Flow Velocity Research Articles

A practical risk model based on Lasso-Cox regression for angina with nonobstructive coronary arteries (ANOCA) patients

Abstract Background Coronary flow reserve (CFR) reduction is currently one of the main criteria for risk-stratifying patients with angina and nonobstructive coronary artery disease (ANOCA). However, CFR depends on resting and vasodilated coronary hemodynamics, and a theoretical concern remains that physiological changes may inadvertently affect the result. Purpose We aim to fit different risk models for patients with ANOCA, which further provides applicable guidance to clinical doctors for their patients. Methods Between May 2018 and October 2023, 251 consecutive patients who were diagnosed as ANOCA were enrolled from Qilu Hospital of Shandong University, and the median follow-up was 800 (493, 1221) days. Demographic characteristics, cardiovascular risk factors, cardiac structure and function index, echocardiography-derived coronary flow velocity, coronary flow velocity-time integral, and CFR were collected. Least absolute shrinkage and selection operator (LASSO) and multivariable Cox regression analyses were used to screen for significant parameters that were included to develop a novel predictive nomogram model. Receiver operating characteristic curve and calibration curve were used to evaluate the performance and clinical utility of the nomogram. Results In LASSO regression selection, five variables, diabetes, global work efficiency (GWE), global wasted work (GWW), decreased hyperemic coronary flow velocity (<0.63m/s), and peak flow velocity-derived CFR<2.5 (Figure 1) showed their correlation to the occurrence of major adverse cardiovascular events (MACE). Univariate Cox regression analysis shows that diabetes (hazard ratio [HR] = 4.108; 95% confidence interval [CI], 2.296–7.350; p = 0.001), GWE (HR = 0.890; 95% CI, 0.856–0.926; p = 0.001), GWW (HR = 1.005; 95% CI, 1.004–1.007; p = 0.012), decreased hyperemic coronary flow velocity (HR =3.405; 95% CI, 1.730–6.702; p = 0.001) and peak flow velocity-derived CFR<2.5 (HR =3.456; 95% CI, 1.898–6.292; p = 0.001) were predictors of recurrent chest pain. Multivariate analysis showed that the association of diabetes (HR = 2.735; 95% CI, 1.452–5.152; p = 0.002), GWW (HR = 1.004; 95% CI, 1.001–1.007; p = 0.010), and peak flow velocity-derived CFR<2.5 (HR = 2.650; 95% CI, 1.306–5.380; p = 0.007) with MACE remained statistically significant after adjusting for other variables. A nomogram incorporated the predictors mentioned above; it is presented in Fig.2. Internal validation showed that the model has good predictive performance. The areas under the curve (AUCs) for prediction of the risk of MACE was 0.849 (Fig.3). The calibration curve for predicting chest pain recurrence shows a good agreement between prediction and observation (Fig.4). Conclusions Diabetes, GWE, GWW, decreased hyperemic coronary flow velocity (<0.63m/s), and peak flow velocity-derived CFR<2.5 are significant in identifying the occurrence risk of MACE for ANOCA patients.

Predicting the severity of valvular heart diseases using ai integrated with ECG and anthropometric data

Abstract Background AI has been used in studies to predict the severity of aortic stenosis (AS) from electrocardiography (ECG), but the application of AI to predict the severity of aortic regurgitation (AR), mitral regurgitation (MR) and tricuspid regurgitation (TR) has not been widely explored. This study aimed to determine whether deep learning can predict the severity of valvular heart disease (AS, AR, MR and TR) assessed by echocardiography using ECG data. Methods and Results We analyzed data from 31,787 adult patients who underwent ECG and echocardiography within three days of each other between 2014 and 2019 at two hospitals. Valvular heart diseases, including AS, AR, MR, and TR, were classified into categories; normal, mild, moderate, and severe; according to guidelines. ECGs, along with patient age, gender, height, and weight, were inputs to a LightGBM machine learning model. The model was trained on 80.6% of the data, with the remaining 19.4% used for validation. The sensitivity for predicting moderate or severe valvular heart disease was 85% for AS, 88% for AR, 85% for MR, and 85% for TR. The negative predictive values for AS, AR, MR, and TR were all 100%. Prediction accuracies for the severity of each disease were AS at 0.857, AR at 0.871, MR at 0.855, and TR at 0.890. Predictions based on AS diagnostic parameters; mean pressure gradient, valve area, and maximum blood flow velocity also showed favorable accuracies at 0.891, 0.821, and 0.877, respectively. Conclusion Integrating AI with standard clinical parameters, including ECG data, height, and weight, showed potential in accurately predicting the severity of various valvular heart diseases. Further researches across diverse populations and settings are necessary to validate the approach's effectiveness and explore its impact on patient care.

Assessing boundary conditions in CFD for transvalvular pressure gradient calculation in cardiac hemodynamics

Abstract Background Computational fluid dynamics (CFD), which has the advantages of providing detailed pressure distribution, has been widely used for cardiac function assessment and heart disease diagnosis. However, the results are usually influenced by the boundary conditions. Particularly, the transvalvular pressure gradient, which serves as a crucial indicator for mitral stenosis and the efficacy of mitral valve surgery, can easily be miscalculated. Here, we assess the effects of widely used boundary conditions on the transvalvular pressure gradient computed based on the Bernoulli equation and the line probe, respectively. Purpose This study aims to determine the effects of boundary conditions on the transvalvular pressure gradient in CFD. Methods We constructed cardiac models including left atrium, left ventricle, aorta from CT and mitral valve from transesophageal echocardiography data (Figure 1). The intraventricular flow fields were computed using CFD tool with four different boundary conditions (BC) at the same cardiac output. BC1 involved specifying the total flow rate of the aorta, with zero pressure at the entrance of the pulmonary veins. BC2 maintained equal flow rates at the entrances of the pulmonary veins. BC3 followed Murray's law, where the flow rate ratio in the pulmonary veins is proportional to the 1.5 power of the area ratio. BC4 followed Poiseuille's law, where the flow rate ratio is proportional to the square of the area ratio. The results encompassed the mean transvalvular pressure gradient and peak transvalvular pressure gradient obtained through the Bernoulli equation and the line probe methods, respectively. Results Figures 2(A-D) present the contours of transvalvular pressure under peak flow velocity conditions and the isosurfaces of vorticity within the ventricle. The results show that the pressure within the atrium is notably lower in the BC2, leading to a 63% underestimation in the mean transvalvular pressure gradient and a 22.9% deviation in the peak transvalvular pressure gradient (Figure 2 F). The transvalvular pressure gradient for BC1, BC3, and BC4 do not exceed 10%. The results reveal that the pressure distribution and vorticity within the ventricle are consistent, primarily due to the influence of the mitral valve. Conclusion When evaluating transvalvular pressure gradient using CFD, it is crucial to specify appropriate boundary conditions. Using inappropriate boundary conditions may lead to underestimation of the transvalvular pressure gradient, thereby affecting further diagnostic decisions. In research studies, it is recommended to allocate flow in different branch vessels according to Murray's law, where the flow in different branch vessels is proportional to the 1.5 power of the vessel cross-sectional area.Modelling flow chartTransvalvular pressure gradient

Effect of Dexmedetomidine Versus Propofol Sedation on The Cerebral Blood Flow Velocity and Cerebral Metabolic Rate of Oxygen in Patients With Traumatic Brain Injuries

Effect of Dexmedetomidine Versus Propofol Sedation on The Cerebral Blood Flow Velocity and Cerebral Metabolic Rate of Oxygen in Patients With Traumatic Brain Injuries

Prognostic significance of coronary flow velocity reserve in patients with peripheral arterial disease

Abstract Background Patients with lower extremity peripheral arterial disease (PAD) have a higher risk of cardiovascular events. Stress echocardiography (SE) based on regional wall motion abnormality (RWMA) is imperfect for risk stratification in PAD, but it can be complemented with an assessment of coronary flow velocity reserve (CFVR) in the mid-distal left anterior descending coronary artery. Purpose To assess the value of SE with RWMA and CFVR to predict survival in PAD. Methods In a retrospective analysis of prospectively acquired data in an observational, multicenter study, we recruited 359 patients (age 69±8 years, 240 [67%] males) with PAD referred for dipyridamole SE in 3 accredited laboratories. We assessed RWMA and CFVR (abnormal value <2.0). All patients were followed up for a median of 4.7 (interquartile range: 2.0 to 8.2 years). All-cause death was the outcome end-point. Results The positivity rate was 37/359 (10%) for RWMA and 159/359 (44%) for CFVR. During follow-up, 97 (27%) deaths were registered. At multivariable analysis, inducible RWMA and/or CFVR <2.0 (HR 2.58, 95% CI 1.65-4.04; p<0.0001), age ≥70 years, diabetes, dialysis treatment, and ejection fraction ≤50% were associated with decreased survival. The annual mortality was 7.4% in patients with RWMA and/or CFVR <2.0 and 2.7% in those with no RWMA and CFVR >2.0 (Figure, p<0.0001). Conclusion In patients with PAD, SE shows more than 4-fold higher prevalence of abnormal CFVR compared to RWMA. The prognostic value of CFVR outperforms RWMA, showing the importance of coronary microvascular dysfunction and diffuse, subcritical coronary atherosclerosis in determining the outcome.

Sinus rhythm maintenance and the changes of echocardiographic parameters in patients with late persistent atrial fibrillation at 6 months after direct current cardioversion

Abstract Background Late persistent non-valvular atrial fibrillation (AF), with a duration of its episode ≥90 days and up to 12 months, is considered a distinct persistent AF entity, which might possess substantial differences as compared to its early persistent pattern (up to 3 months) in terms of myocardial remodeling and its reversibility after cardioversion. Purpose To study the changes of echocardiographic parameters in patients with non-valvular late persistent AF with respect to sinus rhythm (SR) maintenance at 6 months after successful direct current cardioversion (DCCV). Methods The cohort single-center study enrolled 59 late persistent AF patients, who underwent a successful elective DCCV. At 6-months follow-up, patients were subdivided into the groups regarding SR maintenance: 32 (54 %%) patients with a maintained SR (G1), and 27 (46 %) patients with a failure to maintain SR (G2). The parameters of myocardial remodeling and function were evaluated by transthoracic (TTE) and transesophageal echocardiography (TEE) baseline (by TTE and TEE) and at 6-months follow-up (by TTE). Results TTE data from G1 patients, in contrast to G2, suggested better baseline status of left heart chambers, particularly the lower diameter of left atrium (LA), left ventricular (LV) end-diastolic and end-systolic volumes and higher LV systolic function (by LV ejection fraction [EF]). According to the TEE data, G2 (vs. G1) was characterized by more prevalent cases of LA spontaneous (echo) contrast (41 % vs. 15 %, respectively; p=0,042) and LA appendage flow velocity ≤40 cm/s (82 % vs. 53 %, respectively; p=0,022). At 6-months follow-up TTE, G1 patients, as opposed to G2, demonstrated a better profile of echocardiographic parameters, namely a lower LA diameter, LA and right atrium (RA) volumes, along with less advanced LV remodeling and higher LV EF. TTE data from G1 at 6-months follow-up after DCCV suggested the reverse remodeling of both atria, namely the decrease of LA diameter, LA volume and its index (Fig. 1), as well as RA volume and its index. Moreover, G2 demonstrated a decline in LV systolic function, in particular the rise of LV end-systolic volume and decrease of LV EF (Fig. 2), as compared to G1. Furthermore, at 6-months follow-up, G2 patients presented with more advanced severity of PH and tricuspid regurgitation, in comparison with G1. Conclusions Late persistent AF patients with a SR maintenance at 6-months follow-up after successful DCCV presented a better baseline profile of myocardial remodeling and systolic function. The SR maintenance at 6-months follow-up after DCCV was associated with the reverse remodeling of left heart chambers (LA and LV) and RA. On the contrary, a failure to maintain SR in late persistent AF patients was associated with a deterioration in LV systolic function, and more advanced PH and tricuspid regurgitation.

Effects of Stumping and Meteorological Factors on Sap Flow Characteristics of Haloxylon ammodendron in Ulan Buh Desert, Northwestern China

The shrub/dwarf tree Haloxylon ammodendron is a prevalent woody plant used to combat desertification in the arid and semi-arid regions of northwestern China. Despite its drought resistance, artificial stands of this species experience significant degradation approximately ten years post-afforestation. Stumping, which involves cutting a portion of the above-ground part of shrubs/trees, is a common practice aimed at reducing water consumption and enhancing the growth of these stands. However, the impact of stumping on the sap flow of H. ammodendron remain inadequately understood, posing challenges to the sustainable management of these artificial stands. In this study, we monitored the sap flow of H. ammodendron subjected to various stumping treatments in the Ulan Buh Desert using the PS-TDP8 tree sap flow monitoring system. Concurrently, we measured several meteorological factors with an automatic weather station. We examined the changes in sap flow velocity following stumping and its response to meteorological factors to elucidate water use during growth. Our findings indicate that both the change in sap flow velocity and characteristics were closely associated with the degree of stumping. The initiation time of sap flow for H. ammodendron under different stumping treatments was earlier than that of the control group. The daily mean value and daily accumulation of sap flow followed the order: 50% stumping > control (no stumping) > 75% stumping > 100% stumping. Sap flow velocity and daily sap flow accumulation increased at 50% stumping but decreased at 75% and 100% stumping. Stumping altered the relationships between sap flow velocity and meteorological factors, with the correlation coefficient between these variables decreasing as the degree of stumping increased. The sap flow following stumping was primarily influenced by both the degree of stumping and meteorological factors. These results may contribute to a better understanding of water transport during the growth of H. ammodendron following stumping.

Exploring nanoparticle dynamics in binary chemical reactions within magnetized porous media: a computational analysis

Artificial Neural Networks are incredibly efficient at handling complicated and nonlinear mathematical problems, making them very useful for tackling these challenges. Artificial neural networks offer a special computational architecture that is extremely valuable in disciplines like biotechnology, biological computing, and computational fluid dynamics. The present work investigates the applicability of back-propagation artificial neural networks in conjunction with the Levenberg-Marquardt algorithm for evaluating heat transmission in hybrid nanofluids. This work focuses on the computational analysis of a MgO + GO/EG hybrid nanofluid’s steady mixed convection flow over an exponentially stretched sheet, considering multiple slip boundary conditions, thermal conductivity, heat generation, and thermal radiation. A nonlinear system of ordinary differential equations is produced from the basic associated partial differential system by performing the proper exponential similarities modifications. For generating benchmark datasets, the resulting ordinary differential equations are processed employing the bvp4c method. Considering benchmark datasets set aside for training (70%), testing (15%), and validation (15%), the Levenberg-Marquardt algorithm, which employs back-propagation in artificial neural networks, is implemented. The accuracy of the suggested strategy for handling nonlinear problems is verified utilizing mean squared error, error histograms, and regression analysis, which are all used to evaluate the methodology. Outstanding agreement is seen when ANN outputs are compared to numerical results. The flow properties, including temperature, velocity, and concentration profiles, are shown graphically and numerically. For practical purposes, it is therefore essential to analyze the flow and heat transfer in hybrid nanofluids over exponentially extending and shrinking surfaces under mixed convection and heat source scenarios. Hybrid nanofluid problems have a wide range of practical and industrial applications, such as medication delivery, manufacturing, microelectronics, nuclear plant cooling, and marine engineering.

Simulation study on the cavitation flow characteristics of liquid ammonia in the nozzle under high-pressure injection conditions

In this study, a non-isothermal compressible cavitating flow simulation model for liquid ammonia in high-pressure injector, accounting for the phase change properties, was established. The model was validated using experimental data from existing literature. The cavitation phase change process of liquid ammonia within the injector nozzle was investigated, and the differences in cavitation distribution between ammonia and diesel were explored. The results indicate that with increasing injection pressure, the vapor volume fraction of ammonia increases linearly, while that of diesel fuel shows a rapid initial rise followed by a decelerating trend. In terms of flow coefficient, ammonia is lower than diesel, though the two values converge at higher injection pressures. Under low injection pressure, the heat absorbed by the cavitation phase change of ammonia exceeded the heat generated by the high-speed friction of ammonia flow against the nozzle wall, leading to a temperature drop at the nozzle inlet. Conversely, at high injection pressure, the temperature of ammonia on the nozzle wall increases by more than 20 K, resulting in a rapid rise in saturated vapor pressure and significantly intensifying the cavitation effect. Compared to ammonia, diesel experienced a higher temperature rise within the nozzle but exhibited smaller variations in saturated vapor pressure, making the temperature effect on cavitation less pronounced. Diesel’s higher density and viscosity resulted in lower flow velocities compared to ammonia, leading to more developed cavitation in the lower wall region of the nozzle and creating a higher pressure region on the upper wall of the nozzle, which was more distant from the nozzle inlet and inhibited cavitation development there. The research results provide theoretical support for the design of liquid ammonia injectors.

A microwave discharge in high-velocity flows initiated by a half-wave antenna

A microwave discharge in high-velocity (150—250 m/s) air flows induced on a half-wave vibrator is studied. A cw magnetron microwave generator with a frequency of 2.45 GHz and an output power of up to 5 kW was used for initiation of the microwave discharge. The high-speed video imaging was used for studying the discharge structure, determining the diameter and length of the plasma channel as a function of flow velocity and pressure. Electron concentration and temperature, along with characteristic gas temperature, were determined based on the optical spectra. The possibility of using this microwave discharge for ignition of hydrocarbon–air mixtures in combustion chambers of ramjet engines is proved experimentally.

A novel model for low-permeability reservoir numerical simulation considering dynamic capillary force

ABSTRACT Capillary force is not only affected by water saturation but also affected by fluid flow velocity, which is necessary to modify the prior numerical simulation methods. First, a dynamic capillary force testing device was developed, then, an experimental procedure was adopted to measure the dynamic capillary force curve. Three dynamic capillary force curves were obtained under different displacement velocity conditions. Finally, the dynamic capillary force was introduced into the flow equation of low-permeability reservoir numerical simulation. The oil-phase equation and water-phase equation were discretized in three-dimensional space, and the IMPES method was used to solve the water saturation and pressure difference. The calculation results between the traditional numerical simulation method and the novel method under heterogeneous and inhomogeneous conditions were analyzed. The results reveal that the difference in water cut is mainly reflected in the rapid rise of water cut. In the early stage of rapid increase, the water cut calculated by the new method is slightly higher than traditional method. When the water cut is more than 65%, the water cut calculated by the new method is slightly lower than the traditional method.

Effects of pedicle subtraction osteotomy on aortic morphology and hemodynamics in ankylosing spondylitis with kyphosis: a finite element analysis study

Osteotomy can correct kyphosis, restore the spinal sequence, and restore the healthy appearance of a patient. However, the aorta is stretched during pedicle subtraction osteotomy (PSO), and some surgeons are concerned about aortic injury. We used finite element analysis to construct an aortic model to simulate hemodynamic changes during osteotomy. 16 patients with ankylosing spondylitis kyphosis who had undergone a two-level osteotomy at the L1 and L3 levels was included in this study. Aortic computed tomography angiography (CTA) was performed, and a 3D image model was constructed. The length, transverse diameter, and curvature of the aorta were used to evaluate morphological changes. Finite element analysis was used to analyze the changes in aortic fluid dynamics. Blood pressure, wall shear stress, and blood flow velocity were compared pre- and postoperatively. The overall length of the aorta before surgery was 424.3 ± 42.9 mm, and the overall length of the aorta after surgery was 436.2 ± 54.8 mm. The aortic curvature decreased from 0.27 ± 0.13 to 0.17 ± 0.09. The mean transverse diameter of the aorta did not change (19.3 ± 6.6 vs. 19.2 ± 7.4 mm, P > 0.05). The blood flow velocity (2.8 ± 1.1 vs. 1.5 ± 0.8 m/s, P < 0.05), blood pressure (6.6 ± 1.7 vs. 4.3 ± 1.2 Kpa, P < 0.05), and wall shear stress (47.6 ± 17.3 vs. 22.3 ± 8.6, P < 0.05) at the T10-L4 level decreased postoperatively. Changes in LL were significantly correlated with changes in ld, dc, blood flow velocity, blood pressure and wall shear stress (ld : r = 0.713, P < 0.001; dc: r = 0.626,P = 0.010; blood flow velocity: r= − 0.541, P = 0.041; blood pressure: r = − 0.601, P = 0.016; wall shear stress: r= − 0.594, P = 0.027). The aorta was stretched, and its curvature decreased. The mean transverse diameter of the aorta did not change. Blood flow velocity, blood pressure, and wall shear stress decreased after surgery. Our study provides hemodynamic support for the possible cardiovascular benefits of osteotomes.

Proposal for Low-Cost Optical Sensor for Measuring Flow Velocities in Aquatic Environments

The ocean, with its intricate processes, plays a pivotal role in shaping marine life, habitats, and the Earth’s climate. This study addresses issues such as beach erosion, the survival of propagules from species like Posidonia oceanica, and nutrient distribution. To tackle these challenges, we propose an innovative sensor that quantifies hydrodynamic velocity by measuring the output voltage derived from detecting changes in light absorption and scattering using LEDs and LDRs. Our results not only demonstrate the effectiveness of the sensor but also the accuracy of the processing algorithm. Notably, the blue LED exhibited the lowest mean relative error of 7.59% in freshwater, while the yellow LED was most precise in chlorophyll-containing water, with a mean relative error of 6.80%. In a runoff simulation, we observed similar velocities with the blue, green, and white LEDs, 6.89 cm/s, 6.99 cm/s, and 7.05 cm/s, respectively, for nearly identical time intervals. It is important to highlight that our proposed sensor is not only effective but also highly cost-efficient, representing less than 0.43% of the cost of a Nortek Vector 6 MHz and 0.18% of the Teledyne Workhorse II 300 kHz Marine. This makes it a key tool for managing marine ecosystems sustainably.

Lateral Shear Stress Calculation Model Based on Flow Velocity Field Distribution from Experimental Debris Flows

AbstractDebris flows continuously erode the channel downward and sideways during formation and development, which changes channel topography, enlarges debris flow extent, and increases the potential for downstream damage. Previous studies have focused on debris flow channel bed erosion, with relatively little research on lateral erosion, which greatly limits understanding of flow generation mechanisms and compromises calibration of engineering parameters for prevention and control. Sidewall resistance and sidewall shear stress are key to the study of lateral erosion, and the distribution of the flow field directly reflects sidewall resistance characteristics. Therefore, this study has focused on three aspects: flow field distribution, sidewall resistance, and sidewall shear stress. First, the flow velocity distribution and sidewall resistance were characterized using laboratory debris flow experiments, then a debris flow velocity distribution model was established, and a method for calculating sidewall resistance was developed based on models of flow velocity distribution and rheology. A calculation method for the sidewall shear stress of debris flow was then developed using the quantitative relationship between sidewall shear stress and sidewall resistance. Finally, the experiment was validated and supplemented through numerical simulations, enhancing the reliability and scientific validity of the research results. The study provides a theoretical basis for the calculation of the lateral erosion rate of debris flows.

The impact of early speech and language cognitive training care on the developmental quotient of children with language impairments: A retrospective study.

This study aims to investigate the effects of early speech and language cognitive training on the nursing outcomes of children with language impairments and their impact on developmental quotient. From October 2018 to October 2023, the data of 80 children with language impairments treated at our hospital were selected. They were divided into an observation group (n = 40) and a control group (n = 40) based on the treatment plan. The control group received routine rehabilitation training, while the observation group received early cognitive language rehabilitation training. The treatment efficacy of the 2 groups, as well as differences in Gesell Developmental Schedule scores and serum indicators before and after treatment, were observed and analyzed. The treatment efficacy in the observation group was superior to that in the control group (P < .05), with a total effective rate of 92.50% in the observation group. After 6 months of treatment, the scores for adaptability, gross motor skills, fine motor skills, personal-social behavior, and language development quotient in the observation group were (77.41 ± 10.21), (77.15 ± 10.43), (80.43 ± 11.19), (71.14 ± 10.42), and (81.21 ± 12.03), respectively, significantly higher than those in the control group (P < .05). After 6 months of treatment, the mental development index and psychomotor development index in the observation group were (107.28 ± 10.43) and (96.60 ± 9.03), respectively, which were markedly higher than those in the control group (P < .05). After 6 months of treatment, the serum levels of insulin-like growth factor-1, 25-hydroxyvitamin D [25(OH)D3], and gamma-aminobutyric acid in the observation group were (52.43 ± 9.44) ng/mL, (31.45 ± 4.82) ng/mL, and (76.65 ± 10.54) µmol/mL, respectively. These levels were not significantly different from those in the control group (P > .05). The blood flow velocities of the middle cerebral artery, anterior cerebral artery, basal artery, and vertebral artery in the observation group and control group were compared after 6 months of treatment (P > .05). Early speech and cognitive training have shown promising efficacy in the treatment of language disorders, as it can improve developmental quotient in affected children and increase serum levels of insulin-like growth factor-1, 25(OH)D3, and gamma-aminobutyric acid.

Non-Spherical Cavitation Bubbles: A Review

Cavitation is a phase-change phenomenon from the liquid to the gas phase due to an increased flow velocity. As it causes severe erosion and noise, it is harmful to hydraulic machinery such as pumps, valves, and screw propellers. However, it can be utilized for water treatment, in chemical reactors, and as a mechanical surface treatment, as radicals and impacts at the point of cavitation bubble collapse can be utilized. Mechanical surface treatment using cavitation impacts is called “cavitation peening”. Cavitation peening causes less pollution because it uses water to treat the mechanical surface. In addition, cavitation peening improves on traditional methods in terms of fatigue strength and the working life of parts in the automobile, aerospace, and medical fields. As cavitation bubbles are utilized in cavitation peening, the study of cavitation bubbles has significant value in improving this new technique. To achieve this, many numerical analyses combined with field experiments have been carried out to measure the stress caused by bubble collapse and rebound, especially when collapse occurs near a solid boundary. Understanding the mechanics of bubble collapse can help to avoid unnecessary surface damage, enabling more accurate surface preparation, and improving the stability of cavitation peening. The present study introduces three cavitation bubble types: single, cloud, and vortex cavitation bubbles. In addition, the critical parameters, governing equations, and high-speed camera images of these three cavitation bubble types are introduced to support a broader understanding of the collapse mechanism and characteristics of cavitation bubbles. Then, the results of the numerical and experimental analyses of non-spherical cavitation bubbles are summarized.

Modification of Additional Check Valves and Tube Pressure to Enhance Hydram Pump Capacity and Performance for Agricultural Applications

Pump that operates automatically by relying on natural power from water without using great cost and trouble by pumping hydram. Hydram pumps are one of the types of pumps that are driven by kinetic power, it was discovered by a 1796 Montgolfier in Italy. The purpose is to determine the most optimal water speed of the hydram pump by using different numbers of pressure tubes and several check valves. This research uses a factorial Randomised Group Design (RGD) method. The first treatment is valve variation and the second is variation in the number of tubes. The results showed that the average river water flow velocity was 0.154 meters/second with an average water discharge of 2.61 m3/second under normal flow conditions. The average water flow in the intake pipe is 0.717 meters / second and the volume of water in the pipe is 15.19 liters with an average water discharge entering the intake pipe is 10.804 m3 / second. A combination of three valves and three tube treatments consistently produces greater water discharge than other combinations. The highest efficiency of the hydram pump is found in the combination of three checks.

Effect of groove splint fixation on early swelling and blood flow velocity of the injury limb in elderly patients with distal radius fractures

To observe the effects of groove splint fixation on early hand swelling, blood flow velocity, and clinical function in elderly patients with distal radius fractures. Between March 2021 and February 2022, 64 patients of unilateral closed distal radius fractures were treated with manual reduction and external fixation with splints. There were 10 males and 54 females, the age ranged from 60 to 78 years old, with an average age of (67.7±4.7) years old. According to the order of admission, the patients were divided into the groove splint group and the conventional splint group, with 32 cases in each group. In the groove splint group, there were 4 males and 28 females, with an average age of (68.6±4.8) years old. There were 13 patients with left-sided fractures, and 19 patients with right-sided fractures, with 22 cases classified as AO type A and 10 cases as AO type C. The mean time from injury to treatment was 3.0 (2.0, 4.0) h. In the conventional splint group, there were 6 males and 26 females, with an average age of (66.9 ± 4.4) years old. There were 17 patients with left-sided fractures and 15 patients with right-sided fractures, with 20 cases classified as AO type A and 12 cases as AO type C. The mean time from injury to treatment was 3.0 (2.0, 5.0) h. After manual reduction, patients were treated with groove splint or conventional splint. Swelling, assessed by the difference in limb circumference between the injured and healthy limbs, was measured at 1, 3, 7, and 14 days post-treatment. Blood flow velocities in the superficial palmar arch and dorsal metacarpal veins were measured at 1, 3, and 7 days post-treatment. Radiographic evaluations of radial styloid height, palmar tilt, and ulnar variance were performed preoperatively and 3 months post-treatment. Functional outcomes were assessed using the DASH (Disabilities of the Arm, Shoulder, and Hand) score 3 and 12 months post-treatment. Statistical analyses were conducted to compare the outcomes between the two groups. All 64 patients were followed up for the least 12 months. The swelling value of the palm in the groove splint group [(1.897±0.071) cm, (1.200±0.169) cm, (0.994±0.085) cm] was significantly improved compared to the conventional splint group[(2.283±0.268) cm, (1.893±0.269) cm, (1.183±0.126) cm] on days 3, 7, and 14 days posttreatment, with a statistically significant difference (P<0.001). On the first and third day after splint fixation, the difference in blood flow velocity of the superficial palmar arch in the groove splint group(0.017±0.009), (0.018±0.011) L·min-1 were lower than that in the conventional splint group(0.023±0.011), (0.025±0.013) L·min-1, with statistical significance (P<0.05). On the 3rd and 7th days, the difference was not statistically significant (P>0.05). Comparison of blood flow velocity differences between the dorsal metacarpal vein and the two groups showed no statistically significant difference on the first day after splint fixation (P>0.05). On the 3rd and 7th days, the blood flow velocity difference between the groove splint group[(0.037±0.019), (0.021±0.013) L·min-1] decreased compared to the conventional splint group[(0.062±0.033), (0.037±0.022) L·min-1], and the difference was statistically significant (P<0.05). There was no statistically significant difference in the palm angle, ulnar deviation angle, and radius height of the distal radius before and after reduction (P>0.05). The DASH score showed a statistically significant difference at follow-up 3-month[(6.1±2.8) scores vs (8.2±3.7) scores] , P<0.05, but no statistically significant difference at follow-up 12-month (P>0.05). Fixing distal radius fractures with groove splints in the early stage can reduce the impact on the blood flow velocity of the superficial palmar arch and dorsal palmar vein, reduce venous reflux obstruction and swelling of injury limb, alleviate wrist and finger joint stiffness, and improve early clinical efficacy of the affected limb. However, it has no significant impact on clinical function one year after injury.

Evaluation of an Unsteady Yaw, Gust, and Broadband Turbulence Generation System for Closed-Loop Automotive Wind Tunnels

&lt;div&gt;This study investigates the flow characteristics in the test section of a model-scale, three-quarters open-jet, closed-loop return wind tunnel equipped with a novel device featuring three subsystems to generate transient yaw, gusts, and turbulence. The effect of each subsystem on the resulting turbulent and unsteady flows is evaluated individually and simultaneously. It is demonstrated that this new turbulence generation system can generate yaw distributions with standard deviations ranging from 2.1° to 8.0°. This replicates a wide range of on-road yaw behavior. Additionally, the subsystems can activate transient yaw events and unsteady gusts. Frequency sweeping was demonstrated to fill a wide range of low-frequency spectra, which helps recreate the on-road flow spectra in wind tunnels. Unsteady gusts of more than 15% of the mean flow velocity were achieved. The active turbulence subsystem generates turbulence levels from a few percent, passively, to over 20% intensity levels actively, with tailorable levels depending on input parameters to the active grid. Combined, the subsystems were demonstrated to achieve a wide range of yaw distributions with different standard deviations and features of the on-road turbulence spectrum, from low-frequency events to broadband turbulence with significant inertial subrange within the model-scale wind tunnel.&lt;/div&gt;

Comprehensive validation of a compact laser speckle contrast imaging system for vascular function assessment: from the laboratory to the clinic.

Proper organ functioning relies on adequate blood circulation; thus, monitoring blood flow is crucial for early disease diagnosis. Laser speckle contrast imaging (LSCI) is a noninvasive technique that is widely used for measuring superficial blood flow. In this study, we developed a portable LSCI system using an 805-nm near-infrared laser and a monochrome CMOS camera with a 10 × macro zoom lens. The system achieved a high-resolution imaging (1280 × 1024 pixels) with a working distance of 10 to 35 cm. The relative flow velocities were visualized via a spatial speckle contrast analysis algorithm with a 5 × 5 sliding window. In vitro experiments demonstrated the system's ability to image flow velocities in a fluid model, and a linear relationship was observed between the actual flow rate and the relative flow rate obtained by the system. The correlation coefficient (R2) exceeded 0.83 for volumetric flow rates of 0 to 0.2 ml/min when channel widths were greater than 1.2 mm, and R2 > 0.94 was obtained for channel widths exceeding 1.6 mm. Comparisons with laser Doppler flowmetry (LDF) revealed a strong positive correlation between the LSCI and LDF results. In vivo experiments captured postocclusive reactive hyperemic responses in rat hind limbs and human palms and feet. The main research contribution is the development of this compact and portable LSCI device, as well as the validation of its reliability and convenience in various scenarios and environments. Future applications of this technology include evaluating blood flow changes during skin injuries, such as abrasions, burns, and diabetic foot ulcers, to aid medical institutions in treatment optimization and to reduce treatment duration.