A large amount of energy is required in the production of steel where the preheating of blast in the hot blast stoves for iron-making is one of the most energy-intensive processes. To improve the ...energy efficiency it is necessary to investigate how to improve the hot blast stove operation.
In this work a mathematic model for evaluating the performance of the hot blast stove was developed using a finite difference approximation to represent the heat transfer inside the stove during operation. The developed model was calibrated by using the process data from the stove V26 at SSAB Oxelösund, Sweden. As a case study, the developed model was used to simulate the effect of a new concept of OxyFuel technique to hot blast stoves. The investigation shows that,by using the OxyFuel technique, it is possible to maintain the blast temperature while removing the usage of coke oven gas. Additionally, the hot blast temperature increases while the flue gas temperature decreases, which allows for an increase of the blast temperature, leading to improved energy efficiency for the hot stove system.
This article succeeds the former A. P. K nko’ and A. I. Kuzmina’ ubl t on titled "A mathematical model of urban distribution electro-network considering its future development" (electronic scientific ...and technical magazine "Science and education" No. 5, 2014).The article offers a model of urban power distribution network as a set of transformer and distribution substations and cable lines. All elements of the network and new consumers are determined owing to vectors of parameters consistent with them.A problem of the urban power distribution network design, taking into account a prospective development of the city, is presented as a problem of discrete programming. It is in deciding on the optimal option to connect new consumers to the power supply network, on the number and sites to build new substations, and on the option to include them in the power supply network.Two methods, namely a reduction method for a set the nested tasks of global minimization and a decomposition method are offered to solve the problem.In reduction method the problem of prospective development of power supply network breaks into three subtasks of smaller dimension: a subtask to define the number and sites of new transformer and distribution substations, a subtask to define the option to connect new consumers to the power supply network, and a subtask to include new substations in the power supply network. The vector of the varied parameters is broken into three subvectors consistent with the subtasks. Each subtask is solved using an area of admissible vector values of the varied parameters at the fixed components of the subvectors obtained when solving the higher subtasks.In decomposition method the task is presented as a set of three, similar to reduction method, reductions of subtasks and a problem of coordination. The problem of coordination specifies a sequence of the subtasks solution, defines the moment of calculation termination. Coordination is realized by introducing the vectors of parameters of limiting and stimulating coordination into the problem. Vector components of limiting coordination mean the minimum numbers of substations to be built. Vector components of stimulating coordination define "usefulness" of new substations to be built on possible sites. There are two offered options to determine parameters of stimulating coordination.The offered methods of reduction and decomposition generally generate a large number of the optimization algorithms. Subsequent publications are expected to consider these algorithms and a software to implement them.
Low ability of students solving the problems can be overcome by accustomed to work on Higher Order Thinking Skills (HOTS) which include analyzing (C4), evaluating (C5) and creating (C6). This study ...aims to find the distribution of Mathematics questions based on HOTS in integrated thematic textbooks in the 2013 curriculum. Its importance is to give an overview to the government, especially teachers about the quality of these books which are used by schools until 2021. This research is a content analysis with a qualitative approach. Data sources in this study are integrated thematic textbooks of Curriculum 2013 revised edition 2018 for grades I to III SD / MI. The data analysis technique uses percentage analysis. The results showed that the cognitive level of HOTS class I in C4 at 22%, C5 at 4%, C6 at 11%. Class II, C4 at 28%, C5 at 1%, C6 at 6%. Meanwhile, class III, C4 at 29%, C5 at 3%, C6 at 6%. In conclusion, HOTS mathematics questions on cognitive level C4, C5, and C6 in the thematic books of the 2013 curriculum for classes I, II, and III have not reached the criteria for good questions because the percentage of good questions for each cognitive level is C4 40%, C5 30% , and C6 by 30%.
The technology that has evolved can not be denied in fact has entered in every line of life. Not many of us are not familiar with a technology let alone which has been the topic of conversation ...since the last few years, call it with information tools such as smartphones. These tools can help in classroom learning activities. The problems that arise in learning how students need to use some new learning techniques and can visualize and can be taken anywhere. Students have difficulties in learning the mathematics of geometry a flat side room and this media is needed. The model used is Lee & Owens. The result of the research is a valid mobile learning media. Abstrak: Teknologi yang telah berkembang tidak bisa dipungkiri pada kenyataannya telah masuk dalam setiap lini kehidupan. Tidak banyak dari kita yang tidak mengenal suatu teknologi apalagi telah menjadi topik perbincangan sejak beberapa tahun terakhir, sebut saja dengan alat informasi, seperti smartphone. Alat tersebut dapat membantu dalam kegiatan pembelajaran di kelas. Permasalahan yang muncul pada pembelajaran bagaimana siswa perlu menggunakan beberapa teknik belajar yang baru dan dapat memvisualkan serta dapat dibawa kemanapun. Siswa kesulitan mempelajari matematika bahasan bangun ruang sisi datar dan dibutuhkan media ini. Model yang digunakan yaitu Lee & Owens. Hasil penelitian berupa media mobile learning yang valid.
Sintering is essential for inkjet printing and laser sintering is a promising sintering technology. In this study, the effect of laser sintering processing parameters on the sintering quality of ...silver content metal‐organic‐decomposition (MOD) inks is studied. A novel mathematic model is developed to reveal the temperature evolutions in MOD inks and the substrates during laser sintering. In the novel model, the change of thermal conductivity of MOD inks is taken into consideration for the first time to improve simulation accuracy. The simulation results agree well with the experiments, showing the advantages of the mathematic model. The surface morphology of the sintered MOD inks are also observed through experiments. The simulation and experimental results show that the laser sintering processing parameters have significant effects on the sintering quality. With authors’ optimised laser sintering processing parameters, the printed pattern can be sufficiently sintered and its electronic conductivity can reach 1.56 × 10–7 S/m. Thus, a sintering optimisation strategy is proposed based on the results. Finally, a microstrip antenna is fabricated with the optimised sintering strategy. The performance of the antenna agree well with the simulation results, indicating authors’ optimising strategy is useful for industrial production.
This study introduces the results of scientific research and pilot testing of modernised automated electric drives of the plate mill stands. The experimental tests of electromechanical systems of the ...reversing stand of the mill 5000 showed the intolerable level of dynamic loads when biting. The problem of reducing dynamic loads and elastic vibrations in shaft lines was stated; it can be solved through enhancing the automated electric drive. The method for limiting loads through biting metal with accelerated rolls and compensating the dynamic component of speed was suggested. The functional diagram of the electric drive to implement the suggested method was designed. In order to study the suggested technical solution, the dynamic mathematic model of the mill stand electric drive with elastic coupling was developed. The results of modelling dynamic modes and experimental studies carried out on the mill 5000 were introduced. The operability and efficiency of the suggested solutions were substantiated.
Damage analysis in automotive gearbox Barbieri, Nilson; de Sant’Anna Vitor Barbieri, Gabriel; Martins, Bruno Matos ...
Procedia engineering,
2017, 2017-00-00, Volume:
199
Journal Article
Peer reviewed
Open access
In more complex systems, such as automotive gearbox, a rigorous treatment of the data is necessary because there are several moving parts (gears, bearings, shafts, etc.), and in this way, there are ...several possible sources of errors and noise. The basic objective of this work is the detection of damage in automotive gearbox using a computational tool for inspection and maintenance of automotive gearboxes. The methodology of inspection and fault identification in gearboxes, involve the acquisition of vibration data on a bench tests and data processing using bispectrum theory, wavelet transform and morphological mathematic. Gearbox vibration tests were performed (gearboxes in good condition and with defects) of a production line of a large vehicle assembler. The vibration signals are obtained using five accelerometers in different positions of the sample. The results obtained using bispectrum, wavelet and mathematical morphology showed that it is possible to identify the existence of defects in automotive gearboxes. The combination of pattern spectrum and selective filtering in certain frequencies ranges are used for identification of component with failures. Currently the gearboxes are supervised by a subjective method (human hearing). Thus, a computational tool is more reliable and provide more capabilities for the inspection and diagnosis system.
Highlights • This model would be particularly important in developing countries. • Projection distance was applied to reduce X-ray projection related errors. • A simulation model based on X-ray is ...good for surgery of unstable pelvic fractures.
In new teaching-learning approaches, it is emphasized in meaningful learning versus rote learning .So assessment and evaluation as an inseparable part of the educational process should also be ...altered to suit the new educational approaches. One of the new tools for assessment and evaluation of conceptual knowledge is conceptual scheme. Conceptual scheme contains concepts or phrases that are set in a circle or other geometric shapes and lines connecting with the significant relationship together. Conceptual scheme is a useful tool for education, curriculum development, assessment and evaluation of learning. In this study, using the conceptual scheme, understanding of 25 third-year students who major in mathematics teacher in the Shahid Rajaee Teacher Training University was evaluated about limit concept. After familiarizing students with the conceptual scheme in three stages, students come with software to draw a conceptual scheme of “limit” individually and in groups. The findings show that misunderstanding and errors was reduced at each stage compared to a previous stage. Width and length relations get closer, more, and more complex respectively. Some misunderstanding of students that were identified in this way includes: (2) Definition of limit to a point where some students thought that the point should be in the function domain. (2)Some of them knew “limit’ ’for sequence divergence. (3)All asymptotic have not stated using the limit. Identify the misunderstanding of students using the traditional tools of evaluation was not possible. Moreover, according to the standard connections in learning, the relationship represents a deeper conceptual understanding of the concept when relations increase. The results can provide a basis for revision of assessment methods and improving the quality of educational designin.
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