Irregular initial solidification by mold thermal monitoring in the continuous casting of steels:A review

Occasional irregular initial solidification phenomena,including stickers,deep oscillation marks,depressions,and surface cracks of strand shells in continuous casting molds,are important limitations for developing the high-efficiency continuous casting of steels.The application of mold thermal monitoring(MTM) systems,which use thermocouples to detect and respond to temperature variations in molds,has become an effective method to address irregular initial solidification phenomena.Such systems are widely applied in numerous steel companies for sticker breakout prediction.However,monitoring the surface defects of strands remains immature.Hence,indepth research is necessary to utilize the potential advantages and comprehensive monitoring of MTM systems.This paper summarizes what is included in the irregular initial solidification phenomena and systematically reviews the current state of research on these phenomena by the MTM systems.Furthermore,the influences of mold slag behavior on monitoring these phenomena are analyzed.Finally,the remaining problems of the formation mechanisms and investigations of irregular initial solidification phenomena are discussed,and future research directions are proposed.

Dynamic Constraint-Driven Event-Triggered Control of Strict-Feedback Systems Without Max/Min Values on Irregular Constraints

This work proposes an event-triggered adaptive control approach for a class of uncertain nonlinear systems under irregular constraints.Unlike the constraints considered in most existing papers,here the external irregular constraints are considered and a constraints switching mechanism(CSM)is introduced to circumvent the difficulties arising from irregular output constraints.Based on the CSM,a new class of generalized barrier functions are constructed,which allows the control results to be independent of the maximum and minimum values(MMVs)of constraints and thus extends the existing results.Finally,we proposed a novel dynamic constraint-driven event-triggered strategy(DCDETS),under which the stress on signal transmission is reduced greatly and no constraints are violated by making a dynamic trade-off among system state,external constraints,and inter-execution intervals.It is proved that the system output is driven to close to the reference trajectory and the semi-global stability is guaranteed under the proposed control scheme,regardless of the external irregular output constraints.Simulation also verifies the effectiveness and benefits of the proposed method.

Performance and Complexity Trade-Off between Short-Length Regular and Irregular LDPC

In this paper, both the high-complexity near-ML list decoding and the low-complexity belief propagation decoding are tested for some well-known regular and irregular LDPC codes. The complexity and performance trade-off is shown clearly and demonstrated with the paradigm of hybrid decoding. For regular LDPC code, the SNR-threshold performance and error-floor performance could be improved to the optimal level of ML decoding if the decoding complexity is progressively increased, usually corresponding to the near-ML decoding with progressively increased size of list. For irregular LDPC code, the SNR-threshold performance and error-floor performance could only be improved to a bottle-neck even with unlimited decoding complexity. However, with the technique of CRC-aided hybrid decoding, the ML performance could be greatly improved and approached with reasonable complexity thanks to the improved code-weight distribution from the concatenation of CRC and irregular LDPC code. Finally, CRC-aided 5GNR-LDPC code is evaluated and the capacity-approaching capability is shown.

Strength and deformation characteristics of irregular columnar jointed rock mass: A combined experimental and theoretical study

The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of CJRM is important for engineering construction.The Voronoi diagram and three-dimensional printing technology were used to make an irregular columnar jointed mold,and the irregular CJRM(ICJRM)specimens with different dip directions and dip angles were prepared.Uniaxial compression tests were performed,and the anisotropic strength and deformation characteristics of ICJRM were described.The failure modes and mechanisms were revealed in accordance with the final appearances of the ICJRM specimens.Based on the model test results,the empirical correlations for determining the field deformation and strength parameters of CJRM were derived using the dip angle and modified joint factor.The proposed empirical equations were used in the Baihetan Project,and the calculated mechanical parameters were compared with the field test results and those obtained from the tunneling quality index method.Results showed that the deformation parameters determined by the two proposed methods are all consistent with the field test results,and these two methods can also estimate the strength parameters effectively.

Generation of irregular particle packing with prescribed statistical distribution, spatial arrangement, and volume fraction

A method for packing irregular particles with a prescribed volume fraction is proposed.Furthermore,the generated granular material adheres to the prescribed statistical distribution and satisfies the desired complex spatial arrangement.First,the irregular geometries of the realistic particles were obtained from the original particle images.Second,the Minkowski sum was used to check the overlap between irregular particles and place an irregular particle in contact with other particles.Third,the optimised advance front method(OAFM)generated irregular particle packing with the prescribed statistical dis-tribution and volume fraction based on the Minkowski sum.Moreover,the signed distance function was introduced to pack the particles in accordance with the desired spatial arrangement.Finally,seven biaxial tests were performed using the UDEC software,which demonstrated the accuracy and potential usefulness of the proposed method.It can model granular material efficiently and reflect the meso-structural characteristics of complex granular materials.This method has a wide range of applications where discrete modelling of granular media is necessary.

On the problem of the dynamical reactions of a rolling wheelset to real track irregularities

We investigate numerically the dynamical reactions of a moving wheelset model to real measured track irregularities.The background is to examine whether the dynamics are suitable as the input to the inverse problem:determine the true track geometry from measured wheelset dynamical reactions.It is known that the method works well for the vertical position of the rails but the computed lateral position is often flawed.We find that the lateral motion of the wheelset often may differ from the track geometry.The cases are investigated closely but the reasons remain unknown.While the wheelset dynamics reflect the larger(>4-6 mm)aperiodic track disturbances and single large disturbances quite well,this does not seem to be the case for general smaller or periodic track irregularities or sections behind single large disturbances.The resulting dynamics of a wheelset to lateral track irregularities are in general not sufficiently accurate to be used as the basis for a description of the track irregularities.

Influence of Vertical Irregularity on the Seismic Behavior of Base Isolated RC Structures with Lead Rubber Bearings under Pulse-Like Earthquakes

Nowadays,an extensive number of studies related to the performance of base isolation systems implemented in regular reinforced concrete structures subjected to various types of earthquakes can be found in the literature.On the other hand,investigations regarding the irregular base-isolated reinforced concrete structures’performance when subjected to pulse-like earthquakes are very scarce.The severity of pulse-like earthquakes emerges from their ability to destabilize the base-isolated structure by remarkably increasing the displacement demands.Thus,this study is intended to investigate the effects of pulse-like earthquake characteristics on the behavior of low-rise irregular base-isolated reinforced concrete structures.Within the study scope,investigations related to the impact of the pulse-like earthquake characteristics,irregularity type,and isolator properties will be conducted.To do so,different values of damping ratios of the base isolation system were selected to investigate the efficiency of the lead rubber-bearing isolator.In general,the outcomes of the study have shown the significance of vertical irregularity on the performance of base-isolated structures and the considerable effect of pulse-like ground motions on the buildings’behavior.

Refined disturbance observer based prescribed performance fixed-time control of high-speed EMS trains with track irregularities

High-speed Electromagnetic Suspension(EMS)train is continuously impacted by the irregularity of the track,which worsens the levitation performance of the train.In this paper,a composite control scheme for the EMS is proposed to suppress track irregularities by integrating a Refined Disturbance Observer(RDO)and a Prescribed Performance Fixed-Time Controller(PPFTC).The RDO is designed to estimate precisely the track irregularities and lumped disturbances with uncertainties and exogenous disturbances in the suspension system,and reduce input chattering by applying to the disturbance compensation channel.PPFTC is designed to converge the suspension air gap error to equilibrium point with prescribed performance by completing error conversion,and solve the fast dynamic issue of EMS.And the boundary of overshoot and steady-state is limited in the ranged prescribed.A theoretical analysis is conducted on the stability of the proposed control method.Finally,the effectiveness and reasonability of the proposed composite anti-disturbance control scheme is verified by simulation results.

孕产妇不规则抗体血清学特征和临床意义分析

目的:明确不规则抗体在孕产妇人群中的血清学特征,探讨其临床意义。方法:选取2017年1月-2022年3月于重庆医科大学附属妇女儿童医院就诊的孕产妇151471例,采用微柱凝胶抗人球蛋白法进行不规则抗体筛查,对部分抗体筛查阳性标本进一步做抗体特异性鉴定。结果:孕产妇不规则抗体筛查阳性率为0.91%(1375/151471),其中0.23%(355/151471)在孕早期检出,0.05%(71/151471)在孕中期检出,0.63%(949/151471)在孕晚期检出,孕晚期抗体阳性率明显高于孕早期和孕中期,且孕晚期新增阳性例数明显高于孕中期新增例数;分析1375例不规则抗体阳性结果的凝集强度,其中凝集强度为弱阳性占比最高,为50.11%(689/1375),可疑阳性占18.69%(257/1375),阳性占31.20%(429/1375),孕中期凝集强度分布与孕早期相比差异无统计学意义,但孕晚期可疑阳性和弱阳性的比例低于孕早期,阳性比例高于孕早期,比较差异有统计学意义(P<0.001)。不规则抗体阳性孕产妇中,妊娠≥2次孕产妇的占比明显高于≤1次者;进行抗体鉴定的60例孕产妇中,Rh系统占25.00%(15/60),Lewis系统占43.33%(26/60),Kidd系统占3.33%(2/60),MNS系统抗体占16.67%(10/60),P1PK系统抗体占1.67%(1/60),自身抗体占1.67%(1/60),4例无法确认特异性占6.67%(4/60);特异性抗体中以抗-Lea(30.00%)最为常见,其次是抗-E(16.67%)和抗-M(16.67%)。结论:不同地区、具有不同遗传背景的孕产妇人群的不规则抗体血清学特征存在差异,掌握本地区孕产妇不规则抗体的特征,对保证孕产妇输血安全、防治新生儿溶血病具有十分重要的意义。

Use of Irregular Wood Components to Design Non-Standard Structures

This project deals with architecture and engineering involved in the process of architectural design.Based on native irregular components,it aims at developing an innovative approach in the conception and rationalization of non-standard structures.Contemporary architecture and its non-classical structures require the design of customized pieces.This process which is highly energy and resources consumptive does not always take into account the inherent material properties.This project develops a way of optimizing,in architectural structures,the use of native wood pieces that are not industrially transformed(e.g.boughs)or of reused pieces of carpentry.As a consequence,the ecological footprint of the structures would be reduced.

高速铁路0.01~1 m波段高低轨道不平顺特性分析

随着我国高速铁路发展规模的不断扩大及运营速度的不断提升,轨道短波不平顺引起的振动与噪声问题日益严重。深入研究高速铁路短波不平顺的时域、频域与时频域特征,对精准掌握高速铁路轨道短波平顺状态及其引起的车-轨系统振动、伤损等一系列问题具有重要的参考价值。以某高速铁路实测0.01~1 m波段轨面高低不平顺数据为研究对象,经过数据预处理剔除异常值并消除趋势项后,对实测不平顺数据进行时域分析,得到该高铁线路短波不平顺数据的统计与分布特性。采用平均周期图法计算该高铁线路轨道短波不平顺功率谱密度,应用非线性最小二乘拟合优化算法进行拟合,提出高速铁路轨道短波不平顺谱。从时频域角度对该段数据进行经验模态分解与希尔伯特变换,分析该高铁线路短波不平顺的希尔伯特谱与边际谱。研究结果表明:该高铁线路轨道短波不平顺数据各统计量幅值都较小,且近似服从正态分布;该高铁线路轨道短波不平顺功率谱密度存在与钢轨波磨有关的多个周期性成分,提出的高速铁路短波不平顺谱函数能够很好地对实测功率谱密度进行拟合,且拟合效果优于经典的SATO建议的短波谱与50 kg/m钢轨的短波谱;对该高铁线路轨道可能存在的短波病害进行识别与定位,时频域分析的方法可以较好地应用于高速铁路轨道平顺性的分析与日常的管理维护。

城市轨道交通轨面短波不平顺谱实测研究

针对城市轨道交通诱发的振动噪声问题,对轨面短波不平顺进行研究.首先,对上海市轨道交通线路轨面短波不平顺实测数据进行零均值化、剔除异常值、消除趋势项等预处理.其次,利用改进的协方差法计算得到轨面短波不平顺功率谱,分析轨道类型、曲线半径及钢轨接头对轨面短波不平顺功率谱分布规律的影响.然后,基于非线性最小二乘法对轨面短波不平顺谱进行拟合.最后,提出我国城市轨道交通轨面短波不平顺统计谱表达式.研究结果表明:直线段接头区轨面短波不平顺功率谱密度曲线在整个分析波长范围内具有较多特征峰值;直线段接头区上、下行短波不平顺功率谱密度值随波长的分布特征和数值相差不大,说明上、下行的轨面不平顺状态基本相同;钢轨的磨耗程度与曲线半径呈负相关,内、外轨面不平顺功率谱密度的差异随曲线半径的增大而减小,曲线半径是影响轨面不平顺状态的主要因素之一;线路类型对轨面短波不平顺功率谱的影响不大,不同曲线半径、焊接接头影响明显,在对轨道进行维护和养护时需关注小曲线半径区段以及焊接接头区段的不平顺状态.

多源车载数据驱动的地铁轨道不平顺智能识别方法

针对轨道不平顺检测成本高与时效性低等不足,从车辆动态响应与轨道不平顺之间的相关性为切入点,提出一种多源车载数据驱动的轨道不平顺智能识别方法。首先,建立地铁车辆系统动力学模型,获取车辆振动与运动姿态响应数据;其次,通过相关性分析算法,选取强相关性数据,制作网络模型数据集;最后,建立卷积神经网络-长短期记忆网络(CNN-LSTM),通过粒子群算法优化(PSO)神经网络模型参数,建立PSO-CNN-LSTM模型,实现对轨道不平顺的识别拟合。研究结果表明:在车辆动态响应信号中,与横向信号与轨道不平顺之间的相关性相比,垂向信号的更强,同时,车体的运动姿态如车体点头角速度与不平顺有明显的相关性。所提出的PSO-CNN-LSTM模型轨道垂向与横向不平顺识别拟合度分别达0.92和0.76。与经典的全连接神经网络FCNN和支持向量机SVR相比,PSO-CNN-LSTM有更好的识别效果与时效性。

下陡上缓混合式海堤上不规则波爬高研究

波浪爬高是影响海堤堤顶高程的一个重要因素,直接影响工程投资。下部为陡墙、上部为斜坡、中间带平台的海堤为我国沿海常见的一种海堤断面型式,为研究此种海堤断面型式上不规则波爬高规律,通过物理模型试验观测得到不同试验条件下波浪爬高,并根据海堤下部陡墙坡度、上部斜坡坡度、平台宽度与平台高度、波浪要素对波浪爬高的影响分析,拟合了不规则波爬高计算公式。结果表明,陡墙坡度为0的海堤的波浪爬高值比0.5小;当波陡在0.03~0.05之间时,随着海堤上部坡度变缓,大部分波浪爬高逐渐减小;波浪爬高随着平台宽度的增加而减小;波浪爬高随着海堤平台位置的降低而增大;波浪爬高随着波陡的增加呈现先增大后减小的趋势;拟合公式可反映下部为陡墙、中间为平台、上部为斜坡的混合式海堤断面上波浪爬高规律。

45°倾斜应用的多通道干涉截止滤光片研制

光纤通信的发展对通信器件中薄膜滤光片提出了新的要求。根据45°倾斜应用的多通道干涉截止滤光片的设计指标,选择Nb2O5和SiO2为高、低折射率材料设计非规整膜系,以减少偏振效应的影响。结合APS1104型镀膜机的特点,分析了设计膜系的膜层灵敏度和薄膜生长过程中的模拟监控曲线,判断设计薄膜的可镀制性。然后采取直接光学监控方式,选择合适的镀制工艺成功镀制滤光片。测试结果表明:滤光片在45°倾斜应用条件下,1255~1365 nm、1475~1502 nm双通带最大插入损耗为0.199 dB,1547~1565 nm为反射带,通带隔离度为17.3 dB,满足系统应用需求。

异形平面组合空腹夹层板楼盖舒适度实测研究

利用环境激励,采用时域法模态拟合方法对异形平面组合空腹夹层板楼盖结构进行了现场竖向振动模态测试,得到组合楼盖结构前4阶竖向振型、自振频率、阻尼比等参数,并与有限元软件计算出的振型对比分析;对异形平面组合空腹夹层版楼盖进行6种工况作用下的人致振动加速度时程测试,分别得到各工况下不同测点的加速度时程曲线及相应各测点的加速度峰值。结果表明,现场实测和有限元分析得到的组合空腹夹层板楼盖自振频率均远大于3Hz,且两者误差在5%之内;楼盖阻尼比均小于005;最不利工况下异形组合空腹夹层板楼盖竖向最大加速度峰值为0036m/s2,其自振频率和加速度峰值均满足《高层建筑混凝土结构技术规程》(JGJ 3—2010)和《组合楼板设计与施工规范》(CECS 273—2010)要求,楼盖应用在大跨度异形平面中具有较好的舒适度。

住院拟输血患者不规则抗体的鉴定与分析

目的:分析71847例拟输血患者不规则抗体的类型和分布特点,探究其对临床安全输血的作用。方法:选取本院2020年1月到2023年10月期间71847例拟输血患者的血液标本,采用微柱凝胶检测卡进行不规则抗体筛查及抗体鉴定。结果:71847例拟输血患者中,共筛选出不规则抗体阳性301例(0.42%),包括同种抗体252例(83.72%);其中Rh系统最高,为179例(59.47%)。Rh系统抗体包括抗E 135例(44.85%)、抗E+c 24例(7.97%)、抗C+e 10例(3.32%)、抗c 6例(1.99%)、抗D 3例(1.00%)和抗D+C 1例(0.33%)。通过对301例不规则抗体进行分析发现,>60岁组的阳性率高于≤60岁组(0.61%vs 0.33%),女性组的阳性率高于男性组(0.50%vs 0.31%),内科组(1.25%)和妇产科组(0.32%)的阳性率均高于外科(0.20%),妊娠/输血史组的阳性率高于无妊娠/输血史组(0.64%vs 0.13%),差异均具有统计学意义(P<0.05)。结论:有必要将RhE纳入血型常规监测,并在输血时尽可能地进行E抗原匹配,这可以很大程度地降低不规则抗体的阳性率,从而达到更安全的输血治疗。

高速铁路主跨320 m钢-混部分斜拉桥无砟轨道适应性研究

南玉高铁六景郁江特大桥设计将钢-混部分斜拉桥结构引入时速350 km高速铁路领域,而300 m级以上大跨度桥上无砟轨道的竖向变形极易超限,影响列车通过的安全性和舒适性,因此,系统研究在此大跨桥梁结构上铺设无砟轨道的适应性十分必要。通过建立有限元及动力学模型,分析不同组合工况下无砟轨道结构的变形特点及动力特性,运用60 m弦测法探究各工况下无砟轨道的线形变化规律,从而确定大跨度钢-混部分斜拉桥铺设无砟轨道的适应性,并对设计和施工提出合理化建议。主要结论如下:在各种不利组合荷载作用下,桥上无砟轨道结构强度满足规范要求,列车通过大桥的各项安全性与舒适性指标均满足规范要求;混凝土收缩徐变和斜拉索升降温是影响无砟轨道线形标准的两大主因,应在无砟轨道施工前确保足够的沉降观测期和收缩徐变释放期,并充分考虑拉索的保温设计;在温度组合荷载作用下,桥上无砟轨道的60 m弦测不平顺幅值为6.79 mm,满足高速铁路静态验收标准;但在叠加列车荷载和收缩徐变后,变形弦测值均出现Ⅱ级及以上超限,通过合理设置预拱度后可有效改善轨道平顺性标准。

基于特征聚类的轨道不平顺潜在病害辨识

研究目的:轨道不平顺潜在病害隐蔽性强,对其准确合理辨识是开展预防修策略下线路养护维修作业的前提。本文以轨检数据为基础,分别构造了以轨道质量指数(TQI)和轨道不平顺幅值为对象的潜在病害辨识指标。在此基础上,基于k-means++聚类算法和手肘法通过判定样本最佳聚类簇数实现潜在病害的识别及定位。依托某有砟铁路动检数据对所提轨道不平顺潜在病害辨识方法进行了验证。研究结论:(1)对于均值管理来说,在16 km连续轨道区段上2处区段单元潜在病害被准确识别,其历史最大TQI值分别约为5.5 mm、5.3 mm,且潜在病害定位结果与实际里程基本吻合;(2)对于峰值管理来说,在500 m连续轨道区段上2处局部不平顺潜在病害也被准确识别,其历史最大幅值约为3 mm、3.3 mm,潜在病害定位结果与实际里程基本吻合;(3)本研究成果可与大机捣固作业、人工精调作业相结合,为预防修策略下的潜在病害整治提供辅助参考。

空间异形拱桥振动台试验设计

振动台试验是研究大型结构复杂动力特性和地震响应的有效手段,由于振动台尺寸和载重的限制,合理设计缩尺模型结构是振动台试验成功的关键。基于量纲相似法及弹性相似律,取1∶20的几何相似比,以某空间异形拱桥为原型,开展了其关键参数动力缩尺模型设计。首先,通过有限元数值分析,分析了动力作用下原桥模型与缩尺桥模型的动力特性、关键部位内力与位移等响应,以验证缩尺模型的合理性;并在选取合理地震动作用下,开展了结构时程响应分析。研究结果表明:缩尺模型桥与原型桥前10阶模态完全吻合且频率误差小于7%,关键截面内力、位移和加速度等响应误差未超过10%,缩尺模型桥可较好地反映原桥动力特性和响应特点。研究成果可为空间异形拱桥振动台抗震设计提供技术支撑并为同类桥梁振动台试验提供参考。