Abstract
Despite the decreases in temperature and permeability of oceanic plates with increasing age, hydrothermal circulation (HC) can be rejuvenated in the 130-Ma old Pacific plate in the vicinity ...of the Japan Trench, substantially affecting the thermal structure and remaining amount of magnetization (RAM). To decipher the roles of HC in the thermal structure and the RAM, the vigor and extent of HC in the vicinity of the Japan Trench should be quantitatively evaluated. Here we numerically show that HC is rejuvenated in the outer-rise zone but ceases after subduction owing to permeability evolution. The calculated thermal structure explains the measured heat flow evolution but negates the HC-driven thermal demagnetization, which was thought to decrease the RAM after subduction. Instead, we propose that the pressure-driven processes decrease the RAM after subduction through the demagnetizations of titanomaghemite and magnetite and the mineral phase transitions from maghemite to hematite.
Common-mode voltage (CMV) caused by switching operations of power converters can significantly degrade the system's stability and performance. Since the effects of the CMV are more prominent in the ...wide-bandgap-based applications that require fast-switching slew rates, many research articles have been proposed to mitigate CM noise generated by the CMV. In addition, as topologies and control methods of the power converters become more complicated for better performance, more advanced CM noise attenuation methods are required accordingly. Therefore, this article proposes a CM noise attenuation method using a multilevel active CM noise power filter in a five-level inverter system. In this article, detailed control methods and considerations of the proposed multilevel system are presented, and the validity of the proposed multilevel active CM noise power filter has been verified through experimental results.
Pulsewidth modulation (PWM)-based power electronics inverters are being widely used for various applications, including motor drives. However, the common-mode voltage (CMV) resulting from switching ...operations in the PWM inverters causes significant performance degradation of the system and can cause potential damage to motors. Since the effects of the CMV can be more severe in wide bandgap (WBG) and high switching frequency-based converter systems, various methods have been proposed to mitigate the CM noise issues. This work presents a multi-level inverter system composed of a multi-level inverter with a proposed multi-level active power filter (APF). For attenuating the CMV in multi-level inverters using multi-carrier-based PWM methods, a novel PWM method is presented for the proposed multi-level APF. The three-phase five-level active-neutral-point-clamped (ANPC) II-type inverter using the apparent switching frequency doubling (ASFD) PWM is used as an example of the multi-level inverters and carrier-based PWM methods to analyze and verify the proposed CMV attenuation method. The APF generates and injects the APF voltage equal to the CMV to attenuate the CM noise accurately. Various key challenges, including the dead-time compensation, are addressed through the proposed advanced PWM techniques to improve the CMV attenuation performance. Simulation and experimental results are provided to verify the comparison and effectiveness of the proposed CMV attenuation method.
•Continuous full scale thermophilic AD with thermal pretreatment was studied.•Thermal sludge pretreatment at 160°C for 30min was the optimum condition.•Total solids removal efficiency was 54.7% at ...3.50kgVS/m3·d.•0.35m3·CH4/kgVSadd was obtained at the sludge load lower than 2.49kgVS/m3·d.
A continuous full scale thermophilic anaerobic digestion (AD) of wastewater sludge in conjunction with thermal pretreatment was developed for enhanced CH4 production as well as sludge stabilization and reduction. Continuous thermal sludge treatment obtained 45.5, 51.7, and 26.1% of hydrolysis based on TS, VS, and COD at 160°C for 30min. After AD, TS, VS, and COD removal efficiencies reached 54.7, 60.4, and 59.2%, respectively, at 3.50kgVS/m3·d. Maximum CH4 yield (0.35m3 CH4/kg VSadd) was obtained at 2.49kgVS/m3·d and less, and the yield decreased with increasing sludge load while net available energy production increased. Continuous thermal sludge treatment and thermophilic AD enhanced CH4 production and solids reduction and showed stable performance for full scale application.
In this paper, an improved dead-time effect compensation is proposed for WBG multilevel inverters to eliminate dead-time voltage errors by zero-current clamping (ZCC) conditions. Conventional ...dead-time compensation methods based on the current direction can eliminate the dead-time voltage errors in the conventional dead-time methods. However, with the conventional dead-time compensation approaches, dead-time voltage errors remain uncompensated during the control cycles that include the ZCC point and its next control cycle. To address this issue, an additional improvement is proposed based on a prediction of the ZCC condition. is proposed to solve this issue. In this proposed method, the output current values of the next control cycles can be estimated by using the voltage references and feedback current information. Utilizing the estimated current, the proposed control scheme can predict each ZCC case and regenerate updated voltage references that can produce accurate output voltages without any dead-time voltage error. The proposed method is successfully implemented in a digital controller and verified through simulation and experiments.
► We deal with continuous wave ultrasonic anemometer (CWUA). ► This paper employs a phase delay circuit and a frequency divider. ► It is for expanding the measurable range of the phase difference. ► ...An algorithm was implemented for calculating the wind velocity. ► The error in the experimented wind velocity is less than ±1
μs.
This study was conducted to expand the measurement range of a continuous wave ultrasonic anemometer (CWUA) that uses phase difference measurement. A CWUA has a narrower measurement range than conventional ultrasonic anemometers because it can measure the phase difference up to the half-cycle of the used ultrasonic signals. In this study, a method of expanding the measurable range of the phase difference using a phase delay circuit and a frequency divider was developed. Through experiments, it was found that this method doubled or quadrupled the measurement range when the method was used. Furthermore, an algorithm for determining the validity of the measurement data by comparing them with the previous data was implemented with a wind velocity measurement error of less than ±1
μs to solve the problem caused by the use of the frequency divider and to produce a stable measurement system.
Gas atomized Fe–Si–Cr powder was used in the application of a bypass sheet in near field communication. The powder was ball-milled, annealed at different temperatures and then manufactured to the ...sheet. Changes in microstructure and magnetic properties were investigated by XRD, VSM and an impedance analyzer. The as-milled Fe–Si–Cr flake consisted mainly of disordered A2 and ordered B2 phases while the atomized powder consisted of A2, B2 and DO3 phases. Increases in the annealing temperature caused the formation of a DO3 phase. At temperatures higher than 923K, the final flake consisted of only A2 and DO3 phases. Grain size increased abruptly from 823K, while the size of the DO3 phase increased rapidly from 623K. Coercivity of the flake decreased after annealing, with the lowest coercivity obtained after 923K annealing while saturation magnetization showed a minimum value of 928kA/m after 523K annealing. Sputtered Fe–12%Si films showed a highest electrical resistivity value of 191μΩ·cm after 623K annealing while the resistivity of Fe–4%Si sputtered films decreased almost linearly with annealing temperature. Therefore it could be concluded that high permeability of the 623K sheet at 13.56MHz and low permeability of the 923K sheet at 80MHz were due to the high resistivity as well as nanostructure of the 623K flake.
•Phase analysis in the atomized, milled and annealed powder by XRD.•Relationship between permeability and microstructure.•Variation of resistivity of Fe–Si films with annealing temperature.
We investigated nano-floating gate memory having a charge trap layer (CTL) composed of cobalt germanide nanostructure (ns-CoGe). A tunneling oxide layer; a CTL containing Co, Ge, and Si; and a ...blocking oxide layer were sequentially deposited on a p-type silicon substrate by RF magnetron sputtering and low-pressure chemical vapor deposition. We optimized the CTL formation conditions by rapid thermal annealing at a somewhat low temperature (about 830 °C) by considering the differences in Gibbs free energy and chemical enthalpy among the components. To characterize the charge storage properties, capacitance–voltage (C–V) measurements were performed. Further, we used X-ray photoelectron spectroscopy for chemical analysis of the CTL. In this work, we not only report that the C–V measurement shows a remarkable opening of the memory window for the ns-CoGe compared with those of nanostructures composed of Co or Ge alone, but also clarify that the improvement in the memory characteristics originates in the nanostructure formation, which consists mainly of Co-Ge bonds. We expect ns-CoGe to be a strong candidate for fabrication of next-generation memory devices.
•We investigated nano-floating gate memory having a charge trap layer (CTL) composed of CoGe nanostructure (ns-CoGe).•A tunneling oxide layer, a CTL and a blocking oxide layer were sequentially deposited on a p-type silicon substrate.•The CTL can be formed at a low temperature by considering the Gibbs free energy and chemical enthalpy of the constituents.•C–V measurement shows a remarkable memory window for the ns-CoGe compared with those composed of Co or Ge alone.•The improvement in memory characteristics originates from the nanostructure formation which consists mainly of Co-Ge bonds.
Fluid and melt transport in the solid mantle can be modeled as a two-phase flow in which the liquid flow is resisted by the compaction of the viscously deforming solid mantle. Given the wide impact ...of liquid transport on the geodynamical and geochemical evolution of the Earth, the so-called “compaction equations” are increasingly being incorporated into geodynamical modeling studies. When implementing these equations, it is common to use a regularization technique to handle the porosity singularity in the dry mantle. Moreover, it is also common to enforce a positive porosity (liquid fraction) to avoid unphysical negative values of porosity. However, the effects of this “capped” porosity on the liquid flow and mass conservation have not been quantitatively evaluated. Here, we investigate these effects using a series of 1- and 2-dimensional numerical models implemented using the commercial finite-element package COMSOL Multiphysics®. The results of benchmarking experiments against a semi-analytical solution for 1- and 2-D solitary waves illustrate the successful implementation of the compaction equations. We show that the solutions are accurate when the element size is smaller than half of the compaction length. Furthermore, in time-evolving experiments where the solid is stationary (immobile), we show that the mass balance errors are similarly low for both the capped and uncapped (i.e., allowing negative porosity) experiments. When Couette flow, convective flow, or subduction corner flow of the solid mantle is assumed, the capped porosity leads to overestimations of the mass of liquid in the model domain and the mass flux of liquid across the model boundaries, resulting in intrinsic errors in mass conservation even if a high mesh resolution is used. Despite the errors in mass balance, however, the distributions of the positive porosity and peaks (largest positive liquid fractions) in both the uncapped and capped experiments are similar. Hence, the capping of porosity in the compaction equations can be reasonably used to assess the main pathways and first-order distribution of fluids and melts in the mantle.
Gas atomized Fe-Si-Cr powder was used in the application of a bypass sheet in near field communication. The powder was ball-milled, annealed at different temperatures and then manufactured to the ...sheet. Changes in microstructure and magnetic properties were investigated by XRD, VSM and an impedance analyzer. The as-milled Fe-Si-Cr flake consisted mainly of disordered A2 and ordered B2 phases while the atomized powder consisted of A2, B2 and DO sub(3) phases. Increases in the annealing temperature caused the formation of a DO sub(3) phase. At temperatures higher than 923 K, the final flake consisted of only A2 and DO sub(3) phases. Grain size increased abruptly from 823 K, while the size of the DO sub(3) phase increased rapidly from 623 K. Coercivity of the flake decreased after annealing, with the lowest coercivity obtained after 923 K annealing while saturation magnetization showed a minimum value of 928 kA/m after 523 K annealing. Sputtered Fe-12%Si films showed a highest electrical resistivity value of 191 mu Omega times cm after 623 K annealing while the resistivity of Fe-4%Si sputtered films decreased almost linearly with annealing temperature. Therefore it could be concluded that high permeability of the 623 K sheet at 13.56 MHz and low permeability of the 923 K sheet at 80 MHz were due to the high resistivity as well as nanostructure of the 623 K flake.
