Stress area of the mandibular alveolar mucosa under complete denture with linear occlusion at lateral excursion

Background The rocking and instability of a loaded complete denture （CD） during lateral excursion reduce the bearing area under the denture base, causing localized high stress concentrations. This can lead to mucosal tenderness, ulceration, and alveolar bone resorption, and the linear occlusion design was to decrease the lateral force exerted on the denture and to ensure denture stability. But it is not known how the bearing areas of linear occlusal CDs （LOCDs） and anatomic occlusal CDs （AOCDs） differ. The purpose of this study was to analyze and compare the distributions of the high and low vertical stress-bearing areas in the mandibular alveolar mucosa under LOCDs and AOCDs at lateral excursion.Methods Computerized tomography （CT） and finite element analysis were used to establish three-dimensional models of an edentulous maxilla and mandible with severe residual ridge resorption. These models were composed of maxillary and mandibular bone structure, mucosa, and the LOCD or AOCD. Lateral excursion movements of the mandible were simulated and the vertical stress-bearing areas in the mucosa under both mandibular CDs were analyzed using ANSYS 7.0.Results On the working side, the high stress-bearing （-0.07 to -0.1 Mpa） area under the LOCD during lateral excursion was smaller than that under the AOCD, while the medium stress-bearing （-0.03 to -0.07 Mpa） area under the LOCD was 1.33-fold that under the AOCD. The medium stress-bearing area on the non-working side under the LOCD was 2.4-fold that under the AOCD. Therefore, the overall medium vertical stress-bearing area under the LOCD was 20% larger than that under the AOCD.Conclusions During lateral excursion, the medium vertical stress-bearing area under a mandibular LOCD was larger and the high vertical stress-bearing area was smaller than that under an AOCD. Thus, the vertical stress under the LOCD was distributed more evenly and over a wider area than that under the AOCD, thereby improving denture stability.

The Stimulating Effects of Rewatering on Leaf Area of Winter Wheat Suffering Water Stress

After water stress at various levels and durations at different growth stages, rewatering could greatly stimulate the leaf area development of winter wheat. The results showed that the stimulation effect changed with water stress time, degree and duration. Rewatering under earlier stress had greater stimulation effect on leaf area than that under later stress. Higher stimulation effect was observed under severe water stress than that under moderate stress. Longer duration of stress resulted in low stimulation effect. In spite of the greater stimulation effect under severe and longer stress, the final leaf area in these situations was lower than that under moderate stress and shorter duration. Whenever the stress occurred, the stimulating effect was due to the increase of the leaf area of the tillers. Once the leaf on the main stem emerged during stress period, rewatering had no effect on its size, and consequently its leaf area. The stimulation of rewateirng on leaf area contributed to the final grain yield by 45% under moderate stress, and 67% under severe stress. Although the stimulation partly compensated for the loss during stress, the final leaf area and the grain yield could not reach the level without water stress.

Discussion on the dynamic mechanism of Great North China area based on the observed stress data

Based on the constrained data from the observed stress orientation and the observed stress regime, the tectonic stress fields of the Great North China area has been simulated by using the pseudo-3D finite element method. The results indicate that the stress fields in this area are basically controlled by the push forces coming from the Pacific Plate and from the Tibet Plateau, and the WNW-ward action from the Pacific Plate play a more important role in North China plain block. In addition to that, the stress field in this area is also partly formed by the extension action from the mantle upwelling in perpendicular at the basin margins.

缺水胁迫区水系统优化调控理论与模式

开展水系统优化调控是实现缺水胁迫区人-水-生态和谐可持续发展的关键措施之一,对于保障地区经济社会稳定发展和生态健康具有重要意义。本文以京津冀作为典型缺水胁迫区案例,通过解析水系统内涵,总结得出缺水胁迫区水系统存在深度耦合、强烈竞争和系统失衡三大现象,发现水系统呈现非稳态和稳态之间交替演进的模式,并通过构建水系统稳态指数,研判了京津冀地区水系统状态变化发展过程。研究以实现自然社会水系统健康为调控目标,提出缺水胁迫区水系统“高内聚-低耦合”解耦式调控模式,结合京津冀现实状态,在需求侧开展“保障刚需-压缩弹性-抑制奢侈”层次化调控,在供给侧进行“自然水网-人工水网-虚拟水网”适配性优化,提出京津冀“三线七河、四区八源”一体化水网布局,进而实现水系统的整体健康。

考虑椭圆模型M_W≥5.5地震震源参数时域计算方法

为提高时效性,地震预警系统对震源的处理一般采用“点源”假定,不考虑震源尺度、破裂方向和震源区应力降,对震源参数简化处理使得预测地震动参数分布过于粗略,特别是对破坏性大震.本文应用日本地震(M_W≥5.5)强震动数据,考虑椭圆震源模型,提出了一种适用于中、大地震矩震级、拐角频率和应力降等震源参数时域计算方法,并分析了场地效应、地震动传播衰减、震源效应和滤波频带等因素对时域方法的影响.结果表明,该方法能利用P波信息快速获取震源能量释放过程,量化随破裂传播震源谱拐角频率、应力降和破裂面积的演化过程,为地震动预测提供更多重要的震源参数.

盐胁迫对春茄6号茄子幼苗叶面积及生理生化指标的影响

茄子是世界四大蔬菜作物之一,其周年供应主要依靠设施化栽培技术。然而,设施栽培因常年大量施用化肥和不合理灌溉等因素导致土壤次生盐碱化,这将严重影响蔬菜的生长发育和设施农业的可持续发展。因此,本试验以春茄6号幼苗为试验材料,研究0、50、100、150 mmol/L这4个浓度NaCl盐胁迫对春茄6号叶面积和抗氧化酶含量的影响,并分别在第0天、第3天、第6天和第9天记录叶面积,同时测定了丙二醛(MDA)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)的含量。结果表明:随着盐胁迫浓度逐渐上升,春茄6号幼苗叶面积增长逐渐缓慢,在150 mol/L浓度NaCl处理下春茄6号幼苗叶面积生长量最低;NaCl盐胁迫对春茄6号幼苗叶片的叶面积及MDA、SOD、POD和CAT含量均会产生抑制。不同NaCl浓度对春茄6号幼苗的抑制效果表现为150 mmol/L>100 mmol/L>50 mmol/L>0 mmol/L。

基于磁各向异性的管壁应力集中区域检测方法

针对应力集中导致管壁发生屈服失效的问题,提出了利用磁各向异性检测管壁应力集中区域的方法。从能量角度出发,研究了应力导致管壁产生磁各向异性的机理,建立了管壁当量应力与磁各向异性探头输出电压信号的数学模型,通过计算管壁的当量应力判断其是否发生屈服失效,搭建了应力检测实验平台。实验结果表明,应力会导致管壁产生磁各向异性,磁各向异性检测方法能够检测出管壁当量应力的变化趋势和主应力方向所在延长线的角度,进而判断管壁是否产生应力集中区域。

塔中顺北地区志留系断裂特征与应力场扰动分析及井位优选

塔里木盆地中部顺北地区复杂构造应力造成了多层系断裂样式的差异性。当钻井钻至志留系断裂破碎带,地层压力小于钻井液液柱压力时,易发生漏失现象。为保障钻井的高效钻进,亟需开展志留系断裂特征与应力场扰动分析以指导井位设计。通过志留系断裂增强解释性处理及空间解释,结合断裂生长指数,开展断裂综合解析。研究区断裂整体特征为下伏陡直走滑与上覆雁列正断层分层变形,志留系断裂样式以加里东晚期至海西早期活动的雁列式负花状正断层组合排列为主,呈右阶雁列式展布,走滑伸展作用强烈。基于已钻井SHZ1等偶极阵列声波测井等资料,确定了顺北中部地区志留系主应力方向为北东向54°。结合研究区三维地震资料综合解释,建立地质模型,开展迭代边界元数值模拟,明确研究区现今地应力的平面分布规律,包括最大、最小和中间主应力,并将应力场模拟结果与实际测井资料解释结果进行对比分析。受断裂产状和断距的影响,平面上应力扰动带宽度不同,同一断裂的上、下盘应力扰动范围呈现出非对称分布。通过对志留系断裂空间立体雕刻及应力扰动分析,避开志留系断裂强度大、倾角大的雁列单元边界断裂、断裂应力集中部位及强能量异常断裂、裂缝发育区,结合目的层靶点空间特征,优选井位及其井轨迹设计。志留系断裂综合解析与应力场扰动分析为井位优选中规避志留系严重漏失、保障钻井高效钻进提供了保障。

安百拓液压凿岩机活塞受力面积分析与三段法述评

搜集了11个安百拓双控式凿岩机和4个后控式凿岩机冲击活塞的直径数据,计算得到在凿岩机冲击运动周期中,回程与冲程活塞受力面积的比值范围。根据比值数据的分析,指出基于三段法理论的设计变量作为凿岩机性能评价指标的普适性较差。据此,本文强调了数据分析在凿岩机研究中的重要作用。文中还介绍了改进的三段法理论及其计算实例,论述了改进的三段法的优点与缺点。

Coupling characteristics of stress and strain at different layers of different sub-regions in Yunnan and its adjacent areas

In this paper, we collect 6 361 waveform data to calculate the shear wave splitting parameters from a regional seismic network of 22 digital stations in Yunnan and its adjacent area from July 1999 to June 2005. By using the cross-correlation method, 64 splitting events of 16 stations are processed. We also collect the splitting results of eight earthquake sequences to present the characteristics of shear wave splitting in Yunnan and its adjacent areas. The orientations of maximum principal compressive stress of three sub-regions in this area are derived from the CMT focal mechanism solutions of 43 moderate-strong earthquakes provided by Harvard University by the P axis azimuth-averaging method. The principal strain rate at each observatory is deduced from the observations of Crustal Movement Observation Network of China during the period from 1999 to 2004. In addition, the data of Pn aniso- tropy and SKS splitting of Yunnan and its adjacent areas are also collected. We have discovered from this study that the continental lithosphere, as a main seismogenic environment for strong earthquake, can be divided into blocks laterally; the mechanical behavior of lithosphere varies with depth and can be divided into different layers in the vertical orientation; the information of crustal deformation obtained from GPS might be affected by the type of blocks, since there are different types of active blocks in Yunnan and its adjacent areas; the shear wave splitting in this region might be affected mainly by the upper crust or even the surface tectonics.

渤海海峡跨海通道工程区海域三维地应力测试

跨渤海通道海域缺乏实测地应力基础数据,而海域钻探原位实测又承担着巨大风险与重重困难,为取得工程区现今地应力场特征第一手资料,利用以水压致裂地应力测量为主,以空心包体、非弹性应变恢复、差应变、声波各向异性法为辅的综合地应力测量技术,对研究区海域开展三维地应力测试与研究,建立了线性回归方程,得到了回归拟合曲线。结果表明,渤海海峡最大水平主应力σH、最小水平主应力σh与垂直主应力σv均随测试深度的增加呈线性增大规律;海峡南部地应力状态存在σH>σh>σv的关系,处于逆冲应力状态,应力场方向为NE,最大水平主应力大于垂直主应力,区域内构造力处于主导地位;海峡北部应力状态为σH>σv>σh,有利于走滑断层活动,应力场方向为NE,区域内构造力处于主导地位;整个工程区内地应力各分量值之间相差不大,远远小于区内断层活动应力值的下限,表明研究区目前处于稳定状态。研究结果符合一般地应力测量规律,测试流程符合地应力测试要求,测试数据可用于分析区域地应力状态。

黄土地区洞桩法地铁车站边桩和中柱的受力变形机理

[目的]为了确保黄土地区洞桩法车站施工过程中重要竖向承重构件的稳定性,需要对施工过程中边桩和中柱的受力变形机理进行研究,并对最不利受力阶段边桩和中柱提出变形控制措施。[方法]以西安地铁2号线何家营站为研究背景,通过数值模拟与现场监测的方法,对施工过程中边桩的水平位移、钢筋内力、水平土压力及中柱应变展开研究。[结果及结论]扣拱施作以及站厅层和站台层土体开挖是边桩水平位移最不利的三个阶段,在这些关键阶段施工时,应在结构内部架设钢支撑并适当加固已扰动的地层;在桩梁和扣拱施作中,边桩主筋承受轴向压力,而在站内剩余土方施工阶段,边桩背土侧的钢筋由轴向压力逐渐转化为轴向拉力,且随着边桩埋深的增大,钢筋的轴向拉压力增长变缓;在扣拱初期支护施作中,土压力在边桩埋深6.6 m处达到最大值34.5 kPa,且随着边桩埋置深度增大,边桩的桩侧压力增长速率显著,因此车站内侧的土方开挖是控制边桩迎土侧土压力大小的关键阶段,必要时对桩后土体进行注浆加固有利于提高桩基的承载力;中跨扣拱施工时,中柱的应变呈现出先减小、后增大的趋势。

Determine Stress Field of the Shirband Area by Geometric and Kinematic Analysis of Faults and Folds (North Damqan, Iran)

In this paper faults and folds of shirband area (north of damqan) investigated to determine the orient of the stress field. The study area is limited between the two faults with E-W strike and northward slip. Investigations result show major faults of the area have sinisteral mechanism. Waterways displacement and slicken slip of faults approve this issue. Three main folds of area has approx-imately same trend along major faults (E-W). Orientation of stress field investigated and classified by using from some large and medium scale faults and folds. Analysis of stress field investigated by inversion method show that compression axis in the study area have approximately NE-SW strike.

西南山区铁路客运专线隧道底鼓病害变形监测研究

西南山区铁路客运专线具有高桥隧比、沿线地质条件复杂恶劣等特征,在建设和运营过程中易出现各类工程病害。文章基于某隧道底鼓变形病害,设计并开展包含围岩变形、仰拱受力和道床板沉降变形3个监测指标的隧道变形监测方案。通过对监测数据进行分析,获取隧道和围岩受力变形的演化规律,据此提出后续加密轨道几何形位静态、动态检测和衬砌结构贯通裂缝观测、实施列车降速运行等处理措施。相关研究可为该客运专线的安全运营提供有力保障,同时为类似工程隧道病害的监测和整治工作提供有益参考。

马头营干热岩开采试验场地人工注水诱发地震探讨

结合马头营干热岩区7个临时测震台站的地震观测资料和M1井2022-06~09的加压注水数据,研究地震活动与注水压力、水流量的关系,同时分析诱发地震震源机制解及其对周边应力场的影响。结果表明,注水作业可能诱发了201个地震,震源深度主要集中在0~4 km,这个区段也是地围压较小的安全区域,发生中强震的几率较小;水流量、水压力的改变不仅影响诱发地震的时空分布特征,而且影响地震活动频度,应力积累到一定水平诱发地震发生,之后水流量、水压力与地震频度呈现正相关关系;注水量和震级之间关系不明显,压力和诱发地震震级呈线性相关;在持续注水量达到11 821 m^(3)、压力达到23.46 MPa时,有断层失稳、诱发地震的可能;最大诱发地震的震源机制解为走滑型,主压应力NNW向,与华北区域应力分布有一定偏差,可见M1井开采对局部应力分布有影响;从地震震中位置迁移规律推测,有新的地裂缝产生。

雨养农业区冬小麦品种灌浆期抗旱耐逆性评价技术规程

为进一步推进抗旱耐逆小麦品种的快速筛选及其推广应用,提高耐旱育种效率,通过半干旱雨养农业区田间生产条件下灌浆期小麦气孔性状多年多点的测定,明确小麦灌浆期抗旱耐逆性判定规则,联合主成分分析和隶属函数值方法,从适用范围、规范性引用文件、术语和定义、技术原理、基本要求、田间管理、气孔性状调查分析、评价指标的计算及评价等级等方面总结出雨养农业区冬小麦品种灌浆期抗旱耐逆性综合评价技术规程。

考虑路面结构影响的低路堤动应力响应分析

以尼日利亚某公路为依托,对考虑路面结构层的砂砾填料低路堤在交通荷载作用下的动应力分布规律进行了研究。首先通过现场测试方法分析了行驶速度和轴重对路基动应力的影响,在此基础上建立三维有限元模型分析了不同路堤高度、不同超载率和不同路基填料模量对动应力分布的影响。现场测试结果表明:车辆的行驶速度越快,应力峰值越小,车重越重,路基内动应力越高,在路面较为平整的情况下,车重是影响路基动应力的主要因素,车速的影响较小。数值模拟结果表明:路基内动应力与路堤高度、超载率和路基填料的模量均成正比,路堤高度由1 m增加到2 m时,路基工作区由1.92 m下降到1.79 m,超载率由0增长到125%,路基工作区深度由1.77 m增加到2.73 m,增了54.2%,路基模量从80 MPa提高到160 MPa时,路基工作区深度从1.77 m下降到1.58 m,下降幅度为10.7%,试验结果表明超载对路基动应力的影响最大。结论为低路堤公路设计提供了参考。

多期构造应力控制走滑断控储层发育机理与差异性研究——以塔里木盆地顺北地区为例

塔里木盆地顺北油气田发育典型走滑断控缝洞型储层。区别于受原始沉积相带控制的基质孔洞、受岩溶改造的洞穴等储集类型,走滑断控缝洞型储层的形成主要受断裂活动期构造应力导致的破裂作用控制。为研究走滑断裂多期活动背景下构造应力控制的断控储层发育机理与分布规律,综合应用野外、岩心、测录井、地震及钻井动态等资料,开展不同走滑断裂、同一走滑断裂沿走向不同部位、垂向不同层系断控储层发育特征表征,并结合应力场数值模拟手段开展多期构造应力恢复,预测断控储层发育的主要时期与分布规律。结果表明,走滑断裂活动期不同分段内部应力状态差异显著,其中拉分段内部以张应力为主,主要派生张性裂缝;压隆段内部以挤压应力为主,派生裂缝类型多样。顺北地区勘探目的层奥陶系一间房组顶面断控裂缝主要在加里东中期Ⅲ幕及加里东晚期—海西早期发育,海西中—晚期及之后裂缝基本不发育,且滑移距大的顺北18号断裂带较顺北1号断裂带派生裂缝开度、密度更高。走滑断控储层具有“簇状”结构特征,断裂活动期不同分段内部应力状态控制储层结构差异,拉分段“空腔”多,以“双簇”结构为主,核带规模大,压隆段核带结构多,以“多簇”结构为主,分割性强;走滑断裂活动期应力强度控制储集空间类型与规模,小型断裂储集空间以裂缝为主,大型断裂带发育核带结构,断控储层规模与断裂活动强度呈正相关关系;断控裂缝发育主要受断裂早期活动控制,晚期由于地层埋深增大,岩石不易破裂,新派生裂缝发育较少。

城市交通节点明挖隧道回填方案优化

城市明挖隧道的修建需要大量的回填,回填选料和回填方案与施工质量紧密联系。以重庆市金州大道与星光大道延伸段节点改造工程为例,对砂卵石、不同含石量土夹石进行压缩模量匹配,选择工程最不利断面LK0+434,划分回填区域后采用应力面积法计算关键点的沉降值,结合工程经验优化深厚回填区施工方案。改良后的方案针结合砂卵石和土夹石的物理特征,降低了回填沉降峰值,挖方土得到合理调配重利用,避免了工程浪费,为类似工程提供了一定的参考。