Pressure Step Research Articles

Machine learning model for constant volume depletion prediction of the Niger Delta condensate systems

Accurate assessment and evaluation of condensate reservoir performance is dependent on the depth of study of the condensate systems. Due to the anomalous behavior of these reservoirs, a great deal of knowledge is required to accurately forecast performances associated with these systems. Three machine learning (ML) models with proven capabilities and accuracy were developed based on Extratrees (ET), Adaptive Boosting (Adaboost) and Gradient Boosting algorithm (GBM). These models were used to exploits various parameters such as, gas composition, C7+ fraction properties, depletion pressure steps, and reservoir temperature. The data points stretching through different samples from the Niger Delta that passed the quality control tests were used in the validation of the proposed model for this study. Using various metrics to evaluate the accuracy of the models, analyzing the result of two samples A and B show that algorithm with R2 of 0.9868 and 0.9951, MAPE of 0.21224 and 0.10984, RMSE of 0.01746 and 0.01697, MAE of 0.0128 and 0.01457 for sample A and B respectively. Algorithm presents a more accurate prediction when compared with Adaboost and GBM models for two samples. The results from this study can be uniquely serialized and deployed into PVT simulation packages

Filling parameters and process optimization of mining–filling synergistic coal-based solid waste paste in Renjiazhuang mine

In this paper, the authors address the issue of large solid waste output and surface subsidence in the western coal base. They focus on the 110904 filling working face of Renjiazhuang Mine and employ a combination of theoretical analysis, numerical simulation, and field practice to analyze the limit caving step and cycle pressure step of the working face. The authors propose a mining-filling coordination scheme called “three mining and one charging”. Through numerical simulation, they demonstrate that this scheme ensures the time-space continuity of the mining-filling cycle and is theoretically feasible. Additionally, the authors conduct nine groups of orthogonal simulation tests to identify the main factors affecting the filling effect. They conclude that the filling rate is the primary controlling factor, and there is a positive correlation between the filling rate and 1-day strength. The authors implement hanging pipe filling in the return air roadway of the 110904 working face, achieving a filling material 1-day strength of 2 MPa and a filling ratio of 80%. The mining-filling synergy scheme proves effective and feasible. However, the issue of pipe plugging during the filling process requires further optimization of the particle gradation in the subsequent filling material ratio scheme. Overall, the proposed mining-filling collaborative process serves as a theoretical reference for similar filling faces.

Evaluation of a scoring system for the detection of central sensitization among women with chronic pelvic pain

Central sensitization is frequently associated with chronic pelvic pain and requires specific management. The pain is described as hypersensitivity to an innocuous stimulus that is both widespread and persistent. However, no study has evaluated if central sensitization can be measured objectively with neurophysiological tests in the pelvic and perineal area to prove this concept in women with chronic pelvic pain. This study aimed to evaluate nociceptive thresholds (primary objective) and spatial and temporal diffusion of pain among women with chronic pelvic pain and high or low scores of central sensitization. This prospective, assessor-blinded, comparative study compared a cohort of women with chronic pelvic pain and a high (>5/10; n=29) vs low (<5/10; n=24) score of sensitization according to the Convergences PP criteria. Participants underwent a noninvasive bladder sensory test, a rectal barostat test, and a muscular (algometer) and a vulvar (vulvagesiometer) sensory test. Poststimulation pain (minutes), quality of life (Medical Outcomes Study 36-Item Short Form Survey), and psychological state, comprising anxiety (State-Trait Anxiety Inventory), depression (Beck Depression Inventory Short Form), and catastrophizing (Pain Catastrophizing Scale), were assessed. The participants mostly suffered from endometriosis (35.8%), irritable bowel syndrome (35.8%), bladder pain syndrome (32.1%), and vestibulodynia (28.3%). Baseline characteristics were similar. Women with a high sensitization score had more painful diseases diagnosed (2.7±1.3 vs 1.6±0.8; P=.002) and suffered for longer (11±8 vs 6±5 years; P=.028) than participants with a low score. The bladder maximum capacity was equivalent between participants (399±168 vs 465±164 mL; P=.18). However, the pain felt at each cystometric threshold was significantly increased in women with a high sensitization score. No difference was identified for the rectal pain pressure step (29.3±5.5 vs 30.7±6.5 mm Hg; P=.38). Rectal compliance was decreased in women with a high sensitization score with a considerable increase in pain felt. The average of pain pressure thresholds at the 5 vulvar sites tested was decreased in these participants (162.5±90.5 vs 358.7±196.5 g; P=.0003). Similar results were found for the average of the pain pressure thresholds at 6 muscles tested (1.34±0.41 vs 2.63±1.52 kg/m2; P=.0002). A longer period was needed for patients with high sensitization score to obtain a VAS <3 out of 10 after the stimulation of the bladder (4.52±5.26 vs 1.27±2.96 minutes; P=.01), the rectum (3.75±3.81 vs 1.19±1.23 minutes; P=.009), and the muscles (1.46±1.69 vs 0.64±0.40 minutes; P=.002). The psychological state was equivalent between groups. No association was found between the sensory thresholds and the psychological state results. The physical component of the quality of life score was reduced in women with high sensitization score (P=.0005), with no difference in the mental component. Using neurophysiological tests, this study showed that there are objective elements to assess for the presence of central sensitization, independently of psychological factors.

Robust LQR Design Method for the Aero-Engine Integral Constant Pressure Drop Control Valve with High Precision

The closed-loop constant pressure drop control valve is widely used in aero-engine fuel servo metering systems. However, the available constant pressure drop control valve cannot realize servo tracking without static error and, often, a high proportional gain is used to reduce the static error and improve the servo tracking performance, which reduces the stability margin. In this paper, an integral constant pressure drop control valve is designed, which consists of an integral controller and a stabilizing controller. Moreover, a robust LQR design method is proposed to complete the design task. Firstly, the controlled plant’s state–space model is derived, and the augmented model with tracking error is established based on the robust servo system design theory. Secondly, a servo controller with dual functions of integral control and stabilization control is constructed and decoupled, in which the stabilizing controller guarantees the asymptotic stability as well as the anti-disturbance performance, and the integral controller realizes the servo tracking without static error. Finally, based on the robust LQR design method, two key design parameters, including the integral control gain and the stabilization control gain, are designed to complete the design task. The simulation results indicate that, even when suffering 50 mm2 metered flow area step disturbance and 1 MPa inlet pressure step change, the designed integral constant pressure drop control valve can realize the function of servo tracking without static error. The static error is almost 0, the settling time is within 0.01 s, the overshoot is within 10%, and the phase margin is more than 55°.

Pressure–Enhanced Liquid Chromatography as a Suitable Approach to Improve Selectivity for Large Molecule Separations

This work describes the application of a pressure-enhanced liquid chromatography (PE-LC) setup to tune the separation of various large molecules comprised of nucleic acids (oligonucleotides, messenger ribonucleic acid [mRNA], and deoxyribonucleic acid [DNA]). When adding pressure as a method development parameter, it indeed becomes possible to modify retention, selectivity, and peak width. As an example, the separation of oligonucleotides having sizes comprised between 40 and 100-mer in ion-pairing reversed-phase liquid chromatography (IP-RPLC) was drastically improved by using a stepwise pressure gradient to selectively shift the retention of a peak or group of peaks. Resolution was increased from 1.5 to 11.8 when setting a rapid high pressure step (twofold increased pressure) during the run. On the other hand, it was also possible to improve the separation of erythropoietin (EPO) mRNA and related impurities under ion-exchange chromatography (IEX). However, with this biomolecule, the best separation was achieved by reducing the pressure in the system. Finally, for another sample (DNA ladder) under IEX conditions, the pressure was found to have a limited impact on the overall selectivity. As highlighted in this work, pressure is an additional parameter that can be successfully used to develop LC methods of large biomolecules.

Assessment of CO2-Oil swelling behavior using molecular dynamics simulation: CO2 utilization and storage implication

CO2 injection into petroleum reservoirs is an effective enhanced oil recovery (EOR) method that can increase the recovery of oil while reducing CO2 emissions into the atmosphere. To ensure successful implementation of CO2 EOR, a detailed understanding of reservoir fluid properties and the phase behavior of CO2-oil mixtures at different scales is required. The extent to which CO2 injection improves the oil recovery factor is heavily dependent on the swelling behavior of CO2-oil mixtures, which can be quantified by swelling factors. In this study, we model a CO2-oil swelling test using molecular dynamics (MD) simulations to calculate the swelling factors over a pressure range of 24.8 to 68 bar at a temperature of 303.15 K for an actual crude oil sample. The multicomponent molecular model of the oil is built using 1000 molecules of six hydrocarbons, based on the compositional analysis of the oil sample. CO2 molecules are then added to the system at several pressure steps, based on experimental CO2 solubility data, and the resulting swelling factors are compared to their corresponding experimental values. The results of this study demonstrate that the MD simulation model can be successfully used to investigate CO2-oil swelling behavior and accurately predict the swelling factors with a minor mean percentage error of 6%. Additionally, analysis of potential energy variations due to interactions between different molecules in the system under increasing pressures and CO2 mole fractions indicates that the swelling process is primarily controlled by changes in intermolecular forces between CO2-oil and oil-oil molecular pairs, while the effect of CO2-CO2 molecular potentials on oil swelling is minimal. This work highlights the ability of the MD simulation technique to model the complex phase behavior of CO2-oil mixtures and provides unique insights into the molecular-scale mechanisms of CO2 dissolution in oil and the resulting swelling phenomenon.

Study on Fracture Behavior of Directly Covered Thick Hard Roof Based on Bearing Capacity of Supports

Mine pressure at the working face is severe due to it being directly covered by a thick hard roof. To further investigate the technology of controlling the mine pressure of a thick hard roof, the upper working face of 13,121 in Gubei mine of Huainan mining area was used as the engineering background, and similar simulation experiments, mechanical analysis, numerical simulation, and engineering applications were used to obtain the structure of a pre-cracked cut roof cut falling body, as well as establishing the mechanical model of hydraulic brace support resistance and direct covering. The results of the numerical simulation combined with the 20 m step pre-cracked top cutting showed that the cantilever length of the roof plate in the mining area was shortened by 25.61%, the stress concentration was reduced by 31.74%, and the stress level of the hydraulic brace was reduced by 26.59–28.38%, destroying the integrity of the thick hard rock body. According to the field monitoring data analysis, the working face’s initial pressure step and periodic pressure step were reduced, and the average dynamic load coefficients of the initial pressure and periodic pressure were 1.43 and 1.33, respectively, with a small dispersion of the dynamic load coefficient of the bracket. The pressure at the working face is regulated, and the chosen support equipment, in conjunction with the roof cutting scheme, can meet the thick hard roof’s support needs.

A Hybrid Model for Predicting Low Oxygen in the Return Air Corner of Shallow Coal Seams Using Random Forests and Genetic Algorithm

In order to better solve the phenomenon of low oxygen in the corner of return airway caused by abnormal gas emission in goaf during shallow coal seam mining, by analyzing the source and reason of low oxygen phenomenon, a prediction model of oxygen concentration in the corner of return airway based on genetic algorithm (GA) and random forest (RF) technology was proposed. The training sample set was established by using the field data obtained from actual monitoring, including the oxygen concentration in the return airway corner, the periodic pressure step distance of the roof, the surface temperature and atmospheric pressure. GA was used to optimize the parameters in the RF model, including trees and leaves in the forest. The results showed that the model prediction error was minimum when the number of trees was 398 and the number of leaves was 1. In addition, GA was used to optimize the number of hidden neurons and the initial weight threshold of the back-propagation neural network (BPNN). In order to verify the superiority of the model, the GA optimized RF and BPNN model are compared with the conventional RF and BPNN model. Analyze the average absolute percentage error (MAPE), root mean square error (RMSE), and average absolute error (MAE) of the prediction data of each model. The results show that the optimized RF prediction model is better than other models in terms of prediction accuracy.

Hydrocarbon Sorption in Flexible MOFs-Part II: Understanding Adsorption Kinetics.

The rate of sorption of n-butane on the structurally flexible metal-organic framework [Cu2(H-Me-trz-ia)2], including its complete structural transition between a narrow-pore phase and a large-pore phase, was studied by sorption gravimetry, IR spectroscopy, and powder X-ray diffraction at close to ambient temperature (283, 298, and 313 K). The uptake curves reveal complex interactions of adsorption on the outer surface of MOF particles, structural transition, of which the overall rate depends on several factors, including pressure step, temperature, as well as particle size, and the subsequent diffusion into newly opened pores. With the aid of a kinetic model based on the linear driving force (LDF) approach, both rates of diffusion and structural transition were studied independently of each other. It is shown that temperature and applied pressure steps have a strong effect on the rate of structural transition and thus, the overall velocity of gas uptake. For pressure steps close to the upper boundary of the gate-opening, the rate of structural transition is drastically reduced. This feature enables a fine-tuning of the overall velocity of sorption, which can even turn into anti-Arrhenius behavior.

Research on structural evolution characteristics of overburden rock for shallow buried thick coal seam mining

In order to grasp the structural evolution characteristics of overburden rock in shallow buried thick coal seam mining, the mechanism of overburden rock destabilization in the mining of 42106 comprehensive release workings in the 4-2 coal seam of Bultai coal mine was analyzed by using theoretical analysis, similar simulation and numerical simulation. The results show that: with the increase of the workface recovery length, the overburden of the comprehensive release workface experiences a continuous dynamic sinking process; the initial pressure step is about 95m, and the initial breakage position of the key layer is located at the back of the workface, and the periodic pressure step is about 25m, and the breakage position is located in front of the coal wall; when the workface recovery distance is from 65m to 95m, the overburden support stress of the comprehensive release workface appears to rise abruptly at the initial pressure. trend.

Use and perceptions of digital technology for daily life, physical activity and health information among former cardiac rehabilitation patients in Austria: A cross-sectional survey

Objective Digital health technologies offer great potential to improve access and adherence to cardiovascular disease secondary prevention measures such as regular physical activity (PA). However, the use and perceptions of digital technology (DT) among cardiac rehabilitation (CR) patients are not well understood. The aim of this study was therefore to explore the use of DT in former CR patients’ daily lives, for PA and for health information; and to gain insight into patient perceptions of DT for PA, including barriers, facilitators and requested features. Methods A cross-sectional postal survey was conducted between May 2022 and January 2023. Five Austrian CR centres contacted 500 former patients who had completed a phase 2 CR programme from January 2019 onwards. One-hundred seventeen patients (mean [SD] age, 69 ± 10 years, 22% female) responded. Descriptive and thematic analyses were conducted for closed and open-ended questions, respectively. Results Results indicated high DT usage for communication and informational aspects, and to a large extent also for PA and health information seeking. Main facilitators of DT use for PA were attributed to health and behavioural monitoring. Main barriers were lack of perceived need, lack of interest and poor usability. Most frequently requested features included pulse and blood pressure measurement, step count and compatibility to other devices. Conclusions Patients generally used and perceived DT as beneficial in daily life and for secondary prevention purposes such as PA. The survey identified facilitators, barriers and feature requests, which may inform the design and implementation of digital health interventions for CR patients.

Research on Movement Monitoring and Law of Overlying Strata in Goaf Based on IMU Technology

The overlying strata of the stope can be divided into low ( immediate roof ), medium and high strata according to the degree of influence of the mine pressure behavior of the working face. Among them, the pressure step distance of low rock strata can be judged according to the roof pressure appearance of hydraulic support, and the middle and high rock strata can not be accurately and intuitively determined only by theoretical calculation. Therefore, IMU is used to monitor the motion state and fracture distance of different layers, so as to study the relationship between them and periodic weighting. Firstly, the accuracy of monitoring effect and the error of monitoring data are determined by indoor test. Then, taking the 52507 working face of Daliuta as the engineering background, 3DEC software is used to assist the verification. The research shows that the IMU monitoring data meets the requirements of error and accuracy, and can accurately monitor the rock movement ; the movement period of rock strata at different heights is different. As the height of rock strata increases, the displacement distance of rock strata gradually increases, and the median rock strata play a key role in the movement of overlying rock strata. The periodic pressure monitored is twice the actual periodic pressure.

Transient Response of Miniature Piezoresistive Pressure Sensor Dedicated to Blast Wave Monitoring.

Blast waves generated by energetic materials involve very fast time variations in the pressure. One important issue for blast wave metrology is the accurate measurement (typical precision in the range of ±5% or better) of the static overpressure peak. For most near field configurations, this measurement requires ultra-fast sensors with response times lower than a few microseconds. In this paper, we design, model, fabricate and characterize a new ultra-fast sensor using piezo-resistive gauges at the center of a miniaturized and rectangular silicon membrane. When a pressure step of 10 bar is applied to the membrane, the signal delivered to the sensor output presents dampened oscillations, with a resonant frequency of 20.6 MHz and quality factor of 24,700 ns after the arrival of the shock wave. After removing undesirable drifts that appear after 700 ns, we may expect the sensor to have a response time (at ±5%) of 1.2 µs. Consequently, the proposed pressure sensor could be advantageously used for the accurate measurement of static overpressure peaks in blast wave experiments.

The Tasks for Russian African Studies under New Conditions and Measures to Improve the Efficiency of Science Management

The article is devoted to the exposition of the author’s vision immediate tasks of Russian African studies and the development of a set of measures to improve the efficiency and overall optimization of the management of scientific research, primarily in the field of socio-political sciences under the new conditions imposed by the Special Military Operation, aggressive pressure and destructive steps of the united West, the general growth of confrontation on the world stage and crisis of the existing structures of world economic relations. The general main direction, both for African studies and for most other areas of domestic scientific research, is to increase the efficiency of the investments therein (investments in a broad sense, and not only financial!). In practical terms, this means a departure from artificial “numeral” and bibliometric criteria of the effectiveness of scientific activity in favor of unambiguous obtaining of the practical ultimate results, needed by the state today.

Shortened Automatic Lung Recruitment Maneuvers in an In Vivo Model of Neonatal ARDS.

The aim of this study was to assess the safety and efficacy of 2 protocols for automatic lung recruitment maneuvers (LRMs) using stepwise increases in PEEP in a neonatal ARDS model. These protocols were designed with lower maximum opening pressures than traditional methods and differ each one in the duration of the opening phases (short vs prolonged). We described hemodynamic changes through invasive monitoring, and we analyzed if the behavior of the variables depends on the duration of the opening phase of the LRM. We designed a prospective, experimental study with 10 Landrace x Large White pigs < 48 h old. Under general anesthesia, tracheal intubation, invasive hemodynamic monitoring with a pediatric arterial thermodilution catheter was performed. An ARDS model was developed with bronchoalveolar lavages. Two types of LRMs were performed in each piglet, with a maximum peak inspiratory pressure (PIP) of 30 cm H2O and a PEEP 15 cm H2O applied during 8.5 s in the short LRM and 17 s in the prolonged LRM. A comparative analysis by virtue of the Wilcoxon signed-rank test and a regression analysis using generalized estimation equation were performed. We found that both LRMs were effective regarding oxygenation and respiratory mechanics. Shortening the duration of the opening phase and lowering the maximum opening pressures to PIP 30 and PEEP 15 cm H2O were above the critical opening pressure to reverse alveolar collapse in our neonatal ARDS model. Although we observed hemodynamic variations during both types of LRMs, these were well tolerated. Our LRM protocols exceeded critical opening pressures to reverse alveolar collapse in our neonatal ARDS model. This range of pressures might involve less hemodynamic disturbance. Duration of the maximum opening pressure step is a determining factor for hemodynamic alterations.

Use of acoustic myography to evaluate forelimb muscle function in retriever dogs carrying different mouth weights.

To evaluate the effect of mouth weight on gait and relative function of forelimb muscles in retriever hunting dogs as a possible explanation for biceps tendinopathy. Ten sound retriever dogs underwent acoustic myography, measuring efficiency (E-score), spatial summation (S-score), and temporal summation (T-score) during walk and trot on a pressure-sensitive walkway while carrying a 0 lb (0 kg), 1 lb (0.45 kg), and 3.2 lb (1.45 kg) mouth weight. Gait data included total pressure index (TPI), step length, and stance time. Statistics included a mixed effects model significant at p < 0.05. Forelimb TPI increased with increasing weight. There was no significant change in individual muscle parameters in response to weight. Significance was found in between-muscle comparisons. For walk, T-score was significantly lower in triceps vs. brachiocephalicus with 1 lb, not with 3.2 lb., S-score was significantly lower in the biceps at 0, 1 lb, and triceps at 0 lb. when compared to brachiocephalicus, E-score was significantly lower in deltoideus vs. brachiocephalicus at trot with l and 3.2 lb. There was an overall significant effect of muscle on T-score at trot, but no individual muscle comparison was significant. Forelimb load increases with mouth weight. Deltoideus had a longer contraction time in response to increasing weight at trot when compared to brachiocephalicus. The biceps muscle did not show increased work in response to increasing weight. The underlying etiology of biceps tendinopathies in retriever dogs remains uncertain but is not due to increasing weight.

Abstract 10914: Acute Heart Failure Due to Rupture of an Aortic Pseudoaneurysm Into the Right Atrium

Introduction: Rupture of an aortic aneurysm into the right atrium (RA) is extremely rare, while rupture into the thoracic cavity or pericardial sac is a common fatal complication. We describe a case of acute heart failure due to rupture of an aortic pseudoaneurysm with aorta-right atrial fistula. Case Summary: A 73-year-old man presented to the emergency department with dyspnea and abdominal distention. He had a history of ascending aortic replacement for type A aortic dissection 18 years ago. On arrival, physical examination revealed diminished breath sounds, leg edema but no cardiac murmurs. Investigations demonstrated abnormality of hepatic and kidney function, elevated BNP (490.9 pg/ml) in blood exam, and enlargement of ascending aortic aneurysm at the proximal anastomotic site with ascites/pleural effusion on computed tomography (CT), while left ventricular function was normal on transthoracic echocardiogram. We diagnosed acute heart failure with preserved ejection fraction and started to reduce fluid using diuretics. However, the response to diuretics was not good and the progression of lactic acidosis was observed regardless of using cardiotonic agent. Since it was becoming difficult to maintain systemic circulation, we performed further investigations before introducing mechanical support. The pulmonary artery catheterization revealed elevated RA pressure with wide pulse pressure (38/12 mmHg) and Oxygen step up in RA. An aortic root angiogram, contrast-enhanced CT and transesophageal echocardiogram showed a rupture of aortic pseudoaneurysm complicated with aorta-right atrial fistula (Figure). Although emergent surgery was performed, he unfortunately died the following day. Conclusions: This is a rare case of intracardiac perforation of aortic aneurysm diagnosed by various modalities. We should consider the possibility of developing shunt disease when we meet patients with rapidly progressive circulatory failure unresponsive to drugs.

A novel experimental-theoretical method to improve MMP estimation using VIT technique

In the gas injection process for enhanced oil recovery (EOR), the interfacial tension (IFT) and the minimum miscibility pressure (MMP) are two key parameters for evaluating the miscibility condition. The vanishing interfacial tension (VIT) method is an efficient method for measuring the interfacial tension of oil and gas versus pressure and can estimate the minimum miscibility pressure. A problem in the VIT test of a hydrocarbon system is that during this test, oil and gas densities vary due to the composition variation of both phases. But in the conventional interfacial measurement, this issue is ignored, and the initial and non-equilibrium densities are utilized for estimating the interfacial tension. In this study, it is tried to nominate a novel method for estimating the most accurate value of IFT. Hence, for this purpose, first a VIT test has been performed for a hydrocarbon gas and a live oil system and using the axisymmetric drop shape analysis (ADSA), the oil droplet has been analyzed, and the geometry factor, which has been defined in this paper, was calculated. After that, the volume of oil droplet and the gas have been measured and were used for vapor-liquid-equilibrium (VLE) or flash calculation using Peng-Robinson equation of state (PR-EOS). By VLE calculation fulfillment, the final composition of two phases is determined. Eventually, the densities of two phases have been calculated for VIT modification. Finally, the IFT results were plotted versus the pressure steps, and the MMP were estimated. Furthermore, to evaluate the results of VIT test and its modification, slim tube displacement (STD) test, which is known as the most reliable laboratory method for measuring the MMP in the oil industry, has been performed. The results show that the values obtained for MMP values for the VIT test with the corrected densities which are lower than the values obtained for the VIT test for not-corrected densities and the suggested experimental-theoretical method has been estimated the MMP more accurately. The MMP obtained by VIT test and modified VIT method was equal to 3858.72 and 3722.0 psi, respectively. Meanwhile, the slim tube test has measured the MMP equal to 3667.13 psi.

Study on Initial Fracture Characteristics of the Main Roof in Fully Mechanized Caving Mining of Inclined Coalbed

In view of the occurrence conditions of inclined coalbed, the deformation and failure characteristics of the main roof will affect the safe production of the working face. Therefore, the study of the deformation and failure characteristics of the main roof in the inclined coalbed has guiding significance for the control of surrounding rock. This paper takes the II1042 working face of Taoyuan Coal Mine as the research background, adopts the methods of theoretical analysis, numerical calculation, and field practice to analyze the evolutionary characteristics of the initial failure of the main roof of the working face under the background of the inclined coalbed, and explores the mechanical behavior characteristics of the working face roof during the mining of inclined coalbed. Based on the elastic thin plate theory, a mechanical model of the overlying rock roof of a large-angle coal seam is established, and the mechanical characteristics of the surrounding rock under the initial failure of the main roof under the unbalanced load are studied. The stress distribution characteristics of the lower surface are summarized, and the evolution law of the initial fracture of the main roof is summarized. According to the actual geological conditions of the II1042 working face of Taoyuan Coal Mine, the failure characteristics of the main roof and the initial breaking step distance are obtained by analysis, and the analysis results are verified by monitoring the mine pressure of each part of the target working face on site. The research results show that: ① Under the unbalanced load of the inclined coalbed, the deflection surface of the main roof of the coal seam is asymmetrical with respect to the arrangement direction of the working face, and the maximum deflection point is located at the upper middle position of the working face, namely (a/2, 1.836 b/π), and the main roof of the working face breaks for the first time when it advances to 35 m. ② With the advancement of the working face, the two long sides of the roof break first. With the deflection and deformation of the roof, the tensile stress in the middle of the main roof reaches the tensile strength of the rock and breaks, and then the two short sides of the roof break under the action of the breaking and turning of the rock, and the upper short side will break before the lower one. ③ According to the monitoring and analysis of the rock pressure at each part of the working face, it is judged that the initial pressure step distance is between 28.2 m and 34.6 m, which is consistent with the theoretical analysis results.

Closed-type pneumatic temperature control of a pressure-controlled loop heat pipe with a mechanically driven gas pressure controller

Precise and rapid temperature controls without overshooting or undershooting are of prime importance in numerous industrial and scientific applications. The recently-suggested pneumatic temperature control technique with a pressure-controlled loop heat pipe (PCLHP) was considered to be a fit-for-purpose method achieving those required features despite its open nature caused by use of an open-type commercial gas pressure controller. In this work, a closed-type pneumatic temperature control method was established based on the PCLHP equipped with a mechanically driven gas pressure controller (MDGPC). The MDGPC comprised a variable-volume bellows chamber and a linear actuator, and gas pressure control was realized by varying the axial dimension of the bellows chamber. The MDGPC attained a pressure control stability and resolution of approximately 1 Pa and 10 Pa, respectively. Rapid and stable recovery from sudden external pressure disturbances was demonstrated, and stepwise pressure changes of ±5 kPa were successfully achieved with a stability of approximately 1 Pa without any instabilities. With the MDGPC, pneumatic temperature control of the PCLHP was realized in a closed manner; the stability of the pneumatically controlled temperature was approximately 0.01 °C, which is comparable to the stability obtained with a commercial open-type gas pressure controller. Temperature steps of approximately 0.8 °C were generated via pressure steps of ±2.5 kPa, and the change in temperature was accurately predicted with a thermodynamic relationship. Wide-range and stable temperature changes were also attained under gradual pressure changes generated by the MDGPC. Overall, closed-type pneumatic temperature control of the PCLHP was successfully realized with the MDGPC.