Damage Evolution of Ballastless Track Concrete Exposed to Flexural Fatigue Loads:The Application of Ultrasonic Pulse Velocity,Impact-echo and Surface Electrical Resistance Method

In order to clarify the fatigue damage evolution of concrete exposed to flexural fatigue loads,ultrasonic pulse velocity(UPV),impact-echo technology and surface electrical resistance(SR) method were used.Damage variable based on the change of velocity of ultrasonic pulse(Du) and impact elastic wave(Di)were defined according to the classical damage theory.The influences of stress level,loading frequency and concrete strength on damage variable were measured.The experimental results show that Du and Di both present a three-stages trend for concrete exposed to fatigue loads.Since impact elastic wave is more sensitive to the microstructure damage in stage Ⅲ,the critical damage variable,i e,the damage variable before the final fracture of concrete of Di is slightly higher than that of Du.Meanwhile,the evolution of SR of concrete exposed to fatigue loads were analyzed and the relationship between SR and Du,SR and Di of concrete exposed to fatigue loads were established.It is found that the SR of concrete was decreased with the increasing fatigue cycles,indicating that surface electrical resistance method can also be applied to describe the damage of ballastless track concrete exposed to fatigue loads.

Micro-destructive assessment of subgrade compaction quality using ultrasonic pulse velocity

The ultrasonic pulse velocity(UPV)correlates significantly with the density and pore size of subgrade filling materials.This research conducts numerous Proctor and UPV tests to examine how moisture and rock content affect compaction quality.The study measures the changes in UPV across dry density and compaction characteristics.The compacted specimens exhibit distinct microstructures and mechanical properties along the dry and wet sides of the compaction curve,primarily influenced by internal water molecules.The maximum dry density exhibits a positive correlation with the rock content,while the optimal moisture content demonstrates an inverse relationship.As the rock content increases,the relative error of UPV measurement rises.The UPV follows a hump-shaped pattern with the initial moisture content.Three intelligent models are established to forecast dry density.The measure of UPV and PSO-BP-NN model quickly assesses compaction quality.

Characteristics of near-fault ground motion containing velocity pulses

There are many reports about the research on near-fault velocity pulses, which focus on the generation of velocity pulse and simplify the velocity pulse so as to be used in the seismic design of structure, However few researches have put emphasis on the characteristics of near-fault ground motions containing velocity pulses, especially the characteristics relevant with the design response spectrum prescribed by the code. Through collection of a large number of near-fault records containing velocity pulses, the response spectra and the characteristic periods of records containing no pulses are compared with those of records containing pulses. Response spectra of near-fault records are compared with standard spectra given by code; furthermore, the response spectra and the characteristic periods of each earthquake are compared with that given by code. The result shows that at long periods （longer than 1.5 s）, the response spectrum of pulse-containing records is bigger than the response spectrum of no-pulse-containing records; when the characteristic period of near-fault records is calculated, the method that does not fix frequency is more reasonable because the T1 and T2 have a lagging tendency; regardless of the site Ⅰ and site Ⅱ, the characteristic period of pulse-containing records is over twice bigger than the characteristic period given by the code,

Study on equivalent velocity pulse of nearfault ground motions

Near-fault strong ground motions that resulted in serious structural damage are characterized by directivity effect and pulse-type motion. Large-amplitude and long-period pulses are contained in the velocity time-history traces of near-fault pulse-type records. A reasonable model of equivalent velocity pulse is proposed on the basis of the ex- isted models in this paper to simplify the calculation and analysis. Based on the large amount of collected near-fault strong earthquakes records, the parameters describing equivalent velocity pulse model such as pulse period, pulse intensity and number of predominant pulses are studied, and comparison is made with the results obtained by others models. The proposed model is contributive to the seismic design for structures in near-fault areas.

Preliminary analysis of the hanging wall effect and velocity pulse of the 5.12 Wenchuan earthquake

A preliminary study of the PGA attenuation, hanging wall effect and velocity pulse characteristics from the 2008 Wenchuan earthquake ofMS -8.0 is described in this paper. The study was carried out through analyses in the time and frequency domains of main earthquake records. In the PGA attenuation study, records from 316 stations less than 1000 km from the surface rupture of the fault were used as a database and attenuation relationships were developed and compared with some existing relationships that are widely used in China's Mainland, Chinese Taiwan and the US. At the same time, records from 28 stations less than 100 km from the fault were used to study the hanging wall effect and velocity pulse characteristics of this earthquake based on the distribution of PGA, PGV, spectral acceleration, and the velocity pulse peak, and the results are compared with the 1999 Chi-Chi earthquake. In addition, the large PGAs of the UD components observed in this event are also discussed in this paper. From the results of the preliminary study, some conclusions are developed and suggestions for further research are proposed.

Effect of source parameters on forward-directivity velocity pulse for vertical strike slip fault in half space

It has been found that the large velocity pulse is one of the most important characteristics of near-fault strong ground motions. Some statistical relationships between pulse period and the moment magnitude for near-fault strong ground motions have been established by Somerville （1998）; Alavi and Krawinkler （2000）; and Mavroeidis and Papageorgiou （2003）, where no variety of rupture velocity, fault depth, and fault distance, etc. were considered. Since near-fault ground motions are significantly influenced by the rupture process and source parameters, the effects of some source parameters on the amplitude and the period ofa forward-directivity velocity pulse in a half space are analyzed by the finite difference method combined with the kinematic source model in this paper. The study shows that the rupture velocity, fault depth, position of the initial rupture point and distribution of asperities are the most important parameters to the velocity pulse. Generally, the pulse period decreases and the pulse amplitude increases as the rupture velocity increases for shallow crustal earthquakes. In a definite region besides the fault trace, the pulse period increases as the fault depth increases. For a uniform strike slip fault, rupture initiating from one end of a fault and propagating to the other always generates a higher pulse amplitude and longer pulse period than in other cases.

Ankle-brachial index and brachial-ankle pulse wave velocity are risk factors for ischemic stroke in patients with type 2 diabetes

The incidence of ischemic stroke in patients with diabetes is increasing. While brachial-ankle pulse wave velocity （BaPWV） and ankle-bra- chial index （ABI） are known to be associated with ischemic cardiovascular and cerebrovascular diseases, whether these measures predict the risk of ischemic cerebrovascular disease in diabetic patients remains unclear. 117 patients with type 2 diabetes were enrolled in this study. According to the results of head magnetic resonance imaging, the patients were divided into a diabetes-only group （n = 55） and a diabetes and ischemic stroke group （n = 62）. We then performed ABI and BaPWV examinations for all patients. Compared with the diabe- tes-only group, we found decreased ABI and increased BaPWV in the diabetes and ischemic stroke group. Multivariate logistic regression analyses revealed that BaPWV and ABI were risk factors for ischemic stroke in patients with type 2 diabetes. Our findings indicate that decreased ABI and increased BaPWV are objective indicators of increased risk of ischemic stroke in patients with type 2 diabetes.

Serum Calcium Level is Associated with Brachial-ankle Pulse Wave Velocity in Middle-aged and Elderly Chinese

Objective To study the relation between serum calcium level and elevated BaPWV in Chinese subjects. Methods The relation between serum calcium level and elevated BaPWV was studied in 9 615 subjects. The mean value of left and right BaPWV was analyzed. BaPWV was defined as high when it was31 752.5 cm/s （the upper quartile） either side. Results The BaPWV and its elevated percentage progressively increased across the quartiles of the serum calcium level （P〈0.05）. The prevalence of elevated BaPWV was significantly higher in subjects of the second, third and highest quartiles than in those of the lowest quartile （26.9%, 28.4%, and 33.2%vs 23.7%, P=0.0116, P=0.0004, and P〈0.0001）. Logistic regression analysis revealed that the risk of elevated BaPWV was 1.32- fold higher in subjects of the highest quartile than in those of the lowest quartile （OR=1.32, 95%CI：1.08-1.60）. Conclusion The elevated serum calcium level is related to an elevated BaPWV and a higher risk of arterial stiffness, independent of conventional risk factors, in middle-aged and elderly Chinese subjects.

A model for predicting bubble rise velocity in a pulsed gas solid fluidized bed

Bed stability, and especially the bed density distribution, is affected by the behavior of bubbles in a gas solid fluidized bed. Bubble rise velocity in a pulsed gas-solid fluidized bed was studied using photographic and computational fluid dynamics methods. The variation in bubble rise velocity was investigated as a function of the periodic pulsed air flow. A predictive model of bubble rise velocity was derived: ub=ψ(Ut+Up-Umf)+kp(gdb)(1/2). The software of Origin was used to fit the empirical coefficients to give ψ = 0.4807 and kp = 0.1305. Experimental verification of the simulations shows that the regular change in bubble rise velocity is accurately described by the model. The correlation coefficient was 0.9905 for the simulations and 0.9706 for the experiments.

Brachial-ankle pulse wave velocity is an independent predictor of carotid artery atherosclerosis in the elderly

Objective Brachial-ankle pulse wave velocity （baPWV） is widely used as a simple noninvasive measure of arterial softness. The aim of this study was to evaluate the usefulness of baPWV as a predictor of the carotid artery atherosclerosis in the elderly. Methods A total of 721 elderly participants （mean ~ SD age, 70.3 -4- 5.6years） were enrolled in the current study. All participant underwent both baPWV measurement and B-mode ultrasound for the intima-media thickness. Carotid atherosclerosis （CAS） was defined as the present of carotid plaque or and/or intima media thickness for at least 1.1 mm. Results A multivariate logistic regression analysis reveals that age, sex, brachial-ankle pulse wave velocity, smoking and LDL-C level showed a significant correlation with the presence of CAS. The odds ratios of CAS associated with a 500cm/s increase of brachial-ankle pulse wave velocity were 2.378 [95% confidence interval, 1.36 to 4.00, P〈0.05], 3.733 [95% confidence interval, 1.729 to 8.058, P〈0.01], 4.438 [95% confidence interval, 1.659 to 11.803, P〈0.01]. The baPWV significantly correlated with IMT by bivariate correlation analysis （r=-0.39; p=0.001）. After adjusting for factors influencing, baPWV all the same correlated with IMT （r=-0.35; p=0.001）.Conclusion These results indicate that brachial-ankle PWV is an independent predictor of CAS in the elderly.It also means that the direct measurement of arterial stiffness by this simple method may be of great help for the evaluation of carotid artherosclerosis, at least in the elderly

Relationship between brachial-ankle pulse wave velocity and metabolic syndrome components in a Chinese population

The purpose of this study was to assess the relationship between arterial stiffness, as measured by brachial-ankle pulse wave velocity （baPWV）, and the presence of the metabolic syndrome （MS） in a Chinese population. A total of 4,445 subjects were enrolled. The prevalence of MS in for the general population, males and females, respectively. our study population was 21.7%, 17.2% and 25.6% With adjustments for age, gender, cigarette smoking, heart rate, total cholesterol, low-density lipoprotein （LDL） cholesterol, and the use of anti-hypertensive drug, the stepwise regression analysis showed that baPWV had a significant relationship with components of MS, including systolic blood pressure （P 〈 0.001）, diastolic blood pressure （P 〈 0.001）, glucose （P 〈 0.001）, highdensity lipoprotein （HDL） cholesterol （P = 0.04）, and triglycerides （P 〈 0.001）, but no relationship with waist circumference （P = 0.25）. With an increase in the number of the MS components, baPWV increased significantly both in women and men. This study indicated that the MS is indeed a risk factor for arterial stiffness. Monitoring of baPWV in patients with MS may help in identifying persons at high risk for cardiovascular disease.

The value of pulse wave velocity in the diagnosis of coronary heart disease

Objective: Using receiver operating characteristics (ROC) curve to evaluate the value of pulse wave velocity (PWV) in the diagnosis of coronary heart disease (CHD). Methods: By using coronary angiography as golden diagnostic standard of CHD, 218 patients were divided into both CHD group (n=121) and non-CHD group (n = 97). All these patients received PWV test. The efficacy of PWV of each artery segments in the diagnosis of CHD was evaluated by ROC curve. The sensitivity and specificity were calculated with the golden diagnostic standard of CHD. Results:The PWV of right carotid to femoral artery (Rc-f), left carotid to femoral artery (Lc-f), right radial to carotid artery (Rc-r), left radial to carotid artery (Lc-r) in CHD group were significantly higher than that of non-CHD group (9. 31±1. 75 vs 7.60±1.59, P<0. 01; 9. 02±1.71 vs 7. 52±1.50, P<0. 01; 8. 69±1. 37 vs 8. 00±1. 27, P<0. 01; 8.52±1. 03 vs 8. 03±1. 2, P<0. 01 respectively). However, the PWV of both right and left femoral to ankle artery (Rf-a and Lf-a) had no significant differences between the two groups. We then compared the area under curve (AUC) of each ROC(AUCROC) of PWV of Rc-f, Lc-f Rc-r and Lc-r to evaluate their diagnostic efficacy for CHD. We found that AUCROC of Rc-f PWV was the biggest (AUCROC = 0. 818), at the peak point of its ROC curve, the PWV was 8. 32 m/s. PWV>8. 32 m/s of Rc-f could predict the presence of CHD with a sensitivity of 79% and specificity of 77%. Conclusion: The PWV of Rc-f, Lc-f, Rc-r, Lc-r are significantly higher in CHD group than that in non-CHD group, and PWV of Rc-f is the most accurate in the detection of CHD. The PWV>8. 32 m/s of RC-F is a valuable predictor of CHD.

Design aspect of a novel L-shaped pulsed column for liquid–liquid extraction applications: Energy consumption and the characteristics velocity concept

This article deals with the evaluation of the consumption of energy for a steady state solvent extraction in a novel L-shaped pulsed sieve-plate column, which is highly required for design and optimization of the periodic flow processes for industrial applications. In this regard, a comprehensive evaluation on the energy consumption in case of a pulsed flow for three different chemical systems is conducted and besides the influence of pulsation intensity, the effect of geometrical parameters including the plate spacing and the plate free area is investigated as well. Moreover, the concept of characteristic velocity models at flooding points is evaluated with respect to the variation of pressure drop along the column at different operational conditions.

Relationship between the Plasma Fibulin-1 Levels,Pulse Wave Velocity,and Vascular Age in Asymptomatic Hyperuricemia

Fibulin-1(FBLN-1),an elastin-associated extracellular matrix protein,has been found in blood and may play a role in the pathophysiological processes leading to cardiovascular disease(CVD).We aimed to investigate the relationship between fibulin-1 levels and the risk of CVD by evaluating vascular age derived from the Framingham Heart Study and brachial-ankle Pulse Wave Velocity(baPWV)in patients with asymptomatic hyperuricemia(AHU).In total,66 patients with AHU and 66 gender-and age-matched healthy individuals were enrolled.The plasma fibulin-1 levels were measured by immunochemistry.Patients with AHU presented significantly higher vascular age[median(interquartile range):54(22)vs.48(14)years,P=0.01]and baPWV[mean±SD:1373±223 vs.1291±177 cm/s,P=0.02]than the healthy subjects;however,no significant difference was observed in the plasma fibulin-1 level between the patients with AHU and healthy subjects[median(interquartile range):4018(3838)vs.3099(3405)ng/mL,P=0.31].A correlation between fibulin-1 levels and baPWV was observed only in patients with AHU(r=0.29,P=0.02);and there was also a suggestively statistically significant correlation between fibulin-1 levels and vascular age(r=0.22,P=0.08).However,these associations were rendered insignificant after adjustments for potential confounders.In healthy subjects,no correlation was observed between fibulin-1 levels and CVD risk.This study reveals that plasma fibulin-1 levels may reflect the CVD risk in patients with AHU,but the relationship is not robust.

Altered heart rate variability and pulse-wave velocity after spinal cord injury

BACKGROUND Heart rate variability(HRV) and pulse-wave velocity(PWV),indicators of cardiac function,are altered in patients with spinal cord injury(SCI),suggesting that autonomic cardiac function and arterial stiffness may underlie the high risk of cardiovascular complications in these patients.No study has simultaneously investigated HRV and PWV in the same patients.AIM To evaluate cardiovascular complications in SCI patients by comparing HRV and PWV between patients with and without SCI.METHODS In this cross-sectional pilot study,patients with(n = 60) and without SCI(n = 60) were recruited from December 7,2019 to January 21,2020.Each participant received a five-minute assessment of HRV and the cardiovascular system using the Medicore HRV Analyzer SA-3000 P.Differences in HRV and PWV parameters between participants with and without SCI were statistically examined.RESULTS We observed a significant difference between participants with and without SCI with respect to the standard deviation of all normal-to-normal intervals,square root of the mean sum of squared successive risk ratio interval differences,physical stress index,total power,very-low frequency,low frequency,high frequency,and arterial elasticity.CONCLUSION Patients with SCI have weaker sympathetic and parasympathetic activity as well as lower arterial elasticity compared to those without,suggesting that SCI may increase cardiac function loading.

STUDY OF PULSED DOPPLER SIGNAL PROCESSING AND VELOCITY TRACKING TECHNIQUE

This paper describes a signal processing system in a Pulsed Doppler (PD) radar. It mainly consists of a velocity tracking loop and a digital signal processing auxiliary channel. With many signal processing techniques, the system successfully solves the signal detection and tracking at low SNR and the interference identification and rejection. The idea of system design is introduced in detail. Finally, some simulation and experimental results are presented.

Association of Estimated Pulse Wave Velocity and the Dynamic Changes in Estimated Pulse Wave Velocity with All-Cause Mortality among Middle-Aged and Elderly Chinese

Objective We aimed to clarify the association between estimated pulse wave velocity(ePWV)and the changes in ePWV with all-cause mortality among middle-aged and elderly Chinese.Methods Data were obtained from the China Health and Retirement Longitudinal Study(CHARLS)from 2011-2018.The ePWV was calculated using an equation that included age and mean blood pressure(MBP).The ΔePWV was assessed as the difference in ePWV between the first two waves.Cox proportional hazard models were used to determine the association between ePWV and ΔePWV with all-cause mortality after adjustment for potential confounders.Results Of 13,116 participants during a median follow-up of 7.0 years,1,356 deaths occurred.An increased ePWV was independently associated with all-cause mortality.The hazard ratio[95% confidence interval(CI)]for participants from the 1^(st)-4^(th) quartile groups was 1.00,1.69(1.31-2.18),3.09(2.44-3.91),and 8.54(6.78-10.75),respectively.Each standard deviation(SD)increment of ePWV increased the risk of all-cause mortality by 132%.Furthermore,theΔePWV was significantly associated with a 1.28-fold(95%CI,1.18-1.38)risk of all-cause mortality per SD increment.Conclusion This cohort study provided novel evidence from a Chinese population that an increased ePWV or progression of the ePWV was independently associated with all-cause mortality,which highlighted the importance of mitigating ePWV progression in clinical practice.

Effect of Curing Age on Tensile Properties of Fly Ash Based Engineered Geopolymer Composites(FA-EGC)by Uniaxial Tensile Test and Ultrasonic Pulse Velocity Method

Tensile properties of fly ash based engineered geopolymer composites(FA-EGC)at different curing ages were studied by uniaxial tensile test and ultrasonic pulse velocity(UPV)methods,which included uniaxial tensile properties,the correlation between ultrasonic pulse velocity and tensile properties,and characteristic parameters of microcracks.The experimental results show that obvious strain hardening behavior can be found in FA-EGC at different curing ages.With the increase of curing age,the tensile strength increases,the tensile strain decreases and the toughness becomes worse.The UPV of FA-EGC increases with curing age,and a strong correlation can be found between tensile strength and UPV.With the increase of curing age,the average crack width of FA-EGC decreases and the total number of cracks increases.This is because the strength of geopolymer increases fast at early age,thus the later strength development of FA-EGC tend to be stable.At the same time,the bond strength between fiber and matrix,and the friction of fiber/matrix interface continue to increase with curing age,thus the bridging effect of fiber is gradually strengthened.In conclusion,the increase of curing age is beneficial to the development of tensile properties of FA-EGC.

Prediction of Compressive Strength Using Ultrasonic Pulse Velocity for CLSM with Waste LCD Glass Concrete

The purpose of this paper is to develop a prediction model of WGCLSM （waste LCD （liquid crystal display） glass controlled low strength materials） concrete, the relationship between UPV （ultrasonic pulse velocity） and compressive strength, UPV-strength model. The power function was used to perform the nonlinear-multivariate regression analysis of UPV with water-binder ratio （w/b）, curing age （t） and waste glass content （G） in our previous study. Test results show that the compressive strength increases with UPV and approach to a linear relationship. Thus, the UPV-strength model was established by linear-multivariate regression analysis and the compressive strength evaluated by ultrasonic pulse velocity. The calculated results are in accordance with the laboratory measured data ultrasonic pulse velocity and compressive strength. In addition, the statistical analysis shows that the coefficient of determination R2 and the MAPE （mean absolute percentage error） were from 0.916 to 0.951 and 12.6% to 15.1% for the compressive strength, respectively. The proposed models are highly accurate in predicting the compressive and ultrasonic pulse velocity of WGCLSM concrete. However, with other ranges of mixture parameters, the predicted models must be further studied.

Statistical Modelling of Ultrasonic Pulse Velocity of Fly Ash Based Geopolymer Mortar using Response Surface Methodology

The fly ash based geopolymer has emerged as a capable and sustainable binder material in construction industry.Ultrasonic pulse velocity(UPV)method is a non-destructive technique for investigating the mechanical performance of concrete.Experimental investigation was performed for studying the effect of NaOH Molarity,Na2SiO3/NaOH and curing temperature on the ultrasonic pulse velocity of geopolymer mortar.Experiments were designed based on central composite design(CCD)technique of response surface methodology(RSM).Statistical model was developed and statistically validated and found significant as the difference between adjustable R-squared and predicted R-squared less than 0.2.Finally,the optimized mix proportion was assessed for maximized value of UPV.Experimental validation on the optimized mix reveals the close agreement between experimental and predicted values of UPV with significance level of more than 95%.The proposed technique improves the yield,the reliability of the product and the processes.