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Single-photon emitters based on intrinsic defects in silicon carbide (SiC) are promising as solid-state qubits for the quantum information storage, whereas defect engineering in a controllable manner still remains challenging. Herein, the thermally-driven defect dynamic reaction in the ion implanted 4H-SiC has been exploited through the optical emission spectra of defects. For the heavy-ion (Si or Ar) implanted samples with abundant Frenkel pairs, the silicon vacancies (VSi) are energetically converted into the carbon antisite-vacancy pair (CSi-VC) upon annealing till 1300 °C for 30 min, accompanied with the gradual lattice recovery and local strain relaxation. The further temperature elevation dissociates the metastable CSi-VC into carbon antisite (CSi) and carbon vacancy (VC), as supported by the consequent quenching of the (CSi-VC)-related emission at 700 nm. Thus, the whole defect reaction is probed as the vacancy interconversion from VSi to VC with the byproduct of stacking faults. In contrast, the intermediate CSi-VC complexes are not energetically favorable during the annealing of the H-implanted sample, which results from the negligible generation of Frenkel pairs, as supported by the x-ray diffraction patterns and Raman scattering analysis. These findings provide guidance for defect engineering in SiC toward the creation of reliable single photon emitters.

The authors demonstrate a Bull’s eye cavity design that is composed of circular Bragg gratings and micropillar optical cavity in 4H silicon carbide (4H-SiC) for single photon emission. Numerical calculations are used to investigate and optimize the emission rate and directionality of emission. Thanks to the optical mode resonances and Bragg reflections, the radiative decay rates of a dipole embedded in the cavity center is enhanced by 12.8 times as compared to that from a bulk 4H-SiC. In particular, a convergent angular distribution of the emission in far field is simultaneously achieved, which remarkably boost the collection efficiency. The findings of this work provide an alternative architecture to manipulate light–matter interactions for achieving high-efficient SiC single photon sources towards applications in quantum information technologies.

There has been a high rate of false alarms for the critical electrocardiogram (ECG) arrhythmia events in intensive care units (ICUs), from which the 'crying-wolf' syndrome may be resulted and patient safety may be jeopardized. This article presents an algorithm to reduce false critical arrhythmia alarms using arterial blood pressure (ABP) and/or photoplethysmogram (PPG) waveform features. We established long duration reference alarm datasets which consist of 573 ICU waveform-alarm records (283 for development set and 290 for test set) with total length of 551 patent days. Each record has continuous recordings of ECGs, ABP and/or PPG signals and contains one or multiple critical ECG alarms. The average length of a record is 23 h. There are totally 2408 critical ECG alarms (1414 in the development set and 994 in the test set), each of which was manually annotated by experts. The algorithm extracts ABP/PPG pulse features on a beat-by-beat basis. For each pulse, five event feature indicators (EFIs), which correspond to the five critical ECG alarms, are generated. At the time of a critical ECG alarm, the corresponding EFI values of those ABP/PPG pulses around the alarm time are checked for adjudicating (accept/reject) this alarm. The algorithm retains all (100%) the true alarms and significantly reduces the false alarms. Our results suggest that the algorithm is effective and practical on account of its real-time dynamic processing mechanism and computational efficiency.

We investigate theoretically single photon transport properties in coupled-resonator waveguide coupling with a nanocavity interacting with an external mirror. By using the discrete coordinates approach, transmission and reflection amplitudes of the propagating single photon in the waveguide are obtained. The influence of the coupling strength between the nanocavity and the external mirror on the single photon scattering spectra is discussed. We also extend the results to the waveguide with linear and quadratic form dispersion relations.

In this paper, dielectric columns with different dielectric constants are employed as dielectric materials in the packed bed reactor to investigate the dynamic behaviors of plasma interaction processes. The effects of the dielectric constants (zirconia: e=25 and PTFE: e=2.5) on the production of reactive species are studied for plasma catalysis applications. Comparison studies of discharge images, electrical characteristics, discharge dynamic evolution and spatial- temporal resolved optical emission spectroscopy are carried on when zirconia and PTFE columns are employed. The results show that there are four discharge processes existing in the packed bed reactor: surface streamer on the dielectric column, local discharge at the contact point, surface discharge on the grounded dielectric plate, and the volume discharge. The production of reactive species such as N2 (C3Пu), N2 + (B2Σu +) and O (3p 5P) depend on the discharge processes to a great extent. The production of the N2 + (B2Σu +) always accompanies the formation of the streamer by electrons direct impact process to excite the ground state nitrogen molecules to N2 + (B2Σu +). And the O(3p 5P) is generated in two different ways, which plays major role during the voltage pulse raising and falling time, respectively. The first way is the direct and fast one-step ionization and excitation by high energy electrons with O2. The second way is the energy transfer from the nitrogen metastable N2(A3Σu +) and the energetic electrons, in which way the O is first ionized from O2 and then be excited to O(3p 5P).Furthermore, compared with zirconia column, PTFE column is more conductive to the generation of reactive species.

The second harmonic braking protection is the key to the differential excitation inrush current of the transformer and the quick action of the differential protection. In this paper, it is verified that the large-scale inverter type power supply may affect the second harmonic braking protection of the transformer. The mechanism of generating the second harmonic component of the current during the short-circuit fault of the inverter-type power supply is analyzed. Further analysis of the secondary harmonic current generated by the inverter-type power supply during the fault in the transformer zone may cause the second harmonic braking component of the transformer. Finally, the correctness of the analysis is verified based on the PSCAD/EMTDC transient electromagnetic simulation software.

The mechanisms of photoinduced charge transfer in composites of TiO2 nanorods with a conjugated polymer (poly(2-methoxy-5-(2'-ethyl)(hexyloxy) 1,4-phenylenevinylene) (MEH-PPV) have been investigated by steady-state, time-resolved photoluminescence (PL) spectroscopy and photoluminescence excitation (PLE) spectroscopy. Efficient charge separation takes place at the TiO2-nanorod/polymer interfaces when the polymer is excited, leading to quenching of the photoluminescence efficiency η and shortening of the measured lifetime τPL. In addition, the low-temperature absorption and photoluminescence spectra show that the inclusion of TiO2 nanorods in polymer can reduce disorder in conformation and enhance conjugation in the polymer chain. A photovoltaic solar cell device based on the MEH-PPV/TiO2-nanorod composite material is also presented, which shows a two order increase in short-circuit current JSC compared to that based on the pristine MEH-PPV.