Effect of particle size of coal dust on explosion pressure

The effect of the particle size of coal dust on explosion pressure and the rising rate of explosion pressure is studied. Three coal dusts from Lingan Coal Mine in Canada and Datong Coal Mine in China are selected to test. The influence of particle size on the maximum explosion pressure P max and maximum pressure rising rate (d p /d t ) max of each coal dust was tested experimentally. The results indicate that with the decrease of particle size of coal dusts, explosion pressure increases on condition of the same concentration. If the concentration of coal dust is different, the maximum explosion pressure appears at the concentration of 500 g/m^3. The smaller the particle size of coal dusts, the larger the rising rate of explosion pressure of coal dust. When the concentration of coal dust is 500 g/m^3, the rising rate of explosion pressure of each coal dust is the maximum.

Analysis and verification of gas content and pressure change rate characteristics in hydraulic system

Gas content of the hydraulic system directly affects the rate of pressure change of the hydraulic system. The purpose of this paper is to establish a mathematical model of oil gas content, hydraulic system pressure and pressure rise rate, obtain corresponding oil pressure value when the pressure rise rate of different gas content is maximum, and verify the accuracy of this conclusion by the FLUENT simulation software. On this basis, a rapid pressure building device of the hydraulic system is developed and designed. The above oil pressure value is used as the working cut-off pressure of the rapid pressure building device, and then the hydraulic oil pump continues to pressurize to the highest working pressure required by the system. The research content can replace the hydraulic system from the initial low pressure to the rapid pressure build-up of the oil, thus increasing the construction pressure of the hydraulic system. The research results show that the rapid pressure building device effectively reduces the time for the hydraulic system to establish pressure. Through the analysis of theoretical derivation and the collected experimental data, the error is about 5.9%, which verifies the correctness of the theoretical formula.

Predictive Value of Blood Pressure,Heart Rate,and Blood Pressure/Heart Rate Ratio in a Chinese Subpopulation with Vasovagal Syncope

Objective:The head-up tilt test(HUTT)is widely used but is time-consuming and not cost-effective to evaluate patients with vasovagal syncope(VVS).The present study aims to verify the hypothesis that ambulatory blood pressure(BP)monitoring(ABPM)and the simplistic tilt test may be potential alternatives to the HUTT.Methods:The study consecutively enrolled 360 patients who underwent the HUTT to evaluate VVS.BP),heart rate(HR),and BP/HR ratios derived from ABPM and the simplistic tilt test were evaluated to predict the presence,pattern,and stage of syncope during the HUTT.Results:Mixed response was the commonest pattern,and syncope occurred frequently with infusion of isoproterenol at a rate of 3μg/min.During the simplistic tilt test,the cardioinhibitory group had higher tilted BP/HR ratios than the vasodepressor group,while the vasodepressor group had a faster tilted HR and a larger HR difference than the cardioinhibitory group.The higher the BP/HR ratio in the tilted position,the higher the isoproterenol dosage needed to induce a positive response.During ABPM,BP/HR ratios were signifi cantly higher in the cardioinhibitory group than in the vasodepressor group.The higher the ABPM-derived BP,the higher the dosage of isoproterenol needed to induce syncope.There were signifi cant correlations in BP/HR ratios between ABPM and the supine position in the vasodepressor group,while signifi cant correlation was found only for the diastolic BP/HR ratio between ABPM and the tilted position in the cardioinhibitory group.The mixed pattern shared correlative features of the other two patterns.Conclusion:ABPM and the simplistic tilt test might be used as promising alternatives to the HUTT in VVS evaluation in clinical settings.

Characteristic of Ambulatory Blood Pressure in Normotensive Subjects With Type 2 Diabetes Mellitus

Objectives To observe the characteristic of ambulatory blood pressure monitoring in normotensive diabetic subjects with normoalbuminuria or microalbuminuria. Methods Fifty-two normotensive patients with type 2 diabetes received ambulatory blood pressure monitoring were divided into normoalbuminuric and microalbuminuric groups according to their albumin excretion rate, the other 28 normotensive subjects without diabetes were contributed as control group. Ambulatory blood pressure monitoring was performed on a working day and measurement of blood pressure circadian rhythm was analyzed. Results Normotensive microalbuminuric diabetic patients had higher night-time systolic blood pressure and more blood pressure burden than normotensive normoalbuminuric diabetic patients. Additionally, the microalbuminuric patients had a higher frequency of non-dippers than normoalbuminuric ones, although they were all normotensive. Compared to the normotensive non-diabetic control subjects, the night- time systolic blood pressure and frequency of non- dippers of the normoalbuminuric diabetic patients were significantly higher. Conclusions Intensive attention should be paid in control of blood pressure in diabetic patients to prevent and limit damage of target organ including kidney, even in those normotensive subjects.

Predictive performance of the variation rate of the driving pressure on the outcome of invasive mechanical ventilation in patients with acute respiratory distress syndrome

Purpose:To assess the value of the driving pressure variation rate(ΔP%)in predicting the outcome of weaning from invasive mechanical ventilation in patients with acute respiratory distress syndrome.Methods:In this case-control study,a total of 35 patients with moderate-severe acute respiratory distress syndrome were admitted to the intensive care unit between January 2022 and December 2022 and received invasive mechanical ventilation for at least 48 h were enrolled.Patients were divided into successful weaning group and failed weaning group depending on whether they could be removed from ventilator support within 14 days.Outcome measures including driving pressure,PaO2:FiO2,and positive end-expiratory pressure,etc.were assessed every 24 h from day 0 to day 14 until successful weaning was achieved.The measurement data of non-normal distribution were presented as median(Q1,Q3),and the differences between groups were compared by Wilcoxon rank sum test.And categorical data use the Chi-square test or Fisher's exact test to compare.The predictive value ofΔP%in predicting the outcome of weaning from the ventilator was analyzed using receiver operating characteristic curves.Results:Of the total 35 patients included in the study,17 were successful vs.18 failed in weaning from a ventilator after 14 days of mechanical ventilation.The cut-off values of the medianΔP%measured by Operator 1 vs.Operator 2 in the first 4 days were≥4.17%and 4.55%,respectively(p<0.001),with the area under curve of 0.804(sensitivity of 88.2%,specificity of 64.7%)and 0.770(sensitivity of 88.2%,specificity of 64.7%),respectively.There was a significant difference in mechanical ventilation duration between the successful weaning group and the failure weaning group(8(6,13)vs.12(7.5,17.3),p=0.043).The incidence of ventilator-associated pneumonia in the successful weaning group was significantly lower than in the failed weaning group(0.2‰vs.2.3‰,p=0.001).There was a significant difference noted between these 2 groups in the 28-day mortality(11.8%vs.66.7%,p=0.003).Conclusion:The medianΔP%in the first 4 days of mechanical ventilation showed good predictive performance in predicting the outcome of weaning from mechanical ventilation within 14 days.Further study is needed to confirm this finding.

CHARACTERISTCS OF FLUID FILM IN OPTIMIZED SPIRAL GROOVE MECHANICAL SEAL

In order to investigate the sealing performance variation resulted from the thermal deformation of the end faces, the equations to calculate the fluid film pressure distribution, the bearing force and the leakage rate are derived, for the fluid film both in parallel gap and in wedgy gap. The geometrical parameters of the sealing members are optimized by means of heat transfer analysis and complex method. The analysis results indicate that the shallow spiral grooves can generate hydrodynamic pressure while the rotating ring rotates and the bearing force of the fluid film in spiral groove end faces is much larger than that in the flat end faces. The deformation increases the bearing force of the fluid film in flat end faces, but it decreases the hydrodynamic pressure of the fluid film in spiral groove end faces. The gap dimensions which determine the characteristics of the fluid film is obtained by coupling analysis of the frictional heat and the thermal deformation in consideration of the equilibrium condition of the bearing force and the closing force. For different gap dimensions, the relation- ship between the closing force and the leakage rate is also investigated, based on which the leakage rate can be controlled by adjusting the closing force.

Evaluation of cilazapril in vasovagal syncope treatment

Objective: to evaluate cilazapril in vasovagal syncope treatment. Method: eighty\|six cases of VVS patients found positive in TTT tilt were medicated with 2.5 mg cilazapril daily for three months and followed up by TTT. Results: seven cases quit due to cough or unexplained reason; 79 VVS patients had no more fainting spells; 75.95% of TTT results of patients changed to negative after 3 months therapy. The before and after cilazapril treatment average blood pressures (taken in lying position) were 121/73 mm Hg (1 mm Hg= 0.133kPa) and 120/76 mm Hg respectively ( P > 0.05); and mean heart rates were 68.63±12.37/min and 70.13±13.15/min respectively with no significant changes ( P > 0.05). Conclusion: Cilazapril was effective in treatment of VVS; did not affect normal blood pressure and heart rate; was safe; and had little side effect.

Dynamic rock tests using split Hopkinson （Kolsky） bar system - A review

Dynamic properties of rocks are important in a variety of rock mechanics and rock engineering problems. Due to the transient nature of the loading, dynamic tests of rock materials are very different from and much more challenging than their static counterparts. Dynamic tests are usually conducted using the split Hopkinson bar or Kolsl^j bar systems, which include both split Hopkinson pressure bar （SHPB） and split Hopkinson tension bar （SHTB） systems. Significant progress has been made on the quantification of various rock dynamic properties, owing to the advances in the experimental techniques of SHPB system. This review aims to fully describe and critically assess the detailed procedures and principles of tech- niques for dynamic rock tests using split Hopkinson bars. The history and principles of SHPB are outlined, followed by the key loading techniques that are useful for dynamic rock tests with SHPB （i.e. pulse shaping, momentum-trap and multi-axial loading techniques）. Various measurement techniques for rock tests in SHPB （i.e. X-ray micro computed tomography （CT）, laser gap gauge （LGG）, digital image corre- lation （DIC）, Moir~ method, caustics method, photoelastic coating method, dynamic infrared thermog- raphy） are then discussed. As the main objective of the review, various dynamic measurement techniques for rocks using SHPB are described, including dynamic rock strength measurements （i.e. dynamic compression, tension, bending and shear tests）, dynamic fracture measurements （i.e. dynamic imitation and propagation fracture toughness, dynamic fracture energy and fracture velocity）, and dy- namic techniques for studying the influences of temperature and pore water.

Moisture effect on compressive behavior of concrete under dynamic loading

The effect of moisture content upon compressive mechanical behavior of concrete under impact loading was studied. The axial rapid compressive loading tests of over 50 specimens with five different saturations were executed. The technique "split Hopkinson pressure bar"(SHPB) was used. The impact velocity was 10 m/s with corresponding strain rate of 50 s-1. The compressive behavior of materials was measured in terms of stress-strain curves, dynamic compressive strength, dynamic increase factor(DIF) and critical strain at a maximum stress. The data obtained from test indicate that both ascending and descending portions of stress-stain curves are affected by moisture content. However, the effect is noted to be more significant in ascending portion of the stress-strain curves. Dynamic compressive strength is higher at lower moisture content and weaker at higher moisture content.Furthermore, under nearly saturated condition, an increase in compressive strength can be found. The effect of moisture content on the average DIF of concrete is not significant. The critical compressive strain of concrete does not change with moisture content.

In situ study of calcite-Ⅲ dimorphism using dynamic diamond anvil cell

The phase transitions among the high-pressure polymorphic forms of CaCO_(3)(cc-Ⅰ,cc-Ⅱ,cc-Ⅲ,and cc-Ⅲb)are investigated by dynamic diamond anvil cell(dDAC)and in situ Raman spectroscopy.Experiments are carried out at room temperature and high pressures up to 12.8 GPa with the pressurizing rate varying from 0.006 GPa/s to 0.056 GPa/s.In situ observation shows that with the increase of pressure,calcite transforms from cc-Ⅰto cc-Ⅱat~1.5 GPa and from cc-Ⅱto cc-Ⅲat~2.5 GPa,and transitions are independent of the pressurizing rate.Further,as the pressure continues to increase,the cc-Ⅲb begins to appear and coexists with cc-Ⅲwithin a pressure range that is inversely proportional to the pressurizing rate.At the pressurizing rates of 0.006,0.012,0.021,and 0.056 GPa/s,the coexistence pressure ranges of cc-Ⅲand cc-Ⅲb are 2.8 GPa-9.8 GPa,3.1 GPa-6.9 GPa,2.7 GPa-6.0 GPa,and 2.8 GPa-4.5 GPa,respectively.The dependence of the coexistence on the pressurizing rate may result from the influence of pressurizing rate on the activation process of transition by reducing the energy barrier.The higher the pressurizing rate,the lower the energy barrier is,and the easier it is to pull the system out of the coexistence state.The results of this in situ study provide new insights into the understanding of the phase transition of calcite.

Autonomic and cardiovascular effects of pentobarbital anesthesia during trigeminal stimulation in cats

Stimulation of the trigeminal nerve can elicit various cardiovascular and autonomic responses;however,the effects of anesthesia with pentobarbital sodium on these responses are unclear.Pentobarbital sodium was infused intravenously at a nominal rate and the lingual nerve was electrically stimulated at each infusion rate.Increases in systolic blood pressure（SBP） and heart rate（HR） were evoked by lingual nerve stimulation at an infusion rate between 5 and 7 mg？kg 21 ？h 21.This response was associated with an increase in the low-frequency band of SBP variability（SBP-LF）.As the infusion rate increased to 10 mg？kg 21 ？h 21 or more,decreases in SBP and HR were observed.This response was associated with the reduction of SBP-LF.In conclusion,lingual nerve stimulation has both sympathomimetic and sympathoinhibitory effects,depending on the depth of pentobarbital anesthesia.The reaction pattern seems to be closely related to the autonomic balance produced by pentobarbital anesthesia.

A new method for evaluating the injection effect of chemical flooding

Hall plot analysis,as a widespread injection evaluation method,however,often fails to achieve the desired result because of the inconspicuous change of the curve shape.Based on the cumulative injection volume,injection rate,and the injection pressure,this paper establishes a new method using the ratio of the pressure to the injection rate（RPI） and the rate of change of the RPI to evaluate the injection efficiency of chemical flooding.The relationship between the RPI and the apparent resistance factor（apparent residual resistance factor） is obtained,similarly to the relationship between the rate of change of the RPI and the resistance factor.In order to estimate a thief zone in a reservoir,the influence of chemical crossflow on the rate of change of the RPI is analyzed.The new method has been applied successfully in the western part of the Gudong 7th reservoir.Compared with the Hall plot analysis,it is more accurate in real-time injection data interpretation and crossflow estimation.Specially,the rate of change of the RPI could be particularly suitably applied for new wells or converted wells lacking early water flooding history.

Investigation of pressure loading rates on streaming potentials in bone

When load is applied to bone,it deforms and causes fluid pressure to build up in bone.The pressure gradient between different portions of the bone microcnannels drives fluid flow through them.This kind of bone fluid flow can induces the streaming potentials which are considered to play a role for bone remodeling.Aimed to determine the impact of ribbed rough inner surfaces of the microchannels on the streaming potentials,streaming potentials were measured as bone fluid flowed through the mcrospaces of thin cylinder bone samples under different pressure loading rates.The results show that the streaming potentials decrease with the increase of the pressure loading rates.A digital simulation calculation was performed and the results demonstrated that there were turbulent flows near the inner wall surfaces,which making the streaming potentials smaller in bone microchannels.

Dynamic characteristics of bubbling fluidization through recurrence rate analysis of pressure fluctuations

Pressure fluctuations signals of a lab-scale fiuidized bed （15 cm inner diameter and 2 m height） at different superficial gas velocities were measured. Recurrence plot （RP） and recurrence rate （RR）, and the simplest variable of recurrence quantification analysis （RQA） were used to analyze the pressure signals. Different patterns observed in RP reflect different dynamic behavior of the system under study. It was also found that the variance of RR （a2R） Could reveal the peak dominant frequencies （PDF） of different dynamic systems： completely periodic, completely stochastic, Lorenz system, and fluidized bed. The results were compared with power spectral density. Additionally, the diagram of σ^2RR provides a new technique for prediction of transition velocity from bubbling to turbulent fluidization regime.

Offshore fears and onshore risk: exchange rate pressures and bank volatility contagion in China

This paper shows that signals from the offshore China spot market for the Chinese renminbi of the Hong Kong SAR(listed as CNH)directly affect the volatility of share prices of Chinese banks and the overall risks of Chinese banking stability.This is especially so amid heightened uncertainty about global trade or the People’s Republic of China.Thus,the CNH market volatility is a leading indicator of onshore Chinese banking sector volatility.Our results suggest that further offshore exchange market movements arising out of news such as increasing trade friction with the United States will generate greater volatility in the Chinese banking sector.Far from being a shock absorber for the Chinese financial system,the CNH market appears to be a shock transmitter of risk from offshore economic policy uncertainty to the Chinese banking system.

Myocardial Oxygenation Response to Stress Performing a Single-set Compared to Volume-Matched Multiple-Set of Leg Press in Untrained Young Adults

Background Debates exist about the preference for single-or multiple-set resistance exercise(RE)on achieving similar training outcome,however,no study examined their effects on the heart,thus,this study was to examine the effect of volume-matched single-and multiple-set RE on the myocardial response through examining rate pressure product(RPP).Methods Fourteen healthy untrained college students performed two leg press exercises(4×10 and 1×40 at 150%body mass)on different days,and each was performed twice in a counterbalanced crossover order.Pre-and post-exercise SBP and HR were measured by auscultatory method,RPP was calculated as SBP×HR×10^(-3),RPP difference(RPPdiff)was calcu-lated by post-exercise RPP subtracting pre-exercise RPP.Results Single-set post-exercise RPP(17.48±3.16 mmHg·beats/min),HR(123.86±20.25 beats/min)was significantly greater than multiple-set post-exercise RPP(13.66±3.04 mmHg·beats/min),HR(101.61±19.14 beats/min),respec-tively.There was no significant difference of SBP(141.07±9.37 vs.134.29±15.16 mmHg)between exercise protocols(P=0.13).The RPPdiff of single-set(6.74±2.86 mmHg·beats/min)was significantly greater than that of multiple-set(3.62±2.90 mmHg·beats/min)(P<0.001).Conclusions Single-set RE exerts a greater myocardial oxygenation response as compared to multiple-set,HR contributed more than SBP to the increase of RPP in RE.The results indicate that single-set RE can be warranted when wanting to train the heart,while multiple-set RE would appear best for those who should avoid heart stress.

Escherichia coli inactivation by pressurized CO_2 treatment methods at room temperature: Critical issues

This study aims to increase the inactivation efficiency of CO_2 against Escherichia coli under mild conditions to facilitate the application of pressurized CO_2 technology in water disinfection. Based on an aerating-cycling apparatus, three different treatment methods（continuous aeration, continuous reflux, and simultaneous aeration and reflux） were compared for the same temperature, pressure（0.3–0.7 MPa）, initial concentration, and exposure time（25 min）. The simultaneous aeration and reflux treatment（combined method） was shown to be the best method under optimum conditions, which were determined to be 0.7 MPa, room temperature, and an exposure time of 10 min. This treatment achieved 5.1-log reduction after 25 min of treatment at the pressure of 0.3 MPa and 5.73-log reduction after 10 min at 0.7 MPa. Log reductions of 4.4 and 5.0 occurred at the end of continuous aeration and continuous reflux treatments at 0.7 MPa, respectively.Scanning electron microscopy（SEM） images suggested that cells were ruptured after the simultaneous aeration and reflux treatment and the continuous reflux treatment. The increase of the solubilization rate of CO_2 due to intense hydraulic conditions led to a rapid inactivation effect. It was found that the reduction of intracellular p H caused by CO_2 led to a more lethal bactericidal effect.

Dynamic mechanical behavior of ultra-high strength steel 30CrMnSiNi2A at high strain rates and elevated temperatures

During high speed machining in the field of manufacture,chip formation is a severe plastic deformation process including large strain,high strain rate and high temperature.And the strain rate in high speed cutting process can be achieved to 105 s^（-1）.30CrMnSiNi2Asteel is a kind of important high-strength low-alloy structural steel with wide application range.Obtaining the dynamic mechanical properties of30CrMnSiNi2Aunder the conditions of high strain rate and high temperature is necessary to construct the constitutive relation model for high speed machining.The dynamic compressive mechanical properties of30CrMnSiNi2Asteel were studied using split Hopkinson pressure bar（SHPB）tests at 30-700°C and3000-10000s^（-1）.The stress-strain curves of 30CrMnSiNi2Asteel at different temperatures and strain rates were investigated,and the strain hardening effect and temperature effect were discussed.Experimental results show that 30CrMnSiNi2Ahas obvious temperature sensitivity at 300°C.Moreover,the flow stress decreased significantly with the increase of temperature.The strain hardening effect of the material at high strain rate is not significant with the increase of strain.The strain rate hardening effect is obvious with increasing the temperature.According to the experimental results,the established Johnson-Cook（J-C）constitutive model of 30CrMnSiNi2Asteel could be used at high strain rate and high temperature.

An Infrared Touch System for Automatic Behavior Monitoring

Key requirements of successful animal behavior research in the laboratory are robustness,objectivity,and high throughput,which apply to both the recording and analysis of behavior.Many automatic methods of monitoring animal behavior meet these requirements.However,they usually depend on high-performing hardware and sophisticated software,which may be expensive.Here,we describe an automatic infrared behavior-monitor(AIBM)system based on an infrared touchscreen frame.Using this,animal positions can be recorded and used for further behavioral analysis by any PC supporting touch events.This system detects animal behavior in real time and gives closed-loop feedback using relatively low computing resources and simple algorithms.The AIBM system automatically records and analyzes multiple types of animal behavior in a highly efficient,unbiased,and low-cost manner.