The usage of remote signals obtained from a wide-area measurement system (WAMS) introduces time delays to a wide-area damping controller (WADC), which would degrade system damping and even cause ...system instability. The time-delay margin is defined as the maximum time delay under which a closed-loop system can remain stable. In this paper, the delay margin is introduced as an additional performance index for the synthesis of classical WADCs for flexible ac transmission systems (FACTS) devices to damp inter-area oscillations. The proposed approach includes three parts: a geometric measure approach for selecting feedback remote signals, a residue method for designing phase-compensation parameters, and a Lyapunov stability criterion and linear matrix inequalities (LMI) for calculating the delay margin and determining the gain of the WADC based on a tradeoff between damping performance and delay margin. Three case studies are undertaken based on a four-machine two-area power system for demonstrating the design principle of the proposed approach, a New England ten-machine 39-bus power system and a 16-machine 68-bus power system for verifying the feasibility on larger and more complex power systems. The simulation results verify the effectiveness of the proposed approach on providing a balance between the delay margin and the damping performance.
High-mobility semiconducting ultrathin films form the basis of modern electronics, and may lead to the scalable fabrication of highly performing devices. Because the ultrathin limit cannot be reached ...for traditional semiconductors, identifying new two-dimensional materials with both high carrier mobility and a large electronic bandgap is a pivotal goal of fundamental research. However, air-stable ultrathin semiconducting materials with superior performances remain elusive at present. Here, we report ultrathin films of non-encapsulated layered Bi2 O2 Se, grown by chemical vapour deposition, which demonstrate excellent air stability and high-mobility semiconducting behaviour. We observe bandgap values of ∼0.8 eV, which are strongly dependent on the film thickness due to quantum-confinement effects. An ultrahigh Hall mobility value of >20,000 cm2 V-1 s-1 is measured in as-grown Bi2 O2 Se nanoflakes at low temperatures. This value is comparable to what is observed in graphene grown by chemical vapour deposition and at the LaAlO3 -SrTiO3 interface, making the detection of Shubnikov-de Haas quantum oscillations possible. Top-gated field-effect transistors based on Bi2 O2 Se crystals down to the bilayer limit exhibit high Hall mobility values (up to 450 cm2 V-1 s-1 ), large current on/off ratios (>106 ) and near-ideal subthreshold swing values (∼65 mV dec-1 ) at room temperature. Our results make Bi2 O2 Se a promising candidate for future high-speed and low-power electronic applications.
Despite much recent effort, the highest reported T c of the infinite-layer nickelates remains lower than 15 K. Here, the authors apply pressure to Pr0.82Sr0.18NiO2 thin films and observe a monotonic ...increase of T c to 31 K at 12.1 GPa, an increase that does not level off with increasing pressure.
Highlights • Aβ-AGE aggravated Aβ-induced cognitive deficit in rats. • Aβ-AGE intensified Aβ-induced upregulation of RAGE in rats. • Aβ-AGE amplified Aβ-induced activation of GSK3, NF-κB, and p38 in ...rats. • Aβ-AGE exacerbated Aβ-induced cognitive impairment through the RAGE pathway in rats.
The CDEX-1 experiment conducted a search of low-mass (< 10GeV/c super(2)) weakly interacting massive particles dark matter at the China Jinping Underground Laboratory using a p-type point-contact ...germanium detector with a fiducial mass of 915 g at a physics analysis threshold of 475 eVee. We report the hardware setup, detector characterization, data acquisition, and analysis procedures of this experiment. No excess of unidentified events is observed after the subtraction of the known background. Using 335.6 kg-days of data, exclusion constraints on the weakly interacting massive particle-nucleon spin-independent and spin-dependent couplings are derived.
To explore the clinical characteristics and prognosis of the new coronavirus 2019-nCoV patients combined with cardiovascular disease （CVD).
A retrospective analysis was performed on 112 COVID-19 ...patients with CVD admitted to the western district of Union Hospital in Wuhan, from January 20, 2020 to February 15, 2020. They were divided into critical group (ICU,
=16) and general group (
=96) according to the severity of the disease and patients were followed up to the clinical endpoint. The observation indicators included total blood count, C-reactive protein (CRP), arterial blood gas analysis, myocardial injury markers, coagulation function, liver and kidney function, electrolyte, procalcitonin (PCT), B-type natriuretic peptide (BNP), blood lipid, pulmonary CT and pathogen detection.
Compared with the general group, the lymphocyte count (0.74 (0.34, 0.94)×10
/L vs. 0.99 (0.71, 1.29)×10
/L,
=0.03) was extremely lower in the critical group, CRP (106.98 (81.57, 135.76) mg/L vs. 34.34 (9.55,76.54) mg/L,
<0.001) and PCT (0.20 (0.15,0.48) μg/L vs. 0.11 (0.06,0.20) μg/L,
<0.001) were significantly higher in the critical group. The BMI of the critical group was significantly higher than that of the general group (25.5 (23.0, 27.5) kg/m
vs. 22.0 (20.0, 24.0) kg/m
，
=0.003). Patients were further divided into non-survivor group (17, 15.18%) group and survivor group (95, 84.82%). Among the non-survivors, there were 88.24% (15/17) patients with BMI> 25.0 kg/m
, which was significantly higher than that of survivors (18.95% (18/95),
<0.001). Compared with the survived patients, oxygenation index (130 (102, 415) vs. 434 (410, 444),
<0.001) was significantly lower and lactic acid (1.70 (1.30, 3.00) mmol/L vs. 1.20 (1.10, 1.60) mmol/L,
<0.001) was significantly higher in the non-survivors. There was no significant difference in the proportion of ACEI/ARB medication between the critical group and the general group or between non-survivors and survivors （all
>0.05).
COVID-19 patients combined with CVD are associated with a higher risk of mortality. Critical patients are characterized with lower lymphocyte counts. Higher BMI are more often seen in critical patients and non-survivor. ACEI/ARB use does not affect the morbidity and mortality of COVID-19 combined with CVD. Aggravating causes of death include fulminant inflammation, lactic acid accumulation and thrombotic events.
Previous studies have reported that high carbon contents in FeCoCrNiMn high-entropy alloys lead to carbides precipitating from the alloys. Typically, carbides are used to improve the strength of ...alloys but also lead to decreased ductility. However, the strength and ductility of alloys can be improved when carbides shape, size and distribution are carefully controlled. Therefore, a carbide-containing FeCoCrNiMn alloy with 2 at.-% carbon was prepared by arc melting, and its microstructure and mechanical properties were further tuned by cold rolling with subsequent annealing treatment. The yield strength and uniform elongation of the resultant alloy were excellent, reaching 581 MPa and 25%, respectively, due to the additive combination of various strengthening mechanisms, such as solid-solution hardening, grain-boundary hardening and precipitation hardening.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A nasopharyngeal carcinoma (NPC) mass screening trial using a combination of immunoglobulin A antibodies to Epstein-Barr virus capsid antigen and nuclear antigen-1 by enzyme-linked immunosorbent ...assay in addition to indirect mirror examination in the nasopharynx and/or lymphatic palpation (IMLP) was conducted in southern China. Cantonese aged 30-59 years residing in 2 cities randomly selected by cluster sampling, Sihui and Zhongshan, were invited to participate in this screening from May 2008 through May 2010. Participants were offered fiberoptic endoscopy examination and/or pathologic biopsy if their serologic tests reached our predefined level of high risk or if results from the physical examination indicated possible cancer (i.e., were IMLP positive). A total of 28,688 individuals were voluntarily screened in the initial round. The overall NPC detection rate was 0.14% (41/28,688) with an early diagnosis rate of 68.3% (28/41) during the first year of follow-up. Thirty-eight of 41 cases (92.7%) were detected among the high-risk group, and 7 of 41 cases (17.1%) were detected among the IMLP-positive group. The 2 Epstein-Barr virus serologic tests by enzyme-linked immunosorbent assay could be a feasible alternative for NPC screening in endemic areas. Further follow-up is needed to examine whether screening has an effect on decreasing mortality from NPC in these areas.
Abstract Sun-as-a-star spectroscopic characteristics of solar flares can be used as a benchmark for the detection and analysis of stellar flares. Here, we study the Sun-as-a-star properties of an ...X1.0 solar flare, using high-resolution spectroscopic data obtained by the Chinese H α Solar Explorer (CHASE). A noise reduction algorithm based on discrete Fourier transformation is first employed to enhance the signal-to-noise ratio of the space-integral H α spectrum, with a focus on its typical characteristics. For the flare of interest, we find that the average H α profile displays a strong emission at the line center and an obvious line broadening. It also presents a clear red asymmetry, corresponding to a redshift velocity of around 50 km s −1 that slightly decreases with time, consistent with previous results. Furthermore, we study how the size of the space-integral region affects the characteristics of the flare's Sun-as-a-star H α profile. It is found that although the redshift velocity calculated from the H α profile remains unchanged, the detectability of the characteristics weakens as the space-integral region becomes larger. An upper limit on the size of the target region where the red asymmetry is detectable is estimated. It is also found that the intensity in H α profiles, measured by the equivalent widths of the spectra, are significantly underestimated if the H α spectra are further averaged in the time domain.
This paper investigates the delay-dependent stability of a power system equipped with a wide-area damping controller (WADC) using a new method which consists of a delay-dependent criterion based on ...Lyapunov theory and model reduction technique. The delay margin, the maximal delay which allows the closed-loop power system to retain stable, is calculated based on the reduced order model and linear matrix inequality (LMI) technique. Both constant and time-varying delays introduced by the transmission of the remote signals are investigated. Cases studies are carried out based on a two-area four-machine power system controlled by a conventional lead-lag WADC and a robust WADC. The relationship between the parameters of WADC and the delay margin has been investigated and is used to guide the design of WADC and achieve a trade-off between the damping performance and delay margin. The effectiveness of the proposed method is verified by simulation studies.
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