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This paper aims to describe a three-dimensional mathematical and numerical model based on finite volume method to simulate the fluid dynamics in weld pool, droplet transfer and keyhole behaviors in the laser-MIG hybrid welding process of Fe36Ni Invar alloy.

Double-ellipsoidal heat source model and adaptive Gauss rotary body heat source model were used to describe electric arc and laser beam heat source, respectively. Besides, recoil pressure, electromagnetic force, Marangoni force, buoyancy as well as liquid material flow through a porous medium and the heat, mass, momentum transfer because of droplets were taken into consideration in the computational model.

The results of computer simulation, including temperature field in welded plate and velocity field in the fusion zone were presented in this article on the basis of the solution of mass, momentum and energy conservation equations. The correctness of elaborated models was validated by experimental results and this proposed model exhibited close correspondence with the experimental results with respect to weld geometry.

It lays foundation for understanding the physical phenomena accompanying hybrid welding and optimizing the process parameters for laser-MIG hybrid welding of Invar alloy.

The purpose of this study which resulted in this work is to propose an optimization method of sensors distribution for structural impact localization.

This paper presents a multi-objective optimization study of a novel sensors distribution technique, where two optimization objective functions are considered: sensors number and sensors location optimization performance index. In addition, the finite element analysis, the time-frequency transform and the principal component analysis are combined to quantize the above objective functions. The non-dominated sorting genetic algorithm II (NSGA-II) is used to acquire Pareto solutions.

The effectiveness of this method is validated through a prototype laboratory called the piezoelectric intelligent structure where promising results are obtained.

An optimization method of this novel sensors distribution technique is built and produced a set of efficiency solutions for the real-world problem of impact localization where two conflicting objectives are involved.

The purpose of this paper is to model the particle capture of elliptic magnetic matrices for parallel stream type high magnetic separation, which can be a guidance for the development of novel elliptic cylinder matrices for high-gradient magnetic separation (HGMS).

The magnetic field distribution around the elliptic matrices is investigated quantitatively and the magnetic field and gradient were calculated. The motion equations of the magnetic particles around the matrices were derived and the particle capture cross-section of elliptic matrices was studied and was compared with that of the conventional circular matrices.

Elliptic matrices can present larger particle capture cross-section than the conventional circular matrices and can be a kind of promising matrices to be applied to HGMS.

There is little literature investigating the magnetic characteristics and the particle capture of the elliptic matrices in HGMS, the study is of great significance for the development of novel elliptic magnetic matrices in HGMS.

The existing research rarely explains the value of authoritarian leadership in small- and medium-sized enterprises (SMEs). The purpose of this study is to explore how authoritarian leadership facilitates employee followership behaviors of the SMEs in China by considering the moderating effects of cooperative goal interdependence and leader behavioral integrity.

This research tested hypotheses with a two-wave survey from a sample of 258 respondents from SMEs in China. Hypotheses are tested using hierarchical regression analyses.

Findings of the study have indicated the instrumental function of authoritarian leadership in facilitating employee followership behavior in SMEs. In particular, this study shows that the influence of authoritarian leadership on followership behavior was positively related when employees have high cooperative goal interdependence with authoritarian leaders, and when employees perceive a leader's high behavioral integrity.

The study will help SMEs to understand that authoritarian leadership should seek optimal levels of cooperative goals with employees and integrate achievement goals into their career development strategy to enhance their followership behavior. In addition, authoritarian leadership should strive to take actions consistent with their words to guarantee the relationship between achieving goals and sharing mutual goals with employees.

The study contributes to the literature by addressing an important yet under-researched area, i.e. the effectiveness of authoritarian leadership in SMEs. Authoritarian leadership, a demanding and controlling leadership style, is often criticized by scholars. This study elaborates on a three-way interaction implied by self-determination theory in predicting followership behavior. It specifies the different roles of two situational factors (cooperative goal interdependence and leader behavior integrity) in affecting employees' followership behavior.

This paper aims to identify important factors in green public procurement (GPP) implementation and then to clarify how these factors affect GPP implementation.

The authors applied the Delphi method first and then conducted a focused and constrained multiple case study at 18 government procurement centers across China.

The authors identified four clusters of factors for successful GPP implementation: more clear, consistent and operational policy goals; a nation-wide green procurement campaign to enhance social capital and cultural resources; promoting staff’s ethics, professionalism, capacity and knowledge; and establishing checks and balances among organizations involved in the whole purchasing process.

GPP can significantly improve environmental protection and sustainable development.

Based on key insights from systems theory and agency theory, the authors emphasize that GPP implementation must take down its own functional silos and adopt a process approach across organizational tiers to synchronize human resource based and inter-organizational capabilities into a unified whole through information sharing, communications and collaboration.

This paper aims to investigate effect of porous polystyrene microspheres encapsulated inhibitor on the protection performance of epoxy resin coating.

Porous polystyrene (PS) microspheres were synthesized by soap-free emulsion polymerization. The morphology of microspheres was observed by scanning electron microscopy and transmission electron microscopy. Corrosion inhibitor benzotriazole was encapsulated into porous PS microspheres. The protection performance of epoxy resin coating with different contents of PS microspheres was tested by polarization curve.

The findings of electrochemical impedance spectroscopy and scanning vibrating electrode technique showed that addition of corrosion inhibitor to porous PS microspheres further improved the protection performance of the coatings.

Porous PS microspheres could be used as nanocontainer to encapsulate corrosion inhibitor.

Addition of porous PS microspheres with corrosion inhibitor improved the protection performance of the coatings.

This paper aims to explore the influences of different process parameters, including laser power, scanning speed, defocusing distance and scanning mode, on the shape features of molten pool and, based on the obtained relationship, realize the diagnosis of forming defects during the process.

Molten pool was captured on-line based on a coaxial CCD camera mounted on the welding head, then image processing algorithms were developed to obtain melt pool features that could reflect the forming status, and it suggested that the molten pool area was the most sensitive characteristic. The influence of the processing parameters such as laser power, traverse speed, powder feed rate, defocusing distance and the melt pool area was studied, and then the melt pool area was used as the characteristic to detect the forming defects during the cladding and additive manufacturing process.

The influences of different process parameters on molten pool area were explored. Based on the relationship, different types of defects were accurately detected through analyzing the relationship between the molten pool area and time.

The findings would be helpful for the quality control of laser additive manufacturing.

Hand gesture-based interaction can provide far more intuitive, natural and immersive feelings for users to manipulate 3D objects for virtual assembly (VA). A mechanical assembly consists of mostly general-purpose machine elements or mechanical parts that can be defined into four types based on their geometric features and functionalities. For different types of machine elements, engineers formulate corresponding grasping gestures based on their domain knowledge or customs for ease of assembly. Therefore, this paper aims to support a virtual hand to assemble mechanical parts.

It proposes a novel glove-based virtual hand grasping approach for virtual mechanical assembly. The kinematic model of virtual hand is set up first by analyzing the hand structure and possible movements, and then four types of grasping gestures are defined with joint angles of fingers for connectors and three types of parts, respectively. The recognition of virtual hand grasping is developed based on collision detection and gesture matching. Moreover, stable grasping conditions are discussed.

A prototype system is designed and developed to implement the proposed approach. The case study on VA of a two-stage gear reducer demonstrates the functionality of the system. From the users’ feedback, it is found that more natural and stable hand grasping interaction for VA of mechanical parts can be achieved.

It proposes a novel glove-based virtual hand grasping approach for virtual mechanical assembly.

This paper aims to investigate the electrochemical corrosion behavior of a five-layer Al alloy composites (4343/4047/3003/4047/4343) with a thickness of 0.2 mm in NaCl solution.

Electrochemical impedance spectroscopy, polarization curve and morphology analyses were used to study the corrosion behavior of the Al alloy composites from cross-sectional and plane directions.

The corrosion resistance of the surface from the plane direction was higher than that from the cross sections. Si-enrich particles were observed in the outer 4047/4343 layer, and AlFeCuMnBi phases were identified in the core 3003 layer. The galvanic coupling between the Si-enrich particle and the Al matrix accelerated the dissolution Al matrix.

This work lays the experimental foundation for corrosion mechanism of the Al alloy composite plate.

This paper analyzes the impact of economic downturns on the revenue and expense sides of city financing for the period 2003 to 2009 using a convenience sample of the audited end of year financial reports for thirty midsized US cities. The analysis focuses on whether and how quickly and how extensively revenue and spending directions from past years are altered by recessions. A seven year series of Comprehensive Annual Financial Report (CAFR) data serves to explore whether citiesʼ revenues and spending, especially the traditional property tax and core functions such as public safety and infrastructure withstood the brief 2001 and the persistent 2007 recessions? The findings point to consumption (spending) over stability (revenue minus expense) for the recession of 2007, particularly in 2008 and 2009.