265 research outputs found
Parametric study of unsteady-flow-induced volute casing vibro-acoustics in a centrifugal fan
A numerical parametric analysis of a vibro-acoustic coupling method that considered the influence of vibro-acoustic coupling was carried out to investigate the casing vibrations and feathers of vibrational noise induced by unsteady flow of the centrifugal fan at the best-efficiency point (BEP). There are three important aspects of this method. First, an unsteady flow-field with a whole impeller-volute configuration was solved based on three-dimensional incompressible Navier-Stokes equations and a standard k-ε turbulence mode to obtain the source of the vibro-acoustics. Second, a one-way-flow structural acoustic coupling method was implemented to study the volute vibrations and behaviors of vibrational noise by adoption. The generation mechanism of vibrational noise of the volute casing was revealed. Third, the parametric analysis method was used to explore the parametric relationship between the panel thicknesses (such as front-panel thickness [FT], side-panel thickness [ST], and back-panel thickness [BT]) and the outlet acoustical power of the volute casing surface. The parametric analysis provides a reasonable range of values of three panel thicknesses that result in minimal vibrational sound radiation
Realising the decomposition of a multi‐frequency signal under the coloured noise background by the adaptive stochastic resonance in the non‐linear system with periodic potential
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163832/1/sil2bf00663.pd
Beauty of Cryptography: the Cryptographic Sequences and the Golden Ratio
In this paper, the authors construct a new type of cryptographic sequence which is named an extra-super increasing sequence, and give the definitions of the minimal super increasing sequence {a[1], a[2], ..., a[n]} and minimal extra-super increasing sequence {z[1], z[2], ..., z[n]}. Prove that the minimal extra-super increasing sequence is the odd-positioned subsequence of the Fibonacci sequence, namely {z[1], z[2], ..., z[n], ...} = {F[1], F[3], ..., F[2n-1], ...}, which indicates that the approach to the golden ratio phi through the term difference ratio (z[n+1] - z[n]) / z[n] is more smooth and expeditious than through the term ratio (F[n+1] / F[n]). Further prove that the limit of the term ratio difference between the two cryptographic sequences equals the golden ratio conjugate PHI, namely lim (n to infinity) (z[n+1] / z[n] - a[n+1] / a[n]) = PHI, which reveals the beauty of cryptography
Learning to Behave Like Clean Speech: Dual-Branch Knowledge Distillation for Noise-Robust Fake Audio Detection
Most research in fake audio detection (FAD) focuses on improving performance
on standard noise-free datasets. However, in actual situations, there is
usually noise interference, which will cause significant performance
degradation in FAD systems. To improve the noise robustness, we propose a
dual-branch knowledge distillation fake audio detection (DKDFAD) method.
Specifically, a parallel data flow of the clean teacher branch and the noisy
student branch is designed, and interactive fusion and response-based
teacher-student paradigms are proposed to guide the training of noisy data from
the data distribution and decision-making perspectives. In the noise branch,
speech enhancement is first introduced for denoising, which reduces the
interference of strong noise. The proposed interactive fusion combines
denoising features and noise features to reduce the impact of speech distortion
and seek consistency with the data distribution of clean branch. The
teacher-student paradigm maps the student's decision space to the teacher's
decision space, making noisy speech behave as clean. In addition, a joint
training method is used to optimize the two branches to achieve global
optimality. Experimental results based on multiple datasets show that the
proposed method performs well in noisy environments and maintains performance
in cross-dataset experiments
Risk factors predicting a higher grade of subarachnoid haemorrhage in small ruptured intracranial aneurysm (< 5 mm)
Aim. To identify the risk factors for clinical and radiographic grades of subarachnoid haemorrhage (SAH) in small (< 5 mm) intracranial aneurysms (SIAs).
Material and methods. We retrospectively analysed patients with SIAs treated in our centre between February 2009 and June 2018. The clinical status was graded using the Hunt and Hess (H&H) score and the radiological severity of SAH was graded by Fisher grades (FG). The risk factors were determined using multivariate logistic regression analysis.
Results. A total of 160 patients with ruptured SIAs (< 5 mm) were included. In univariate analysis, smoking (P = 0.007), alcohol use (P = 0.048), aspirin use (P = 0.001), and higher size ratio (SR) (P = 0.001) were significantly associated with a higher H&H grade (3–5) in SIAs; and smoking (P = 0.019), aspirin use (P = 0.031), inflow angle < 90 degrees (P = 0.011), and aneurysm size (P = 0.039) were significantly associated with a higher FG score (3–4). In the adjusted multivariate analysis, previous SAH (OR, 12.245, 95% CI, 2.261–66.334, P = 0.004), aspirin use (OR, 4.677, 95% CI, 1.392–15.718, P = 0.013), alcohol use (OR, 3.392, 95% CI, 1.146–10.045, P = 0.027), inflow angle < 90 (OR, 3.881, 95% CI, 1.273–11.831, P = 0.017), and higher SR (OR, 6.611, 95% CI, 2.235–19.560, P = 0.001) were independent risk factors for a higher H&H grade in ruptured SIAs; smoking (OR, 2.157, 95% CI, 1.061–4.384, P = 0.034), and inflow angle < 90 degrees (OR, 2.603, 95% CI, 1.324–5.115, P = 0.006) were independent risk factors for a higher FG (3–4).
Conclusions. This study revealed that inflow angle < 90 degrees and size ratio, but not absolute size, may highly predict poorer grade of SAH in SRA. Aspirin use, previous SAH, and alcohol use were significantly associated with a higher H&H grade in ruptured SIAs, and smoking was a significant predictor of poorer FG
DGSD: Dynamical Graph Self-Distillation for EEG-Based Auditory Spatial Attention Detection
Auditory Attention Detection (AAD) aims to detect target speaker from brain
signals in a multi-speaker environment. Although EEG-based AAD methods have
shown promising results in recent years, current approaches primarily rely on
traditional convolutional neural network designed for processing Euclidean data
like images. This makes it challenging to handle EEG signals, which possess
non-Euclidean characteristics. In order to address this problem, this paper
proposes a dynamical graph self-distillation (DGSD) approach for AAD, which
does not require speech stimuli as input. Specifically, to effectively
represent the non-Euclidean properties of EEG signals, dynamical graph
convolutional networks are applied to represent the graph structure of EEG
signals, which can also extract crucial features related to auditory spatial
attention in EEG signals. In addition, to further improve AAD detection
performance, self-distillation, consisting of feature distillation and
hierarchical distillation strategies at each layer, is integrated. These
strategies leverage features and classification results from the deepest
network layers to guide the learning of shallow layers. Our experiments are
conducted on two publicly available datasets, KUL and DTU. Under a 1-second
time window, we achieve results of 90.0\% and 79.6\% accuracy on KUL and DTU,
respectively. We compare our DGSD method with competitive baselines, and the
experimental results indicate that the detection performance of our proposed
DGSD method is not only superior to the best reproducible baseline but also
significantly reduces the number of trainable parameters by approximately 100
times
Audio Deepfake Detection Based on a Combination of F0 Information and Real Plus Imaginary Spectrogram Features
Recently, pioneer research works have proposed a large number of acoustic
features (log power spectrogram, linear frequency cepstral coefficients,
constant Q cepstral coefficients, etc.) for audio deepfake detection, obtaining
good performance, and showing that different subbands have different
contributions to audio deepfake detection. However, this lacks an explanation
of the specific information in the subband, and these features also lose
information such as phase. Inspired by the mechanism of synthetic speech, the
fundamental frequency (F0) information is used to improve the quality of
synthetic speech, while the F0 of synthetic speech is still too average, which
differs significantly from that of real speech. It is expected that F0 can be
used as important information to discriminate between bonafide and fake speech,
while this information cannot be used directly due to the irregular
distribution of F0. Insteadly, the frequency band containing most of F0 is
selected as the input feature. Meanwhile, to make full use of the phase and
full-band information, we also propose to use real and imaginary spectrogram
features as complementary input features and model the disjoint subbands
separately. Finally, the results of F0, real and imaginary spectrogram features
are fused. Experimental results on the ASVspoof 2019 LA dataset show that our
proposed system is very effective for the audio deepfake detection task,
achieving an equivalent error rate (EER) of 0.43%, which surpasses almost all
systems
Oxidative balance score reflects vascular endothelial function of Chinese community dwellers
Background: The oxidative balance score (OBS) is a composite estimate of the overall pro- and antioxidant risk status in an individual. The aim of this study is to explore the association between the OBS and vascular endothelial function in Chinese community dwellers.Methods: In total, 339 community dwelling adults (aged 20–75 years) were recruited in this study. The overall OBS was calculated on the basis of 16 pro- and antioxidant factors related to diet (measured by fasting blood samples) and lifestyle (evaluated by questionnaires). The dietary OBS and lifestyle OBS were calculated on the basis of the corresponding components. Serum iso-prostaglandin F2α (FIP) was measured to evaluate the oxidative stress degree, and brachial artery blood flow-mediated dilation (FMD) was measured for vascular endothelial function. The FIP and FMD levels were dichotomized as “low” or “high” using the corresponding median values (low FIP, n = 159; high FIP, n = 180; low FMD, n = 192; and high FMD, n = 147). The components of the OBS were compared between the stratified FIP and FMD groups. Logistic regression was used to analyze the OBS associations with FIP and FMD.Results: The higher overall OBS and dietary OBS were associated with lower FIP (p < 0.001), whereas the higher overall OBS (p < 0.01) and dietary OBS (p < 0.05) were associated with higher FMD. The lifestyle OBS was not associated with FIP and FMD (p > 0.05). Except for the body mass index (BMI) and low physical activity, all other OBS components were significantly different between the low FIP and high FIP groups (p < 0.05). Four diet-related antioxidants (α-carotene, zeaxanthin, α-tocopherol, and γ-tocopherol) showed significant differences between the high and low FMD groups (p < 0.05).Conclusion: The decreasing OBS level was associated with low endothelial function and high oxidative stress. The dietary OBS, rather than the lifestyle OBS, was more closely associated with endothelial function
Bioassay-guided isolation of three new alkaloids from Suillus bovinus and preliminary mechanism against ginseng root rot
In order to control the occurrence of ginseng root rot caused by Fusarium solani (Mart.) Sacc., the antifungal compounds of the mushroom Suillus bovinus were investigated. And three new alkaloids (1–3), named bovinalkaloid A–C, along with one known analog (4), were isolated and identified by bioassay-guided isolation and spectroscopic analyses. Compound 1 strongly inhibited the mycelial growth and spore germination of F. solani with minimum inhibitory concentration of 2.08 mM. Increases in electrical conductivity, nucleic acid, and protein contents, and decreases in lipid content showed that the membrane permeability and integrity were damaged by compound 1. Compound 1 also increased the contents of malondialdehyde and hydrogen peroxide and the activities of antioxidant enzymes, indicating that lipid peroxidation had taken place in F. solani. Compound 1 may serve as a natural alternative to synthetic fungicides for the control of ginseng root rot
Population pharmacokinetics of intravenous daptomycin in critically ill patients: implications for selection of dosage regimens
Daptomycin is gaining prominence for the treatment of methicillin-resistant Staphylococcus aureus infections. However, the dosage selection for daptomycin in critically ill patients remains uncertain, especially in Chinese patients. This study aimed to establish the population pharmacokinetics of daptomycin in critically ill patients, optimize clinical administration plans, and recommend appropriate dosage for critically ill patients in China. The study included 64 critically ill patients. Blood samples were collected at the designated times. The blood daptomycin concentration was determined using validated liquid chromatography-tandem mass spectrometry. A nonlinear mixed-effects model was applied for the population pharmacokinetic analysis and Monte Carlo simulations of daptomycin. The results showed a two-compartment population pharmacokinetic model of daptomycin in critically ill adult Han Chinese patients. Monte Carlo simulations revealed that a daily dose of 400 mg of daptomycin was insufficient for the majority of critically ill adult patients to achieve the anti-infective target. For critically ill adult patients with normal renal function (creatinine clearance rate >90 mL/min), the probability of achieving the target only reached 90% when the daily dose was increased to 700 mg. For patients undergoing continuous renal replacement therapy (CRRT), 24 h administration of 500 mg met the pharmacodynamic goals and did not exceed the safety threshold in most patients. Therefore, considering its efficacy and safety, intravenous daptomycin doses are best scaled according to creatinine clearance, and an increased dose is recommended for critically ill patients with hyperrenalism. For patients receiving CRRT, medication is recommended at 24 h intervals
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