EFFECT OF THE CONTROLLED ROLLING CONTROLLED COOLING ON STRENGTH AND DUCTILITY OF THE BAINITE MICRO ALLOYED ENGINEERING STEEL

The continuous cooling transformation of hot deformation austenite austenite of test steel and the effect of different processing schedules of controlled rolling and controlled cooling on the strength and ductility have been studied. The theory and the experiment base are presented for controlled rolling and controlled cooling of the SBL micro alloyed engineering steel.

Polyacrylamide hydrogel application in sand control with compressive strength testing

Sand production is one of the major problems in sandstone reservoirs. Different mechanical and chemical methods have been proposed to control sand production. In this paper, we propose a chemical method based on using polyacrylamide/chromium triacetate hydrogel to investigate sand production in a synthetic sandpack system. To this end, a series of bulk experiments including the bottle test and rheological analysis along with compression tests were conducted. Experimental results indicated that the compressive strength of the sandpack was increased as much as 30 times by injecting 0.5 pore volume of hydrogel. Also, it was found that the increases in cross-linker and polymer concentrations exhibited a positive impact on the compressive strength of the sandpack, mostly by cross-linker concentration(48 psi). Hydrogel with a higher value of cross-linker could retain its viscoelastic properties against the strain which was a maximum of 122% for 0.5 weight ratio of cross-linker/polymer. The presence of salts, in particular divalent cations, has a detrimental effect on the hydrogel stability. The maximum strain value applied on hydrogel in the presence of CaCl_2 was only about 201% as compared to 1010% in the presence of distilled water. Finally, thermogravimetric analysis and its derivative showed that the hydrogel could retain its structure up to 300 °C. The results of this study revealed the potential application of the hydrogel to control sand production.

CHARACTERISTICS OF STRENGTH CONTROL OF ADAPTIVE STRUCTURE WITH ELECTROMECHANICAL COUPLING

Based on the programming method, an electromechanical coupling adaptive statically indeterminate truss structure is controlled for increasing its load capacity. Several main parameters during the process of design of the adaptive structure are selected for a study of its characteristic during the control stage. The curves of each parameter for the effect of control results are plotted and corresponding conclusions are drawn. Thus, the theoretical basis is presented for optimal design, manufacture and control of the adaptive structure.

Multi-Variable Flocking Control for Multi-Agent Systems via a Received Signal Strength Indicator

A novel flocking control approach is proposed for multi-agent systems by integrating the variables of velocities, motion directions, and positions of agents. A received signal strength indicator （RSSI） is applied as a variable to estimate the inter-distance between agents. A key parameter that contains the local information of agents is defined, and a multi-variable controller is proposed based on the parameter. For the position control of agents, the RSSI is introduced to substitute the distance as a control variable in the systems. The advantages of RSSI include that the relative distance between every two agents can be adjusted through the communication quality under different environments, and it can shun the shortage of the limit of sensors. Simulation studies demonstrate the effectiveness of the proposed control approach.

Properties of Rapid Hardening Controlled Low Strength Material Made of Recycled Fine Aggregate from Urban Red Brick Construction Waste

In some cases of emergency backfill engineering projects, traditional backfill materials cannot meet the requirements of fast construction due to their long curing time. This study presents a new kind of rapid hardening controlled low strength material, which utilizes both rapid hardening sulphoaluminate cement and recycled fine aggregate from urban red brick construction waste. Totally, sixteen mixtures were prepared for the experiment with different cement-to-sand ratios and water-to-solid ratios. The flowability and bleeding rate of fresh mixture were measured to evaluate its workability, and the compressive strength of hardened mixture was tested to evaluate its rapid hardening and mechanical properties. Test results indicate that rapid hardening controlled low strength material containing recycled fine aggregate from urban red brick construction waste can achieve the desirable flowability, but the bleeding rate increases with the increase of flowability. In addition, 2-hour compressive strength can reach 0.08 - 0.12 MPa, and 4-hour compressive strength is 0.32 - 1.54 MPa, which can meet the requirements of emergency backfill construction. At last, based on the derived compressive strength, a fitting model for predicting compressive strength evolution of this new rapid hardening backfill material is developed, which fits accurately with these experimental data.

Does Change in the Effect of Source Strength of the High Dose Rate ¹⁹²Iridium Radio-Isotope on Local Control and Late Normal Tissue Toxicity (Bladder and Rectum) in the Treatment of Carcinoma Cervix

Aim: To analyse and assess the effect of dose rate of 192ir-source strength on late complications and local control rate during treatment of carcinoma cervix. Materials and Methods: One hundred and two cases of carcinoma cervix were included in the study. All patients were treated with a curative intent with radical dose of radiation as per the department protocol. All patients were treated with both EBRT plus Brachytherapy with Inj. Cisplatin 40 mg/m2 weekly. Patients were divided into 2 groups based on activity i.e. group A (10-6Ci) and group B (5-2Ci). After brachytherapy, point doses were analysed based on ICRU 38 recommendations. During follow up, morbidities were evaluated using RTOG grading system. Results: There was no difference in local control and distant metastasis in both groups after six months of follow up. Late Complications were comparable in both groups irrespective of source strength. Bladder complications were minimal with no significant difference in both study groups. Further Patients were divided into four groups i.e. BED of ICRU rectal point (3 and ≥100 Gy3) and source strength (10-6Ci and 5-2Ci), when BED was >100 Gy3 resulted in higher late rectal complication rate (P 3. Conclusion: This study suggests that change in source activity did not make a difference in local control, late rectal and bladder morbidities at 6 months of follow up. Longer follow up is required to assess long term results and morbidities.

日本HEAS-02-2022《医院设施设计指南(空调设备篇)》介绍

日本HEAS-02《医院设施设计指南(空调设备篇)》已经持续应用了30多年,对我国医院建设影响较大。历经4次修订,最新颁布的2022版是由医学主席在疫情中主持修订的,鉴于气溶胶新的传播特性提出了相应的合适措施。在医疗环境控制方面提出了许多新的思路与措施,局部修订了空气洁净度级别和各医疗科室的通风要求。依据感染管理风险评估及推荐强度与证据质量实施合理的医疗环境控制,并对一些关注点进行了澄清。

碳纳米管增强铝基复合材料界面与晶粒调控研究进展

随着碳纳米管增强铝基复合材料制备工艺的不断完善,碳纳米管的难分散问题被妥善解决,复合材料的强度有所提高,但复合材料的高模量、高强度没有得到充分利用,并出现“强度–塑性”倒置现象。本文总结了近年来对碳/铝复合材料界面结构、晶粒结构与复合构型设计的调控手段,讨论了界面结构强度对碳纳米管载荷传递效率的影响,分析了出现倒置现象的原因,并针对复合材料塑韧性差的问题,提出了调控思路,为制备强度高、韧性强的碳纳米管增强铝基复合材料提供依据。

Reliable evaluation method of quality control for compressive strength of concrete

Concrete in reinforced concrete structure (RC) is generally under significant compressive stress load. To guarantee required quality and ductility, various tests have to be conducted to measure the concrete’s compressive strength based on ACI (American Concrete Institute) code. Investigations of recent devastating collapses of structures around the world showed that some of the collapses directly resulted from the poor quality of the concrete. The lesson learned from these tragedies is that guaranteeing high quality of concrete is one of the most important factors ensuring the safety of the reinforced concrete structure. In order to ensure high quality of concrete, a new method for analyzing and evaluating the concrete production process is called for. In this paper, the indices of fit and stable degree are proposed as basis to evaluate the fitness and stability of concrete’s compressive strength. These two indices are combined to define and evaluate the quality index of the compressive strength of concrete. Prin-ciples of statistics are used to derive the best estimators of these indices. Based on the outcome of the study, a concrete compres-sive strength quality control chart is proposed as a tool to help the evaluation process. Finally, a new evaluation procedure to assess the quality control capability of the individual concrete manufacturer is also proposed.

大型耙吸挖泥船结构设计要点

为实现大型耙吸挖泥船结构设计安全、合理、可靠,以某大型耙吸挖泥船为例,分析大型耙吸挖泥船结构设计特点,从结构设计、强度评估、疲劳评估和振动评估等角度论证其设计要点,通过对泥舱结构设计分析,给出泥舱设计的关键节点,对关键节点进行强度分析和疲劳分析,结果表明,该船局部关键区域应力水平较高,低周疲劳在关键区域的疲劳中占据主要地位,建立三维有限元模型计算挖泥船固有频率,对比该大型耙吸挖泥船激励频率与固有频率,结果表明,船体总振动固有频率通常可以避开激励频率,生活楼固有频率与激励频率较为接近。

金沙江上游白格滑坡黏土化蚀变岩的灾变力学行为研究

金沙江构造结合带是典型的板块碰撞作用形成的构造混杂岩带,不仅地质结构复杂,而且发育了工程特性极差的特殊岩土体。本文在金沙江上游白格滑坡成因机理调查与分析过程中,新发现了巨型滑坡体后缘滑壁发育厚度较大、分布较连续的黏土化蚀变岩,是构成滑动带的重要组分。基于相关样品的原位测试和室内系统的物质组成、耐崩解、环形剪切、动三轴等物理力学试验研究,揭示了黏土化蚀变岩的灾变力学特性及其在白格滑坡形成演化中的作用。主要结论如下:1)白格滑坡黏土化蚀变岩是金沙江构造结合带中蛇绿岩蚀变的产物,蚀变程度高,蚀变系数介于0.64~0.86之间,黏土矿物成分以伊利石为主、伊/蒙混层矿物次之,遇水极易崩解,崩解指数达50%以上;2)黏土化蚀变岩中工程性质最差的是蚀变黏土,水和振动荷载作用下剪切强度弱化显著,含水率由10%增至20%后剪切强度降幅达34%,动强度远小于其静强度,并随着振动次数的增加不断降低,蚀变黏土是促进斜坡岩体结构面贯通、破坏的重要因素;3)白格滑坡滑动面的形成受节理结构面与黏土化蚀变岩联合控制,整体上可分为2种模式:黏土化蚀变岩厚层软弱夹层型和充填节理裂隙贯通型;4)金沙江上游发育的不少巨型高位滑坡与黏土化蚀变岩不良工程特性具有密切的关系,岩体结构与特殊岩性的组合是值得关注的区域性易滑地质结构。以上结论对于青藏高原东缘大江大河岸坡稳定性分析和防灾减灾具有较好的启示意义。

超细复合矿物掺合料的制备及其在水泥工业中的应用

水泥行业正致力于推动低碳化和超低排放,通过研发新型低碳材料、利用工业固废资源,降低熟料消耗量和污染物排放,以实现绿色可持续发展。采用粉煤灰、水渣矿粉、脱硫石膏及外加剂等组分材料经科学配比、良好的质量控制制备而成的超细复合矿物掺合料,通过部分取代熟料生产低碳水泥,分析超细复合矿物掺合料取代率对水泥性能的影响。结果表明:在三家水泥企业生产的P·O42.5水泥中,掺入20%超细复合矿物掺合料取代水泥熟料,28d抗压强度分别提升4.7%、3.0%和3.6%,28d抗折强度分别提升6.67%、6.0%和7.1%。超细复合矿物掺合料具有取代水泥熟料的良好可行性。

仿木水泥基材料的发展研究综述

根据木材特性,结合现有水泥基材料着色、轻质化、强韧化和功能化四方面技术,可以制备出成本低、性能优、安全性高、轻质高比强的仿木水泥基复合材料,实现多维度性能的“仿木”。此外,对仿木水泥基材料的密度、强度、导热系数、颜料选择等指标提出了建议,并对未来的研究方向进行了展望。

自我控制力量模型视角下医学生心理健康的提升

医学生的心理健康关系着国家医疗卫生事业的发展和未来,意义重大,而自我控制是影响个体心理健康的重要因素之一。本文从自我控制的力量模型视角,分析导致医学生自我损耗的原因以及自我损耗对医学生心理健康的影响,并从自我控制的力量模型视角,提出了维护医学生心理健康的对策,希望为提高医学生的自我控制能力和心理健康水平提供参考。

基于相对等效短路比的新能源——柔直送出系统振荡风险评估

新能源基地并网系统面临与电压支撑强度密切相关的振荡稳定性问题,在海量运行方式下,逐一建立精细化模型的稳定性分析过程耗时较长。短路比指标可直观反映新能源并网系统的电压支撑强度和稳定裕度,但现有短路比无法适用于无同步机电源的系统。为此,将短路比概念合理扩展至全电力电子化系统,基于戴维南等效网络来度量新能源-柔直送出系统电压支撑强度,进而提出了能快速评估新能源-柔直送出系统振荡风险的相对等效短路比计算方法,并阐明相对等效短路比能够全面考虑新能源场站发电功率、交流网架结构以及新能源设备变流控制系统等多重因素对振荡稳定性的影响,最后通过算例验证了相对等效短路比评估方法的有效性。

巷道蝶形破坏强度准则低敏感性研究及工程应用

巷道围岩的塑性区形态对巷道的破坏形式及破坏程度有重要影响。为探究三向应力场下塑性区形态演化过程,基于弹性力学推导了轴向应力表达式,并依据蝶形塑性区边界方程求解思路,确定了三维强度准则下三向塑性区近似解的求解方法。通过等球应力p、等偏应力q以及不同Lode角θσ来确定围岩应力加载方案,对不同三维强度准则下的围岩塑性区形态演化规律进行深入研究,论证了蝶形破坏的准则低敏感性。基于蝶形破坏理论对羊场湾160206回风巷道的非对称变形破坏机制及控制技术进行深入分析。研究结果表明:(1)在相同p、q及不同θσ的应力加载条件下,5种强度准则下的塑性区形态均呈现圆形、类椭圆及蝶形的演化规律,且每种强度准则在相同θσ的情况下围岩的塑性区形态基本一致。(2)相同应力大小、不同应力方向的加载方案下,围岩的塑性区形态大不相同。圆巷围岩的塑性区形态很大程度上由水平侧压比决定,轴向侧压对围岩的塑性区尺寸影响较大,对塑性区形态影响较小。(3)羊场湾160206回风巷道在叠加采动影响下顶板呈现非对称大变形破坏,基于蝶形塑性区支护思路,应用非对称锚杆索+超前单元支架+钻孔卸压的协同支护技术,取得了良好的支护效果。

大型飞机结构强度试验姿态转换与控制

针对以往大型飞机姿态转换过程存在潜在的胶布带脱落、局部失稳以及多种提升设备不协调等风险问题,提出一种大型飞机结构强度试验姿态转换与控制方法。通过设计位移提升装置和全浮动支持平台,确保飞机姿态转换系统安全可靠;应用协调加载控制系统,提出多点协调的位移提升控制方案,实现飞机姿态平稳转换和精准控制;研究飞机姿态实时测量算法,开发可视化监控系统,实现飞机姿态多维变量实时监控。通过全要素测试,验证了所提方法的合理性。试验结果表明:某大型飞机的姿态转换过程实现了多维度可视化监控,与传统方法相比,效率提升了约35%,可靠性及安全性大幅提升。

金属材料高温拉伸试验控制模式及试验速率的选择

对GB/T 228.2—2015金属材料高温拉伸试验标准中的方法A和方法B从控制模式、试验速率要求两方面进行了分析解读,选用不同方法和速率从应力-应变曲线、应变速率-时间曲线、屈服强度三方面分析,并对分析设定不同试验速率进行验证。结果表明,采用引伸计反馈控制实施方法A1,实际应变速率波动超差,应力-应变曲线易发生畸变,对Rp0.2的测试结果造成误判;采用横梁位移反馈控制实施方法A2和方法B,选择合适的试验速率,测定参数的应变速率能够满足标准要求,可以获得稳定可靠的应力-应变曲线和较为一致的试验结果。

高强度螺栓施拧工具控制系统设计

为了使高强度螺栓施拧工具能够满足施工现场对扭矩控制精度以及对工具多样化的需求,设计了基于STM32的高强度螺栓施拧工具控制系统。控制系统采用一体化设计。硬件具有应变片接口和霍尔传感器接口。软件对应开发扭矩控制和转角控制双重可配置模式,以控制螺栓精准施拧。控制器配备数据上传功能,方便数据化管理、追溯工具和螺栓信息。此外,开发标定功能、故障检测功能、人机交互等功能,以进一步满足施工需求、降低施工难度。该控制系统体积紧凑、控制精度高、响应速度快、功能丰富。在标准扭矩仪测试过程中,施拧工具能够保证±4%以内的控制精度。该设计为市场同类铁路桥梁建设工具的设计提供了参考。

1180 MPa级超高强钢冷连轧过程的厚度综合控制技术

针对超高强钢在冷轧过程中厚度波动大以及带头带尾厚度超差的问题,首先根据金属秒流量模型建立了厚度超差预测模型与辊缝调节量预估模型;随后开发了轧制过程中的厚度控制系统,并进行了辊缝调节量优化;最后建立了带钢头尾轧制过程中的轧制速度与张力优化模型。以国内某冷连轧机组的第1机架为技术应用对象,选择两种典型的超高强钢进行生产测试,测试结果表明:超高强钢AR4146E1与DU6220A1的厚度超差长度分别从70.3 m、36.89 m下降到了16.85 m、16.33 m。