Experimental research into the effect of gas pressure,particle size and nozzle area on initial gas-release energy during gas desorption

Coal and gas outburst is a violent disaster driven by released energy from gas desorption.The initial expansion energy of released gas(IEERG)is a new method to predict coal and gas outburst.In this paper,an instrument for IEERG measurement was developed.Compared with previous setups,the new one which is equipped with three convergent nozzles and quick-release mechanism gets improved in data acquisition and gas sealing and releasing performance.To comprehensively know the effect of gas pressure,particle size,and nozzle area on IEERG,a series of experiments were carried out with this new setup.The variable control test results indicated that the gas pressure-IEERG curves remain the linear trend and the particle size-IEERG curves maintain the negative exponential trend for nozzle areas at 1.13,2.26,and3.39 mm2,respectively.The increase in nozzle area leads to deceases in value of IEERG and absolute value of slope of fitting curves in each test.In addition,the orthogonal experiment showed that the influence of gas pressure,nozzle area,and particle size on IEERG decreases in turn.Only gas pressure had a marked impact on IEERG.This work offers great importance in improving the accuracy of prediction of coal and gas outburst.

Stress release mechanism of deep bottom hole rock by ultra-high-pressure water jet slotting

To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom hole rock,before and after slotting are analyzed and the stress release mechanism of slotting is clarified.The results show that the stress release by slotting is due to the coupling of three factors:the relief of horizontal stress,the stress concentration zone distancing away from the cutting face,and the increase of pore pressure caused by rock mass expansion;The stress concentration increases the effective stress of rock along the radial distance from O.6R to 1R(R is the radius of the well),and the presence of groove completely releases the stress,it also allows the stress concentration zone to be pushed away from the cutting face,while significantly lowering the value of stresses in the area the drilling bit acting,the maximum stress release efficiency can reach 80%.The effect of slotting characteristics on release efficiency is obvious when the groove location is near the borehole wall.With the increase of groove depth,the stress release efficiency is significantly increased,and the release range of effective stress is enlarged along the axial direction.Therefore,the stress release method and results of simulations in this paper have a guiding significance for best-improving rock-breaking efficiency and further understanding the technique.

Airway Pressure Release Ventilation Improves Oxygenation in a Patient with Pulmonary Hypertension and Abdominal Compartment Syndrome

The following case describes the favorable application of airway pressure release ventilation (APRV) in a patient with pulmonary hypertension who developed respiratory failure and abdominal compartment syndrome after abdominal closure from an incarcerated umbilical hernia. A 66-year-old male with past medical history of restrictive lung disease, obstructive sleep apnea and pulmonary hypertension, presented to the operating room for an incarcerated inguinal hernia. After abdominal closure, he gradually developed decreased oxygen saturation and hypotension. APRV was initiated during post operative day 2 after inability to maintain adequate oxygen saturation with resultant hypotension on pressure control ventilation with varying degrees of positive end expiratory pressure and 100% inspired oxygen concentration. The initial set high pressure on APRV was 35 mm Hg. Yet, in lieu of decreasing lung compliance, it peaked at 50 mm Hg. Eventually, inhaled Nitric Oxide was initiated post operative day 3 due to increasing pulmonary arterial pressures. A bedside laparotomy was eventually performed when bladder pressures peaked to 25 mm Hg. APRV gradually and temporally improved the oxygen saturation and decreased the pulmonary arterial pressures with subsequent increase in systemic blood pressures. APRV promoted alveolar recruitment and decreased the shunting associated with abdominal compartment syndrome. Better oxygen saturations lead to increases in blood pressure by decreasing the effects of hypoxic pulmonary vasoconstriction on the right ventricle (RV). In patients with decreasing lung compliance and pulmonary comorbidities, APRV appears safe and allows for improve oxygenation, after failure with conventional modes of ventilation.

The Impact of Different Mining and Releasing Ratios on the Over-Support Pressure of Header Working Face

Through the theoretical analysis of overburden destabilization mechanism, FLAC 3D simplified plane numerical simulation method and field measurement method, we compared the relationship of overburden support pressure at 35 m of workface recovery, and the peak overburden support pressure decreased from 13.85 Mpa to 11.97 Mpa from 1:1 to 1:3. With the increase of mining ratio, the peak over-supporting pressure decreases: with the increase of top coal recovery thickness, the peak over-supporting pressure and the influence range will be further expanded, and the distance between the peak over-supporting pressure and the coal wall of the working face will be further increased and the high stress zone of the peak area will be expanded simultaneously.

Tunnel design considering stress release effect

In tunnel design, the determination of installation time and the stiffness of supporting structures is very important to the tunnel stability. This study used the convergence-confinement method to determine the stress and displacement of the tunnel while considering the counter-pressure curve of the ground base, the stress release effect, and the interaction between the tunnel lining and the rock surrounding the tunnel chamber. The results allowed for the determination of the installation time, distribution and strength of supporting structures. This method was applied to the intake tunnel in the Ban Ve Hydroelectric Power Plant, in Nghe An Province, Vietnam. The results show that when a suitable displacement u0 ranging from 0.0865 m to 0.0919 m occurrs, we can install supporting structures that satisfy the stability and economical requirements.

Delamination growth for composite laminated cylindrical shells under external pressure

The delamination growth may occur in delaminated cylindrical shells＇under external pressure. This will lead to failure of structure. By using the variational principle of moving boundary and considering the contact effect between delamination regions, in this work, the delamination growth was investigated for cylindrical shells under the action of external pressure. At the same time, according to the Griffith criterion, the formulas of energy release rate along the delamination front were obtained. In the numerical calculation, the delamination growth of axisymmetrical laminated cylindrical shells was analyzed, and the effects of delamination sizes and depths, the geometrical parameters, the material properties, and the laminate stacking sequences on delamination growth were discussed.

硝苯地平控释片联合缬沙坦在原发性高血压中的应用价值

目的探讨硝苯地平控释片联合缬沙坦在原发性高血压中的临床应用价值。方法选择2023年11月至2024年3月本院收治的单纯原发性高血压患者80例。按照随机数字表法分为两组,各40例。对照组口服硝苯地平控释片,观察组联用缬沙坦片。比较两组治疗前后胱抑素-C水平变化,统计两组治疗后心脏彩超左室射血分数及肾功能指标变化,统计两组血压达标情况及不良反应。结果治疗前两组胱抑素-C水平比较无统计学意义(P>0.05),治疗后观察组胱抑素-C水平低于对照组(P<0.05)。观察组左室射血分数高于对照组,尿素氮和血肌酐水平均低于对照组(P<0.05)。观察组随机血压、诊室血压及动态血压达标率均高于对照组(P<0.05)。两组均未出现低钾血症、恶心呕吐、咳嗽、外周水肿等不良反应。结论针对原发性高血压患者,在使用硝苯地平控释片基础上联合缬沙坦治疗,可有效提高左室射血分数,改善肾功能,促使血压快速达标,且不良反应少,安全性高。

Does airway pressure release ventilation offer new hope for treating acute respiratory distress syndrome?

Mechanical ventilation(MV)is an essential life support method for patients with acute respiratory distress syn-drome(ARDS),which is one of the most common critical illnesses with high mortality in the intensive care unit(ICU).A lung-protective ventilation strategy based on low tidal volume(LTV)has been recommended since a few years;however,as this did not result in a significant decrease of ARDS-related mortality,a more optimal venti-lation mode was required.Airway pressure release ventilation(APRV)is an old method defined as a continuous positive airway pressure(CPAP)with a brief intermittent release phase based on the open lung concept;it also perfectly fits the ARDS treatment principle.Despite this,APRV has not been widely used in the past,rather only as a rescue measure for ARDS patients who are difficult to oxygenate.Over recent years,with an increased under-standing of the pathophysiology of ARDS,APRV has been reproposed to improve patient prognosis.Nevertheless,this mode is still not routinely used in ARDS patients given its vague definition and complexity.Consequently,in this paper,we summarize the studies that used APRV in ARDS,including adults,children,and animals,to illustrate the settings of parameters,effectiveness in the population,safety(especially in children),incidence,and mechanism of ventilator-induced lung injury(VILI)and effects on extrapulmonary organs.Finally,we found that APRV is likely associated with improvement in ARDS outcomes,and does not increase injury to the lungs and other organs,thereby indicating that personalized APRV settings may be the new hope for ARDS treatment.

RELATIONSHIP BETWEEN EFFECT OF PRESSURE RELEASE ON DEPOSITS AND MINERALIZATION OF PORPHYRY COPPER

Duobaoshan copper deposit is an important porphyry copper deposit in nothern China. The mineralization of deposit is closely related to tectonic movement, almost all orebodies of the deposit are distributed in the original biotitization zone. The more copper mineralization concentration, the more schistosity and structural cracks. Mineralization occurs when it changes from a dosed system to an open ore,

Sustained release of brimonidine from polydimethylsiloxane-coating silicone rubber implant to reduce intraocular pressure in glaucoma

Glaucoma is the leading cause of irreversible blindness,affecting 111 million people by 2040 worldwide.Intraocular pressure(IOP)is the only controllable risk factor for the disease and current treatment options seek to reduce IOP via daily taking eye drops.However,shortcomings of eye drops,such as poor bioavailability and unsatisfied therapeutic effects,may lead to inadequate patient compliance.In this study,an effective brimonidine(BRI)-loaded silicone rubber(SR)implant coated with polydimethylsiloxane(BRI@SR@PDMS)is designed and fully investigated for IOP reduction treatment.The in vitro BRI release from BRI@SR@PDMS implant reveals a more sustainable trend lasting over 1 month,with a gradually declined immediate drug concentration.The carrier materials show no cytotoxicity on human corneal epithelial cells and mice corneal epithelial cells in vitro.After administrated into rabbit’s conjunctival sac,the BRI@SR@PDMS implant releases BRI in a sustained fashion and effectively reduces IOP for 18 days with great biosafety.In contrast,BRI eye drops only maintain IOP-lowering effect for 6 h.Therefore,as a substitute of eye drops,the BRI@SR@PDMS implant can be applied as a promising non-invasive platform to achieve long-term IOP-lowering in patients suffering from ocular hypertension or glaucoma.

Release models for leaks from high-pressure hydrogen storage systems

Simulations and analyses of experimental data from leaks from high-pressure hydrogen storage systems will require knowledge of the stagnation state time histories and stream properties exiting the orifices.An analytical ideal-gas model based on the ideal gas state equation and a computer program making use of the NIST standard reference database(REFPROP)were developed to model the entire process of leaks from high-pressurized hydrogen gas containers.The results obtained by the two methods agree with each other well.As the gas behavior departs from the ideal gas properties at high pressures,the actual stagnation pressure and temperature decay more rapidly than with the ideal-gas assumption.

Airway pressure release ventilation forin-vivodonor lung management and lung transplant outcomes

Background:Airway pressure release ventilation(APRV)can be used for cadaveric donor lung recruitment.APRV elevates PaO_(2)in donor lungs;however,reported outcomes in recipients with APRVmanaged donor lungs are limited.Methods:We retrospectively reviewed patients who underwent lung transplantation(LTx)from 2012 to 2013 and divided them into two groups based on mode of ventilation used during donor management and organ extraction(A:non-APRV;B:APRV).Kaplan-Meier method and multivariate Cox regression were used for analysis.Results:We found 126 LTx recipients(LTxRs);9 were excluded for use of portable ventilation perfusion systems.Of the remaining 117 patients,81(69%)were in Group A;36(31%)were in Group B.Preoperative LTxR characteristics(age,sex,lung allocation score,endstage lung disease type)were comparable between groups.Donors for Group B were older(P=0.03)and had higher body mass index(BMI)(P<0.001),higher incidence of death from chest trauma(P=0.008),longer ventilation duration after brain death(P<0.001),and higher pre-explant PaO_(2)/FiO_(2)ratios(P<0.001).Post-LTx duration of mechanical ventilation,hospital stay,and median survival were similar in both groups.Risk of death was comparable between the two groups at the end of follow-up(HR=1.42;95%CI:0.57-3.56;P=0.45).Conclusions:APRV is a safe and effective pre-LTx donor lung management strategy.Short-and long-term survival outcomes were comparable in LTx recipients,irrespective of donor ventilation mode.APRV may help recruit lungs from older donors with higher BMI who die from chest trauma and have anticipated longer ventilation duration.

极近距离煤层开采无煤柱自成巷控制方法研究

极近距离煤层传统长壁开采,受上层遗留煤柱和采空区垮落等因素的影响,下煤层开采过程中应力环境复杂、矿压显现剧烈,易诱发巷道围岩大变形。为解决上述问题,提出了极近距离条件下巷道定向切顶–约束高强支护无煤柱自成巷控制方法。通过顶板定向预裂切顶,主动改变顶板悬臂结构,切断采空区向巷道顶板的应力传递。充分利用矿山压力和岩体碎胀特性,取消煤柱留设,结合高强支护加强巷道顶板整体性,共同实现切顶自成巷。建立了极近距离煤层开采覆岩结构模型,计算了下煤层切顶自成巷巷旁支护阻力。以典型极近距离煤层为工程背景,开展了不同开采方法的数值试验对比研究,结果表明,提出的自成巷控制方法使巷道围岩应力降低59.8%,巷道顶板变形减少70.8%,并明确了极近距离煤层开采无煤柱自成巷控制机理。在此基础上,开展了典型极近距离煤层工程设计及现场应用研究,结果表明该方法有效降低了矿压显现程度,保证了自成巷的安全稳定控制。

西维来司他钠联合气道压力释放通气治疗创伤所致重度ARDS的临床疗效观察

目的探讨西维来司他钠、气道压力释放通气治疗由创伤导致重度急性呼吸窘迫综合征(ARDS)的疗效。方法选取南阳市中心医院2020年1月至2022年12月期间收治80例重度ARDS患者,依照随机抽签的方法分成两组,各40例。对照组应用气道压力释放通气治疗,观察组在此基础上加用西维来司他钠,比较两组血气、炎性因子、血流动力学指标和预后。结果治疗前,两组动脉二氧化碳分压(PaCO_(2))、动脉氧分压(PaO_(2))、PaO_(2)/吸入氧浓度(FiO_(2))值比较,差异无统计学意义(P>0.05);治疗24 h、治疗72 h后,两组PaCO_(2)值均低于治疗前,PaO_(2)、PaO_(2)/FiO_(2)值均高于治疗前,且观察组PaCO_(2)值低于对照组,观察组PaO_(2)、PaO_(2)/FiO_(2)值高于对照组,差异有统计学意义(P<0.05)。治疗前,两组白细胞介素-6(IL-6)、降钙素原(PCT)、C反应蛋白(CRP)值比较,差异无统计学意义(P>0.05);治疗后,两组IL-6、PCT、CRP值均低于治疗前,且观察组IL-6、PCT、CRP值均低于对照组,差异有统计学意义(P<0.05)。治疗前,两组中心静脉压(CVP)、心率(HR)、平均动脉压(MAP)值比较,差异无统计学意义(P>0.05);治疗24 h、治疗72 h后,对照组CVP、HR、MAP值均低于治疗前,观察组HR低于治疗前,MAP治疗24 h低于治疗前,差异有统计学意义(P<0.05);治疗24 h、治疗72 h后,观察组CVP、HR、MAP值均高于对照组,差异有统计学意义(P<0.05)。治疗前,两组急性生理和慢性健康状况(APACHEⅡ)评分比较,差异无统计学意义(P>0.05);治疗后,两组APACHEⅡ评分均低于治疗前,且观察组低于对照组,差异有统计学意义(P<0.05)。结论西维来司他钠、气道压力释放通气治疗创伤所致重度ARDS成效佳,能改善血气、炎性因子及血流动力学指标,提高预后。

厚煤层沿空留巷变形漏风机制及多元协同防治技术

为解决厚煤层沿空留巷墙体变形机理及采空区漏风流场不清、瓦斯防治效果不佳的问题,以山西沁城煤矿20107工作面为工程背景,采用力学建模、理论分析研究了沿空留巷顶板断裂位置对应力集中及传播路径的控制作用,并指出断裂线位于留巷外侧时,可有效转移支撑应力并卸压,并提出了分段压裂切顶关键位置的计算方法。采用单元法实测,从采空区漏风量分布及留巷漏风通道两方面,揭示了沿空留巷采空区漏风流场及瓦斯浓度分布规律,进而提出了沿空留巷采空区瓦斯多元防治技术,即采用定向钻孔分段压裂切顶卸压-强化瓦斯抽采超前协同共治为主,弱化转移顶板来压避免墙体变形产生裂隙漏风的同时提高采空区瓦斯抽采效率;采用硅酸盐复合材料对已有墙体裂隙发育区(顶板交界处、插管外壁周围)进行喷涂堵漏,封堵留巷漏风通道;辅以留巷插管参数优化及控风降压,进一步减小采空区漏风及瓦斯涌出,并通过现场考察验证。研究结果表明:①20107采空区漏风以运输巷进风流正压漏入为主、回风侧以高浓瓦斯漏入沿空留巷为主,工作面倾向0~36 m区段正压漏风量332.84 m^(3)/min,占工作面总体漏入采空区风量(572.15 m^(3)/min)58.17%;留巷走向54~108 m区段留巷漏入风量408.45 m^(3)/min,占采空区总体漏入沿空留巷风量(469.01 m^(3)/min)87.09%;②优化后,裂隙带定向钻孔(压裂孔+抽采孔)平均瓦斯抽采纯量为7.46 m^(3)/min,压裂切顶后留巷墙体变形、裂隙控制大幅改善,沿空留巷平均瓦斯体积分数由原0.59%逐渐降至0.34%,实现工作面高效达产。

高炉放散煤气治理技术

总结了高炉均压放散煤气和休风放散煤气治理技术的研究进展和应用情况。高炉均压放散煤气干法回收技术自2014年起逐步在京津冀地区率先获得推广应用至今,经过多次迭代更新,最终形成了“三级除尘+高效引射+智能控制”的引射法均压煤气干法全回收技术,该技术成熟可靠,已在国内多数高炉上获得成功应用。对于高炉休风放散煤气治理技术的研究仍处于发展阶段,当前的主流技术路线是利用现有煤气净化设施,通过在调压阀组区域并联引射器,对高炉休风末期、炉顶放散阀开启前的炉内低压煤气强制回收进入管网,可实现休风煤气全量回收,达到应收尽收,在休风结束时,高炉炉顶放散阀开启前,炉顶压力可降至0~1 kPa。但该技术仅适用于长期休风和短期休风,不适用于降料线休风和事故紧急休风。鉴于高炉休风过程的煤气回收操作是一项危险性作业,对休风放散煤气的治理还需在确保安全的前提下谨慎选择。选择技术方案时,需要综合考虑节能环保、投资、运行维护成本对高炉生产的影响以及系统是否能安全可靠运行等多方面的因素,采用性价比高的技术实现钢铁企业的长期绿色发展。

差压步进钻头提高破岩速度原理及现场试验

井底岩石承受较大的原地应力作用,且随着井深增加原地应力呈增大趋势。原地应力的存在增加了岩石的压实程度,导致岩石坚硬、可钻性差、研磨性强等问题,成为破岩工具切削效率低、使用寿命短和钻井速度慢的最主要原因之一。针对此背景,提出释放井底部分原地应力弱化地层抗钻特性提高破岩速度的理念,研发一种可释放井底部分原地应力弱化地层抗钻特性且能够集中钻压强化攻击能力的差压步进钻头,该钻头充分利用钻井过程中的井底钻压波动,实现扩眼钻头与领眼钻头钻压动态分配及钻进过程交替进行的目标,通过弱化地层、强化攻击及转化振动三重效果提高破岩速度。为验证差压步进钻头的应力释放效应,建立三维流固耦合的阶梯井底应力场模型,并在江苏油区某区块砾石层井段开展3口井的实钻试验。结果表明:阶梯井底能够使阶梯处岩石更易破碎;小直径领眼钻头应力释放效果较好;随着地层深度的增加,差压步进钻头应力释放效果更加显著,应力释放比约为60.2%;差压步进钻头提速效果显著,砾石层钻速较牙轮钻头提升可达161.89%,最高提速318.11%。

阿替普酶静脉溶栓联合硝苯地平缓释片对急性缺血性脑卒中患者血压控制及神经功能的影响

目的:探讨阿替普酶静脉溶栓联合硝苯地平缓释片治疗对急性缺血性脑卒中(AIS)患者血压控制及神经功能的影响。方法:选取104例AIS患者为研究对象,按照治疗方式不同分为对照组和联合组,每组各52例。对照组患者给予阿替普酶静脉溶栓治疗;观察组患者给予阿替普酶静脉溶栓联合硝苯地平缓释片治疗,疗程均为3个月。比较两组患者血压变化、神经功能[神经功能缺损(NIHSS)评分]、日常功能恢复情况[巴氏日常生活活动能力量表(Barthel)指数评分、改良Rankin量表(mRS)评分]及不良反应发生情况。结果:治疗前及治疗后1 h,两组患者血压比较,差异无统计学意义(P>0.05)。治疗后6、24 h及7 d,联合组患者收缩压和舒张压均低于对照组(P<0.05)。治疗后7 d,两组患者NIHSS评分均降低(P<0.05),且联合组低于对照组(P<0.05)。治疗后24 h及3个月,两组患者Barthel指数评分均升高(P<0.05),且联合组各时间点均高于对照组(P<0.05);mRS评分均降低(P<0.05),且联合组各时间点均低于对照组(P<0.05)。两组患者不良反应总发生率比较,差异无统计学意义(28.85%vs.25.00%,P>0.05)。结论:阿替普酶静脉溶栓联合硝苯地平缓释片治疗AIS患者可改善血压控制能力及神经功能,且有较好的安全性。

煤层厚度影响下大直径钻孔卸压释能机理

煤层厚度变化是影响大直径钻孔卸压效果的重要因素之一。基于等效弹性模量原理建立了大直径钻孔卸压弹性力学模型,以某矿不同工作面为工程背景,研究了不同煤层厚度条件下大直径钻孔卸压煤体应力分布特征和能量释放规律,探讨了煤层厚度影响下大直径钻孔卸压释能机理。研究结果表明:当大直径钻孔卸压参数相同时,薄煤层中原岩应力、钻孔切向应力及其塑性区范围均大于厚煤层;大直径钻孔周边应力峰值随煤层厚度增加呈非线性减小趋势,当煤层厚度由1 m增加到9 m,应力峰值由23.2 MPa降低到20.2 MPa,降低12.9%;大直径钻孔卸压释能率随着煤层厚度增加呈减小趋势,当煤层厚度由1 m增加到9 m,大直径钻孔卸压释能率由68.7%降低到45.8%,即相同大直径钻孔卸压参数条件下薄煤层卸压效果更好;当大直径钻孔卸压参数相同时,钻孔切向应力随着煤层厚度增加而减小,导致煤体破碎区和塑性区范围以及存储弹性能释放量减小,即钻孔卸压释能率降低。某矿1208工作面和1203工作面煤层厚度分别为9.08、4.95 m,虽然两工作面采取了相同的大直径钻孔参数,但1208工作面巷道围岩变形破坏更为严重,对大直径卸压钻孔参数优化后,煤体平均钻屑量由2.48 kg/m下降到1.76 kg/m,表明随着煤层厚度增加,需采取减小钻孔间距、增大钻孔直径等措施来达到更好的卸压效果。

排气道压力波动对发动机二冲程减压制动性能的影响

为分析排气管内压力波动对发动机二冲程制动功率的影响,以某重型柴油机为研究对象,利用GT-Power建立发动机二冲程制动一维模型,通过修改排气型线开展排气道压力波动对制动性能影响的研究。结果表明:第二次减压制动(the second compression release braking,2nd CRB)相位开启时的压力波动会影响到其他气缸的排气回流,进而影响发动机的制动功率。进一步对排气管进行三维流场计算,证明了其他气缸2nd CRB相位排气门开启时的压力波传递对排气回流阶段排气回流的影响。最后通过试验设计(design of experiment,DoE),结合响应面拟合和粒子群算法对排气管几何尺寸进行优化,优化后该柴油机二冲程减压制动模式下2100 r/min工况的最大制动功率可达到395.08 kW。