Velocity Sensitivity Research Articles

Improving early mortality risk detection in light-chain cardiac amyloidosis patients with routine echocardiographic indicators and mayo staging

Abstract Background Light-chain cardiac amyloidosis (AL-CA) is a fatal cardiomyopathy caused by the deposition of monoclonal immunoglobulin light-chain in the cardiac fibers, conduction system, valves, and other parts of the heart. The Mayo 2004 staging system is widely used to assess the prognosis of AL-CA. Those in the highest-risk categories, Mayo 2004 stage IIIb, exhibit extremely poor responses to conventional treatment regimens, resulting in high early mortality rates. However, within the same stage, prognostic outcomes among patients can still vary significantly. Hence, a more detailed stratification of high-risk patients is crucial for pinpointing those at extreme risk. Objective To investigate whether conventional echocardiographic measurements can enhance the identification of high-risk patients with early mortality in AL-CA on the basis of existing risk stratification. Methods Continuous enrollment of patients diagnosed with AL-CA at our center from May 2020 to December 2022. Clinical data, echocardiography, and follow-up results of the patients were collected. Logistic regression analyses were used to identify risk factors for early mortality, with risk factor thresholds calculated using Receiver Operating Characteristic (ROC) curves. Kaplan-Meier survival analysis was employed to assess endpoint events. The diagnostic efficacy of the model was evaluated using the area under the ROC curve and the Integrated Discrimination Improvement (IDI). Results A total of 76 patients were included with an average age of 59±10 years. Among them, 51 were male (67.1%). The median follow-up duration was 10 months (ranging from 5 to 20 months). Early mortality, defined as death within 6 months, occurred in 20 patients (26.3%). Twenty-three patients were categorized under the Mayo 2004 stage IIIb (30.3%). The 6-month mortality rate for patients in the Mayo 2004 stage IIIb was 56.5%. The sensitivity of early diastolic transmitral flow velocity to early diastolic mitral annular tissue velocity ratio divided left ventricular ejection fraction [(E/e’) /LVEF] in predicting early mortality in patients with AL-CA is 63%, and the specificity is 92%.When compared to the Mayo 2004 stage IIIb alone, (E/e')/LVEF≥0.5 combined with the Mayo 2004 stage IIIb had an area under the curve of 0.731 and 0.824, respectively, in the ROC curve. The IDI was 0.113 (95% CI: 0.013-0.213, P=0.026), representing an 11.3% enhancement in the predictive value of early mortality in AL-CA patients. Conclusion Routine echocardiography derived E/e' to LVEF ratio offered added prognostic value for early mortality beyond Mayo staging.Kaplan-Meier survival curve

Data-Driven Sparse Sensor Placement Optimization on Wings for Flight-By-Feel: Bioinspired Approach and Application.

Flight-by-feel (FBF) is an approach to flight control that uses dispersed sensors on the wings of aircraft to detect flight state. While biological FBF systems, such as the wings of insects, often contain hundreds of strain and flow sensors, artificial systems are highly constrained by size, weight, and power (SWaP) considerations, especially for small aircraft. An optimization approach is needed to determine how many sensors are required and where they should be placed on the wing. Airflow fields can be highly nonlinear, and many local minima exist for sensor placement, meaning conventional optimization techniques are unreliable for this application. The Sparse Sensor Placement Optimization for Prediction (SSPOP) algorithm extracts information from a dense array of flow data using singular value decomposition and linear discriminant analysis, thereby identifying the most information-rich sparse subset of sensor locations. In this research, the SSPOP algorithm is evaluated for the placement of artificial hair sensors on a 3D delta wing model with a 45° sweep angle and a blunt leading edge. The sensor placement solution, or design point (DP), is shown to rank within the top one percent of all possible solutions by root mean square error in angle of attack prediction. This research is the first to evaluate SSPOP on a 3D model and the first to include variable length hairs for variable velocity sensitivity. A comparison of SSPOP against conventional greedy search and gradient-based optimization shows that SSPOP DP ranks nearest to optimal in over 90 percent of models and is far more robust to model variation. The successful application of SSPOP in complex 3D flows paves the way for experimental sensor placement optimization for artificial hair-cell airflow sensors and is a major step toward biomimetic flight-by-feel.

Synthesis and Properties of N1, N3‐di (2,4‐dinitrophenyl) −2‐fluoro‐1,3‐diamino‐4,6‐ Dinitrobenzene and its Analogues

AbstractPolynitrobenzene compounds are a type of heat‐resistant explosives with excellent thermal stability. This study reported three novel energetic compounds, namely compounds N1, N3‐bis(2,4‐dinitrophenyl)‐2‐fluoro‐4,6‐dinitrobenzene‐1,3‐ diamine (3), 2‐fluoro‐4,6‐dinitro‐N1,N3‐bis(2,4,6‐trinitrophenyl)benzene‐1,3‐ diamine (4), and 2‐chloro‐4,6‐dinitro‐N1,N3‐bis(2,4,6‐trinitrophenyl)benzene‐1,3‐ diamine (6). The target compounds were prepared with commercially available 2,3,4‐trifluoronitrobenzene and 2,3,4‐trichloronitrobenzole. The crystalline structures of compounds 3, 4, and 6 were determined by single‐crystal X‐ray diffraction, and the crystal densities (ρ) were calculated to be 1.7585 g cm−3, 1.6651 g cm−3, and 1.7371 g cm−3, respectively. Based on the calculated standard molar enthalpy of formation and crystal densities, the Chapman–Jouguet detonation properties of 3, 4, and 6 were predicted. Their enthalpy of formation (ΔHf), detonation velocities (D), and detonation pressures (P) were in the ranges of 110.1 kJ mol−1 to 349.9 Kj mol−1, 7264 m s−1 to 7770 m s−1, and 21.8 GPa to 25.9 GPa, respectively. Notably, the density, thermal decomposition temperature, detonation velocity, detonation pressure, and impact sensitivity value of compound 3 were 1.76 g cm−3, 313°C, 7546 m s−1, 24.2 GPa, and 16 J, respectively, suggesting that compound 3 is a high‐performance heat‐resistant explosive.

Comparative Approach to Performance Estimation of Pulsed Wave Doppler Equipment Based on Kiviat Diagram

Quality assessment of ultrasound medical systems is a demanding task due to the high number of parameters to quantify their performance: in the present study, a Kiviat diagram-based integrated approach was proposed to effectively combine the contribution of some experimental parameters and quantify the overall performance of pulsed wave Doppler (PWD) systems for clinical applications. Four test parameters were defined and assessed through custom-written measurement methods based on image analysis, implemented in the MATLAB environment, and applied to spectral images of a flow phantom, i.e., average maximum velocity sensitivity (AMVS), velocity measurements accuracy (VeMeA), lowest detectable signal (LDS), and the velocity profile discrepancy index (VPDI). The parameters above were scaled in a standard range to represent the four vertices of a Kiviat plot, whose area was considered the overall quality index of the ultrasound system in PWD mode. Five brand-new ultrasound diagnostic systems, equipped with linear array probes, were tested in two different working conditions using a commercial flow phantom as a reference. The promising results confirm the robustness of AMVS, VeMeA, and LDS parameters while suggesting further investigations on the VPDI.

Experimental and numerical study on the combustion characteristic of H2 and CH4 in oxygen-enriched environment

Oxygen-enriched combustion could rise the hazard of unexpected fire and explosion in industry. This study experimentally and numerically analyzed the combustion characteristic of H2 and CH4 in oxygen-enriched environment (Ω = 21%–100 %). For H2 at Φ = 1 and Ω = 100 %, the maximum explosion pressure and maximum pressure rise rate were about 3.89 MPa and 1259.2 MPa/s. For CH4, these values were about 4.77 MPa and 6279.4 MPa/s. The upper flammability limit of gases increased sharply with the increase of Ω, however, the lower flammability limit was almost unchanged. Besides, the increasing of Ω also could result in the rising of aforementioned combustion parameters. The sensitivity of burning velocity was also analyzed. For H2 flame at Φ = 0.8, R35 could slow down burning velocity when Ω = 21 %, but promote it when Ω = 30 % and 70 %. For CH4 flame at Φ = 1.4, the sensitivity coefficients of R11, R35, R43 and R84 changed from negative to positive when Ω increased from 21 % - 30 %–70 % - 100 %. It was concluded that the oxygen concentration not only affect the inert gas but also affect the reaction kinetic of flame.

A computational model of auditory chirp-velocity sensitivity and amplitude-modulation tuning in inferior colliculus neurons.

We demonstrate a model of chirp-velocity sensitivity in the inferior colliculus (IC) that retains the tuning to amplitude modulation (AM) that was established in earlier models. The mechanism of velocity sensitivity is sequence detection by octopus cells of the posteroventral cochlear nucleus, which have been proposed in physiological studies to respond preferentially to the order of arrival of cross-frequency inputs of different amplitudes. Model architecture is based on coincidence detection of a combination of excitatory and inhibitory inputs. Chirp-sensitivity of the IC output is largely controlled by the strength and timing of the chirp-sensitive octopus-cell inhibitory input. AM tuning is controlled by inhibition and excitation that are tuned to the same frequency. We present several example neurons that demonstrate the feasibility of the model in simulating realistic chirp-sensitivity and AM tuning for a wide range of characteristic frequencies. Additionally, we explore the systematic impact of varying parameters on model responses. The proposed model can be used to assess the contribution of IC chirp-velocity sensitivity to responses to complex sounds, such as speech.

Evolution of Turbulent Boundary Conditions on the Surface of Large Barchan Dunes: Anomalies in Aerodynamic Roughness and Shear Velocity, Aeolian Threshold, and the Role of Dune Skewness

AbstractWe recorded aerodynamic roughness and shear velocity along transects on and around mature crescent‐shaped barchan dunes of and height above the horizontal rock‐covered Qatar desert by fitting to the log‐law time‐averaged vertical velocity profiles acquired from triads of ultrasonic anemometers penetrating the inner turbulent boundary layer. Shear velocity first decreased, then recovered as air climbed on the dune, with a local maximum ahead of the crest as predicted by the Jackson and Hunt (1975, https://doi.org/10.1002/qj.49710143015) theory. Unlike flows over gentler bedforms without a slope discontinuity, an anomalous peak of shear velocity also arose on the dune centerline at the brink, which the theory attributed to skewness in the dune transect profile. The onset of aeolian transport produced a log‐law passing through the Bagnold (1941, https://doi.org/10.1007/978‐94‐009‐5682‐7) focal point. It was bracketed by noticeable hysteretic peaks in the correlation between wind speed and entrained sand flux. The dunes' rocky surroundings and topography produced an aerodynamic roughness at odds with the Nikuradse (1933, https://ntrs.nasa.gov/citations/19930093938) data for fully developed turbulent boundary layers. Large‐eddy numerical simulations illustrated the sensitivity of shear velocity to wide changes in aerodynamic roughness from desert floor to dune surface.

Influence of rotating wheels on Reynolds number sensitivity of passenger vehicle drag

Rotating wheels are essential to replicate realistic forces and flow fields during aerodynamic testing of passenger vehicles. Previous studies have found that the drag coefficient typically reduces with increased speed under rotating wheel conditions but is stable with stationary wheels. This paper investigates this velocity sensitivity for two vehicles, the aerodynamic research vehicle DrivAer and a production vehicle. Experiments with the DrivAer indicate that the drag reduction with increased speed cannot be explained by pressure changes on the vehicle body; instead, the effect is attributed to local flow changes around the wheels. Using numerical simulations, it is found that the separation at the front wheels' outer tire shoulder increases for lower velocities, thus resulting in higher drag coefficient and causing Reynolds number sensitivity. The degree of drag reduction is less for the DrivAer squareback than for the notchback due to the separation over the notchback's rear window. No direct difference is measured between various tires and rims. To assess the generality of the findings with the DrivAer, the results are compared to experiments with a production vehicle. It is observed that the drag sensitivity is less and only occurs if the rear wheels are rotating. Pressure measurements in the wheelhouses and around the wheel drive units confirm the front wheel separation's dependence on velocity and highlight the complex interaction between the front wheel wakes and rear wheel rotational state.

Long-range transport impact of a severe dust storm over the Yangtze River Basin region and its modeling sensitivity to dust emission scheme

Dust storms frequently occur in the spring over East Asia, affecting southern Mongolia and northeast China. An exceptionally powerful dust storm occurred in East Asia from March 14th to March 18th, 2021. To investigate the ability of climate models to simulate severe dust storms, we employed the Weather Research Forecast model coupled with chemistry (WRF-Chem) with Goddard Chemistry Aerosol Radiation and Transport (GOCART), SHAO and KOK dust emission schemes to simulate the evolution of this event and to characterize dust aerosols long-range transport. Results showed that this storm was caused by a Mongolian cyclone depicted at 850 hPa with a cold front, which swept dust aerosols southeastward across southern Mongolia to northeast China. Model evaluation with satellite-retrieved Aerosol Optical Depth (AOD) and observational PM10 concentrations revealed that the SHAO dust emission scheme performed better in simulating spatial and temporal distribution of AOD over the Gobi Desert (GD) but overestimated them over Taklimakan Desert (TD). In contrast, the GOCART dust emission scheme underestimated AOD over most areas except the Taklimakan Desert; the KOK dust emission scheme overestimated them over both TD and GD. Overall, the SHAO dust emission scheme had good performance in simulating the surface PM10 concentrations over the Yangtze River Basin (YRB) and depicted an increase in PM10 concentrations, which denoted the transport of dust aerosols over YRB. As a better description of the physical process of dust emission flux over the eastern region of the Gobi Desert, the SHAO dust emission scheme depicted well the spatial and temporal evolution of dust plume episodes, especially over northeast China and YRB. The significant differences in dust emission fluxes between the three dust emission schemes were attributed to the sensitivity of threshold friction velocity and erodibility factor. Thereunto, the SHAO dust emission scheme incorporated well soil particle size distribution and threshold velocity to produce the dust emission flux, which allowed higher dust emission flux over the eastern GD and under strong southwesterly transported dust aerosols to East Central China's region of North China Plain (NCP) and YRB. This study will help further the simulation of extreme dust events more accurately and the exploration of climate change's effect on dust events over East Asia.

Evaluation of surface corrosion damage in thin plates by Zero-Group Velocity Lamb waves based on PVDF comb transducers

This paper introduces a novel method for assessing surface corrosion damage in thin plates by leveraging the high sensitivity of Zero-Group Velocity (ZGV) Lamb waves and the versatility of polyvinylidene fluoride (PVDF) comb transducers. Theoretical analyses of ZGV Lamb wave modes and their differentiation from thickness vibration modes were conducted. The functionality and utility of the PVDF comb transducer tailored for the specific S1-ZGV mode were assessed. Experimental findings demonstrate that the PVDF comb transducer efficiently excites and captures the S1-ZGV mode, enabling effective assessment of surface corrosion damage in thin aluminum plates. Compared to the variations in wave velocity of surface acoustic waves (SAW) and the S1-ZGV frequency, the spectral amplitude at the initial S1-ZGV frequency exhibits a monotonically decreasing trend with increasing corrosion levels, proving to be more sensitive and reliable for evaluating surface corrosion damage. This research offers theoretical underpinnings and experimental validation for damage assessment using ZGV Lamb waves with the PVDF comb transducer, showcasing significant potential for practical engineering applications.

Analytical solution for MHD nanofluid flow over a porous wedge with melting heat transfer

This study employs the Hybrid Analytical-Numerical (HAN) method to investigate steady two-dimensional magnetohydrodynamic (MHD) nanofluid flow over a permeable wedge. Analyzing hyperbolic tangent nanofluid flow, the governing time-independent partial differential equations (PDEs) for continuity, momentum, energy, and concentration transform into a set of nonlinear third-order coupled ordinary differential equations (ODEs) through similarity transformations. These ODEs encompass critical parameters such as Lewis and Prandtl numbers, Brownian diffusion, Weissenberg number, thermophoresis, Dufour and Soret numbers, magnetic field strength, thermal radiation, power law index, and medium permeability. The study explores how variations in these parameters impact the velocity field, skin friction coefficient, Nusselt, and Sherwood numbers. Noteworthy findings include the sensitivity of fluid velocity to parameters like Weissenberg number, power law index, wedge angle, magnetic field strength, permeability, and melting heat transfer. The skin friction coefficient experiences a significant increase with specific parameter changes, while Nusselt and Sherwood numbers remain relatively constant. The local Reynolds number significantly affects Nusselt and Sherwood numbers, with a less pronounced impact on the skin friction coefficient. The study's uniqueness lies in employing the analytical HAN method and extracting recent insights from the results.

Quantitative transport mapping of multi-delay arterial spin labeling MRI detects early blood perfusion alterations in Alzheimer’s disease

BackgroundQuantitative transport mapping (QTM) of blood velocity, based on the transport equation has been demonstrated higher accuracy and sensitivity of perfusion quantification than the traditional Kety’s method-based cerebral blood flow (CBF). This study aimed to investigate the associations between QTM velocity and cognitive function in Alzheimer’s disease (AD) using multiple post-labeling delay arterial spin labeling (ASL) MRI.MethodsA total of 128 subjects (21 normal controls (NC), 80 patients with mild cognitive impairment (MCI), and 27 AD) were recruited prospectively. All participants underwent MRI examination and neuropsychological evaluation. QTM velocity and traditional CBF maps were computed from multiple delay ASL. Regional quantitative perfusion measurements were performed and compared to study group differences. We tested the hypothesis that cognition declines with reduced cerebral blood perfusion with consideration of age and gender effects.ResultsIn cortical gray matter (GM) and the hippocampus, QTM velocity and CBF showed decreased values in the AD group compared to NC and MCI groups; QTM velocity, but not CBF, showed a significant difference between MCI and NC groups. QTM velocity and CBF showed values decreasing with age; QTM velocity, but not CBF, showed a significant gender difference between male and female. QTM velocity and CBF in the hippocampus were positively correlated with cognition, including global cognition, memory, executive function, and language function.ConclusionThis study demonstrated an increased sensitivity of QTM velocity as compared with the traditional Kety’s method-based CBF. Specifically, we observed only in QTM velocity, reduced perfusion velocity in GM and the hippocampus in MCI compared with NC. Both QTM velocity and CBF demonstrated a reduction in AD vs. controls. Decreased QTM velocity and CBF in the hippocampus were correlated with poor cognitive measures. These findings suggest QTM velocity as potential biomarker for early AD blood perfusion alterations and it could provide an avenue for early intervention of AD.

Sensitivity of GNSS to vertical land motion over Europe: effects of geophysical loadings and common-mode errors

We perform a statistical sensitivity analysis on a parametric fit to vertical daily displacement time series of 244 European Permanent GNSS stations, with a focus on linear vertical land motion (VLM), i.e., station velocity. We compare two independent corrections to the raw (uncorrected) observed displacements. The first correction is physical and accounts for non-tidal atmospheric, non-tidal oceanic and hydrological loading displacements, while the second approach is an empirical correction for the common-mode errors. For the uncorrected case, we show that combining power-law and white noise stochastic models with autoregressive models yields adequate noise approximations. With this as a realistic baseline, we report improvement rates of about 14% to 24% in station velocity sensitivity, after corrections are applied. We analyze the choice of the stochastic models in detail and outline potential discrepancies between the GNSS-observed displacements and those predicted by the loading models. Furthermore, we apply restricted maximum likelihood estimation (RMLE), to remove low-frequency noise biases, which yields more reliable velocity uncertainty estimates. RMLE reveals that for a number of stations noise is best modeled by a combination of random walk, flicker noise, and white noise. The sensitivity analysis yields minimum detectable VLM parameters (linear velocities, seasonal periodic motions, and offsets), which are of interest for geophysical applications of GNSS, such as tectonic or hydrological studies.

Window size dependence of gain and bandwidth in avalanche photodiodes with multiple multiplication layers under near Geiger-mode operation.

We consider avalanche photodiodes (APDs) functioning under near Geiger-mode operation for extremely weak light (single or several photons) detection, such as in LiDAR receivers. To meet such demands, APDs which simultaneously have a large active window size, moderate bandwidth (∼GHz), and high internal gain (responsivity), are highly desired. However, it is difficult to design APDs capable of meeting the afore-mentioned performance requirements due to the intrinsic limitations of the gain-bandwidth product (GBP). In this work, we demonstrate that the GBP bottleneck in the APDs can be overcome by using multiple (3) In0.52Al0.48As based multiplication (M-) layers with a thick In0.53Ga0.47As absorber (2 µm). Moreover, the characteristic invariant 3-dB bandwidth in our APDs, from low to an extremely high operation gain, becomes more pronounced with an increase of its active window diameter (40 to 200 µm). This characteristic makes it very attractive for collecting weak light in free space as is required for LIDAR receiver applications. Comparison shows that the 200 µm APD exhibits a higher 0.9 Vbr responsivity (15 vs. 7 A/W), larger maximum gain (460 vs. 110), and higher GBP (468 vs. 131 GHz) than does the 40 µm reference sample and can sustain a constant 3-dB bandwidth (1.4 GHz) over a wide range of operation gains (10 to 460). The dependence of the APD performance on the window size can be attributed to the influence of the surface states on the edge of the etched mesa. Here, we further demonstrate a backside-illuminated structure with a flip-chip bonding package which minimizes this phenomenon in small APDs ensuring high-speed performance. Compared with the top-illuminated reference samples, the flip-chip bonding packaged device shows a further enhancement of the responsivity (10.7 vs. 7 A/W), 3-dB bandwidth (4.1 vs. 3.9 GHz), and saturation current (4.25 vs. 3.6 mA). The excellent static and dynamic performance of our flip-chip APD in turn leads to an unprecedented high velocity sensitivity (5 µm/sec) and superior quality 4-D FMCW LiDAR images compared to that obtainable with p-i-n-based or top-illuminated reference devices with the same small active window size (40 µm).

A Computational Model of Auditory Chirp-Velocity Sensitivity and Amplitude-Modulation Tuning in Inferior Colliculus Neurons.

We demonstrate a model of chirp-velocity sensitivity in the inferior colliculus (IC) that retains the tuning to amplitude modulation (AM) that was established in earlier models. The mechanism of velocity sensitivity is sequence detection by octopus cells of the posteroventral cochlear nucleus, which have been proposed in physiological studies to respond preferentially to the order of arrival of cross-frequency inputs of different amplitudes. Model architecture is based on coincidence detection of a combination of excitatory and inhibitory inputs. Chirp-sensitivity of the IC output is largely controlled by the strength and timing of the chirp-sensitive octopus-cell inhibitory input. AM tuning is controlled by inhibition and excitation that are tuned to the same frequency. We present several example neurons that demonstrate the feasibility of the model in simulating realistic chirp-sensitivity and AM tuning for a wide range of characteristic frequencies. Additionally, we explore the systematic impact of varying parameters on model responses. The proposed model can be used to assess the contribution of IC chirp-velocity sensitivity to responses to complex sounds, such as speech.

Development of novel magnetorheological dampers with low-speed sensitivity for flying car suspensions

As urban traffic environments continue to grow in complexity, there is an urgent need for a versatile mode of transportation that seamlessly transitions between terrestrial and aerial mobility. In conventional magnetorheological damper (CMRD), the magnetorheological fluid flowing through the narrow annular gap between the piston and cylinder in CMRD results in a damping force directly proportional to velocity. As velocity increases, the damping force rises sharply, posing a significant risk to the vehicle’s mechanical structure and passenger safety. This velocity sensitivity restricts their applications primarily to standard commercial vehicle suspension systems. They face significant challenges when it comes to high-speed impact scenarios. To overcome this limitation, enhance the shock-absorbing capacity of flying cars, ensure passenger safety, and improve passenger comfort during the landing phase, this study introduces a novel magnetorheological damper (NMRD) with unique internal channel structure embedded in a circular permanent magnet. In road travel mode, NMRD maintains a wide dynamic range. During high-speed impact landing, when the impact force exceeds the threshold, the pressure relief channel opens, effectively reducing the peak impact force. This feature greatly expands the application range of magnetorheological dampers. The researches included simulations of the electromagnetic induction phenomenon within the piston, The pressure relief damping force inside the NMRD valve was accurately measured by using material testing system, the peak force and peak acceleration experienced by the two dampers during impact were tested using a dedicated drop hammer apparatus. These tests demonstrate that the NMRD exhibits superior impact resistance performance compared to CMRD. This highlights the promising potential for the NMRD’s application within the suspension systems of flying cars.

Study on Sensitivity Mechanism of Low-Permeability Sandstone Reservoir in Huilu Area of Pearl River Mouth Basin

Reservoir sensitivity is a parameter that is used to evaluate the degree of change in reservoir permeability under the influence of external fluids. Accurate evaluation of reservoir sensitivity is conducive to the optimization of fluid parameters during exploration and development. Taking the Wenchang Formation and Enping Formation of the Paleogene in the Huilu area of the Pearl River Mouth Basin as the research object, reservoir sensitivity experiments were carried out. Combined with the corresponding experimental results obtained using methods such as thin section identification, scanning electron microscopy (SEM), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and screening analysis, based on mineral sensitization and pore structure sensitization, qualitative and quantitative evaluations of reservoir sensitivity were carried out, and factors affecting sensitivity and sensitization mechanisms were analyzed. This work shows the following: (1) The sandstone reservoirs in the two areas have the same clay type, but the total clay content of the Wenchang Formation is greater than that of the Enping Formation. The porosity of the Wenchang Formation is less developed than the Enping Formation. (2) The Wenchang Formation has weak or moderately weak water sensitivity and moderately weak or moderately strong flow velocity sensitivity. The water sensitivity of the Enping Group samples is moderately weak or moderately strong, the flow rate sensitivity is moderately weak, the alkali sensitivity is weak, the acid sensitivity is moderately weak, and the salinity sensitivity is moderately weak or moderately strong. (3) The sensitivity of the Wenchang Formation is mainly affected by the content of clay minerals. The sensitivity of the Enping Formation is also affected by the clay content and type. Although the clay content is not high, the permeability is more susceptible to sensitivity due to the pore structure and debris particle distribution characteristics. These conclusions are beneficial for the selection of fluid parameters and efficient reservoir development.

Laboratory study of cyclic underground hydrogen storage in porous media with evidence of a dry near-well zone and evaporation induced salt precipitation

Large-scale storage of ‘green’ hydrogen is essential in our quest to transition to renewable energy sources and achieve the net-zero emission targets. As such, Underground Hydrogen Storage (UHS) in geological porous media, such as in depleted oil and gas fields or saline aquifers, provides a cost-effective solution to store such large volumes of hydrogen (H2) to buffer seasonal fluctuations in renewable energy supply and demand. Due to the novelty of the topic, many research gaps persist, but we focus on H2 transport characteristics in the subsurface, hydrogen recoverability during cyclic operations, chemical interactions, and acoustic velocity as an indicator of H2 saturation. In this study, we investigate UHS using a triaxial core-flooding experiment to address the above-mentioned research gaps by replicating field operations in the laboratory setup at representative subsurface conditions. Unstable displacement due to immiscible two-phase flow led to early H2 breakthrough at 18% of H2 saturation, ultimate H2 saturation of 36% and withdrawal efficiency of 78% during the first cycle. However, cyclic charging and discharging led to an eventual H2 withdrawal efficiency as high as 95%. Observed chemical interactions during our 3-day experiments were negligible, but our results also indicated a strong potential for evaporation-induced salt precipitation after injection of dry H2 gas, leading to decreased reservoir porosity and permeability over time. Our ultrasonic measurements confirmed the sensitivity of P-wave velocity to H2 saturation, which decreased by 3.5% when the H2 saturation increased to 36%. This indicates that H2 plume and leaks in UHS should be possible to monitor using 4D seismic surveys. Our results help to better understand H2 flow, storage, and transport during cyclic UHS. The results indicate that H2 withdrawal efficiency increases as the UHS reservoir matures and provides evidence of a dry near-well zone and evaporation induced salt precipitation in a UHS reservoir.

Experimental analysis of acidizing in Weizhou X low permeability reservoir

AbstractAiming at the problem of increased water injection pressure and poor water injection effect during the water injection operation of Weizhou X offshore low permeability oil reservoir. The cause of clogging was clarified using cast thin section experiments, water quality compatibility experiments and reservoir sensitivity experiments, and corresponding deblocking agents were configured based on the experimental results. The experimental results show that Weizhou X oilfield has strong velocity sensitivity (damage rate 85.35%) and strong salt sensitivity (damage rate 63.02%), and there is a phenomenon of water quality incompatibility. Analysis shows that the excessive velocity of the injected water causes the core particles to fall off and the water quality is incompatible with the calcium carbonate precipitation to cause pore throat blockage as the fluid migrates to the small roar, which is the main reason for the increase in water injection pressure. Based on the analysis results, the acid solution formula was optimized and determined to be: 12% HCl + 0.5% HF + 3% CH3COOH + 0.5% C6H12N4. Indoor test results show that the acid has good clay swelling prevention and reservoir modification effects, and the average reservoir modification rate is 129.21%. The plug‐removing effect is remarkable and can be promoted in similar oil fields.

Surface strengthening mechanism of graphene-oxide membrane and its modified aluminium lamina under penetration loading

The contact surface is crucial in determining the ability of membranes or laminas to absorb energy during penetration. This study conducted experiments to explore the mechanical properties of the pristine graphene oxide (GO) membrane when dry, as well as the anti-penetration performance of four surface-modified GO membranes (dry, oil, water, and grease) under various loading velocities. Dynamic penetration occurs when the kinetic energy exceeds a specific threshold, as opposed to the quasi-static outcomes. Additionally, the examination of failure mode indicated that the GO membrane demonstrates significant elastic rebound when subjected to comparatively lower levels of dynamic loading. Further analysis after penetration revealed a transition from brittleness to ductility under dynamic loading conditions. Uniaxial tensile tests of aluminium sheets revealed a distinct negative velocity sensitivity behaviour. Moreover, surface treatment with the GO membrane can enhance the penetration failure strength and energy absorption capacity of the sheet. This study provides crucial insights into the physical principles governing the energy absorption of membrane structures and how they are influenced by surface conditions.