Average Wave Velocity Research Articles

Clinical Outcomes of Left Ventricular Assist Device Bleeding Complication.

Bleeding complications have emerged as major causes of morbidity and mortality in patients with implantable left ventricular assist devices (LVAD). We hypothesized that the hemodynamics after LVAD implantation may influence the occurrence of bleeding complications after LVAD implantation. We retrospectively evaluated 78 patients who underwent continuous-flow LVAD implantation and hemodynamic ramp test after LVAD implantation between July 2017 and July 2023 at Osaka University. The bleeding complication occurred in 13 patients. The rates of freedom from bleeding complications at 1, 3, and 5 years were 94%, 85%, and 74%. Gastrointestinal bleeding, nose bleeding, and intraperitoneal hemorrhage occurred in six, three, and two patients, respectively. Preoperative average brachial-ankle pulse wave velocity (baPWV) was positively associated with bleeding complication (1,276 ± 280 vs. 1,098 ± 190 cm/s p = 0.04). In the hemodynamic ramp test, systemic vascular resistance (SVR) in patients with bleeding complications was higher than that in patients without bleeding complications (SVR: 1,359 ± 341 vs. 1,150 ± 217 dyne sec/cm5, p = 0.01). High preoperative baPWV and high SVR in the hemodynamic ramp test were significantly associated with bleeding complications after LVAD implantation. Arteriosclerosis is a risk factor for bleeding complications after LVAD implantation.

An experimental study on gas-solid two-phase rotating detonation ramjet engine based on aluminum powder fuel

In order to explore the feasibility of solid powder detonation technology, the ground direct connection test of aluminum powder/hydrogen/air fuel detonation engine was carried out in this paper. The experimental results show that hydrogen is needed to achieve detonation combustion of aluminum powder with a diameter of 1 μm. A series of tests were carried out in the range of equivalence ratio of 0.8-1.2. With the increase of equivalence ratio, the mean value of steady pressure, average peak pressure, and average wave velocity of rotating detonation combustion increased first and then decreased gradually, and reached the maximum at the equivalence ratio of 0.9. The maximum propagation frequency of the detonation wave is 2653 Hz, and the average wave velocity is 1667 m/s.

Arterial hypertension and stiffness in women of different age groups and reproductive status

Objective: study of the relationship between arterial hypertension and arterial stiffness in women to identify potential markers of target organ damage and therapeutic targets of antihypertensive therapy.Materials and methods: the study involved 161 women who were divided into three groups depending on age and reproductive function. Group 1 consisted of 52 women aged 18 to 30; group 2 – 54 women aged 31 years before menopause; 3rd group – 55 women in the postmenopausal period. All women were questioned, clinical examination, determination of anthropometric data, measurement of carotid-femoral pulse wave velocity, determination of arterial stiffness by volumetric sphygmography, 24-hour blood pressure monitoring with assessment of aortic stiffness and characteristics of the central pulse wave.Results: 24-hour blood pressure monitoring revealed arterial hypertension in 38 (34,8%) women: 15 (27,8%) women in the 2nd group and 23 (41,8%) women in the 3rd group. Correlation analysis revealed the most significant correlations between the presence of arterial hypertension (R=0,45-0,71; p<<0,01) with central aortic pressure, double product index and average daily aortic pulse wave velocity in the aorta (PWVao), regardless of the state reproductive function. For women of reproductive age with arterial hypertension, the ambulatory vascular stiffness index (AASI: R=0,36; p=0,01) is more significant, while in the menopausal period, the arterial stiffness index (ASI: R=0,33; p=0,01). Correlation analysis did not reveal significant relationships between carotid-femoral pulse wave velocity and cardio-ankle vascular index (CAVI) with arterial hypertension in women of the 2nd and 3rd groups. The relationship between carotid-femoral pulse wave velocity and arterial hypertension in women was confirmed by analysis of variance (p=0,007).Conclusion: Central aortic pressure, carotid-femoral pulse wave velocity, AASI, ASI, PWVao – direct and indirect indicators of arterial stiffness – are interconnected with the presence of arterial hypertension in women of reproductive and menopausal age. In this regard, these indicators are potential markers of target organ damage in arterial hypertension.

Propagation characteristics of ultrasonic in SLM manufactured AlSi10Mg

Porosity is a crucial quality evaluation criterion in metal additive manufacturing. To investigate the propagation characteristics of ultrasonic longitudinal waves with different incident frequencies in AlSi10Mg prepared by selective laser melting, specimens with varying porosity were created using printing process adjustments. Ultrasonic longitudinal wave tests and COMSOL simulations based on 2.5 MHz, 3.5 MHz, 5 MHz, and 7.5 MHz incident frequencies were carried out to establish a linear relationship between average wave velocity, average attenuation coefficient, and porosity at different frequencies. Results indicate that sound velocity and porosity are inversely proportional for each frequency longitudinal wave, while the attenuation coefficient is proportional to the porosity. Linear fitting expressions suggest that the best fit for both sound velocity and attenuation coefficient occurs at 5 MHz. Simulation results demonstrate that using 5 MHz as the incident frequency can better balance detection sensitivity and linearity. These findings provide more data support for establishing the intrinsic connection between acoustic parameters and porosity of AlSi10Mg prepared by selective laser melting in the selected area and serve as a reference for selecting ultrasonic incident frequencies in practical inspection.

Pemanfaatan Tangki Riak Untuk Mengukur Kecepatan Rambat Gelombang Permukaan Air

The study intends to investigate the relationship between wavelength and frequency to calculate the speed of propagating waves on the water's surface. The researchers used a ripple tank to collect data by recording the pendulum's movement as well as the image of the ripples on the water's surface. The data is then analyzed with the Tracker application. The wavelength is determined by analyzing the recorded ripple shadows with the Tracker application. The Tracker application is used to analyze the recorded pendulum movement to obtain data on the period of vibration and calculate the frequency of the vibrations. The average surface wave velocity at a pendulum length of 10 cm is 3.38 10-2 m/s. In addition, for a 30 cm pendulum length, an average surface wave speed of 3.26 10-2 m/s is obtained.

DFT investigations of structural stability and structure dependent physical behavior of SnO2 polymorphs

In this work, we investigated the electronic, mechanical and thermodynamic properties of various phases of SnO2 from first principles method. Here the five phases of choice are rutile, α-PbO2, CaCl2, pyrite, and ZrO2. To begin with, from the key parameters such as total energy, bond length and cohesive energy of the phases, we theoretically estimated their phase stability. Interestingly, the estimated elastic moduli are dependent on the corresponding crystal symmetry. These parameters are also comparable with reported values. Further, from the phonon dispersion relation, we recognized the dynamically stable phases. In addition, we also calculated the Debye temperature of the polymorphs from the average wave velocity, νm. Finally, we presented the relationship between the physical properties of the phases and their structural symmetry sequence. Such a relationship is not derived earlier in any theoretical and experimental report.

Closing the window on COVID-19 case-control studies.

Closing the window on COVID-19 case-control studies.

Acoustic emission detection of micro-cracks under high pressure and high temperature in a deformation large-volume apparatus at the endstation P61B, PETRA III.

We successfully developed an in situ acoustic emission (AE) detection setup that allows recording of AE waveforms (triggered and streaming) and simultaneous x-ray diffraction and imaging on samples deformed at high pressure and high temperature (HPHT) conditions in the Aster-15 Large Volume Press at the synchrotron beamline station P61B. This high pressure AE detection system is a powerful tool to investigate AE phenomena from the HPHT chamber. Six commercial acoustic sensors, protected by a tungsten carbide support ring on each anvil of the same material, have excellent survivability throughout each successive experiment. By pulsing each sensor in succession, the average wave velocity through the anvils and cell assembly can be determined at any press load. The distance between the sensors is obtained by x-ray radiography and by logging the positions of each hydraulic ram. This provides a basis for accurately locating AE events in the sample. The feasibility of this AE detection setup was confirmed by compression and deformation test runs using several different self-designed AE sources in specialized assemblies. The present setup proves to be extremely efficient and accurate in measuring brittle processes in samples under HPHT. It is now available for applications for beam time and experiments without x rays at P61B. Combined with synchrotron x rays, in situ pressure, temperature, strain rate and stress, and phase changes can be monitored while recording AE activity. We provide a powerful tool to investigate the origin of earthquakes, for example, causing AE emissions due to brittle dehydration reactions or phase transformations in the Earth.

Effects of High Temperature Treatments on Strength and Failure Behavior of Sandstone under Dynamic Impact Loads

With the increasing demand for resource consumption, the mining depths gradually increase, resulting in increases of temperature at tens or even hundreds of degrees. High temperature could damage to interior structures and alter the mechanical properties of rock mass. Therefore, studying the effects of temperature on dynamic mechanical properties and failure behaviors are of great significance for deep resources exploitation. In this study, to study the effects of high temperature treatment on the strength and failure behavior of typical sandstones, specimens were prepared and heated to different degrees. The longitudinal wave velocity, volume, and density of specimens before and after high-temperature treatment were examined. Then, the Thomas Hopkinson (SHPB) test was conducted on specimens with different air pressures and the dynamic stress-strain curve, peak stress, peak strain, and other dynamic characteristics were obtained. The variations regulations and failure behavior of sandstone under the effects of high-temperature treatments and different impact loads were analyzed and discussed from the aspects of stress-strain, peak strength, and peak strain. It was observed that with the increase of heating temperature, the average density, average wave velocity, peak strength, and average elastic modulus of the sandstone specimens all showed a decreasing trend and the highest decreasing rated occurred at the temperature between 600 °C and 800 °C. The obtained results provided a certain theoretical basis for deep mine exploitation, especially for mines with high temperature.

Research on Leakage Detection at the Joints of Diaphragm Walls of Foundation Pits Based on Ground Penetrating Radar

It is significant to monitor the leakage at the joints of the diaphragm walls of subway station foundation pits to check the weak links in the waterproof quality of the diaphragm wall structure. It is essential to take effective waterproof measurements timely to improve the overall waterproof quality of the diaphragm wall in the foundation pit to prevent accidents and reduce the operation and maintenance costs. This paper used ground penetrating radar (GPR) to detect the Lishan North Road Station section of Jinan Rail Transit Line R2 during construction. The abnormal waveform image is obtained after processing radar detection data with Reflexw software. This abnormal waveform image is used to identify the abnormal area. In order to accurately predict the location of leakage at the joint of diaphragm wall, MATLAB is used to calculate the average wave velocity amplitude and single channel signal of the electromagnetic wave velocity of geological radar at different mileages and draw the trend chart of average wave velocity amplitude with mileage and the corresponding relationship curve of electromagnetic wave amplitude and depth of radar. It is proposed that sudden changes in the area of the average wave velocity amplitude cause a change in the trend chart. Furthermore, the radar electromagnetic wave velocity amplitude curve is taken as the area where seepage may occur at the joints of the diaphragm wall, so as to determine the corresponding mileage and depth of the leakage area. On this basis, the grey correlation analysis for the analysis of the source of the water leakage at the joints of the diaphragm wall of the subway foundation pit is proposed. The research results show that the leakage water at the joints of the diaphragm wall of the subway foundation pit is not connected to the rivers around the foundation pit, which confirms that the construction of the subway station has not affected the groundwater resources around the station. The proposed approach has successfully predicted the location of the foundation pit leakage disaster and has been verified on the project site. The research results provide a reference for the monitoring and early warning of leakage at the joints of diaphragm walls in foundation pits with similar geological conditions.

THE PHYSIOLOGIC COMPLEXITY OF BEAT-TO-BEAT BLOOD PRESSURE FLUCTUATION IS ASSOCIATED WITH FRAILTY IN OLDER ADULTS

Abstract Background Beat-to-beat blood pressure (BP) is an important cardiovascular output and regulated by neurophysiologic elements over multiple temporal scales. The multiscale dynamics of beat-to-beat BP fluctuation has thus been characterized using “BP complexity” and has been linked to age-related adverse health outcomes. We here aimed to examine the relationship of BP complexity to frailty, and if BP complexity mediates the association between arterial stiffness and frailty. Method: A total of 350 older adults completed assessments for frailty (i.e., Fried frailty phenotype criteria), arterial stiffness (i.e., average brachial-ankle pulse wave velocity), and beat-to-beat finger BP. The complexity of beat-to-beat systolic (SBP) and diastolic (DBP) BP series were measured using multiscale entropy. The relationships between frailty, BP complexity and arterial stiffness were examined using ANOVA and linear regression models. The effects of BP complexity on the association between arterial stiffness and frailty were examined using mediation analyses. Results Compared to non-frail, pre-frail and frail groups had significantly elevated lower SBP and DBP complexity (F>11, p< 0.001), and greater arterial stiffness (F=16, p< 0.001). Greater arterial stiffness was associated with lower BP complexity (β<-0.42, p< 0.001). SBP and DBP complexity mediated the association between arterial stiffness and frailty (indirect effects>0.28), account for at least 47% of its total effects on frailty (Mediated proportion: SBP: 50%, DBP: 47%). Conclusion This study demonstrates that BP complexity is associated with frailty in older adults, and mediates the association between arterial stiffness and frailty, suggesting that this metric would serve as a marker to characterize important functions in older adults.

Comparative Modal Study of the Two-Dimensional and Three-Dimensional Transonic Shock Buffet

A computational comparative study of the shock buffet phenomenon is presented. A comparison between the two-dimensional airfoil buffet and the three-dimensional swept-wing buffet is made at pre-buffet and developed buffet flow conditions to shed further light on the distinct mechanisms that characterize the phenomena. We perform modal analysis using dynamic mode decomposition and compare the dominant modal shapes and time-space evolution of the wing’s full flow field to the airfoil. This allows to characterize their distinct dominant driving mechanisms. While the airfoil buffet involves a strong interaction between the shock wave and the separated boundary layer behind it, we show that the finite-wing buffet exhibits mainly spanwise traveling perturbations that induce only small chordwise shock travel, with only weak interaction between the shock wave and boundary layer. The finite-wing shock excursion distance is significantly smaller than the airfoil’s, while the average chordwise shock wave velocities are shown to be comparable, providing a physical explanation for the swept-wing buffet frequencies that are higher than those of an airfoil.

MECHANISM OF BOULDER TRANSPORT DURING EXTREME WAVE EVENTS ALONG THE EASTERN FLANK OF THE ARABIAN SEA

The study presents hydrodynamic mechanism of boulder transportation along the rocky coastal margins with a case study from the eastern flank of the Arabian Sea. Limestone blocks ranging in size from small (1.3, 0.95, 0.35) m to large (2.9, 1.68, 0.5)m scattered over a rocky platform were considered for the approximation of wave energy. The boulders with prominent imbrications indicative of flow direction were used to assess the minimum flow velocity to initiate boulder transport during extreme wave events. The irregular /polyhedral boulders, previously a part of sub-aerially exposed jointed limestone strata, were detached and transported from the rocky coastal platform under the impact of high energy waves. We calculated velocity and height for dynamic waves required to transport boulders onshore using boulder dimensions i.e., length (a-axis), width (b-axis), and height (c-axis). By applying hydrodynamic equations, it is deduced that the average wave velocity required to transport boulders of such dimensions onshore must be ≥7.28m/s and the corresponding average wave heights must be ≥5.51m and ≥1.38m in case of the storm and tsunami events respectively. Based on largest clast recorded, ≈7m high storm waves and ≈2m high tsunami waves are capable of transporting ≈2.5m3 tabular boulders along rocky coastal margins. Since this region has documented records of very-severe cyclonic storms affecting the coastal landscape in addition to the widespread impact of 1945 tsunami, we suggest that boulders deposition on the eastern flank had received inputs from storm as well as tsunami events for the last few decades.

Subsurface Weathering Zone Determination Using Down-Hole Seismic Surveys, Majnoon Oil Field, Southern Iraq

Detecting the weathering zone is one of the required data correction steps to process reflection seismic data collected at the Majnoon oil field, south of Iraq. Two subsurface layers represent the weathering zone in this field. Those two layers were inferred by primary seismic waves utilizing the down-hole seismic method. Five wells in the studied area were drilled and named DH-1, DH-2, DH-3, DH-4 and DH-5. The collected seismic data was analyzed to determine the depths, thicknesses and lithology of the subsurface layers. The primary seismic wave velocities were calculated and applied to eliminate two sub-surface layers. The average primary wave velocities and thicknesses of the first layer were 374, 240, 211, 277, 370 m/s, and 2.8, 2, 2, 2, 4.9 m, respectively. In the second layer, the primary waves velocities were 1125, 1284, 1201, 1395 and 1008 m/s, and the thicknesses were 13.2, 11, 13, 11.5, 21.4 m. The first weathered layer represented on the five wells is clay. The second layer has different geometry on different wells, which is represented by a sandy clay layer on DH-1, and muddy clay on DH-2. Then, it is changed to be a silt layer in DH-3, sandy clay in DH-4 and DH-5.

Isolated systolic hypertension is associated with increased left ventricular mass index and aortic stiffness in adolescents: a cardiac magnetic resonance study.

Despite the high prevalence of isolated systolic hypertension (ISH) among hypertensive adolescents, its clinical significance is not determined. In addition, it is hypothesized that ISH with normal central blood pressure (BP) in young patients is a benign phenomenon and was hence labeled spurious hypertension (sHTN). Using cardiac magnetic resonance we evaluated a group of 73 patients with suspected primary hypertension, aged 13-17 years (median: 16.9, interquartile range 15.8-17.4; 13 girls), in whom, based on 24-h ambulatory BP monitoring either ISH (n = 30) or white-coat hypertension (WCH) (n = 43) was diagnosed. Based on noninvasive central BP measurement 13 participants in the ISH group were classified as having sHTN and 17 were diagnosed with true hypertension. Compared with WCH adolescents, ISH patients presented with higher indexed left ventricular mass index (LVMI) (P < 0.001), maximal left ventricular (LV) wall thickness (P < 0.001), LV concentricity (P = 0.001) and more often had LV hypertrophy (47 vs. 14%, P = 0.002). They had higher average pulse wave velocity (PWV) in the proximal aorta (P = 0.016) and the whole thoracic aorta (P = 0.008). In addition, we observed higher indexed LV stroke volume (P = 0.025) in patients with ISH. The sHTN subgroup had significantly higher LVMI and aortic PWV, and more often had LV hypertrophy compared with the WCH group. The sHTN and true hypertension subgroups did not differ in terms of aortic PWV, LVMI or LV geometry. Compared with adolescents with WCH patients with ISH, including the sHTN subtype, have more pronounced markers of cardiac end-organ damage, higher aortic stiffness and stroke volume.

Structural, electronic and elastic properties of FeCrAs Half-metallic ferromagnetic Half-Heusler Alloy: A First-Principles study

In this work, we employ full potential linearized augmented plane wave approach based on the density functional theory to calculate the structural, electronic, and elastic properties of FeCrAs Half-Heusler compound. For electron exchange, we have considered the most common Generalized Gradient Approximation (PBE-GGA and PBEsol-GGA), as exchange and correlation potential for investigating these properties. The half-metallic ferromagnetic behavior is confirmed by density of states and spin-polarized band structures analysis, which show that the FeCrAs has an indirect band-gap in the spin-down channel and a metallic behaviour in the spin-up channel. Furthermore, the elastic constants (Cij) and the related elastic moduli confirm their stability in the cubic phase and demonstrate their brittle nature. The Debye’s temperature along with compressional, Shear and average elastic wave velocities has also been calculated.[copyright information to be updated in production process]

Brzina transverzalnih zvučnih talasa u stablima Pančićeve omorike (Picea omorika (Pančić) Purkyně)

In this paper, transversal stress wave velocity was measured in 30 trees of Serbian spruce (Picea omorika /Pančić/ Purk.) using a 2D sonic tomograph. Tomograms were analyzed and speed loss and average speed for Serbian spruce were calculated. Since there is no reference value for this species, in this research the reference value for stress wave velocity of Norway spruce (Picea abies /L./ H. Karst.) was used for comparison. The relative difference between referent and measured stress wave velocity indicates the amount of decay between the two sensors. The largest number of cross-sections had a speed loss of up to 10%, but there were also cross-sections with a speed loss of more than 50% in the transversal direction. This result shows that there are defects and damages in this direction that will reduce the strength of the wood. Summarizing data for trees with speed loss of less than 10%, the average stress wave velocity at the cross-sections is 1635 (1205-2170) m/s. Compared to Norway spruce, this velocity is higher, but not significantly.

Sistem Deteksi Kemurnian Minyak Goreng Dengan Menggunakan Metode Gelombang Ultrasonik

Bulk cooking oil is a food ingredient that is widely used by the public. The seller uses used bulk cooking oil to be mixed with new bulk cooking oil or even mixes it with harmful ingredients. Lab tests are needed to determine the quality of cooking oil, but the lab test requires a long time and can also damage the content of the cooking oil so it cannot be reused. The focus of this research is the creation of a system that can detect the purity of cooking oil by utilizing the wave velocity measurement method without damaging the shape and nature of the cooking oil.Wave velocity measurements are carried out by propagating ultrasonic waves on objects with a wave frequency of 40 kHz. The value of the duration of the wave propagation time at a distance of 19.4 cm is sampled and used for the calculation of wave velocity. The results of these wave velocity calculations are used to determine the purity level of cooking oil. Then the results of the purity level obtained were analyzed with an approach to the value of fluid viscosity. The results of the wave velocity values show that the waves propagate faster if the purity level of cooking oil is higher and produces a positive correlation with R2=0.9784. The results of the analysis conducted with the approach to fluid viscosity also showed a positive correlation with R2= 0.9999. The average wave velocity in pure bulk cooking oil is 1174.90 m/s.

Study on Changes in Wave Velocity in Surrounding Tunnel Rock under Different High In-situ Stresses

Studies have indicated that in the tunnel’s surrounding rock, high in-situ stress influences the wave velocity changes. Under different ground stresses, an underground model system is used to study the propagation characteristics of the blasting seismic wave velocity. The electric spark was used to recreate explosive blasting by employing a model loading system to simulate gradient loading under high in-situ stress in the tunnel. The DH5983 dynamic signal analytical system was used to collect the vibration acceleration and calculate the average velocity. The average radial and axial wave velocities gradually increased with increasing in-situ stress, and the increase in the average radial wave velocity was greater than the axial wave velocity, according to the test results. The growth rate of the average wave velocity gradually slowed down under various high in-situ stressors, with that in the low in-situ stress stage being greater than in the high in-situ stress stage. A logarithmic growth trend is seen when the wave velocity gradually becomes constant. The average decay growth rate of the radial wave velocity was larger than the rate of axial velocity, which was approximately 1.5 times.

Influence of high pressure on structural, electronic and mechanical properties of tetragonal FeH5

First-principles method is performed to investigate the structural, electronic, and mechanical characteristics of the tetragonal I/4mmm-FeH5 in the pressure range from 100GPa to 300 GPa. At 130 GPa and 150 GPa, the lattice parameters of I/4mmm-FeH5 are matched well with available values. The pressure has a more significant influence on the c→ direction than the a→and b→ direction. Electronic calculations predicted that the I4/mmm-FeH5 has weak metallic behaviors and the ionic bond between Fe and H atom under pressure. The obtained elastic constants reveal the I/4mmm-FeH5 is mechanically stable between 100 GPa and 300 GPa. The bulk, shear, and Young's modulus are evaluated by Voigt-Reuss-Hill approximation. All these polycrystalline elastic moduli exhibit a monotonic feature as a function of pressure. The Poisson's ratio, Pugh's criterion, and Cauchy pressure indicate that the I4/mmm-FeH5 is ductile against pressure. Mechanical anisotropy is evaluated through several physical parameters. Finally, the Debye temperature estimated from the average wave velocity is found to monotonically increase with pressure.