Scattering strength at active volcanoes in Japan as inferred from the peak ratio analysis of teleseismic P waves

Small-scale seismic velocity heterogeneity has been studied through the calculation of peak amplitude ratio as a means to quantify the strength of seismic wave scattering at volcanoes in Japan. This ratio is defined as the ratio of the maximum (peak) P wave energy in the transverse component seismogram envelope over that of the three-component sum seismogram envelope (transverse + radial + vertical). According to the previous study using Japan’s Hi-net seismometer network, the peak ratio is observed to be larger near the (active) quaternary volcanoes. However, these Hi-net stations are not positioned on the volcanoes themselves. This study systematically examines the peak ratios at 47 active volcanoes across Japan, using seismometers operated by the Japan Meteorological Agency (JMA). Analyses were performed at four frequency bands: 0.5–1, 1–2, 2–4, and 4–8 Hz. We found that the JMA stations yield higher peak ratios than the Hi-net stations. Their differences are statistically significant at the 99.9% confidence level in all frequency bands. We also examined the differences between the ground surface and borehole stations of the JMA network. The former shows larger peak ratios, and for most frequency bands, the differences are also statistically significant at the 99.9% confidence level. This suggests an intensification of small-scale medium heterogeneities especially at shallow depths at active volcanoes, and that scattering might have been enhanced at the very shallow parts. Graphical Abstract

Thrombin Generation to Predict the Risk of Venous Thromboembolism Recurrence, Major Bleeding and Death in the Elderly: A Prospective Multicenter Cohort Study

Introduction: Venous thromboembolism (VTE), comprising deep vein thrombosis (DVT) and pulmonary embolism (PE), constitutes a worldwide major health issue, and a leading cause of death. VTE incidence increases exponentially with age mainly due to the accumulation of risk factors and comorbidities predisposing to thrombosis. This leads to greater morbidity impact of VTE on elderly patients, who are also at higher risk of bleeding. Consequently, identification of older patients who might benefit from indefinite anticoagulation treatment is paramount. In order to facilitate the identification of these patients, the benefit/risk ratio should be carefully evaluated by considering clinical and laboratory information. Thrombin activity can be recorded by continuously measuring cleavage of a fluorescent substrate, resulting in a thrombin generation (TG) curve. Recent association studies show promising data of thrombin generation parameters predicting first VTE in elderly (Wang H et. al. RPTH 2021, 5:e12536). However, the predictive ability of thrombin generation for recurrent VTE, major bleeding and mortality in the elderly is unknown. The goal of this study was to prospectively investigate the performance of the TG assay one year after index VTE in predicting the risk of VTE, recurrence, major bleeding and mortality up to 2 years in elderly population. Methods: The study was conducted as part of the Swiss Cohort of Elderly Patients with VTE (SWITCO65+), a prospective multicenter cohort study to assess medical outcomes and quality of life in elderly patients with acute VTE in Switzerland. For the present study, the clinical outcomes were VTE recurrence, major bleeding and mortality, which were assessed parallel to clinical data of thrombosis and other general laboratory parameters including thrombophilia testing in over a 3-year period. Blood samples for assessment of TG parameters were drawn 12 month after the index VTE. Venous blood was drawn after minimal venostasis and processed by double centrifugation according to the recommendation of the subcommittee of the Scientific and Standardization Committee of ISTH. TG measurements were performed with the calibrated automated thrombogramm assay (Stago, Asnières-sur-Seine, France) in two experimental settings: 1pM tissue factor (TF) with/without thrombomodulin (TM) and 13.6 pM TF with/without activated protein C (APC). In addition, reference plasma (Cryocheck Reference Control Normal, PrecisionBiologic, Dartmouth, Canada) was tested in all experiments in order to correct day-to-day variations. Lag time, velocity index, time to peak, peak height, endogenous thrombin potential (ETP) were measured and peak and ETP ratio obtained in presence/absence of TM or APC were calculated. Results from the reference plasma were used to calculate the normalized ETP and peak ratio in 1 pM setting and peak ratio in 13.6 pM TF setting. Results: TG was assessed in 565 patients 12 months after the index VTE. At this time, 59% of patients were still anticoagulated. Eleven percent of them had cancer-related VTE, 20% provoked VTE and 68% unprovoked VTE. The prevalence of inherited risk factors for VTE was in line with previous reports on European patients with VTE. Patients still anticoagulated 12 months after the index VTE were less likely to develop recurrent VTE in the next 24 months than patients without anticoagulation. However, the incidence of major bleeding and mortality was comparable in anticoagulated and non-anticoagulated patients. TG was faster and lower in anticoagulated than in non-anticoagulated patients. Some thrombin generation parameters measured 12 months after the index VTE (Figure 1) were discriminatory for VTE recurrence, major bleeding and mortality (Table 1). In addition, several thrombin generation parameters measured in patients not under anticoagulation 12 months after the index VTE were associated with an increased risk of VTE recurrence, major bleeding and mortality up to 24 months. These associations remained after adjustment for potential confounding factors for the risk of VTE recurrence, major bleeding and mortality (Table 2). Conclusion: In elderly patients, several parameters of thrombin generation were associated with VTE recurrence, major bleeding and/or mortality. These findings may serve as the basis for validation in a prospective interventional outcome trial. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Research on Calculation Method for Maximum Mean Acceleration in Longitudinal Train Collision

A large number of numerical simulations are required to design an energy absorption scheme for train crashworthiness, leading to low design efficiency in the early stage. Based on train collision dynamics theory and the finite element method, a dynamic finite element model of longitudinal train collision is established. According to the model, we studied the acceleration time-history characteristics during the train collision process, obtained the mean-peak ratio coefficient, and determined the calculation formula for the maximum mean acceleration of a longitudinal train collision. Through characteristic analysis of the vehicle acceleration, interface force, and other parameters during a longitudinal train collision, the calculation method of the mean acceleration was improved. The analysis shows that the maximum mean acceleration depends on two stages in the collision process: (1) the coupler action of the head vehicle: the mean-peak ratio coefficient of the head vehicle is 0.7 in this stage, and the mean-peak ratio coefficient of other vehicles is 0.43; (2) the coupler of the collision interface is cut off, and the energy absorption devices of the head vehicle or intermediate vehicle absorb energy; the mean-peak ratio coefficient of the vehicle is 0.93 in this stage. On this basis, a mathematical function is established describing the mean acceleration of the vehicle and the average crushing force of the coupler collapse tube and the energy-absorbing device. The calculation formula is obtained for the maximum mean acceleration of the longitudinal train collision, and the results are compared with the mean acceleration obtained by numerical simulation. The Kruskal–Wallis ANOVA multisample independent nonparametric test was conducted to verify the reliability of the calculation results in the 95% confidence interval. The calculation formula can be used to calculate the maximum mean acceleration in the energy allocation stage of train crashworthiness design to effectively improve the efficiency of train collision energy allocation.

Opposite Peak Ratio to Characterize Ground Motion Loading History for Performance-Based Design

Recent studies have revealed the impact of ground motion loading history on performance limit states of reinforced concrete (RC) bridge columns such as reinforcement bar-buckling and residual drift ratio. Conventional hazard characterizations such as peak ground acceleration, spectral acceleration, and spectral displacement only capture peak values of ground motion hazard and, therefore, fall short of providing the necessary information to account for these limit states. In this study, a parameter termed as the opposite peak ratio (Rop) is defined, explored, and shown to be useful in reproducing loading history characteristics of ground motions for displacement-based design. Several past ground motion records were analyzed to develop empirical models that can estimate Rop. These models provide the mean and confidence intervals of Rop as a function of earthquake magnitude, epicentral distance, structural period, hysteretic model, and displacement ductility. To motivate practitioners to make use of Rop, a design scenario and two case studies are discussed. In an RC bridge column design scenario, it is shown that having prior information about the expected Rop at the site could reduce the structural cost of the bridge. Next, case studies designed to investigate correlations between Rop and the performance limit states of RC bridge columns are discussed. By analyzing the results of nonlinear time-history analyses of numerical RC column models, it is established that Rop could potentially be a significant variable in generating fragility models for these limit-states.

Order-Based Identification of Bearing Defects under Variable Speed Condition

Condition monitoring of rotating machinery plays an important role in reducing catastrophic failures and production losses in the 4.0 Industry. Vibration analysis has proven to be effective in diagnosing rotating machine failures. However, identifying bearing defects based on vibration analysis remains a difficult task, especially in non-stationary operation conditions. This work aims to automate the process of identifying bearing defects under variable operating speeds. Based on an order analysis technique, three frequency domain features: Spectrum peak Ratio Outer (SPRO), Spectrum peak Ratio Inner (SPRI), and Spectrum peak Ratio Rolling element (SPRR) are updated to perform with non-stationary signals. The updated features are extracted from vibration data of a real ball bearing system. They are retained to build a predictive multi-kernel support vector machine (MSVM) classification model. Therefore, the effectiveness of the proposed features is evaluated based on the performance of the constructed classifier. The updated features deployed have proven their effectiveness in identifying bearing: outer race, inner race, ball, and combined defects under variable speed conditions.

Peak Ratio Characteristic Value Sequence Based Signal Processing Method for Transit-Time Ultrasonic Gas Flowmeter

The transit-time ultrasonic gas flowmeter plays a vital part in the measurement field with its unique advantages. In recent years, it has developed into a research hotspot in the field of gas flow measurement. However, while the ultrasonic signal propagates in gas, the amplitude fluctuation of the ultrasonic signal is produced under the condition of energy attenuation and unstable flow field. This leads to inaccurate transit time of ultrasonic signal that causes flow calculation errors. Aiming at this problem, a signal processing method is proposed in this paper for the transit-time ultrasonic gas flowmeter based on the peak ratio characteristic value sequence (PRCVS). Through the research on the mathematical model of ultrasonic signal, the ratio of the amplitude of adjacent peaks is defined as the peak ratio characteristic value (PRCV) of the peak. According to the corresponding relationship between the PRCV and the peak serial number, a set of reference PRCVS is established. By matching the characteristic value of the ultrasonic signal with the reference characteristic value sequence, the peak serial number can be determined. In this research, the PRCVS-based signal processing method is applied to the gas flow measurement system based on time-to-digital converter (TDC) that has strict requirements on the peak serial number which can verify the validity of the method. The calibration experiment of basic measurement performance test and the unstable flow field experiment of the curved pipe were performed on the gas flow standard device, which verified the stability and validity of the method proposed in this paper.

An eccentric wave in the circumstellar disc of the Be/X-ray binary X Persei

ABSTRACT We present spectroscopic observations of the Be/X-ray binary X Per obtained during the period 2017 December–2020 January (MJD 58095–58865). In 2017 December, the H α, H β, and He i 6678 emission lines were symmetric with violet-to-red peak ratio V/R ≈ 1. During the first part of the period (2017 December–2018 August), the V/R ratio decreased to 0.5 and the asymmetry developed simultaneously in all three lines. In 2018 September, a third component with velocity ≈250 km s−1 appeared on the red side of the He i line profile. Later, this component emerged in H β, accompanied by the appearance of a red shoulder in H α. Assuming that it is due to an eccentric wave in the circumstellar disc, we find that the eccentric wave appeared first in the innermost part of the disc, it spreads out with outflowing velocity vwave ≈ 1.1 ± 0.2 km s−1, and the eccentricity of the eccentric wave is ewave ≈ 0.29 ± 0.07. A detailed understanding of the origin of such eccentricities would have applications to a wide range of systems from planetary rings to AGNs.