Peak Pressure Values Research Articles

Vibration properties of full ceramic bearing under elastohydrodynamic fluid lubrication based on the energy approach

As an important part of rotating machinery, heat generation due to friction is inevitable during the rotating process of bearings. A large amount of heat causes the temperature of lubricating oil to increase, viscosity of lubricating oil to decrease, and lubricating performance decreases. Addressing the issue of inadequate lubrication between the rolling element and raceway due to increased lubricating oil temperature, this study focuses on full-ceramic ball bearings. It examines the impact of temperature fluctuations on the bearing's lubrication condition and investigates the vibration characteristics of the full-ceramic bearing. The variation in the viscosity of lubricating oil with respect to temperature is measured via a rotary viscometer. A dynamic model of the silicon nitride full-ceramic ball bearing, which considers the effects of elastohydrodynamic lubrication, is established. The impacts of changes in lubricating oil viscosity due to different temperatures on oil film pressure, oil film thickness, and bearing vibration are analyzed and then compared with experimental data. It is observed that under conditions of constant load and speed, the film thickness of the lubricating oil decreases as the viscosity decreases. Additionally, the second peak value of oil film pressure is reduced with the declining viscosity of the lubricating oil. As the viscosity decreases, the vibration of the bearing increases. The amplitude discrepancy between the simulated vibration signal and experimental vibration signal of the full-ceramic bearing is found to be less than 10 %, verifying the validity of the dynamic model.

Artificial intelligence-enabled reconstruction of the right ventricular pressure curve using the peak pressure value: a proof-of-concept study

Abstract Aims Conventional echocardiographic parameters of right ventricular (RV) function are afterload-dependent. Therefore, incorporating RV pressures may enable the formulation of new parameters that reflect intrinsic RV function accurately. Accordingly, we sought to develop an artificial intelligence–based method to reconstruct the RV pressure curve based on the peak RV pressure. Methods and Results We invasively acquired RV pressure in 29 heart failure patients before and after implanting a left ventricular (LV) assist device. Using these tracings, we trained various machine learning models to reconstruct the RV pressure curve of the entire cardiac cycle based on the peak value of the curve. The best-performing model was compared with two other methods that estimated RV pressures based on a reference LV and RV pressure curve, respectively. Seventeen consecutive patients from another centre who underwent right heart catheterization and simultaneous echocardiography served as an external validation cohort. Among the evaluated algorithms, multilayer perceptron (MLP) achieved the best performance with an R2 of 0.887 (0.834–0.941). The RV and LV reference curve–based methods achieved R2 values of 0.879 (0.815–0.943) and 0.636 (0.500–0.771), respectively. During external validation, MLP exhibited similarly good performance [R2 0.911 (0.873–0.948)], which decreased only modestly if the echocardiography-derived peak RV pressure was used instead of the invasively measured peak RV pressure [R2 0.802 (0.694–0.909)]. Conclusions The proposed method enables the reconstruction of the RV pressure curve using only the peak value as input. Thus, it may serve as a fundamental component for developing new echocardiographic tools targeting the afterload-adjusted assessment of RV function.

Coal‐wall spalling prevention mechanism using advance‐grooving pressure relief in the large‐mining‐height working face of a shallow coal seam

AbstractIn mining, the roof structure of a working face with a large mining height in a shallow‐buried coal seam is prone to cutting instability in front of the support, which causes support crushing and coal‐wall spalling. This study analyzes 2201 working faces with large mining heights in the Haiwan No. 3 Mine by investigating the mechanical response law of coal walls under the transient excitation of roof structure instability. A mechanical model of coal walls under dynamic and static load coupling is established, revealing the formation mechanism of coal wall spalling and its main influencing factors. Prevention and control technologies of advanced grooving and pressure relief are proposed, and grooving parameters are determined. The results show that: During the mining process of large mining height working face in shallow buried coal seam, the step change of static response of coal wall is induced by the transient instability of roof structure, and the high abutment pressure is formed on the coal wall. At the same time, the strain energy and gravitational potential energy of roof cutting instability are released to form a dynamic load. Under the action of dynamic and static load, the plastic failure dissipation power of the coal wall is greater than the critical power, and the coal wall spalling occurs. The main influencing factors are mining load, mining height, and internal friction angle of the coal wall. The method of advanced grooving pressure relief can change the roof structure and coal force mechanism, by cutting off the connection between the coal wall and immediate roof, reducing the height of the coal wall force, effectively controlling the position of the roof cut off break line, reducing the static load effect of the roof on the coal, and transferring the position of the dynamic load response to the depth of the coal wall. When the grooving height‐depth ratio k is 0.75, the peak value of the abutment pressure moves 5.57 m to the front of the working face, and the pressure relief effect is the best. The above research results provide an effective active protection method for controlling coal wall spalling in fully mechanised working face with large mining height.

Monotonic simple shear characteristics of K0 highly over-consolidated and remolded Wenzhou clay

The over consolidated clay is widely distributed in the seabed. Monotonic simple shear tests on K 0 consolidated clays with an over consolidation ratio (OCR) of 1 ∼ 14 were conducted through a multidirectional cyclic simple shear apparatus. The stress–strain relationship, pore pressure evolution, and shear strength variation under different OCRs were revealed, and differences between over and normally consolidated clay were compared. When OCR is below 8, peak values of shear stress and negative excess pore pressure both increase linearly with increasing OCR. However, the peak values tend to stabilize when OCR is above 8. Correspondingly, the occurrences of peak values no longer delay linearly, and the failure line is also shifted towards stronger strengths. An exponential formula is purposed and validated on accordance with numerous experimental data to describe the aforementioned pattern more precisely compared with the traditional power formula. Therefore, shear strengths of over consolidated clays with various OCRs and consolidation pressures can be accurately predicted according to the exponential formula and the shear strength of a normally consolidated sample with a certain consolidation pressure.

Experimental study on the equivalence ratio effects in ammonia–hydrogen–air premixed gas duct-vented explosions

To explore the combustion characteristics of ammonia‒hydrogen‒air flame, explosion venting experiments of ammonia‒hydrogen‒air mixtures with different equivalence ratios (ϕ), in the range of 0.6–1.7, are carried out in a 2 m long duct. The results show that the pressure‒time histories inside the duct have a three-peak structure (Pb, Pout, and Pext), which is caused by the burst of the vent cover, venting of burned mixtures, and counterflow flame generated by the external explosion, respectively. Pout evolves into three pressure peak types with increasing ϕ. The pressure peak value Pe is generated at the pressure measuring point outside the duct because of the external explosion. The change in Pe with ϕ is consistent with Pout and Pext, all of which increase first and then decrease with increasing ϕ and reach a maximum value at ϕ = 1.3. This study provides basic theoretical support for the promotion and application of ammonia mixed fuel.

Study on the evolution mechanism of gangue filling and overlying rock spatial structure in steeply dipping stope

The key to the safe and efficient mining of steeply dipping coal seams is the effective control of surrounding rock, and the discovery and revealing of the evolution mechanism of the spatial structure of overlying strata is the basis for the stability control of surrounding rock. By means of theoretical analysis and physical experiment, the evolution characteristics of the spatial structure of overlying strata in steeply dipping stope are clarified. Combined with numerical calculation, the stress evolution and deflection law of overlying strata are analyzed, and the influence mechanism of gangue on the spatial structure of surrounding rock and mining dynamic behavior is revealed. The results show that under the influence of unbalanced filling of gangue and key strata, the spatial bearing structure of steeply dipping has undergone multiple evolutions, showing a plate-shell combined step structure, and the size of key strata is affected by the evolution of overburden structure. The filling gangue changes the stress transfer path of the surrounding rock of the stope. There are two stress deflection boundaries in the rock strata, and the peak value of the abutment pressure is transferred to the lower part of the non-filling area. The principal stress deflection angle gradually decreases from the goaf to the boundary on both sides. The change rate of the principal stress difference and the shear stress of the rock strata decrease with the increase of the principal stress deflection angle.

Hydraulic fracturing in cement mortar subjected to seepage-sulfate coupled attack under varying pH levels

Cement-based structures are prone to hydraulic fracturing in acidic sulfate and seepage environments, posing a significant safety threat to engineering projects. To investigate the impact of pH levels on hydraulic fracturing in cement-based materials under seepage-sulfate coupled attack, hydraulic fracturing test and splitting tensile strength test have been conducted on cement mortar specimens permeated with Na2SO4 solution. A mathematical model is developed to establish the relationship between the critical water pressure of hydraulic fracturing and the splitting tensile strength at varying pH levels. The results show that the critical water pressure and splitting tensile strength initially increase and then decrease with the increase in erosion duration under pH levels of 7 and 3, while they continuously decrease with the increase in erosion duration under pH level of 1. Furthermore, the peak values of the critical water pressure and splitting tensile strength gradually diminish, which indicates an increased deterioration in hydraulic fracturing resistance with the decrease in pH value. The relationship between critical water pressure damage coefficient and erosion duration can be accurately described by a quadratic polynomial. Overall, the findings of this study can serve as a useful reference for enhancing the structural performance of cement mortar subjected to seepage-sulfate coupled attack at varying pH levels.

Intraoperative Lung Mechanics In Post-Covid Healthy Pregnants Who Required Cesarean Section: A Randomized Controlled Trial

Objective: This study aimed to investigate whether lung mechanics were affected in patients recovering from Covid-19 without ARDS who did not undergo lung imaging during the active infection period. Methods: The study included pregnant patients undergoing cesarean section operations. Participants were divided into two groups: those who had recovered from Covid-19 within the past year (group 1, n=50) and those who had never been infected with Covid-19 (group 2, n=50). The study included 100 patients divided into two groups: those who had recovered from Covid-19 within the last year (group 1, n=50) and those who had never experienced Covid-19 infection (group 2, n=50). Peak pressure (Ppeak), plateau pressure (Pplato), dynamic compliance (Cdyn), and positive end-expiratory pressure (PEEP) values, measured by the anesthesia machine, were recorded at specified time intervals following intubation. Results: Comparisons of Ppeak, Pplato, ΔP, Cdyn, and R data at specified times (1 min, 5 min, 10 min, 20 min, 30 min, and 40 min) showed no significant differences between the groups (p>0.05). Conclusion: No significant differences in lung mechanics were found between the Covid-19-recovered patient group and the control group. Differences observed in SpO2, MAP, and Cdyn values in both groups are considered to be expected changes associated with routine procedures of general anesthesia

Investigation of Split Diesel Injections in Methanol/Diesel Dual-Fuel Combustion in an Optical Engine

Methanol is a promising alternative fuel due to its wide availability of raw materials, mature production processes, and low production cost. However, because of the low cetane number, methanol must include a more reactive fuel to assist with combustion when used in compression ignition (CI) engines. In this study, based on the optical CI engine platform, methanol is injected into the intake port, and diesel is directly injected into the cylinder to achieve dual-fuel combustion. The effects of the methanol energy ratios and diesel split injection strategies on combustion are investigated. The results show that the premixed blue flame was mainly concentrated in the near wall region, whereas the yellow flame produced by diesel combustion tended to concentrate in the central region as the methanol energy ratio increased. When the methanol energy ratio exceeded 50%, the ignition delay was significantly prolonged, while the flame area was greatly reduced. Meanwhile, the peak values for the cylinder pressure and heat release rate decreased significantly, indicating a significant deterioration in combustion. At the earlier diesel pre-injection timing at −58°, the overall dual-fuel combustion at each main injection timing exhibited low-temperature premixed combustion characteristics, with a lower peak exothermic rate and flame brightness. At the later pre-injection timing at −33°, the spray flame at all main injection timings could be observed, with higher peak heat release rates and indications of thermal efficiency. Combustion at later main injection timings was characterized by diffusion combustion, and the main injection timing could effectively regulate the combustion process through phase adjustment.

Study of the Pore Water Pressure Development Characteristics of PHC Pipe Piles in Soft Soil Foundations

When constructing hollow prestressed high-strength concrete (PHC) pipe piles in soft soil foundations, the generation and dissipation of pore water pressure can induce negative friction on the pile. This phenomenon increases the settlement of the pile foundation and, in severe cases, can lead to pile deflection and flotation. To further investigate the development characteristics of pore water pressure during PHC hollow pipe pile driving in soft soil, this study combined existing theories and numerical models to analyze the generation and influence areas of pore water pressure. Field tests were conducted at three different sites: an untreated site, a surcharge preloading site, and a site treated with cement mixing piles and well dewatering. These tests monitored and analyzed the horizontal and vertical development and behavior of pore water pressure during pile driving at each site. The results indicate that during the pile driving process, when the horizontal distance from the pile center is 3d and 9d, the peak values of the excess pore water pressure in the site treated with cement mixing piles and well dewatering are 117 kPa and 100 kPa. After pile driving is completed, they decrease to 50 kPa and 48 kPa, respectively. The peak values of excess pore water pressure in the surcharge preloading site are 122 kPa and 97 kPa, and after pile driving, they decreased to 80 kPa and 21 kPa, respectively. The peak values of excess pore water pressure in untreated sites are 140 kPa and 121 kPa; after pile driving, they decreased to 82 kPa and 60 kPa, respectively. Pore water pressure increases with the depth of pile driving and decreases with distance from the pile driving location. The peak pore water pressure and dissipation rate during construction were found to be higher at the untreated site compared to the other two sites. Therefore, during pile sinking in soft soil foundations, dewatering and driving drainage boards are effective methods for reducing pore water pressure and accelerating its dissipation. These findings provide a theoretical basis and technical support for ensuring the safety of engineering constructions.

Effects of exhaust gas recirculation and ethanol-gasoline blends on combustion and emission characteristics of spark ignition engine

The combined influences of exhaust gas recirculation (EGR) and ethanol-gasoline blends on the combustion process and emissions of a single-cylinder spark ignition engine were numerically examined. Four different EGR values were employed, i.e. 0%, 2.5%, 5%, and 10%, to reveal the effect of EGR on engine performance. The engine was operated at a load of 100% and a speed of 3000 rpm. The peak values of in-cylinder pressure and temperature gradually decreased as increasing the EGR ratios. These peaks move towards the TDC as increasing the ethanol fraction in blends due to high oxygen in the mixture and burning flame speed in the cylinder. Ethanol fractions ranging from 5% to 15% can effectively improve the negative effects of EGR ratios. When increasing the ethanol fraction, the CO2 rapidly increased and concentrated around the TDC. The NOx emissions are significantly increased with increasing ethanol fraction. In the case of pure gasoline, the NOx emissions are substantially suppressed and exhibit a remarkably low value as increasing the EGR ratios. The best combination for diluting NOx emissions to a very low level is ethanol fraction ranging from E5 to E10, while the EGR rates range from 5% to 10%.

Pressure dependence of electrochemical CO2 reduction to ethanol in flow cell

The electroreduction of carbon dioxide (CO2RR) to ethanol is an ideal approach for using released CO2 and producing fuel. The impact of CO2 partial pressure (PCO2) on ethanol synthesis was significant but was not well understood. The present study investigates the pressure dependence of ethanol formation from 0.25 bar to 15 bar in a high-pressure flow cell. It displayed a volcano type. The PCO2 associated with the peak Faradaic efficiency (FE) of ethanol increased as the current density increased. The pressure peak values were 0.5 bar, 0.75 bar at 100, 200, and 300 mA cm−2, respectively. Ethanol formation kinetics was affected by adsorbate-adsorbate interactions and the physical blocking of active sites on catalysts with excess CO2. Besides, ethanol synthesis using the configured flue gas, i.e., low-concentration CO2 (VCO2 = 5–30%), was realized via system pressurization from 5 to 20 bar at 200 mA cm−2. By optimizing the combination of CO2 concentration and total pressure (Ptot), the fuel efficiency (FE) of ethanol was maximized to 26.5%. This study uncovers the ideal CO2 partial pressure for ethanol synthesis under industrial current densities, hence presenting potential industrial applications for utilizing flue gas directly in ethanol production.

Assessment of a Simplified Methodology for Preliminary Blast-Resistant Design of Insulated Precast Concrete Wall Panels

Abstract A Blast loading history can be represented by the peak pressure value and the impulse. Combinations of pressure and impulse of various blast loading scenarios can be collected to draw a pressure-impulse (P-I) curve that corresponds to a level of damage of a blast-resistant structural component. The P-I curve is typically used for a preliminary design or assessment of blast resistance structural components. Generating a P I curve for a given structural component and level of protection requires repeatedly ru nning a single degree of freedom system (SDOF) model, which can be tedious for early design stages. Hence, a simplified approach (i.e., the normalization approach) was utilized to promptly generate the P- I curve for insulated precast concrete wall panels, which relies on shifting a control P I curve using normalization factors. The generated P-I curves using the normalization approach are validated with the traditional SDOF approach curves; 95% of the examined insulted panel configurations have an error between +/-7%. As a result of the reached low error percentages, a spreadsheet- design tool was developed using this approach. The tool can further enable rapid evaluation of the performance of insulated precast concrete panels under blast loading during the preliminary design phase.

Research on abutment stress distribution of roof-cutting coalface: numerical simulation and field measurement

During the processing of deep mining, revealing the distribution of abutment pressure is significant for controlling stability of the entry. In this study, the abutment pressure distribution of roof-cutting coalface was investigated by FLAC3D and self-developed flexible detection unit (FDU). In the numerical simulation, the double-yield model was built to analyze the goaf abutment pressure under the fracturing roofs to maintain entry (FRME). Compared with the non-fracturing side, the peak value of the advanced abutment pressure on the fracturing side is reduced by 19.29% on average, the influence range (span) increases by 30.78% and the distance between the peak value and the working face increases by 66.7%. The goaf abutment pressure within 23m near the cutting side is significantly higher than other areas along the dip. The FDU was employed in the coalface to record the change of advanced abutment stress. And the field measured results are in well agreement with the numerical results.

Study on dynamic characteristics of cavitation in underwater explosion with large charge

Underwater explosions (UNDEX) generate shock waves that interact with the air–water interface and structures, leading to the occurrence of rarefaction waves and inducing cavitation phenomena. In deep-water explosions, complex coupling relationships exist between shock wave propagation, bubble motion, and cavitation evolution. The shock wave initiates the formation of cavitation, and their growth and collapse are influenced by the pressure field. The collapsing bubbles generate additional shock waves and fluid motion, affecting subsequent shock wave propagation and bubble behavior. This intricate interaction significantly impacts the hydrodynamic characteristics of deep-water explosions, including pressure distribution, density, and phase changes in the surrounding fluid. In this paper, we utilize a two-fluid phase transition model to capture the evolution of cavitation in deep-water explosions. Our numerical results demonstrate that the introduction of a two-phase vapor–liquid phase change model is necessary to accurately capture scenarios involving prominent evaporation or condensation phenomena. Furthermore, we find that the cavitation produced by the same charge under different explosion depths exhibits significant differences, as does the peak value of cavitation collapse pressure. Similarly, the cavitation produced by different charge quantities under the same explosion depth varies, and the relationship between cavitation volume and charge quantity is not a simple linear increase. The research methods and results presented in this paper provide an important reference for studying the dynamic characteristics of deep-water explosions.

Effects of train vibration load on the structure and hydraulic properties of soils

Investigating the impact of train-induced vibration loads on soil hydraulic properties, this study conducted experiments using a self-designed indoor soil seepage platform that incorporates vibration loads. The experiments were complemented with scanning electron microscopy to analyze the influence of train-induced vibration loads on soil hydraulic conductivity and its evolutionary characteristics under different vibration frequencies. The experimental results indicated that as the vibration frequency increases from no vibration (0 Hz) to 20 Hz, the time required for the soil volumetric moisture content to reach its peak and stabilize decreases rapidly. However, after the vibration frequency exceeds 20 Hz, the rate at which the time required for the volumetric moisture content to reach its peak and stabilize decreases slows down. Furthermore, the soil pore water pressure increases with the increase in vibration frequency. At a vibration frequency of 80 Hz, the peak value of pore water pressure increases by 105% compared to the non-vibration state, suggesting that higher vibration frequencies promote the development and acceleration of soil pore moisture migration. Additionally, as the vibration frequency increases, the soil hydraulic conductivity initially experiences a rapid increase, with a growth rate ranging from 40.1 to 47.4%. However, after the frequency exceeds 20 Hz, this growth rate significantly decreases, settling to only 18.6% to 7.8%. When the soil was subjected to a vibration load, the scanning electron microscopy test revealed alterations in its pore structure. Micropores and small pores transformed into macropores and mesopores. Additionally, the microstructural parameters indicated that vibration load decreased the complexity of soil pores, thereby speeding up the hydraulic conduction process. This, in turn, affected the hydraulic properties of the soil and established a relationship between pore structure complexity and soil hydraulic properties.

A Two-Temperature Fractional DPL Thermoelasticity Model with an Exponential Rabotnov Kernel for a Flexible Cylinder with Changeable Properties

This article presents a new thermoelastic model that incorporates fractional-order derivatives of two-phase heat transfer as well as a two-temperature concept. The objective of this model is to improve comprehension and forecasting of heat transport processes in two-phase-lag systems by employing fractional calculus. This model suggests a new generalized fractional derivative that can make different kinds of singular and non-singular fractional derivatives, depending on the kernels that are used. The non-singular kernels of the normalized sinc function and the Rabotnov fractional–exponential function are used to create the two new fractional derivatives. The thermoelastic responses of a solid cylinder with a restricted surface and exposed to a moving heat flux were examined in order to assess the correctness of the suggested model. It was considered that the cylinder’s thermal characteristics are dependent on the linear temperature change and that it is submerged in a continuous magnetic field. To solve the set of equations controlling the suggested issue, Laplace transforms were used. In addition to the reliance of thermal characteristics on temperature change, the influence of derivatives and fractional order was also studied by providing numerical values for the temperature, displacement, and stress components. This study found that the speed of the heat source and variable properties significantly impact the behavior of the variables under investigation. Meanwhile, the fractional parameter has a slight effect on non-dimensional temperature changes but plays a crucial role in altering the peak value of non-dimensional displacement and pressure.

Numerical Assessment of Tsunami Forces on Vertical Wall Structures: Impact of Inundation Depth and Incident Fluid Velocity

This study evaluates the tsunami forces exerted on a terrestrial structure caused by a collision-induced tsunami. Conventionally, assessing these forces relies on the inundation depth of the colliding tsunami passing without the presence of the terrestrial structure. However, it is essential to consider the inundation depth and incident fluid velocity, as both significantly influence the resulting tsunami forces. In this research, ANSYS Fluent 17.2 is employed to simulate excitation sources using a Defined Function (UDF) code within a C++ framework. The dynamic meshing technique is adopted to replicate the interactions between the bore pressure of the tsunami and an idealised vertical wall structure across three distinct water levels. Computational Fluid Dynamics (CFD) modelling demonstrates the proposed methodology's capability to offer precise impact pressure distributions concerning geographical and temporal aspects. The findings reveal specific instances: at a water depth of 10 m, the maximum Froude number is attained at 3.5 and 6.9 seconds, corresponding to a maximum pressure value of 3.9x105 Pa at 3.85 seconds for a water flow velocity of 20 m/sec. Similarly, for a water depth of 12 m, the most significant Froude number is observed at 3.95 and 6.9 seconds, with a peak pressure value of 1.8x105 Pa at 4.6 seconds, associated with a water flow velocity of 15 m/s. Additionally, at a water depth of 14 m, the maximum Froude number is reached at 4.95 and 7.1 seconds, accompanied by a maximum pressure value of 7.4x104 Pa at 4.85 seconds for a water flow velocity of 10 m/s.

Simulation Study and Engineering Application of Weakening Mine Pressure Behavior in Stope through Ground Fracturing Thick and Hard Rock Strata

Fracturing hard roofs by ground hydraulic action is an important control technology for the strong mine pressure in the stope. In this paper, a new simulation method, “separate + interface,” is proposed, and two physical simulation experiments are conducted; the phenomenon of increased goaf pressure and decreased front abutment pressure is discovered after fracturing in the key strata, and then the influence of different fractured crack shapes on the front abutment pressure and the goaf stress is revealed. The results are as follows: Firstly, the separation under the high-level hard strata blocks the transmission of overburden load to the goaf, leading to the high-stress concentration of the coal seam, which is the main reason for the large deformation of roadways and the breakage of a single hydraulic prop in the roadway. Secondly, the weakening effect of mine pressure differs when hard rock strata are fractured artificially with different types of cracks. The peak value of abutment pressure is reduced from 24.91 to 20.60 MPa, 17.80 MPa, and 16.13 MPa with the vertical crack spacing of 20 m, 15 m, and 10 m, respectively, and the related goaf pressure is increased from 2.61 to 3.54 MPa, 3.91 MPa, and 4.34 MPa, respectively. The peak value of abutment pressure decreased from 24.79 to 22.08 MPa, 19.88 MPa, and 17.73 MPa. The related goaf pressure increased from 2.61 to 3.39 MPa, 3.81 MPa, and 4.43 MPa, respectively, with the key strata also fractured into two horizontal layers, three horizontal layers, and four horizontal layers with horizontal fractures. Thirdly, after the hard roof is fractured above the No. 8202 working face, the first breaking step distance of the main roof decreased from 112.6 to 90.32 cm, while the first breaking step distances of KS2 and KS3 decreased from 106.3 and 135.8 cm to 93.5 cm and 104.8 cm, respectively, and the goaf pressure also increased. Compared to the adjacent unfractured No. 8203 working face, the mine pressure intensity of the No. 8202 working face is significantly reduced. The research results can provide useful guidance for the treatment of strong mine pressure.

Association Between Calf Muscle Tone, Plantar Surface Area, and Gross Motor Function in Children with Spastic Diplegic Cerebral Palsy.

Children diagnosed with spastic diplegic Cerebral Palsy (CP) usually demonstrate hypertonicity of the lower limb muscles which affects the normal alignments and weight reception by the feet. These impairments could be correlated to the limitations in gross motor function such as standing and walking abilities. Understanding these relationships can contribute to developing more effective rehabilitation strategies and improving overall motor outcomes for affected children. The current study was designed to explore the relationship between plantar surface area, weight distribution on the plantar surface, and gross motor function (namely, standing and walking abilities) in spastic diplegic CP children. Seventy-one spastic diplegic CP children aged 8-14 years joined this cross-sectional study. The Person's correlation coefficient and regression tests were used to assess the correlation between variables, namely, Gross Motor Function (GMFM), Calf Muscle Tone, Plantar surface area (PSA), and Peak pressure on mid and hind feet (PPMF, PPHF, respectively). These variables were assessed using the GMFM-88 scale, Modified Ashworth scale, and foot scan plantar pressure detection system, respectively. The correlation analysis demonstrated a strong to moderate positive correlation between PSA, PPMF, PPHF, and GMFM-D and GMFM-E. Additionally, regression model showed prediction levels equal to 0.791 for the GMFM-D and 0.720 for the GMFM-E categories, respectively. Standing and walking abilities were positively correlated (r ≥.6) with the increased plantar surface area and higher peak pressure on mid and hind feet in spastic diplegic CP. Future longitudinal studies should investigate changes in gross motor function in relation to improvement in plantar surface area and peak pressure values.