Lateral earth pressure of granular backfills on retaining walls with expanded polystyrene geofoam inclusions under limited surcharge loading

Existing studies have focused on the behavior of the retaining wall equipped with expanded polystyrene(EPS)geofoam inclusions under semi-infinite surcharge loading rather than limited surcharge loading.In this paper,the failure mode and the earth pressure acting on the rigid retaining wall with EPS geofoam inclusions and granular backfills(henceforth referred to as EPS-wall),under limited surcharge loading are investigated through two-and three-dimensional model tests.The testing results show that different from the sliding of almost all the backfill in the EPS-wall under semi-infinite surcharge loading,only an approximately triangular backfill slides in the wall under limited surcharge loading.The distribution of the lateral earth pressure on the EPS-wall under limited surcharge loading is non-linear,and the distribution changes from the increase of the wall depth to the decrease with the increase of the limited surcharge loading.An approach based on the force equilibrium of a differential element is developed to predict the lateral earth pressure behind the EPS-wall subjected to limited surcharge loading,and its performance was fully validated by the three-dimensional model tests.

Limit state analysis of rigid retaining structures against seismically induced passive failure in heterogeneous soils

Soils are not necessarily uniform and may present linearly varied or layered characteristics,for example the backfilled soils behind rigid retaining walls.In the presence of large lateral thrust imposed by arch bridge,passive soil failure is possible.A reliable prediction of passive earth pressure for the design of such wall is challenging in complicated soil strata,when adopting the conventional limit analysis method.In order to overcome the challenge for generating a kinematically admissible velocity field and a statically allowable stress field,finite element method is incorporated into limit analysis,forming finiteelement upper-bound(FEUB)and finite-element lower-bound(FELB)methods.Pseudo-static,original and modified pseudo-dynamic approaches are adopted to represent seismic acceleration inputs.After generating feasible velocity and stress fields within discretized elements based on specific criteria,FEUB and FELB formulations of seismic passive earth pressure(coefficient K_(P))can be derived from work rate balance equation and stress equilibrium.Resorting to an interior point algorithm,optimal upper and lower bound solutions are obtained.The proposed FEUB and FELB procedures are well validated by limit equilibrium as well as lower-bound and kinematic analyses.Parametric studies are carried out to investigate the effects of influential factors on seismic K_(P).Notably,true solution of K_(P) is well estimated based on less than 5%difference between FEUB and FELB solutions under such complex scenarios.

Protective effect of retaining wall on rock avalanche:A case study of Nayong rock avalanche in China

Rock avalanches are generally difficult to prevent and control due to their high velocities and the extensive destruction they cause.However,barrier structures constructed along the path of a rock avalanche can partially mitigate the magnitudes and consequences of such catastrophic events.We selected a rock avalanche in Nayong County,Guizhou Province,China as a case to study the effect of the location and height of a retaining wall on the dynamic characteristics of rock avalanche by using both actual terrain-based laboratory-model tests and coupled PFC3D-FLAC3D numerical simulations.Our findings demonstrate that a retaining wall can largely block a rock avalanche and its protective efficacy is significantly influenced by the integrity of the retaining wall.Coupled numerical simulation can serve as a powerful tool for analyzing the interaction between a rock avalanche and a retaining wall,facilitating precise observations of its deformation and destruction.The impact-curve characteristics of the retaining wall depend upon whether or not the rock avalanche-induced destruction is taken into account.The location of the retaining wall exerts a greater influence on the outcome compared to the height and materials of the retaining wall,while implementing a stepped retaining-wall pattern in accordance with the terrain demonstrates optimal efficacy in controlling rock avalanche.

Mid-term outcomes of a kinematically designed cruciate retaining total knee arthroplasty

BACKGROUND Advances in implant material and design have allowed for improvements in total knee arthroplasty(TKA)outcomes.A cruciate retaining(CR)TKA provides the least constraint of TKA designs by preserving the native posterior cruciate ligament.Limited research exists that has examined clinical outcomes or patient reported outcome measures(PROMs)of a large cohort of patients undergoing a CR TKA utilizing a kinematically designed implant.It was hypothesized that the studied CR Knee System would demonstrate favorable outcomes and a clinically significant improvement in pain and functional scores.AIM To assess both short-term and mid-term clinical outcomes and PROMs of a novel CR TKA design.METHODS A retrospective,multi-surgeon study identified 255 knees undergoing a TKA utilizing a kinematically designed CR Knee System(JOURNEY™II CR;Smith and Nephew,Inc.,Memphis,TN)at an urban,academic medical institution between March 2015 and July 2021 with a minimum of two-years of clinical follow-up with an orthopedic surgeon.Patient demographics,surgical information,clinical outcomes,and PROMs data were collected via query of electronic medical records.The PROMs collected in the present study included the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement(KOOS JR)and Patient-Reported Outcomes Measurement Information System(PROMIS■)scores.The significance of improvements in mean PROM scores from preoperative scores to scores collected at six months and two-years postoperatively was analyzed using Independent Samples t-tests.RESULTS Of the 255 patients,65.5%were female,43.8%were White,and patients had an average age of 60.6 years.Primary osteoarthritis(96.9%)was the most common primary diagnosis.The mean surgical time was 105.3 minutes and mean length of stay was 2.1 d with most patients discharged home(92.5%).There were 18 emergency department(ED)visits within 90 d of surgery resulting in a 90 d ED visit rate of 7.1%,including a 2.4%orthopedic-related ED visit rate and a 4.7%non-orthopedic-related ED visit rate.There were three(1.2%)hospital readmissions within 90 d postoperatively.With a mean time to latest follow-up of 3.3 years,four patients(1.6%)required revision,two for arthrofibrosis,one for aseptic femoral loosening,and one for peri-prosthetic joint infection.There were significant improvements in KOOS JR,PROMIS Pain Intensity,PROMIS Pain Interference,PROMIS Mobility,and PROMIS Physical Health from preoperative scores to six month and two-year postoperative scores.CONCLUSION The evaluated implant is an effective,novel design offering excellent outcomes and low complication rates.At a mean follow up of 3.3 years,four patients required revisions,three aseptic and one septic,resulting in an overall implant survival rate of 98.4%and an aseptic survival rate of 98.8%.The results of our study demonstrate the utility of this kinematically designed implant in the setting of primary TKA.

基于RETAIN模型的对外汉字教育游戏的设计与开发

基于系统化的教学设计原则,Gunter等提出了RETAIN教育游戏设计模型,该模型能够很好地兼顾教育性与游戏性,受到广泛关注。以RETAIN模型为基础,结合对外汉字教学的相关研究成果,重点针对字形研发汉字教育游戏。首次构建出对外汉语汉字教育游戏的设计框架,并使用Unity3D进行PENZZLE的设计与开发,探讨教育性与游戏性的有机融合途径。调查结果显示,在学习兴趣提升、知识目标达成度、学习效果提升度三个方面,该游戏的开发都取得良好效果。

The Elist Drain Retainer: A New Adherent Drain Retainer with Antibacterial Properties

Background: Surgical drains are used in at least half of all surgical operations world-wide. The gold standard for the fixation of drains to the skin is currently the “Roman garter” (RG) technique, which involves knotting a suture around the drain. Its disadvantages include the time to perform the technique, possible loosening and accidental removal, and bacterial infection with biofilm formation if left in place for weeks. Methods: The Elist Drain Retainer (EDR) has been developed, and it consists of a short plastic tube bent to 90° with a side slit for the drain, fixed to a mounting patch with adhesive and an antiseptic. Results: In a clinical trial comparing 25 drain attachments with the RG versus 25 drain attachments with the new EDR, the former took an average of five minutes and the EDR took an average of one minute to place. Loosening occurred in five (20%) drains and accidental removal occurred in four (16%) for the RG group versus no incidences of loosening or accidental removal in the EDR group. Self-removal of the EDR was possible for seven (28%) patients. Conclusion: The EDR demonstrated a clear advantage over the RG in all tested parameters. The lack of instruments and the possibility of self-removal of the EDR when a drain is needed are particularly advantageous features.

Accuracy of Orthodontic 3D Printed Retainers versus Thermoformed Retainers

Background: The integration of the current technology of CBCT and 3D CAD/CAM technology has great potential in the field of orthodontics, which is not yet fully investigated. The purpose of this article is to evaluate the accuracy of 3D printed retainers in comparison to vacuum formed retainers. Methods: Alginate impressions were taken for ten patients who have a CBCT scan. A 3D printed retainer and vacuum formed retainer were fabricated. Linear measure-ments were measured by two assessors using digital caliper. Every measure-ment on the 3D printed retainer was compared to the corresponding measure-ment on the thermoformed retainer. The linear measurements were Inter-canine width, Inter-premolar width (first and second premolars), Inter-molar width, Canine-midline length (both sides) and Canine-molar length (both sides). Intra-observer, and inter-observer reliability measurements were done. Results: Results showed excellent intra-observer reliability for the thermoformed retainer and the 3D printed retainer. Inter-observer measurements showed strong agreement between the measurements of the two assessors, for both retainers. The comparison of the thermoformed retainer to the 3D printed retainer showed high statistical agreement, except for the canine-molar on the right side, but with no clinical significance, p value of 0.038 and mean difference 0.19. Conclusions: The new method for fabricating a 3D printed retainer is accurate and reliable in comparison to the vacuum formed retainer (conventional method). CBCT proved to be efficient for fabrication of a custom made appliances.

Dynamic modeling of fluid-conveying pipes restrained by a retaining clip

Although most pipes are restrained by retaining clips in aircraft,the influence of the clip parameters on the vibration of the fluid-conveying pipe has not been revealed.By considering the clip width,a new dynamic model of a fluid-conveying pipe restrained by an intermediate clip is established in this paper.To demonstrate the necessity of the proposed model,a half pipe model is established by modeling the clip as one end.By comparing the two models,it is found that the half pipe model overestimates the critical velocity and may estimate the dynamical behavior of the pipe incorrectly.In addition,with the increase in the clip stiffness,the conversion processes of the first two modes of the pipe are shown.Furthermore,by ignoring the width of the clip,the effect of the flow velocity on the accuracy of a concentrated restraint clip model is presented.When the flow velocity is close to the critical velocity,the accuracy of the concentrated restraint clip model significantly reduces,especially when the width of the clip is large.In general,the contribution of this paper is to establish a dynamic model of the fluid-conveying pipe which can describe the influence of the clip parameters,and to demonstrate the necessity of this model.

Stability Analysis of Landfills Contained by Retaining Walls Using Continuous Stress Method

An analytical method for determining the stresses and deformations of landfills contained by retaining walls is proposed in this paper.In the proposedmethod,the sliding resisting normal and tangential stresses of the retaining wall and the stress field of the sliding body are obtained considering the differential stress equilibrium equations,boundary conditions,and macroscopic forces and moments applied to the system,assuming continuous stresses at the interface between the sliding body and the retaining wall.The solutions to determine stresses and deformations of landfills contained by retaining walls are obtained using the Duncan-Chang and Hooke constitutive models.A case study of a landfill in the Hubei Province in China is used to validate the proposed method.The theoretical stress results for a slope with a retaining wall are compared with FEMresults,and the proposed theoreticalmethod is found appropriate for calculating the stress field of a slope with a retaining wall.

Effect of surface retaining elements on rock stability:laboratory investigation with sand powder 3D printing

This study aims to investigate the benefcial efects of surface retaining elements (SREs) on the mechanical behaviors of bolted rock and roadway stability. 3D printing (3DP) technology is utilized to create rock analogue prismatic specimens for conducting this investigation. Uniaxial compression tests with acoustic emission (AE) and digital image correlation techniques have been conducted on 3DP specimens bolted with diferent SREs. The results demonstrate that the strength and modulus of elasticity of the bolted specimens show a positive correlation with the area of the SRE;the AE characteristics of the bolted specimens are higher than those of the unbolted specimen, but they decrease with an increase in SRE area, thus further improving the integrity of the bolted specimens. The reinforcement efect of SREs on the surrounding rock of roadways is further analyzed using numerical modelling and feld test. The results provide a better understanding of the role of SREs in rock bolting and the optimization of rock bolting design. Furthermore, they verify the feasibility of 3DP for rock analogues in rock mechanics tests.

10kV箱变改造为发电机转子护环感应加热电源的研究与应用

在某核电站汽轮发电机转子首次检修和绕组发生绝缘缺陷时,需要采用感应加热法拆除转子护环进行检查与处理。本文结合电站实际情况及护环拆装需求,经过分析与计算,按照最优的单绕组供电方案将工程建设期退役的10kV箱式变电站改造成拆装发电机转子护环所需的感应加热电源,并在两台百万千瓦级汽轮发电机的首次大修和转子绝缘缺陷处理中实现成功应用,有效保障了核电站发电机大修工期,节约了大修成本。

切顶沿空留巷充填体—矸石协同承载机理及控制技术研究

针对深部沿空留巷顶底板移近量大、充填体大变形破坏失稳等问题,采用数值模拟和现场实践相结合的方法,分析了传统沿空留巷和切顶卸压协同承载沿空留巷围岩应力演化规律和变形特征,揭示了切顶沿空留巷充填体—矸石协同承载机理。在此基础上,以朱庄煤矿Ⅲ635工作面沿空留巷为工程背景,提出了一种巷旁充填体—矸石组合结构体协同承载的切顶卸压沿空留巷技术,建立充填体—矸石协同支撑顶板力学模型、推导出顶板挠度方程,并进行工程应用。数值模拟结果表明:采用切顶卸压协同承载沿空留巷技术后,实体煤帮和充填体的垂直应力峰值分别降低了28.3%、44.4%,巷道顶底板移近量降低了58.2%。现场应用结果表明:采用该技术后,顶底板和两帮移近量分别为382.9、253.6 mm,工作面支架平均支撑力下降了45.3%,有效控制了巷道变形。可为类似条件下沿空留巷围岩控制提供参考。

贵州沿空留巷支护技术的分析与改进

针对贵州某煤矿沿空留巷在原有支护条件下,靠上帮一侧顶板以及下帮底角的岩层变形破坏较严重的情况,对巷道支护方式进行改进。利用数值模拟软件,对改进支护后的巷道围岩变形破坏情况进行分析。研究发现:改进支护后的巷道围岩变形破坏情况得到明显改善,改进后的支护方式能够较好地阻滞巷道上帮一侧顶板和下帮底角的岩层严重变形破坏,从而保持巷道围岩的完整性和稳定性,研究可为类似条件矿井沿空留巷的支护方式提供参考。

千米深井切顶卸压自成巷支护技术及应用

为了解决深部复杂条件下的切顶卸压自成巷难题,以红阳三矿703工作面运输巷道为研究对象,从恒阻大变形锚索超前支护、切顶巷内支护、切顶巷旁支护三个方面研究了切顶卸压沿空成巷支护技术,并对现场试验巷道顶板受力以及巷道围岩变形量进行了监测。结果表明:在超前工作面实施爆破切顶能够极大降低巷道所受应力,成巷区巷道顶板整体下沉量较小,巷中顶板最大下沉量约385 mm,平均下沉量约280 mm,巷中底鼓最大值545 mm,碎石巷帮无明显侧鼓现象,实体煤帮无明显片帮现象,满足安全和使用要求,巷道围岩变形在可控范围内,留巷效果良好。

不同酶解程度对留胚米粉理化性质及消化性的影响研究

研究不同酶解程度对留胚米粉理化性质及消化性的影响,以留胚米为原料,制备不同酶解程度的留胚米粉,考察不同酶解程度对留胚米粉的营养成分、色度、粒径、水合特性、糊化特性、红外光谱和体外消化特性的影响。结果表明,留胚米粉经过不同酶解时间处理后,淀粉含量降低,淀粉粒径减小;淀粉结块率先减小后增大,当DE值为19.98%±0.78%时淀粉结块率最低;淀粉分散时间缩短,溶解度增大;酶解米粉中淀粉的峰值黏度、谷值黏度、衰减值、最终黏度、回生值和淀粉黏度到达峰值的时间均显著降低;且淀粉的短程有序性受到破坏;快消化淀粉(RDS)含量显著增加。综上所述,当DE值为19.98%±0.78%时,酶解留胚米粉的综合性质最佳。

Hawley保持器戴用后咬(牙合)变化的数字化分析

目的 分析正畸完成后患者佩戴Hawley保持器前后的咬(牙合)状态,以评估在牙齿保持过程中Hawley保持器对咬(牙合)产生的变化。方法选取固定拔牙矫治结束,并拆除矫治器后即刻佩戴Hawley保持器的患者20例。应用iTero扫描仪记录正畸结束即刻(T1)及正畸结束后6个月(T2)牙尖交错位的咬(牙合)接触。比较T1和T2期全牙弓、前后段和左右侧咬(牙合)接触面积、接触点数目的变化。结果 T2期后段牙弓、左右侧牙弓、总牙弓的咬(牙合)接触面积和接触点数目比T1期增加(P<0.05);前段牙弓的咬(牙合)接触面积和接触点数目在T1期与T2期差异无统计学意义(P>0.05)。T2期咬(牙合)接触间距范围0~0.2 mm时的咬(牙合)接触点均在T1期咬(牙合)接触间距范围0~1.0 mm,表明牙齿发生牙尖磨耗的生理性调整。结论 正畸固定治疗结束后佩戴Hawley保持器,有利于后牙合发生生理性调整,咬(牙合)稳定性和紧密性有明显的改善,但对前牙咬(牙合)影响较小。

含建筑桩基的顺层岩质边坡桩锚支护体系振动台模型试验研究

基于Bockinghamπ定理,对具有建筑桩基的顺层岩质边坡桩锚支护体系开展振动台模型试验,通过分析预应力锚索、建筑桩基的应变以及边坡坡顶加速度,研究支护体系的动力响应规律。结果表明,预应力锚索的应变在地震波加速度达到峰值时达到最大值,且上排锚索受力大于下排锚索,随着地震幅值的增大,最上排锚索锚固段率先发生滑移破坏失去锚固作用;建筑桩基应变最大值点位于滑动面以下一定深度,且远离边坡坡面的建筑桩基受力大于邻近边坡坡面的建筑桩基;坡顶各点峰值加速度随地震波幅值增大整体表现为线性增大,但在Wenchuan-Wolong波(0.55g)和Sin波(0.4g)工况时,各点峰值加速度相对有所下降,随着地震波幅值增大,各点峰值加速度放大系数在汶川波和正弦波作用下并非单调变化,而是表现为先减小后增大波动变化特点。

基于遗传算法的空箱式挡土墙多目标优化设计

为高效、准确、自动化地实现空箱结构的优化设计,以空箱式挡土墙为研究对象,基于Python语言和ABAQUS软件进行参数化建模,实现了结构建模及有限元计算分析全套流程的自动化。结合某水闸工程中的一座空箱式挡土墙结构,以多个强度和稳定性指标的最优化和混凝土体积的最小化为目标,以规范要求的指标阈值、几何尺寸和体积限制为约束条件,采用非支配排序遗传算法(NSGA-Ⅱ算法)进行空箱式挡土墙多目标优化设计。为进一步提高计算效率,基于人工神经网络算法建立了代理模型,实现了与实际有限元模型的高度近似。结果表明,依据所提出的优化设计方法进行空箱式挡土墙多目标优化设计,可以在有效控制强度和稳定性的前提下尽可能地缩减混凝土用量,具有显著的经济效益。

胎衣不下奶牛miRNA-185靶向调控血管内皮生长因子A表达的研究

【目的】通过体内和体外试验检测miRNA-185及血管内皮生长因子A(vascular endothelial growth factor A,VEGFA)在胎衣正常排出和胎衣不下(RFM)奶牛胎盘组织中的差异表达情况及VEGFA在奶牛母体胎盘组织中表达分布,验证及明确miRNA-185和VEGFA与奶牛胎衣不下发生密切相关并存在靶向调节关系,为深入研究miRNA-185在奶牛胎衣不下发生过程中的作用提供理论依据和试验基础。【方法】采用实时荧光定量PCR法检测胎衣正常排出及胎衣不下奶牛母体胎盘组织中miRNA-185及VEGFA基因表达情况,采用荧光原位杂交技术(FISH)检测VEGFA在母体胎盘组织的表达分布及mRNA的差异表达情况;采用双荧光素酶明确miRNA-185与VEGFA的靶向调节关系,采用实时荧光定量PCR及Western blotting检测体外转染miRNA185 mimics、miRNA-185 inhibitor及miRNA-185 NC后VEGFA mRNA及蛋白的差异表达情况。【结果】实时荧光定量PCR结果显示,与胎衣正常排出奶牛相比,胎衣不下奶牛体内miRNA-185及VEGFA的表达水平均极显著下调(P<0.01);荧光原位杂交结果显示,VEGFA mRNA主要在奶牛子宫内膜上皮细胞中表达。VEGFA是miRNA-185的靶向调节蛋白。与阴性对照组相比,转染miRNA-185 mimics后VEGFA的mRNA及蛋白表达水平均极显著下调(P<0.01),转染miRNA-185 inhibitor后VEGFA的mRNA及蛋白表达水平均极显著上调(P<0.01)。【结论】胎衣不下奶牛母体胎盘组织内miRNA-185及VEGFA表达显著降低,VRGFA主要在子宫内膜上皮细胞中表达,miRNA-185可通过靶向调控VEGFA的表达参与奶牛胎衣不下的发生发展。

台阶级数对加筋土挡墙地震动力响应影响研究

为了优化加筋土挡墙的结构设计,研究了台阶级数对加筋土挡墙抗震性能的影响程度。基于Flac3D软件建立了加筋土挡墙数值模型,探讨了不同地震峰值加速度(peak ground acceleration,PGA)下不同台阶级数加筋土挡墙的侧向位移、竖向沉降、加速度响应和水平土压力的变化规律。结果表明:4 m/s^(2)峰值加速度下,增加台阶级数,侧向位移减小了61.9%,竖向沉降减小了20.5%;PGA放大系数随着台阶级数的增加而增大,其中加筋区PGA放大系数略大于面板处PGA放大系数;1级加筋土挡墙最大水平土压力位于墙脚处,2,3级加筋土挡墙最大水平土压力位于台阶分级处;水平土压力在台阶分级处大于规范计算值。增加台阶级数能够提升加筋土挡墙的抗震性能,可为实际工程中加筋土挡墙的分级设计提供理论参考。