Long-term decay of the water pressure in the osmotic tensiometer

Matric suction is an important state variable required for the assessment of unsaturated soil properties.Tensiometers are commonly used for direct matric suction measurement but have a limited measuring range up to 90 kPa due to the cavitation problem.Osmotic tensiometer(OT)can improve the measuring range of tensiometers by increasing the osmotic pressure of water to avoid the cavitation.However,the long-term water pressure decay that appeared in OTs caused a gradual decrease in their measuring range.In this study,crosslinked poly(acrylamide-co-acrylic acid)potassium salt(PAM-co-PAAK)was used for the preparation of OTs(five in total)to explore the mechanism of water pressure decay of OTs.The maximum water pressure in the OT versus the volume fraction of polymer filled in the OT was described based on the Flory-Huggins polymer theories and validated using WP4C dewpoint hygrometer.The long-term pressure decay of OT-1,OT-2,and OT-3 was observed for 130 d and constant pressures were found for OT-1 and OT-2,indicating that the pressure decay of OT was mainly caused by the stress relaxation of the polymer hydrogels,and standard linear solid(SLS)rheological model was appropriate to fit the decay data.For OT-1,OT-2 and OT-3,the theoretical osmotic pressure that was calculated based on the mass of retrieved polymer from OTs after 130-d pressure observation was higher than the actual osmotic pressure as observed,indicating that polymer leakage cannot explain the pressure decay of the OT.The ultravioletevisible(UVevisible)spectrophotometry examined the change in polymer concentrations in the water containers of OT-4 and OT-5 and demonstrated that there was no increase in polymer leakage during the period of pressure decay of OT-4 and OT-5.As a result,the pressure decay of OT was not caused by polymer leakage.The results of this research suggested that the viscoelastic properties of polymers should be taken into consideration in further OT development.

Effect of holding pressure on density and cooling rate of cast Al-Si alloy during additive pressure casting

The cast Al-Si alloy was fabricated using the Additive Pressure Casting(APC)method.The effects of holding pressure from 50 to 400 k Pa on the density,cooling rate,and mechanical properties of the alloy,and the corresponding mechanism were discussed.The results indicate that the application of high holding pressure(300 k Pa)enhances the feeding ability of the alloy,leading to an increase of the density.Meanwhile,the cooling rate of the alloy is increased by 100%.In addition,the tensile testing results show that the increase of holding pressure from 50 to 300 k Pa improves the tensile strength and elongation of the alloy by 6.2%and 81.3%,respectively.However,excessive holding pressure(400 k Pa)might lower the density and cooling rate of the alloy due to the feeding channels being blocked.

Psychological stress and long-term blood pressure variability of military young males:The cardiorespiratory fitness and hospitalization events in armed forces study

BACKGROUND Acute stress might increase short-term heart rate variability and blood pressure variability(BPV);however,chronic stress would not alter short-term BPV in animal models.AIM To examine the association of psychological stress with long-term BPV in young male humans.METHODS We prospectively examined the association of chronic psychological stress with long-term BPV in 1112 healthy military males,averaged 32.2 years from the cardiorespiratory fitness and hospitalization events in armed forces study in Taiwan.Psychological stress was quantitatively evaluated with the Brief Symptom Rating Scale(BSRS-5),from the least symptom of 0 to the most severe of 20,and the five components of anxiety,insomnia,depression,interpersonal sensitivity,and hostility(the severity score in each component from 0 to 4).Longterm BPV was assessed by standard deviation(SD)for systolic and diastolic blood pressure(SBP and DBP),and average real variability(ARV),defined as the average absolute difference between successive measurements of SBP or DBP,across four visits in the study period from 2012 to 2018(2012-14,2014-15,2015-16,and 2016-18).RESULTS The results of multivariable linear regressions showed that there were no correlations of the BSRS-5 score with SDSBP,SDDBP,ARVSBP,and ARVDBP after adjusting for all the covariates[β(SE):-0.022(0.024),-0.023(0.026),-0.001(0.018),and 0.001(0.020),respectively;P>0.05 for all].In addition,there were also no correlations between each component of the BSRS score and the long-term BPV indexes.CONCLUSION Our findings suggest that chronic psychological stress might not be associated with long-term BPV in military young male humans.

The effect of high-pressure and high-temperature drying treatments on the deresination ratio of Pinus massoniana

This study investigated the possibility of using high-temperature and high-pressure schedules to treat Pinus massoniana wood in order to reduce its oil content. We discuss the effect of drying temperature, absolute pressure and the holding time on the deresination ratio in R massoniana wood and establish a model for the deresination ratio as a function of drying temperature, absolute pressure and holding time. The results show that the deresination ratio in- creased from 7.14% to 87.04% when the temperature increased from 150 to 200℃, the absolute pressure from 0.1 to 0.6 MPa and the holding time from 1 to 3 h. The optimal model for the deresination ratio （Y） with drying temperature （t）, absolute pressure （p） and holding time （r） is： Y = 0.284t ＋ 113.424p ＋ 3.518r - 42.486, with a coefficient of determina- tion （R2） of 0.930. Compared with drying temperature and holding time, absolute pressure plays the more significant role in the deresination process. This study could provide a theoretical basis to the practical production of R massoniana wood.

老年人群24h动态血压监测中清晨高血压与脑血管储备功能相关性

目的研究老年人群24 h动态血压监测中清晨高血压与脑血管储备功能(CVR)的相关性。方法回顾性选取2021年1月至12月到济南市妇幼保健院行24 h动态血压监测的300例老年受试者,依据监测结果分为A组、B组和C组。A组158例为清晨血压升高的高血压患者,男88例,女70例,年龄(66.02±4.35)岁;B组74例为清晨血压正常的高血压患者,男41例,女33例,年龄(65.42±4.42)岁;C组68例为血压正常者,男37例,女31例,年龄(65.77±4.38)岁。以两侧大脑中动脉屏气指数均值<0.69%为CVR减低,屏气指数均值≥0.69%为CVR正常,将300例受试者分为CVR降低组(52例)和CVR正常组(248例)。比较A、B、C 3组患者的临床资料,CVR指标;比较CVR降低组、CVR正常组一般资料,行单因素分析、多因素分析和相关性分析。采用F检验、独立样本t检验、χ^(2)检验、logistic回归分析和Pearson相关性分析。结果300例24 h动态血压监测的老年受试者,清晨血压升高的高血压患者158例,占52.67%;清晨血压正常的高血压患者74例,占24.67%;血压正常者68例,占22.67%。3组收缩压(24 h均值、日间均值、夜间均值)、晨峰指数:A组>B组>C组(均P<0.05);舒张压(24 h均值、日间均值、夜间均值):A组>B组、C组(均P<0.05),B组、C组舒张压比较,差异均无统计学意义(均P>0.05)。CVR:A组[(21.37±7.89)%]<B组[(25.58±8.14)%]<C组[(28.56±8.10)%](均P<0.05);屏气指数:A组[(0.89±0.23)%]<B组[(1.13±0.21)%]、C组[(1.20±0.24)%](均P<0.05),B组、C组屏气指数比较,差异无统计学意义(P>0.05);脉动指数:A组[(1.49±0.36)]>B组[(1.15±0.31)]、C组[(1.06±0.29)](均P<0.05),B组、C组脉动指数比较,差异无统计学意义(P>0.05)。CVR降低组年龄[(73.14±3.21)岁]、清晨收缩压[(132.42±9.64)mmHg](1 mmHg=0.133 kPa)、清晨舒张压[(68.85±6.59)mmHg]均高于CVR正常组[(64.28±4.36)岁、(121.58±7.26)mmHg、(65.36±7.23)mmHg](均P<0.05)。logistic回归分析结果显示:年龄、清晨收缩压、清晨舒张压均为CVR降低的影响因素(均P<0.05)。清晨收缩压与屏气指数呈负相关(P<0.05),与脉动指数呈正相关(P<0.05);清晨舒张压与屏气指数呈负相关(P<0.05),与脉动指数呈正相关(P<0.05)。结论老年人群24 h动态血压监测中清晨高血压患者占比较大,清晨高血压患者CVR、屏气指数较低,脉动指数较高,清晨收缩压、清晨舒张压均与屏气指数呈负相关,与脉动指数呈正相关。

过滤器容尘过程对房间负压、风量的影响研究

以某工程固化线通风系统为例,利用FLoMASTER软件建立了固化线排风管网一维水力平衡模型。根据过滤器容尘过程中的阻力特性曲线,模拟分析了固化线房间负压和风量随容尘量的变化。针对容尘过程中造成的固化线房间负压、风量不满足规范和设计要求的情况,提出了相应的调节措施,为后续调试和运行提供依据。

基于三维实体模型的注塑成型保压过程模拟

基于现有的超算平台和有限体积法计算程序,开发基于三维实体模型的注塑成型数值模拟计算模型。基于可压缩两相流模型进行计算,采用有限体积法进行离散,结合流体体积法(VOF)进行界面捕获,使用Cross-WLF黏性模型表征聚合物熔体的流变行为。以平板型腔和带圆柱嵌件型腔熔体保压过程为例进行数值模拟计算,成功预测型腔压力、温度和应力等流动特性的分布,模拟结果与文献中的结果基本吻合。

高压电器产品中铜套冷装、压装与粘接的对比应用

铝青铜铜套具有较高强度、导热性、耐磨性及耐腐蚀性等优点,在高压电器产品中广泛应用,但在工程使用过程中,生产装配现场反馈部分小直径铜套有窜出现象。经分析,铜套窜出主要是受剪应力及滑动摩擦力影响产生的滑移现象,为进一步提升装配质量,综合材料特性、结构强度、可制造性、经济性等方面,在不改变原装配结构条件下,选择冷装、压装、粘接3种连接方式开展工艺研究。通过验证,使用压装与粘接复合工艺可提供更高的固持力,并提出一种在过盈配合基础上发挥粘接效果的设计结构,有效减小径向压力产生的摩擦力。

Long-term results of Ahmed glaucoma valve implantation in Egyptian population

AIM： To evaluate the long-term results and complications of Ahmed glaucoma valve （AGV） implantation in a cohort of Egyptian patients. METHODS： A retrospective study of 124 eyes of 99 patients with refractory glaucoma who underwent AGV implantation and had a minimum follow-up of 5y was performed. All patients underwent complete ophthalmic examination and intraocular pressure （lOP） measurement before surgery and at ld, weekly for the 1st month, 3, 6mo, and ly after surgery and yearly afterward for 5y. lOP was measured by Goldmann applanation tonometry and/or Tono-Pen. Complications and the number of anti-glaucoma medications needed were recorded. Success was defined as lOP less than 21 mm Hg with or without anti-glaucoma medication and without additional glaucoma surgery. RESULTS： Mean age was 23.1±19.9y. All eyes had at least one prior glaucoma surgery, lOP was reduced from a mean of 37.2±6.8 to 19.2±5.2 mm Hg after 5y follow-up with a reduced number of medications from 2.64±0.59 to 1.81±0.4. Complete and qualified success rates were 31.5% and 46.0% respectively at the end of follow-up. The most common complications were encapsulated cyst formation in 51 eyes （41.1%）, complicated cataract in 9 eyes （7.25%）, recessed tube in 8 eyes （6.45%）, tube exposure in 6 eyes （4.8%） and corneal touch in 6 eyes （4.8%）. Other complications included extruded AGV, endophthalmitis and persistent hypotony. Each of them was recorded in only 2 eyes （1.6%）. ~ CONCLUSION： Although refractory glaucoma is a difficult problem to manage, AGV is effective and relatively safe procedure in treating refractory glaucoma in Egyptian patients with long-term follow-up. Encapsulated cyst formation was the most common complication, which limits successful lOP control after AGV implantation. However, effective complications management can improve the rate of success.

Long-term outcomes in patients initially responsive to selective laser trabeculoplasty

AIMTo determine the long-term effects of selective laser trabeculoplasty (SLT) on intraocular pressure (IOP) and the number of medications used up to 5y following treatment in glaucoma patients receiving maximally tolerated medical therapy (MTMT).METHODSThe Wills Eye Hospital Glaucoma Research Center retrospectively reviewed the charts of glaucoma patients who underwent SLT after receiving MTMT. Eyes that did not achieve their target pressure within 3mo following SLT were excluded from the study. Changes in mean IOP and number of glaucoma medications used were analyzed at 1, 3, and 5y following SLT.RESULTSSeventy-five eyes of 67 patients were included in the study. Fifteen eyes that received SLT failed to achieve their target pressure within 3mo and were excluded from the study. The average follow-up time was 37.4mo (&#x000b1;14.4). Mean IOP was significantly reduced 1y after treatment (P=0.005). It was also reduced 3, 5y after treatment without reaching statistical significance (P=0.20 and P=0.072, respectively). There was a significant decrease in mean number of medications used 1, 3, 5y after treatment (P&#x0003c;0.001, P&#x0003c;0.001, and P=0.039, respectively). In the span of 5y, 2 eyes (2.7%) underwent repeat SLT, 7 eyes (9.3%) underwent glaucoma surgery and an additional 3 eyes (4.0%) underwent both.CONCLUSIONSLT significantly reduced the number of glaucoma medications used 5y following treatment in glaucoma patients receiving MTMT. SLT may delay operating-room surgery.

BM(book-to-market ratio) factor: mediumterm momentum and long-term reversal

To explain medium-term momentum and long-term reversal,we use the difference between the optional model and the CAPM model to construct a winner-loser portfolio.According to the CAPM model’s zero explanatory ability with respect to stock market anomalies,we obtain an anomaly interpretative model.This study shows that this anomaly interpretative model can explain stock market perceptions and medium-term momentum.Most importantly,BM is a critical factor in the model’s explanatory ability.We present a robustness test,which includes selecting new sample data,adding new auxiliary variables,changing sample years,and adding industry fixed effects.In general,the BM effect does have considerable explanatory power in medium-term momentum and long-term reversal.

“分段逐级憋压”固井工艺技术研究与应用

固井水泥浆凝结成水泥石过程中的体积收缩会导致水泥石与套管和井壁之间耦合力降低,甚至产生微间隙从而影响固井质量,严重时会导致环空带压。憋压候凝不仅能提高固井质量,而且解决了水泥浆失重引起的压稳问题。在地层承压能力不能满足一次性憋压的情况下,可根据水泥浆在凝结过程中具有塑性体的特征,分时段逐渐提高憋压值以实现环空憋压。分段逐级憋压通过井口把压力分时段传递到正处于凝结区域的水泥浆,正处于凝结区域上部的浆体的凝结时间、高度、密度对传压能力影响较大。上部浆柱凝结时间越长,压力传递能力越低;上部浆柱高度越大,压力传递能力减小;相同的凝结时间和浆柱高度,压力传递能力随上部浆柱密度增加而降低。PX2井177.8 mm+193.68 mm尾管固井作业中采用了分段逐级憋压技术,固井质量合格率达到98.1%,环空无气窜现象,该技术不增加成本,具有较大的推广价值。

“半浮动”取心保压球阀的设计研究

现行机械式保压球阀受限于井下狭小空间,保压能力弱、保压成功率低、灵活性差.针对以上问题,提出一种“半浮动”取心保压球阀设计构想.基于保压取心技术要求,采用数值仿真及理论计算,设计研发了一种“半浮动”球阀保压控制技术,创新设计的“半浮动”承压结构改变了球阀承压位置,有效增强了球阀承压能力.提出了一种气动式的新型控制方式,球阀启闭可控,可以有效解决大斜度井、水平井作业中球阀关闭难题.分别对“半浮动”及固定球阀阀体、阀座进行了有限元对比分析,“半浮动”球阀承压能力达到70 MPa,保压能力显著提升.通过理论计算确定了球阀的转矩及最小气体压力.研究结果可为保压取心技术的发展提供一定技术支撑.

深渊生物资源取样装备技术体系研究

针对深渊生物资源研究的需求,自主研发了用于全海深深度的深渊沉积物、水体和宏生物的保压取样装置,深渊沉积物保压转移装置,深渊微生物原位过滤及保存装置和高压培养高压酶学测定装置。在深海模拟环境验证了取样装置在万米深度下的工作性能。相关装置在“探索一号”科考船的TS15、TS21-1和TS21-2大洋科考航次中,搭载“奋斗者”号载人潜器、“2号”深渊着陆器、“原位实验”号着陆器于西菲律宾盆区和马里亚纳海沟进行了海上试验,成功获取了万米深度沉积物、水体和宏生物保压样品以及微生物原位过滤滤膜;成功进行了沉积物保压样品的保压转移试验。初步形成了深渊海域生物资源取样的装备技术体系,为深渊海底生物和基因资源开发,深渊生命过程等科学研究提供技术手段。

全海深沉积物保压取样装置设计及试验研究

为了实现全海深沉积物保压取样,提出基于着陆器的自密封式全海深沉积物保压取样系统。取样系统主要由深海充油电机、传动机构、取样机构、保压筒、蓄能器、压力传感器和多个高压针阀及不锈钢毛细管组成。为取样器在海底自主取样提供动力,设计了专用于深海超高压的水下电池。整套装置总重60 kg,其中,水下重量45kg。通过设计花瓣压缩环形取样、下端自封闭、两端自平衡的新型取样机构,简化了装置的结构,减轻了装置重量。通过对取样器贯入过程的分析和计算,得到最大贯入力的值为786.5 N。搭建了贯入试验台架以模拟沉积物的取样过程,在不同性质的黏土中测试取样器的取样能力和贯入力,试验结果与计算结果相符合。对于硬塑性、塑性和流塑性3种黏土,取样器的取样体积分别为410、120和20 mL,最大贯入力分别为720、210和20 N。为验证取样器保压筒的密封性能和强度,进行了110 MPa内压试验,保压120 min无压降。为验证取样器在高压下的工作稳定性及保压性能,在60 MPa和100 MPa高压舱内进行了多次测试,试验结果表明,60 MPa下保压率超过90%,100 MPa保压率超过88%。最后,在中国2021大洋科考TS21航次中,取样器搭载“奋斗者号”载人潜器在西菲律宾盆区和马里亚纳海沟进行了3次原位测试,所提出的取样器均完成保取样任务,保压率超过80%,共获取保压沉积物样品超过700 mL。

CF/PEI复合材料超声焊工艺优化及机理研究

碳纤维复合材料(CFRP)广泛应用于航空航天领域,高效连接技术是影响CFRP构件制造成本和使用安全的关键因素之一。利用超声焊技术对碳纤维增强聚醚酰亚胺树脂基复合材料(CF/PEI)进行焊接,采用单搭接剪切强度(LSS)测试研究了超声焊接压力和焊接时间对复合材料超声焊接头强度的影响,利用扫描电镜对断面微观形貌进行表征;并对实验数据进行线性拟合分析,结合BP神经网络与遗传算法对时间和压力参数进行优化并预测接头强度;最后研究了保压时间对接头强度的影响机理。结果表明:当焊接时间为2.5 s,焊接压力为0.45 MPa时,LSS达到最大值为25.6 MPa,较高的焊接强度是由于接头表面形成致密稳定的结构所致;BP神经网络将实验数据细化,遗传算法模拟出的LSS值为24.8 MPa,与实验结果误差仅为3%;随着保压时间的增加,超声焊接头强度呈现先快速增大后趋于稳定的变化趋势,当保压时间为5 s,时焊接界面处的熔融树脂基本固化完全,PEI树脂与碳纤维形成致密结构,焊接头强度达到稳定。

煤矿智能化顶板矿压预警技术研究

为了解决现有煤矿顶板矿压预警技术可靠性低、准确性差、智能化不足的问题,研究了基于机器学习的工作面矿压预警指标分析方法,并分别采用了线性回归、系统聚类方法对液压支架循环内载荷以及周期来压步距进行分析,构建了顶板灾害预警算法,实现了工作面顶板灾害监测关键指标的自动分析和预测预警。现场应用结果表明:预警系统运行可靠性高、分析预警功能全且准确性高,在示范矿井进行顶板来压实际次数统计,其中预测准确次数不低于90%。能够为煤矿顶板灾害防治提供重要支持。

超高压及植物油添加量对兔肌球蛋白热凝胶特性的影响

为研究超高压处理及植物油添加量对兔肌球蛋白热凝胶特性的影响,在不同压力条件(100、150、200 MPa)下对兔肌球蛋白进行10℃、2 min超高压处理,然后分别添加不同体积分数(0%、10%、20%、30%)的大豆油和磷酸盐缓冲液制备乳化体系,再利用程序升温(1℃/min)制备凝胶,并以未经高压处理的肌球蛋白作为空白对照。利用流变仪、质构分析仪、扫描电子显微镜、低场核磁共振分析仪等对热凝胶的储能模量G′、损耗模量G″、凝胶强度、保水性、微观结构和弛豫时间等指标进行测定。结果表明:与空白对照组相比,高压处理及添加油脂使兔肌球蛋白热凝胶的G′、G″、凝胶强度、保水性等指标均明显增加;通过扫描电子显微镜观察到经复合处理的凝胶三维网络结构变得更加致密和紧凑,低场核磁共振分析结果显示凝胶基质中的自由水相对含量随着压力的增加逐渐减少,不易流动水质子结合程度增加,结合水组分相对含量明显增多。在相同压力处理条件下,兔肌球蛋白热凝胶的G′、G″、凝胶强度、保水性随着油脂添加量的增加而增大,即0%处理组<10%处理组<20%处理组<30%处理组,且相互之间差异显著(P<0.05);其中,在200 MPa下添加30%油脂时,兔肌球蛋白热凝胶性能最好。综上,适当的高压处理结合油脂的添加,一定程度增强了蛋白质和脂肪的相互作用,改变了肌球蛋白热凝胶的微观结构和水分分布状态,从而表现出相应流变特性、质构特性、保水性等凝胶特性的变化,进而对改善兔肌球蛋白热凝胶的功能特性发挥积极作用。

气体灭火系统防护区气密性测试方法分析及试验研究

气体灭火系统常用于数据机房、电池储能舱等不宜用水灭火的重要场所,气体灭火系统防护区气密性直接影响灭火成功率。近年来,防护区气密性问题导致浸没时间不足,致使火灾复燃的案例时有发生,而国内现行气体工程建设标准中尚未明确气体灭火系统防护区气密性测试的具体方法,为保证气体灭火系统的可靠性,亟须对气体灭火系统防护区气密性进行测试验证。本文概述了对气体灭火系统防护区可靠性进行验证的测试方法,对比分析了国外常用气密性检测标准中计算模型的差别,通过设计试验发现,灭火剂喷放后实际的空气-灭火剂交界面浓度分布处于NFPA 2001与ISO 14520-1假设模型之间的区间,验证了鼓风门法测试浸渍时间的可行性;并对适用于气体灭火系统防护区的峰值压力计算方法进行了可行性分析,为完善气体灭火系统防护区气密性测试方法提供借鉴。

煤层密闭侧面取样装置的设计与模拟

煤矿瓦斯灾害防治是矿井安全生产的重点和难点,其核心是煤层瓦斯含量的精准测定,对煤层中定点位置进行煤样获取是进行瓦斯含量测定的关键。为此设计一种通过钻杆内部通风进行钻头冷却排渣、侧面边钻进边取样方式的煤矿井下密闭取样装置,用于煤层煤样的获取与瓦斯含量测定。确定了整体装置的构建,建立了取样装置外部钻杆和钻头的有限元模型,并对取样装置内流场进行仿真分析,得出气流经狭长腔道中的流场状态。结合分析进行取样装置样机制造,便于进一步开展煤层取样工作。