形成性测量模型:结构方程模型的新视角

形成性测量模型(Formative Model,FM)是指标变异导致潜变量变异的模型,反映性测量模型(Reflective Model,RM)是潜变量变异导致指标变异的模型。FM在模型界定、识别和估计、信效度评价以及模型应用等方面均与RM存在极大的不同。模型界定错误会使参数估计发生偏差,影响统计结论的有效性,应当审慎考虑指标和潜变量之间的关系,选择恰当的测量模型。进一步揭示两者的区别和误用带来的偏差,完善FM的识别和估计、信效度评价方法、对变量含义的解释以及高阶FM的理论解释和模型估计是未来的研究方向。

消费者对网站服务质量的心理反应机制研究——基于形成性测量模型

网站服务质量已成为网商成功与否的关键因素。以往文献对有关网站服务质量对消费者心理反应机制的研究还存在不足。为此,对网站服务质量五维度进行形成性测量模型设定,继而剖析它们对后悔、满意与忠诚的差异化影响。采用整群抽样法,收集247份有效样本,对包含形成性与反应性测量模型的结构方程模型进行统计检验。结果表明：可靠性与保证性会负向影响后悔,其中,保证性的影响效应最强;有形性、可靠性与移情性会正向影响满意,其中,移情性的影响效应最强,可靠性的次之;响应性会直接正向影响忠诚;后悔是通过满意间接影响忠诚。该研究不仅厘清了消费者对网站服务质量五维度的差异化反应机制,而且对网商进行网站服务质量管理有重要的启示。

在线大学英语写作形成性评价模型构建研究

该研究以句酷批改网为在线作文自动评分工具,结合计算机辅助大学英语教学原理和形成性评价理论,在相关文献梳理与分析基础上提出在线大学英语写作形成性评价"三阶九评模型"。即作文经过"初稿"、"修订稿"和"定稿"三个阶段,在初稿和修改稿阶段,教师在自动作文评分反馈和同学评价基础上,有针对性地做出综合评价,学生以即时评价和同学评价为参考、以教师评价为准绳修改作文。实验证明该模型可为大学生在线英语写作提供有效的反馈、减轻教师作文批阅负担,也能有效促进大学生英语写作水平提升。

医学英语课程形成性评估理论模型研究

针对目前国内医学英语课程形成性评估的不足,分析了国外两种可运用于医学英语课程的形成性评估理论模型,即Cowie和Bell理论模型,以及Heritage理论模型。除了熟悉形成性评估理论模型外,医学英语课程教师还需要掌握三项基本知识:医学学科领域知识、教学法知识和评估知识。形成性评估理论模型能给医学英语课程的教学改革与评估提供理论参考。

地域差异对居民休闲生活满意度的影响研究——基于中国五大代表性休闲城市的调查比较

本文选取杭州、成都、桂林、湛江、五大连池市五个具有地域代表性和不同经济社会水平的休闲城市进行比较研究。通过建构模型分析发现,生活条件对休闲生活满意度的影响非常显著,其中又以休闲娱乐便利度的影响最大,其次是收入和家务负担程度;地域文化对休闲生活满意度的影响较为显著。对休闲生活满意度的评价应当至少包括对生活条件、地域文化、休闲时间、个人休闲生活、邻里关系等社交状况等多个方面的综合评估。本文的模型不仅表明了地域差异导致居民休闲生活满意度的差异是显著的,而且量化了差异有预测功能,为有效提高居民的休闲生活满意度提供决策参考。

基于形成性测量模型的游客满意度研究—散客游与团队游比较

从多维度游客感知质量视角,构建基于形成性测量模型的游客满意度模型,并分别在散客游和团队游两类样本下对模型进行统计检验与比较。研究发现:对于散客游,如旅游交通与景点并不会影响满意与忠诚;但餐饮、住宿、娱乐会正向影响满意,进而间接影响忠诚。对于团队游,如餐饮、住宿与景点不会影响满意与忠诚;但娱乐、公共服务、旅行社服务会正向影响满意,进而间接影响忠诚。无论是散客游,还是团队游,购物都对满意与忠诚有正向影响;娱乐与公共服务对满意都有正向影响,但两者之间也存在显著差异。

基于扎根理论的员工劳动关系满意度研究

劳动关系满意度是和谐劳动关系理念下的重要本土化概念,国内学者在其维度结构上进行了初步探索,但研究结果却大相径庭。基于扎根理论质性研究方法对工会企业员工劳动关系满意度的构成维度进行重新梳理,并采用形成性模型的构建方法,开发了劳动关系满意度测量工具。研究结果表明:劳动关系满意度由员工关怀、员工参与、劳动争议管理、劳动条件与保障、劳动报酬、劳动负荷和员工成长7个维度构成,共36个题项,该量表具有较好的效度。研究结论为企业内部的劳动关系管理实践提供了有益启示。

Advance and trend of friction study in plastic forming

Friction is a critical issue in plastic forming which influences forming force, metal flow, forming quality and service life of die. Since friction is a highly nonlinear physical phenomenon which is interactively affected by so many factors, great efforts have been made to study the friction mechanism and controlling. The research progress of friction issues in plastic forming was summarized and discussed from four aspects： testing, characterizing, modeling and optimization/controlling. Considering urgent demands for green, efficient and precise forming of high-performance, lightweight and complex components in high-tech industries such as aerospace and automotive, the trends and challenges of friction study in plastic forming were proposed.

PPP模式下高速公路建设项目团队胜任力影响因素

PPP模式具有优化风险、扩大融资渠道、提高运营成功率等优点,因此该模式下的项目团队应具备更高的要求。基于胜任力理论,通过文献研究、调查访谈以及因子分析,确定了团队胜任力影响因素模型的结构,应用PLS-SEM建模方法,以形成性和反映性混合的观察指标作为测量模型,构建了PPP模式下高速公路建设项目团队胜任力影响因素模型。应用Smart PLS 2.0软件对团队胜任力影响因素模型进行分析,结果表明:专业能力、组织一致性、创新能力对团队胜任力有不同程度的正向影响,专业能力不仅直接影响团队胜任力,还通过组织一致性和创新能力两个中介变量来间接影响胜任力,其中专业能力的影响效应最大,组织一致性其次,创新能力最小。

基于PLS-SEM的烟草工艺参数关联关系分析研究

本文研究如何发掘制丝流程中松散回潮、加料和切烘阶段中诸多工艺参数与各阶段以及最终输出产品的品质之间的关联性。通过对某烟厂制丝生产流水线上收集到的共121个工艺参数观察变量3064条记录进行清洗和变量筛选后,选取了填充值作为最终输出指标,建立形成性偏最小二乘结构方程模型展开分析探究。确定路径模式,建立结构方程模型,并给出模型评估结果,以及提升填充值的参数调整优化建议。

Prediction of fracture limits of Ni-Cr based alloy under warm forming condition using ductile damage models and numerical method

The stretch forming and the deep-drawing processes were carried out at 300 and 673 K to determine the safe forming and fracture limits of IN625 alloy.The experimentally obtained strain-based fracture forming limit diagram(FFLD)was transformed into a stress-based(σ-FFLD)and effective plastic strain(EPS)vs triaxiality(η)plot to remove the excess dependency of fracture limits over the strains.For the prediction of fracture limits,seven different damage models were calibrated.The Oh model displayed the best ability to predict the fracture locus with the least absolute error.Though the experimentally obtained fracture limits have only been used for the numerical analysis,none of the considered damage models predicted the fracture strains over the entire considered range of stress triaxiality(0.33<η<0.66).The deep drawing process window helped to determine wrinkling,safe and fracture zones while drawing the cylindrical cups under different temperature and lubricating conditions.Further,the highest drawing ratio of 2 was achieved at 673 K under the lubricating condition.All the numerically predicted results of both stretch forming and deep drawing processes using the Hill 1948 anisotropic yielding function were found to be good within the acceptable range of error.

Influence of process parameters on properties of AA6082 in hot forming process

The influences of process parameters on mechanical properties of AA6082in the hot forming and cold-die quenching(HFQ)process were analysed experimentally.Transmission electron microscopy was used to observe the precipitate distribution and to thus clarify strengthening mechanism.A new model was established to describe the strengthening of AA6082by HFQ process in this novel forming technique.The material constants in the model were determined using a genetic algorithm tool.This strengthening model for AA6082can precisely describe the relationship between the strengths of formed workpieces and process parameters.The predicted results agree well with the experimental ones.The Pearson correlation coefficient,average absolute relative error,and root-mean-square error between the calculated and experimental hardness values are0.99402,2.0054%,and2.045,respectively.The model is further developed into an FE code ABAQUS via VUMAT to predict the mechanical property variation of a hot-stamped cup in various ageing conditions.

Thickness distribution of multi-stage incremental forming with different forming stages and angle intervals

Although multi-stage incremental sheet forming has always been adopted instead of single-stage forming to form parts with a steep wall angle or to achieve a high forming performance, it is largely dependent on empirical designs. In order to research multi-stage forming further, the effect of forming stages(n) and angle interval between the two adjacent stages(Δα) on thickness distribution was investigated. Firstly, a finite element method(FEM) model of multi-stage incremental forming was established and experimentally verified. Then, based on the proposed simulation model, different strategies were adopted to form a frustum of cone with wall angle of 30° to research the thickness distribution of multi-pass forming. It is proved that the minimum thickness increases largely and the variance of sheet thickness decreases significantly as the value of n grows. Further, with the increase of Δα, the minimum thickness increases initially and then decreases, and the optimal thickness distribution is achieved with Δα of 10°.Additionally, a formula is deduced to estimate the sheet thickness after multi-stage forming and proved to be effective. And the simulation results fit well with the experimental results.

Nonlinear Modeling of a High Precision Servo Injection Molding Machine Including Novel Molding Approach

A nonlinear mathematical model of the injection molding process for electrohydraulic servo injection molding machine (IMM) is developed.It was found necessary to consider the characteristics of asymmetric cylinder for electrohydraulic servo IMM.The model is based on the dynamics of the machine including servo valve,asymmetric cylinder and screw,and the non-Newtonian flow behavior of polymer melt in injection molding is also considered.The performance of the model was evaluated based on novel approach of molding - injection and compress molding,and the results of simulation and experimental data demonstrate the effectiveness of the model.

Formation Mechanism and Characteristics Research of Ball Lightning Based on Vortex Model

The strange characteristics of ball lightning are considered as a question hard to explain. In order to solve the problem, in this paper a complete model of plasma vortex is presented for the ball lightning. By ideal MHD equations, through imposing disturbance to plasma column, the possibility of sausage and kink instability of the lightning channel is analyzed from the perspective the minimum potential energy. The conclusion is that the kink instability （m = 1） is most prone to occur. And when instability occurs, because of the difference of the magnetic field in the twisted area, the magnetic pressure makes the trend further and therefore forming the plasma vortex that may eventually turn into ball lightning if the energy of the vortex is large enough. The existence of the vortex makes ball lightning have a short period of time stability. By the proposed model, the ball lightning features that are hard to understand in the past are explained. In this paper, the reason for bead lightning is also explained from the perspective of the sausage instability.

Expression changes and roles of matrix metalloproteinases in a rat model of traumatic deep vein thrombosis

Objective：To study the expression changes of matrix metal loproteinases （MMPs） in traumatic deep vein thrombosis （TDVT） in a rat model with the aid of gene chip technology and to explore the roles of MMPs in TDVT.Methods：Totally 150 Sprague Dawley rats were randomly divided into control group （n=10） and model group （n=140）. Rat models of TDVT were established by clamping the femoral vein and fixing the bilateral hind limbs. Then fixation of the hip spica with plaster bandage was conducted.According to the observation phases and/or biological situations of the femoral vein thrombosis, the model rats were further divided into 7 groups. Vascular tissues were obtained from each group through noninvasive incision into the femoral vein at corresponding time points. We adopted the Trizoi one-step method for total RNA extraction,Affymetrix RAT 230 2.0 array for detection of RNA expressions and fold change （FC） analysis for changes of differential expressions of MMPs in each group. The main outcome parameters measured included expressions of MMP-2,MMP-3, MMP-7, MMP-8, MMP-9, MMP-10, MMP-11,MMP- 12, MMP-13, MMP- 14, MMP- 16, MMP-23 and MMP-24. Gene array data of these MMPs were analyzed by the Affymetrix Microarray Analysis software （Version 5.0）.Results：FC analysis showed differential expressions of MMPs in each group during the course of TDVT. At the initial period of thrombosis, MMP-2, MMP-3, MMP-7,MMP-8, MMP-9, MMP- 10, MMP-11, and MMP-24 had significantly high expression, while MMP-12, MMP-13,MMP-14, MMP-16 and MMP-23 had relatively low expression. MMPs were all highly expressed at the peak time of thrombosis. In the process of thrombus resolution,MMP-2, MMP-10, MMP-16 and MMP-24 have relatively low expression, while MMP-12, MMP-13, MMP-14,MMP-16 and MMP-23 have significantly high expression.Conclusion：MMPs may affect the process of TDVT through transcription regulation of the fibrinolysis-anti-fibrinolytic system during the course of thrombosis and thrombus resolution.

Classification of breast lesions based on a dual S-shaped logistic model in dynamic contrast enhanced magnetic resonance imaging

This study proposes a novel dual S-shaped logistic model for automatically quantifying the characteristic kinetic curves of breast lesions and for distinguishing malignant from benign breast tumors on dynamic contrast enhanced (DCE) magnetic resonance (MR) images.D(,) is the diagnostic parameter derived from the logistic model.Significant differences were found in D(,) between the malignant benign groups.Fisher's Linear Discriminant analysis correctly classified more than 90% of the benign and malignant kinetic breast data using the derived diagnostic parameter (D(,)).Receiver operating characteristic curve analysis of the derived diagnostic parameter (D(,)) indicated high sensitivity and specificity to differentiate malignancy from benignancy.The dual S-shaped logistic model was effectively used to fit the kinetic curves of breast lesions in DCE-MR.Separation between benign and malignant breast lesions was achieved with sufficient accuracy by using the derived diagnostic parameter D(,) as the lesion's feature.The proposed method therefore has the potential for computer-aided diagnosis in breast tumors.