Search results

Project scheduling plays an essential role in the implementation of a project due to the limitation of resources in practical projects. However, the existing research tend to focus on finding suitable algorithms to solve various scheduling problems and fail to find the potential scheduling rules in these optimal or near-optimal solutions, that is, the possible intrinsic relationships between attributes related to the scheduling of activity sequences. Data mining (DM) is used to analyze and interpret data to obtain valuable information stored in large-scale data. The goal of this paper is to use DM to discover scheduling concepts and obtain a set of rules that approximate effective solutions to resource-constrained project scheduling problems. These rules do not require any search and simulation, which have extremely low time complexity and support real-time decision-making to improve planning/scheduling.

The resource-constrained project scheduling problem can be described as scheduling a group of interrelated activities to optimize the project completion time and other objectives while satisfying the activity priority relationship and resource constraints. This paper proposes a new approach to solve the resource-constrained project scheduling problem by combining DM technology and the genetic algorithm (GA). More specifically, the GA is used to generate various optimal project scheduling schemes, after that C4.5 decision tree (DT) is adopted to obtain valuable knowledge from these schemes for further predicting and solving new scheduling problems.

In this study, the authors use GA and DM technology to analyze and extract knowledge from a large number of scheduling schemes, and determine the scheduling rule set to minimize the completion time. In order to verify the application effect of the proposed DT classification model, the J30, J60 and J120 datasets in PSPLIB are used to test the validity of the scheduling rules. The results show that DT can readily duplicate the excellent performance of GA for scheduling problems of different scales. In addition, the DT prediction model developed in this study is applied to a high-rise residential project consisting of 117 activities. The results show that compared with the completion time obtained by GA, the DT model can realize rapid adjustment of project scheduling problem to deal with the dynamic environment interference. In a word, the data-based approach is feasible, practical and effective. It not only captures the knowledge contained in the known optimal scheduling schemes, but also helps to provide a flexible scheduling decision-making approach for project implementation.

This paper proposes a novel knowledge-based project scheduling approach. In previous studies, intelligent optimization algorithm is often used to solve the project scheduling problem. However, although these intelligent optimization algorithms can generate a set of effective solutions for problem instances, they are unable to explain the process of decision-making, nor can they identify the characteristics of good scheduling decisions generated by the optimization process. Moreover, their calculation is slow and complex, which is not suitable for planning and scheduling complex projects. In this study, the set of effective solutions of problem instances is taken as the training dataset of DM algorithm, and the extracted scheduling rules can provide the prediction and solution of new scheduling problems. The proposed method focuses on identifying the key parameters of a specific dynamic scheduling environment, which can not only reproduces the scheduling performance of the original algorithm well, but also has the ability to make decisions quickly under the dynamic interference construction scenario. It is helpful for project managers to implement quick decisions in response to construction emergencies, which is of great practical significance for improving the flexibility and efficiency of construction projects.

This study aims to build a framework of the influencing factors of construction workers' career promotion and identifies the critical determinants so as to propose suggestions for the government and enterprises to offer construction workers a path for career promotion.

In line with the theory of human resources, such as Herzberg's two-factor theory, this study constructs a theoretical framework that affects the career promotion of construction workers. Using evidence from Guangzhou city, valid data provided by 464 workers from 50 sites were collected by a questionnaire survey, and the significance test on the influencing factors of construction workers' career promotion was taken by binary logistic regression.

The overall career development of construction workers in Guangzhou is worrying. The binary logistic regression indicates that age, working years, type of work, career development awareness, legal awareness, professional mentality, vocational psychological training and career development path are critical factors that affect construction workers' career promotion.

This study for the first time explores the career promotion of frontline construction workers. Specifically, it identifies the critical factors that affect the career promotion of workers and thus lays a foundation for further research and the promotion and continuous and healthy development of the construction industry. Thus, this study is original and has theoretical and practical significance.

Public participation has been implemented with growing frequency as an instrument for dealing with the increased socio-economic and environmental disputes in public infrastructure and construction (PIC) projects in China. The purpose of this paper is to examine the perceptions of major stakeholders on the major aspects related to public participation practices in China's PIC projects and intends to convey what is presently happening in this segment of the construction industry.

Specific topics of the social effects, benefits, forms, and barriers were addressed through a recent survey of the major stakeholders involved in PIC projects. The survey results were used to perform a strength-weakness-opportunity-threat analysis for evaluating the status quo of public participation in PIC projects.

The survey results indicate that the development of public participation practices in China remains relatively slow despite the urgent need to promote this mechanism for solving socio-economic and environmental disputes in PIC projects. Thus, a four-step strategic plan is suggested to be established to overcome main barriers for the implementation of public participation and promote its development in China.

This study aims to evaluate the status quo of the public participation practices in China by conducting a national survey, which has never been conducted before. The findings of this paper provide a holistic view of the status quo of public participation in China's PIC projects and promote a better application of this mechanism in the construction industry.

To reduce the computational scale for quasi-magnetostatic problems, model order reduction is a good option. Reduced-order modelling techniques based on proper orthogonal decomposition (POD) and centroidal Voronoi tessellation (CVT) have been used to solve many engineering problems. The purpose of this paper is to investigate the computational principle, accuracy and efficiency of the POD-based and the CVT-based reduced-order method when dealing with quasi-magnetostatic problems.

The paper investigates computational features of the reduced-order method based on POD and CVT methods for quasi-magnetostatic problems. Firstly the construction method for the POD and the CVT reduced-order basis is introduced. Then, a reduced model is constructed using high-fidelity finite element solutions and a Galerkin projection. Finally, the transient quasi-magnetostatic problem of the TEAM 21^a model is studied with the proposed reduced-order method.

For the TEAM 21^a model, the numerical results show that both POD-based and CVT-based reduced-order approaches can greatly reduce the computational time compared with the full-order finite element method. And the results obtained from both reduced-order models are in good agreement with the results obtained from the full-order model, while the computational accuracy of the POD-based reduced-order model is a little higher than the CVT-based reduced-order model.

The CVT method is introduced to construct the reduced-order model for a quasi-magnetostatic problem. The computational accuracy and efficiency of the presented approaches are compared.

The purpose of this paper is to present a crack initiation mechanism of the external hydrogen effect on type 304 stainless steel, as well as on fatigue crack propagation in the presence of hydrogen gas.

The effects of external hydrogen on hydrogen-assisted crack initiation in type 304 stainless steel were discussed by performing fatigue crack growth rate and fatigue life tests in 5 MPa argon and hydrogen.

Hydrogen can reduce the incubation period of fatigue crack initiation of smooth fatigue specimens and greatly promote the fatigue crack growth rate during the subsequent fatigue cycle. During the fatigue cycle, hydrogen invades into matrix through the intrusion and extrusion and segregates at the boundaries of α′ martensite and austenite. As the fatigue cycle increased, hydrogen-induced cracks would initiate along the slip bands. The crack initiation progress would greatly accelerate in the presence of hydrogen.

To the best of the authors’ knowledge, this paper is an original work carried out by the authors on the hydrogen environment embrittlement of type 304 stainless steel. The effects of external hydrogen and argon were compared to provide understanding on the hydrogen-assisted crack initiation behaviors during cycle loading.

The car-sharing market has entered the mature stage, and consumers' demand shows a diversified increasing trend. This paper considers two modes of operation and two pricing strategies, which are business-to-consumer and consumer-to-consumer modes, market pricing and platform pricing. Under these conditions, the platform's revenue-sharing ratio will be different. The purpose of this paper is to explore this research question, and seeks an optimal pricing mechanism that can achieve a win–win situation between platform and automobile manufacturer in the two market modes.

The authors design different profit functions for platform under the two contexts. Of course, the platform's function is constrained to the manufacturer's function. By introducing a revenue-sharing contract a Stackelberg game model dominated by the platform is established and the equilibrium solutions under the two pricing models are derived.

The study found that even if only market pricing is executed, the scale of the car-sharing market will continue to expand. As the car-sharing market becomes more saturated, platform pricing is better for the automobile manufacturer; in most cases, the platform prefers platform pricing, but when the number of private cars is relatively small, if the cost of car operation and maintenance for the automobile manufacturer is lower or the revenue-sharing ratio of private cars is high, then market pricing will be more favorable to the platform.

With the cross-border integration of car service platforms and the automobile manufacturing industry, the key to achieving win–win cooperation and sustainable development in the car-sharing market will converge on the question of how to design a suitable pricing mechanism and revenue-sharing method.

Authors have determined how a car-sharing platform achieves a win–win order pricing strategy with the manufacturer and private car owners, respectively. And authors combined the supply chain revenue-sharing contract with the car-sharing market to explore the application of the revenue-sharing contract in the sharing economy.

A direct and unified approach is proposed toward simultaneously simulating large strain elastic behaviors of gellan gels with different gellan polymer concentrations. The purpose of this paper is to construct an elastic potential with certain parameters of direct physical meanings, based on well-designed invariants of Hencky’s logarithmic strain.

For each given value of the concentration, the values of the parameters incorporated may be determined in the sense of achieving accurate agreement with large strain uniaxial extension and compression data. By means of a new interpolating technique, each parameter as a function of the concentration is then obtained from a given set of parameter values for certain concentration values.

Then, the effects of gellan polymer concentrations on large strain elastic behaviors of gellan gels are studied in demonstrating how each parameter relies on the concentration. Plane-strain (simple shear) responses are also presented for gellan gels with different polymer concentrations.

A direct, unified approach was proposed toward achieving a simultaneous simulation of large elastic strain behaviors of gellan gels for different gellan polymer concentrations. Each parameter incorporated in the proposed elastic potential will be derived as a function of the polymer concentration in an explicit form, in the very sense of simultaneously simulating large strain data for different concentrations.

The purposes of this paper include studying the friction coefficient of polyoxymethylene (POM) under a broad range of normal load and sliding velocity; developing a mathematical model of friction coefficient of POM under a broad range of normal loads and sliding velocities; and applying the model to dynamic finite element (FE) analysis of mechanical devices containing POM components.

Through pin-on-disc experiment, the friction coefficient of POM in different normal loads and sliding velocities is investigated; the average contact pressure is between 5 and 15 Mpa and the sliding velocity is from 0.05 to 0.9 m/s. A friction algorithm is developed and embedded in the FE model to simulate the friction of POM in different normal loads and sliding velocities.

The friction coefficient of POM against steel declines with the increase of normal loads when the contact pressure is between 5 and 15 Mpa. The friction coefficient of POM against steel increases markedly when the sliding velocity is between 0.05 and 0.15 m/s, it decreases sharply between 0.15-0.45 m/s and then it stabilizes at high sliding velocity between 0.45 and 0.9 m/s. The friction coefficient of POM in different working operations has a significant effect on contact stress and shear stress. The simulation data and experiment data of POM friction force fit very well; therefore, it can be concluded that the friction algorithm and FE model are accurate.

The friction coefficient of POM under a broad range of normal loads and sliding velocities is investigated. The friction coefficient model of POM is established as a function of normal loads and sliding velocities in the dry sliding condition. A friction algorithm is developed and embedded in the FE model of the friction of POM. The mathematical model of the friction coefficient accurately agrees with the experiment data, and simulation data and experiment data of the POM friction force fit very well.

This paper aims to reduce environment pollution caused by benzotriazole. The authors chose one of the best inhibitors from 2-aminobenzimidazole, 2-methylbenzimidazol, 2-mercaptobenzimidazole and benzimidazole in combination with benzotriazole.

The electrochemical measurement indicated that 2-methylbenzimidazol had the best inhibition behavior. Then, it was mixed with benzotriazole. Techniques such as field emission scanning electron microscopy, atomic force microscopy, Raman spectroscopy and optical contact angle measurements were used.

The results showed that the inhibition efficiency was up to 99.98%, when the mixture concentration was 20 mmol/L and the molar ratio 1:1.

1-benzotriazole was mixed with 2-methylbenzimidazol for the first time. During the exist of methyl, 2-methylbenzimidazol has the better inhibition; this point was ignored by researchers.

Career plateau is a major concern for many seasoned employees because they often stay in the same position longer than expected and over time begin to lack job challenges. This phenomenon is now considered a normal stage in career development. The purpose of this study is to test the effects of two types of career plateau: hierarchical and job content on career commitment (career identity, career insight and career resilience), along with the mediating effect of perceived external employability. We also determined in the moderated mediation model if Super's (1957) three career stages amplify and attenuate the indirect effect of hierarchical/job content plateau on career commitment (career identity, career insight, career resilience) via perceived external employability.

We tested the hypotheses with survey data collected from a convenience sample of 472 white-collar full-time employees who also studied in the MBA and continuing education program in five large universities in Taiwan (77% return rate).

The mediation model result showed that perceived external employability partially and negatively mediated the influence of hierarchical plateaus on career commitment (career identity, career insight and career resilience). Perceived external employability partially and negatively mediated the influence of job content plateaus on career identity and career insight but fully and negatively mediated on career resilience. The result of the moderated mediation model also demonstrated that only employees in the trial stage had influences on the mediation relationships among the hierarchical plateau, perceived external employability and career commitment with its two dimensions of career identity and career insight only other than those in the stabilization and maintenance stages.

The findings of this study can benefit career management scholars and practitioners since they promote a better understanding of the career management practices that are relevant for seasoned employees who are valued for their knowledge, experience and expertise when encountering the three career stages.

Drawing on the conservation of resources (COR) theoretical perspective, we fill the gap in the literature by proposing perceived external employability as a mediator in the link between career plateau and career commitment and generalize the results to plateaued employees at the different career stages.