High Frequency Currents Research Articles

A novel mechanical simulator for cannulation and sphincterotomy after Billroth II or Roux-en-Y reconstruction.

Introduction: In patients with Billroth II (B II) or Roux-en-Y anatomy, endoscopic retrograde cholangiopancreatography (ERCP) is demanding. Here, we describe a novel simulator with simulated fluoroscopy for cannulation and sphincterotomy training in such situations. Methods: A custom-made simulation system was built based upon a common chassis of a series of previously described ERCP simulators. The papilla is made out of organic material and can be cut by high frequency current. The advancement of guidewires and other instruments within transparent mock bile ducts can be viewed in the window of the simulator without the need for fluoroscopy. The ERCP B II/Roux-en-Y simulation system was first evaluated during an ERCP course. Results: There were no technical problems related to the novel simulator during the course. After sphincterotomy, the organic papillae could easily be exchanged within a few seconds. Overall, the novel B II/Roux-en-Y simulator achieved favorable results by trainees and expert endoscopists in all categories assessed. Conclusions: The new B II/Roux-en-Y mechanical simulator is simple and practicable. A first evaluation during an ERCP course showed promising results.

Combined methods of water disinfection – UV radiation in combination with other technologies

The results of the study of water disinfection using UV radiation in combination with other physical and chemical methods are shown in the article. Combined use of the different decontamination methods is expedient in cases where one of the methods hasn’t the requisite properties. In assessing the effect of the combined action of chlorine and UV disinfection it is shown no disinfection enhancement. Also, photolysis of chlorine compounds is not accompanied by the formation of undesirable byproducts. Combined use of US and UV treatment is characterized by high energy consumption, which makes this method not competitive for industrial use. Using high frequency currents entails higher costs in comparison with traditional method and therefore this method is not practical for widespread use. Using water ozonation provides the primary barrier against microbial contamination and reduces the amount of reagent that enables the use of the method for decomposition of complex organic compounds. Combined methods of UV radiation and other physical and chemical techniques (ultrasound, chlorination, microwaves) make it possible to solve complex and specific problems on a laboratory scale. Ozonation with UV radiation can be used for industrial purposes. The effectiveness of each of the studied techniques is based on the results of bacteriological analysis and characteristics of the object. The proposed UV combined methods for germicidal disinfection can be used for disinfection of not only drinking water and wastewater, and for a variety of objects of agriculture, food and medical industries.

Current sensorless control for half‐bridge based AC/DC PFC converter with consideration of conduction losses

SummaryThe focus of this paper is on a simple half‐bridge converter that performs power factor correction (PFC) using current sensorless control. Current sensors increase cost, auxiliary power required, conduction losses, and volume of the PFC converter. Moreover, measurement of high frequency current is demanding, especially in cost‐sensitive applications. The PFC converter proposed combines simple half‐bridge topology and improved current sensorless‐control algorithm that takes into account conduction losses. These losses influence volt‐second balance in the input inductor and result in distorted grid current shape. Their effect is especially evident in half‐bridge converter, where input inductor operates with high voltage swing. The current sensorless control method proposed compensates this influence and allows achieving sinusoidal current shape. First, the phenomenon of current distortion was shown with numerical simulation in PSIM package. Experimental prototype rated for 350 W power was built to verify theoretical and simulation results. Experimental results are in good agreement with those obtained with simulation and theoretically. The PFC converter proposed features low cost of realization and can be used in consumer equipment for connection to the grid. Copyright © 2016 John Wiley & Sons, Ltd.

Is a multi array-contact lead able to improve STN-DBS in Parkinson’s Disease?

Background Multi-directional electrodes in STN-DBS give the possibility to steer the high frequency current into the direction for clinical improvement and moreover recording of multi-array local field potential recordings (LFPs) give the possibility to determine the spatiotemporal distribution of oscillatory power across the STN that is related to the symptomatology in PD patients. Ultimately this information can be used as a feedback to optimize the stimulation parameters. Methods Eight PD patients were included in the study. After micro-electrode recording (MER), to determine the boundaries of the STN, temporarily a prototype of a new 32-contact DBS lead was inserted during the DBS procedure. Different modes of current steering were employed to improve motor symptoms and patients were scored on beneficial and adverse effects. Prior to and immediately after stimulation the distribution of spectral power was recorded by LFPs and spatiotemporal changes were evaluated with Fourier analysis. Results Thresholds of the effects of spherical stimulation were comparable to thresholds of stimulation through the conventional electrode at the same location in 89% of the cases. In eight of fourteen side effects, steering stimulation current increased the threshold for side effects by ⩾ 1 mA compared to spherical stimulation. The size of the therapeutic window could be widened in patient 6, 7 and 8 by steering stimulation in the posterior, posterior and anterior direction, respectively. LFP recordings prior to stimulation yielded the boundaries of the STN by showing increased spectral power particularly in the 13–40 Hz range. Recordings across all directions showed distinct spatiotemporal patterns of neuronal activity, which were related to the pattern of stimulation and the PD symptoms of the patient. Conclusions With a new DBS lead it is possible to steer stimulation current in STN-DBS such that it leads to a larger therapeutic window than with conventional spherical stimulation. Simultaneous LFP recordings across the entire STN provide spatial information about the location of the STN and its disease-related electrical activity. This may potentially be of benefit in predicting how to steer the current towards the sensorimotor part, while avoiding adverse effects.

NIKOLA TESLA AND MEDICINE: 160TH ANNIVERSARY OF THE BIRTH OF THE GENIUS WHO GAVE LIGHT TO THE WORLD - PART II.

Nikola Tesla (1856- 1943) was a genius inventor and scientist, whose contribution to medicine is remarkable. Part I of this article reviewed special contributions of the world renowned scientist to the establishment of radiology as a new discipline in medicine. This paper deals with the use of Tesla currents in medicine. Tesla Currents in Medicine. Tesla's greatest impact on medicine is his invention of a transformer (Tesla coil) for producing high frequency and high voltage currents (Tesla currents). Tesla currents are used in diathermy, as they, while passing through the body, transform electrical energy into a therapeutic heat. In 1891, Tesla passed currents through his own body and was the first to experience their beneficial effects. He kept correspondence on electrotherapy with J. Dugan and S. H. Monell. In 1896, he used high frequency currents and designed an ozone generator for producing ozone, with powerful antiseptic and antibacterial properties. Tesla is famous for his extensive experiments with mechanical vibrations and resonance, examining their effects on the organ ism and pioneering their use for medical purposes. Tesla also designed an oscillator to relieve fatigue of the leg muscles. It is less known that Tesla's inventions (Tesla coil and wireless remote control) are widely used in modern medical equipment. Apart from this, wireless technology is nowadays widely applied in numerous diagnostic and therapeutic procedures. Nikola Tesla was the last Renais- sance figure of the modern era. Tesla bridged three centuries and two millennia by his inventions, and permanently indebted humankind by his epochal discoveries.

Combined Diagnosis of PD Based on the Multidimensional Parameters

This paper presents a comprehensive multiparameter diagnosis method based on multiple partial discharge (PD) signals which include high-frequency current (HFC), ultrasound, and ultrahigh frequency (UHF). The HFC, ultrasound, and UHF PD are calculated under different types of faults. Therefor the characteristic values, as nine basic characteristic parameters, eight phase characteristic parameters, and the like are calculated. Diagnose signals are found with the method based on information fusion and semisupervised learning for HFC PD, adaptive mutation parameters of particle entropy for ultrasonic signals, and IIA-ART2A neural network for UHF signals. In addition, integrate the diagnostic results, which are the probability of fault of various defects and matrix, of different PD diagnosis signals, and analysis with Sugeno fuzzy integral to get the final diagnosis.

고조파발생에 따른 영향과 대책 연구

Skyscrapers, large business buildings, and IT consumers use many appliances, and the electrical power stems can cause fires by overheating. This can result in damaged capacitors, lost data, rising ground potential, and communication obstacles from linear or nonlinear high frequency. To make sure of that we investigated 7 spots of a building, among which 6-spots were fair but the other one needed high frequency control. Spots 3, 6, and 7 needed diagnostic workup, and spots 2, 3, and 5 considered 5 high frequency currents. A phase is all of good but the high frequency current is greater than the standard level except for spot 1. As a result, a zigzag transformer or active filter needs to be installed, and the efficiency needs to be upgraded by investigating load unbalance factors and power factors.

Harmonic Analysis of the Effects of Inverter Nonlinearity on the Offline Inductance Identification of PMSMs Using High Frequency Signal Injection

Offline inductance identification of a permanent magnet synchronous motor (PMSM) is essential for the design of the closed-loop controller and position observer in sensorless vector controlled drives. On the base of the offline inductance identification method combining direct current (DC) offset and high frequency (HF) voltage injection which is fulfilled at standstill, this paper investigates the inverter nonlinearity effects on the inductance identification while considering harmonics in the induced HF current. The negative effects on d-q axis inductance identifications using HF signal injection are analyzed after self-learning of the inverter nonlinearity characteristics. Then, both the voltage error and the harmonic current can be described. In addition, different cases of voltage error distribution with different injection conditions are classified. The effects of inverter nonlinearities on the offline inductance identification using HF injection are validated on a 2.2 kW interior PMSM drive.

NEW CONFIGURATIONS FOR HYBRID FILTERS TO IMPROVE POWER QUALITY

Reforms in Power Sector have given an opportunity to the consumer to demand Quality Power. Unbalance, Distortion and poor regulation in the supply voltage have detrimental effect on the life of equipment and leads to poor efficiency in operation. Variable speed drives, Electric Traction and Furnace Loads inject harmonic currents into the supply system creating Bus voltage distortion. Even linear loads connected to this Bus will experience distorted load currents. These high frequency currents do not generate any useful output but produce over heating of motors, increased reactive power demand and ripples in the generated torque causing vibrations, leading to failure and poor performance efficiency. So there is a need for bypassing the load current harmonics generated by nonlinear loads from entering the system Bus Conventionally passive tuned filters connected to the Bus are used for bypassing the harmonics, but these filters have many limitations and become less effective under some operating conditions. Advent of high frequency, high power switching devices has given rise to new tools to mitigate the harmonic distortion in the Bus Voltage by freewheeling the harmonic currents, these are generally called as Active Filters. There are many configurations of these filters. Many of the limitations faced by tuned passive filters are overcome by the use of Active filters, but by combining the tuned and active filter the reliability and affectivity in improving power quality is enhanced, these are called Hybrid Filters. This paper briefly deals with two new configurations of Hybrid filter, one based on Pulse Width Modulation (PWM) operated Voltage Source Converter and the other on Current Controlled Converter. Results of performance of these two filters applied to a simple distribution system with a nonlinear load are given.

Superhard oxide coatings formed on titanium treated by high-frequency currents

We have studied the hardness and elastic modulus of rutile (TiO2) oxide coatings formed on the surface of commercial grade VT1-00 titanium treated by high-frequency current (HFC). The mechanism of formation of superhard oxide coatings with thicknesses within 2–3 μm and submicron-grained structure consisting of prismatic crystallites with dimensions of 200–400 nm. It is established that, at high temperatures (within 1000–1200°C) and short HFC treatment durations (30–300 s), the oxide coatings are characterized by hardnesses of about 61–78 GPa and elastic moduli within 330–680 GPa.

Quality Improvement of Wear-Resistant Coatings in Plasma Spraying Integrated with High-Energy Heating by High Frequency Currents

The paper presents the results of metallographic and energy-dispersive studies of a wear-resistant coating structure made from high-chromium cast iron powder in the course of integrated plasma spraying and high-energy heating by high frequency currents (HEH HFC). The problem of determining the intensity and the nature of residual stress distribution in the depth of the hardened layer is solved by the finite element method and ANSYS and SYSWELD software systems. The results of numerical simulations were checked in field experiments using X-ray and mechanical methods for residual stress measurement. An optimum mode of fusion by high-frequency heating (the source specific power qs= (3.0 - 3.2) ∙ 108W / m2, relative velocity of parts Vd= 60 - 80 mm / sec) was determined. In doing so compressive residual voltage (σRS≈ -120 ± 10 MPa) was formed in the surface layer; the coating porosity reduced and the distribution uniformity of microhardness in the depth of the hardened layer improved. It was found that after plasma spraying of the surface of the part was characterized by a sufficiently developed non-uniform topography with a maximum deviation of high-altitude performance PV = 80 - 160 μm and roughness Ra = 25 μm ± 10 μm. After thermal reflow by high-frequency heating, roughness reduced significantly (Ra = 6 μm ± 2 μm) and the homogeneity of the material improved (PV = 4 ... 10 μm).

Depth Distribution of Temperature in Steel Parts during Surface Hardening by High Frequency Currents

Quenching of steel 45 using high-frequency induction-heating (440000 Hz) with simultaneous shower water cooling was studied. The possibility of liquid-phase creation in the bulk (appr. 0.2 mm) in the material being treated in the absence of melting on the surface was clearly demonstrated by both numerical simulation of the temperature field in the material during hardening and experimental results

Electromigration induced stress evolution under alternate current and pulse current loads

Stress evolution in a metal line embedded in a rigid confinement caused by the arbitrary wave-form time-dependent current loads is resolved by a direct analytic solution of the one-dimensional (1-D) Korhonen's equation. Electromigration induced stress buildup and relaxation kinetics resulted by time-dependent current density are obtained as functions of the relevant physical parameters. A novel methodology for physics based conversion between the time-dependent and effective DC current densities is developed based on a condition of equal void nucleation times resulted by these currents. It is shown that in the case of high frequency currents, with periods much smaller than the characteristic time of stress evolution, the stress buildup is proportional to the pulse duty factor. It is demonstrated that very short metal lines with preexisted thermal voids loaded with symmetrical bi-directional currents can demonstrate a notable resistance increase when a specific temperature oscillation is generated in the line by active devices of the integrated circuit.

Influence of upper hybrid resonance localized oscillation on X-B mode conversion efficiency for high-β National Spherical Torus Experiment in nonlinear regime

Ever increasing needs and capabilities in high power radio frequency waves heating and current drive scenarios of present and future magnetic confined fusion plasmas motivate expansion of understanding for vast variety of ever upcoming nonlinearities in such levels of power. Among many motivating experiments, one of the most relevant and actively studied in the regime for electron Bernstein wave (EBW) heating is high-β National Spherical Torus Experiment. A very special type of large amplitude electron plasma oscillations known as localized upper hybrid (UH) mode is demonstrated. It is shown that the mutual synergetic interaction of EBW and the localized UH mode can significantly shift the resonance layer about △x∼0.9 mm compared to the prediction of linear theory and consequently can explain the considerable reduction of conversion value around 35% observed in our modelling. This reduction is due to scale up of density scale length, Ln, at the new UH resonance (UHR) location followed by the increase of Budden parameter, η, which varies from 0.18 predicted by linear aspect to 0.40 in new position of UHR layer obtained by our modelling. Moreover, the parametric instabilities in the form of ion decays and dispersion of localized UH mode, approximately 7 mm due to the finite electron temperature account, are also observed which have an important contribution in reduction of conversion efficiency.

Review of Electrogravitics & Electrokinetics Propulsion

Electrogravitics and electrokinetics can be traced to T. Townsend Brown’s first article “How I Control Gravity” (Science and Invention, 1929) with the unexplained alignment of the “molecular gravitors”. Brown reported that the dielectrics had high propulsive force when the “differently charged elements” were aligned with the voltage source. Perhaps electrogravitics was also revealed in the article “Gravity Nullified: Quartz Crystals Charged by High Frequency Currents Lose Their Weight” which appeared two years earlier in the same magazine in September of 1927. The editors had a change of heart however, in the following issue, they rescinded the article. Much of what we know about T. T. Brown is from his numerous patents and articles, reprinted inElectrogravitics Systems Volume I, by this author who was fortunate to correspond with him in 1981 when he was at the University of Florida. A sample of his detailed correspondence is contained in the out-of-print book, Ether-Technology: A Rational Approach to Gravity-Control by Rho Sigma (1977) and in the recent Defying Gravity: The Parallel Universe of T. Townsend Brown, Paul Schatzkin, (2009, Embassy Books). Also, a five-minute Brown-Bahnson Lab video online shows many of the experimental models that Brown developed toward 1960 with colleague Agnew Bahnson (http://www.youtube.com/watch?v=Rp4hygoD3RU).

ПРОГНОЗИРОВАНИЕ ЭФФЕКТИВНОЙ ТОЛЩИНЫ СЛОЯ, ЗАКАЛЕННОГО ТОКАМИ ВЫСОКОЙ ЧАСТОТЫ, ДЛЯ ДЕТАЛИ «ОСЬ ПРОМЕЖУТОЧНОЙ ШЕСТЕРНИ ЗАДНЕГО ХОДА» ПО РАСЧЕТНОЙ ПРОКАЛИВАЕМОСТИ СТАЛИ 45

The study is performed on the example of “Reverse idler gear shaft” part made of 45 steel and covers the development of methodology of forecasting the effective thickness of a tempered by high frequency currents layer with the help of estimated hardenability, which uses data of metal acceptance test by chemical composition and grain size. The research is caused by the necessity of increase of the tempering equipment capacity and the reduction of working time for the estimated hardenability determination. The work was performed taking into account the lack of research in scientific literature containing the detailed description of methodology for forecasting of hardness and effective thickness of tempered with high frequency currents layer for the parts made of 45 steel using the estimated hardenability. In this research, the authors, firstly, analyzed the heat chemistry, secondly, determined the values of hardness depending on the layer effective thickness, and, thirdly, built the estimated hardenability curves using the Daido Steel (DS) method and the layer effective thickness dependences on the estimated hardenability. It was determined, that the above-mentioned dependences allow forecasting the layer effective thickness with the desired precision prior to the “HFC hardening” operation that serves as the basis for the proposed methodology implementation into production. The developed methods allow the following: - to reduce the working time for determining the effective thickness of a tempered with high frequency currents layer, as compared to the control in a specialized laboratory; - to eliminate in the existing production the necessity of control of the layer effective thickness after the “HFC hardening” operation, and therefore, to avoid the equipment downtime due to the use of data of the supplied metal acceptance test by chemical composition.

Numerical Modeling of Steel Surface Hardening in the Process of High Energy Heating by High Frequency Currents

Surface layer modification methods using concentrated energy sources to ensure high heating rates of approximately 104 – 105 °C/s are becoming increasingly common in an attempt to improve operational performance of machine components. As a result, it is quite difficult to determine heat cycle parameters by means of experiments to predict the required intensity and distribution behavior of residual stresses and strains. The paper addresses the issue of numerical simulation of the stress-strain behavior during high energy heating by high frequency currents (HFC HEH). A finite element model has been generated using the ANSYS and SYSWELD software based on numerical computations of differential equations for transient heat conduction (Fourier equation), carbon diffusion (Fick's second law), and the elastic-plastic behavior of the material. The simulation data was verified by full-scale experiments using optical and scanning microscopy and mechanical and X-ray methods to determine residual stresses. It has been established that the level of residual compressive stresses on the component surface can be from-500 to-1000 MPa within the range of HFC HEH process variations under review. It is proven in theory and confirmed by experiments that the transition layer thickness must amount to 25 – 33 % of the hardened layer depth for the tensile stress peak to shift to deeper material layers while compressive stresses on the surface decrease by 6 – 10 %, in order to prevent hardening cracks.

Integration of Production Steps on a Single Equipment

The article describes a new method for integrated processing which combines high-energy heating by high frequency currents (HEH HFC) and abrasive grinding. Research clearly showed that implementation of integrated processing may lead to 2 … 2.5-fold increasing of the processing performance. It was established experimentally that the proposed integrated treatment results in increasing of the microhardness and the level of residual compressive stresses in the surface layer. This increases the contact–fatigue strength of steel parts up to 10% … 16%.

영구자석형 동기발전기의 회전자 위치검출 센서의 옵셋 검출에 관한 연구

Abstract: In this paper, an algorithm is suggested to detect an offset angle of the absolute rotor position sensor after the initial assembly of a PMSG. Unlike previous studies in a stationary state, this one is not designed to detect an electrical angle but rather the absolute position of the rotor is detected while operating the generator. Also,a position sensor, current sensors and voltage sensor were used to ensure reliability. This technique completes the detection of the sensor offset in two steps. In the first step, a zero-crossing of the EMF is measured using a voltage sensor to detect the electrical angle offset when the alternator is actuated by the engine. In the second step, a high frequency current is injected along the d-axis on-line during the control of the generation, eventually to obtain the inductance using a DFT (Discrete Fourier Transform), and then to ultimately extract the final electrical angle offset through the comparison of the inductance magnitude. The suggested algorithm was validated with PSIM simulation and, furthermore, was tested with actual experiments on a dynamometer.Keywords: PMSG, initial position, zero-crossing, inductance, DFT (Discrete Fourier Transform)

Simulation of the response of nerve fibers to the applied interferential currents

Abstract Introduction: Interferential current is one of the most popular kinds of electrical stimulation that are used in electrotherapy. Despite its clinical popularity, there have been limited studies to investigate how this stimulation protocol affects the nerve fibers. This study was aimed to develop a realistic model for the stimulation of nerve fibers by interferential currents and using that to assess the spatial and temporal activation patterns of fibers in response. The effect of the modulation frequency on the resultant neural activity was also evaluated. Materials and Methods: A model of the target tissue, including the skin, fat and muscle layers was implemented in COMSOL software to obtain the potential distribution induced by the current inside the tissue. Then the MRG model of the myelinated nerve fibers in NEURON environment was used to simulate the response of fibers at different positions in the tissue. A 4 KHz carrier frequency with the modulation of 1 to 250 Hz and stimulus strength of 1 to 99 mA was used in this study. Results: The sensory fibers that are passing right beneath the electrodes are blocked in response to the applied high frequency currents and cannot conduct the action potentials. The sensory and motor fibers in other positions of the tissue can be activated based on the stimulus amplitude and the modulation frequency. The temporal activation pattern is at frequencies equal or twice of the modulation frequency. The excitation thresholds for fibers in a specific depth of the tissue are different based on their position relative to the electrodes, and even fibers that are outside the borders of the four electrodes can be activated. Conclusion: The results demonstrate how the block of sensory fibers may decrease the patient discomfort, and suggests that non-target fibers outside the region of electrode placement may also affected by the stimulation. Moreover, the results confirm the traditional claims about role of the modulation frequency in the firing frequency of nerve fibers. Keywords: Electrotherapy, Transcutaneous Electrical stimulation, Nerve fiber, Interferential Current, Simulation.