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The assembly simulation in tolerance analysis is one of the most important steps for the tolerance design of mechanical products. However, most assembly simulation methods are based on the rigid body assumption, and those assembly simulation methods considering deformation have a poor efficiency. This paper aims to propose a novel efficient and precise tolerance analysis method based on stable contact to improve the efficiency and reliability of assembly deformation simulation.

The proposed method comprehensively considers the initial rigid assembly state, the assembly deformation and the stability examination of assembly simulation to improve the reliability of tolerance analysis results. The assembly deformation of mating surfaces was first calculated based on the boundary element method with optimal initial assembly state, then the stability of assembly simulation results was assessed by the density-based spatial clustering of applications with noise algorithm to improve the reliability of tolerance analysis. Finally, combining the small displacement torsor theory, the tolerance scheme was statistically analyzed based on sufficient samples.

A case study of a guide rail model demonstrated the efficiency and effectiveness of the proposed method.

The present study only considered the form error when generating the skin model shape, and the waviness and the roughness of the matching surface were not considered.

To the best of the authors’ knowledge, the proposed method is original in the assembly simulation considering stable contact, which can effectively ensure the reliability of the assembly simulation while taking into account the computational efficiency.

The step effect and support structure generated by the manufacturing process of fused deposition molding parts increase the consumables cost and decrease the printing quality. Multiorientation printing helps improve the surface quality of parts and reduce support, but path interference exists between the printing layer and the layers printed. The purpose of this study is to design printing paths between different submodels to avoid interference when build orientation changed.

Considering support constraint, build orientation sequence is designed for submodels decomposed by model topology. The minimum printing angle between printing layers is analyzed. Initial path through the oriented bounding box is planned and slice interference relationship is then detected according to the projection topology mapping. Based on the relationship matrix of multiorientation slice, feasible path is calculated by directed graph (DG). Final printing path is determined under support constraint and checked by minimum printing angle. The simulation model of the robotic arm is established to verify the accessibility of printing path under the constraint of support and slice.

The proposed method can reduce support structure, decrease volume error and effectively solve the interference problem of the printing path for multiorientation slice.

The method based on projection topology mapping greatly improves the efficiency of interference detection. A feasible path calculated through DGs ensures the effectiveness of the printing path with the constraint of support and slice.

This paper aims to propose a suitable atomizing solidification chitosan (CS) gel liquid extrusion molding technology for the three dimensional (3D) printing method, and experiments verify the feasibility of this method.

This paper mainly uses experimental means, combined with theoretical research. The preparation method, solidification forming method and 3D printing method of CS gel solution were studied. The CS gel printing mechanism and printing error sources are analyzed on the basis of the CS gel ink printing results, printing performance with different ratios of components by constructing a gel print prototype, experiments evaluating the CS gel printing technology and the effects of the process parameters on the scaffold formation.

CS printing ink was prepared; the optimal formula was found; the 3 D printing experiment of CS was completed; the optimal printing parameters were obtained; and the reliability of the forming prototype, printing ink and gel printing process was verified, which allowed for the possibility to apply the 3 D printing technology to the manufacturing of a CS gel structure.

This study can provide theoretical and technical support for the potential application of CS 3 D printed gels in tissue engineering.

This study contributes to the understanding of the health effects of pesticides exposure and of how pesticides have been and should be regulated.

This study presents literature reviews for the period 2000–2013 on (i) the health effects of pesticides and on (ii) preference valuation of health risks related to pesticides, as well as a discussion of the role of benefit-cost analysis applied to pesticide regulatory measures.

This study indicates that the health literature has focused on individuals with direct exposure to pesticides, i.e. farmers, while the literature on preference valuation has focused on those with indirect exposure, i.e. consumers. The discussion highlights the need to clarify the rationale for regulating pesticides, the role of risk perceptions in benefit-cost analysis, and the importance of inter-disciplinary research in this area.

This study relates findings of different disciplines (health, economics, public policy) regarding pesticides, and identifies gaps for future research.

The purpose of this paper is to explore the correction mechanism of resilient safety culture on new generation of construction workers (NGCWs)' unsafe behavior and test the multiple mediation effects of job crafting and perceived work meaningfulness based on the context of Chinese construction industry in order to find a new way to effectively correct the NGCWs' unsafe behavior.

A theoretical model of correction mechanism was established based on literature research and theoretical deduction. An empirical study was employed based on confirmatory factor analysis and regression analysis with a sample of 404 NGCWs in China.

The results indicated that resilient safety culture can effectively correct NGCWs' unsafe behavior through job crafting and perceived work meaningfulness. Job crafting and perceived work meaningfulness can play independent and serial mediating roles between resilient safety culture and unsafe behavior.

Research results only represent a short-term law about the correction mechanism of NGCWs' unsafe behavior based on a questionnaire study from China's construction industry. It is necessary to continue to implement a longitudinal study to test it in a relatively long period in future research. The findings also need to be verified based on the young construction workers in other countries.

This study provides a theoretical basis and feasible management reference for construction enterprises in China to correct NGCWs' unsafe behavior from the perspective of resilient safety culture. Furthermore, the construction of resilient safety culture in construction enterprises can help NGCWs better carry out job crafting and perceive the meaning of work.

This paper clarifies the correction mechanism of resilient safety culture on unsafe behavior of NGCWs, and further tests the independent mediating roles and a serial mediating role of job crafting and perceived work meaningfulness between resilient safety culture and unsafe behavior, which fills the research gap about the influence mechanism of resilient safety culture on young construction workers' unsafe behavior and enriches the theoretical system of unsafe behavior correction of construction workers.

Based on goal content theory (GCT), this study examines the associations between different work goal contents (intrinsic and extrinsic goals) and early retirement intentions and reveals the underlying mechanisms of abovementioned relations.

The paper tested the proposed model by using a sample of 265 workers in China using a two-wave survey.

Findings(1) employees' intrinsic and extrinsic goals are both negatively related to early retirement intentions, and the effect of extrinsic goals on early retirement intentions is more significant. (2) Work passion was found to be a strong mediator between work goal content and employees' early retirement intentions. (3) Human resource (HR) practices’ flexibility significantly moderates the relationship between work passion and early retirement intentions.

The contribution of the current study is that this study first takes into account individuals’ psychological and organizational factors, aiming to reveal the differential effect of different work goals on individuals' early retirement intentions as well as the mediating effect of work passion and the moderating effect of HR practices’ flexibility in the abovementioned relations.

The purpose of this paper is to accurately obtain the deformation of a hybrid robot and rapidly enable real-time compensation in friction stir welding (FSW). In this paper, a prediction algorithm based on the back-propagation neural network (BPNN) optimized by the adaptive genetic algorithm (GA) is presented.

Via the algorithm, the deformations of a five-degree-of-freedom (5-DOF) hybrid robot TriMule800 at a limited number of positions are taken as the training set. The current position of the robot and the axial force it is subjected to are used as the input; the deformation of the robot is taken as the output to construct a BPNN; and an adaptive GA is adopted to optimize the weights and thresholds of the BPNN.

This algorithm can quickly predict the deformation of a robot at any point in the workspace. In this study, a force-deformation experiment bench is built, and the experiment proves that the correspondence between the simulated and actual deformations is as high as 98%; therefore, the simulation data can be used as the actual deformation. Finally, 40 sets of data are taken as examples for the prediction, the errors of predicted and simulated deformations are calculated and the accuracy of the prediction algorithm is verified.

The entire algorithm is verified by the laboratory-developed 5-DOF hybrid robot, and it can be applied to other hybrid robots as well.

Robots have been widely used in FSW. Traditional series robots cannot bear the large axial force during welding, and the deformation of the robot will affect the machining quality. In some research studies, hybrid robots have been used in FSW. However, the deformation of a hybrid robot in thick-plate welding applications cannot be ignored. Presently, there is no research on the deformation of hybrid robots in FSW, let alone the analysis and prediction of their deformation. This research provides a feasible methodology for analysing the deformation and compensation of hybrid robots in FSW. This makes it possible to calculate the deformation of the hybrid robot in FSW without external sensors.

Purpose – The author examines the implementation and characteristics of teacher evaluation and explores their associations with improvement in teachers’ practice of constructivist instruction.Methodology – This quantitative study uses statewide longitudinal Teachers’ Opportunity to Learn survey data collected in 2009 and 2010 from middle school mathematics teachers in Missouri and estimates a series of value-added models with two-level Hierarchical Linear Modeling.Findings – Teachers in this study were mainly evaluated by principals who conducted classroom observations and held face-to-face meetings to evaluate teaching practice and professional development activities. The study provides empirical evidence and support for the use of multiple evaluators with multiple evaluation data and outcomes in teacher evaluation. Additionally, it highlights the potential benefits of focusing on teachers’ instructional data instead of student achievement in teacher evaluation in order to improve their teaching practice.Research limitations – This study focused on middle school mathematics teachers in a single state in the United States. Whether these findings can be generalized to teachers of other subject areas or grades, or to states with different policy contexts, or to countries with country-specific structural, cultural, and social differences is unknown.Value – This study is the first effort to systematically examine teacher evaluation practices across a single state and provide empirical evidence on the relationships between the implementation characteristics of teacher evaluation and improvement in teachers’ instructional practice. Findings of this study provide school, district, state, federal, and international policymakers and administrators with important, up-to-date information on teacher evaluation at the middle-school level in the United States.

The utilisation of building information modelling (BIM) technology is rapidly increasing among construction professionals across the world. Notwithstanding, recent studies revealed a low level of BIM implementation in the context of the Nigerian construction sector. Moreover, previous studies have established that BIM application comes with its share of various barriers. Therefore, this study aims to carry out an on-site survey on barriers to the application of BIM on construction sites in the Nigerian construction industry.

An extensive review of literature on BIM barriers was conducted, from where 33 factors were identified as significant BIM barriers peculiar to the developing countries. A questionnaire was developed and distributed to the targeted respondents, who are practicing professionals in the Nigerian construction industry, based on the identified barriers. The data collected were analysed by using both descriptive and inferential statistics.

The principal component analysis revealed that 27 barriers were peculiar to the Nigerian construction industry. The “lack of familiarity with BIM capacity, habitual resistance to change from the traditional style of design and build, and poor awareness of BIM benefit” were identified as the three most critical barriers hindering BIM application on construction sites in the Nigerian construction industry.

This study reveals key information on the peculiar barriers to BIM application in the Nigerian construction industry. The avoidance of these barriers will not only assist various construction stakeholders in the successful implementation of BIM application on a construction project but also promote information management systems and productivity within the construction industry to a great extent. These will further improve post-construction activities.

This study provides a substantial understanding of BIM state of the art in the context of barriers hindering BIM application on construction sites in the Nigerian construction industry.