Search results

During the construction process of the China Railway Track System (CRTS) I type filling layer, the nonwoven fabric bags have been used as grouting templates for cement asphalt (CA) emulsified mortar. The porous structure of nonwoven fabrics endowed the templates with breathability and water permeability. The standard requires that the volume expansion rate of CA mortar must be controlled within 1%–3%, which can generate expansion pressure to ensure that the cavities under track slabs are filled fully. However, the expansion pressure caused some of the water to seep out from the periphery of the filling bag, and it would affect the actual mix proportion of CA mortar. The differences in physical and mechanical properties between the CA mortar under track slabs and the CA mortar formed in the laboratory were studied in this paper. The relevant results could provide important methods for the research of filling layer materials for CRTS I type and other types of ballastless tracks in China.

During the inspection of filling layer, the samples of CA mortar from different working conditions and raw materials were taken by uncovering the track slabs and drilling cores. The physical and mechanical properties of CA mortar under the filling layer of the slab were systematically analyzed by testing the electrical flux, compressive strength and density of mortar in different parts of the filling layer.

In this paper, the electric flux, the physical properties and mechanical properties of different parts of CA mortar under the track slab were investigated. The results showed that the density, electric flux and compressive strength of CA mortar were affected by the composition of raw materials for dry powders and different parts of the filling layer. In addition, the electrical flux of CA mortar gradually decreased within 90 days’ age. The electrical flux of samples with the thickness of 54 mm was lower than 500 C. Therefore, the impermeability and durability of CA mortar could be improved by increasing the thickness of filling layer. Besides, the results showed that the compressive strength of CA mortar increased, while the density and electric flux decreased gradually, with the prolongation of hardening time.

During 90 days' age, the electrical flux of the CA mortar gradually decreased with the increase of specimen thickness and the electrical flux of the specimens with the thickness of 54 mm was lower than 500 C. The impermeability and durability of the CA mortar could be improved by increasing the thickness of filling layer. The proposed method can provide reference for the further development and improvement of CRTS I and CRTS II type ballastless track in China.

The construction of cement asphalt (CA) emulsified mortar can obviously disturb the slab status after the fine adjustment. To decrease or eliminate the influence of CA mortar grouting on track slab geometry status, the effects of grouting funnel, slab pressing method, mortar expansion ratio, seepage ratio and grouting area on China Railway Track System Type (CRTS I) track slab geometry status were discussed in this paper.

Combined with engineering practice, this paper studied the expansion law of filling layer mortar, the liquid level height of the filling funnel, the pressure plate device and the amount of exudation water and systematically analyzed the influence of filling layer mortar construction on the state of track slab. Relevant precautions and countermeasures were put forward.

The results showed that the track slab floating values of four corners were different with the CA mortar grouting and the track slab corner near CA mortar grouting hole had the maximum floating values. The anti-floating effect of “7” shaped slab pressing device was more efficient than fixed-joint angle iron, and the slab floating value could be further decreased by increasing the amount of “7” shaped slab pressing devices. After CA mortar grouting, the track slab floating pattern had a close correlation with the expansion rate and water seepage rate of CA mortar over time and the expansion and water seepage rate of the mortar were faster when the temperature was high. Furthermore, the use of strip CA mortar filling under the rail bearing platform on both sides could effectively reduce the float under the track slab, and it could also save mortar consumption and reduce costs.

This study plays an important role in controlling the floating values, CA mortar dosage and the building cost of projects by grouting CA mortar at two flanks of filling space. The research results have guiding significance for the design and construction of China's CRTS I, CRTS II and CRTS III track slab.

This study examines the effect of cross-border network ties of returnee entrepreneurs on the foreign market diversity of their ventures. The study further investigates how two cross-cultural competencies (global mindset and cultural intelligence) moderate this effect.

A sample of 135 returnee entrepreneurial ventures from China was used to test the hypotheses.

This study finds that returnee entrepreneurs tend to enter into a wide range of culturally different country groups when returnee entrepreneurs have strong cross-border network ties. Moreover, global mindset and cultural intelligence function as complements in strengthening the effect of the cross-border network ties on foreign market diversity.

The authors contribute to both returnee entrepreneurship and foreign market entry literature in two ways. First, by examining the effect of cross-border network ties on foreign market entry, the authors add new and important insights into the role of social networks in the pre-internationalization phase. This is useful in understanding the internationalization process of new ventures founded by returnees, which have not been fully understood in returnee entrepreneurship literature. Second, by examining the moderating roles of global mindset and cultural intelligence, the authors enhance the understanding of the extent to which cross-border networks can be valuable in foreign market entry.

This study aimed to bibliometrically and visually analyze and review hospitality and tourism marketing studies published from 2000–2020.

A total of 3,942 articles collected from the databases of Social Science Citation Index (SSCI) and Science Citation Index Expanded (SCI-E) in the Web of Science (WoS) along with their references were used for analyses. The bibliometric software HistCiteTM and literature measurement visualization tools, VOSviewer and CiteSpace, were employed to analyze the selected articles.

The results of the study demonstrated top influential scholars and institutions, intellectual structure and emerging trends of the study topics, and future research opportunities in the field of hospitality and tourism marketing.

First, academic influence of a scholar was evaluated by citations of his/her publications, which did not take the order of authorship into consideration. Second, this study was restricted to the English language journals. Third, other types of published documents related to the studied field such as review papers were not considered by this research.

In comparison to traditional qualitative analysis such as content analysis, bibliometric analysis is a more objective approach to vividly demonstrate trends and performance of a research field, offers unique insights for its advancement with wider inclusiveness of a larger amount of data.

The purpose of this paper is to discriminate fake interference caused by polygonal approximation so as to achieve accurate assembly sequence planning and assembly simulation.

An approximation zone model is proposed to formulate polygonal approximation. Fake interference is discriminated from hard interference by evaluating if polygonal models intersect within corresponding approximation zones. To reduce the computation, the surface-surface, surface-end face and end face-end face intersection test methods have been developed to evaluate the intersection and obtain collision data. An updated collision detection algorithm with this method is presented, which is implemented by a system named AutoAssem.

This method has been applied to a set of products such as a valve for assembly interference matrix generation, static and dynamic collision detection. The results show that it ensures the accuracy of assembly sequence planning and assembly simulation for polygonal models.

This method facilitates assembly design in the virtual environment with polygonal models. It can also be applied to computer aided design systems to achieve quick and accurate collision detection.

Fake interference between polygonal models may result in serious errors in assembly sequence planning and assembly simulation. Assembly zone model and novel polygon intersection verification methods have been proposed to effectively tackle this problem. Compared to current methods, this method considers valid penetration direction and approximation difference, does not need to process complicated auxiliary data and can be easily integrated with current collision detection methods.

While the importance of “science and technology-based innovation” (STI) and “doing, using and interacting-based innovation” (DUI) innovation modes in firm innovation performance has been well-established, little is known about how they affect the innovation performance of young firms. The author examines the most effective innovation mode and boundary conditions for the innovation performance of developing companies.

The author tests the two modes of innovation using data from 159 young firms in China.

The author’s analysis indicates that a higher level of DUI innovation mode is more relevant to the innovation performance of newly established enterprises. Moreover, the effectiveness of the innovation mode is bound by the networks in which the company operates and interacts. The effectiveness of STI and DUI innovation modes is enhanced when there are high levels of innovation and business network interconnectedness from the technology network partner.

These findings have important implications on innovation research as they highlight the joint effects of innovation modes and quality of network ties on young firms seeking to improve their innovation performance.

STI and DUI innovation modes represent different forms of innovation activities that may affect the knowledge and resources of young firms used to improve innovation performance. Knowing this can help young firms to choose effective innovation mode.

This study makes three contributions. The first is to pay specific attention to the neglected topic of the influence of STI and DUI innovation modes on innovation performance of young firms. Understanding that the two innovation modes offer different methods of gaining knowledge and resources can help young firms choose an effective innovation mode for their business; Second, the author examines the boundary conditions of the effectiveness of innovation modes. Specially, the author examines the moderating role of external networks, which can help clarify conflicting results in this regard. 10;The third contribution is to investigate the importance of network relationships for innovation activities moving beyond the extent of network relationships to instead consider the ability of those relationships to expose a firm to innovative techniques and methods.

The purpose of this paper is to show which models, uncertain or certain, simple or complicated, are more suitable when they are faced with incomplete information and inaccurate data.

The characteristics of fuzzy mathematics, grey system theory, rough set theory and the basic characteristics of incomplete information and inaccurate data in uncertain systems are analysed.

The similarities and differences among fuzzy mathematics, grey system theory, rough set theory and probability statistics are compared. The principle of simplicity of scientific theories, methods, and models are discussed.

It is suggested that the tendency to concentrate on a complicated model isn't always necessary when faced with the condition of incomplete information and inaccurate data.

The paper shows that a more satisfied result can be obtained with an uncertain model than with a meticulous model on a certain situation.

The purpose of this paper is to introduce the elementary concepts and fundamental principles of grey systems and the main components of grey systems theory. Also to discuss the astonishing progress that grey systems theory has made in the world of learning and its wide‐ranging applications in the entire spectrum of science.

The characteristics of unascertained systems including incomplete information and inaccuracies in data are analysed and four uncertain theories: probability statistics, fuzzy mathematics, grey system and rough set theory are compared. The scientific principle of simplicity and how precise models suffer from inaccuracies are also shown.

The four uncertain theories, probability statistics, fuzzy mathematics, grey system and rough set theory are examined with different research objects, different basic sets, different methods and procedures, different data requirements, different emphasis, different objectives and different characteristics.

The scientific principle of simplicity and how precise models suffer from inaccuracies are shown. So, precise models are not necessarily an effective means to deal with complex matters, especially in the case that the available information is incomplete and the collected data inaccurate.

The elementary concepts and fundamental principles of grey systems and the main components of grey systems theory are introduced briefly. The reader is given a general picture of grey systems theory as a new method for studying problems where partial information is known, partial information is unknown; especially for uncertain systems with few data points and poor information.

This study aims to examine the effect of several types of ex post idiosyncratic deals (i-deals) on work–life balance and work well-being, focusing on the mediating effect of work–life balance on the relationship between ex post i-deals and work well-being as well as the moderating effect of gender on the relationship between ex post i-deals and work–life balance in the hospitality industry.

This study uses a questionnaire survey of 642 hotel managers from developed cities in China and analyze the data with structural equation modeling. This study also conducts on-site interviews among 20 hotel managers to support conclusions of the survey.

The results indicate that task i-deals as well as career and incentives i-deals significantly promote work–life balance, thereby indirectly improving work well-being. However, the impact of flexibility i-deals on work–life balance and work well-being is insignificant. The influence of career and incentives i-deals on work–life balance for males is slightly stronger than that for females.

This study has practical implications for hotel employers in terms of using various ex post i-deals to motivate and retain hotel managers by improving personal work–life balance and work well-being.

As one of early attempts to highlight the potential of i-deals to serve as solutions for work–life conflicts and unhappiness issues among hotel managers, this study provides novel insights into the mediating process between ex post i-deals and work well-being from the work–life balance perspective as well as distinct influences of various ex post i-deals on work–life balance for male and female managers.

This study aims to investigate the coupling reaction of epoxide and CO₂ catalysed by alkali metal salts in the presence of ß-cyclodextrin (ß-CD) derivatives to generate cyclic carbonates at various conditions.

The coupling reaction was catalysed by alkali metal salts. The effects of the co-catalysts were investigated by using the conversion rate of raw materials. The affecting factors, such as reaction temperature, amount of the co-catalyst and reaction time, were explored. The possible mechanism of the coupling reaction was discussed.

Results showed that the structure of ß-CD is an important factor influencing the catalytic activity for the coupling reaction of epoxide with CO₂. The catalytic system of 2,3,6-trimethyl-ß-CD with potassium iodide (KI) showed a high catalytic activity. The protocol was expanded to various epoxides, which provided the corresponding cyclic carbonates in excellent yields. The apparent decrease in the yields was not detected after four recycling times. Moreover, the mechanism for the synergetic effect of the catalyst was proposed.

The coupling reactions were achieved in the presence of different structure of ß-CD as co-catalysts. The affecting of substituent of ß-CD were investigated.