Differences in Norwegian and Swedish student teachers’ explanations of solutions of linear equations

This study draws on data from 146 Norwegian and 161 Swedish student teachers. They were given a correct but short and unannotated solution to the linear equation x + 5 = 4x – 1. The student teachers were invited to explain the solution provided for a fictive friend, who was absent when the teacher introduced this topic. An accurate solution of this equation contains two additive and one multiplicative operation. There are two main strategies for solving a linear equation, ‘swap sides swap signs’ (SSSS) and ‘do the same to both sides’ (DSBS). Of the Norwegian student teachers, 2/3 explained the additive steps in the solution by SSSS, while only 1/3 of the Swedish student teachers applied SSSS. Consequently, DSBS was more frequent among the Swedish student teachers regarding the additive steps. However, in the final, multiplicative step, 3/4 of the Norwegian student teachers chose to explain by DSBS. On the contrary, among the Swedish student teachers the proportion applying DSBS for the multiplicative step of the solution decreased, and almost as many provided a deficient explanation of the final operation. We discuss possible reasons for differences between the nations. We also suggest how teacher educators in both countries can use the results of this study to improve student teachers’ explanations of how to solve linear equations.

Methods of synchronization of electric drives not mechanically connected

The article provides a comparative analysis of the structures of synchronization of the motion of electric drives of medium and high power. A comparison of synchronization structures is made in terms of the impact on the final operation of the system and hardware synchronization methods in terms of applicability and maximum performance. The mathematical apparatus is based on the principle of separation of the movements of each of the electric drives and the representation of its transfer function in matrix form. The control ranges and speed of different types of systems are compared experimentally by evaluating the speed of data transmission and evaluating the speed ripple at low revs.

Viscoelastic web curl due to storage in wound rolls

Winding is often the final operation in a roll-to-roll manufacturing process. Web materials, i.e., materials that are thin compared to their length, are wound into rolls because this form is the only practical means to store them. The resulting bending strains and associated stresses are large for thick webs and laminates. As many webs are viscoelastic on some time scale, bending stresses lead to creep and inhomogeneous changes in length. When the web material is unwound and cut into discrete samples, a residual curvature remains. This curvature, called curl, is the inability for the web to lie flat at no tension. Curl is an undesirable web defect that causes loss of productivity in a subsequent web process. This paper describes the development and implementation of modeling and experimental tools to explore and mitigate curl in homogenous webs. Two theoretical and numerical methods that allow the prediction of curl in a web are developed: a winding software based on bending recovery theory, and the implementation of dynamic simulations of winding. One experimental method is developed that directly measures the curl online by taking advantage of the anticlastic bending resulting from the curl. These methods are demonstrated for a low-density polyethylene web.

DEVELOPMENT OF MAHÂRAH AL-ISTIMÂ’ TEST INSTRUMENT FOR ELECTRONIC BASED ARABIC STUDENT USING THE KAHOOT! APPLICATION

This study aimed to develop the feasibility of the Mahârah al-Istimâ’ test instrument for electronic-based Arabic students using the Kahoot! application at UIN Sunan Kalijaga Yogyakarta. The method used in this research is the research and development of Borg and Gall model through analysis, design, and testing. Eligibility is based on the expert validator test and the final operation field test. The results of the study can be concluded that: 1) Preparation of the Test Instrument refers to the 5 objectives or indicators of Mahmud Kamil an-Naqah into 50 questions in product design using the Kahoot! application, 2) From the results of the expert validator it is known that the results of the material quality are obtained by an average 5.37 and the media quality of the application is obtained by an average of 4.75 (very feasible), 3) After being obtained from the main field test to 20 students there are 6 questions or 12% that are not feasible because they are invalid and have not discrimination index, then the author revise and test the revision results to 70 students with 100% valid results and are suitable for use.

WT1 gene mutation in exone 7 in boy with disturbance of the sex formation and the bilateral nephroblastoma

The case of observing a patient with WT1 gene mutation in exone 7 with bilateral Wilms metachronous tumor, disturbance of the sex formation in the form of scrotal hypospadias and bilateral abdominal cryptorchidism, without nephropathy, is presented. The child underwent surgical operations: left-sided nephrectomy, resection of the lower pole of the right kidney, bilateral orchiopexy and two-stage hypospadias correction. 7 years after the start of treatment and 3 years after the final operation, the condition of the child was estimated as satisfactory. The presented case by the results of the molecular genetic study has no previously described analogues and requires further observation.

New design universal working bodies of tillage and seeding equipment

New designs of tillage and seeding equipment are presented. Technological and technical deficiencies of the existing working bodies for surface tillage and sowing techniques of row crops are noted. To eliminate the shortcomings, new universal working bodies of tillage and sowing units have been proposed, which provide for the mechanization and automation of working processes of tillage and seeding of various row crops. Their technological and technical advantages over the existing traditional working bodies are given. The technical characteristics of the new working bodies are presented, which allow to simultaneously perform four operations: cultivation, fissure, seeding and leveling the field surface. Execution of the sieve in the form of two discs with rollers on its inner surface allows cutting a slit along the sides from the vertical axis of seed placement, at a depth of almost twice the sowing depth to improve the water-air regime, with simultaneous compaction of the soil by the rollers. The final operation to level the soil across the entire width of the cultivator's paw grip is carried out by embedding a train. Also presented is the design of a modernized pneumatic sowing unit for various sowing methods, ensuring the simultaneous sowing of seeds of several types of row crops with their placement at different planting depth in accordance with agrotechnical requirements

Computing Stress-Strain State of a Workpiece During Drawing with Wall Thinning Through a Die with a Small Taper Angle

The paper considers computing the stress-strain state of a workpiece during drawing with wall thinning through a die with a small taper angle. A manufacturing process for a sleeve usually includes several drawing operations, whereas recommendations for the final drawing operation are a low extent of deformation and using dies with a small taper angle of (2°--4°). We present a diagram for drawing with wall thinning, delineating all deformation stages recorded on the chart showing force as a function of tool path. We computed the stress-strain state and deformation in the workpiece wall during the final operation of drawing through a die with a small taper angle α ≤ 4°. We provide equilibrium equations in toroidal coordinates and compute stress-strain state parameters and extents of deformation for the axisymmetric problem statement. No longer assuming a plane strain state, we compute the stress-strain state and extent of deformation in the workpiece wall during drawing with wall thinning through a die with a small taper angle α = 2°--4°. We show that at the stage when intermediate product walls are formed, for a small taper angle it is reasonable to consider the process of drawing with wall thinning to be monotone.

Modern methodology for the development of parametric models for determining the cost of transporting freights for tariff setting purposes

One of the key problems of organizing an effective The article considers problems of the influence of technical transportation process is an adequate reflection of the current and technological parameters of freight transportation by rail on pricing factors in the tariff system. This can be done on the basis of the cost price for tariff purposes, the distribution of the cost of the the development of appropriate models for determining the cost initial-final operation between loaded and empty cars, determinaof transportation. Modeling the cost of transporting freights by rail tion of coefficients taking into account the length of cars and the for tariff purposes is based on determining and assessing the rela-distance of transportation, as well as the methodology for the distionship between transportation costs and work indexes. tribution of costs between the initial-final and motion operations. Proposed updated methodology for constructing parametric models for determining the cost of transportation of freights for tariff setting purposes includes: method of itemized distribution of expenditures between non-commercial organizations and affiliated subsidiaries in terms of infrastructure and traction; procedure for allocating the costs, attributed to affiliated subsidiaries, to the indexes “ton-kilometer gross” and “car-kilometer”; system of itemized distribution of freight costs for the indexes of the transportation operation, as well as the system for calculating the aggregate expenditure rates (AER) used in parametric models of the cost price; actualized assessment of the influence of the length of the car on the cost value for tariff setting purposes; procedure for allocating the cost of initial-final operations between loaded and empty cars. The developed parametric models for calculating the cost of transportation for tariff purposes for transportation by the locomotive of the JSC “Russian Railways” take into account such factors as the distance of transportation, the weight of the container and the length of the car, its loading, the type of shipment. Within the framework of creating new parametric models, the following factors have been updated: coefficients that take into account the length of the car; coefficients that take into account the effect on the cost of production up to the distance of transportation in connection with the change in the relative distance of carriage of the car as part of mixed and transfer-and-export trains; coefficients depending on the type of shipment.

The structural design and technical investigations of data resources sharing system in the field of aero engine

Purpose Nowadays, a large amount of data related to aero engine in various types can be created in a single day and it is very important to well organize and store these data. The paper aims to discuss this issue. Design/methodology/approach This paper puts forward the problem of data management with the fast development of aero engine and sets the compression system as an example to see the inner relationships of data from the initial design procedure to the final operation and maintenance part. There are five principles, namely digitization, accuracy, normative, integrality and validity, involved in managing the data effectively. Findings These data resources arranged according to the five principles can be well organized and better used. Originality/value At the end, the top design of aero engine data sharing platform is investigated and five layers including data layer, data access layer, communication layer, business logic layer and application layer are designed and presented to support the platform.