Deceleration Zone Research Articles

High-density Grid Mapping Catheter Unveiled a Deceleration Zone in a Large Ventricular Scar.

High-density Grid Mapping Catheter Unveiled a Deceleration Zone in a Large Ventricular Scar.

Channel width, bedform length and turbulence: numerical investigation of flow dynamics over laboratory-scale pool–riffle sequences

Spatial dimensions of bedforms relative to the flow depth are of great interest for both engineers and geoscientists, and continue to be an active area of research. These morphological features are of significant consequence for critical hydrodynamic parameters, which in turn has an impact on sediment and solute transport through the river system. In this study, we present results from three-dimensional large eddy simulation of flows over such bedforms in a straight channel. Rigid three-dimensional pool–riffle structures occupying the full span of the channel were considered as the macro-bedforms. The presence of pool–riffle affects the spatial heterogeneity of the flow parameters such as lateral flow concentration. We observed that the lateral flow concentration increases in convective deceleration (CDF) zone with peak values at the central plane in channels with narrower span. The peak values shift from the central plane towards sidewall in channels with larger width. Flow recovery is found to be faster in narrower channels in the conducted simulations. High-magnitude counter-rotating vortices (HCRVs) in CDF and pool transport the momentum of the flow towards the centre of the channel. Larger channel width ensures persistent presence of HCRV in CDF and pool. Longer riffle length in the streamwise direction is observed to further alter the lateral flow concentration compared to the shorter riffles. Instantaneous bed shear stress mapping reveals the presence of coherent high- and low-velocity streaks on riffles. The coherence of these structures is lost in CDF and pool accompanied with an increase in turbulence represented by an increase in turbulent kinetic energy and Reynolds stress.

Influence of airflow dynamics on vortices in the human nasal cavity

Purpose The purpose of this paper is to understand the effect of airflow dynamics on vortices for different flow rates using the human nose three-dimensional model. Design/methodology/approach Olfaction originates with air particles travelling from an external environment to the upper segment of the human nose. This phenomenon is generally understood by using the nasal airflow dynamics, which enhances the olfaction by creating the vortices in the human nose. An anatomical three-dimensional model of the human nasal cavity from computed tomography (CT) scan images using the MIMICS software (Materialise, USA) was developed in this study. Grid independence test was performed through volume flow rate, pressure drop from nostrils and septum and average velocity near the nasal valve region using a four computational mesh model. Computational fluid dynamics (CFD) was used to examine the flow pattern and influence of airflow dynamics on vortices in the nasal cavity. Numerical simulations were conducted for the flow rates of 7.5, 10, 15 and 20 L/min using numerical finite volume methods. Findings At coronal cross-sections, dissimilar nasal airflow patterns were observed for 7.5, 10, 15 and 20 L/min rate of fluid flow in the human nasal cavity. Vortices that are found at the boundaries with minimum velocity creates deceleration zone in the nose vestibule region, which is accompanied by flow segregation. Maximum vortices were observed in the nasal valve region and the posterior end of the turbinate region, which involves mixing and recirculation and is responsible for enhancing the smelling process. Practical implications The proposed analysis is applicable to design the sensor chamber for electronic noses. Originality/value In this paper, the influence of airflow dynamics on vortices in the human nasal cavity is discussed through numerical simulations.

Substrate Mapping in Ventricular Arrhythmias.

Ventricular tachycardia is typically hemodynamically unstable. Strategies to target the arrhythmogenic substrate during sinus rhythm are essential for therapeutic ablation. Electroanatomic mapping is the cornerstone of substrate-based strategies; ablation can be directed within a delineated scar region defined by low voltage. Bipolar voltage mapping has inherent limitations. Specific electrogram characteristics may improve the specificity of localizing the most arrhythmogenic regions within the substrate. Deceleration zones during sinus rhythm are niduses for reentry and can be identified by isochronal late activation mapping, which is a functional analysis of substrate propagation with local annotation to electrogram offset.

Targeted Ablation of Ventricular Tachycardia Guided by Wavefront Discontinuities During Sinus Rhythm

Accurate and expedited identification of scar regions most prone to reentry is needed to guide ventricular tachycardia (VT) ablation. We aimed to prospectively assess outcomes of VT ablation guided primarily by the targeting of deceleration zones (DZ) identified by propagational analysis of ventricular activation during sinus rhythm. Patients with scar-related VT were prospectively enrolled in the University of Chicago VT Ablation Registry between 2016 and 2018. Isochronal late activation maps annotated to the latest local electrogram deflection were created with high-density multielectrode mapping catheters. Targeted ablation of DZ (>3 isochrones within 1cm radius) was performed, prioritizing later activated regions with maximal isochronal crowding. When possible, activation mapping of VT was performed, and successful ablation sites were compared with DZ locations for mechanistic correlation. Patients were prospectively followed for VT recurrence and mortality. One hundred twenty patients (median age 65 years [59-71], 15% female, 50% nonischemic, median ejection fraction 31%) underwent 144 ablation procedures for scar-related VT. 57% of patients had previous ablation and epicardial access was employed in 59% of cases. High-density mapping during baseline rhythm was performed (2518 points [1615-3752] endocardial, 5049±2580 points epicardial) and identified an average of 2±1 DZ, which colocalized to successful termination sites in 95% of cases. The median total radiofrequency application duration was 29 min (21-38 min) to target DZ, representing ablation of 18% of the low-voltage area. At 12±10 months, 70% freedom from VT recurrence (80% in ischemic cardiomyopathy and 63% in nonischemic cardiomyopathy) was achieved. The overall survival rate was 87%. A novel voltage-independent high-density mapping display can identify the functional substrate for VT during sinus rhythm and guide targeted ablation, obviating the need for extensive radiofrequency delivery. Regions with isochronal crowding during the baseline rhythm were predictive of VT termination sites, providing mechanistic evidence that deceleration zones are highly arrhythmogenic, functioning as niduses for reentry.

Gait Speed Measurement using a Doppler Radar Sensor for In-Home Functional Capacity Tests.

Gait speed is a simple physical function measure associated with key outcomes in the elderly population. Several tests are realized in order to assess the functional capacity of people. For an in-home monitoring of the functional capacity, we propose to use a Doppler radar sensor in order to continuously measure the gait speed of elderly people. We discuss at first how the gait speed is evaluated using the Doppler radar. We note three different phases in the gait speed, namely an acceleration zone, a measured-gait zone, and a deceleration zone. We thus provide a segmentation of the walking in order to automatically distinguish these zones. Experiments are conducted on ten subjects with three different paces in a total of 180 walking patterns. The gait speed obtained by the radar sensor is validated using a Vicon motion-capture system, with a correlation equal to 0.9788. We report an enhancement of 20% in measuring the gait speed as compared to traditional techniques, while removing the need for acceleration and deceleration zones.

Laser Doppler Velocimetry (LDV) measurements of airfoil surface flow on a Horizontal Axis Wind Turbine in boundary layer

This study investigated the flow characteristics of a Horizontal Axis Wind Turbine (HAWT) rotor surface during rotation with wind tunnel experiments. Firstly, the effect of Laser Doppler Velocimetry (LDV) system on the power coefficient of HAWT was measured. Then, the flow distributions near the blade surface were measured at the different radial positions (r/R = 0.3 and 0.7) in the cases of the low and optimal tip speed ratios. At last, the radial position effect on the flow field features in boundary layer were also investigated in detail. As a result, the boundary layer thickness decreased at the blade leading edge and then increased rapidly along the blade surface at the trailing edge region. Furthermore, in the case of r/R = 0.7, the two-dimensional resultant velocity in the acceleration region of boundary layer showed smaller value than that of r/R = 0.3. Meanwhile, the flow in the blade root showed a large expansion of the deceleration zone at the low tip speed ratio. The results acquired from this study was suitable for designing the airfoil and had a better understanding of the radial position effect on dynamic stall.

Can a Field Based Neuromuscular Test Determine Readiness to Train in Female Team Sport Athletes?

PURPOSE: To determine if a field-based neuromuscular test (Counter Movement Jump (CMJ)) could accurately detect EIMD-related performance decrements incurred by repeated sprinting in female team sport athletes. METHODS: 10 female athletes (Age: 21.7 ± 2.5y) performed an eccentrically-biased, repeated sprint protocol consisting of 5 sets of 8 maximal sprint (MS) trials (20m in length, 5m deceleration zones). Participants then immediately performed three CMJs on a force plate (FD4000, NMP ForceDecks Ltd, UK) to assess fatigue before beginning the next set of 8 sprints. Blood lactate and RPE were assessed following the completion of the sprint protocol. After 24-48h, participants returned to complete soreness ratings, 3 CMJs and 3 MSs. This process was completed 4 times (each “Trial” = 1 repeated sprint protocol visit + 1 24-28h follow up visit). RESULTS: A number of CMJ metrics were significantly lower (p<0.05) when measured during the 24-48h follow up visits, however the only one that was consistently lower across all 4 trials was concentric RFD (N/s/kg) (Pre v 24-48h post: Trial 1 = 36.03 ± 16.81 v 20.64 ± 13.49; Trial 2 = 49.37 ± 32.29 v 29.44 ± 21.87; Trial 3 = 50.45 ± 40.86 v 27.59 ± 24.43; Trial 4 = 43.87 ±32.37 v 31.01 ± 29.41). No significant differences (p>0.05) were found for peak or average velocity during the MSs across any trial. Lower body soreness was significantly greater (p<0.05) during the 24-48h follow up visits as assessed via a 0-10 visual analogue scale. The sprint protocol induced a high internal physiological load, evidenced by significantly elevated post-exercise blood lactate levels (pre: 1.51±0.50 vs post: 5.6±2.53). CONCLUSION: Concentric RFD determined using a CMJ was the best metric for detecting performance impairments, as it consistently declined 24-48h after completing a repeated sprint protocol. The other CMJ metrics, as well as MS performance did not decrease across all trials. A CMJ test that assesses concentric RFD may be a useful tool for coaches to determine readiness to train in female athletes. Future research should seek to replicate this protocol using higher sprinting volumes, to determine whether concentric RFD declines in a predictable dose-response manner. Limitations of this study were the small sample size and the lack of control for external damaging activity (i.e. rugby training).

Investigations into Mining-Induced Stress–Fracture–Seepage Field Coupling Effect Considering the Response of Key Stratum and Composite Aquifer

The effect of mining-induced stress–fracture–seepage field coupling (SFSC) is critical to the safety and productivity of the underground mining. This study investigated the spatiotemporal effect of SFSC at the Bulianta Colliery panel #31401 of the Shendong coalfield in China, characterized by ladder key stratum and composite aquifer. An integrated method including borehole and working face observation, in-site water leakage, and real-time video imaging was adopted to examine the behavior of overburden movement, water level change, and groundwater inrush. Simultaneously, the evolution of the SFSC was visualized by the FLAC3D–CFD (fluent) simulator with a developed non-Darcy model, and the dynamic characteristics of the SFSC were analyzed. The results indicated that the macro-stress shell, fractured field distributed beneath the macro-stress shell with a 48 m height difference in the lower and higher key stratum zone, and seepage field including initiation zone, acceleration zone, deceleration zone, and drainage zone were identified. The confined aquifer was affected by the fracture field with a height of 140–154 m, and groundwater invasion was triggered and developed beneath the lower key stratum. The confined aquifer was kept stable by protection of the higher key stratum by controlling the propagation of the fracture field at the height of 90–100 m. Highly permeable channels were distributed beneath the micro-stress shell as a result of the release of in-site stress, especially at the rupture region of the micro-stress shell between the lower and higher key stratum, with the maximum fluid discharge. Furthermore, the SFSC response resulted in large and medium groundwater invasion and strong variation of abutment stress peak, when creating rupture at the micro-stress shell and main roof. Finally, based on the mechanism of the SFSC, the developed optimization strategy could efficiently mediate the effect of the SFSC by lowering the mining height, increasing the advance rate, and enhancing the support resistance of the longwall mining face.

Estimating Regional Shadow Prices of CO2 in China: A Directional Environmental Production Frontier Approach

Shadow price of carbon dioxide (CO2) plays a fundamental role in evaluating CO2 abatement cost and formulating regional environmental policies. In this study, CO2 shadow prices are estimated in 29 provinces of China from 2006 to 2015. Directional Environmental Production Frontier Function (DEPFF) measures the distance between actual production points and the effective production frontier surface, which yields the shadow prices of CO2 emission. With the relationship between CO2 emission and Gross Domestic Product (GDP) growth which is encapsulated in the shadow price, the provinces are classified into three groups: acceleration zone, buffer zone, and deceleration zone. The acceleration zone is characterized by a smaller emission growth driving a greater economic growth, and the provincial average price of CO2 is 184.16 US$/ton. In the buffer zone, a significant emission increase brings about less economic growth with the average shadow price at 86.57 US$/ton. In the deceleration zone, a high growth rate of CO2 emissions is accompanied with an economic output decrease, which implies that the shadow price of CO2 should be negative, and the mean value is −200.7 US$/ton. As the CO2 abatement potential differs significantly across provinces, the environmental policy and CO2 reduction targets should be region-specific.

Near Time-Optimal &lt;italic&gt;S&lt;/italic&gt;-Curve Velocity Planning for Multiple Line Segments Under Axis Constraints

To drive the machine tool along a curve, a commercial computer-aid design and computer-aided manufacturing system usually breaks the curve into a set of line segments. This paper provides a systematic way for generating smooth and fast machining velocity planning for contouring line segments in a machine tool. It is especially useful for mass manufacturing. In this paper, the particle swarm optimization algorithm is employed to optimize the design parameters. The algorithm allows for as many motion limits as possible, not only the limits along the path, but those on the axes, as well. It can automatically determine the existence of acceleration, constant speed, and deceleration zones of the S -curve velocity profile. Also, it can determine the optimal corner speed with a given corner error. The computation time of the algorithm is fast so that it allows for online operation. Simulation and experimental results demonstrate that machine tools using the proposed algorithm go fast where possible and slow down where needed, dramatically increasing the productivity.

Anisotropic Properties of Blood in a Vessel with Stenosis

Preferential orientation of erythrocytes along the flow lines in the vertical plane was observed in the acceleration zone at the entry to the narrow part of the cell and inside this part when whole blood flow in a canal with stenosis was analyzed. An area where the erythrocyte orientation changed was observed in the deceleration zone; erythrocytes assumed an orientation perpendicular to the flow lines in the vertical plane after they passed through this zone. The flow of erythrocytes at a concentration of 1 vol % was studied under the same hydrodynamic conditions in order to characterize the behavior of individual erythrocytes.

Driving Risk Detection Model of Deceleration Zone in Expressway Based on Generalized Regression Neural Network

Drivers’ mistakes may cause some traffic accidents, and such accidents can be avoided if prompt advice could be given to drivers. So, how to detect driving risk is the key factor. Firstly, the selected parameters of vehicle movement are reaction time, acceleration, initial speed, final speed, and velocity difference. The ANOVA results show that the velocity difference is not significant in different driving states, and the other four parameters can be used as input variables of neural network models in deceleration zone of expressway, which have fifteen different combinations. Then, the detection model results indicate that the prediction accuracy rate of testing set is up to 86.4%. An interesting finding is that the number of input variables is positively correlated with the prediction accuracy rate. By applying the method, the dangerous state of vehicles could be released through mobile internet as well as drivers' start of risky behaviors, such as fatigue driving, drunk driving, speeding driving, and distracted driving. Numerical analyses have been conducted to determine the conditions required for implementing this detection method. Furthermore, the empirical results of the present study have important implications for the reduction of crashes.

Laser shock peening induced fatigue crack retardation in Ti-17 titanium alloy

Laser shock peening is an advanced surface treatment technique of great interest introducing beneficial compressive residual stress and further enhancing fatigue crack propagation resistance of metallic components. In this study, fatigue crack propagation and subsequent retardation of Ti-17 titanium alloy under laser shock peening are presented. Varying degrees of fatigue crack retardation were observed after peening with pulse energy of 20 J and 30 J. The fatigue life was increased up to 2.4 times that of the unpeened counterpart. The fatigue arrests were observed in the deceleration zone after peening, showing different angles with the fatigue crack path as the peening energy varied. The fatigue crack retardation mechanism based on the plastic zone size and crack propagation energy density drop at the crack tip was further discussed, and a crack tip energy density criterion was proposed to quantitatively understand the fatigue crack retardation.

Computational Study of Partially Covered Hartmann Whistle in a Sonic-Underexpanded Jet

The present study investigates the use of Hartmann whistle as an effective passive flow control device by partially covering the entire area between the jet exit and cavity inlet using a cylindrical shield, numerically. The passive flow control is accomplished by allowing the pulsating jet to exit through two small openings in the shield: (i) near the cavity inlet, (ii) away from the cavity inlet. The studies are performed for various S/Dj values of 1.43, 2.86 and 4.28, (where S is the stand-off distance and Dj is the jet diameter). The velocity vectors indicate the jet regurgitance showing inflow/outflow phases as well as flow diversion features near the cavity mouth. The Mach contours show shock-structures as well as the flow deceleration and re-acceleration zones. It shows that the resonant oscillations are primarily driven by jet regurgitance at smaller stand-off distances but at higher stand-off distances they are mainly driven by fluid column oscillations in the shock cells, shield, as well as in the cavity regions. It also shows that the stand-off distance is a key parameter that controls the strength of shock as well as regurgitant/fluid column, oscillations. An empirical formula developed using dimensional analysis reveals that the resonance frequency of the partially covered Hartmann whistles can be obtained using the classical Helmholtz resonator analogy with the stagnation sound speed, size of the flow control openings, shield height, stand-off distance and cavity length as parameters. Thus, this paper adequately illustrates the effect of stand-off distance as well as flow control openings in modifying the shock as well as regurgitant/fluid column, oscillations in a partially covered Hartmann whistle for attaining the effective flow control .

Automated isochronal late activation mapping to identify deceleration zones: Rationale and methodology of a practical electroanatomic mapping approach for ventricular tachycardia ablation

Sinus rhythm surrogates for critical isthmus sites are highly desirable because the vast majority of VT is hemodynamically unstable. While many ablation strategies to decrease the arrhythmogenicity of scar have been shown to be effective, the predominant method for electroanatomic mapping relies on a voltage-based depiction of scar and abnormal electrograms. A functional prioritization of slow conduction, distinct from late activation, is feasible in clinical practice with the creation of isochronal late activation maps. Regions of slow conduction are easily visualized with isochronal displays of baseline intrinsic rhythm activation and deceleration zones, where isochrones crowd, have been observed to have strong correlation with successful ablation sites. Automated annotation of the offset of local electrograms was developed to create the propagation maps to incorporate electrogram width and completion of local activation. Simple conduction velocity estimates where three isochrones are seen within a 1 cm radium confirm that deceleration zones harbor conduction velocity of <0.6 m/s. We present a practical methodology of analyzing electroanatomic substrate in a voltage-independent manner with correlation to reentrant VT. Non-linear 3D transmyocardial conduction limits the validity of conduction velocity estimates that assume planar and tangential conduction and we show an example of a patient with 3D isthmus boundaries with an activation gap on the epicardial surface during tachycardia.

Year in Review in Cardiac Electrophysiology.

In the past year, there have been numerous advances in our understanding of arrhythmia mechanisms, diagnosis, and new therapies. We have seen advances in basic cardiac electrophysiology with data suggesting that secretoneurin may be a biomarker for patients at risk of ventricular arrhythmias, and we have learned of the potential role of an NPR-C (natriuretic peptide receptor-C) in atrial fibrosis and the role of an atrial specific 2-pore potassium channel TASK-1 as a therapeutic target for atrial fibrillation. We have seen studies demonstrating the role of sensory neurons in sleep apnea-related atrial fibrillation and the association between bariatric surgery and atrial fibrillation ablation outcomes. Artificial intelligence applied to electrocardiography has yielded estimates of age, sex, and overall health. We have seen new tools for collection of patient-centered outcomes following catheter ablation. There have been significant advances in the ability to identify ventricular tachycardia termination sites through high-density mapping of deceleration zones. We have learned that right ventricular dysfunction may be a predictor of survival benefit after implantable cardioverter-defibrillator implantation in patients with nonischemic cardiomyopathy. We have seen further insights into the role of His bundle pacing on improving outcomes. As our understanding of cardiac laminopathies advances, we may have new tools to predict arrhythmic event rates in gene carriers. Finally, we have seen numerous advances in the treatment of arrhythmias in patients with congenital heart disease.

Shelter effect efficacy of sand fences: A comparison of systems in a wind tunnel

Abstract The Lanzhou-Xinjiang High-speed Railway runs through an expansive wind area in the Gobi Desert and blown-sand disasters are a critical issue affecting its operation. To strengthen the blown-sand disaster shelter systems along the railway, the shelter effects of punching plate and wire mesh fences with approximately equal porosity (48%) were simulated in a wind tunnel. The experimental results showed that the wind velocity was reduced to a higher extent by the punching plate fence than by the wire mesh fence. When a single row of sand fencing was used, the wind velocity reduction coefficient (Rcz) values downwind of the punching plate fence and wire mesh fence reached 71.77% and 39.37%, respectively. When double rows of sand fencing were used, the Rcz values downwind of the punching plate and wire mesh fences were approximately 87.48% and 60.81%, respectively. For the flow field structure on the leeward side of the fencing, the deceleration zone behind the punching plate fence was more pronounced than that behind the wire mesh fence. The vortex zone was not obvious and the reverse flow disappeared for both types of fences, which indicates that the turbulent intensity was small. The sand-trapping efficiency of the wire mesh fence was close to that of punching plate fence. When a single row of sand fencing was set up, the total mass flux density decreased, on average, by 65.85% downwind of the wire mesh fence, and 75.06% downwind of the punching plate fence; when double rows of sand fencing were present, the total mass flux density decreased, on average, by 84.53% downwind of the wire mesh fence and 84.51% downwind of the punching plate fence. In addition, the wind-proof efficiency and the sand-proof efficiency of the punching plate fence and the wire mesh fence decreased with increasing wind velocities. Consequently, punching plate and wire mesh fences may effectively control the sand hazard in the expansive wind area of the Gobi Desert.

Airflow and sediment movement within an inland blowout in Hulun Buir sandy grassland, Inner Mongolia, China

Abstract We measured wind flows and sediment transport rates through a blowout in Hulun Buir grassland, Inner Mongolia. Topography and the angle of incidence between the approaching wind and the blowout long-axis significantly affected the air flow. Flow separated and decelerated at the western wall and accelerated towards the east, until maximum wind speed occurred at the top of the depositional lobe, and then decelerated on the lee side. When airflow emerged on the eastern wall, resultant directions were always NW. When winds approached from directions within 17.5° of the blowout axis, both the northwestern and southwestern walls developed turbulent flow, and significant topographic steering occurred. The deceleration zone expanded eastwards from 10.3 to 12.8 m from the western rim. When the wind direction was more oblique than 17.5°, turbulent flow at the southwestern wall disappeared. ‘S-shaped’ flow intensified, causing more pronounced steering at the bottom, but topographic steering elsewhere was reduced, and the boundary of the deceleration moved to 10 m from the western rim. Minor sediment deposition occurred on the western wall, while other parts were eroded; maximum sediment transport occurred at the top of the depositional lobe. The approaching wind speed affected the sediment transport rate more than the direction; and spatial variability in sediment transport reflected differences in compaction, vegetation coverage, slope, aspect, and upwind sediment availability, resulting in asymmetrical development. Overall, flow-form interactions governed the flow structures and controlled the evolution of the blowout via sediment transport.

Influence of Types of Steel Poles on Measurements by Wind Speed Sensors along High-Speed Railways

To find the influence of different types of steel poles on measurements by wind speed sensors along highspeed railways, the three-dimensional Reynolds-averaged Navier-Stokes equations, combined with the k-e turbulence model, were solved on an unstructured grid with a boundary layer using the finite volume method. The grid-independent validation was firstly conducted, and the accuracy of the present numerical simulation method was validated by experiments and simulations carried out by previous researchers. To ascertain angles of influence at different distances between the sensor and the virtual one, the flow field around a sensor was investigated with the method of altering the relative coordinates between the two sensors. After that, the flow fields and velocity distributions around steel poles were studied. It can be stated that behind the sensor, the closer the distance from the sensor center line, the larger the angle of influence. However, as the distance is varied from 0.3 to 1.0 m, the most adverse angles are not in excess of ±20°. In addition, the steel poles have a certain influence on the measurement results of sensors. A “two-sided petal acceleration region” with a “central pistil deceleration zone” comes into being. From the perspective of regions of influence in different wind directions, the influence region of the annulus pole is basically the same. For the square and H types, when the angle is 45°, the region of effect is the largest. For the same distance between the sensor and the pole, the space required between two sensors for the single H type is larger than that required by the annulus type. Thus, it is suggested that the distance between sensors and the pole should be 1.0 m with the anemometer located on the upstream side, and the distance between two anemometers should be 0.8 m.