13,155 research outputs found
Forced Oscillation Source Location via Multivariate Time Series Classification
Precisely locating low-frequency oscillation sources is the prerequisite of
suppressing sustained oscillation, which is an essential guarantee for the
secure and stable operation of power grids. Using synchrophasor measurements, a
machine learning method is proposed to locate the source of forced oscillation
in power systems. Rotor angle and active power of each power plant are utilized
to construct multivariate time series (MTS). Applying Mahalanobis distance
metric and dynamic time warping, the distance between MTS with different phases
or lengths can be appropriately measured. The obtained distance metric,
representing characteristics during the transient phase of forced oscillation
under different disturbance sources, is used for offline classifier training
and online matching to locate the disturbance source. Simulation results using
the four-machine two-area system and IEEE 39-bus system indicate that the
proposed location method can identify the power system forced oscillation
source online with high accuracy.Comment: 5 pages, 3 figures. Accepted by 2018 IEEE/PES Transmission and
Distribution Conferenc
Fe(BF4)2 catalyzed inter- and intramolecular carbonyl-ene reaction of trifluoropyruvate
Inter- and intramolecular carbonyl-ene reactions have been developed using 5 mol% Fe(BF4)2 as catalyst, affording homoallylic alcohols in 36β87% isolated yields. This catalyst, prepared from FeCl2 and AgBF4, is the first FeII Lewis acid reported for the carbonyl-ene reaction using ethyl trifluoropyruvate. The method was successfully applied to the reaction of various 1,1-disubstituted alkenes with ethyl trifluoropyruvate and to the cyclization of citronellal
Convergence of wavelet thresholding estimators of differential operators
AbstractWavelet shrinkage is a strategy to obtain a nonlinear approximation to a given signal. The shrinkage method is applied in different areas, including data compression, signal processing and statistics. The almost everywhere convergence of resulting wavelet series has been established in [T. Tao, On the almost everywhere convergence of wavelet summation methods, Appl. Comput. Harmon. Anal. 3 (1996) 384β387] and [T. Tao, B. Vidakovic, Almost everywhere behavior of general wavelet shrinkage operators, Appl. Comput. Harmon. Anal. 9 (2000) 72β82]. With a representation of fβ² in terms of wavelet coefficients of f, we are interested in considering the influence of wavelet thresholding to f on its derivative fβ². In this paper, for the representation of differential operators in nonstandard form, we establish the almost everywhere convergence of estimators as threshold tends to zero
Binary population synthesis study on supersoft X-ray phase of single degenerate type Ia supernova progenitors
In the single degenerate (SD) scenario for type Ia supernovae (SNe Ia), a
mass-accreting white dwarf is expected to experience a supersoft X-ray source
(SSS) phase. However, some recent observations showed that the expected number
of the mass-accreting WD is much lower than that predicted from theory,
whatever in spiral or elliptical galaxies. In this paper, we did a binary
population synthesis study on the relative duration of the SSS phase to their
whole mass-increasing phase of WDs leading to SNe Ia. We found that for about
40% progenitor systems, the relative duration is shorter than 2% and the
evolution of the mean relative duration shows that it is always smaller than
5%, whatever for young or old SNe Ia. In addition, before SNe Ia explosion,
more than 55% progenitor systems are experiencing a dwarf novae phase, and only
no more than 10% is staying SSS phase. These results are consistent with the
recent observations, and imply that both in early- and late-type galaxies, only
a small fraction of mass-accreting WD resulting in SNe Ia contribute to the
supersoft X-ray flux. So, although our results are not directly related to the
X-ray output of SN Ia progenitor, the low supersoft X-ray luminosity observed
in early type galaxies may have no ability to exclude the validity of SD model.
On the contrary, it is evidence to support the SD scenario.Comment: 9 pages, 5 figures, accepted for publication in RA
Role of ASH1L in Prostate Cancer Metastasis
https://openworks.mdanderson.org/sumexp22/1021/thumbnail.jp
Tolerability and effectiveness of (S)-amlodipine compared with racemic amlodipine in hypertension: A systematic review and meta-analysis
AbstractBackground: Amlodipine is a calcium channel blocker prescribed for the management of angina and hypertension. As a racemic mixture, amlodipine contains (R)- and (S)-amlodipine isomers, but only (S)-amlodipine as the active moiety possesses therapeutic activity. Based on pharmacologic research, it remains uncertain if (S)-amlodipine alone has similar efficacy and fewer associated adverse events (AEs) compared with the racemic mixtures.Objective: The aim of this systematic review and meta-analysis was to determine the effectiveness and tolerability of (S)-amlodipine compared with that of racemic amlodipine.Methods: A systematic literature search was performed using MEDLINE (1966β2009), EMBASE (1966β2009), the Cochrane Central Register of Controlled Trials (issue 3, 2009), the Chinese Biomedical Database (1978β2009), and the China National Knowledge Internet (1980β2009). All randomized controlled trials (RCTs) comparing (S)-amlodipine 2.5 mg and racemic amlodipine 5.0 mg in the treatment of hypertension were included in the review. The outcome measures to be collected were cardiovascular events, systolic blood pressure (SBP), diastolic BP (DBP), and AEs. Quality assessments of clinical trials were conducted using a modified Jadad Scale, with trials being rated as low quality (score 0β3) or high quality (score 4β7). Meta-analysis of the included studies was performed using RevMan software.Results: Of the 229 references identified, 214 were excluded after screening the titles, abstracts, or full texts. Fifteen RCTs were included, of which 13 were in Chinese and 2 in English. Based on the Jadad Scale score, 3 of the RCTs were classified as high quality (score 5 or 6) and the remaining 12 as low quality (score 1β3). None of the trials evaluated cardiovascular events beyond 40 weeks. Meta-analysis of the 15 trials indicated that (S)-amlodipine was not significantly different from racemic amlodipine in the effect on BP. When only high-quality studies were included, after 4 weeks' treatment, the weighted mean difference (WMD) of SBP and DBP decrease (1 study) was β2.84 (95% CI, β6.42 to 0.74) with (S)-amlodipine and β1.71 (95% CI, β3.48 to 0.06) with racemic amlodipine. After 8 weeks' treatment, the WMD of SBP and DBP decrease (2 studies) was β1.13 (95% CI, β5.29 to 3.03) and β1.34 (95% CI, β2.67 to β0.01), respectively. The risk difference (RD) for the number of patients who experienced AEs with (S)-amlodipine and racemic amlodipine was found to be β0.04 (95% CI, β0.06 to β0.02). When all the trials were included, (S)-amlodipine treatment was associated with significantly less edema than racemic amlodipine (RD, β0.02; 95% CI, β0.03 to 0.00); however, when only high-quality studies (2 studies) were included, no difference was found between the 2 groups (RD, 0.01; 95% CI, β0.02 to 0.03). One high-quality study found significant differences in increases in aspartate and alanine aminotransferase activities in the 2 groups (RD, 0.08; 95% CI, 0.01 to 0.05). No significant differences between the 2 groups were found in the incidence of headache (RD, 0.00; 95% CI, β0.02 to 0.01) or flushing (RD, β0.01; 95% CI, β0.02 to 0.00).Conclusions: The majority of the clinical trials comparing (S)-amlodipine and racemic amlodipine treatment were low quality (12/15 [80%]). According to the limited evidence, there were no significant differences between (S)-amlodipine 2.5 mg and racemic amlodipine 5.0 mg in controlling BP. When all the trials were considered, (S)-amlodipine treatment was associated with significantly less edema than racemic amlodipine; however, when only high-quality trials were included, no significant difference was found. More long-term, high-quality RCTs with cardiovascular events as the primary outcome are needed to compare the safety and efficacy of (S)-amlodipine and racemic amlodipine
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