Initial Deceleration Research Articles

The Influence of FA Content on the Mechanical and Hydration Properties of Alkali-Activated Ground Granulated Blast Furnace Slag Cement

This study primarily investigates the effect of fly ash (FA) content on the mechanical properties and hydration performance of alkali-activated ground granulated blast furnace slag cement (AAGC) and compares the related properties with ordinary Portland cement (OPC). Additionally, we examined the hydration products; performed thermal analysis, MIP, and SEM; and determined chemically bound water and pH values of AAGC. The compressive strength of AAGC showed a retrogression phenomenon from 3 to 28 days, with the 14-day and 28-day compressive strengths of AAGC being higher than those of OPC. The AAGC with 20% FA content exhibited the highest 28-day compressive strength (75 MPa). The hydration heat release rate curve of OPC and AAGC was divided into the initial induction period, induction period, acceleration period, deceleration period, and steady period. As FA content increased, the 28-day pore volume of AAGC increased, while pH values and chemically bound water decreased. SEM images of AAGC with low FA content showed more microcracks.

Temperature effect on the kinetic profile of Ziegler–Natta catalyst in propene polymerization

Propene polymerization kinetic profiles with a diether-based Ziegler–Natta MgCl2-supported catalyst were investigated in a stainless-steel batch reactor. The initial 10 min period characterizes various temperature levels with a constant volume of liquid propene. The lowest temperature level corresponds to the usual prepolymerization temperature (10 °C), and the highest level corresponds to the usual main polymerization temperature (70 °C). The effects of the starting temperature levels were evaluated through polymerization kinetic patterns computed namely from the second polymerization period carried out at 70 °C for the next 90 min. Based on the heat transfer data, the kinetic profiles were fitted to suitable semi-empirical equations derived from fundamental kinetic approaches using the first and second orders of the catalyst active sites decay. Both approaches adequately describe the dependence of the initial activities and deceleration constants on the temperature during the initial period.

Analysis of Longitudinal Braking Stability of Lightweight Liquid Storage Mini-Track Vehicles

In this study, a theoretical model was established for longitudinal braking stability (LBS) of a lightweight liquid storage mini-track vehicle to investigate its behaviors. The influence of the tank liquid filling ratio (TLR), initial velocity (IV), and initial braking deceleration (IBD) on the LBS of the tracked vehicle was studied via FLUENT simulation. The simulation results showed that when the IV and the IBD were constant, the TLR significantly affected the braking efficiency. Conversely, when the TLR was 0.7, the braking efficiency decreased by 32%, resulting in the worst LBS. The braking efficiency at different IVs decreased by ~30% when using a constant IBD and TLR, and the braking stability exhibited little difference. Further, the braking efficiency decreased noticeably with increasing IBD; meanwhile, the braking longitudinal stability worsened. When the IBD was increased to 5 m⋅s−2, the braking efficiency decreased by 48.4%. The road experiment showed that when the tracked vehicle was accelerated and braked under limit conditions, the stability requirements were met. Finally, by combining the simulation and road experiment, the driving parameters of the tracked vehicle that could satisfy the LBS were obtained.

Analysis of HZSM‐5 molecular sieve particles attrition behavior under fluidized conditions

AbstractThe attrition behavior of HZSM‐5 zeolite catalyst particles at room temperature was investigated in a laboratory‐scale fluidized bed. The effects of three fluidization conditions on particle attrition were investigated, and a new attrition model was proposed. The results demonstrate that the attrition rate is inversely proportional to the initial particle size and proportional to the apparent gas velocity. After increasing to 80 μm and .3 m/s respectively, they are no longer the main factor affecting attrition. The effect of bed pressure on attrition rate is nonlinear, and the lowest attrition rate is obtained when the diameter‐height ratio is 1:1. Unsteady attrition stage can be divided into initial stage and deceleration stage. Surface delamination dominates particle attrition throughout the whole process, and bulk fracture is the dominant mechanism only in the deceleration stage. Based on the Gwyn equation, a new attrition model in the form of cubic polynomial is established with the ratio of total attrition rate to unstable attrition rate P as a parameter. The model has high accuracy and repeatability and is suitable for various fluidization conditions. It can effectively describe the attrition process and change rule of particles and reasonably predict the fluidization attrition rate of particles.

The basic characteristics of paste backfill materials based on highly active mineral admixtures: Part I. Preliminary study on flow, mechanics, hydration and microscopic properties

The cost performance of backfill materials in coal mines has long limited the widespread use of backfill technology. Therefore, developing backfill materials that are both cost-effective and high-performing is a pressing scientific issue that requires immediate attention. This study proposes replacing ordinary Portland cement (OPC) with highly active mineral admixtures, such as mineral powder and limestone powder, to prepare a green, low-cost, and high-performance coal mine backfill material. The use of mineral admixtures can improve the performance of the backfill material while reducing its environmental impact. The proposed approach is cost-effective and environmentally friendly. The study employed experimental tests and microscopic characterization methods, such as the slump test, hydration heat test, uniaxial compressive strength test, and microstructure test, to clarify the synergistic reaction mechanism of highly active mineral admixture-based paste backfill material (HAM-PBM). This clarification is helpful in regulating the macroscopic properties of hardened paste. The results show that: (1) The rheological properties of fresh HAM-PBM slurry are consistent with the Herschel-Bulkley model, and its fluidity meets the technical requirements for coal mine backfilling. The slump of fresh HAM-PBM slurry ranges from 140 to 145 mm, and the yield stress ranges from 3.188 to 12.819 Pa. (2) Highly active mineral admixtures significantly affect the early hydration process of HAM-PBM. The parameters of the hydration characteristics during the initial dissolution stage, acceleration stage, deceleration stage, and stabilization stage gradually decrease, while the duration of the induction stage gradually increases. This confirms that the early hydration activity of mineral powder (MP) and limestone powder (LF) is lower than that of OPC. (3) The uniaxial compressive strength (UCS) of the MP series exhibits an "anti-hook" change pattern, while the UCS of the LF series shows a decreasing change pattern. The microstructure, including the number of hydration products, microscopic density, and other characteristics, follows the same change pattern as the UCS. (4) Based on the synergistic reaction mechanism of hardened slurry, it is recommended that MP replace a maximum of 10 % of OPC and LF replace a maximum of 5 % of OPC. The need for composite replacement of OPC with MP and LF is clarified, resulting in a cost-effective coal mine backfill material. This study has contributed to the national "double carbon" policy and the low-cost backfilling application of coal mines.

Recycling multisource industrial waste residues as green binder for cemented ultrafine tailings backfill: Hydration kinetics, mechanical properties, and solidification mechanism

Incorporating mine tailings with industrial waste residues (IWRs) is progressively used to manufacture filling materials, which provides an eco-friendly disposal method for IWRs and alleviate their impact on the environment. In this study, steel slag (5, 10, 15, 20 wt%), fly ash (5, 10 wt%) and blast furnace slag (52, 57, 65, 74 wt%) as the precursor, carbide slag (16, 18, 20 wt%) and desulfurization gypsum (0, 2, 3 wt%) as the activator were reutilized to synthesize the IWRs-based binder for cemented ultrafine tailings backfill (CUFTB). Experimental tests were conducted to determine the setting time, hydration heat release, mechanical behavior, and microstructure characteristics. The hydration kinetics and solidification mechanism were expounded correspondingly. Results elucidate that the initial and final setting time of CUFTB are respectively 12.08–13.92 h and 16.92–20 h <24 h much longer than the transport time in pipeline and meets the operational requirements of mine site. Hydration process of CUFTB includes initial dissolution, induction, acceleration, deceleration, and decline stages. As the hydration proceeds, the initial stage of CUFTB is regulated by nucleation and crystal growth (NG), and gradually shifted to interactions at phase boundaries (I) or diffusion (D). The high content of carbide slag (20 wt%) promotes the hydration reaction, resulting in the increase of heat release. IWRs-based binder hydrates to form calcite, ettringite, hydroaluminite, and gehlenite. Especially, the gel products are mainly C-A-S-H, C-(Al,Na)-S-H, C-(Al,K)-S-H with Ca/Si ratio <1, demonstrating a fundamental distinction from Portland cement. Under the bonding and padding of hydration products, tailings particles are solidified well. After curing of 28 days, CUFTB exhibit high UCS values exceeding 2.0 MPa, presenting an evident improvement of 26.70% ∼ 39.20% compared to those made of Portland cement. These findings are referential for preparation of cemented paste backfill by reutilizing IWRs in mine filling field.

Reliability of phase-specific outcome measurements in change-of-direction tests using a motorized resistance device.

This study aims to determine test-retest reliability of phase-specific information during initial acceleration, deceleration, and re-acceleration phases of different change-of-direction (CoD) tests using a motorized resistance device (MRD). A total of 21 participants (16 males and five females, with mean age of 22.3 ± 3.9 years, body mass of 75.2 ± 6.9 kg, height of 177.9 ± 6.8 cm) completed the modified 505 (m505), 10-0-5, and 15-0-5 CoD tests on four different test sessions while exposed to an external load (3 kg) provided by the MRD. Outcome variables included overall and phase-specific kinetic (force, power, and impulse) and kinematic (time, distance, velocity, and acceleration/deceleration) data during the initial acceleration, deceleration, and re-acceleration phases. The deceleration and re-acceleration phases were further divided into two subphases, namely, early and late subphases, using 50% of maximum velocity. Reliability was assessed using an intraclass correlation coefficient (ICC), coefficient of variation (CV), typical error (TE), and minimal detectable change (MDC). Good to excellent ICC values (>0.75) and acceptable (<10%) to good (<5%) CV values were observed for most outcome measurements. Specifically, 80.1% (822 out of 1,026) of all variables showed good or better relative reliability (i.e., ICC ≥ 0.75), while 97.0% (995 out of 1,026) of all variables showed acceptable or better absolute reliability (i.e., CV < 10%). In conclusion, the present study demonstrates that the MRD can obtain reliable phase-specific outcome measurements across different CoD tests, providing coaches and researchers with new opportunities to advance our understanding of CoD ability and inform more advanced CoD training prescriptions.

Physical-chemical coupling excitation of low activity coal gasification slag solid waste and its application as a backfill cementitious material

To realize the green mining and clean utilization of coal resources, environmental issues such as coal mine subsidence and coal gasification slag (CGS) solid waste storage require urgent resolution. High residual carbon and low activity serve as bottlenecks for CGS to achieve safe, efficient and resourceful consumption. Therefore, in this study, we proposed the concept of graded utilization of CGS and conducted a study on physical–chemical coupling to stimulate the hydration activity of CGS. We prepared a modified coal gasification slag-based cement paste backfill material (MCGS-CPB) to meet the technical requirements of coal mine backfilling. Through various experimental tests and microscopic characterization methods (uniaxial compressive strength, hydration heat and microscopic tests, etc.), we elucidated the modification mechanism of CGS, and the synergistic reaction law of MCGS-CPB was clarified. The following results were obtained. (1) The best excitation approach for CGS hydration activity was salt modification, and the early strength of MCGS-CPB prepared with CGS excited by sodium sulfate (SS) developed rapidly, while the later strengths showed expansion and deterioration. The strength development of MCGS-CPB prepared by CGS activated with calcium chloride (CC) was relatively stable, and the excitation effect was ideal. (2) The salt modification of CGS had a significant effect on the early hydration process of MCGS-CPB. The durations of the initial dissolution, acceleration, deceleration and slow reaction stages were prolonged, and the duration of the induction stage was shortened, while the hydration heat release rate increased. (3) The salt modification of CGS had a significant effect on the microstructure of MCGS-CPB, primarily due to the difference in excitation effect of salt modification on CGS on pozzolanic activity. This study provided theoretical guidance for the safe, efficient and resourceful utilization of CGS.

Development and field application of a modified magnesium slag-based mine filling cementitious material

How to make high value use of solid waste is a key issue in achieving sustainable development. In this study, a modified magnesium slag-based cementitious material (M·C) for mine filling was developed using industrial solid waste modified magnesium slag (MMS), fly ash (FA), and desulfurization gypsum (DG); the mechanical properties, stability, hydration heat and synergistic reaction mechanism of M·C were investigated; and the M·C with optimized ratios was used to prepare cemented aeolian sand/coal gangue backfill material for industrial mine backfill tests. The results revealed that (1) the uniaxial compressive strength (UCS) of M·C at 28 d was 5.60–19.30 MPa, and the FA and DG contributed significantly to the development of the UCS of M·C. A combination of 65–90% MMS, 2.5–7.5% DG and 5–35% FA was determined to be optimum for the preparation of M·C. (2) The expansion rate (Ex) of M·C increased rapidly in the early stage, increased slowly after 28 d, and stabilized after 90 d. E28 of M·C was 0.107%–0.188%, which satisfied the requirement of Ex ≤ 0.6% in GB/T 2938. (3) The hydrated exothermic process of M·C was divided into initial dissolution, induction, acceleration, deceleration and slow reaction stages. DG can effectively promote the early hydration process of M·C, while the contribution of FA is not noticeable, and even reduces the hydration heat of M·C. (4) The hydration of MMS generates C-S-H gels and CH to increase the strength and form an alkaline environment. DG promotes the dissolution and polymerization of MMS and FA into C-S(A)-H gels and ettringite, a process that consumes Ca2+ and OH− and promotes the hydration of MMS. (5) The UCS of the 28 d downhole cores from the Changxing and Mahuangliang coal mines were 7.73 and 12.62 MPa, respectively, and the leaching indexes met the requirements stated in GB/T 14848 (Ⅲ), both of which reach the requisites for safe underground backfill. The results of this study demonstrate the feasibility and advancements of the new all-solid waste M·C replacement cement and its backfill application, and also standardizes the production and filling application route of M·C and accelerates the industrialization process of this technology.

Numerical Investigation of the Evolution Process of an Open-Pit Mine Landslide Using Discrete-Element Method

Because of the complexity of geological conditions and disturbance of external factors, the process of instability of open-pit landslides is very complicated. To illustrate this complex process, taking an open-pit coal mine landslide as an example, an accurate landslide geological section was established via detailed field investigation, remote sensing image interpretation, and field borehole data, in this study. A two-dimensional discrete-element model was established by the Fast CPU Matrix Computing of Discrete-Element Method (MatDEM, Version 1.60). The failure evolution of the landslide was investigated; then, the deformation behavior and dynamic characteristics of the landslide were systematically studied. The analyses of the failure process, velocity, displacement, and heat showed that the evolution of the landslide could be divided into the stages of initial deformation, accelerated deformation, and deceleration and stabilization. During the movement of the landslide, the gravitational potential energy of the landslide gradually converted into kinetic energy, heat, and elastic potential energy. The kinetic energy in the initial stage was small but rapidly increased and occupied the dominant position in the second stage. The kinetic energy gradually decreased and tended to be stable in the third stage. The final geometry and accumulation characteristics of the landslide obtained by numerical simulation were consistent with the corresponding field investigation and remote sensing interpretation. This work can provide a reference for the study of the evolution and prevention of open-pit mine landslides.

Using minimum effort duration can compromise the analysis of acceleration and deceleration demands in football

ABSTRACT The aim of this study was to characterise football players’ acceleration and deceleration demands regarding duration, initial velocity, and effort magnitude without a minimum effort duration. Forty-two male professional players were monitored daily during four training weeks, using a global position system. Players were divided according to their playing positions as central defenders, fullbacks, central midfielders, wide midfielders, and forwards. Acceleration and deceleration efforts were analysed from the start of the change in velocity until it stopped increasing (acceleration) or decreasing (deceleration). Descriptive statistics were performed for occurrences, initial velocities, and average and peak magnitudes. Comparisons between playing positions were conducted with one-way analysis of variance (ANOVA). The frequency of accelerations and decelerations decreased as the duration increased. The initial deceleration velocity increased with duration, but no changes were seen in the acceleration initial velocity. The average effort’s magnitude increased with duration, while the peak magnitudes decreased, showing acceleration and deceleration peaks between 0.5–1.3 and 0.1–0.3 s, respectively. Differences between playing positions occurred between 0.7 and 2.5 s. In conclusion, the measurement of accelerations and decelerations should avoid the use of minimum effort duration since it can modify the real training load of football players.

The Numerical Analysis of Non-Newtonian Blood Flow in a Mechanical Heart Valve

Background: The non-physiological structure of mechanical heart valves (MHVs) affects the blood flow field, especially the complex microstructure at the hinge. Numerous studies suggest that the blood flow field in the aortic area with an MHV can be considered Newtonian. However, the Newtonian assumption is occasionally unreasonable, where blood viscosity changes with shear rate, exhibiting non-Newtonian shear-thinning characteristics. Methods: In this research, a comprehensive study of the non-Newtonian effects on the hemodynamic behavior of MHVs was performed. The impact of the Newtonian hypothesis was investigated on the internal hemodynamics of MHVs. Several non-Newtonian and Newtonian models were used to analyze the chamber flow and blood viscosity. MHVs were modeled and placed in simplified arteries. After the unstructured mesh was generated, a simulation was performed in OpenFOAM to analyze its hemodynamic parameters. Results: In the study of the non-Newtonian viscosity model, the Casson model differs significantly from the Newtonian model, resulting in a 70.34% higher wall shear stress. In the modified Cross and Carreau models, the non-Newtonian behavior can significantly simulate blood in the MHV at different stages during initial and intermediate deceleration. The narrowing of the hinge region in particular, has a significant impact on evaluating blood rheology. The low flow rate and high wall shear force at the hinge can cause blood cell accumulation and injury time, resulting in hemolytic thrombosis. Conclusion: The results exhibit that the Newtonian hypothesis underestimates the hemodynamics of MHVs, whose complex structure leads to increased recirculation, stagnation, and eddy current structure, and a reasonable choice of blood viscosity model may improve the result accuracy. Modfied Cross and Carreau viscosity models effectively exhibit the shear-thinning behavior in MHV blood simulations.

Terminus change of Kaskawulsh Glacier, Yukon, under a warming climate: retreat, thinning, slowdown and modified proglacial lake geometry

AbstractLinks between proglacial lakes and glacier dynamics are poorly understood but are necessary to predict how mountain glaciers will react to a warmer, wetter climate, where such lakes are expected to increase both in number and volume. Here, we examine a long-term (~120 year) record of terminus retreat, thinning and surface velocities from in-situ and remote sensing observations at the terminus of Kaskawulsh Glacier, Yukon, Canada, and determine the impact of a local proglacial hydrological reorganisation on glacier dynamics. After an initial deceleration during the late 1990s, terminus velocities increased at a rate of 3 m a−2from 2000–12, while proglacial Slims Lake area increased simultaneously. The rapid drainage of the lake in May 2016 substantially altered the velocity profile, decreasing annual velocities by 48% within 3 km of the terminus between 2015 and 2021, at an average rate of ~ 12.5 m a−2. A key cause of the rapid drop in glacier motion was a reduction in flotation of the lower part of the glacier terminus after lake drainage. This has important implications for glacier dynamics and provides one of the first assessments of the impacts of a rapid proglacial lake drainage event on local terminus velocities.

Barrow holographic dark energy models in f(Q) symmetric teleparallel gravity with Lambert function distribution

The paper presents Barrow holographic dark energy (infrared cut-off is the Hubble horizon) suggested by Barrow [The area of a rough black hole, Phys. Lett. B 808 (2020) 135643] recently in an anisotropic Bianchi type-I Universe within the framework of [Formula: see text] symmetric teleparallel gravity, where the non-metricity scalar [Formula: see text] is responsible for the gravitational interaction. We consider two cases: Interacting and non-interacting models of pressureless dark matter and Barrow holographic dark energy by solving [Formula: see text] symmetric teleparallel field equations. To find the exact solutions of the field equations, we assume that the time-redshift relation follows a Lambert function distribution as [Formula: see text], where [Formula: see text], [Formula: see text] and [Formula: see text] are non-negative constants and [Formula: see text] represents the age of the Universe. Moreover, we discuss several cosmological parameters such as energy density, equation of state (EoS) and skewness parameters, squared sound speed, and [Formula: see text] plane. Finally, we found the values of the deceleration parameter (DP) for the Lambert function distribution as [Formula: see text] and [Formula: see text] which are consistent with recent observational data, i.e. DP evolves with cosmic time from initial deceleration to late-time acceleration.

What employees do today because of their experience yesterday: Previous exposure to yellow:number aspects as a cause for SPAD incidents

When a train passes a red aspect, this is called a Signal Passed at Danger event or SPAD. Sometimes it is easy to identify the SPAD cause but in other cases it is unclear why the incident occurred, especially if the system operated as usual and the train driver was trained and experienced just like his or her colleagues. In previous research, train driver deceleration behaviour has been shown to be influenced by frequent exposure in the previous 14 days to less restrictive and visually similar signal aspects in the same location. Previous exposure can contribute to SPAD causation unless the initial insufficient deceleration is corrected in time. Six years of SPAD data and red aspect approaches in the Netherlands was used to test whether previous exposure to yellow:number aspects corresponds with a statistically significant increase in SPAD incidents if there is a small window for correction available to drivers. The permitted track speed and signal distance influence the size of this window. The results provide evidence for previous exposure as a cause for SPADs and details to identify locations with increased SPAD probability. Changes in infrastructure and timetable design or adding safety measures for these locations can prevent future SPADs.

Relaxation characteristics and state evolution of water during the early-age reaction of alkali-activated slag as monitored by low field nuclear magnetic resonance

Low field nuclear magnetic resonance (LF-NMR) was used to monitor the evolution characteristics of transverse relaxation time (T2) of the water in sodium hydroxide (SH) and sodium silicate (SS) activated slag pastes. According to the T2 weighted average value evolution curve, the early-age reaction process of SH-activated system could be divided into three typical stages: initial setting stage (I), acceleration stage (II) and deceleration stage (III). However, another two distinguishable stages including the second acceleration stage (Ⅳ) and the second deceleration stage (Ⅴ) could be identified in SS-activated system. The essential reactions in different reaction stages of the two types of alkali-activated pastes were discussed. The obtained relaxation signals were employed to determine the chemically bound water content in different alkali-activated slag (AAS) pastes at specific reaction stages, as well as the dynamic change of the relative contents of gel water, capillary water and free water with reaction time. The influence mechanism of the initial active SiO44− oligomer in activator solution on the early-age reaction of AAS was revealed. A distinct water release behavior was observed in the geopolymerization process at the acceleration stages of each AAS paste.

Examining braking behaviour during failed lane-changing attempts in a simulated connected environment with driving aids

This study examines braking behaviour of drivers assisted with driving aids in a connected environment compared to when they are driving without it during failed lane-changing attempts that often exerts more pressure on the immediate follower in the target lane in the form of hard decelerations, which increases crash risk. To achieve this aim, the CARRS-Q Advanced Driving Simulator is utilised, where 78 participants faced a failed-lane-changing attempt of a lane-changer from the adjacent lane into two randomised driving conditions: (a) baseline (without driving aids); and (b) connected environment (with driving aids). A descriptive analysis of braking profiles reveals decreased decelerations among drivers in the connected environment, compared to when they are driving in the baseline condition. To model braking behaviour, more specifically the time taken by drivers to reduce their initial speeds to the minimum speeds, a grouped random parameters hazard-based duration model is developed. Factors found to significantly impact the braking behaviour are initial speed, spacing, maximum deceleration, driving condition, driver age, and gender. The developed model reveals that drivers’ braking times may increase or decrease in the connected environment compared to those in the baseline condition. However, a majority of drivers in the connected environment tend to reduce speeds earlier with a lower deceleration rate, exhibiting smoother speed reductions and larger safety margins. A decision tree analysis reveals that middle-aged and male drivers take longer to reduce their speeds in the baseline condition but shorter in the connected environment. This study concludes that followers in the connected environment respond to failed lane-changing attempts more swiftly, thereby increasing safety margins.

Analiza radnih parametara kočenja pri ispitivanju habanja kočnica i nastanka čestica na inercijalnom kočnom dinamometru

In parallel with the significant reduction of the impact of vehicles on the environment, the development of modern propulsion systems that have less and less harmful impact, new pollutants are being identified on the vehicle. One of the such pollutants is the brakes, which wear out and lead to the formation of particles that are released into the air, i.e. generally into the environment. Investigation of the mechanism of particle formation during braking, and thus the brake wear is today becoming one of the important areas of research. The most common tests in this area are performed using initial brake dynamometers and pin-on-disc machines. An overview of the influence of some operation parameters (initial vehicle speed, braking pressure, and deceleration) that varies frequently during testing on an inertial brake dynamometer is performed in this paper. There are a number of tests and cycles that are applied during research, but they are not specifically prescribed for testing the particle formation during braking. The UNECE (United Nations Economic Commission for Europe) has included it in its plan and is in the development phase of introducing standardized cycles that will prescribe the braking cycle, the purpose of which will be to examine the formation of particles. This kind of review paper can be important for researchers who are engaged in this field, and the develop their own cycles or tests to examine the concentration or mass of particles formed during braking.

Study on unsteady seepage characteristics and EUR evaluation methods of tight channel sandstone gas reservoirs

Tight channel sandstone gas reservoirs have the characteristics of strong heterogeneity, low porosity and permeability, and slow formation energy supply in the later stage of mining. In the process of gas well development, the initial production deceleration rate is fast, the later production deceleration rate is slow, and the EUR prediction result is large in error. In response to the above problems, this paper starts from the perspective of seepage mechanics, establishes a EUR evaluation mathematical model, derives the staged fractured horizontal well pressure response model and productivity model, predicts future production performance based on the production instability method, and uses Topaze The production analysis software adopts the method of production instability analysis to simulate and analyze the single well controlled reserves at different production times in stages, which further confirms the change process. The research results of this paper have certain guiding significance for predicting and analyzing single-well EUR.

Tunable Drop Splashing on Magnetoactive Elastomers

AbstractThe significant effect of an external dc magnetic field on the splashing behavior of ethanol drops impacting on the unstructured (flat) surface of soft magnetoactive elastomers (MAEs) is reported. The Weber number corresponding to the transition between the deposition and the splashing regime is reduced by ≈20% in a moderate magnetic field of ≈300 mT. Alongside this effect, a two‐fold increase of the initial deceleration of the ejection sheet is observed for the softest sample. The main underlying mechanism for the observed phenomena is believed to be the magnetic‐field‐induced stiffening of the MAEs. Further possible mechanisms are magnetically induced changes in the surface roughness and magnetic‐field‐induced plasticity (magnetic shape memory effect). The potential application areas are magnetically regulable wetting and magneto‐responsive surfaces for controlling the drop splashing.