Vertical two-dimensional non-hydrostatic pressure model with single layer

The vertical two-dimensional non-hydrostatic pressure models with multiple layers can make prediction more accurate than those obtained by the hydrostatic pres- sure assumption. However, they are time-consuming and unstable, which makes them unsuitable for wider application. In this study, an efficient model with a single layer is developed. Decomposing the pressure into the hydrostatic and dynamic components and integrating the x-momentum equation from the bottom to the free surface can yield a horizontal momentum equation, in which the terms relevant to the dynamic pressure are discretized semi-implicitly. The convective terms in the vertical momentum equation are ignored, and the rest of the equation is approximated with the Keller-box scheme. The velocities expressed as the unknown dynamic pressure are substituted into the continuity equation, resulting in a tri-diagonal linear system solved by the Thomas algorithm. The validation of solitary and sinusoidal waves indicates that the present model can provide comparable results to the models with multiple layers but at much lower computation cost.

Pressure manipulation of ultrafast carrier dynamics in monolayer WS_(2)

Two-dimensional transition metal dichalcogenides(TMDs)have intriguing physic properties and offer an exciting platform to explore many features that are important for future devices.In this work,we synthesized monolayer WS_(2)as an example to study the optical response with hydrostatic pressure.The Raman results show a continuous tuning of the lattice vibrations that is induced by hydrostatic pressure.We further demonstrate an efficient pressure-induced change of the band structure and carrier dynamics via transient absorption measurements.We found that two time constants can be attributed to the capture process of two kinds of defect states,with the pressure increasing from 0.55 GPa to 2.91 GPa,both of capture processes were accelerated,and there is an inflection point within the pressure range of 1.56 GPa to 1.89 GPa.Our findings provide valuable information for the design of future optoelectronic devices.

THE TRANSIENT TWO-DIMENSIONAL FLOW THROUGH DOUBLE POROUS MEDIA

This paper presents the analytical solutions in Laplace domain for two-dimensional nonsteady flow of slightly compressible liquid in porous media with double porosity by using the methods of integral transforms and variables separation. The effects of the ratio of storativities to , interporosity flow parameter on the pressure behaviors for a vertically fractured well with infinite conductivity are investigated by using the method of numerical inversion. The new log-log diagnosis graph of the pressures is given and analysed.

三环追压非等灌对枸杞根系湿润体盐分的影响

针对新疆降水稀少、蒸发量大,土壤盐碱化面积不断蔓延,改良盐碱地用水量居高不下等问题,提出一种以作物为圆心滞后滴水的3环灌溉模式,探究其节水排盐效果.将枸杞作为研究对象,根据土壤湿润体内盐分运移规律,试验确定第1环、第2环、第3环的半径分别为5,10,15 cm.在滴水器流量为3 L/h的条件下,第1环(最内环)先开始滴水,2 h之后,其滴水产生的土壤湿润体脱盐范围超出第2环位置时,打开第2环滴水阀门;以此类推,2 h之后打开第3环滴水阀门,各环滞后滴水将根系发育范围内的盐分逐步追压至根系发育范围之外,从而达到节水排盐的效果.对晾干后土体采用剖面法取样测定不同位置的盐分含量,结果表明:环心附近的盐分少,离环心越远盐分含量越多;环心水平方向40 cm处不同深度取土检测盐分质量比:在(0,10],(10,20],(20,30],(30,40]和(40,50]cm分别为61.550,57.640,53.470,50.690和129.650 g/kg,表明土壤盐分积累在湿润体边缘,排盐效果良好;同时,试验的灌水定额为31.5 mm(315 m^(3)/hm^(2)),年总灌水量为1890 m^(3)/hm^(2),较常规滴灌条件下枸杞的年灌水量3450 m^(3)/hm^(2)节约了1560 m^(3)/hm^(2),节水效果显著.

政府卫生支出、财政压力与居民医疗服务利用机会不平等分析

目的:分析政府卫生支出与居民医疗服务利用机会不平等之间的关系及其作用机制,为完善相关政策提供理论依据。方法:基于机会平等理论,利用CFPS2014—2020年数据测算居民医疗服务利用的机会不平等程度。结果:2014—2020年,我国居民医疗服务利用的机会不平等上限均值为0.781,下限均值为0.264,机会不平等的相对程度均值为0.337,即总不平等中有33.7%是机会不平等造成的;每增加1个单位的政府卫生支出,机会不平等程度增加4.6%,说明我国政府卫生支出存在一定的结构性问题;财政压力作为调节变量,能够削弱政府卫生支出对机会不平等的影响。结论:增加政府卫生支出能够改善欠发达地区医疗服务利用机会不平等问题,同时应从报销比例、地域、财政压力等方面,提升医疗服务利用公平性。

非等压应力场下充填钻孔主应力差分布规律

为了探究非等压应力场下充填钻孔主应力差分布规律并评估其稳定性,采用理论分析、数值模拟和工程实例方法,分析了不同钻孔直径、垂直主应力σV、最大水平主应力σH、水平主应力比λ′下钻孔主应力差和塑性区的分布规律。结果表明:平行于最小水平主应力σh方向的钻孔内壁处均是主应力差最大区域;建立了不同λ′下钻孔主应力差最大位置计算模型,可为预测不同围岩深度下钻孔破裂发展方位提供理论指导;钻孔主应力差分布的数值模拟结果与理论计算结果基本一致,验证了理论分析的正确性。当围岩参数一定时,不同钻孔直径、σH、σV下主应力差分布均为类“8”字形,不同λ′下主应力差的分布形态转变历程为圆形→椭圆形→类“8”字形;围岩塑性区先出现在主应力差最大方位,即平行σh方向,后向平行σH方向发展;塑性区的存在可能导致围岩失稳,并使得钻孔横截面由圆形向椭圆形发展。以国外某铜矿充填钻孔为例,分析了围岩主应力差和塑性区分布规律,并计算了钻孔加固的最小泥浆压力,可为提高钻孔稳定性提供工程指导。

Pressure Distinguishes the Dual Emissions in Pseudohalide 2D Ruddlesden-Popper Perovskite Cs_(2)Pb(SCN)_(2)Br_(2)

Two-dimensional(2D)Ruddlesden-Popper(RP)halide perovskites with diverse structures and properties have drawn increasing attention due to their promising optoelectronic applications.Recently,a new all-inorganic Cs_(2)Pb(SCN)_(2)Br_(2) has been reported that opens up new potential for the development of 2D RP perovskites.However,recent reports of unusual dual emissions and two-edge absorption in Cs_(2)Pb(SCN)_(2)Br_(2) have generated intense debate about its origin and remains controversial.Here,by combining continuous pressure tuning with in situ diagnostics,we have unambiguously revealed the underlying mechanisms that the 2D Cs_(2)Pb(SCN)_(2)Br_(2) exhibits an intrinsic blue emission at 2.66 eV and an absorption edge close to the emission peak.While the gradually formed CsPbBr_(3) is responsible for the green emission at 2.33 eV with the absorption shoulder at 2.41 eV.Furthermore,by fitting the temperature-dependent intensity of the intrinsic blue emission,we have determined the corrected value of exciton binding energy for 2D Cs_(2)Pb(SCN)_(2)Br_(2) to be 90 meV.Intriguingly,an emission enhancement of 2.5 times is achieved in Cs_(2)Pb(SCN)_(2)Br_(2) under a mild pressure within 0.8 GPa,caused by the pressuresuppressed exciton-phonon interaction.This work not only elucidates the origin of the dual emissions and two-edge absorption in Cs_(2)Pb(SCN)_(2)Br_(2),but it also provides a potential means to regulate and optimize the optoelectronic properties of 2D perovskites.

不等模数渐开线齿轮副参数极限值与有限元分析

为了解决常规变位齿轮对中心距调节及强度分配的局限性,提出利用基圆节距相同但模数不等的结构,大幅度提高齿轮传动中较小齿轮的强度,尤其是齿根强度。但用于工程实践中的模数与齿形角相差均较小,通过对渐开线齿面的形成原理及齿轮啮合中部分参数的分析,得到了此种齿轮模数、齿数、齿形角、齿高系数等参数的限制条件,并通过公式推导了齿数、齿高系数与分度圆压力角极限值的关系式。基于工程实践情况建模并通过Ansys进行了有限元分析,得到基于极限参数设计的齿轮强度约为标准齿轮的2.66倍,验证了理论的可行性,并扩大了此种齿轮副的应用范围。

多模数ZI蜗杆斜齿轮传动设计与有限元分析及其应力预测

为解决传统渐开线蜗杆斜齿轮副在开式传动或传动比过大时斜齿轮容易发生齿根断裂的情况,提出一种新型的基于不等模数不等压力角设计的渐开线蜗杆副,使斜齿轮的模数与压力角同时提高,大幅提高斜齿轮的齿根强度。通过对此种蜗杆副的传动特性的分析,得到特殊的啮合角与中心距计算方式。另外,通过对同传动比、同蜗杆情况下基于不等模数设计的ZI蜗杆斜齿轮副和传统ZI蜗杆斜齿轮副的建模与有限元分析,得出在较大模数比情况下的斜齿轮齿根强度约为传统斜齿轮齿根强度的2.956倍,增大了渐开线蜗杆的应用范围。后续使用灰色预测,对比出误差平方和(Sum of Squared Errors,SSE)最小模型,予以验证预测的准确性,另外进行蜗杆施加不同转矩下的斜齿轮啮合齿受拉力处最大应力σ_(1max)的数据预测,为相应的工程分析与必要的校核设计给出了依据。

页岩气多段压裂水平井不等长裂缝定量评价方法研究

页岩气井的压裂改造效果受储层地质、岩石力学性质和地应力等多重因素综合影响,微地震监测和产液剖面测试均显示单井各段改造效果差异较大。为精细评价气井产能,需快速、准确地评价单段的改造效果,本文基于注入压降试井理论对单段压后停泵压降数据进行分析,建立页岩气压裂井不稳定渗流数学模型,获取停泵后压力和压力导数的双对数曲线,从曲线形态和解释参数对单段压裂的改造效果进行定量评价。实例应用结果表明:该方法的解释结果与微地震监测以及G函数分析结果基本吻合,验证了该方法的准确性。该方法可有效实现单段缝长的定量评价,为准确开展数值模拟提供基础,同时也为井距的优化调整提供技术支撑。

Two-dimensional van der Waals thin film transistors as active matrix for spatially resolved pressure sensing

The development of pressure sensor arrays capable of distinguishing the shape and texture details of objects is of considerable interest in the emerging fields of smart robots,prostheses,human-machine interfaces,and artificial intelligence(AI).Here we report an integrated pressure sensor array,by combining solution-processed two-dimensional(2D)MoS2 van der Waals(vdW)thin film transistor(TFT)active matrix and conductive micropyramidal pressure-sensitive rubber(PSR)electrodes made of polydimethylsiloxane/carbon nanotube composites,to achieve spatially revolved pressure mapping with excellent contrast and low power consumption.We demonstrate a 10×10 active matrix by using the 2D MoS2 vdW-TFTs with high on-off ratio>10^(6),minimal hysteresis,and excellent device-to-device uniformity.The combination of the vdW-TFT active matrix with the highly uniform micropyramidal PSR electrodes creates an integrated pressure sensing array for spatially resolved pressure mapping.This study demonstrates that the solution-processed 2D vdW-TFTs offer a solution for active-matrix control of pressure sensor arrays,and could be extended for other active-matrix arrays of electronic or optoelectronic devices.

Manipulating Emission Enhancement and Piezochromism in Two-Dimensional Organic–Inorganic Halide Perovskite[(HO)(CH_(2))_(2)NH_(3)]_(2)PbI_(4)by High Pressure

Two-dimensional(2D)organic–inorganic halide perovskites present remarkable stability and diversity and are promising alternatives to their three-dimensional(3D)counterparts.The 2D halide perovskite[(HO)(CH_(2))_(2)NH_(3)]_(2)PbI_(4)is regarded as a superior moisture-stabile“smooth”perovskite because of distinct hydrogen-bond networks that connect adjacent organic–inorganic layers.

浅埋不等跨隧道围岩压力计算方法与影响规律研究

为研究不等跨隧道围岩压力,构建不等跨隧道破坏模式,基于极限上限法推导不等跨隧道围岩压力,并进行验证对比;分析不等跨隧道围岩压力分布特征,最后就相关影响因素做参数分析。结果表明:两隧道内侧围岩压力比外侧大;小跨洞竖向围岩压力大于大跨洞相应侧的值;两洞不等跨时的围岩压力比等跨时的大。随着相对跨度增大,两隧道之间的围岩压力差异增大,且大跨洞将承受更多的围岩压力。在浅埋条件下,埋深对围岩压力的影响较大。大跨隧道围岩压力随着小跨隧道埋深增大而逐渐减小;小跨隧道围岩压力则随着埋深增大而增大。竖向平均围岩压力随着两洞净距的增大呈现先增大后减小。围岩压力随GSI、m_(i)、σ_(ci)值(Hoek-Brown准则相关参数)的增大而减小。不等跨隧道应结合其相对跨度大小、两洞埋深等条件,根据所受围岩压力不同而采取不对称支护。

压力匹配器在抽汽供热中的应用

江苏徐矿综合利用发电有限公司坐落在徐州市贾汪区,根据地区“十三五”发展规划及现有工业和居民热用户需求调研,结合大气污泥源头防治、削减污染物排放总量的环保要求,利用清洁、高效发电技术对汽轮机组进行供热改造,实施“以大代小、上大压小”策略,淘汰、退役小机组和分散小锅炉,发展热电联产适应城市采暖热负荷和工业热负荷的需求,符合国家节能减排政策,具有良好的社会效益、环境效益和经济效益。

基于Hoek-Brown的双向不等压隧道支护估算及工程应用

现行隧道塑性区分析中常基于轴对称荷载建立分析模型,忽略侧压力带来的影响。增加了对围岩侧压力的考虑,基于Hoek-Brown准则推导了双向不等压圆形隧道的塑性半径及应力计算式。依托滇中引水工程板凳山隧洞的监测数据,结合滑移剪切模型对隧道的极限位移和极限支护应力进行计算。结果表明:在确定围岩材料参数的条件下,塑性边界上的径向应力为恒值;环向应力在θ为0~30°范围内与侧压力成正比,在θ为30°~90°范围内与侧压力成反比,当θ取30°时环向应力为最大值,最终形成蝴蝶状的曲线。隧洞塑性区范围随着侧压力系数的降低呈现出上下端部小,中间部分大的椭圆形,在λ<0.38后,塑性区不再是可完整包裹开挖截面的椭圆形。基于滑移剪切模型对隧洞极限位移和极限支护应力进行计算,完善具有滇中红层特性的隧洞支护特征曲线。根据以上的计算结果对支护方案进行修正,并通过监测结果验证了方案的合理性。

两向不等压圆形孔口压缩与扩张问题的塑性区半径统一解

【目的】在地下工程中,隧道或水平定向钻井过程中的最大泥浆压力分析等所处真实应力场常为远处两向不等压应力场。为了求解两向不等压应力场下圆形孔口压缩和扩张问题的统一解析解,【方法】基于统一强度理论和弹脆塑性模型,借鉴鲁宾涅特解的求解方法,推导了两向不等压圆形孔口压缩和扩张问题的塑性区半径统一解,并与复变函数解、摄动解进行了对比,最后分析了各因素对塑性区半径的影响以及在实际工程中的应用。【结果】结果显示:当两向为不等压应力场时,弹塑性交界线均呈现类椭圆形状,对于压缩问题,类椭圆长轴方向与两向不等压应力场较小值处一致,并且弹塑性交界线在极角0°~90°范围内分成两段,在极角0°~30°范围内,弹塑性交界线随两向不等压应力场的应力比增加水平向左移动,在30°~90°范围内,弹塑性交界线随两向不等压应力场的应力比增加竖直向上移动,而对于扩张问题则相反;对于压缩问题,支护力、中间主应力、残余黏聚力和残余内摩擦角对塑性区半径影响显著,而对于扩张问题,扩孔压力、中间主应力、残余内摩擦角对塑性区半径影响显著,残余黏聚力对塑性区半径几乎无影响。【结论】在实际工程分析中,应充分考虑两向不等压应力场、中间主应力和弹脆塑性模型的影响,并且采用弹脆塑性模型比理想弹塑性模型计算的塑性区半径大,更适合岩土类材料弹塑性分析。

Property modulations of two-dimensional materials under compression

Two-dimensional(2D)materials have attracted considerable research interest,leading to significant advances in energy applications in recent years,such as lithium batteries,catalysis,electronics,and thermoelectrics,owing to their rich controllable properties and excellent performances.Recently,pressure has been successfully employed as an effective method for property modulation of 2D materials,through tuning electronic orbitals and bonding patterns.In this review,we summarize recent progresses in the pressure-driven property modulations and elucidate the underlying mechanism of the pressure modulation of 2D materials.Further,we identify the remaining challenges and opportunities in this new,vibrant area of research for energy conversion and utilization.Among the different property modulation strategies,the in situ application of high pressure is systematically identified as a promising knob for 2D materials.This review is expected to inspire further research on the fundamental understanding and practical applications of high-pressure modulation in 2D materials.

非等高连体双塔高层建筑风致效应研究

基于风洞试验,对某非等高连体双塔高层建筑的风致效应特性进行了研究,得到了各塔楼的平均风压分布及测点的风压时程。然后,对该高层结构的风荷载及其风致动力响应进行了研究,为该类双塔结构抗风设计提供了设计依据。结果表明,风向角、结构高度与重现期风速对结构表面风压分布与动力响应的影响较大。双塔之间的相互影响导致临近表面风场发生变化,从而引起风压发生显著变化。1^(#)塔楼结构的风致动力响应最大值满足中国相关规范的要求。

不等间距叶片对离心泵性能及压力脉动影响分析

为研究叶片不等间距对离心泵性能及压力脉动影响,以一比转数为132.7的离心泵为研究对象,基于转子自动平衡理论建立了3种叶片不等间距叶轮模型,并对模型泵全流场进行了CFD数值计算,获得了模型泵外特性、叶轮内流分布及蜗壳内压力脉动信息。利用外特性试验验证了计算方法的准确性,并对叶片不等间距与原等间距叶轮模型计算结果进行了对比分析。分析表明:叶片不等间距布置会使泵扬程降低,效率升高,且最小角间距越小,扬程下降越明显,效率上升越明显,但最小角间距为45°、50°、55°时,3个工况下的扬程、效率计算值变化幅度均保持在5%以内,满足设计要求;叶片不等间距布置后叶轮工作面附近的低速区更明显,且主要存在于较宽流道,最小角间距越小,低速区范围越大;叶片不等间距模型在145 Hz及其谐频处产生新的压力脉动峰值,一定程度上改善了压力脉动频谱平稳性,其中最小角间距为45°、50°的2种模型在此处的脉动量整体比叶频处脉动量还大。该研究结果可为离心泵优化设计提供参考。

不等跨连拱铁路隧道围岩压力分布及受力特征模型试验研究

以兰渝铁路新作坊隧道洞口明挖段不等跨连拱结构为背景,采用室内模型试验的方法,对不等跨连拱铁路隧道围岩压力分布及受力特征进行研究。试验结果表明：隧道水平侧压力均小于竖向围岩压力,拱顶处侧压力小于墙脚处侧压力,小洞侧侧压力系数平均为0.55,大洞侧侧压力系数平均为0.65;中隔墙顶部围岩压力均大于拱顶处围岩压力,且大洞拱顶围岩压力约为小洞的1.2倍;隧道结构总体为小偏心压弯构件,大洞所承受的轴力总体比小洞承受的轴力大20%-30%;隧道先后在大小洞靠近中隔墙的拱腰及仰拱处破坏,最终发生整体失稳;靠近中隔墙的大小洞拱腰及仰拱是设计施工时应重点关注的部位;最终获得不等跨连拱铁路隧道的围岩压力分布模式,研究结果可以直接指导新作坊隧道结构的设计与施工,有利于完善不等跨连拱隧道设计施工理念。