阀门喷涂机器人的轨迹规划与优化求解

为对特定阀门工件的外表自由曲面进行精确喷涂,提出以阀门外形尺寸和机器人本体结构为约束条件,对喷涂 机器人的工作空间进行了合理优化。利用MATLAB对多变量有约束非线性函数优化求解,得到了机器人主连杆杆长以 及相应的关节转角范围;对阀门进行了参数描述,并建立喷涂轨迹路径数学模型;通过基于ADAMS的虚拟样机建模、运 动仿真和MATLAB数值求解的相互协同和相互验证,得到了合理的关节角逆解。通过优化后的逆解进行仿真喷涂验证 了轨迹规划和优化求解方法的合理性。     

The occupational (im)mobility of migrants in Italy

Migrants usually experience a downward mobility in their host country’s economy and are over-represented among lower status jobs. The present study contributes to the knowledge on migrant occupation mobility in Italy, assuming a longitudinal perspective and focusing on two aspects: first, the entry of migrants into the Italian labour market and, second, the working trajectories of migrants in Italy, reflecting the role of the first step in determining the following trajectory and migrants’ strategies.     

The trajectory of life satisfaction and its associated factors among adolescents in South Korea

Korean adolescents are reportedly unhappy, dissatisfied with their lives, yet little is known about why. This study is set out to examine their life satisfaction and its change over time and the factors associated with its change. The analyses were conducted using the data from the Korean Youth Panel Survey (2004–2008) on a total of 3449 adolescents. The latent growth curve modelling result shows that Korean adolescents’ life satisfaction had a linear trajectory over a five-year period, and that while peer and teacher relationships were identified as important protective factors, academic stress and their internalised problems such as depression had long-lasting effect over time. Based on such findings, implications for social work practice with adolescents are discussed.     

相似原理及其在液力耦合器研制中的应用

本文阐述了液力耦合器原理及柔性传动的特点,介绍了相似原理在液力耦合器研制中的应用,并给出性能偏差评价。     

Multivariate singular spectrum analysis for forecasting revisions to real-time data

Real-time data on national accounts statistics typically undergo an extensive revision process, leading to multiple vintages on the same generic variable. The time between the publication of the initial and final data is a lengthy one and raises the question of how to model and forecast the final vintage of data – an issue that dates from seminal articles by Mankiw et al. [51 Mankiw, N. G., Runkle, M. and Shapiro, M. D. 1984. Are preliminary announcements of the money stock rational forecasts?. J. Monetary Econ., 14: 15–27. [Crossref], [Web of Science ®] [Google Scholar]], Mankiw and Shapiro [52 Mankiw, N. G. and Shapiro, M. D. 1986. News or noise? An analysis of GNP revisions. Surv. Curr. Bus. May, : 20–25.  [Google Scholar]] and Nordhaus [57 Nordhaus, W. D. 1987. Forecasting efficiency: Concepts and applications. Rev. Econ. Stat., 4: 667–674.  [Google Scholar]]. To solve this problem, we develop the non-parametric method of multivariate singular spectrum analysis (MSSA) for multi-vintage data. MSSA is much more flexible than the standard methods of modelling that involve at least one of the restrictive assumptions of linearity, normality and stationarity. The benefits are illustrated with data on the UK index of industrial production: neither the preliminary vintages nor the competing models are as accurate as the forecasts using MSSA.     

Group-based Criminal Trajectory Analysis Using Cross-validation Criteria

In this article, we discuss the challenge of determining the number of classes in a family of finite mixture models with the intent of improving the specification of latent class models for criminal trajectories. We argue that the traditional method of using either the Proc Traj or Mplus package to compute and maximize the Bayesian Information Criterion (BIC) is problematic: Proc Traj and Mplus do not always compute the MLE (and hence the BIC) accurately, and furthermore, BIC on its own does not always indicate a reasonable-seeming number of groups even when computed correctly. As an alternative, we propose the new freely available software package, crimCV, written in the R-programming language, and the methodology of cross-validation error (CVE) to determine the number of classes in a fair and reasonable way. In this article, we apply the new methodology to two samples of N = 378 and N = 386 male juvenile offenders whose criminal behavior was tracked from late childhood/early adolescence into adulthood. We show how using CVE, as implemented with crimCV, can provide valuable insight for determining the number of latent classes in these cases. These results suggest that cross-validation may represent a promising alternative to AIC or BIC for determining an optimal number of classes in finite mixture models, and in particular for setting, the number of latent classes in group-based trajectory analysis.     

Identifying and Explaining Different Poverty Trajectories Using a Group‐based Trajectory Analysis – A Case Study of South Korea

In this study, we propose a group‐based trajectory analysis to examine why and how people fall into and out of poverty despite spiralling public expenditure on anti‐poverty policies. By analyzing the poverty experiences of 1,001 low‐income households between 1999 and 2008 in Korea, we identify five groups based on their poverty trajectories: exiting, declining, slowly rising, rapidly rising and chronic. Household members in each group demonstrate heterogeneous labour market experiences, educational levels and demographic factors. The exiting group has a high proportion of full‐time workers, high school graduates, and younger and male‐headed households, whereas the chronic group has more part‐time workers, high school dropouts, and older and female‐headed households. Among the declining, slowly rising and rapidly rising groups, educational background, age and sex are factors that differentiate the poverty dynamics of household members. Lastly, a number of social policies for helping low‐income households to leave and stay out of poverty are proposed.     

英语“IN”和汉语“里”意象图式的认知对比研究

随着认知语言学的兴起与发展,国内外不少学者对其从不同角度进行历时和共时的研究,就方位介词而言,多数学者重在分析同一语言下的某个介词,比如＂上-下＂的语用认知。本文尝试从对比角度探讨英汉两种语言下的对应词＂IN＂和汉语＂里＂的意象图式的认知分析,以期能够从一定程度上对跨语言层面意象图式的认知研究起到一定的启迪作用。     

用等效外径法对塔式钻具组合防斜问题探讨

针对气体钻垂直井中塔式钻具组合防斜效果具有不确定性,在三弯矩方程的基础上,提出等效外径法对不等截面的塔式钻具进行力学特性研究,以等效外径法计算为依据,开发了简易的VB程序实现塔式钻具组合的力学分析以及对钻具组合优化设计和钻井参数调整,同时用ANSYS有限元软件二次开发ADPL语言编程实现塔式钻具组合侧向力的计算,这样不仅可以得到等效外径法计算的钻具侧向力大小,也可以得到有限元软件计算出的侧向力数据,并进行两种结果的对比分析。通过实例分析,所编写的VB程序能得到比较准确而且高精度的计算结果,同时探讨了影响钻具防斜效果的原因和改进方案。