DC Recovery Research Articles

Current research status of ionic polymer–metal composites in applications of low-voltage actuators

Bending response images of an IPMC actuator under the same DC voltage and recovery process diagram after removing the voltage.

VDCOL Parameter Optimization Method for Improving Voltage Stability of DC Receiving Terminal Power Grid

This research based on different startup and operation modes of Heilongjiang receiving power grid, The influence of anti disturbance capability of converter bus on DC recovery characteristics. A VDCOL parameter optimization configuration scheme based on multi feed short circuit ratio (MSCR) is proposed. Through the DC near fault simulation analysis, it is verified that the proposed VDCOL parameter optimization scheme reduces the overall wattless power demand of converter station, and improve Heilongjiang receiving-end grid voltage stability.

Improvement of Autonomy, Efficiency, and Stress of Fuel Cell Hybrid Electric Vehicle System Using Robust Controller

Among issues facing the transportation sector today is the limited autonomy of electric vehicles, which are highly reliant upon energy storage systems. Considering this issue as the current research gap, researchers seek to prolong vehicle dependability through renewable-free and sustainable energy that tackles negative environmental impacts. This research exploits the electric vehicle’s kinetic energy to improve its performance and reliability. It uses fuel-cell resources and supercapacitors hybridized with lithium-ion batteries, in addition to DC generators connected to front wheels that convert their rotations into energy contributing to the vehicle’s overall power balance. A state machine-based energy management strategy computes fuel-cell setpoint power, while a dual-loop structure uses a super-twisting controller for DC bus voltage regulation and recovery, in addition to tracking banks’ setpoint currents. A speed controller-based artificial intelligence is proposed to reduce power losses and enable accurate tracking of running trajectory to improve vehicle mechanisms. The simulation results using Matlab Simulink software proved the proposed vehicle’s feasibility by adopting the free kinetic energy of additional DC generators that provided 28% of its total power requirements, resulting in superior supply efficiency reaching 98%. Thus, the stress on FC and battery was minimized by 21% and 10%, respectively, in addition to reducing fuel consumption by 39%, so the vehicle autonomy was extended, and its reliability was enhanced and supported, as targeted.

A Three-Parameter Adaptive Virtual DC Motor Control Strategy for a Dual Active Bridge DC–DC Converter

Increasingly more power electronic devices are being connected to DC microgrids, which reduces the inertia of a DC microgrid, and the DC bus voltage has poor resistance to disturbance. Adding a virtual DC motor control to the converter can effectively suppress the fluctuation of the DC bus voltage; however, due to the fixed inertia and damping parameters, the system cannot attain a good dynamic performance. On this basis, a two-parameter adaptive virtual DC motor control is proposed to realize flexible change both in terms of inertia and damping, which improves the stability of the DC bus, and the system has good dynamic performance under this control. To further improve the stability of DC bus voltage and the flexibility of the microgrid control, in this paper, a dual active bridge (DAB) DC–DC converter controlled by dual phase shift (DPS) is taken as the research object, a three-parameter adaptive virtual DC motor control strategy is proposed to realize the flexible adjustment of inertia, damping, and armature resistance at the same time, and meanwhile, optimize the backflow power and inductor current stress of the converter. Finally, simulation and experiment results show that the proposed three-parameter adaptive control strategy compares with the two-parameter adaptive control strategy, and it can further reduce DC bus voltage fluctuation and recovery time, which improve the stability of the DC bus and the dynamic performance of the system. The DC bus voltage fluctuation rate under the three-parameter adaptive control is reduced to 9%, and the voltage recovery time is only 0.18 s; the optimization strategy can also effectively reduce the backflow power and inductor current stress.

Michelson interferometer based phase demodulation for stable time transfer over 1556km fiber links.

Time transfer based on phase modulation schemes has attracted extensive attention in recent years. We propose and experimentally demonstrate an adjustable and stable Michelson interferometer (MI) with a DC phase tracking algorithm for two-way time transfer. Time signal with one pulse per second (1 PPS) is loaded on an optical carrier modulated in phase and demodulated by a Michelson interferometer. The whole compact and cost-effective demodulator is symmetrical with a single coupler to split and recombine optical waves, flexible with one photodetector and a bias tee to separate the DC signal and recovery pulses and stable with a phase modulator to compensate for the drift-phase noise. We show the implementation of modulation and demodulation of the time signal and obtain the stability of 2.31 × 10-11 at 1000 s averaging time. We then demonstrate two-way time transfer over 1556 km lab fibers. The experimental result shows time interval stability of 1 PPS with 5.62 × 10-11 at 1000 s averaging time. It has the potential to transfer time signals in long-distance fiber optic links.

DC Component Recovery in Kramers-Kronig Receiver Utilizing AC-Coupled Photo-Detector

The Kramers-Kronig (KK) receiver has recently drawn a great deal of attention due to its capability to extract the complex-valued electric field of optical signal from the directly detected signal. One practical issue is the recovery of the DC component lost upon the reception using an AC-coupled photo-detector. Due to the nonlinear operation of KK algorithm, it is necessary to recover the DC value of the signal before executing the algorithm. A common method to estimate the DC component was to sweep the DC value added to the detected signal, while measuring the system performance metrics such as bit-error ratio (BER). In this article, we propose and demonstrate a simple one-step DC recovery method for KK receiver. By inserting a zero-padded preamble in the modulation data and measuring a couple of statistical averages of the detected AC-coupled signal, we can estimate the DC component accurately even when the carrier-to-signal power ratio (CSPR) is low. Thus, this method estimates the DC component rapidly without time-consuming and power-hungry signal processing such as demodulation and BER calculation. We carry out a series of computer simulations and experiments to measure the accuracy of the proposed method. The results show that the proposed method incurs negligible sensitivity penalties compared with the conventional DC-sweep method. Also, provided in this paper is the design guideline on the proposed method.

Simultaneous decolorization and deproteinization of α,ω-dodecanedioic acid fermentation broth by integrated ultrafiltration and adsorption treatments.

α,ω-Dicarboxylic acids (DC) are versatile chemical intermediates with different chain length. For biosynthesis of DC, to obtain the highly pure product via crystallization, it is required to remove pigments and proteins in fermentation broth. However, a trade-off between decolorization/deproteinization ratio and DC recovery during the purification process was found, which impeded DC production by fermentation. When ultrafiltration (UF) was applied to treat α,ω-dodecanedioic acid (DC12) broth, 93.4% of DC12 recovery, 80.5% of decolorization ratio and 61.7% of deproteinization ratio were achieved by a PES 3 membrane. However, the membrane technology could not effectively retain the pigments or proteins with low molecular weight when a high DC12 permeation was required. Meanwhile, the selected activated charcoal or macroporous resins were not good adsorbents for the present system. Furthermore, an integrated process for decolorization and deproteinization was developed. After filtration with PES3 membrane, an activated charcoal was used to remove the small proteins and pigments in the UF permeate. As a result, 91.4% of DC12 recovery, 94.7% of decolorization ratio and 84.8% of deproteinization ratio were obtained by such two-stage strategy. These results would serve as a valuable guide for process design and practical operation in subsequent industrial application.

Modeling of NBTI Kinetics in RMG Si and SiGe FinFETs, Part-I: DC Stress and Recovery

An ultrafast (10- $\mu \text{s}$ delay) measurement technique is used to characterize the negative bias temperature instability-induced threshold voltage shift ( $\Delta {V}_{T}$ ) in replacement metal gate-based high-K metal gate Si and SiGe p-FinFETs. The dc stress-recovery $\Delta {V}_{T}$ time kinetics, voltage acceleration factor (VAF), and temperature activation energy ( ${E}_{A}$ ) are compared for different germanium percentages (Ge%) in the channel and nitrogen percentages (N%) in the gate-stack. A comprehensive physical model framework based on uncorrelated contributions from the generation of interface ( $\Delta {V}_{\mathrm {IT}}$ ) and bulk oxide ( $\Delta {V}_{\mathrm {OT}}$ ) traps and hole trapping in preexisting defects ( $\Delta {V}_{\mathrm {HT}}$ ) is used to explain the measured data. The impact of Ge% and N% on $\Delta {V}_{T}$ , VAF, ${E}_{A}$ , temperature (T) dependence of VAF, and stress bias ( ${V}_{\mathrm {GSTR}}$ ) dependence of ${E}_{A}$ are quantified. The interface trap generation component is independently verified by direct-current ${I}$ – ${V}$ (DCIV) measurements.

Burst Mode Optical Receiver With 10 ns Lock Time Based on Concurrent DC Offset and Timing Recovery Technique

This paper describes a low-power, low-latency, 7–10 Gb/s burst-mode DC-coupled receiver for photonic switch networks. The receiver includes a transimpedance amplifier (TIA) followed by a three-stage differential amplifier. For burst-mode operation, DC and timing recovery loops work concurrently in the proposed architecture to achieve 5.8 ns lock time. The DC recovery loop employs a successive approximation algorithm to recover signal-dependent offset that takes only six cycles of C8 (1/8th of data rate) clock. The timing recovery uses a quarter-rate injection scheme that is immune to duty cycle distortion. The recovered clock jitter is 10 ps p-p for 10 Gb/s operation. The receiver consumes only 33 mW while operating at 10 Gb/s, and less than 2 mW (leakage power and bias circuit) during idle time. The completely inductor-less receiver occupies a 465 pm × 265 pm area in 0.13 pm technology.

A 100 Gbit/sec Interface for 4K/8K UHDTV Signals

A 100 Gbit/sec realtime interface has been developed specifically to transmit 4K and 8K ultrahigh-definition television (UHDTV) image formats. This 100 Gbit/sec interface can carry 8K/50p-60p/4:4:4/12-bit or 8K/100p-120p/4:2:2/10-bit image formats. The dc balance and clock recovery were secured by adopting the 8b/10b coding. A transmission distance of 2 km, the same as those of the HD/3G-SDI optical interfaces, was achieved by adopting the 1.3 $\mu \text{m}$ Quad Small Form-factor Pluggable 28 (QSFP28) optical module. The QSFP optical module has evolved and treats the data as $4\times28$ Gbits/sec. This 100 Gbit/sec interface can be the next-generation realtime interface that can cover all the 4K and 8K signal formats defined by SMPTE ST 2048–1 and ST 2036–1 as well as ST 274 and ST 296. It also maintains backward compatibility because its I/O supports HD/3G-SDI.

Degradation and recovery of iron doped barium titanate single crystals via modulus spectroscopy and thermally stimulated depolarization current

Understanding resistance degradation during the application of DC bias and recovery after removing the DC bias provides insight into failure mechanisms and defects in dielectric materials. In this experiment, modulus spectroscopy and thermally stimulated depolarization current (TSDC) techniques were used to characterize the degradation and recovery of iron-doped barium titanate single crystals. Modulus spectroscopy is a very powerful analytical tool applied during degradation and recovery to observe changes in the local conductivity distribution. During degradation, oxygen vacancies migrate to the cathode region, and a counter flow of oxygen anions migrates towards the anode. With increasing time during degradation, the distribution of conductivity broadens only slightly exhibiting crucial differences to iron doped strontium titanate. After removing the DC bias, the recovery shows that a second previously unobserved and distinct conductivity maximum arises in the modulus data. This characteristic with two maxima related to different conductivities in the anode and cathode region is what can be expected from the published defect chemistry. It will be concluded that only the absence of an external electric field during recovery measurements permits the observation of local conductivity measurements without the presence of non-equilibrium conditions such as charge injection. Equilibrium conductivity as a function of oxygen vacancy concentration is described schematically. Oxygen vacancy migration during degradation and recovery is verified by TSDC analysis. We establish a self-consistent rationale of the transient changes in the modulus and TSDC for the iron doped barium titanate single crystal system including electron, hole and oxygen vacancy conductivity. During degradation, the sample fractured.

Transient evolution of mechanical and electrical effects in microelectromechanical switches subjected to long-term stresses

Application of two different biasing waveforms in long-term stresses in RF MEMS switches is used to separate mechanical and electrical effects. Three different effects are shown: 1) permanent mechanical degradation (creep effect) after the first stress and relaxation period; 2) transient mechanical degradation (viscoelastic recoverable mechanism); and 3) transient electrical degradation (recoverable charge trapping). Such effects are extracted by monitoring the evolution of the actuation and release voltages in different RF MEMS switches subjected to dc biasing and recovery tests. This paper highlights the mechanical and the electrical degradation components in long-term stress tests with the aim of quantifying the weights of the different contributions.

On-Chip Recovery Operation for Self-Aligned Nitride Logic Non-Volatile Memory Cells in High-K Metal Gate CMOS Technology

A new on-chip recovery operation is proposed in the self-aligned nitride (SAN) cell. Merged nitride spacer is sandwiched between high-k metal gate stacks in nano-meter CMOS process. The scaled gate length enables the SAN cell be erased by band-to-band hot hole. For multiple-time-programming operation, two effective recovery methods are proposed to recover on/off window after cycling stress. Both ac and dc methods are applied to eliminate deep-trapped charges via electrical self-heating. Experimental data demonstrates dc recovery methods that provide nearly full damage anneal capability and, in turn, effectively extend SAN cell’s endurance level.

Low levels of SDF-1α constrain DC recovery and diminish homeostatic proliferation of naïve CD4+ T cells during graft-versus-host disease. (TRAN3P.892)

Abstract Graft-versus-host disease (GVHD) is the major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (SCT) and its effect on T cell regeneration greatly increases the immunodeficiency normally associated with SCT. As a result, GVHD patients experience profound lymphopenia and lymphocyte reconstitution takes generally several months or years. The goal of this work was to assess the impact of GVHD on homeostatic proliferation (HP) of non-alloreactive naïve CD4+ T lymphocytes with the hypothesis that regeneration of the peripheral niche permissive to CD4 HP is constrained by GVHD. To study the impact of GVHD on the peripheral niche regulating CD4 HP, we used a Parent→F1 mouse model and observed a complete abrogation of CD4 HP in GVHD hosts. Loss of HP was related to depletion of all DC subsets as well as low levels of IL-7. While Flt3-ligand (FL) levels were normal, Stromal Derived Factor-1α (SDF-1α) was significantly diminished in GVHD mice. Administration of FL or SDF-1α significantly increased DC counts but CD4 HP was restored only when FL or SDF-1α was combined to IL-7. Importantly, while FL treatment aggravated GVHD, GVHD was improved by SDF-1α therapy. Our study shows that lack of immune reconstitution of CD4+ T cells is primarily due to failure of DC recovery owing to diminished SDF-1α production and diminished IL-7 and that the combination of SDF-1α and IL-7 could be used to enhance CD4 HP in GVHD hosts.

Control of DC-Fault-Resilient Voltage Source Converter Based HVDC Transmission System under DC Fault Operating Condition

Voltage source converter (VSC)-based high-voltage direct current (HVDC) transmission systems have attractive advantages compared to classical thyristor-based HVDC transmission systems. However, VSC-based HVDC transmission systems are vulnerable to dc side fault, and expensive dc circuit breakers are required to protect them against dc fault. This paper proposes a control method of a dc fault-resilient VSC which can be protected against dc fault without using expensive dc circuit breakers. In the VSC configuration, several H-bridge modules are connected in cascade, so the voltage balancing control of several floating dc capacitors is required. In this paper, an appropriate control structure with the capacitor voltage balancing controller is proposed. The appropriate control algorithm for dc fault operation and recovery after dc fault is also proposed. PSCAD simulation results are presented to validate the proposed control structure under normal and dc fault operating conditions. Real-time-digital-simulator results are also presented to verify the control structure.

NK cells are necessary for recovery of corneal CD11c+ dendritic cells after epithelial abrasion injury

Mechanisms controlling CD11c(+) MHCII(+) DCs during corneal epithelial wound healing were investigated in a murine model of corneal abrasion. Selective depletion of NKp46(+) CD3- NK cells that normally migrate into the cornea after epithelial abrasion resulted in >85% reduction of the epithelial CD11c(+) MHCII(+) DCs, normally present during and after epithelial wound closure. Transfer (i.v.) of spleen NK cells into NK cell-depleted mice significantly restored levels of corneal epithelial DCs (P<0.01). Immigrated NK cells were predominately positive for IFN-γ, and topical corneal anti-IFN-γ reduced epithelial DCs by 79% (P<0.01). IFN-γ(-/-) mice had 69% fewer DCs than WT controls (P<0.01), and topical rIFN-γ applied to NK cell-depleted corneas increased epithelial DCs significantly (P<0.01). The contribution of ICAM-1, an adhesion molecule involved in leukocyte migration, expressed on healing corneal epithelium, was evaluated. ICAM-1(-/-) mice exhibited >70% reduction in epithelial DC recovery in the first 48 h after epithelial abrasion (P<0.01). These interventions reveal an early turnover of DCs in the epithelium after injury, and ICAM-1, NK cells, and IFN-γ are necessary for the immigration phase of this turnover.

Early evaluation of immune reconstitution following allogeneic CD3/CD19-depleted grafts from alternative donors in childhood acute leukemia

Graft engineering procedures for hematopoietic SCT (HSCT) may improve the chance of success in matched unrelated donor (MUD) and haploidentical donor transplantations. Successful donor immune reconstitution is important to mediate GVL effects in reduced-intensity conditioning (RIC) HSCT. We prospectively investigated early immune reconstitution and clinical outcome in 30 CD3/CD19-depleted MUD (n=15) or HP (n=15) HSCTs for high-risk childhood leukemia using a fludarabine-based RIC without serotherapy. The graft consisted of a mean of 10.5 × 10(6)/kg CD34+, 77 × 10(3)/kg CD3+ and 39 × 10(6)/kg CD56+ cells. After transplantation, 86% of the patients engrafted. In all, 13% of patients had >grade 3 acute GVHD. Natural killer (NK) cell, DC and T-cell recovery achieved normal values within the first 60 days after transplantation. DC recovery was dominated by the DC2(-) subset. NK-cell phenotype was altered and cytotoxicity was lower compared with their donors. EFS was 50±9% (73±11% for those in CR1 and 26±11% for those with advanced disease). Faster DC2(-) recovery was associated with better outcome, especially in the MUD setting. In summary, CD3/CD19-depleted HSCT with fludarabine-based RIC without serotherapy resulted in favorable patient survival, and rapid NK, DC and T-cell recovery.

Recovering DC Coefficients in Block-Based DCT

It is a common approach for JPEG and MPEG encryption systems to provide higher protection for dc coefficients and less protection for ac coefficients. Some authors have employed a cryptographic encryption algorithm for the dc coefficients and left the ac coefficients to techniques based on random permutation lists which are known to be weak against known-plaintext and chosen-ciphertext attacks. In this paper we show that in block-based DCT, it is possible to recover dc coefficients from ac coefficients with reasonable image quality and show the insecurity of image encryption methods which rely on the encryption of dc values using a cryptoalgorithm. The method proposed in this paper combines dc recovery from ac coefficients and the fact that ac coefficients can be recovered using a chosen ciphertext attack. We demonstrate that a method proposed by Tang to encrypt and decrypt MPEG video can be completely broken.

Clinical-grade myeloma Ag pre-loaded DC vaccines retain potency after cryopreservation

The use of myeloma Ag-loaded mature DC vaccines, cryopreserved in single-use aliquots, is an attractive immunotherapeutic strategy. In this study we investigated the retention of phenotype, viability and potency of DC vaccines after freezing and thawing. Plastic-adherent monocytes, derived from a steady-state leukapheresis, were cultured in serum-free media containing GM-CSF and IL-4. DC were loaded on day 6 with myeloma lysate (ML) or idiotype (Id) Ag and keyhole limpet hemocyanin (KLH), induced to mature on day 7 with CD40-ligand and cryopreserved on day 9. Seventeen clinical-scale cultures were evaluated for DC yield, recovery and immunophenotype after potency was validated with allogeneic mixed lymphocyte culture and Ag presentation assays. We produced 88 individual vaccines from 17 clinical-scale cultures. Median DC yield at harvest was 131 x 10(6) (range 37-375 x 10(6)) and median recovery of viable DC after thawing was 69% (range 11-100%). We confirmed viability (7AAD-), phenotype (CD14-, CD83+/CD40+, CD83+/CD80+, CD83+/CD86+, CD83+/CD54+, HLA-DR++) and the ability of the DC to present Ag and stimulate allogeneic T cells post-thawing. We have validated a serum-free culture system for the production of DC. Cryopreservation did not interfere with DC activity, allowed time for rigorous quality control (QC) and flexible scheduling of intranodal vaccination, and reduced the time to prepare multiple vaccines.

Dynamic performance of a STATCON at an HVDC inverter feeding a very weak AC system

This paper investigates the dynamic performance of the advanced static VAr compensator or STATCON at a high voltage direct current (HVDC) converter terminal where the AC system has a very low short circuit ratio (SCR). The STATCON is based on a nine-level GTO thyristor inverter. The studies include operating characteristics of the STATCON under various AC and DC disturbances. The simulation results are compared with other types of reactive power compensation options available for such applications. It is shown that the STATCON has clear advantages over the other compensators, in areas such as: fault response time; voltage support ability; and DC recovery, while operating with very weak AC systems.