SUBCRITICAL ASYMPTOTIC BEHAVIOR IN THE MODIFIED LUSHNIKOV PROCESS OF POLYMERIZATION

We consider a modified Lnshnikov process as a model of a chemical polymer ization anf study the asymptotic behavior (in the thermodynamic limit;as N →∞)of a particular probability distribution on the set of N-dimensional vectors,tile kth component of which is the number of k-mers.The study study establisles the existence of three stages (subcritical,near-critical and supercritical stages)of polymerization,dependenting upon the ratio of association and dissociation rates of f polymers.The present paper concentrates on the analysis of tile subcritical stage.In the sibcritical.stages we show that tile size of the largest length of polymers of stize N is of the order.log N as N →+∞.

Flow Stress Behavior and Processing Map of Al-Cu-Mg-Ag Alloy during Hot Compression

The hot deformation behavior of Al-Cu-Mg-Ag was studied by isothermal hot compression tests in the temperature range of 573-773 K and strain rate range of 0.001-1 s^-1 on a Gleeble 1500 D thermal mechanical simulator. The results show the flow stress of Al-Cu-Mg-Ag alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate and temperature, the flow stress equation is estimated to illustrate the relation of strain rate and stress and temperature during high temperature deformation process. The processing maps exhibit two domains as optimum fields for hot deformation at different strains, including the high strain rate domain in 623-773 K and the low strain rate domain in 573-673 K.

Properties and corrosion behavior of Al based nanocomposite foams produced by the sintering-dissolution process

The properties orAl based nanocomposite metal foams and their corrosion behaviors were investigated in this study. For this, the composite metal foams with different relative densities （porosity） reinforced with alumina nanoparticles were prepared using a powder me- tallurgy-based sintering-dissolution process （SDP） and NaC1 particles were used as space holders. Then, the effect of nanoparticle rein- forcement and different amounts of NaC1 space holders （corresponding porosity） on the microstructure, morphology, density, hardness, and electrochemical specifications of the samples were investigated. It was found that as the relative density increased from 60% to 70%, the wall thickness increased from about 200 to 300 pro, which led to a decrease in pore size. Also, the addition of nanoparticle reinforcement and the increased relative density result in increasing metal foam hardness. Moreover, electrochemical test results indicated that increasing the A1203 content reduced the corrosion rate, but increasing the porosity enhanced it.

S^(2-) behaviors analysis in leaching SrS and precipitating high purity SrCO_3 by reduction-decomposition process

A new preparation method （reduction-decomposition process） for high purity SrCO3 was investigated, which mainly includes four processes: reduction, leaching, purification and precipitation. The affecting factors about S2- behaviors in leaching process and the effects of variables on purity and particle sizes distribution of SrCO3 were analyzed theoretically and practically. It is concluded that with the increase of temperature or decrease of pH value in leaching process, the strontium recovery increases, but SrS decomposes and hydrogen sulphide （H2S） gas discharges. The purity of SrCO3 is dependent on dissolution-recrystallization times, for example, the purity of （SrCO3） is as high as 99.97% when it is recrystallized three times. Besides, the solution concentration of Sr（OH）2 and flow rate of CO2 have important effects on particle size distribution of SrCO3 particles, especially, the particle sizes of （SrCO3） meanly distribute in 0.11.0 μm when the flow rate of CO2 is about 2 000 mL/min and other parameters are invariable.

Rheological Behaviors and Processing Windows of Low Viscosity Epoxy Resin for VIMP

The chemorheological behaviors of a low viscosity epoxy resin system （Huntsman 1564/3486） for vacuum infusion moulding process （VIMP） were studied with viscosity experiments.The dual-Arrhenius rheological model and the engineering viscosity model were established and compared with the experimental data.The result showed that the viscosity in the earlier stage calculated by dual-Arrhenius model were smaller than the experimental data,while the data calculated by the engineering model were larger.Combining the two models together can predict the rheological behaviors of the resin system in a more credible manner.The processing windows of the resin system for VIMP were determined based on the two models.The optimum processing temperature is 30-45 ℃.

THE NEAR-CRITICAL AND SUPER-CRITICAL ASYMPTOTIC BEHAVIOR IN THE THERMODYNAMIC LIMIT OF REVERSIBLE RANDOM POLYMERIZATION PROCESSES

In this paper, the near-critical and super-critical asymptotic behavior of a reversible Markov process as a chemical model for polymerization was studied. The results of the present paper, together with an analysis of the sub-critical stage, establish the existence of three distinct stages (sub-critical, near-critical and super-critical stages) of polymerization (in the thermodynamic limit as N --> +infinity,),depending on the value of strength of the fragmentation reaction. These three stages correspond to the size of the largest length of polymers of size N to be itself of order log N, Nm/m+1 (m greater than or equal to 2, m not equal 4n, n greater than or equal to 1) and N, respectively.

Effect of melting temperature on microstructural evolutions, behavior and corrosion morphology of Hadfield austenitic manganese steel in the casting process

In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium silicate/CO_2 method, using a blind riser, and then the desired molten steel was obtained using a coreless induction furnace. The casting was performed at melting temperatures of 1350, 1400, 1450, and 1500°C, and the cast blocks were immediately quenched in water. Optical microscopy was used to analyze the microstructure, and scanning electron microscopy(SEM) and X-ray diffractrometry(XRD) were used to analyze the corrosion morphology and phase formation in the microstructure, respectively. The corrosion behavior of the samples was analyzed using a potentiodynamic polarization test and electrochemical impedance spectroscopy(EIS) in 3.5 wt% NaCl. The optical microscopy observations and XRD patterns show that the increase in melting temperature led to a decrease of carbides and an increase in the austenite grain size in the Hadfield steel microstructure. The corrosion tests results show that with increasing melting temperature in the casting process, Hadfield steel shows a higher corrosion resistance. The SEM images of the corrosion morphologies show that the reduction of melting temperature in the Hadfield steel casting process induced micro-galvanic corrosion conditions.

Effect of laser shock processing on residual stress and fatigue behavior of 6061-T651 aluminum alloy

Laser shock processing is a very new technique and an emerging modern process that generates compressive stresses much deeper into the surfaces of metals or alloys. A brief parametric study of the effect of laser parameters on fatigue behavior and residual stress state generated in 6061-T651 alloy specimens was summarized. Residual stress of 6061-T651 alloy was analyzed both before and after laser processing with multishocks. The material remains in compressive residual stress of approximate 1mm in depth which is approximately 10 times deeper than that can be achieved with the conventional technique, and the maximal compressive residual stress at the surface of the sample is about -350MPa. Near the surface, yield strength and hardness are found to be increased by the laser shock. The ratio of fatigue crack initiation life for the laser-shocked to unshocked specimens is found to be 4.9 for specimens. The results clearly show that LSP is an effective surface treatment technique for improving the fatigue performance of aluminum alloys.

深轮辐齿坯多工位闭式模锻材料流动规律研究

探索闭式热模锻成形时材料的流动规律是控制充填不满等成形缺陷、获得高精度模锻件的理论基础。针对深轮辐齿坯件热模锻成形时易出现填充不满的问题,以某SCr420H深轮辐齿坯为研究对象,基于齿坯件结构分析,设计了“下料-加热-镦粗-预锻Ⅰ-预锻Ⅱ-终锻”的多工位闭式热模锻工艺方案;基于Deform软件,构建了深轮辐齿坯件多工位闭式热模锻全流程有限元模拟模型;采用试验验证了有限元模型的可靠性,并对多工位闭式热模锻成形过程中材料的流动规律进行了研究。结果表明:镦粗比为3.7时,可获得外形良好的圆饼形预制坯,镦粗时受上下表面摩擦效应的影响,材料径向流动不均匀,在坯件腰部出现鼓形;预锻Ⅰ工位成形出用于定位的底面内凹结构,同时减小了后续工位材料填充难度;预锻Ⅱ和终锻成形时的材料流动规律相似,成形前期材料集中流向轮缘部分、成形中期主要流向轮毂部分、末期流向圆角处;终锻成形时未出现材料填充不满的缺陷,在成形后期,少量金属材料从终锻上下模的导向间隙中流出,形成纵向飞边。通过生产试验,成形出填充良好的深轮辐齿坯件,模拟数值获得温度与实际生产数值最大误差不超过3.15%,纵向飞边高度小于0.5 mm,零件各尺寸偏差均小于0.2 mm,验证了所设计多工位闭式模锻工艺的合理性。

组织正念对矿工安全行为的影响机理

为明晰组织正念对安全行为的影响机理,基于自我决定理论和社会信息加工理论,构建了包含组织正念、和谐安全激情、领导安全承诺和安全行为的概念模型;以山西省431名一线矿工为研究对象,采用结构方程模型进行假设和实证检验。研究结果表明:组织正念显著正向影响安全行为,和谐安全激情在此关系中起中介作用;领导安全承诺调节了组织正念的影响,即领导安全承诺越高,和谐安全激情的中介作用越强;煤矿管理者应提高组织动态应急处理能力,切实履行安全承诺,提升矿工安全行为。

从“化繁为简”到“繁简相生”:公共安全政民合作治理的过程机制研究——以深圳市B区义警为例

“乌卡时代”,厘清政民合作治理过程机制对于实现公共安全治理向事前预防转型至关重要。既有研究主要侧重于分析政民合作治理的前因条件与合作绩效,却忽视了对中国情境下政民合作治理过程的分析。鉴于此,以合作治理理论为基础,立足政民双主体视角,构建了基于公共安全政民合作治理“合作动机一行为过程一价值共创”的过程机制解释模型。公共安全政民合作治理是政民双方基于各自的合作动机,通过利益互融、资源互补、协调互动、信任互惠、成效助推,最终实现价值共创的循环选代过程。

Ti65钛合金热变形行为及本构方程

利用WDW-100H万能试验机对Ti65钛合金进行了等温恒应变速率热压缩实验,变形温度为840~1010℃,应变速率为0.001~0.1 s^(-1),建立了应变补偿型Arrhenius本构方程和热加工图。结果表明:在840~880℃内流动应力曲线波动较大,在880℃时峰值应力与稳定后应力之间的降幅最小,为24%,对温度敏感性较大;在920~1010℃内流动应力曲线较为平稳,在920℃时峰值应力与稳定后应力之间的降幅最大,为30%,对温度敏感性较小。采用应变补偿型Arrhenius本构方程可以较好地预测Ti65钛合金在变形条件为840~1010℃和0.001~0.1 s^(-1)下流动应力的变化规律。根据相关系数R=0.994和平均相对误差e AARE=6.9%可以判断出该模型精度较高,平均应变速率敏感性指数m为0.31。在应变为1.0时建立热加工图,发现Ti65钛合金在低温高应变速率下可能会发生失稳,在低温低应变速率下会发生再结晶行为。最终得出Ti65钛合金的最佳热变形工艺参数,即温度区间为940~980℃,应变速率区间为0.01~0.001 s^(-1)。

挤压Mg-Y-Ni-Co合金的显微组织、加工性能及塑性变形行为

本工作通过光学显微镜(OM)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和万能实验机对挤压Mg-2Y-0.5Ni-0.5Co(%,原子分数)合金的显微组织、加工性能和塑性变形行为进行了研究。挤压合金的显微组织主要由α-Mg、沿挤压方向分布的片层状和细小块状18R-LPSO相、MgY(Co,Ni)_(4)相以及晶粒内细条纹状的14H-LPSO相组成。拉伸测试结果显示,挤压合金具有良好的室温塑性,断裂延伸率均高于15%。随着温度的升高和应变速率的降低,合金的拉伸强度降低,而塑性增强。合金在300℃、1×10^(-3)s^(-1)和1×10^(-4)s^(-1)应变速率下断裂延伸率分别为117.87%和143.9%,具有准超塑性。通过构建的热加工图谱,优化出合金的稳定加工区间为温度275~300℃、应变速率10^(-4)~10^(-3)s^(-1)。挤压合金的变形行为随温度和应变速率的变化而改变,在低温(室温(RT)到200℃)和不同应变速率下,合金的变形机制以位错滑移为主;在高温(300℃)和低应变速率(1×10^(-4)s^(-1)和1×10^(-3)s^(-1))下,合金的变形机制为晶界滑移协调的位错滑移。

认知神经及语言训练配合感觉统合训练对自闭症患儿的干预效果

目的 探讨认知神经及语言训练配合感觉统合训练对自闭症患儿的干预效果。方法 选取2022年1月至2023年1月我院收治的自闭症患儿90例,随机分为两组各45例。对照组实施常规训练,观察组实施认知神经及语言训练配合感觉统合训练。对比两组的语言发育状态、孤独行为和感觉统合能力。结果 干预后,观察组孤独症儿童心理教育量表评分高于对照组,孤独症儿童行为检查量表评分低于对照组,儿童感觉统合能力发展评定量表评分高于对照组(P <0.05)。结论 认知神经及语言训练配合感觉统合训练可有效提高自闭症患儿的语言发育状态及感觉统合能力,改善其孤独行为。

建设工程事故文本的知识发现:以PPE类不安全行为为例

为了丰富建设工程领域的安全知识,从事故文本中挖掘和发现施工人员的不安全行为,以个人防护用品PPE类不安全行为为例,采用基于规则的自然语言处理方法,从事故文本中自动抽取此类不安全行为。从政府官网等收集195份建设工程事故调查报告作为文本挖掘语料,通过哈尔滨工业大学的语言技术平台LTP展开词法分析和依存句法分析,构建PPE类不安全行为的11条抽取规则并确定抽取流程。再以网络爬虫收集的427份事故调查报告展开实例应用,按照流程自动抽取PPE类不安全行为。结果表明:平均抽取准确率为94.70%,召回率为67.57%。研究能够为建设工程事故文本的知识发现提供理论启示和实践路径。

基于CenterNet的跑步姿态鉴别系统的设计

为了改善目前大众跑步姿势普遍不规范的现状,提出了一种基于CenterNet的跑步姿态鉴别系统。首先,通过截图、拍照的方式自制数据集,并对数据集进行清洗、标注和分析,消除数据无关信息与简化数据。其次,引入多尺度通道注意力机制与添加十字星变形卷积2种方式改进CenterNet算法模型,将动作图像转化为数字信息和特征向量,并以此为基础,利用KNN(K-nearest neighbors)算法对跑步姿态类型进行分类。最后,与经典模型方案进行对比,验证改进CenterNet算法鉴别系统的有效性。结果表明:改进的CenterNet模型的精确率与召回率都有所提升,其参数量与计算量降低。所提算法模型能够对大多数不良姿势作出及时、准确反馈,有效帮助跑步爱好者发现问题,从而改善跑步姿态、提高运动效率、预防伤病。

Identification of Behavior of Voluntary Traceability and Analysis of Its Determinants: A Case Study of Hog Slaughtering and Processing Firms in Zhejiang Province,China

In recent years, the Chinese government has highlighted the importance of adopting hog safety/quality traceability, and a growing amount of research continues to entice firms to adopt traceability systems. In this study, a survey was conducted on a sample of pig slaughtering and processing firms in Zhejiang, China through personal interviews and emails. The aim of this study was to examine the determinants of firm behavior on the implementation of voluntary traceability systems with more stringent standards and controls than those of the mandatory system in China. The results revealed that motivation based on product quality improvement, capital ability and role perception （business type） had significantly positive relationships with a firm＇s voluntary traceability. Other incentives, such as operation improvement, recall risk reduction, reduced occurrence of safety issues, and technical strength were not found to be supportive in our study. This study provides an opportunity to better understand the determinants of firm behavior on voluntary traceability, particularly in light of the fact that some Chinese firms are facing the threat of criminal action for the use of illegal additives and the abuse of Clenbuterol. Policy recommendations on encouraging the implementation of pork safety voluntary traceability by hog slaughtering and processing firms are also discussed.

基于图像处理的行人过街安全警示系统设计与研究

为了提高行人过街的安全性和效率,避免安全事故的发生,设计一种可以实时检测行人过街行为以及车辆往来的行人过街安全警示系统。该系统采用图像处理技术和嵌入式系统技术,能够实时监测行人、车辆和交通信号灯状态,能准确快速地提醒过街行人注意出行及安全,提高城市交通秩序,有助于推进智慧城市建设和交通安全领域的技术创新,具有一定的理论和实践价值。

基于EPPM理论胃癌患者一级亲属胃癌筛查行为干预方案构建

目的构建基于拓展平行过程理论(extended parallel process model,EPPM)的胃癌患者一级亲属胃癌筛查行为干预方案。方法2023年3—11月,在文献回顾和小组讨论的基础上形成基于EPPM理论的胃癌患者一级亲属胃癌筛查行为干预方案初稿,采用德尔菲专家函询法对18名专家进行2轮函询,形成干预方案终稿。结果2轮专家函询共构建2个一级指标、4个二级指标和27个三级指标的筛查干预方案。专家权威系数分别为0.822、0.884;2轮函询的肯德尔协调系数分别为0.176、0.373,差异有统计学意义(P<0.001)。结论构建的基于EPPM理论的胃癌患者一级亲属胃癌筛查行为干预方案具有可靠性和实用性,以期为胃癌患者一级亲属胃癌筛查行为干预提供借鉴依据。

全过程工程咨询项目咨询方行为风险因素间影响关系研究

全过程工程咨询是建筑业未来的发展趋势,但其顺利推行存在一定的阻碍,如何实现风险的有效管控是目前亟需解决的问题之一。项目风险由客观风险和主体行为风险构成,工程项目主体的不当行为将会对项目产生重大影响。本文针对主体行为风险中全过程工程咨询单位带来的风险,从项目全生命周期角度出发,运用文献研究法、专家访谈法和因子分析法对咨询方行为风险因素进行系统识别,构建了包含6个阶段、13项一级风险和34项二级风险的全过程工程咨询项目咨询方行为风险因素体系,运用FUZZY-DEMATEL-ISM模型对风险因素间相互影响关系和风险传导路径进行分析,发现可行性研究不到位、前期规划咨询不当、项目评估不达标是其中的关键风险因素,并提出了相应的风险管理建议。