynski, P. Moskal, P. Kowalski, W. Wislicki, T. Bednarski, P. Bialas, E. Czerwinski, A. Gajos, L. Kaplon, A. Kochanowski, G. Korcyl, J. Kowal, T. Kozik, W. Krzemien, E. Kubicz, Sz. Niedzwiecki, M. Palka, Z. Rudy, O. Rundel, P. Salabura, N.G. Sharma, M. Silarski, A. Slomski, J. Smyrski, A. Strzelecki, A. Wieczorek, M. Zielinski, N. Zon

Abstract:

The J-PET scanner, which allows for single bed imaging of the whole human body, is currently under development at the Jagiellonian University. The J-PET detector improves the TOF resolution due to the use of fast plastic scintillators. Since registration of the waveform of signals with duration times of few nanoseconds is not feasible, a novel front-end electronics allowing for sampling in a voltage domain at four thresholds was developed. To take fully advantage of these fast signals a novel scheme of recovery of the waveform of the signal, based on ideas from the Tikhonov regularization (TR) and Compressive Sensing methods, is presented. The prior distribution of sparse representation is evaluated based on the linear transformation of the training set of waveform of the signals by using the Principal Component Analysis (PCA) decomposition. Beside the advantage of including the additional information from training signals, a further benefit of the TR approach is that the problem of signal recovery has an optimal solution which can be determined explicitly. Moreover, from the Bayes theory the properties of regularized solution, especially its covariance matrix, may be easily derived. This step is crucial to introduce and prove the formula for calculations of the signal recovery error. It has been proven that an average recovery error is approximately inversely proportional to the number of samples at voltage levels. The method is tested using signals registered by means of the single detection module of the J-PET detector built out from the 30 cm long BC-420 plastic scintillator strip. It is demonstrated that the experimental and theoretical functions describing the recovery errors in the J-PET scenario are largely consistent. The specificity and limitations of the signal recovery method in this application are discussed. It is shown that the PCA basis offers high level of information compression and an accurate recovery with just eight samples, from four voltage levels, for each signal waveform. Moreover, it is demonstrated that using the recovered waveform of the signals, instead of samples at four voltage levels alone, improves the spatial resolution of the hit position reconstruction. The experiment shows that spatial resolution evaluated based on information from four voltage levels, without a recovery of the waveform of the signal, is equal to 1.05 cm. After the application of an information from four voltage levels to the recovery of the signal waveform, the spatial resolution is improved to 0.94 cm. Moreover, the obtained result is only slightly worse than the one evaluated using the original raw-signal. The spatial resolution calculated under these conditions is equal to 0.93 cm. It is very important information since, limiting the number of threshold levels in the electronic devices to four, leads to significant reduction of the overall cost of the scanner. The developed recovery scheme is general and may be incorporated in any other investigation where a prior knowledge about the signals of interest may be utilized.

Keywords: plastic scintillators, positron emission tomography, statistical analysis, tikhonov regularization

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Authors: Peter C. St. John, Michael F. Crowley, Yannick J. Bomble

Abstract:

Production of chemicals from engineered organisms in a batch culture typically involves a trade-off between productivity, yield, and titer. However, strategies for strain design typically involve designing mutations to achieve the highest yield possible while maintaining growth viability. Such approaches tend to follow the principle of designing static networks with minimum metabolic functionality to achieve desired yields. While these methods are computationally tractable, optimum productivity is likely achieved by a dynamic strategy, in which intracellular fluxes change their distribution over time. One can use multi-stage fermentations to increase either productivity or yield. Such strategies would range from simple manipulations (aerobic growth phase, anaerobic production phase), to more complex genetic toggle switches. Additionally, some computational methods can also be developed to aid in optimizing two-stage fermentation systems. One can assume an initial control strategy (i.e., a single reaction target) in maximizing productivity - but it is unclear how close this productivity would come to a global optimum. The calculation of maximum theoretical yield in metabolic engineering can help guide strain and pathway selection for static strain design efforts. Here, we present a method for the calculation of a maximum theoretical productivity of a batch culture system. This method follows the traditional assumptions of dynamic flux balance analysis: that internal metabolite fluxes are governed by a pseudo-steady state and external metabolite fluxes are represented by dynamic system including Michealis-Menten or hill-type regulation. The productivity optimization is achieved via dynamic programming, and accounts explicitly for an arbitrary number of fermentation stages and flux variable changes. We have applied our method to succinate production in two common microbial hosts: E. coli and A. succinogenes. The method can be further extended to calculate the complete productivity versus yield Pareto surface. Our results demonstrate that nearly optimal yields and productivities can indeed be achieved with only two discrete flux stages.

Keywords: A. succinogenes, E. coli, metabolic engineering, metabolite fluxes, multi-stage fermentations, succinate

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Authors: Huang Yajing

Abstract:

Context: Computer-aided language learning (CALL) in China has undergone significant development over the past few decades, with distinct stages marking its evolution. This paper aims to provide a comprehensive review of the practice and research in this field in China, tracing its journey from the early stages of audio-visual education to the current multimedia network integration stage. Research Aim: The study aims to analyze the historical progression of CALL in China, identify key developments in the field, and provide recommendations for enhancing CALL practices in the future. Methodology: The research employs document analysis and literature review to synthesize existing knowledge on CALL in China, drawing on a range of sources to construct a detailed overview of the evolution of CALL practices and research in the country. Findings: The review highlights the significant advancements in CALL in China, showcasing the transition from traditional audio-visual educational approaches to the current integrated multimedia network stage. The study identifies key milestones, technological advancements, and theoretical influences that have shaped CALL practices in China. Theoretical Importance: The evolution of CALL in China reflects not only technological progress but also shifts in educational paradigms and theories. The study underscores the significance of cognitive psychology as a theoretical underpinning for CALL practices, emphasizing the learner's active role in the learning process. Data Collection and Analysis Procedures: Data collection involved extensive review and analysis of documents and literature related to CALL in China. The analysis was carried out systematically to identify trends, developments, and challenges in the field. Questions Addressed: The study addresses the historical development of CALL in China, the impact of technological advancements on teaching practices, the role of cognitive psychology in shaping CALL methodologies, and the future outlook for CALL in the country. Conclusion: The review provides a comprehensive overview of the evolution of CALL in China, highlighting key stages of development and emerging trends. The study concludes by offering recommendations to further enhance CALL practices in the Chinese context.

Keywords: English education, educational technology, computer-aided language teaching, applied linguistics

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Authors: Liaquat Ahmad, Muhammad Aslam, Muhammad Azam

Abstract:

In this article, we propose a control chart based on repetitive group sampling scheme for the location parameter. This charting scheme is based on the regression estimator; an estimator that capitalize the relationship between the variables of interest to provide more sensitive control than the commonly used individual variables. The control limit coefficients have been estimated for different sample sizes for less and highly correlated variables. The monitoring of the production process is constructed by adopting the procedure of the Shewhart’s x-bar control chart. Its performance is verified by the average run length calculations when the shift occurs in the average value of the estimator. It has been observed that the less correlated variables have rapid false alarm rate.

Keywords: average run length, control charts, process shift, regression estimators, repetitive group sampling

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Authors: Murat Toren, Mehmet Çelebi

Abstract:

Reducing the weight of transformers while providing good performance, cost reduction and increased efficiency is important. Weight is one of the most significant factors in all electrical machines, and as such, many transformer design parameters are related to weight calculations. This study presents a comparison of the weight of oil type transformers and dry type transformer weight. Oil type transformers are mainly used in industry; however, dry type transformers are becoming more widespread in recent years. MATLAB is typically used for designing transformers and design parameters (rated voltages, core loss, etc.) along with design in ANSYS Maxwell. Similar to other studies, this study presented that the dry type transformer option is limited. Moreover, the commonly-used 50 kVA distribution transformers in the industry are oil type and dry type transformers are designed and considered in terms of weight. Currently, the preference for low-cost oil-type transformers would change if costs for dry-type transformer were more competitive. The aim of this study was to compare the weight of transformers, which is a substantial cost factor, and to provide an evaluation about increasing the use of dry type transformers.

Keywords: weight, optimization, oil-type transformers, dry-type transformers

Procedia PDF Downloads 345