METHOD OF FINDING LOSSES IN THE THROTTLE WINDING AS A RESULT OF THE SKIN EFFECT AND THE PROXIMITY EFFECT

Представлен метод использования расчетных методик и моделирования магнитных полей в двухмерном пространстве для нахождения высокочастотных потерь в обмотке моточных изделий, таких как дроссель или трансформатор. Была проведена работа по анализу литературы по данной теме, а также поднят вопрос оптимизации и адаптации аналитических формул для случая использования проводников круглого сечения и намотки, имеющей неоднородное распределение слоев в окне сердечника. Был также поднят вопрос об аналитическом нахождении длины обмоточного провода намотки с различным количеством слоев и переменного количества используемых при этом витков. Для проведения автоматизации расчета с помощью формул был написан скрипт, строящий зависимость сопротивления переменному току относительно частоты, используя аналитические формулы. Была написана программа для автоматической постановки начальных условий и граничных значений параметров моделирования, процесса самого моделирования электромагнитных полей, анализа полученных данных, а также формирования массива для построения графика полученной при этом зависимости сопротивления от частоты. В данном методе используется свободно распространяемое программное обеспечение как для математических расчетов, так и моделирования электромагнитных полей. Итогом данной работы стало сравнение полученных результатов, которые показали хорошую сходимость и преемственность этапов данного метода Here we present a method for using computational methods and modeling magnetic fields in two-dimensional space to find high-frequency losses in the winding of winding products, such as a choke or transformer. We analyzed the literature on this topic, as well as the issue of optimization and adaptation of analytical formulas for the case of using round-section conductors and winding having a non-uniform distribution of layers in the core window. We discussed the analytical finding of the length of the winding wire of the winding with a different number of layers and a variable number of turns used in this case. To automate the calculation using formulas, we wrote a script that builds the dependence of the resistance to alternating current relative to the frequency using analytical formulas. In addition, we wrote a program for automatically setting the initial conditions and boundary values of the modeling parameters, the process of modeling electromagnetic fields itself, analyzing the data obtained, as well as forming an array for plotting the resulting dependence of resistance on frequency. This method uses freely distributed software for both mathematical calculations and modeling of electromagnetic fields. The result of this work was a comparison of the results obtained, which showed good convergence and continuity of the stages of this method

CALCULATION OF INTERMEDIATE SUPPORTING PARTS OF INSEPARABLE PERFORATED BEAMS IN THE SOFTWARE COMPLEX «LIRA»

Due to the simplicity of design and manufacture, as well as reliability during operation, beams are one of the most common elements used in industrial, civil and public construction. The most rational cross-section of metal beams are rolled I-beams with inclined or parallel inner faces of the shelves, the predominant use of which is due to the value of the core distance, which is twice as much the same value for a rectangular section and almost three times for a round section. This figure is even higher for perforated profiles obtained from conventional rolling beams, which allow you to compose sections with increased values of moments of inertia and moments of resistance without increasing material consumptions. For inseparable beams, an additional significant factor influencing on their bearing capacity, is the structural design of the intermediate support part. The aim of these researches is to study the stress-strain state of inseparable perforated beams of I-beam profile of different heights in areas near the intermediate support, the design of which is made without a transverse stiffening rib placed on the axis of the support, and with unwelded holes to the left and right of the support under the action of evenly distributed load in the software complex "Lira". The objectives of the study are to establish the actual values of stresses and strains in the characteristic cross sections of the inseparable perforated I-beam, which occur on the intermediate support, and perform a comparative analysis of numerical studies obtained in the software complex "Lira" for intermediate support node beams of different heights for actions of different magnitudes of loads. The analysis of the obtained diagrams of normal stresses was carried out, which showed that for the proposed design of the support part of the beam, the cross-sections with holes directly to the left and right of the support are calculated. The conclusion about necessity of carrying out further experimental-theoretical researches of various types of support parts of beams for the purpose of development of a complex technique of their calculation and recommendations on definition of rational scope of application of each of them is formulated.

Investigation of corrosion rate of X55CrMo14 stainless steel at 65% nitrate acid at 348 K

A number of factors determine the mechanical, but also physical and chemical properties. One of the most important are the steel microstructure and its working conditions. A few corrosion processes in crevices and awkward corners can be avoided at the design stage (low roughness parameters, round-section and other). But still the construction material is exposed to corrosion. These steels often come into contact with an aggressive environment based on nitric acid. Stainless steel is more and more often used in many sectors of industry. The purpose of this article is to investigate corrosion resistance in different time (48, 96, 144, 192, 240, 288, 336, 384 and 432 hours) using weight loss and profile roughness parameters of martensitic steel in grade X55CrMo14 in nitric acid 65% pure-basic at temperature 348 K. Corrosion tests show that the tested steel in nitric acid as a corrosive environments is characterized through continuous corrosion process whose measure may be surface roughness.

Fear of the Relapse: Effect of Composite Type on Adhesion Efficacy of Upper and Lower Orthodontic Fixed Retainers: In Vitro Investigation and Randomized Clinical Trial

The aim of this laboratory and clinical study is to determine the reliability of the flowable nanocomposite Filtek Supreme XTE (FL) for the adhesion of orthodontic retainers, compared to highly filled orthodontic resin Transbond XT (XT). Portions of a round section multistranded wire (Ortosmail Krugg) were bonded to 40 bovine incisors with Scotchbond Universal in total-etch modality. For group one (XT, 20 samples), the orthodontic resin was used, whereas in group two (FL, 20 samples), the flowable one. Specimens were placed into a universal testing machine which applied a shear force on retainers with a crosshead speed of one/minute. Shear bond strength (SBS) and adhesive remnant index (ARI) scores were calculated. In the clinical trial, 100 patients requiring a canine-to-canine palatal and lingual retainer were randomly divided into two groups, according to the resin used for bonding procedure: the orthodontic in group one (XT, 50 participants) and the flowable in group two (FL, 50 participants). Monthly visits were carried out over a 24-month follow up to assess any detachment occurring on teeth of both arches. All data were submitted to statistical analysis. In vitro, FL reported a significant lower mean SBS, whereas no significant differences in ARI were reported between the two groups which both showed a major frequency of scores “1” and “2”. At the end of the 24-month follow up, FL reported significantly higher failure rates in both arches besides a significantly lower survival rate starting from the sixth month after retainers bonding. According to the results assessed in vitro and clinically, XT would be preferable to FL when performing retainers bonding procedure.

Main the Oretical Provisions of Grain Material Separation in Air Channels with Unequal Air Flow Speed

The article considers the increase of efficiency of grain materials separation in pneumatic vertical channels by determining the rational shape and parameters of material supply, as well as the geometric shape of the pneumatic channel and options for separation into fractions. Regularities of change of trajectory and speed of movement of material in pneumatic vertical channels of round section with the lower unloading of material are received. The regularities of particle motion in the form of a material point were determined taking into account air resistance forces, friction forces, Magnus and Zhukovsky forces, material moisture and density based on a theoretical study of grain fractionation in pneumatic vertical channels. Using the proposed dependences for the design of air separators, it is possible to determine the initial rate of introduction and the direction of entry of grains into the air stream, which are the initial conditions for determining the trajectory of material in air channels with lower material discharge.

EXPEDIENCY OF CHOICE OF CARDBOARD — POLYETHYLENE PIPES OF ROUND SECTION AS UNEXTRACTIVE PUSTOTOOBRAZOVATELEJ FOR MONOLITHIC REINFORCE-CONCRETE BEAM FLAGS OF CEILING

A study sent to the search of the most effective construction of unextractive pustotoobrazovatelej with the purpose of decline of weight and cost of monolithic reinforce-concrete beam flags of ceiling is undertaken in the article. The selection of materials is executed for unextractive pustoobrazovatelja on the basis of comparison of different materials on energy consumptions on their production. The new construction of unextractive pustoobrazovatelja is reasonable and offer with the use of cardboard-polyethylene pipe of round section. Recommendations are given on the parameters of pustoobrazovatelja depending on length of flight of ceiling flag. The methods of testing, analysis, design, study, comparison and generalization are applied. On the basis of comparison of totality of properties of different pustotoobrazovatelej (form, durability, inflexibility, moisture resistance, volume of substituting for a concrete, industrial applicability, labor intensiveness, jenergozatratnosti) the best pustotoobrazovatelem appeared offered cardboard-polyethylene pustotoobrazovatel’ made from the cardboard pipes of round section covered by polyethylene tape in 0,045 mm thick.

Reducing Surgeon's Physical Stress in Minimally Invasive Neurosurgery

Background and Study Aims Various minimally invasive approaches are used in neurosurgery. Surgeons must perform nondynamic fine movements in a narrow corridor, so specially designed surgical devices are essential. Unsophisticated instruments may pose potential hazards. The purpose of this study was to assess the factors associated with muscle fatigue during minimally invasive neurosurgery and to investigate whether physical stress can be reduced by refining the devices used. Material and Methods Four physical aspects of a handpiece were investigated: torque of conduits (0.20, 0.28, and 0.37 kgf*cm), shape of hand grip (five types), angle of the nozzle (0, 20, and 40 degrees), and weight balance (neutral, proximal, and distal). To evaluate muscle fatigue, surface electromyography was recorded from the extensor carpi radialis muscle and flexor carpi radialis muscle during a geometric tracing task. The maximum voluntary contraction (MVC) of each muscle and %MVC (muscle contraction during a task/MVC × 100) were used as the indexes of muscle fatigue. Results The shape of the hand grip significantly reduced %MVC, which is associated with muscle fatigue. The torque of conduits and angle of the nozzle tended to reduce muscle fatigue but not significantly. Weight balance did not affect muscle fatigue. Based on these results, we made two refined models: model α (torque of conduits 0.2 kgf*cm, angle of nozzle 20 degrees, neutral balance, hand grip with a 2.9 × 2.0-cm oval section with angled finger rest), and model β (torque of conduits 0.2 kgf*cm, angle of nozzle 20 degrees, neutral balance, hand grip with a 2.9-cm round section with a curved finger rest). The %MVC was significantly decreased with both types (p < 0.05 and p < 0.01, respectively), indicating reduction of muscle fatigue. Conclusions The geometrically refined surgical device can improve muscle load during surgery and reduce the surgeon's physical stress, thus minimizing the risk of complications.

Hydraulic studies of bottom regulatory devices

Introduction. Accidents at underwater pipeline crossings lead to serious environmental consequences. The choice of the location of the pipeline junction made without accounting the general dynamics of the channel process, use of improper construction technology of underwater trenches and pipeline laying often result in their destruction, which are caused by erosion and pipe sagging. Existing methods for protecting the pipeline by soil or crushed stone filling, exposure embedding with sandbags, strengthening with flexible concrete mats and other materials are not always effective and, as a rule, are expensive. Materials and methods. The article considers a method of protection of the main pipeline against erosion by means of through bottom devices of various types to determine their efficiency. Velocities of the flow are measured behind the bottom obstacles at the flow axis at several points in depth using the microcomputer flowmeter/velocimeter. The measuring sections are located at distances of 1 to 10 of flow depths from the bottom obstacles. The near-bottom velocities at the height of the roughness protrusions are calculated according to the dependences suggested by V.N. Goncharov. Results. The article shows results of laboratory hydraulic investigations of a tray flow around four types of bottom obstacle models: solid flat wall, slotted flat wall, volumetric round-section obstacle of fixed synthetic strings and volumetric soft structure. All the studied design models cause a rearrangement of the velocity diagrams and a decrease of near-bottom velocities. However, only through-passing structures are suitable for sediment deposition behind the barriers. If the bottom velocities are reduced to values less than sediment-washing ones, sediments will be deposited behind the barriers at a certain relative distance determined in the work. Conclusions. The investigated models of through bottom structures showed themselves to be quite effective in reducing the near-bottom speed and depositing sediments at a certain distance behind them. The most effective is the “volumetric” construction, since it gives the greatest reduction in relative velocities at a certain relative distance.