Electrothermal Model of Coupled Inductors with Nanocrystalline Cores

The paper proposes a new electrothermal model of a coupled inductor containing a nanocrystalline core dedicated to the analysis of electrical energy conversion systems. The formulated model has a form of a subcircuit for SPICE. The model takes into account the influence of direct current, frequency, skin effect, temperature, self-heating, and mutual thermal couplings on the parameters and characteristics of the coupled inductors. The form of the developed model and the method of model parameter estimation are presented. The applied measuring system is presented. The results of measurements and calculations made with the use of the proposed model are presented and commented on.

Analysis of exact and approximating dependences of active resistance of a conductor on the current frequency based on the influence of skin effect

The operation of semiconductor power converters, which are part of tractionsubstations, frequency-controlled electric drives and other powerful nonlinear loads, cause asignificant emission of higher harmonics of currents to electrical networks. Higher harmonics ofcurrents in electrical networks cause a complex negative effect on the energy efficiency of thenetwork. The increase in power losses in the active resistance under the action of higher harmonicsis due to the increase in the root mean square value of the current and the action of the skin effect.Analytical expressions describing the dependence of the active and impedance of the electricnetwork on the current frequency are determined. Based on them, analytical expressions are obtainedfor the calculation of additional power losses under the action of higher harmonics of currents, whichare due to the skin effect. The dependences of the active resistance of the electric network on thefrequency of higher harmonics are determined on the basis of Bessel equations. The analysis of convergence of the received equations with the data of the international standard IEC 60287-1-1 iscarried out. For the high-frequency zone, simplified approximating dependences are given, whichdetermine the parabolic dependence of the active resistance on the frequency. Simplifiedapproximating dependences of active resistance on the frequency of higher harmonics are obtainedfor engineering calculations. The obtained equations can be used to determine additional powerlosses in the active supports of electrical networks, windings of electric machines, high-frequencytransformers from higher harmonics of currents at different nonlinear loads. In addition, the obtainedexpressions can be used to justify the use of filter-compensating devices.

THE NEW APPLIANCE IS USED FOR CIRCUMCISION

Нами получен патент на полезную модель Республики Казахстан №5782 от 22.01.2021, который с большой эффективностью используется для обрезания крайней плоти. Для отсечения листков крайней плоти применяется устройство для пирографии Stayer, снабженный трансформатором, генерирующий напряжение от 0 до 5 В., с частотой тока 50Гц, мощностью 40Вт., с твердым рабочим наконечником, регулируемым температурой от 450ºС до 750ºС. Применение устройства для пирографии Stayer для обрезания крайней плоти позволяет сократить время оперативного вмешательства, уменьшить травматичность воздействия и улучшить косметический эффект. За 2018-2020 годы было выполнено 500 операций с применением устройства для пирографии Stayer. При этом, среднее время операции составляло 10 минут. У всех детей достигнут хороший непосредственный и отдаленный клинический результат. We have obtained a patent for a utility model of the Republic of Kazakhstan №5782, 22.01.2021., which is used with great efficiency in circumcision of the foreskin. To cut off the foreskin sheets, a Stayer pyrography device is used, equipped with a transformer that generates a voltage from 0 to 5 V., with a current frequency of 50 Hz, a power of 40 W., with a solid working tip, adjustable temperature from 450 ° C to 750 ° C. The use of the Stayer pyrography device for circumcision of the foreskin allows you to reduce the time of surgical intervention, reduce the traumatic impact and improve the cosmetic effect. In 2018-2020, 500 operations were performed using the Stayer pyrography device. The average operation time was 10 minutes. All children achieved a good immediate and long-term clinical outcome.

Parametric Models and Process Map for Alternating Current Square-Waveform Welding of Heat-Resistant Steel

The demand for efficient processes through a comprehensive understanding and optimization of welding conditions continues to grow in the manufacturing industry. This study involves heat-resistant 2.25 Cr-1 Mo V-groove steel welding using the square-waveform alternating cur-rent. Experiments were conducted to build the relationship between input variables—such as current, frequency, electrode negativity ratio, and welding speed—and process performance, such as penetration, bay area, deposition rate, melting efficiency, percentage dilution, flux–wire ratio, and heat input. The process was analyzed in light of the defect-free high-deposition weld groove weld, the sensitivity to process parameters, and the optimization and development of the process map. The study proposes an innovative approach to reducing the cost and time of optimizing the one-pass-each-layer V-groove welding process using bead-on-plate welds. Square waveform welding creates a metallurgical notch in the form of a bay at the fusion boundary that can be minimized by selecting appropriate welding conditions. The square waveform submerged arc welding is more sensitive towards changes in current and welding speed than the frequency and electrode negativity ratio; however, the electrode negativity ratio and frequency are minor but helpful parameters to achieve optimal results. The proximity of the planned and experimental results to within 3% confirms the validity of the proposed approach. The investigation shows that 90% of the maximum deposition rate is possible for one-pass-each-layer V-groove welds within heat input and weld width constraints.

The Perspective of the Oncology Health Care Professionals on Educational Conferences

BACKGROUND: Continuous education is vital to update the knowledge of the health care professionals (HCPs) engaged in cancer management. We aim to explore the perspective of the oncology HCPs on oncology conferences. METHODS: A questionnaire was handed to the delegates and faculty of an oncology educational scientific conference in the Kingdom of Saudi Arabia (KSA). The questionnaire explored the perspective on the ideal number, duration and the educational value of such conferences. RESULTS: Medical oncologists represented 70.5% of the 78 responders. All responders attended oncology conferences in the preceding year with 24.4% have attended >9 conferences. The educational value of these conferences was rated 7.98/10. Two thirds are satisfied with the frequency of conducted event or desire more. Short (half to one day) meetings are preferred by 66.67% and the mean number of optimum educational events is 5.7 per year. Educational events were highly valued (score ≥ 8/10) as venues to meet colleagues. CONCLUSION: The findings suggest that the current frequency and scientific value of oncology conferences and educational events are satisfactory to the majority of the relevant HCPs in the KSA. More CME events of up to one day in duration seem to be desired.

Giant magneto resistance (GMR) sensors for non destructive testing

<p>The thesis investigates the use of giant magneto resistance sensors for eddy current testing in order to identify defects in steel pipes. An automated test rig which included the device under test, sensor array, excitation unit, electronic measurement equipment, mechanical setup and LabVIEW automation was designed and built. This was used to investigate the effect of excitation parameters such as current, frequency and distance to the pipe. Some preliminary algorithms to improve the signal were developed and tested. The effect of the shape and size of the defect and aluminum shield on the magnetic field was investigated. A qualitative model to describe the magnetic field, including measured defect signals, was developed. Minimum defect parameters and maximum distance values were evaluated in the context of signal to noise.</p>

Giant magneto resistance (GMR) sensors for non destructive testing

<p>The thesis investigates the use of giant magneto resistance sensors for eddy current testing in order to identify defects in steel pipes. An automated test rig which included the device under test, sensor array, excitation unit, electronic measurement equipment, mechanical setup and LabVIEW automation was designed and built. This was used to investigate the effect of excitation parameters such as current, frequency and distance to the pipe. Some preliminary algorithms to improve the signal were developed and tested. The effect of the shape and size of the defect and aluminum shield on the magnetic field was investigated. A qualitative model to describe the magnetic field, including measured defect signals, was developed. Minimum defect parameters and maximum distance values were evaluated in the context of signal to noise.</p>

Modeling the Effects of the Factors Affecting IGF in Coastal Areas and Variation of IGF in Jiaodong Peninsula of China Based on Finite Element Method

Based on finite element method, we develop a model of the induced geoelectric field (IGF) occurring in land-sea boundary regions during large geomagnetic field disturbances. The model is used first to study the effects of the changes in the lithospheric conductivity, ionospheric current, and ocean depth on the distribution of IGF in a typical land-sea boundary region. The results show that the changes in the lithospheric conductivity and ionospheric current (frequency, magnitude and direction) have major effects and ocean depth has minor effect on IGF in coastal areas. Then by incorporating a realistic 3-D conductivity variation of Jiaodong Peninsula (JDP) in China obtained from measured data, the model is used to simulate the IGF variation in JDP covering its land-sea boundaries for east-west and north-south ionospheric currents. The results show a new aspect that extremely large IGF development on the land side of the coastal bay areas perpendicular to the currnet compared to plane coastal areas. The results can stimulate detailed investigations of IGF (and GIC, geomagnetically induced current) in coastal areas.