An approach for determination of lateral limit angle in kinematic planar sliding analysis for rock slopes

Planar sliding is one of the frequently observed types of failure in rock slopes.Kinematic analysis is a classic and widely used method to examine the potential failure modes in rock masses.The accuracy of planar sliding kinematic analysis is significantly influenced by the value assigned to the lateral limit angleγlim.However,the assignment ofγlim is currently used generally based on an empirical criterion.This study aims to propose an approach for determining the value ofγlim in deterministic and probabilistic kinematic planar sliding analysis.A new perspective is presented to reveal thatγlim essentially influences the probability of forming a potential planar sliding block.The procedure to calculate this probability is introduced using the block theory method.It is found that the probability is correlated with the number of discontinuity sets presented in rock masses.Thus,different values ofγlim for rock masses with different sets of discontinuities are recommended in both probabilistic and deterministic planar sliding kinematic analyses;whereas a fixed value ofγlim is commonly assigned to different types of rock masses in traditional method.Finally,an engineering case was used to compare the proposed and traditional kinematic analysis methods.The error rates of the traditional method vary from 45%to 119%,while that of the proposed method ranges between 1%and 17%.Therefore,it is likely that the proposed method is superior to the traditional one.

Investigation on the effect of beam divergence angle upon output waveform based on stimulated Brillouin scattering optical limiting

This paper investigates the effect of beam divergence angle on output waveform based on stimulated Brillouin scattering optical limiting.Output waveforms in the case of different pump divergence angles are numerically simulated,and validated in a Nd：YAG seed-injected laser system.The results indicate that a small pump divergence angle can lead to good interaction between pump and Stokes,and a platform can be easily realized in the transmitted waveform.In contrast,a peak followed by the platform appears when the divergence angle becomes large.

Joint member angle limits of composite beams and CFT square columns

This work aims to understand the relationship between the member angle limit and the energy ratio for 24 test samples of composite beams and CFT square steel tube columns. This work also compares the formula applicability for member angle limit with the previous test result to provide the basic data for the design of composite beam-CFT column. The evaluation of the member angle limit was performed with concrete compressive strength (fC =22.16 MPa, 30.49 MPa), breadth-to-thickness ratio (B/t=25.0, 33.3, 43.5), and axial capacity ratio (N/N0=0, 0.3, 0.4, 0.5) as the main variables of the test samples. For the relationship between the member angle limit (Ru) and the energy ratio (ES/EC ), the test result shows that the energy ratio becomes lower as the axial capacity ratio and the breadth-to-thickness ratio increase. The energy ratio is lower for the Type B test sample compared with that of Types A and C. For the formula suggested by SATO, the test samples are distributed evenly for comparison between test values and the member angle limit; however, other formulas indicate a deviation. Specifically, for the comparison between R u,cal and R u (Test), Maeda's formula shows severe deviation.

Combined treatment of phacoemulsification and single-port limited pars plana vitrectomy in acute angle-closure glaucoma

AIM: To evaluate the efficacy of combined treatment of phacoemulsification(PE) and micro-incisional single-port transconjunctival limited pars plana vitrectomy(PPV) in acute angle-closure glaucoma(AACG).METHODS: A retrospective study included 26 patients who underwent PE diagnosed with AACG. Among them, 16 patients(16 eyes) underwent PE alone, 10 patients(10 eyes) underwent combined limited vitrectomy and PE. Then we compared intraocular pressure(IOP), anterior chamber angle, anterior chamber depth, central corneal thickness and corneal endothelial cell count before and after surgery, and effective PE time during cataract surgery.RESULTS: Effective PE time was shorter in the combined surgery group than in the single surgery group(P=0.040). There was no statistically significant difference in IOP and best-corrected visual acuity between the two groups postoperatively. At 6 mo postoperatively, there was no difference in the anterior chamber angle, anterior chamber depth, and central corneal thickness between two groups, but corneal endothelial cell count was higher in the combined surgery group than in the single surgery group(P=0.046). No complication such as vitreoretinal disease, endophthalmitis, bullous keratopathy was noted.CONCLUSION: Combined micro-incisional single-port transconjunctival limited PPV and PE are more effective and safer than PE alone because of less operation time and fewer complications for management of AACG.

Limitations of Lightning Rods in Preventing Direct Lightning Strikes

Since ancient times,lightning disasters have undoubtedly been an unstoppable threat to humanity.During thunderstorms,lightning often damages objects on the ground,such as buildings and structures.Since Franklin invented the lightning rod in 1752,lightning rods have been used worldwide to prevent direct lightning strikes in various fields such as high-voltage power transmission lines,outdoor chemical sites,highways,land and sea wind farms,and forest lightning fire protection.It has been proven that lightning accidents still occur frequently in places where lightning rods are installed and the protective angle method is used.In order to further study the protective effect of lightning rods and identify the shortcomings of lightning rod protection,negative lightning strikes are taken as the research object,to analyze the limitations of lightning rods in preventing direct lightning strikes from the working principle of lightning rods.

New Approach for Limited-Angle Problems in Electron Microscope Based on Compressed Sensing

New advances within the recently rediscovered field of Compressed Sensing (CS) have opened for a great variety of new possibilities in the field of image reconstruction and more specifically in medical image reconstruction. In this work, a new approach using a CS-based algorithm is proposed and used in order to solve limited-angle problems (LAPs), like the ones that typically occur in computed tomography or electron microscope. This approach is based on a variant of the Robbins-Monro stochastic approximation procedure, developed by Egaziarian, using regularization by a spatially adaptive filter. This proposal consists on filling the gaps of missing or unobserved data with random noise and enabling a spatially adaptive denoising filter to regularize the data and reveal the underlying topology. This method was tested on different 3D transmission electron microscope datasets that presented different missing data artifacts (e.g, wedge or cone shape). The test results show a great potential for solving LAPs using the proposed technique.

型钢混凝土T形截面剪力墙基于性能的变形限值研究

为更好地评估T形截面型钢混凝土(steel reinforced concrete,SRC)剪力墙变形性能,采用ABAQUS有限元软件对按照规范设计的324个T形截面SRC剪力墙构件的破坏形态和变形性能进行研究,根据收集的试验数据分析构件的破坏形态,提出T形截面SRC剪力墙的破坏形态划分准则;以构件的各材料应变极限值为准则来判别构件的性能状态,考虑轴压比、剪跨比、弯剪比、腹板暗柱配钢率、暗柱纵筋配筋率及箍筋暗柱特征值对构件变形性能的影响。对不同性能状态变形限值和参数进行线性回归分析,得到不同破坏类型下各性能状态位移角限值计算式;按规范ASCE 41修正各性能状态变形限值的失效概率,得到具有15%、20%、35%失效概率保证的各性能状态变形限值取值表。研究表明:剪跨比、轴压比对构件各性能状态位移角限值影响较大,暗柱腹板配钢率、纵筋配筋率及箍筋特征值对构件位移角限值影响相对较小,但能提高其延性。按规范ASCE 41修正后的位移角限值取值较为合理且有一定的安全储备。为T形截面SRC剪力墙基于性能的抗震设计与性能评估提供参考。

基于桨距角控制的永磁风电机组高电压穿越控制策略

为解决传统永磁风电机组高电压穿越控制策略存在超速脱网风险问题,提出一种基于桨距角控制的高电压穿越控制策略。高电压穿越期间,首先,按照并网要求向电网提供无功支撑;其次,考虑转子转速限制,当转子转速达到参考值时启动桨距角控制,抑制转子转速上升;最后,通过仿真试验,验证了所提控制策略的有效性。基于桨距角控制的永磁风电机组高电压穿越控制策略,既能向电网提供无功支撑,又能避免超速脱网。

有限空间作业条件下中小桥梁加固安全施工及风险管理

以某现浇箱梁的维修加固工程为依托,分析了有限空间条件桥梁维修加固工程的施工安全风险以及应对措施。工程具有工作面高度极其有限、工序复杂、风险因素多等不利因素。利用风险源评估方法LEC评价法对风险因素进行评估,对重点的风险因素进行监控管理,并总结了恶劣施工条件下的安全措施要点,工程期间未发生安全事故,为后续公路工程箱梁内部维修加固工程提供一定的参考价值。

基于实际触发角响应的连续换相失败抑制方法

针对逆变侧交流故障下高压直流(line commutated converter-high voltage direct current,LCC-HVDC)输电系统易引发连续换相失败问题,该文分阶段分析了连续换相失败的产生机理。明确了当产生触发角偏差后,直流电流调节效果与实际触发角不匹配是连续换相失败的重要诱因。同时不对称故障后,负序分量通过极控、阀控两级控制系统对实际触发角造成的影响,增加连续换相失败的风险。因此提出了一种基于实际触发角响应的连续换相失败抑制方法,通过实际触发角修正整流侧电流指令值。与此同时,该方法通过陷波器降低负序电流对极控层触发角指令值的影响,通过相序解耦控制器和换相电压相位补偿降低负序电压对阀控层触发角实际值的影响。该方法能实现动态、自适应的电流指令值调整,提升恢复过程中直流电流与实际触发角的匹配度,提升直流系统抵御连续换相失败能力。在CIGRE标准测试模型和实际工程模型中,验证了理论分析的正确性和优化方法的有效性。

螺纹参数误差对钻杆接头密封性的影响分析

为探究钻杆接头螺纹参数极限误差对其密封性的影响,基于API NC38钻杆接头,分析了锥度、牙侧角和螺距3种螺纹参数极限误差的存在情况,建立了12种内、外螺纹极限误差组合的钻杆接头有限元模型,分析了不同误差组合的钻杆接头在上扣扭矩单独作用、上扣扭矩和轴向载荷组合作用下的密封性和应力分布。分析结果表明:螺距极限误差对钻杆接头密封性影响最为明显,且极易出现接触面屈服失效的情况;锥度极限误差使钻杆接头在受拉伸载荷时密封性显著降低;内外螺纹牙侧角极限误差变化情况相反时,钻杆接头局部出现塑性变形,影响密封效果。因此钻杆接头螺纹加工时有必要进一步控制螺纹参数的误差范围,避免出现标准规定的极限误差,降低钻杆接头密封失效的风险。研究结果可为快速、安全钻井提供技术支撑。

着角与攻角联合作用下薄芳纶层合板抗平头弹侵彻性能

为探究着角和攻角对薄芳纶层合板抗平头弹侵彻性能的影响,建立了三维有限元仿真模型,对4 mm厚芳纶层合板在着角单独作用下以及着/攻角联合作用下的弹道行为进行了计算.通过弹丸的剩余速度、靶板的极限弹道速度及穿孔能量阈值反映了芳纶层合板的抗侵彻性能,分析了其在不同工况下的变形与破坏机理.结果表明:薄芳纶层合板的弹道极限速度随初始着角的增加先减小后增大;随着入射速度的增大和初始着角的减小,着角改变量和攻角改变量均有减小的趋势;对于固定的着角,负攻角不利于子弹侵彻,正攻角有利于侵彻.

基于离散元模拟的不同挡土墙位移模式下非极限主动土压力

针对刚性挡土墙主动位移过程中砂土非极限主动土压力问题,利用PFC 2D分别对挡土墙绕墙顶转动(RB)模式、绕墙顶转动(RT)模式和平动(T)模式下砂土主动破坏过程进行模拟分析。分析结果表明,不同位移模式下土体内摩擦角及墙土摩擦角调动规律存在差异。挡土墙主动位移过程中,RB模式下土体破坏从墙顶开始,向墙脚发展,土楔体内部只有靠近墙背侧区域出现主应力偏转现象,并且土楔体中内摩擦角调动值均能达到极限值。RT模式下,土体破坏沿着墙背和滑裂面从墙脚开始,向土体表面发展,墙后土楔体中上部区域主应力偏转角度较大,形成了大主应力拱,与此对应的是该区域内摩擦角调动值相对初始内摩擦角减小。T模式下,土体破坏分别沿着墙背从墙顶向墙脚发展以及沿着滑裂面从墙脚向土体表面发展,墙后土楔体内部会出现小主应力拱,且内摩擦角调动值从初始内摩擦角增加,但达不到极限值。

有限转角力矩电机电磁转矩与霍尔感应磁场研究

永磁式齿槽式集中绕组形式有限转角力矩电机一般具有较小的气隙,进而可以增加电机的气隙磁密幅值,提高力矩输出能力。根据这一优势,通过理论设计和有限元仿真软件设计出一种符合基本性能要求的旋转式直驱阀有限转角力矩电机,并研究了充磁方向、斜槽对齿槽转矩和输出转矩的影响,从而达到抑制转矩波动、改善转矩波形的目的。根据线性霍尔具有体积小、反馈信号线性度好等优点,选用线性霍尔接收信号,并研究霍尔位置和偏心距对霍尔波形畸变率的影响。研究表明,对霍尔波形进行优化后成功将谐波畸变率从最初的4.9%降低到0.1%以下,这在工程研究领域具有重要参考意义。

"Skeleton" and "Spirit" of Architecture——With the Library in Henan University of Urban Construction as a Study Case

This study,taking the library in Henan University of Urban Construction for an example,points out that constant elements in the evaluation system of architecture are its "skeleton" and "spirit",that is,"space" and "spirit of place".Through analyzing the significant role of space in modern architecture and the appeal of spirit of place to construction users,it is explained that space and spirit of place are closely related and mutually dependent.

永磁有限转角力矩电机的仿真与实验

随着多电飞机的快速发展及成附件轻小化、高效能的迫切需求,有限转角力矩电机(Limited Angle Torque Motor,LATM)在飞机引气系统中的应用日益迫切。一方面,有限转角力矩电机可以显著简化高温引气控制阀结构、减小体积;另一方面,可以基于系统需求实现引气压力和温度按需调节,减少燃油代偿损失。针对高温有限转角力矩电机工作特性不易预测的难题,建立了其数学模型、仿真模型,并通过实物试验验证了仿真模型的准确性。研究结果为有限转角力矩电机特性研究提供了参考依据。

植入式钛钉颌间牵引联合钛板内固定治疗下颌角骨折患者的效果分析

目的探讨植入式钛钉颌间牵引联合钛板内固定对下颌角骨折患者疼痛、咀嚼和张口受限的影响。方法本研究为随机对照试验。选取2019年9月至2023年9月延安大学附属医院收治的下颌角骨折患者108例,使用随机数字表法分为观察组与对照组,每组54例。观察组男31例,女23例;年龄(46.21±5.03)岁,骨折部位:左侧26例,右侧28例,接受植入式钛钉颌间牵引联合钛板内固定治疗;对照组男33例,女21例;年龄(45.79±6.18)岁,骨折部位:左侧29例,右侧25例,接受牙弓夹板颌间牵引外固定联合钛板内固定治疗。比较两组手术前后视觉模拟评分法(VAS)评分、咀嚼功能、张口度、下颌活动度变化,并评估两组术后3个月时愈合情况。采用χ^(2)检验、秩和检验、t检验。结果术后1个月、3个月,两组VAS评分均低于术前,且观察组均低于对照组[(2.03±0.86)分比(2.49±0.71)分、(0.22±0.05)分比(0.29±0.07)分](t=3.031、5.980,均P<0.05);两组咀嚼功能评分均高于术前,且观察组均高于对照组[(5.76±1.13)分比(5.02±1.07)分、(8.65±0.67)分比(8.23±0.59)分](t=3.494、3.457,均P<0.05);两组张口度、下颌前后活动度均大于术前,且观察组均大于对照组(均P<0.05)。观察组一期愈合29例、二期愈合23例、三期愈合2例,对照组一期愈合22例、二期愈合21例、三期愈合11例,差异有统计学意义(Z=3.971,P=0.046)。结论植入式钛钉颌间牵引联合钛板内固定治疗下颌角骨折效果显著,可以减轻患者疼痛,改善咀嚼功能和张口受限程度,促进骨折愈合。

限制负载角的永磁同步电机序列模型预测控制

针对永磁同步电机模型预测控制中增加负载角限制函数可以避免电机失步但会导致模型预测控制权重系数调节更加繁琐的问题,提出了一种可限制负载角的永磁同步电机无权重系数模型预测控制。该方法基于字典法实现模型预测控制,对目标函数进行分层序列优化,实现无权重系数下的多目标优化。为验证该方法的有效性,进行了仿真和实验研究。结果表明,本方法可以实现负载角限制且动静态性能与传统方法一致,与传统方法相比,转矩与磁链的稳态误差相近,约为0.3N·m和0.005V·s,但省去了权重系数的调整,减少了计算负担。

基于FPGA的有限转角力矩电机伺服阀控制器设计

介绍了有限转角力矩电机在伺服阀中的应用,给出了有限转角力矩电机控制器的总体设计方案,提出基于FPGA的位置环、速度环、电流环三闭环的控制策略,论述了数字PID控制算法和控制器的软硬件设计,采用MATLAB对控制策略进行仿真分析,并利用样机进行试验验证。结果表明,控制器性能与仿真分析结果一致,具有响应速度快、无超调等优点,达到了设计目标,满足任务需求。

异地异级调用检察官的有“限”性

异地异级调用检察官存在诸多限制。调用主体上,仅限于上级检察院调用下级检察院检察官。调用内容上,应限于检察行政事务,而不包括出庭公诉等内容。法理依据上,我国检察官的调用应首先契合检察机关检察权产生和负责的体制特殊性以及地方检察官任免的地域依附性。调用目的上,该行为有悖于刑事诉讼保障犯罪嫌疑人、被告人权益的理念,且易忽视检察机关自身法律监督的职能定位,欠缺正当性、合理性。