Peak Kinetic Energy Research Articles

Preliminary Investigation of the Spatial-Temporal Characteristics and Vertical Dynamics of Internal Solitary Waves in the South China Sea from SWOT Data

Internal waves are crucial for understanding oceanographic parameters such as spatiotemporal distribution and energy transfer. They significantly impact ocean circulation, marine ecosystems, and offshore operations. However, studying internal waves is challenging due to their dynamic nature and the need for effective observation methods. This study investigated nonlinear internal solitary waves (ISWs) in the South China Sea using SSHa data from the SWOT satellite mission (Cycles 2 to 20). The distribution patterns and seasonal variations in ISWs were analyzed, revealing that ISWs are more frequently observed in summer while being rarely detected in winter. By combining SSHa observations with a Mode-1 vertical structure model, the isopycnal displacement, velocity fields, and energy characteristics of ISWs were reconstructed. The results show a maximum isopycnal displacement of 160 m at 400 m depth and peak kinetic energy near the surface (~2000 J/m3) and potential energy at a depth of around 300 m (~9000 J/m3). These findings highlight the vertical variability of ISWs and demonstrate the capability of SWOT data in capturing their fine-scale evolution, providing new opportunities for oceanic research and enhancing our understanding of internal waves’ impact on marine environments and ocean circulation.

Enhanced Biomass Combustion via Bluff Body- and Impingement-Stabilized Natural Gas-Air Premixed Flames

ABSTRACT The preheating, flow recirculation and impingement effects of trapezoidal bluff bodies increased the biomass heating value-based combustion efficiency to 94% at a firing intensity of 78 MW/m3. A sawdust-laden air stream was combined to bluff body-stabilized natural gas-air premixed flames in three different configurations. A common impingement of opposing fuel-lean mixture jets with a sawdust-laden air cross-flow upstream of a solid bluff body provided a peak turbulent kinetic energy of 11.8 m2/s2. Using opposing jets with ports of multiple sharp corners minimized the flame length/combustor diameter ratio to 4.2. The combination of premixed flame impingement on the combustor base with the flow stagnation effect inside hollow bluff bodies provided a maximum blow-off velocity of 19.5 m/s at Ф = 0.8. Delaying the biomass interaction with the premixed flames decreased the peak exhaust NOx concentration to 0.17 g/kW.hr. Confronting the premixed flame jets by the sawdust-air laden jet provided a superior flow configuration in which the premixed flame high temperatures provided effective tar cracking, thus minimizing the exhaust total tar content to 50 mg/Nm3. A simultaneous peak exhaust soot volume fraction of 7 × 10−8 and a peak exhaust CH4 concentration of 0.1% were thus combined to a peak CO concentration of 14 mg/MJ.

Feasibility of 4D-flow CMR for haemodynamic characterization in hypertrophic cardiomyopathy after septal myectomy with and without anterior mitral valve leaflet extension.

The common surgical treatment in patients with obstructive hypertrophic cardiomyopathy is septal myectomy. This involves resection of a segment of the myocardial septum and can be performed with and without concomitant anterior mitral valve leaflet extension (AMVLE). While both approaches have satisfying clinical outcomes, there is a lack of data regarding the added value of concomitant AMVLE. In particular, their impact on postoperative haemodynamics remains unexplored. Therefore, we conducted a study to assess the feasibility of utilizing four-dimensional-flow cardiac magnetic resonance imaging (4D-flow cardiac magnetic resonance imaging (CMR)) to investigate postoperative haemodynamic differences among both surgical approaches. In this feasibility study, nine subjects underwent 4D-flow CMR evaluation, including three patients who underwent isolated myectomy, three patients with myectomy + AMVLE and three healthy controls. Primary end-points were aortic wall shear stress, left ventricular outflow tract (LVOT) peak velocity and peak kinetic energy in the LVOT and ascending aorta. Results showed that patients who underwent myectomy with concomitant AMVLE exhibited (i) lower aortic wall shear stress (-21.2%), (ii) lower LVOT peak velocity (-6.3%), (iii) higher kinetic energy in the LVOT (+10.8%) and (iv) lower kinetic energy in the ascending aorta (-28.8%) compared to patients who underwent isolated myectomy. Patients undergoing additional AMVLE exhibited a better trend towards the haemodynamic reference values from healthy controls compared to patients undergoing isolated myectomy. Our findings underscore the feasibility of 4D-flow CMR to assess postoperative haemodynamic differences in hypertrophic cardiomyopathy patients undergoing different surgical approaches. This highlights the potential of 4D-flow CMR to compare surgical strategies based on postoperative haemodynamics. Dutch National Medical Ethics Committee, registration number 2022.0078.

Dynamic behavior analysis of steel, aluminum, and composite plates under extreme air blast loadings

The number of terrorist air blast attacks is increasing in a catastrophic way in the current era. However, the selection of material is a crucial task for designing a high-blast-mitigating protective structure. The experimental evaluation of the dynamic responses of various materials under a blast event is highly costly, with many restrictions and environmental pollution. Therefore, to avoid these difficulties, the current study demonstrated a series of dynamic explicit analyses to determine the dynamic responses of the plate structure of various materials and equal masses under air blast loads of 1–3 kg trinitrotoluene (TNT) at 300 mm stand-off distance (SoD). These loads were applied by using the Convention Weapons Effect Program (CONWEP). To correctly predict the mutilation behavior of metallic plates, the Johnson-Cook (J-C) material model was used, and to determine the damage behavior of composite plates, Hashin and Puck-Schurmann criteria were used. The Puck-Schurmann criterion was implemented via user defined VUMAT subroutine. These numerical approaches were first verified with the validations of the literature’s experimental results. To characterize the various plates’ blast mitigation capacity, their mid-point deflection, radial deflection at the instant of peak mid-point deflection, kinetic energy, internal energy, and damage patterns were compared. The influence of applied blast loads on the pressure and impulse variations on the plates has also been investigated. Findings of the analysis showed that the aluminum plate has the highest non-residual deflection resistance, and the composite plate had a maximum energy absorption characteristic under the air blasts.

The eddies are attached, but it is all right

The behavior of velocity fluctuations near a wall has long fascinated the turbulence community, because the prevalent theoretical framework of an attached-eddy hierarchy appears to predict infinite intensities as the Reynolds number tends to infinity. Although an unbounded infinite limit is not a problem in itself, it raises the possibility of unfamiliar phenomena when the Reynolds number is large and has motivated attempts to avoid it. We review the subject and point to possible pitfalls stemming from uncritical extrapolation from low Reynolds numbers or from an over-simplification of the multiscale nature of turbulence. It is shown that large attached eddies dominate the high-Reynolds-number regime of the near-wall layer, and they behave differently from smaller-scale ones. In that limit, the near-wall layer is controlled by the outer flow, the large-scale fluctuations reduce to a local modulation of the near-wall flow by a variable friction velocity, and the kinetic-energy peak is substituted by a deeper structure with a secondary outer maximum. The friction velocity is then not necessarily the best velocity scale. While the near-wall energy peak probably becomes unbounded in wall units, it almost surely tends to zero when expressed in terms of the outer driving velocity.

Impact of the Source Material Gradation on the Disaster Mechanism of Underground Debris Flows in Mines

In mines where the natural caving method is used, the frequent occurrence of underground debris flows and the complex mine environments make it difficult to prevent and control underground debris flows. The source is one of the critical conditions for the formation of debris flows, and studying the impact of source material gradation on underground debris-flow disasters can effectively help prevent and control these occurrences. This paper describes a multiscale study of underground debris flows using physical model experiments and the discrete-element method (PFC3D) to understand the impact of the source material gradation on the disaster mechanism of underground debris flows from macroscopic and microscopic perspectives. Macroscopically, an increase in content of medium and large particles in the gradation will enhance the instantaneous destructive force. Large particles can more easily cause disasters than medium and fine particles with the same content, but the disaster-causing ability is minimized when the contents of medium and large particles exceed 50% and 60%, respectively. With increasing fine particle content, the long-distance disaster-causing ability and duration is increased. On the microscopic level, the source-level pairs affect the initial flow mode, concentration area of the force chain, average velocity, average runout distance, and change in energy of the underground debris flow. Among them, the proportion of large particles in the gradation significantly affects the change in kinetic energy, change in dissipative energy, time to reach the peak kinetic energy, and time of coincidence of dissipative energy and gravitational potential energy. The process of underground debris flow can be divided into a “sudden stage”, a “continuous impact stage”, and a “convergence and accumulation stage”. This work reveals the close relationship between source material gradation and the disaster mechanism of underground debris flows and highlights the necessity of considering the source material gradation in the prevention and control of underground debris flows. It can provide an important basic theory for the study of environmental and urban sustainable development.

Parameter characterization of the PBM-DEM method in numerical simulation of shallow buried mine explosions

Abstract To investigate the impact of various parameters on the numerical simulation of shallow buried mine explosions through the particle explosion method and discrete element method, this paper adopts a coupled method of particle blast method and discrete element method, namely the PBM-DEM method, to simulate the response of AL-6XN stainless steel plate under shallow buried mine explosions. This article first combines the experimental results of Børvik to validate the precision of the PBM-DEM approach. Then, the influence of particle quantity, interaction parameters between sand particles, and interaction parameters between sand particles and plate on the outcomes of the numerical simulations are analyzed. The analysis reveals that as the quantity of explosive particles rises, the central displacement and maximum kinetic energy of the plate escalate. In contrast, these values decrease as the number of sand particles increases. The interaction parameters between sand particles have almost no effect on the numerical simulation results. The damping and stiffness parameters between the sand particles and the plate have a pronounced effect on the numerical simulation results, and the center displacement and peak kinetic energy of the plate rise as the damping and stiffness parameters between the sand particles and the plate increase.

Influence of thermodynamic conditions on the mixing characteristics of a supercritical nitrogen jet under mode excitation

Fuel injection mixing is one of the critical factors affecting the energy conversion efficiency and emission level of thermal engines. The effect of thermodynamic conditions on mixing characteristics of supercritical cryogenic nitrogen jet under varicose mode excitation is investigated using the unsteady Reynolds-averaged Navier-Stokes method combined with real-gas thermodynamics and transport properties of nitrogen in NIST database. The ambient-to-jet density ratio is defined to represent different thermodynamic conditions and is found to affect the jet mixing enhancement directly. As the density ratio increases from 0.098 to 0.432, the density gradient reduces in the jet shear layer, mitigating flow stratification. Jet mixing is enhanced with a reduction of density potential core length by 24 % and a tripled density spreading angle. Under varicose mode excitation, large vortices are formatted close to the jet orifice, especially for higher density ratio cases. The peak of the jet turbulent kinetic energy is higher and shifts upstream as density ratio increasing. The jet mixing enhancement is further achieved, with the spreading angle increment growing from 1° to 4° and the velocity decay rate increasing from 0.03 to 0.15. As the excitation amplitude rising from 5 % to 15 %, the growth of jet momentum instability in the jet potential core breaks the velocity gradients inhibition on jet mixing. The supercritical jet enters self-similar region earlier, with density potential core length shortened by 51 % and spreading angle increased by 28 % at a middle density ratio of 0.275.

Impact and spread dynamics of a viscoelastic droplet on an inclined hydrophilic surface

In this work, the impact of a three-dimensional viscoelastic droplet on an inclined hydrophilic surface is investigated by means of direct numerical simulations. The volume-of-fluid method is adopted to capture the interface, and the Oldroyd-B model is used to describe the rheological behavior of the viscoelastic droplet. The effects of the Weissenberg number (Wi) and the Weber number (We) on the impacting and spreading processes are studied, including the viscoelastic droplet shape, velocity, energy transformation, and stress distribution. Our results are in good agreement with the experimental data in the literature. In particular, the elastic force markedly influences droplet deformation at intermediate Wi values, although this trend diminishes at higher or lower Wi values. With increasing We, the impacting viscoelastic droplet reaches its maximum deformation more rapidly, while the nonmonotonic peak of kinetic energy indicates that the droplet elasticity plays significant role at moderate We. Additionally, the inclination of the surface has a pronounced effect on the droplet spreading process, and the elongated viscoelastic droplet at larger inclination angle is likely to experience a stronger oscillation. According to further analyses, We exerts a modest influence on the change rates of the droplet potential energy and spreading length in the flow direction. However, a larger inclination angle reduces stress concentration and accelerates the change rates. Due to the oscillation dynamics, Wi exhibits a non-monotonic effect on the spreading process and induces a monotonous increase in potential energy of viscoelastic droplets. The above analyses provide insights into the impact mechanism of droplets on an inclined hydrophilic wall and, therefore, will guide the applications in the future.

Numerical study on the effect of actuation parameters on the formation characteristics of metal droplets in magnetohydrodynamic drop-on-demand (DOD) jetting

Numerical simulations have investigated the effects of electromagnetic drive waveform amplitude and pulse width on the state of metal droplet generation during drop-on-demand printing of molten metal aluminum by electromagnetic drive. It indicates that positive and negative pulses of magnetohydrodynamic(MHD) actuation applied to the molten metal in the crucible can form a so-called “push-pull” effect, which is the main mechanism affecting droplet generation and breakup. The positive pressure pulse causes the liquid metal to be extruded outward, and the negative pressure pulse promotes the fluid retraction at the nozzle to promoting the thinning of the liquid bridge and the generation of liquid droplets. With the increase in the amplitude of the applied current, the ejected molten aluminum from the crucible experiences three states: no droplet, single droplet, and droplet with satellite droplets. In the single drop state, the droplet formation time is shortened as the current peak increases and the droplet volume increases with the increase of pulse width. The energy conversion and force changes during droplet formation and falling are analyzed. When the peak kinetic energy of the ejected molten metal exceeds its surface energy, the jet breaks up and generates a single droplet. For the actuation with constant amplitude and duration for positive pulses, extending the duration of negative pulses weakens the "pull" effect, leading to a transition from the generation of a single droplet to multiple droplets. The numerical simulation results provide information on the current amplitude, pulse width, and Weber number range necessary for stable single droplet generation.

Investigation of unsteady engulfment flows in a cross‑shaped mixer by particle image velocimetry

An experimental study was conducted to characterize flow fields in a cross-shaped mixer by particle image velocimetry technique (PIV). Instantaneous flow fields describe the formation and development of secondary flows at 20 ≤ Re ≤ 400, with focus on the dynamic evolution of vortices for periodic unsteady engulfment flows. Three stages are detected during one flow period, i.e., vortex merging, growing, and splitting. Vortex characteristics including populations, distributions, and strengths, are evaluated by a vortex identification and vorticity distributions. Reversal flow regions triggered by vortex breakdown are identified in merging and splitting vortices, which periodically shed downstream, thus causing an axial oscillation. The statistical properties and proper orthogonal decomposition (POD) modes of unsteady engulfment flows are analyzed. The peak of turbulent kinetic energy appears near the chamber corners where two co-rotating vortices are observed, and it decreases with Re. The second and third-order POD modes describe large-scale coherent structures in unsteady engulfment flows.

Left atrial haemodynamic evaluation using 4D flow cardiac magnetic resonance imaging: application to hypertension and hypertrophic cardiomyopathy

Abstract Introduction Changes in left atrial (LA) hemodynamics have been suggested reflective of left ventricular (LV) disease progression. Kinetic energy (KE), viscous energy loss, and vorticity could be promising indices for the assessment of left atrial dynamics by time resolved four-dimensional cardiac magnetic resonance (4D flow CMR). Hypertrophic cardiomyopathy (HCM) patients are at risk of developing mitral regurgitation and left ventricular outflow tract obstruction, with poor outcome (1). Hypertensive myocardial remodelling has been suggested to be due to complex flow and tissue interactions leading to hypertrophy and diastolic dysfunction (2). Early detection of altered LA hemodynamic abnormalities may help non-invasive assessment, improving their long-term outcome (3). Purpose Quantitative and qualitative evaluation of left atrial hemodynamic metrics by 4D flow CMR in a cohort of HCM patients, hypertensive patients, and healthy controls with no known cardiovascular disease. Methods Eighteen HCM patients (50.0 [±18.2] years, 8 females), twenty-one hypertensive patients (55.2 [±6.2] years, 11 females), and seventeen controls (36.7 [±12.8] years, 1 female) underwent 4D flow CMR. Both patient groups had significantly higher LV-indexed mass, end-diastolic volume, and end-systolic volumes (P < 0.05). A semi-automated pipeline was used to segment the LA including pulmonary inflow and mitral outflow tracts using phase contrast magnetic resonance images derived from the 4D flow acquisition's phase and magnitude images. LA KE, viscous energy loss and vorticity were computed throughout the cardiac cycle. Results The HCM and hypertensive groups demonstrated significantly higher average KE integrated across the cardiac cycle (1.58 ± 0.79 and 1.32 ± 0.50 mJ respectively) compared to controls (1.20 ± 0.47 mJ) (P < 0.05), with the systolic curve in HCM showing the highest peak KE. Qualitatively, KE in the diastolic portion of the cardiac cycle appeared less variable between groups (Figure 1). Vorticity in HCM showed different configurations with loss of the central atrial vortex core (Figure 2). Viscous energy loss was also significantly higher in HCM patients confirming the increase in energy loss (Figure 2). Average KE across the cardiac cycle highly correlated with LA volume and pulmonary capillary wedge pressure calculated by a previously published regression method (4) (Pearson correlation: r= 0.76 and 0.71 respectively P < 0.05). There were also significant correlations with cardiac metrics such as indexed end-diastolic and indexed end-systolic volumes (Pearson correlation: r= 0.54 and 0.52 respectively P < 0.05) as well as indexed LV mass (r= 0.59 P < 0.05). Conclusion Hemodynamic metrics derived from 4D flow CMR may be valuable in establishing valuable predictive metrics of ventricular function. Integration of 4D flow MRI in clinical workflows could provide information that may be indicative of pathological onset before abnormal remodelling.Kinetic energy and viscous energy lossParticle pathlines and vorticity

Analysis of vortex structures evolution and aeroacoustic characteristics in the ultra-high-speed elevator ring-gap flow field

The continuous improvement of elevator speed has made the issue of aerodynamic noise in the hoistway more prominent. Previous research has usually focused on the characteristics of aerodynamic loads and related safety issues, and little attention has been paid to the problem of flow-induced noise. This paper established a three-dimensional geometric configuration of the ultra-high-speed elevator to study the flow behavior and aerodynamic acoustic characteristics in the hoistway using well-validated large eddy simulations. Firstly, we analyzed the unsteady flow behavior in the ring-gap flow field using large eddy simulations and captured the transient vortex structure in the flow field using the Q-criterion. We then predicted the far-field aerodynamic noise of the elevator car using the Lighthill-Curle aerodynamic acoustic equations. The results showed that the factors affecting the sound source intensity of the elevator car include the shedding position and intensity of the vortex structures. By adjusting the shedding position and reducing the intensity of the vortex structure, the sound source intensity of the elevator car wall could be effectively controlled. The change of the blocking ratio could not affect the attenuation of aerodynamic noise in the hoistway, but the increase of the blocking ratio could lead to an increase in the turbulent kinetic energy intensity and peak SPL in the hoistway. Therefore, the blocking ratio should be kept within 0.65 when designing the hoistway structure dimensions.

Sustainable use of End-of-Life-Tires (ELTs) in a vibration isolation system

Huge stockpiles of End-of-Life Tires (ELTs) are of major global concern. This paper investigates and helps to demonstrate the beneficial utilization of ELTs to provide geotechnical seismic isolation (GSI) of machine foundations located on a rubber-soil mixture (RSM). A series of laboratory tests is conducted to extend the understanding of RSM behavior beyond that previously elaborated, particularly by demonstrating the efficiency of the GSI-RSM system and by defining its optimal parametric values. The results indicate that increasing the thickness of the RSM layer and soil cap, along with the addition of rubber content, up to the optimum values lead to enhanced performance. Beyond these optimum values, the benefits start to decrease. For the determined optimum rubber content (8%), RSM layer thickness (0.1B), and soil cap thickness (0.15B) at a vibration moment level of 0.17 N.m, the GSI-RSM system achieves maximum reductions of 36%, 43%, and 77% in resonant frequency, resonant displacement, and resonant acceleration, respectively, compared to untreated beds. Moreover, the GSI-RSM system effectively reduces the developed peak particle velocity (PPV) and kinetic energy, independent of the excitation frequency. The increased damping and significant energy dissipation demonstrates the system’s effectiveness in mitigating vibrations. This environmentally-friendly technique presents a low-cost alternative for improving the vibration behavior of soil beds. It provides the basis for the wider adoption of ELTs for GSI, for machine foundations and for other infrastructure projects with similar soil vibration concerns, including building foundations, transportation infrastructure and industrial facilities. In this way the research contributes to the growing body of sustainable practices in the construction industry.

Using Ambient Pressure Photoelectron Spectroscopy to Investigate the Time Dependence of Electrostatic Potential Difference over the Interphase between an Electrode and an Electrolyte

Ambient pressure photoelectron spectroscopy (APPES) is a method well-suited for measuring the change ∆φ in electrostatic potential difference φ over an interphase between an electronic conductor and an insulator. APPES had previously been used to compare ∆φ over an interphase between an electrode and an electrolyte with the change in electrochemical potential difference ∆UWE-RE between the working and the reference electrode UWE-RE .[1] The relationship between ∆φ and ∆UWE-RE at low current-transient had been shown to follow two distinct trends depending on whether charge transfer of Li+ ions between an electrode and an electrolyte occurs or not.[1,2] In this work, APPES was used to investigate the time dependence of ∆φ after changing UWE-RE . The studied electrochemical system consisted of Au (working electrode), Li4Ti5O12 (reference electrode) and a second Li4Ti5O12 (counter electrode) with 0.008 M LiClO4 in propylene carbonate (PC) as the electrolyte. Pressure in the sample compartment was equal to the saturated PC pressure. APPES experiments were performed at HIPPIE beamline at MAX IV in Lund and were conducted as follows. After applying a potential step ∆UWE-RE , a C 1s spectrum was measured every 7 s. Incident photon energy was 1800 eV. Each spectrum was fitted using a Python code written especially for the obtained C 1s spectra. Time dependence of ∆φ was extracted from the shift in the kinetic energy ∆KE of the C=O peak (∆φ = ∆KE). Experiments were performed in both regimes, i.e. when the working electrode behaves as an ideal polarizable electrode and when it behaves as an ideal non-polarizable electrode, and have shown the time dependence of ∆φ to differ for the two regimes. Behaviour of ∆φ(t) as well as the experimental setup and spectral fitting using the Python code will be discussed.Figure 1: a) Schematic depiction of the electronic electrostatic potential φ between a working (WE) and a reference electrode (RE). Electrostatic potential profile is not to scale. b) An example of the experimentally obtained time dependence of the C=O peak kinetic energy KE(t). KE(t) is related to φ(t) as ∆φ(t) = ∆KE(t).

Hydrodynamics and Sediment Transport of Downslope Turbidity Current Through Rigid Vegetation

AbstractSystematical downslope‐turbidity‐current experiments were performed to clarify the relationship between sediment‐transport modes and current propagation patterns caused by rigid vegetation, as well as adjustments in turbulence characteristics of current. The equations for predicting the front velocities of downslope turbidity currents with emergent vegetation were proposed and validated via experimental data. Experimental results reveal that sediment deposition causes the lower turbulent kinetic energy (TKE) peaks of turbidity currents to decrease or even disappear without affecting their upper TKE peaks, while the rigid vegetation has the opposite effect. Vegetation stems destroy the longitudinal low‐high speed streaks associated with the quasi‐streamwise eddies in the near‐bed region and increase the proportions of the outward and inward interactions. In addition, sediment deposition severely suppresses the turbulent bursting events within turbidity currents but does not influence the relative proportions of the four bursting types. Rigid vegetation and sediment deposition both degrade the absolute values of the third‐order moments of velocity fluctuations without changing their signs to reduce the generation frequency of sweep events. Emergent rigid vegetation accelerates the formation of the reflected bore to provide energy for the deposited sediment to move downstream continuously. On the other hand, the dense submerged vegetation makes turbidity currents easily form the two‐head propagating mode, which allows part of the sediments carried by the upper current head to be transported downstream rather than deposited within or upstream of the vegetation region. Furthermore, the sloping boundary provides favorable conditions to initiate these specific modes for sediment transport adjusted by rigid vegetation.

Modulations of Storm-Track Activity Associated with the Baroclinic Annular Mode

Abstract The baroclinic annular mode (BAM) is the leading mode of variability in extratropical eddy activity characterized by its hemispheric-scale pulsing. Based on atmospheric reanalysis data for the Southern Hemisphere, this study reveals BAM-associated systematic modulations not only in fluxes associated with subweekly transient disturbances, as found by earlier studies, but also in their spatial structure involved in the dynamics of the BAM. Specifically, in the positive phase of the BAM characterized by enhanced activity of transient disturbances, their lower-tropospheric baroclinic structure becomes more distinct, and they tend to be more elongated meridionally in both the upper and lower troposphere. These BAM-associated structural modulations of the disturbances favor the more efficient baroclinic development via enhanced poleward heat transport and their downstream development, which can contribute to hemispheric-scale enhancement of kinetic energy associated with the disturbances. In addition, a tendency of the disturbances to exhibit horizontally tilting structure becomes more evident in the positive phase of the BAM, which is favorable for enhanced transport of westerly momentum from the subtropics to the midlatitude polar-front jet, or equivalently enhanced wave-activity propagation from the midlatitude storm track into the subtropics. This modulation lags the peak of anomalous kinetic energy of the disturbances, thus acting to contribute to the decay of the BAM signature. A set of numerical simulations suggests that the BAM-associated pulsing in storm-track activity and structural modulations are manifestations of atmospheric internal dynamics, which can be significantly amplified in the presence of a midlatitude oceanic frontal zone through the formation of more organized and coherent baroclinic wave packets.

Study on Blasting Characteristics of Shallow and Deep Soft-hard Rock Strata Based on Energy Field

The expected blasting effect of rock mass is always affected by the soft-hard rock strata with anisotropic mechanical properties, especially under the influence of in-situ stress. Based on discrete element method (PFC2D), single-hole blasting experiments are carried out considering effect of soft-hard rock strata and in-situ stress. The result is analyzed from the perspectives of cracks state, cracks number, cracks extension range and energy fields. The results show that: 1) Under different in-situ stress fields, damage degree of rock mass increases first, then decreases rapidly and ultimately keeps stable with growth of soft rock thickness. Through fitting, better change laws are obtained. 2) When detonation in hard rock, if distance between blasthole and structural plane is larger than about 4 times the radius of crushing area, cracks development is restrained with the growth of in-situ stress. 3) Rock damage degree of rock firstly ascends and then descends with growth of Uniaxial Compressive Strength (UCS). Rock damage degree reaches maximum at about 40 MPa and descends with growth of in-situ stress, when it is greater than about 80 MPa. 4) When detonation in hard rock and lower in-situ stress, if structural plane is outside crushing area, peak kinetic energy will decrease with the growth of in-situ stress as well as peak friction energy, which is contrary to the peak strain energy.

Impact of pulmonary artery flow distribution on Fontan hemodynamics and flow energetics

BackgroundWith improved life expectancy following Fontan palliation, there is an increasing population of patients with a total cavopulmonary connection. However, there is a poor understanding of which patients will experience Fontan failure and when. 4D flow MRI has identified several metrics of clinical interest, but longitudinal studies investigating hemodynamics in Fontan patients are lacking.ObjectiveWe aimed to investigate the relationship between flow distribution to the pulmonary arteries and regional hemodynamic metrics in a unique cohort with follow-up 4D flow MRI.Materials and methodsPatients with > 6 months of 4D flow MRI follow-up were included. Flow distribution from the caval veins to pulmonary arteries was measured in addition to regional measures of peak velocity, viscous energy loss (ELmean and ELtot), and kinetic energy.ResultsTen patients with total cavopulmonary connection (17.7 ± 8.8 years at baseline, follow-up: 4.4 ± 2.6 years) were included. Five subjects had unequal flow distribution from the IVC to the pulmonary arteries at baseline. Over time, these subjects tended to have larger increases in peak velocity (39.2% vs 6.6%), ELmean (11.6% vs -38.3%), ELtot (9.5% vs -36.2%), and kinetic energy (96.1% vs 36.3%) in the IVC. However, these differences were statistically insignificant. We found that changes in ELmean and ELtot were significantly associated with changes in peak velocity in the caval veins (R2 > 0.5, P < 0.001).ConclusionUnequal flow distribution from the IVC may drive increasing peak velocities and viscous energy losses, which have been associated with worse clinical outcomes. Changes in peak velocity may serve as a surrogate measure for changes in viscous energy loss.

Study on rock mass failure characteristics of double-hole delayed blasting in interbedding based on particle expansion algorithm

The existence of the interface between soft and hard rock often makes it difficult to control the blasting effect. Studying the influence of structural plane and delayed initiation time on rock blasting characteristics can make the blasting effect more controllable. In this paper, by using the Particle Flow Code (PFC2D) and particle expansion algorithm, the double-hole delayed blasting experiments of soft-hard rock are carried out, and the results are analyzed from the perspectives of fragment gradation, micro contact force and energy field. Results show that: 1) When blasting in hard rock, if the distance between structural plane and blasthole is about two times the radius of crushing area, it will easier to form large area fragments, and the fragments tend to be crushed with the increase of the distance. When the distance is 2–4 times the radius of crushing area, with the increase of delay time, the overall fragment area value increases first and then decreases, and reaches the maximum when the delay time is 4 ms. 2) When the structural plane existing in the rock mass, the delayed initiation will make the contact force become relatively uniform within a certain range. The main direction of contact force will appear in the uneven state of contact force generated by simultaneous or delayed initiation, which is close to the parallel or vertical direction of blasthole connection. 3) When blasting in hard rock, if the distance between the structural plane and the blasthole is greater than about two times the radius of the crushing area, compared with simultaneous blasting, the peak kinetic energy and peak strain energy of delayed blasting will be reduced by about 33% and 46% respectively.