Search results

This paper aims to present a multi-scale stochastic damage model (SDM) for concrete and apply it to the stochastic response analysis of reinforced concrete shear wall structures.

The proposed SDM is constructed at two scales, i.e. the macro-scale and the micro-scale. The general framework of the SDM is established on the basis of the continuum damage mechanics (CDM) at the macro-scale, whereas the detailed damage evolution is determined through a parallel fiber buddle model at the micro-scale. The parallel buddle model is made up of micro-elements with stochastic fracture strains, and a one-dimensional random field is assumed for the fracture strain distribution. To represent the random field, a random functional method is adopted to quantify the stochastic damage evolution process with only two variables; thus, the numerical efficiency is greatly enhanced. Meanwhile, the probability density evolution method (PDEM) is introduced for the structural stochastic response analysis.

By combing the SDM and PDEM, the probabilistic analysis of a shear wall structure is performed. The mean value, standard deviation and the probability density function of the shear wall responses, e.g., shear capacity, accumulated energy consumption and damage evolution, are obtained.

It is noted that the proposed method can reflect the influences of randomness from material level to structural level, and is efficient for stochastic response determination of shear wall structures.

The purpose of this paper is to investigate transformational, ambidextrous, and transactional leadership and their relationship to employee creativity and the extent to which psychological empowerment and promotion focus are consistent with previous studies that identify their significant impact on employee creativity. In addition, employee psychological empowerment and promotion focus are used as mediators in the research model to ascertain whether or not there is a significant mediating effect between transformational leadership, ambidextrous leadership, transactional leadership and employee creativity.

In the study, 500 questionnaires were mailed to 50 electronics companies in China; 427 valid questionnaires were eventually collected. A structural equation model was then used for data analysis to study the causalities between all the parameters.

The research findings indicate that transformational and ambidextrous leadership styles have a significant effect on employee creativity. In addition, the study found that employee psychological empowerment and promotion focus has a significant mediating effect for transformational leadership, ambidextrous leadership, transactional leadership and employee creativity.

Executives who adopt a transformational or ambidextrous leadership style tend to have employees with greater psychological empowerment, while transformational or ambidextrous leaders tend to have employees with a stronger promotion focus. Further, the study discovered that when executives adopt a transformational or ambidextrous leadership style, they can use their employees’ psychological empowerment and promotion focus to improve employee creativity.

The purpose of this paper is to develop a mediation model for understanding how favoritism, in the context of the leader–member exchange (LMX) theory, influences subordinate-rated LMX via the subordinates’ perception of organizational justice.

The sample comprised 39 managers and 159 employees working in local branches of banks in Taiwan. While the managers were asked to rate their LMX scores with all employees, three to five employees were randomly selected to participate in a survey which included two phases with a time lag of three months. Given the nested structure of the data, hierarchical linear modeling was used to examine the mediation model.

The findings support the mediation model, indicating that LMX favoritism can significantly influence subordinate-rated LMX by enhancing subordinates’ justice perception.

The study contributes to the existing LMX research by showing that a superior’s LMX favoritism may change subordinate-rated LMX over time.

This study aims to explore which relational factors are crucial for accelerator-based start-ups to achieve high financial performance and whether innovation levels influence this relationship. Utilizing fsQCA and drawing from the resource-based view (RBV), we analyze 128 start-ups in a Spanish accelerator, split by innovativeness, to understand the impact of relational and human capital factors on performance.

The study uses fuzzy-set qualitative comparative analysis (fsQCA) to investigate conditions leading to high financial performance among 128 start-ups in a Spanish accelerator, divided by innovativeness. Four key factors are analyzed: social capital, social competence, resource mobilization and entrepreneurial ecosystem support. fsQCA examines complex relationships between these factors and financial performance.

Relational and human capital factors significantly impact start-up financial performance, varying with innovativeness. Highly innovative start-ups benefit from social competence and networked support, while less innovative but profitable start-ups rely on resource mobilization skills. The study highlights the contingent value of these factors, showing that unique configurations drive financial success.

The paper enhances the RBV in entrepreneurial contexts by highlighting the critical role of relational resources and their configurations. It suggests social competence and networked support are crucial for highly innovative start-ups, while resource mobilization is key for less innovative ones. These findings encourage nuanced theorizing of start-up success strategies, considering varying innovativeness levels and their impact on performance.

This study enhances understanding of the relationship between relational factors and financial performance in accelerator-based start-ups, considering innovation levels. It provides insights into how different configurations of social capital, competence, resource mobilization and ecosystem support lead to success. It underscores the importance of considering the contingent value of relational factors for start-up growth.

Gender difference exists in the perception of the patient safety culture in healthcare organizations. A case from a medical center in Taiwan is presented to examine how different genders perceive the patient safety culture in practice from 2014 to 2017.

A longitudinal study using the data from 2014 to 2017 is conducted quantitatively. Mann–Whitney U test and one-way analysis of variance are employed for analyses.

The results showed that female nurses had significantly higher emotional exhaustion than male nurses in 2015 and 2016 indicating male nurses had better fatigue recovery than their female counterparts. In addition, male nurses felt a higher degree of fatigue in 2016 and 2017 than those in 2015 statistically. In contrast, female nurses felt more stressful in 2016 and 2017 than those in 2014 statistically. Female nurses had higher emotional exhaustion in 2016 and 2017 than those in 2014 and 2015 statistically.

To sum up, female nurses were more stressful than before, and their recovery was also relatively poor particularly in 2016 and 2017. There is a need to reduce the degree of fatigue for female nurses in this medical center through employee assistance programs, mindfulness-based stress reduction programs, building up female nurses' positive currency and setting up their appreciative inquiry. In contrast to female nurses, male nurses recovered better from fatigue. This might encourage hospital management to deploy male nurses more effectively in this medical center.

The results enable the hospital management to know there is a gender difference in this case hospital. More attention on female nurses is required.

The purpose of this study is to identify critical demographic variables that would significant influence each dimension of patient safety culture. Understanding nurses' attitudes toward patient safety is important for healthcare organizations to relentlessly improve medical quality and services for patients.

The internal survey data sets in 2015 and 2016 from nurses' viewpoints are used. Linear regression with forward selection is applied where nine demographic variables are the input variables, while each dimension of the Chinese version of safety attitudes questionnaire (SAQ) is the dependent variable.

Supervisor/manager is the most essential demographic variable that has significant impacts on six dimensions. Experience in organization is the other critical demographic variable.

Nurses who are in charge of supervisors/managers are more satisfied in six of eight dimensions. Nurses who have much experience in an organization tend to have less satisfaction in three dimensions. Therefore, hospital management should enhance the leader's effectiveness in engaging their subordinates' commitment.

The results enable the hospital management to pay much attention to two major demographic variables, namely supervisor/manager and experience in organization, in order to improve the patient safety culture based on the Chinese version of SAQ in this hospital. Moreover, supervisor/manager is a more critical demographic variable for nurses due to larger absolute values of standardized coefficients by linear regression with forward selection.

This study aims to study the dynamic characteristics of a helical geared rotor-bearing system with composite material rotating shafts.

A finite element model of a helical geared rotor-bearing system with composite material rotating shafts is developed, in which the rotating shafts of the system are composed of composite material and modeled as Timoshenko beam; a rigid mass is used to represent the gear and their gyroscopic effect is taken into account; bearings are modeled as linear spring-damper; and the equations of motion are obtained by applying Lagrange’s equation. Natural frequencies, mode description, lateral responses, axial responses, lamination angles, lamination numbers, gear mesh stiffness and bearing damping coefficients are investigated.

The desired mechanical properties could be constructed using different lamination numbers and fiber included angles by composite rotating shafts. The frequency of the lateral module decreases as the included angle of the fibers and the principal shaft of the composite material rotating shaft increase. Because of the gear mesh stiffness increase, the resonance frequency of the coupling module of the system decreases, the lateral module is not influenced and the steady-state response decreases. The amplitude of the steady-state lateral and axial responses gradually decreases as the bearing damping coefficient increases.

The model of a helical geared rotor-bearing system with composite material rotating shafts is established in this paper. The dynamic characteristics of a helical geared rotor-bearing system with composite rotating shafts are investigated. The numerical results of this study can be used as a reference for subsequent personnel research.

The dynamic characteristics of the geared rotor-bearing system had been reported in some literature. However, the dynamic analysis of a helical geared rotor-bearing system with composite material rotating shafts is still rarely investigated. This paper shows some novel results of lateral and axial response results obtained by different lamination angles and different lamination numbers. In the future, it makes valuable contributions for further development of dynamic analysis of a helical geared rotor-bearing system with composite material rotating shafts.

The disbonding of DLC coating is a main failure mode in the high-speed cavitation condition, which shortens the service life of the bearing. This study aims to investigate influence of adhesion strength on cavitation erosion resistance of DLC coating.

Three DLC coatings with different adhesion strengths were grown on the 304 steel surfaces by using a cathodic arc plasma deposition method. Cavitation tests were performed by using a vibratory test rig to investigate the influence of adhesion strength on cavitation erosion resistance of a DLC coating. The cavitation mechanism of the substrate-coating systems was further discussed by means of surface analyses.

The results indicated that, the residual stress decreased and then increased with the increasing DLC coating thickness from 1 µm to 2.9 µm, and the lower residual stress can improve the adhesion strength of the DLC coating to the substrate. It was also concluded that, the plastic deformation as well as the fracture occurred on the DLC coating surface at the same time, owing to higher residual stress and poorer adhesion strength. However, lower residual stress and better adhesion strength could help resist the occurrence of the coating fracture.

Cavitation tests were performed by using a vibratory test rig to investigate the influence of adhesion strength on cavitation erosion resistance of the DLC coating. The plastic deformation and the fracture occurred on the DLC coating surface at the same time, owing to higher residual stress and poorer adhesion of coating. Lower residual stress and better adhesion of coating could resist the occurrence of the DLC coating fracture.

In high-temperature regions (tropical regions) temperatures rises in summer, which affects the performance of asphalt pavement. Therefore, we must consider the conditions of asphalt pavement, especially in these regions. This study aims to investigate the influence of high temperature on the stability performance of high-density polyethylene (HDPE) and crumb rubber powder (CRP) modified hot mix asphalt (HMA) using Marshall design parameters and rutting test.

In this study, three HMA mixtures with 4 per cent HDPE and 15 per cent CRP, 5 per cent HDPE and 10 per cent CRP, and 6 per cent HDPE and 5 per cent CRP concentrations were used for the Marshall stability test and dynamic stability (rutting test) at 60-75°C, and water stability test at 60°C.

The results showed that when test temperature was increased from 60°C to 75°C, the Marshall stability and dynamic stability of three HDPE- and CRP-modified HMA mixtures decreased, and these three HDPE- and CRP-modified HMA mixtures have a good moisture damage resistance. Of the three HMA mixtures with different HDPE and CRP concentrations, HMA mixtures with 5 per cent HDPE and 10 per cent CRP concentration exhibit optimal Marshall stability, dynamic stability and water stability.

This study showed the effects of high-temperatures changes on the stability performance of HDPE- and CRP-modified HMA mixtures.

Cavitation bubbles cannot be avoided in the hydraulic system. Because of instability of flow and variation of water pressure, the jet often occurs in a bubble collapse. This study aims to accurately predict the shape, velocity and time of the resulting jet, so as to inhibit cavitation erosion.

In the study, a theoretical model of cavitation bubbles in the water has been developed by applying a periodic water film pressure into the Rayleigh–Plesset equation. A fourth-order in time Runge–Kutta scheme is used to obtain an accurate computation of the bubble dynamic characteristics. The behavior of the proposed theory is further simulated in a high-speed photography experiment by using a cavitation bubble test rig. The evolution with time of cavitation bubbles is further obtained.

A comparison with the available experimental results reveals that the bubble evolution with time has a duration of about 0.3T0, that well predicts the expanding and compressing process of cavitation bubbles. The results also show that the initial bubble radius in the water influences the moving velocity of the bubble wall, whereas the perturbation frequency of the water pressure has less effect on the velocity of the bubble wall.

A theoretical model well predicts dynamic characteristics of cavitation bubbles. The bubble evolution with time has a duration of about 0.3T0, Initial bubble radius influences the velocity of bubble wall. Perturbation frequency has less effect on the velocity of bubble wall.