Search results

This chapter reviews the effects of air transport liberalization, and investigates the roles played by airport-airline vertical arrangements in liberalizing markets. Our investigation concludes that liberalization has led to substantial economic and traffic growth. Such positive outcomes are mainly due to increased competition and efficiency gains in the airline industry, and positive externalities to the overall economy. Liberalization allows airlines to optimize their networks, and thus may introduce substantial demand and financial uncertainty to airports. Vertical arrangements between airlines and airports may offer a wide range of benefits to the parties involved, yet such arrangements could also lead to airline entry barriers which reduce the effects of liberalization. Three approaches have been developed to model the effects of liberalization in complex market conditions, which include the analytical, econometric and computational network methods. These approaches should be selectively utilized in policy studies on liberalization.

The five countries in Central Asia, namely Uzbekistan, Kazakhstan, Turkmenistan, Tajikistan, and Kyrgyzstan, are landlocked and therefore rely critically on aviation for passenger travel and express cargo logistics. However, despite substantial growth in the past decade, the aviation market in the region is still not realizing its full potential. This chapter reviews the development status of the international air travel market from Central Asia, with an aim of identifying the key barriers for industrial development and growth, and possible remedies to address these challenges. Overall, our study suggests that international market growth from the region is significantly influenced by historical patterns and political ties with Russia. Whereas markets linking selected countries such as Turkey and the UAE have experienced substantial growth, further liberalization is needed for the region to achieve better connectivity with major trade partners and aviation markets.

A finite difference method for solving the quasi one‐dimensional non‐equilibrium hypersonic flow equations in a diverging nozzle is presented and discussed. In chemically reacting flows the system of equations to be solved is very stiff. Some reactions may be several orders of magnitude faster than others and generally, they are much faster than the convective process except for very high Ma numbers. For this reason the development of a numerical scheme whose stability is independent of the chemical reaction rates is of importance. The main advantage of this scheme is the conservation of each chemical component, the positivity of densities and vibrational energies, as well as its relative simplicity, which results in a fast computer code.

The purpose of this study is to investigate the thermomechanical condition on the shape memory property of Polybutylene adipate-co-terephthalate (PBAT). PBAT is a widely researched and rapidly developed biodegradable copolyester. In a tensile test, we found that the fractured PBAT samples had a heat-driven shape memory effect which piqued our interest, and it will lay a foundation for the application of PBAT in new fields (such as heat shrinkable film).

The shape memory effect of PBAT and the effect of the thermomechanical condition on its shape memory property were confirmed and systematically investigated by a thermal mechanical analyzer and tensile machine.

The results showed that the PBAT film had broad shape memory transform temperature and exhibited excellent thermomechanical stability and shape memory properties. The shape memory fixity ratio (Rf) of the PBAT films was increased with the prestrain temperature and prestrain, where the highest Rf exceeded 90%. The shape memory recovery ratio (Rr) of the PBAT films was increased with the shape memory recovery temperature and decreased with the prestrain value, and the highest Rr was almost 100%. Moreover, the PBAT films had high shape memory recovery stress which increased with the prestrain value and decreased with the prestrain temperature, and the highest shape memory recovery stress can reach 7.73 MPa.

The results showed that PBAT had a broad shape memory transform temperature, exhibited excellent thermomechanical stability and shape memory performance, especially for the sample programmed at high temperature and had a larger prestrian, which will provide a reference for the design, processing and application of PBAT-based heat shrinkable film and smart materials.

This study confirmed and systematically investigated the shape memory effect of PBAT and the effect of the thermomechanical condition on the shape memory property of PBAT.

This paper is supposed to provide a critical review of current research progress on thermal management in grinding of superalloys, and future directions and challenges. By understanding the current progress and identifying the developing directions, thermal management can be achieved in the grinding of superalloys to significantly improve the grinding quality and efficiency.

The relevant literature is collected from Web of Science, Scopus, CNKI, Google scholar, etc. A total of 185 literature is analyzed, and the findings in the literature are systematically summarized. In this case, the current development and future trends of thermal management in grinding of superalloys can be concluded.

The recent developments in grinding superalloys, demands, challenges and solutions are analyzed. The theoretical basis of thermal management in grinding, the grinding heat partition analysis, is also summarized. The novel methods and technologies for thermal management are developed and reviewed, i.e. new grinding technologies and parameter optimization, super abrasive grinding wheel technologies, improved lubrication, highly efficient coolant delivery and enhanced heat transfer by passive thermal devices. Finally, the future trends and challenges are identified.

Superalloys have excellent physical and mechanical properties, e.g. high thermal stability, and good high-temperature strength. The superalloys have been broadly applied in the aerospace, energy and automobile industries. Grinding is one of the most important precision machining technologies for superalloy parts. Owing to the mechanical and physical properties of superalloys, during grinding processes, forces are large and a massive heat is generated. Consequently, the improvement of grinding quality and efficiency is limited. It is important to conduct thermal management in the grinding of superalloys to decrease grinding forces and heat generation. The grinding heat is also dissipated in time by enhanced heat transfer methods. Therefore, it is necessary and valuable to holistically review the current situation of thermal management in grinding of superalloys and also provide the development trends and challenges.

The purpose of this paper is, based on leisure constraints and means-end theories, to identify the e-leisure constraints of using the video-sharing websites/apps; demonstrate how means-end theory can be used to reveal the differences between high- and low-leisure constraints in an e-leisure environment; and provide designers and marketers with valuable insights for developing e-leisure products and e-marketing strategies.

Both qualitative and quantitative approaches are employed to collect data. By eliminating three participants whose age range did not meet our criterion (15 to 24 years old), 57 one-on-one in-depth interviews were then content analyzed to design the survey questionnaire. A total of 514 valid samples were collected for hierarchical value map (HVM) construction.

By comparing the full HVM vs the e-leisure constraints HVM, the analytical results indicate that the importance of attributes, consequences and values for the young people using video-sharing websites/apps is quite different. “Unable to resume the video after leaving the screen,” “creating playlist,” “providing movies” and “location restrictions” are extremely important features that influence the willingness of such users with high e-leisure constraints to participate in e-leisure activities. By understanding the differences between these two HVMs, it is possible to provide marketers or designers with valuable insights for website/app design and marketing strategies.

This study only focused on young people’s perceptions of video-sharing websites/apps, so the findings are limited to those aged between 15 and 24 years old. Since managers today are challenged to design effective strategies that can meet target users’ demands across different ages with different economic, social and sub-cultural groups, future research may consider gathering a wider age range of respondents in order to obtain more robust results.

This is the first paper integrating leisure constraints theory and means-end theory to understand young people’s cognitive structure of using video-sharing websites/apps, especially when they encounter e-leisure constraints.

To address the safety concerns generated by truck crashes occurred in big cities, this paper analyzes the zip code tabulation area (ZCTA)-based truck crash frequency across four temporal intervals – morning (6:00–10:00), mid-day (10:00–15:00), afternoon (15:00–19:00), and night (19:00–6:00) in New York City in 2010. A multivariate conditional autoregressive count model is used to recognize both spatial and temporal dependences. The results prove the presence of spatial and temporal dependencies for truck crashes that occurred in neighboring areas. Built environment attributes such as various types of business establishment density and traffic volume for different types of vehicles, which are important factors to consider for crashes occurred in an urban setting, are also examined in the study.

This paper aims to develop a non-linear finite element model predicting the response of externally strengthened beams under a three-point flexure test.

The ANSYS software is used for modeling. SOILD65, LINK180, SHELL181 and SOLID185 elements are used, respectively, to model concrete, steel reinforcement, polymer and steel plate support. A parametric study was carried out. The effects of compressive strength, Young’s modulus, layers number and carbon fiber-reinforced polymer thickness on beam behavior are analyzed. A comparative study between the non-linear finite element and analytical models, including the ACI 440.2 R-08 model, and experimental data is also carried out.

A comparative study of the non-linear finite element results with analytical models, including the ACI 440.2 R-08 model and experimental data for different parameters, shows that the strengthened beams possessed better resistance to cracks. In general, the finite element model’s results are in good agreement with the experimental test data.

This model will predict the strengthened beams behavior and can describe the beams physical conditions, yielding the results that can be interpreted in the structural study context without using a laboratory testing.

On the basis of the results, a good match is found between the model results and experimental data at all stages of loading the tested samples. Crack models obtained in the non-linear finite element model in the beams are also presented. The submitted finite element model can be used to predict the behavior of the reinforced concrete beam. Also, the comparative study between an analytical model proposed by of current code of ACI 440.2 R-08 and finite element analysis is investigated.

Economic theory suggests that profits of firms in industries with higher competition are less persistent and more volatile than in industries with lower competition (Stigler, 1963; Mueller, 1977). Extending this reasoning, I hypothesize that accounting-based fundamentals are more effective in predicting performance in industries with lower competition. I find that a measure of fundamentals (Piotroski’s F-score) has greater ability to identify potentially mispriced securities in industries with lower competition. The results are robust to using a variety of competition measures and imply that industry competition is an important consideration in the application of fundamental analysis.

Dementia in older persons with learning disabilities is a growing concern for all those involved in their care. There is at present no effective treatment, but the importance of current drug treatments is reviewed. Developments in drug treatments for dementia remain an active area of ongoing research.