Seismic elastic-plastic time history analysis and reliability study of quayside container crane

Quayside container crane is a kind of huge dimension steel structure,which is the major equipment used for handling container at modern ports.With the aim to validate the safety and reliability of the crane under seismic loads,besides conventional analysis,elastic-plastic time history analysis under rare seismic intensity is carried out.An ideal finite element（FEM） elastic-plastic mechanical model of the quayside container crane is presented by using ANSYS codes.Furthermore,according to elastic-plastic time history analysis theory,deformation,stress and damage pattern of the structure under rare seismic intensity are investigated.Based on the above analysis,the established reliability model according to the reliability theory,together with seismic reliability analysis based on Monte-Carlo simulation is applied to practical analysis.The results show that the overall structure of the quayside container crane is generally unstable under rare seismic intensity,and the structure needs to be reinforced.

The Optimum Sowing Time for Plastic-film Corn and the Application of Two Related Theories

There are two main theories, the 'temperature-raising' theory and the 'precipitation-based regulation' theory, which guide the optimum sowing time of the plastic-film corn. The former was applied in the humid or semi-humid ecotope and on irrigated or half-shaded land in the arid and semi-arid ecotopes, while the latter was suitable for the dry-farming land in the semi-arid ecotope. The results of experiments and investigations for many years showed that the corn output was increased by 69.2% when the former theory was applied to guide the optimum sowing time for plastic-film corn in the semi-humid ecotope, and by 60. 0% when the latter theory was applied in the semi-arid ecotope. In the semi-arid ecotope, however, the output was increased only by 15.7% when the former theory was applied, and even dropped by 14.4% when the latter theory was applied.

Early constraint-induced movement therapy affects behavior and neuronal plasticity in ischemia-injured rat brains

Constraint-induced movement therapy is an effective rehabilitative training technique used to improve the restoration of impaired upper extremity movement after stroke. However, whether constraint-induced movement therapy is more effective than conventional rehabilitation in acute or sub-acute stroke remains controversial. The aim of the present study was to identify the optimal time to start constraint-induced movement therapy after ischemic stroke and to explore the mechanisms by which constraint-induced movement therapy leads to post-stroke recovery. Sixty-four adult male Sprague-Dawley rats were randomly divided into four groups: sham-surgery group, cerebral ischemia/reperfusion group, early constraint-induced movement therapy group, and late constraint-induced movement therapy group. Rat models of left middle cerebral artery occlusion were established according to the Zea Longa line embolism method. Constraint-induced movement therapy was conducted starting on day 1 or day 14 in the early constraint-induced movement therapy and late constraint-induced movement therapy groups, respectively. To explore the effect of each intervention time on neuromotor function, behavioral function was assessed using a balance beam walking test before surgery and at 8 and 21 days after surgery. The expression levels of brain-derived neurotrophic factor, nerve growth factor and Nogo receptor were evaluated using real time-polymerase chain reaction and western blot assay to assess the effect of each intervention time. The results showed that the behavioral score was significantly lower in the early constraint-induced movement therapy group than in the cerebral ischemia/reperfusion and late constraint-induced movement therapy groups at 8 days. At 21 days, the scores had significantly decreased in the early constraint-induced movement therapy and late constraint-induced movement therapy groups. At 8 days, only mild pyknosis appeared in neurons of the ischemic penumbra in the early constraint-induced movement therapy group, which was distinctly better than in the cerebral ischemia/reperfusion group. At 21 days, only a few vacuolated cells were observed and no obvious inflammatory cells were visible in late constraint-induced movement therapy group, which was much better than at 8 days. The mRNA and protein expression levels of brain-derived neurotrophic factor and nerve growth factor were significantly higher, but expression levels of Nogo receptor were significantly lower in the early constraint-induced movement therapy group compared with the cerebral ischemia/reperfusion and late constraint-induced movement therapy groups at 8 days. The changes in expression levels at 21 days were larger but similar in both the early constraint-induced movement therapy and late constraint-induced movement therapy groups. Besides, the protein nerve growth factor level was higher in the late constraint-induced movement therapy group than in the early constraint-induced movement therapy group at 21 days. These results suggest that both early(1 day) and late(14 days) constraint-induced movement therapy induces molecular plasticity and facilitates functional recovery after ischemic stroke, as illustrated by the histology. The mechanism may be associated with downregulation of Nogo receptor expression and upregulation of brain-derived neurotrophic factor and nerve growth factor expression.

Plasticity-induced characteristic changes of pattern dynamics and the related phase transitions in small-world neuronal networks

Phase transitions widely exist in nature and occur when some control parameters are changed. In neural systems, their macroscopic states are represented by the activity states of neuron populations, and phase transitions between different activity states are closely related to corresponding functions in the brain. In particular, phase transitions to some rhythmic synchronous firing states play significant roles on diverse brain functions and disfunctions, such as encoding rhythmical external stimuli, epileptic seizure, etc. However, in previous studies, phase transitions in neuronal networks are almost driven by network parameters （e.g., external stimuli）, and there has been no investigation about the transitions between typical activity states of neuronal networks in a self-organized way by applying plastic connection weights. In this paper, we discuss phase transitions in electrically coupled and lattice-based small-world neuronal networks （LBSW networks） under spike-timing-dependent plasticity （STDP）. By applying STDP on all electrical synapses, various known and novel phase transitions could emerge in LBSW networks, particularly, the phenomenon of self-organized phase transitions （SOPTs）： repeated transitions between synchronous and asynchronous firing states. We further explore the mechanics generating SOPTs on the basis of synaptic weight dynamics.

Self-sustained firing activities of the cortical network with plastic rules in weak AC electrical fields

Both external and endogenous electrical fields widely exist in the environment of cortical neurons. The effects of a weak alternating current （AC） field on a neural network model with synaptic plasticity are studied. It is found that self-sustained rhythmic firing patterns, which are closely correlated with the cognitive functions, are significantly modified due to the self-organizing of the network in the weak AC field. The activities of the neural networks are affected by the synaptic connection strength, the exterrtal stimuli, and so on. In the presence of learning rules, the synaptic connections can be modulated by the external stimuli, which will further enhance the sensitivity of the network to the external signal. The properties of the external AC stimuli can serve as control parameters in modulating the evolution of the neural network.

Evaluation of the Equality of Non-Polar Capillary Columns in GC/MS Analysis of Food Contact Plastics

Non-polar capillary columns for GC/MS are widely utilized in the analysis of additives for food contact materials. Though various kinds of non-polar capillary columns are commercially available, the equality of their performance has not been verified. Herein, ninety-six additives for food contact plastics were analyzed using fifteen kinds of columns, and the peak separation, retention times, and peak areas of each additive were compared. The additives, with various chemical properties, comprised forty four plasticizers, twenty lubricants, twenty antioxidants, nine ultraviolet absorbers, and three other compounds. 10 μg.mL-1 test solutions were prepared in acetone, and injected to the GC/MS. The fifteen columns were classified into five categories based on the chromatogram pattern and peak separation. To facilitate comparison of the retention time and detection sensitivity of the columns for the additives, the relative retention time (RRT) and relative peak area (RPA) were calculated by using dibutylphthalate or 4-tert-butylphenylsalicylate as an internal standard. The RRTs of the additives on each column were essentially similar. However, the RRT of the additives which were detected in the later stages differed slightly. Although the RPA of the plasticizers and lubricants were roughly similar, column-to-column differences were observed for certain additives, such as antioxidants and ultraviolet absorbers. Furthermore, certain fatty acids, antioxidants, two plasticizers, and two benzophenone type ultraviolet absorbers were not detected in the chromatograms of two columns.

Structure, Plastic Deformation of Polyethylene: A Molecular Dynamics Method

This paper studies the influence factors of atoms number (N) at temperature (T) and after annealing time (t) on the structure shape and the plastic deformation of Polyethylene C2H4 (PE) by the Molecular Dynamics (MD) method with Dreading pair interaction, cyclic boundary conditions and plastic deformation of Polyethylene (PE) be done by stretching method according to the z-axis. The results of structure, plastic deformation of PE are analyzed through size (l), the total energy of the system (Etot), shape and associated energy (Ebond), angular binding energy (Eangle), energy Edihedral, interactive energy Vander Walls (Enon-bonding). When increasing N, t leads to the number of structural units of Face-Centred Cubic (FCC), Body-Centered Cubic (BCC) and Hexagonal Close-Packed (HCP) increasing, but Amorphous (Amor) decreases while the angle between the atoms is a constant corresponding to 109.5°. Besides, the length of the link (r) increases from r = 1.529 Å to r = 1.558 Å while the plastic deformation energy of PE gets an enormous change and the bonding angle at 109.27°. The length of the link r = 1.529 Å and the size (l) of the PE material increase from l = 3.73 nm to l = 6.63 nm while the total energy of system (Etotal) decreases from Etotal = −1586 eV to Etotal = −7891 eV with the transition temperature is T = 103 K. Increasing the number of atoms leads to increasing the length of the link. The total energy Etotal of the system decreases, but the number of structural units in FCC, HCP, BCC and Amor increase, which leads to the length of the link increases, the Etotal decreases, and there is a change in the plastic deformation characteristics of PE. In contrast, increasing T leads to the plastic deformation increases, and PE moves from the amorphous state to the liquid state. The obtained results are very significant for future experimental research.

Fast pulse sampling module for real-time neutron–gamma discrimination

An adaptable and compact fast pulse sampling module was developed for the neutron–gamma discrimination. The developed module is well suited for low-cost and low-power consumption applications. It is based on the Domino Ring Sampler 4(DRS4) chip, which offers fast sampling speeds up to 5.12 giga samples per second(GSPS) to digitize pulses from front-end detectors. The high-resolution GSPS data is useful for obtaining precise real-time neutron–gamma discrimination results directly in this module. In this study, we have implemented real-time data analysis in a field programmable gate array. Real-time data analysis involves two aspects: digital waveform integral and digital pulse shape discrimination(PSD). It can significantly reduce the system dead time and data rate processed offline. Plastic scintillators(EJ-299-33), which have proven capable of PSD, were adopted as neutron detectors in the experiments. A photomultiplier tube(PMT)(model #XP2020) was coupled to one end of a detector to collect the output light from it. The pulse output from the anode of the PMT was directly passed onto the fast sampling module. The fast pulse sampling module was operated at 1 GSPS and 2 GSPS in these experiments, and the AmBe-241 source was used to examine the neutron–gamma discrimination quality. The PSD results with different sampling rates and energy thresholds were evaluated. The figure of merit(FOM) was used to describe the neutron–gamma discrimination quality. The best FOM value of 0.91 was obtained at 2 GSPS and 1 GSPS sampling rates with an energy threshold of 1.5 MeV_(ee)(electron equivalent).

面向建筑韧性目标的减隔震设计研究与实践

为培养土木工程类学生防灾减灾设计能力,本文以《基于保持建筑正常使用功能的抗震技术导则》(以下简称《导则》)为核心内容,提出建筑物在遭受设防地震时满足正常使用要求,并根据使用功能及损坏后果提出Ⅰ、Ⅱ类建筑性能目标。以预期抗震韧性目标为导向,提出一种面向两区八类建筑的“三水准设防、两阶段设计”策略,以实现《导则》对Ⅰ、Ⅱ类建筑进行减隔震设计时正常使用要求,提高震后建筑维持和恢复使用功能的能力。选取某医技楼和学校作为Ⅰ类和Ⅱ类建筑的典型算例,以震后修复费用、修复时间和人员伤亡指标提出预期韧性目标,并对其按照韧性设防策略进行隔震与减震设计。基于弹塑性时程分析结果采用SAUSG-RES提取工程需求参数进行韧性等级评定。结果表明,两区八类建筑采用韧性设防策略后,结构在遭受设防地震时满足正常使用要求,经过简单修复后可恢复使用功能,达到韧性一星等级;在遭受罕遇地震后经过适度修复可恢复使用功能,达到高韧性等级。韧性设防策略不仅完善了传统抗震设防的不足,而且衔接《导则》要求与工程设计习惯,为抗震设计课程高阶性改革提供了参考思路。

湖北工人文化宫超限结构设计

湖北工人文化宫的主要功能为职工培训和展览等,主体结构采用框架-剪力墙结构,存在扭转不规则、偏心布置、楼板不连续、局部跃层柱等不规则项,属于复杂超限高层建筑。采用抗震性能化设计对主要构件进行复核,采用YJK和MIDAS Building软件对结构进行多遇地震弹性计算和弹性时程分析以及罕遇地震下的动力弹塑性时程分析和楼板应力分析等。分析结果表明,整体结构可以满足规范的要求,达到预定的性能目标。并根据分析结果采取抗震加强措施。在容易产生共振的大跨度预应力楼盖区域,以高阻尼橡胶减振垫作为减振材料,对楼盖在人行激励下和有节奏运动激励下的楼板舒适度进行分析。分析结果表明,楼板舒适度满足规范要求。

以Cameron适时理论为基础的全程护理模式在烧伤后瘢痕整形患者中的应用

目的:研究以Cameron适时理论为基础的全程护理模式对烧伤后瘢痕整形患者的干预效果。方法:选择2021年9月-2022年6月笔者医院收治的60例烧伤后瘢痕整形患者为研究对象,采用随机数字表法分为对照组(30例)和观察组(30例)。对照组给予常规护理干预,观察组在对照组的基础上采用以Cameron适时理论为基础的全程护理模式进行干预,两组均干预8周。统计比较两组瘢痕恢复效果、并发症发生情况、心理状态、应对方式及护理满意度。结果:干预后,观察组创面渗出持续时间、疼痛持续时间均短于对照组(P<0.05);两组创面愈合时间、色素沉着率比较差异无统计学意义(P<0.05)。干预8周后,观察组瘢痕恢复总有效率显著高于对照组(P<0.05);观察组心理韧性评分高于对照组(P<0.05),焦虑、抑郁、心理困扰评分低于对照组(P<0.05);观察组屈服、回避评分低于对照组(P<0.05),面对评分高于对照组(P<0.05);观察组护理总满意率高于对照组(P<0.05)。干预期间,观察组总并发症发生率低于对照组(P<0.05)。结论:以Cameron适时理论为基础的全程护理模式对烧伤后瘢痕整形患者进行干预,可有效促进患者创面愈合,改善患者心理状态及应对方式,降低并发症发生率,患者满意度高,具有较好的应用价值。

上海浦东足球场整体模型分析与计算

上海浦东足球场整体结构由一层地下室结构、地上钢结构看台和大跨度钢结构屋盖三部分组成,地上看台结构采用钢框架+屈曲约束支撑体系,屋盖采用轮辐式张拉体系。屋盖和下部结构单独分析,不能体现上下结构之间的相互影响。为更可靠合理进行整体结构设计,采用了整体模型分析作为单体模型分析的重要且必要的补充。整体模型分析工作主要包括多遇地震、设防地震下的弹性分析,罕遇地震下的弹塑性时程分析,以及超长混凝土结构应力分析。结果表明:单体分析存在局限性,整体模型的足球场结构受力安全。

高烈度区框-筒结构组合减隔震抗震性能研究

随着社会经济发展,我国高层建筑数量与日俱增,减震、隔震技术逐渐在高层结构中应用,并且提出了减震、隔震装置联合使用的新型组合减隔震技术。本文为研究高层组合减隔震结构中阻尼器布置位置对隔震效果的影响,针对高烈度区某框架-核心筒结构采取传统抗震、隔震、隔震-隔震层减震和隔震-非隔震层减震4种抗震方案,并选取7条地震波,通过Perform-3D软件对其分别进行罕遇地震和极罕遇地震下的弹塑性时程分析。对比结构宏观指标发现:相比隔震结构,组合减隔震结构能有效降低地震响应;黏滞阻尼器设置在非隔震层的组合减隔震结构抗震效果最佳,提高了结构安全度。

雷电冲击下土体应力及弹塑性界面时程分析

雷电作为自然界一种极端天气的表现形式,常给地基、地面、高耸建筑等造成严重破坏。工程防雷措施依赖于土体雷电冲击特性。现阶段,研究人员大多从电气工程角度探究雷电冲击土体造成的危害,但因学科间的差异与局限,雷电作用下岩土工程与电气工程的交叉融合方面的研究十分欠缺。本文构建土体雷电冲击模型,基于电弧通道能量平衡方程计算雷电放电产生的冲击波压力,将冲击波压力作为外加荷载作用在土体中,并通过修正Mohr-Coulomb屈服准则考虑动荷载下土体应变硬化,利用土体的理想锁定状态方程(Idealized Locked Equation of State)和动态扩孔方法考虑冲击波非稳态加载,探究雷电冲击下土体的弹塑性界面及应力时程变化规律。研究表明:在雷电冲击下,土体应力随时间变化呈现先陡增后迅速衰减的趋势,应力突变点表明土体此时正处于弹塑性交界面;在应力突变点之前,土体附加应力趋于0,处于弹性状态。任一时刻下,随着逐渐远离雷电冲击点,土体应力呈现迅速衰减的趋势,应力发生突变骤降表明此处土体正处于弹塑性交界面;在突变点之后土体附加应力趋于0,处于弹性状态。土体压缩系数对土体的弹塑性界面变化具有显著影响,随着压缩指标增大,土体塑性区半径逐渐减小;随着土体黏聚力逐渐增大,土体塑性区半径逐渐减小;增大土体弹性模量可以增大土体塑性区半径,但变化幅度相对较小;电流波形对土体塑性区中的应力会产生较大影响,而对土体弹性区影响较小。

节点域承载力对半刚性钢框架地震易损性影响研究

目的 通过考察节点域承载力变化与地震易损性曲线间的关系,获得半刚性钢框架地震易损性曲线,量化节点域屈服承载力对半刚性钢框架地震易损性的影响。方法 采用OpenSEES抗震分析软件建立以节点域承载力比为主要参数的半刚性钢框架模型,通过地震需求分析和抗震能力分析,绘制不同节点域屈服承载力比(0.5~1.0)对应的半刚性钢框架地震易损性曲线。结果 节点域屈服承载力比的取值为0.7时,半刚性钢框架地震易损性曲线在四种极限状态下均小于其他半刚性钢框架,且形成包络趋势。结论 在水平地震作用下,允许节点域屈服,可显著降低钢框架的失效概率,结构的抗震性能也得到了明显改善;节点域屈服承载力比取0.7时,结构抗震性改善效果最显著。

某高架大跨梁式渡槽抗震及隔震分析

滇中引水工程场区具有地震频发、设防烈度高的特点,为保证其渡槽设施在地震下的安全性,以滇中引水工程某高架大跨梁式渡槽为研究对象,分析其抗震性能。通过大型通用有限元分析软件ABAQUS建立了考虑流固耦合作用的单跨渡槽模型,依据场区地质条件选取地震动,对盆式橡胶支座、铅芯橡胶支座及摩擦摆支座渡槽进行弹塑性动力时程分析。结果表明,隔震支座渡槽的槽身最大位移平均比盆式橡胶支座渡槽降低25.5%,最大墩底弯矩平均降低24.3%,隔震性能良好。盆式橡胶支座比隔震支座渡槽的损伤严重,槽身与槽墩的损伤部位分别为槽底支座处、槽壁变截面处及墩底。空槽工况下,铅芯橡胶支座渡槽的最大位移比满槽增加10.4%,最大墩底弯矩降低21.4%;摩擦摆支座最大位移及墩底最大弯矩分别降低20.9%及32.2%。铅芯橡胶支座的隔震周期受上部质量影响大,而摩擦摆支座的隔震周期与上部质量无关,因此摩擦摆支座更适用于渡槽结构。

硝化纤维素塑化效果与其表面张力的变化规律

为了研究发射药塑化过程中的特征参数,基于双螺杆“塑化-挤出”的方法,研究了溶剂、增塑剂种类和塑化时间对单基药塑化工艺的影响;利用Owens三液法计算乙酸乙酯(EAC)、四氢呋喃(THF)、丙酮(ACE)和1∶1醇酮混合溶剂塑化后NC的表面张力,并进一步研究了不同增塑剂对表面张力的影响。结果表明,1∶1醇酮混合溶剂塑化90 min后NC表面张力最高(43.07 mN/m),且不会粘壁粘杆,是本研究中最合适的溶剂;通过接触角计算不同塑化时间时不同含氮量(12.14%、12.80%和13.45%)NC的表面张力,其表面张力最大值均出现在90 min;拉伸力学性能研究表明塑化时间为90 min时,12.80%NC的单基药同时具有最大抗拉强度(39.10 MPa)和最大断裂伸长率(16.9%),与经验法判断塑化效果较好的时间一致;含氮量12.14%和12.80%NC表面张力最大值随着增塑剂含量的增加均提前至60 min出现,13.45%NC表面张力最大值仍于90 min时出现;对应条件下,各组样品的抗拉强度及断裂伸长率与表面张力具有相同的变化趋势。因此,在NC塑化过程中,表面张力与溶剂、增塑剂和塑化时间相关,且与拉伸力学性能变化趋势具有一致性,可作为发射药塑化效果初步判断的特征参数之一。

加工型ACR的合成及在PVC中的应用

针对聚氯乙烯(PVC)/CaCO_(3)在混炼过程中存在的塑化困难、共混时间较长、不完全塑化等加工难点以及制品表面粗糙、无光泽等市场痛点,以叔十二烷基硫醇(TDDM)为链转移剂,设计并合成了一种加工型丙烯酸酯类共聚物(ACR-P)。探究了TDDM和ACR-P的添加量对PVC/CaCO_(3)/ACR-P复合材料力学性能、流变性能、微观形貌及塑化效果的影响。结果表明,随着TDDM添加量的增加,ACR-P特性黏度逐渐下降,PVC/CaCO_(3)/ACR-P复合材料的拉伸强度和储能模量明显提高,塑化时间大幅缩短,同时冲击强度略有增加。当TDDM添加质量分数为0.8%时,PVC/CaCO_(3)/ACR-P复合材料的拉伸强度达到52.79 MPa,与PVC/CaCO_(3)相比,提高了50.27%;塑化时间由71 s缩至32 s。ACR-P添加量的增加显著地影响了PVC/CaCO_(3)/ACR-P复合材料的力学性能和加工性能,当ACR-P添加量为10份时,复合材料的拉伸强度达到61.12 MPa,与PVC/CaCO_(3)相比,提高了87.6%;塑化时间由115 s缩至25 s。动态热机械分析测试显示PVC/ACR-P复合材料只有一个玻璃化转变峰,说明PVC树脂和ACR-P两相是一个相容体系。从扫描电子显微镜可以观察到PVC/CaCO_(3)复合材料中两相界面清晰,ACR-P的引入使复合材料的界面变得模糊,这表明复合材料的相容性得到改善,力学性能和加工性能得到提升。

巨型钢框架-双钢板组合剪力墙住宅体系力学性能探究

在巨型结构体系的基础上提出巨型钢框架-双钢板组合剪力墙住宅体系。基于实际超高层混凝土住宅工程背景建立高度为156 m的计算模型,对其进行弹性反应分析及弹塑性时程分析以评估结构力学性能。通过对比主次结构不同的连接假定,探究主次结构连接方式对于结构整体性能及关键结构构件的影响。基于ABAQUS软件分析了次结构与双钢板组合剪力墙之间采用不同连接方式对剪力墙各部件的影响。最后对该结构体系进行经济性分析。研究结果表明:该结构体系能满足建筑户型无柱大空间设计要求且具有优良的力学性能和经济性指标,在设计中主、次结构连接推荐采用铰接连接。研究结果可为巨型钢框架-双钢板组合剪力墙结构的设计提供参考。

底层自复位框架结构抗震性能分析

采用有限元软件ABAQUS,以8度(0.2g)设防的地区为例,建立多层多跨的普通框架结构和底层自复位框架结构三维有限元模型。选取4条地震动,分别以0.07g、0.4g的峰值加速度输入结构,进行弹塑性时程分析,对比两个结构在地震作用下的动力响应及破坏模式。数值模拟结果表明:自复位框架结构的层间位移角与普通框架结构相近,均在规范限值内;罕遇地震作用下,损伤主要集中于底部两层的梁端。底层自复位结构的柱脚损伤小于普通框架结构,其残余位移角小于普通框架结构。