The Dynamic Volt-Ampere Characteristics of a Vacuum Arc at Intermediate-Frequency Under a Transverse Magnetic Field

In this study, the changes of a vacuum arc＇s appearance were observed and the volt-ampere characteristics of the vacuum arc at intermediate frequency were analyzed under a transverse magnetic field （TMF）. The TMF and phase shift time were calculated by using the TMF contact model and the large phase shift of the magnetic field at a higher frequency was conductive to the dispersion process of residual plasma. The arc velocity was higher at 800 Hz than at 400 Hz. It can be inferred that TMF will encourage arc movement at 800 Hz. Moreover, the arc movement has an impact on the arc voltage. Because of the increasing length of the arc column with a high arc velocity, the elongated arc causes the arc voltage to increase. Specifically, the volt-ampere characteristics of the vacuum arc are divided into three stages in this paper. The higher the frequency, the greater the initial rate of rise in the arc voltage and the larger the area surrounded by arc volt-ampere characteristics. The correlations between the arc voltage and the amplitude and frequency of the current are also presented.

Motion and Splitting of Vacuum Arc Column in Transverse Magnetic Field Contacts at Intermediate—Frequency

Arc motion and splitting of vacuum arc at intermediate frequency（400-800 Hz） were investigated under transverse magnetic field（TMF）.The experiment was performed on cup-type TMF contacts with contact diameter of 40 mm and a contact gap of 4 mm in a single-frequency circuit.With high-speed photography we characterized the arc appearance at different arc currents from 3.3 kA-rms to 10 kA-rms at intermediate frequencies.As arc current increases from3.3 kA-rms to 10 kA-rms the arc appearance changes obviously.When current value is 3.3 kArms（current frequency 400-800 Hz）,there is almost no splitting arc;when the current exceeds5 kA-rms（current frequency 400-800 Hz）,the arc rotates at a speed above 20 m/s,accompanied by an observable splitting arc.The splitting arc could be observed at different frequencies and the arc-voltage had no noises when splitting occurred.The motion direction and the velocity of arc column were studied.Finally,the formation of a split arc was discussed.

Interruption Phenomenon in Intermediate-Frequency Vacuum Arc

In the condition of the 3 mm gap, experiments for 360 Hz intermediate-frequency vacuum arc are carried out in interrupters with the diameters being 41 mm and with the contact materials being CuCr50 and Cu-W-WC alloy respectively. The results indicate that the contacts material is closely related to the breaking capacity of the vacuum interrupters and characteristics of an intermediate-frequency vacuum arc. For contacts with the same diameter, the breaking capacity of CuCr50 is better than that of Cu-W-WC. When the current fails to be interrupted, the arcs overflow the gap and present irregular performances in the first half wave. Consequently a voltage spike appears. More macroscopic metal droplets can be seen in the arc column between CuCr50 contacts because of the lower melting point. It is observed that the droplet emission is much more severe during arc reignition than that in the first half wave. It is much more conspicuous that the high frequency arc voltage noises appear in Cu-W-WC contacts when the vacuum arcs reignite, for higher temperature and stronger electronic emission ability of Cu-W-WC contacts.

Safety and efficacy of frequency-domain optical coherence tomography in evaluating and treating intermediate coronary lesions

AIM To establish whether frequency-domain optical coherence tomography(FD-OCT) is safe and effective in the evaluation and treatment of angiographicallyintermediate coronary lesions(ICL) METHODS Sixty-four patients with 2-dimensional quantitativecoronary angiography(2D-QCA) demonstrating ICL were included. OCT imaging was performed. According to predetermined OCT criteria, patients were assigned to either of 2 groups: OCT-guided percutaneous coronary intervention(PCI) or OCT-guided optimal medical therapy(OMT). The primary efficacy endpoint was to demonstrate the superiority and higher accuracy of FD-OCT compared to 2D-QCA in evaluating stenosis severity in patients with ICL. The primary safety endpoint was the incidence of 30-d major adverse cardiac events(MACE). Secondary endpoints included MACE at 12 mo and other clinical events.RESULTS Analysis of the primary efficacy endpoint demonstrates that 2D-QCA overestimates the stenosis severity of ICL in both the OCT-guided PCI and OMT groups, proving FD-OCT to be superior to and more precise than 2D-QCA in treating this subset of lesions. The primary safety endpoint was fully met with the incidence of 30-d MACE being nil in both the OCT-guided PCI and OCTguided OMT groups. Incidences of secondary endpoints were found to be low in both arms, the only exception being the relatively high incidence of recurrent episodes of angina which was, however, very similar in the 2 groups.CONCLUSION FD-OCT is safe and effective in the evaluation and treatment of ICL. Larger studies are needed to firmly establish the efficacy and safety of FD-OCT in treating ICL across all coronary artery disease population subgroups.

Research for the Dynamic Range and Its Extension of Digital Intermediate Frequency Receiver

For the optimization of dynamic range and bandwidth of digital intermediate frequency receiver(DIFR), main factors affecting them and their relationships are studied. Firstly, the DIFR sensitivity, bandwidth, noise factor of radio frequency (RF) analog front-end (RFAF), and processing gain of intermediate frequency(IF) sampling are analyzed. Secondly, the constraint relationship of the noise factor of RFAF, the signal-to-noise ratio of ADC and the dynamic range of DIFR are studied. The relationship between the dynamic range and the RFAF gain, and that of the extended dynamic range and the RF AGC(automatic gain control) step are educed and simulated. These results can be used as theory foundations and design references for the implementation and optimization of the large dynamic range and wideband DIFR.

A tunable passive mixer for SAW-less front-end with reconfigurable voltage conversion gain and intermediate frequency bandwidth

An adjustable mixer for surface acoustic wave( SAW)-less radio frequency( RF) front-end is presented in this paper. Through changing the bias voltage,the presented mixer with reconfigurable voltage conversion gain( VCG) is suitable for multi-mode multi-standard( MMMS) applications. An equivalent local oscillator( LO) frequency-tunable high-Q band-pass filter( BPF) at low noise amplifier( LNA) output is used to reject the out-of-band interference signals. Base-band( BB) capacitor of the mixer is variable to obtain 15 kinds of intermediate frequency( IF) bandwidth( BW). The proposed passive mixer with LNA is implemented in TSMC 0. 18μm RF CMOS process and operates from 0. 5 to 2. 5 GHz with measured maximum out-of-band rejection larger than 40 d B. The measured VCG of the front-end can be changed from 5 to 17 d B; the maximum input intercept point( IIP3) is0 d Bm and the minimum noise figure( NF) is 3. 7 d B. The chip occupies an area of 0. 44 mm^2 including pads.

Radio-frequency magnetron sputtered thin-film La_(0.5)Sr_(0.5)Co_(0.95)Nb_(0.05)O_(3-δ) perovskite electrodes for intermediate temperature symmetric solid oxide fuel cell(IT-SSOFC)

The present work explores the application of La_(0.5)Sr_(0.5)Co_(0.95)Nb_(0.05)O_(3-δ)(LSCNO)perovskite as electrode material for the symmetric solid oxide fuel cell.Symmetric solid oxide fuel cells of thin-film LSCNO electrodes were prepared to study the oxygen reduction reaction at intermediate temperature.The Rietveld refinement of syn-thesized material shows a hexagonal structure with the R-3c space group of the prepared perovskite material.Lattice parameter and fractional coordinates were utilized to calculate the oxygen ion diffusion coefficient for molecular dynamic simulation.At 973 K,the oxygen ion diffusion of LSCNO was 1.407×10^(-8)cm^(2)s^(-1) higher by order of one magnitude than that of the La_(0.5)Sr_(0.5)Co_(0.95)Nb_(0.05)O_(3-δ)(7.751×10^(-9)cm^(2)^(-1)).The results suggest that the Nb doping provide the structural stability which improves oxygen anion diffusion.The enhanced structural stability was analysed by the thermal expansion coefficient calculated experimentally and from molecular dynamics simulations.Furthermore,the density functional theory calculation revealed the role of Nb dopant for oxygen vacancy formation energy at Sr-0 and La-O planes is lower than the undoped structure.To understand the rate-limiting process for sluggish oxygen diffusion kinetics,80 nm and 40 nm thin films were fabricated using radio frequency magnetron sputtering on gadolinium doped ceria electrolyte substrate.The impedance was observed to increase with an increasing thickness,suggesting the bulk diffusion as a rate-limiting step for oxygen ion diffu-sion.The electrochemical performance was analysed for the thin-flm symmetric solid oxide fuel cell,which achieved a peak power density of 390 mW cm^(-2) at 1.02 V in the presence of H_(2) fuel on the anode side and air on the cathode side.

Properties of intermediate-frequency vacuum arc in sinusoidal curved contact and butt contact

In this report,two new contact structures of a vacuum interrupter with a sinusoidal curved surface are proposed to improve the capability by increasing the surface area.The experimental investigation of vacuum arc at intermediate frequency(360-800 Hz)was conducted and the results were compared with a butt contact with the same contact diameter(41 mm)and the same material.By analyzing the arc behavior,arc voltage characteristics,arc energy,current interrupting capacity,ablation of the anode contact and condensation of the arc products at a 3 mm gap,the differences in their vacuum arc characteristics were determined.The correlations of their arc energy with the amplitude and the frequency of the current were also achieved.Analysis suggests that the ruled curved contact has strong application potentiality because of its low arc energy,low arc voltage noise and arc voltage peak,light ablation on the surface of the anode contact and high interrupting capacity.

ZERO INTERMEDIATE FREQUENCY RECEIVER FOR MULTICARRIER MODE OF cdma2000

This paper proposes a novel zero Intermediate Frequency (IF) receiver for Multi-Carrier (MC) Direct-Sequence Code-Division Multiple Access (DS-CDMA) based on multicar-rier mode of cdma2000 system. The proposed receiver employs direct RF-to-baseband down-conversion, sampling at a rate equal to the bandwidth of the baseband multicarrier signal and complex-valued coefficient FIR filters. This receiver avoids the need for arrays of high Q analog bandpass filters, has a much lower sampling rate half of that of conventional receiver and offers significant savings in hardware implementation. Analytic and simulation results show that the presented receiver performs well for both the AWGN channel and Rayleigh fading channel.

The Primary Configuration and Formulae of the Intermediate Frequency Bend Machine

In this paper the primary configuration and formulae of design parameters of the intermediate frequency bend machine(  1450)are introduced and the main points of its design are explained.

Present and future of new systemic therapies for early and intermediate stages of hepatocellular carcinoma

Hepatocellular carcinoma(HCC)is a high mortality neoplasm which usually appears on a cirrhotic liver.The therapeutic arsenal and subsequent prognostic outlook are intrinsically linked to the HCC stage at diagnosis.Notwithstanding the current deployment of treatments with curative intent(liver resection/local ablation and liver transplantation)in early and intermediate stages,a high rate of HCC recurrence persists,underscoring a pivotal clinical challenge.Emergent systemic therapies(ST),particularly immunotherapy,have demonstrate promising outcomes in terms of increase overall survival,but they are currently bound to the advanced stage of HCC.This review provides a comprehensive analysis of the literature,encompassing studies up to March 10,2024,evaluating the impact of novel ST in the early and intermediate HCC stages,specially focusing on the findings of neoadjuvant and adjuvant regimens,aimed at increasing significantly overall survival and recurrence-free survival after a treatment with curative intent.We also investigate the potential role of ST in enhancing the downstaging rate for the intermediate-stage HCC initially deemed ineligible for treatment with curative intent.Finally,we critically discuss about the current relevance of the results of these studies and the encouraging future implications of ST in the treatment schedules of early and intermediate HCC stages.

High-Precision Doppler Frequency Estimation Based Positioning Using OTFS Modulations by Red and Blue Frequency Shift Discriminator

Orthogonal Time Frequency and Space(OTFS) modulation is expected to provide high-speed and ultra-reliable communications for emerging mobile applications, including low-orbit satellite communications. Using the Doppler frequency for positioning is a promising research direction on communication and navigation integration. To tackle the high Doppler frequency and low signal-to-noise ratio(SNR) in satellite communication, this paper proposes a Red and Blue Frequency Shift Discriminator(RBFSD) based on the pseudo-noise(PN) sequence.The paper derives that the cross-correlation function on the Doppler domain exhibits the characteristic of a Sinc function. Therefore, it applies modulation onto the Delay-Doppler domain using PN sequence and adjusts Doppler frequency estimation by red-shifting or blue-shifting. Simulation results show that the performance of Doppler frequency estimation is close to the Cramér-Rao Lower Bound when the SNR is greater than -15dB. The proposed algorithm is about 1/D times less complex than the existing PN pilot sequence algorithm, where D is the resolution of the fractional Doppler.

Pixelated non-volatile programmable photonic integrated circuits with 20-level intermediate states

Multi-level programmable photonic integrated circuits(PICs)and optical metasurfaces have gained widespread attention in many fields,such as neuromorphic photonics,opticalcommunications,and quantum information.In this paper,we propose pixelated programmable Si_(3)N_(4)PICs with record-high 20-level intermediate states at 785 nm wavelength.Such flexibility in phase or amplitude modulation is achieved by a programmable Sb_(2)S_(3)matrix,the footprint of whose elements can be as small as 1.2μm,limited only by the optical diffraction limit of anin-house developed pulsed laser writing system.We believe our work lays the foundation for laser-writing ultra-high-level(20 levels and even more)programmable photonic systems and metasurfaces based on phase change materials,which could catalyze diverse applications such as programmable neuromorphic photonics,biosensing,optical computing,photonic quantum computing,and reconfigurable metasurfaces.

Coherent optical frequency transfer via 972-km fiber link

We demonstrate coherent optical frequency dissemination over a distance of 972 km by cascading two spans where the phase noise is passively compensated for.Instead of employing a phase discriminator and a phase locking loop in the conventional active phase control scheme,the passive phase noise cancellation is realized by feeding double-trip beat-note frequency to the driver of the acoustic optical modulator at the local site.This passive scheme exhibits fine robustness and reliability,making it suitable for long-distance and noisy fiber links.An optical regeneration station is used in the link for signal amplification and cascaded transmission.The phase noise cancellation and transfer instability of the 972-km link is investigated,and transfer instability of 1.1×10^(-19)at 10^(4)s is achieved.This work provides a promising method for realizing optical frequency distribution over thousands of kilometers by using fiber links.

Ultrafast dynamics of femtosecond laser-induced high spatial frequency periodic structures on silicon surfaces

Femtosecond laser-induced periodic surface structures(LIPSS)have been extensively studied over the past few decades.In particular,the period and groove width of high-spatial-frequency LIPSS(HSFL)is much smaller than the diffraction limit,making it a useful method for efficient nanomanufacturing.However,compared with the low-spatial-frequency LIPSS(LSFL),the structure size of the HSFL is smaller,and it is more easily submerged.Therefore,the formation mechanism of HSFL is complex and has always been a research hotspot in this field.In this study,regular LSFL with a period of 760 nm was fabricated in advance on a silicon surface with two-beam interference using an 800 nm,50 fs femtosecond laser.The ultrafast dynamics of HSFL formation on the silicon surface of prefabricated LSFL under single femtosecond laser pulse irradiation were observed and analyzed for the first time using collinear pump-probe imaging method.In general,the evolution of the surface structure undergoes five sequential stages:the LSFL begins to split,becomes uniform HSFL,degenerates into an irregular LSFL,undergoes secondary splitting into a weakly uniform HSFL,and evolves into an irregular LSFL or is submerged.The results indicate that the local enhancement of the submerged nanocavity,or the nanoplasma,in the prefabricated LSFL ridge led to the splitting of the LSFL,and the thermodynamic effect drove the homogenization of the splitting LSFL,which evolved into HSFL.

Enhanced anomalous Hall effect in kagome magnet YbMn_(6)Sn_(6)with intermediate-valence ytterbium

We report on the magnetization and anomalous Hall effect(AHE)in the high-quality single crystals of the kagome magnet YbMn_(6)Sn_(6),where the spins of the Mn atoms in the kagome lattice order ferromagnetically and the intermediate-valence Yb atoms are nonmagnetic.The intrinsic mechanism plays a crucial role in the AHE,leading to an enhanced anomalous Hall conductivity(AHC)compared with the other rare-earth RMn_(6)Sn_(6)compounds.Our band structure calculation reveals a strong hybridization between the 4f electrons of Yb and conduction electrons.

Combined Wind-Storage Frequency Modulation Control Strategy Based on Fuzzy Prediction and Dynamic Control

To ensure frequency stability in power systems with high wind penetration,the doubly-fed induction generator(DFIG)is often used with the frequency fast response control(FFRC)to participate in frequency response.However,a certain output power suppression amount(OPSA)is generated during frequency support,resulting in the frequency modulation(FM)capability of DFIG not being fully utilised,and the system’s unbalanced power will be increased during speed recovery,resulting in a second frequency drop(SFD)in the system.Firstly,the frequency response characteristics of the power system with DFIG containing FFRC are analysed.Then,based on the analysis of the generation mechanism of OPSA and SFD,a combined wind-storage FM control strategy is proposed to improve the system’s frequency response characteristics.This strategy reduces the effect of OPSA and improves the FM capability of DFIG by designing the fuzzy logic of the coefficients of FFRC according to the system frequency index in the frequency support stage.During the speed recovery stage,the energy storage(ES)active power reference value is calculated according to the change of DFIG rotor speed,and the ES output power is dynamically adjusted to reduce the SFD.Finally,taking the IEEE 39-bus test system as an example,real-time digital simulation verification was conducted based on the RTLAB OP5707 simulation platform.The simulation results showthat theproposedmethodcan improve theFMcapabilityofDFIG,reduce the SFDunder thepremise of guaranteeing the rapid rotor speed recovery,and avoid the overshooting phenomenon so that the systemfrequency can be quickly restored to a stable state.

Physical activity volume,frequency,and intensity:Associations with hypertension and obesity over 21 years in Australian women

Background:Optimal patterns of accrual of recommended levels of physical activity(PA)for prevention of hypertension and obesity are not known.The overall aim of this study was to investigate whether different patterns of accumulation of PA are differentially associated with hypertension and obesity in Australian women over 21 years.Specifically,we investigated whether,for the same weekly volume of PA,the number of sessions(frequency)and vigorousness of PA(intensity)were associated with a reduction in the occurrence of hypertension and obesity in women.Methods:Data from the 1973-1978 and 1946-1951 cohorts of the Australian Longitudinal Study on Women's Health were analyzed(n=20,588;12%-16%with a Bachelor's or higher degree).Self-reported PA,hypertension,height,and weight were collected using mail surveys every 3 years from 1998/2000 to 2019/2021.Generalized Estimating Equation models with a 3-year lag model were used to investigate the association of PA volume(metabolic equivalent min/week)(none;33-499;500-999;≥1000,weekly frequency(none;1-2 times;3-4times;5-7 times;≥8 times),and the proportion of vigorous PA to total volume of PA(none;0%;1%-33%;34%-66%;67%-100%)with odds of hypertension and obesity from 2000 to 2021.Results:The cumulative incidence of hypertension was 6%in the 1973-1978 and 23%in the 1946-1951 cohort;27%of women in the 1973-1978;and 15%in the 1946-1951 cohort developed obesity over the period.Overall,a higher volume of PA was associated with reduced odds of hypertension and obesity.When the volume of PA was considered,the odds of hypertension did not vary according to the frequency or intensity of PA.However,increased proportion of vigorous PA to the total volume of PA was associated with a small additional reduction in the risk of obe sity.Conclusion:PA volume appears to be more important than the pattern of accumulation for the prevention of hypertension and obesity.Incorporating more sessions,particularly of vigorous-intensity PA,may provide extra benefits for the prevention of obesity.

Steam reforming of acetic acid over Ni/biochar of low metal-loading:Involvement of biochar in tailoring reaction intermediates renders superior catalytic performance

Biochar is a reactive carrier as it may be partially gasified with steam in steam reforming,which could influence the formation of reaction intermediates and modify catalytic behaviors.Herein,the Ni/biochar as well as two comparative catalysts,Ni/Al_(2)O_(3) and Ni/SiO_(2),with low nickel loading(2%(mass))was conducted to probe involvement of the varied carriers in the steam reforming.The results indicated that the Ni/biochar performed excellent catalytic activity than Ni/SiO_(2) and Ni/Al_(2)O_(3),as the biochar carrier facilitated quick conversion of the -OH from dissociation of steam to gasify the oxygen-rich carbonaceous intermediates like C=O and C-O-C,resulting in low coverage while high exposure of nickel species for maintaining the superior catalytic performance.In converse,strong adsorption of aliphatic intermediates over Ni/Al_(2)O_(3) and Ni/SiO_(2) induced serious coking with polymeric coke as the main type(21.5%and 32.1%,respectively),which was significantly higher than that over Ni/biochar(3.9%).The coke over Ni/biochar was mainly aromatic or catalytic type with nanotube morphology and high crystallinity.The high resistivity of Ni/biochar towards coking was due to the balance between formation of coke and gasification of coke and partially biochar with steam,which created developed mesopores in spent Ni/biochar while the coke blocked pores in Ni/Al_(2)O_(3) and Ni/SiO_(2) catalysts.

Enhancing quantum temporal steering via frequency modulation

Various strategies have been proposed to harness and protect space-like quantum correlations in different models under decoherence.However,little attention has been given to temporal-like correlations,such as quantum temporal steering(TS),in this context.In this work,we investigate TS in a frequency-modulated two-level system coupled to a zero-temperature reservoir in both the weak and strong coupling regimes.We analyze the impact of various frequency-modulated parameters on the behavior of TS and non-Markovian.The results demonstrate that appropriate frequency-modulated parameters can enhance the TS of the two-level system,regardless of whether the system is experiencing Markovian or non-Markovian dynamics.Furthermore,a suitable ratio between modulation strength and frequency(i.e.,all zeroes of the 0th Bessel function J_(0)(δ/?))can significantly enhance TS in the strong coupling regime.These findings indicate that efficient and effective manipulation of quantum TS can be achieved through a frequency-modulated approach.