Saturation Mode Research Articles

Thermally and Optically Stimulated Luminescence Kinetics with Impeded Carrier Transport

A simplified model of thermally stimulated luminescence (TSL) and optically stimulated luminescence (OSL) kinetics is considered for the case of impeded carrier transport. A response function is obtained for the OSL with transport barrier, being of special interest for the extreme case of saturation mode (when the optical term in the model exceeds all other terms). In this case, the maximum of the response function does not depend on the stimulating light intensity but is proportional to the recombination rate, which in turn, depends on the transport barrier and temperature. A high barrier makes the OSL ineffective, whereas the elevated temperatures can increase OSL response for moderate barriers. If carriers released by light are transferred deeper to the respective energy band, they can overcome the transport barrier during their thermalization, which decreases the temperature required for OSL.

Observation of helical m/n = 1/1 saturated steady mode in EAST pure electron heating scenario with q0 ≼ 1

We observed for the first time a helical m/n = 1/1 (m is the poloidal mode number and n is the toroidal mode number) saturated steady mode (SSM) in the center of the EAST electron heating dominant plasma where the core safety factor was close to but slightly below unity and the profile had an extreme peak at the plasma center ( is the electron temperature). An internal crash can be caused by the dynamics of the SSM, and its influence on the electron temperature profile is as large as that of a typical sawtooth crash (SC) in magnitude. Due to the weak magnetic shear in the core, the SSM regularly exhibits an m/n = 2/2 harmonic component. For low shear auxiliary heated plasma, the SSM cannot cause the degradation of plasma confinement ( or ), but an SC is indeed a harmful factor. Three-dimensional resistive magnetohydrodynamic simulations with a realistic EAST strong elongated magnetic configuration, a high Lundquist number () and a strong central peaked pressure profile, have been made to demonstrate the formation of the SSM in the case of and the destabilization of the SC in another case with . These nonlinear simulation results agree well with the observations of both the SSM and SC in EAST electron heating dominant discharges with an extreme central peaked . An M3D simulation found that the SC is caused by additional newly developed harmonics of the m/n = 1/1 helical instability. Nonlinear simulation also predicted a modulation of the SSM on current in the plasma core, which is favorable for maintaining in the plasma core. Furthermore, nonlinear simulation also showed that a small toroidal plasma flow can be generated by the SC.

Reconstruction of the Internal-Wave Parameters in the Atmosphere from Signal Amplitude Fluctuations in a Radio-Occultation Experiment

In this paper, we discuss a method for reconstructing the parameters of internal gravitational waves (IGWs) in the stratosphere from amplitude fluctuations in satellite radio-occultation observations. In the formation of radio-signal fluctuations, IGWs play the main role in these observations, while the contribution of isotropic turbulence is negligible. We consider methodological issues: (1) the choice of a model for the spatial spectrum of internal waves, (2) the derivation of relations connecting the statistical parameters of the IGW spectra and amplitude fluctuations in the approximation of a phase screen and weak fluctuations, (3) the development of a reconstruction algorithm, and (4) the estimation of possible errors. The reconstructed parameters are the outer or dominant scale and the structural characteristic of the vertical IGW spectrum, which determines the spectral amplitude in the saturation mode. The operating range covers altitudes from 28 km to the upper boundary of the tropopause. The error estimates for the reconstruction algorithm are 10–20% for the outer scale and 20–40% for the structural characteristic.

Comparative Experiments on Lower Hybrid Wave Heating of Ions in High-Density Hydrogen and Deuterium Plasmas at the FT-2 Tokamak

In the framework of the isotope effect studies at the FT-2 tokamak, the efficiencies were compared of the lower hybrid wave heating of the ion components of the hydrogen and deuterium plasmas with high densities (close to the Greenwald limit, 〈ne〉 ≤ 1020 m–3). It was experimentally ascertained that, in accordance with the theoretical concepts, the efficient axial heating of the deuterium plasma ions occurs, as opposed to the peripheral heating of the hydrogen plasma ions. Such an isotope effect occurs due to the different localization of the plasma-RF wave interaction regions. The distinctive feature of these experiments is the fact that, in deuterium plasma, during the preliminary ohmic heating, the dependence of the energy lifetime on density τЕ(n) is linear (LOC dependence), and, with increasing density, the transition to the improved ohmic confinement mode occurs. In hydrogen plasma, on the contrary, the transition to the saturation mode is observed. In this study, the considerable decrease in τЕ was revealed, observed during the additional lower hybrid wave heating in both hydrogen and deuterium plasmas.

ATP 시스템의 발리스데이터 전송특성 시험 및 개선방안

The most functionally important component of an ATP system is the Balise transmission system for transmitting track signals and track conditions to a moving train. A Balise transmission system consists of a Balise on the track and an antenna on the train to enable transmitance of digital information to the train as it passes the Balise. The Balise and onboard antenna are simple and critical components of the ATP system that require continuous performance and reliability. The purpose of this study is to derive the technical characteristics of the Balise air-gap interface through various tests and analysis, and to suggest ways to ensure safety and reliability of the Balise transmission system. The result of the test show that when the magnetic field strength of the tele-powered signal transmitted from the onboard antenna is above a certain level, the uplink signal of the Balise operates in saturation mode, and the magnetic strength of the tele-powered signal does not affect the input/output characteristics. However, various tests in this study verify that the relative position and cross-link area of the two antennas greatly affect the input/output characteristics. As a result of sampling and testing the Balise used in Korean railroad, it was found that the uplink signal was generated near the threshold in certain products, which may cause a telegram decoding error in the BTM. It was confirmed that in order to solve this problem, that it is necessary to prevent the uplink signal from being generated in sections where the current value of the uplink signal induced in the onboard antenna is less than the threshold value of the Balise input/output characteristics.

Novel Low-Side/High-Side Gate Drive and Supply With Minimum Footprint, High Power Density, and Low Cost for Silicon and Wide-Bandgap Transistors

High-power silicon field-effect transistors as well as insulated gate bipolar transistors and particularly wide-bandgap semiconductor transistors typically need negative turn-off voltage for a secure off-state, resilience to spurious turn on, and rapid transition through the saturation mode. We present a gate driver configuration with compact and very efficient supply of the high and low sides of power transistor bridges with asymmetric bipolar control voltages without the need for costly and lossy isolated dc-dc converter and only low-voltage active components. The underlying negative voltage gate driver supply circuit consists of only a few cost-efficient components, its electrical potential is referenced to the source of the controlled semiconductor power switch, and its operation is synchronized with the gate driver output. It outcompetes the established use of isolated dc-dc converters in gate circuits with negative voltage needs with respect to cost, size, reliability, and efficiency. Importantly, the proposed negative voltage supply allows bootstrapping without the need for controllable high-voltage semiconductors for the sake of further cost reduction. We present detailed design rules of the circuit and experimentally validate circuit and control. In the automotive prototype implementation, size of the gate driver supply was reduced by 61%, cost by 57%, and loss by more than 16%.

A Study of the Temperature Modes of the Automatic Switch Contacts in Cutoff of Short-Circuit Currents

This paper considers processes of electric arc damping by automatic switches in the short-circuit mode. Certain conditions for facilitating a successful short-circuit arc damping are shown, such as the limitation of the short-circuit current amplitude by its active resistance, the reduction of the phase shift between current and voltage, and the amplitude loss in returning and restoring voltages. The article features oscillograms of currents and voltages in the short-circuit mode. Anode heating processes are also described within the framework of the process of arc burning (heat saturation mode) and after the change of polarity current transition through zero processes at the cathode in the temperature equalization mode. Mathematical models of processes at the cathode took into account the thermal flows of the ionic component and evaporation. The calculations were carried out with the average values of thermal coefficients for copper, as the arc base moves from contacts to contact holders, which are made of copper and its alloys. The results of the calculations proved the validity of the considered mathematical models of thermal processes at both the cathode and the anode.

Direct prediction of nonlinear tearing mode saturation using a variational principle

It is shown that the variational principle of multi-region relaxed magnetohydrodynamics (MRxMHD) can be used to predict the stability and nonlinear saturation of tearing modes in strong guide field configurations without resolving the dynamics and without explicit dependence on the plasma resistivity. While the magnetic helicity is not a good invariant for tearing modes, we show that the saturated tearing mode can be obtained as an MRxMHD state of a priori unknown helicity by appropriately constraining the current profile. The predicted saturated island width in a tearing-unstable force-free slab equilibrium is shown to reproduce the theoretical scaling at small values of Δ′ and the scaling obtained from resistive magnetohydrodynamics simulations at large Δ′.

Bifurcation transitions in dynamic systems of pulse voltage regulator

In this article bifurcations in nonlinear dynamical systems are considered and special attention is paid to bifurcations-crises, which are identified with catastrophes in systems. The qualitative change in the phase portrait that occurs when the parameter m of the system changes is called the bifurcation of the phase portrait. The value of the system parameter m = m0, at which bifurcation occurs, is called the bifurcation value of the parameter (or bifurcation point). Mathematical models are presented in unsaturated mode; in saturation mode. Sufficient conditions are given under which the Andronov–Hopf bifurcation takes place. Quantitative relations are determined for the conditions under which the Andronov–Hopf bifurcation takes place in the system. Numerical values of parameters are entered, at which the system takes a quite compact, but quite informative form.

Causes of anisotropy in thermal atomic layer etching of nanostructures

In this work, the authors have investigated the dependence of the anisotropy level in an atomic layer etching (ALE) process of Al2O3 on form factor constraints when the ALE process involves etching in non-line-of-sight locations beneath a silicon nitride mask. In the experiments described here, thermal etching of Al2O3 without the use of any direction-inducing plasma components was explored utilizing the well characterized hydrogen fluoride/dimethyl-aluminum-chloride atomic layer etching process. The degree of anisotropy was quantified by measuring the ratio of lateral etch rate of this process in comparison to the vertical etch rate as a function of process step time inside 60 nm holes of aluminum oxide. Inside these holes, the authors determined that the horizontal etch rates slowed to an amount of 19% compared to the vertical rate when short process times were used. For process times operating in the saturation mode of the ALE process, horizontal etch rates per cycle could be sped up to 71% of the vertical rate but never reached parity with the latter. The authors propose a simple mechanism for explaining the anisotropy dependence on process step time and applied a reduced-order algorithm to model it. In this model, the authors introduced fitting parameters for surface modification depths and reaction times to match the experimentally found etch results. Conclusions could be drawn regarding topological hindrance or tortuosity for reactants to reach surfaces in shaded areas under the mask and for reaction by-products to escape from these locations and the impact on etch rate. In addition, the authors recognize that this mechanism could explain the unwanted depth dependence of the etch rate per cycle in high aspect ratio structures.

Two-year performance of single-stage vertical flow treatment wetlands planted with willows under cold-climate conditions

Climate-related issues constitute an important obstacle for the development of treatment wetland (TW) applications in regions with freezing winter temperatures. The aim of the present study was to evaluate the efficiency of a new configuration of TWs based on the vertical flow (VF) configuration. The proposed TWs system is planted with a willow species (Salix miyabeana SX67) and including design adaptations for cold climate operation. Two different flow modes for winter-time operation were proposed: percolated and saturated with continuous artificial aeration. The pilot-scale systems were tested with municipal wastewater, at an organic loading ranging from 5 to 20 g CBOD5 m−2 d−1.The pilot TWs were successfully operated for 22 months despite freezing winter temperatures reaching as low as −32 °C. Willow development was normal, with evapotranspiration ranging from 19 to 23 mm/d in July 2017 for the pilot TWs at an organic loading of 10 g CBOD5 m−2 d−1. Organic matter removal efficiency was high for all pilot TWs, with an average 91% COD and 81% TSS removal. Nitrification was essentially complete during the summer period and remained high for pilot TWs operated under percolating flow mode in winter but was lower for the saturated flow mode, probably due to insufficient air supply. Our study confirms the successful application of a modified version of VF TW in regions with freezing air temperatures.

Electric heating and angular momentum transport in laminar models of protoplanetary discs

ABSTRACT The vertical temperature structure of a protoplanetary disc bears on several processes relevant to planet formation, such as gas and dust grain chemistry, ice lines, and convection. The temperature profile is controlled by irradiation from the central star and by any internal source of heat such as might arise from gas accretion. We investigate the heat and angular momentum transport generated by the resistive dissipation of magnetic fields in laminar discs. We use local 1D simulations to obtain vertical temperature profiles for typical conditions in the inner disc (0.5–4 au). Using simple assumptions for the gas ionization and opacity, the heating and cooling rates are computed self-consistently in the framework of radiative non-ideal magnetohydrodynamics. We characterize steady solutions that are symmetric about the mid-plane and which may be associated with saturated Hall-shear unstable modes. We also examine the dissipation of electric currents driven by global accretion-ejection structures. In both cases we obtain significant heating for a sufficiently high opacity. Strong magnetic fields can induce an order-unity temperature increase in the disc mid-plane, a convectively unstable entropy profile, and a surface emissivity equivalent to a viscous heating of α ∼ 10−2. These results show how magnetic fields may drive efficient accretion and heating in weakly ionized discs where turbulence might be inefficient, at least for a range of radii and ages of the disc.

PROBABILISTIC CHARACTERISTICS OF WIRELESS NETWORKS WITH INFRASTRUCTURE TOPOLOGY

Based on the analysis of the operation of networks IEEE 802.11 DCF, a function is proposed for determining the probability of frame transmission to a central node depending on the number of stations operating in saturation mode. The probabilities of collisions are calculated. Using a polynomial approximations an expression is obtained for the network throughput, which explicitly depends on the number of the simultaneously operating stations.

Temperature dependence of ER3+, YB3+ kinetic spectra in the gradient crystals of lithium niobate

The paper presents the data on temperature measurements of the luminescence kinetics spectra of lithium niobate crystals with gradients of Yb and Er concentrations. It was found that heating the samples in the temperature range of 300–473 K leads to an increase in the luminescence spectrum in the range of 1480–1680 nm for the Er3+,Yb3+:LiNbO3 crystal and to a decrease for the Er3+:LiNbO3 crystal. Measuring the dependence of the gain in the weak signal mode at a wavelength of 1546 nm made it possible to establish that the signal does not decay and does not enter the saturation mode up to the pump power of 500 mW.

BJT-Type Optical Phase Shifter With Small Power Consumption and Fast Response Time on a Silicon Photonics Foundry Platform

We demonstrate a novel optical phase shifter with a bipolar junction transistor (BJT) type of device structure based on the silicon photonics foundry platform. By operating such a device in saturation mode, we obtain measured output IEC-VEC characteristics very similar to those of an ideal diode, which has a nearly zero turn-on voltage and an extremely small differential resistance. The huge amount of injected current under a small voltage swing (0.1 V) in the operation window makes it possible to obtain significant plasma induced change of the refractive index in the optical waveguide with an extremely small driving-voltage. The device has a small foot-print (500 μm in length), but exhibits small static power consumption for the π phase-shift (Pπ: 4.1 mW), reasonable propagation loss (0.02 dB/μm), small driving-voltage (Vπ: 0.12 V), fast switching time (rise/fall <1.6/1 ns), a residue amplitude modulation (RAM) as small as 0.18 dB, and a very-low power consumption (0.45 mW) during dynamic operation.

Geochemical behavior and stabilization of spent sulfate-reducing biofilter mixtures for treatment of acid mine drainage

Sulfate-reducing biofilters operated in semi-passive or passive modes constitute an approach of choice for treatment of acidic mining effluents. The aim of the present study involved examining the behavior of biofilters after use based on two modes of management, namely in unsaturated and saturated media. Two acidophilic biofilters were investigated following their mixing with different alkaline industrial residues (i.e., 25% fly ash biomass or 30% aluminum red mud, or 10% kiln dust). Percolation column tests for a 330-d period indicated that aluminum red mud and lime kiln dust (to a lesser extent) are efficient materials for maintaining the pH neutrality of biofilter leachate and to reduce release of metals (i.e., Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in spent biofilters. The storage of biofilters in saturated mode also makes it possible to preserve the reducing conditions of the environment and neutrality of the pH and to limit the dissolution of the solution of cadmium, nickel and zinc. Conversely, increased iron release is noted under saturated conditions. Finally, the results indicated that a mixture of biofilters and lime kiln dust is preferable to surface addition of these to reduce the loss of metals in leachates.

Robust control with an anti-windup technique based in relaxed LMI conditions for LTV system

This paper proposes a new technique to address the anti-windup (AW) with model predictive control (MPC) scheme for linear time-varying (LTV) systems. The main advantage of this new approach is the reduced conservativeness compared with other well-known anti-windup techniques and to prevent integration windup in MPC controllers when the actuators are saturated. The control with AW is applied in a three-state switching cell (3SSC) DC-DC converter operating under saturation conditions. The MPC with proposed anti-windup is compared with the MPC technique and with MPC-AW without relaxation. The MPC-AW with relaxation improves the performance when the converter operated in the saturated mode and allows the rational use of the converter. The simulation results validated the efficiency of the proposed approach and showed that the proposed approach not only allows working better with the polytope modeling but also improves the response under LTV disturbance.

The influence of carburization technology on performance properties of high-loaded gear wheels

The purpose of the study is to develop a technology for vacuum carburization of heat-resistant steels, taking into account the requirements for the structure of the carburised layer to ensure the operational properties of gears.The paper describes the issues of improving the operating characteristic of heavily loaded gears made of high-strength steels. Information on the modes of vacuum cementation is given. A technological process has been developed that ensures the presence of carbides on the tooth profiles, the absence of a carbide mesh in the cemented layer and the optimal mechanical properties of the gears. Recommendations on the choice of modes of diffusion saturation to ensure wear resistance, contact endurance, bending strength of gears made of heat-resistant steels are proposed.

Efficient use of microwave EMF and multilevel high temperature sterilization modes in apple puree technology for dietetic nutrition

The article is dedicated to improving the quality of apple puree with xylitol for dietetic nutrition due to the development and implementation of a new technological process. This is microwave boiling of apples, rather than traditional steaming using saturated steam before chopping, with the development of a device for its implementation and multilevel high-temperature sterilization modes with prebake of apple puree in glass jars in microwave EMF. The analysis of research and technical data proved that pre-heat treatment of apples with saturated steam and traditional sterilization modes have a considerable duration, which impairs the finished products quality and has an adverse effect on the nutrient composition of the raw material during processing. Substituting the traditional method of pre-heat treatment of apples for their short-time processing in microwave EMF reduces the process by more than twice, which, in turn, contributes to an increased preservation of the nutrient composition of apples, while enhancing the yield of apple puree. For the implementation of microwave processing method of raw materials, a new design of the device for electromagnetic treatment of plant roughage has been developed, providing a uniform and more intensive heat treatment of raw materials in a continuous flow. Rapid multilevel high-temperature sterilization modes with the application of apple puree in glass jars in microwave EMF, liquid high-temperature heat devices and an autoclave basket, providing the opportunity for thermal sterilization of the product without creating reverse pressure in the machine, generally contribute to reducing heat costs and increasing the nutritional value.

Temperature modes of the contactor contacts during the test for the limiting breaking capacity

The processes of electric arc quenching of an electromagnetic contactor during testing for ultimate breaking capacity are considered. The conditions for facilitating the successful arc quenching when turning off the limiting currents are shown: by reducing the phase shift between current and voltage, by reducing the amplitude of the restriking and recovery voltages. The processes of anode heating during arcing (heat saturation mode), after the change of polarity and transition of the current through zero, processes on the cathode in the temperature equalization mode are considered. The mathematical models of cathode thermal processes adressed the heat fluxes of the ionic component and evaporation. The mathematical models of anode thermal processes in the temperature equalization mode took into account the heat fluxes of the ionic component, thermionic emission, and evaporation. The calculations were carried out for the averaged values of thermophysical coefficients for copper, since the arc base moves from the contacts to the contact holders, which are made of copper or its alloys. The calculation results showed that the used mathematical models of thermal processes are appropriate both for the cathode and for the anode. This was confirmed by the results of previously performed and published experimental and theoretical studies of thermal processes at the switching contacts of electrical devices.