This New Articles Channel contents the latest articles published in Inderscience's distinguished academic, scientific and professional journals.
Inferring business relationships in the internet backbone
Several researchers during the last decade have encountered the problem of how to infer business relationships between autonomous systems (ASes) of the internet. Since the internet has a decentralised structure and public data sources containing inter-domain routing information have not been created for topology inference, there are no accurate and comprehensive maps of the internet readily accessible. This challenge has inspired several approaches for inferring business relationships between ASes from BGP routing data. This article presents one implementation of the most recent and most promising approach for relationship inference on AS-level. The algorithm used has been improved in terms performance and quality of the sanitising process. Unlike recent projects, not a only snapshot of the topology of the internet has been inferred but a comprehensive map showing the internet over the last decade. The correctness of this implementation and the inferred dataset is examined by comparison with a business relationship graph and a validation dataset provided by related work.
Collaborative initiatives among international actors within a humanitarian setting
There are a number of collaborative practices among humanitarian organisations aiming of improving the effectiveness and efficiency of humanitarian operations. This study elaborates the objectives of collaboration among international humanitarian organisations, and reviews various types of collaborative network and dyadic initiatives in place in the humanitarian sector. Moreover, we discuss the extent to which the initiatives are employed by humanitarian organisations and the challenges for organisations to engage in the initiatives and act as a successful partner. We also review the challenges in examining the collaborative performance within a humanitarian setting and the factors limiting organisations to appropriately collaborate and attain the desired goals of their relationships. In parallel, we elaborate research enquiries, which may be insightful to be explored in next studies on collaboration among humanitarian organisations.
Drivers' evaluation to implement green marketing practices in automobile industry of China
Green marketing practices are an important green supply chain management (GSCM) activity due to retailer's environmental practices will guide customers green consumption and enhance the environmental performance of the entire supply chain. To successful implement green marketing management, we should identify the various factors which drive retailers to implement green marketing practices. However, these drivers' relationship and the role in the implementation of green marketing practices are not to be considered in the literature. This paper will develop a grey multiple criteria decision making methodology to analyse the relationship among the drivers within the implementation of green marketing practices. Combine three-parameter interval grey number and DEMATEL method to evaluate the relationship among the considered drivers in the automobile industry of China. Finally, we found that top management commitment, government support and consumer awareness are the most important drivers.
Fault-valve behaviour and episodic gas flow in overpressured aquifers - evidence from the 2010 Ms5.1 isolated shallow earthquake in Sichuan Basin, China
We investigated the 2010 Ms5.1 Suining earthquake (a temporally and spatially isolated event) centred in Moxi gas field in the tectonically stable central region of Sichuan Basin, China. The focal depth is estimated to be approximately 2.8 km and thus the earthquake is nucleated in Triassic marine sediment, coincident with the depths of the top boundary of an overpressured gas reservoir. The strike/dip/rake of the estimated source fault is 223/48/122, showing a rupture area of a dimension of ∼2.4 km along a blind reverse fault in agree with the geological structures and regional stress regime of this area. Through an integrated analysis, we propose that the associated fault slip of this earthquake was most probably initiated and driven by gas injection from the underlying overpressured reservoir into the shallower gas reservoirs. No aftershocks following the Suining earthquake indicates that the gas injection from the deeper reservoir is somewhat episodic and a fault-valve behaviour.
Hydraulic fracturing process by using a modified two-dimensional particle flow code - case study
By using a modified PFC2D model, the authors conducted a series of simulations to examine the influences of in-situ stress ratio, fluid injection rate, anisotropy of laminated rocks, and perforation parameters on hydraulic fracturing process. The simulations indicated that: 1) larger in-situ stress ratio will induce smaller breakdown pressures and faster propagation, and hydraulic fractures will extend along the direction of the maximum principal stress or approach to this preferred path; 2) smaller difference of in-situ stresses or faster fluid injection rate is helpful for creation of complex fracture network; 3) weak layers are preferred locations and directions for fracture initiation and propagation in the laminated rocks; 4) hydraulic fractures initiate easily at the bottoms of perforation channels, and propagate generally along or approaching to the direction of maximum principal stress.
Mathematical model of one-dimensional penetration stability failure for gaseous coal
Based on the theory of fluid dynamics in porous media, combined with the gas state equation, Darcy's law and the discriminant equation of one-dimensional seepage instability, a mathematical model of one-dimensional penetration stability failure is established to study the seepage damage law of coal seam. Assuming that the background pressure of the coal wall is attenuated according to the exponential law, the mathematical equation is solved by using the finite difference method. Furthermore, the process of coal bed instability which is supposed as a form of a 'sublayer' pushing forward was analysed. That is, the coal bed loses its stability layer by layer. The calculation results showed that the thickness of the failure sublayer decreases with the reduction of coal permeability and the acceleration of dissipation rate of the background pressure. The model provides a method which can analyse the outburst process and its intensity quantitatively.
Numerical study of immiscible CO2 flooding in thick reservoirs with positive rhythm
Benefitting from the development of carbon capture and storage (CCS) technology, CO2 flooding for enhanced oil recovery (EOR) has become increasingly attractive to the petroleum industry. This paper presents a numerical study about the feasibility and efficiency of the immiscible CO2 flooding process, which is a potential tertiary oil recovery method for use after water flooding, with advantages of lower cost and fewer facility requirements than miscible CO2 flooding. A numerical simulation model established from laboratory experimental results was used to predict fluid behaviour and influence factors of immiscible CO2 flooding in thick reservoirs with positive rhythm to enhance oil recovery after water flooding. Injection and confining pressure conditions are both important to the displacement process and results.
Incremental algorithm for acoustoelastic theory of large static pre-deformed fluid-saturated porous media
The incremental acoustoelastic equations for fluid-saturated porous media (FSPM) under the large static pre-deformation are derived in this paper by incremental loading method based on classic acoustoelastic theory of FSPM, which provides quantitative acoustoelastic relation of FSPM with arbitrary constitutive equation. Isotropic FSPM with third-order constitutive equation are taken as an example to give the relation between wave velocity and confining pressure and discuss the effect of loading step on acoustoelastic relations of isotropic FSPM under closed-pore jacketed condition and opened-pore jacketed condition.
Hydraulic fracturing process by using a modified two-dimensional particle flow code - method and validation
Hydraulic fracturing had been proved as a very useful tool for unconventional oil and gas development, where the fracturing fluid is injected into tight reservoirs under high pressure to enhance the permeability of rock mass. Although hydraulic fracturing theory, numerical modelling, and laboratory experiments develops fast, knowledge is still limited when the geological conditions are complex. This paper presents a numerical method - particle flow code (PFC) - and validates its power for hydraulic fracturing modelling in complex conditions. Firstly, the bonded particle method (BPM) and fluid-mechanical coupling mechanism are introduced; secondly, Darcy's flow in circular particles is simulated; thirdly, a series of numerical simulations is carried out to validate its suitability for hydraulic fracturing modelling; finally, the laminated reservoir will be modelled by BPM. The modelling results show good agreement with classical analytical solution and laboratory test results, which demonstrates that the BPM is a useful and strong tool for understanding the fracturing behaviour of reservoir rocks.
The roles of technology acceptance and computer learner aptitude on accounting student learning achievement with IDEA software
Technology is pervasive in the accounting profession. Successful auditors must be able to use current computer auditing techniques (CAATs). Learning to use these technologies as part of a college accounting curriculum can help ensure new accounting graduates are equipped to participate in all phases of audits from the start of their careers. However, some students learn course-specific technology more easily than others. Our study investigates the roles that student technology acceptance and aptitude for learning technology play in student comprehension of the auditing software IDEA. While prior research has shown that technology acceptance and aptitude for learning technology both are relevant to technology adoption decisions of organisations, prior research has not applied these models to teaching and learning technology. We found that students' perceptions about the ease of use of IDEA, its usefulness, and their intent to use IDEA in their future careers all have significant impacts on their computer learning aptitude. We also found that computer learning aptitude impacted student learning. When students believed their aptitude for learning technology was higher, they showed higher achievement in using IDEA.
Strengthening collaboration and communication skills in an online TPD program for 21st-century educators
The profile of the 21st-century teacher should reflect the philosophy of lifelong and adaptive learners who never stop enriching their knowledge, upgrading their skills and re-calibrating their career paths. To achieve such goals, many academic institutions implement teacher professional development (TPD) programs to support the professional development of the educational community. The goal of our research is to design an online TPD program which allocates roles and activities to learners and manages their progression through both in order to maximise the learning benefits. To this end, a PBLJii script orchestrated in line with the principles of a PBL model and the Jigsaw II collaborative strategy in a CSCL environment (Moodle) was designed and implemented to bolster collaboration and communication skills among teachers. Case study research (examination of one group) was conducted in a number of primary schools in Greece. There was both a quantitative and a qualitative analysis of the chat and forum messages exchanged by the inservice teachers and the results revealed significant development of their collaboration and communication skills as a result of their participation in collaborative tasks.
Medium as frame: comparing mobile audio and video interactions in informal learning contexts
Concept-driven interaction design opens new pathways for research of information and communication technologies (ICTs) in educational contexts, between the particulars of a case study and the abstractions of theory. Explorative research in this project tested foundational theoretical ideas, such as medium specificity, through concrete designs in an authentic setting. During these separate but similar procedures, conducted a year apart, ordinary users were given representative tasks on mobile devices in order to examine the levels of involvement, social facilitation, and satisfaction generated by differing media forms within the mobile delivery system. From this perspective, direct comparisons could be made, for example, between audio and video forms. Enabling such comparisons has grown in importance with the advent of mobile and other convergent technologies that blend mediums to bring together media organisms to comingle. In the case of a smartphone, for example, mobile media designers now can choose which medium (text, audio, video, animation, etc.) they want to use within their master medium, which adds to the complexity of the design endeavour but also to the potential for new integrated and interactive forms to emerge as well as for more mindful context-tailored solutions.
Interaction interfaces in interactive geometry software: are we exploring new devices and possibilities?
Many research findings indicate that Interactive Geometry (IG) software is an effective tool to support geometry learning. Nevertheless, the various forms of interacting with this kind of software have not been widely investigated. As a first step towards bridging this gap, we carried out a literature review regarding the multiple types of interactions offered by GUI of IG software. We searched five digital libraries and collected 998 papers covering more than ten years (2004-2014) of research in the field. As a result we verified that: 1) most of the studies focused on desktop interfaces based on keyboard and mouse; 2) few efforts have been carried out on the design of IG software for devices with multitouch interfaces. By categorising the contributions of papers according to their goal and research approach we hope to organise the valuable contributions of the community and give directions for further research to build better GUI for IG software.
Constructivist research framework for integrating indigenous knowledge into computing education
Some computing educators, especially in African context, have been interested in pedagogical strategies that cultural heritage can provide viable mental models to enhance teaching and learning in curriculum. Particularly, students from Africa have rich cultural heritage that provides new ways of conceptualising computing principles. It is essential that literature provides framework that explains pedagogical benefits of indigenous knowledge in computing education. We analysed scientific publications related to computing education by systematically reviewing the article from constructivist perspectives on students learning from cultural heritage. The study reveals that constructivist philosophical assumptions of multiple meanings to reality and subjectivity in knowledge construction are compatible with the main objective in ethnocomputing studies that seeks to contextualise computing principles in cultural heritages.
Project managers' motivation in the Jordanian construction industries
Today's organisations are concerned with motivation factors that influence the project managers' project achievement and success. In this study, a questionnaire was designed and conducted within the Jordanian construction industry based on five Likert-scales to identify the importance of the motivational dimensions on the project managers in Jordanian construction industry. Six motivational dimensions were defined and analysed, which were; interpersonal interaction, task, general working conditions, empowerment, personal development, and compensation. Results showed that project managers were more motivated with compensation and personal development rather than other dimensions. Also, the level of education for project manager was positively related with the motivation by tasks. A more experienced project manager was highly motivated by empowerment.
Risk management maturity in large complex rail projects: a case study
In this paper, we study the risk management practices in a large complex mass rapid transit construction project undertaken by the relevant government authority in Singapore. A project risk management capability maturity model has been developed and applied in the study. The model consists of ten capability areas namely, organisation culture, stakeholder coalition, leadership, organisation structure and support, risk planning and identification, risk analysis, risk mitigation, process integration and improvement, project management process, and technology. The client organisation has a comprehensive safety and risk management system, which includes life cycle risk management, risk register and documentation, site risk meetings, and so on. Overall, the case organisation shows a high level of risk management capability maturity derived purposeful learning and practices. Specific strengths as well as areas of weaknesses are identified and ranked, and opportunities for further improvement are suggested.
Strategies to improve job outcomes of construction site supervisors
This study examined ways to boost site supervisors' job outcomes through the characteristics of their jobs and how their jobs are designed. Using a structured questionnaire, data were collected from site supervisors working on construction projects in Singapore. Data were collected via face-to-face interviews. It was found that site supervisors have significantly good job outcomes, operationalised as high internal work motivation, high job satisfaction and good quality work performance. The results show some of the significant job characteristics affecting job outcomes are: given discretion to decide what to be done; allowed to offer suggestions for job improvement; regular working hours; and adequate pay. This study found that job outcomes of site supervisors would not significantly improve if their jobs are designed with characteristics which use skill variety, and provide task identity and task significance.
Modelling of trust and working relationship in construction project management: a case study of Vietnam
Trust is regarded an essential lubricant to complete the construction project smoothly. However, few attempts to study how trust helps to improve working relationship in construction projects. The objective of this study is to explore the inter-correlations between antecedences and consequences of trust in project management. Quantitative study was conducted to test the hypotheses. The result of analysis revealed that Relational trust arisen by continual interactions between individuals and Calculus-based trust regarding to beneficial issues based on economic exchange were found to have most contribution to generating a harmony working environment in construction projects through facilitating communication, cooperation, negotiation-problem solving, and relationship satisfaction. However, institution-based trust, which is built up on legal system and professional practice, has least impact on improving working relationship. The research findings are expected to be useful for local construction parties and others that wish to engage in construction market in Vietnam.
Numerical computation of integral of analytic functions in complex plane
A family of interpolatory type of quadrature rules of degree of precision at least seven has been constructed for the approximate evaluation of contour integrals of analytic functions along a directed line segment in the complex plane. The relative accuracies of rules have been studied in their respective classes and also numerically verified by integrating some standard test integrals.
Existence of coincidence point for weakly increasing mappings satisfies (ψ, φ)-weakly contractive condition in partially ordered metric spaces
Nashine and Samet (2011) showed some common fixed point theorems for two mappings satisfying (ψ, φ) weakly contractive condition in an ordered complete metric space. Further, this result was extended by Shatanawi and Samet (2011) to three mappings S, T and R satisfying weakly contractive condition in partially ordered metric spaces in which S, T were assumed to be weakly increasing with respect to R. In the present paper, we define weakly increasing mapping for four self maps and then implant it to prove the coincidence point theorem satisfying a generalised contractive principle.
Construction of some accelerated methods for solving scalar stochastic differential equations
The purpose of this short communication is to contribute in constructing some new solvers for the strong solution of stochastic ordinary differential equations. It is derived that new methods could be obtained as new variants of the high order scheme of Platen (1987). A simple technique to accelerate their speed will also be pointed out. Finally, numerical simulations are brought forward to show the efficiency of the derived methods.
An inpainting result based on p-Laplace operator
In this paper, we propose an inpainting approach, involving a model of an incompressible Newtonian fluid, based on the nonlinear anisotropic p-Laplace diffusion. The proposed resolution algorithm transports automatically the information correction to the damaged part of the image. By numerical experimentations, we prove and illustrate the direct benefit and potentiality, by the performance and the improvement results, on inpainting for real and synthetic images.
A two-level particle swarm optimisation algorithm for open-shop scheduling problem
This paper proposes a two-level PSO algorithm for open-shop scheduling problem. In this algorithm, the upper-level PSO algorithm fine-tunes the parameter values for the lower-level PSO algorithm; the lower-level PSO algorithm then uses the given parameter values to generate the solutions for open-shop scheduling problem. The proposed two-level PSO-based algorithm performs very well on the benchmark instances.
Enhanced social emotional optimisation algorithm with elite multi-parent crossover
Social emotional optimisation algorithm (SEOA) has been successfully applied in a variety of real-world applications. However, it may suffer from slow convergence rate when solving complex optimisation problems. In order to improve the performance of SEOA on complex optimisation problems, in this paper, an enhanced social emotional optimisation algorithm with elite multi-parent crossover (MCSEOA) is proposed. In MCSEOA, it employs the elite multi-parent crossover operator to exploit the neighbourhood solutions of the current population. The numerical experiments are conducted on 13 classical test functions. Comparison results demonstrate that MCSEOA can significantly improve the performance of the traditional SEOA.
A new multi-population-based artificial bee colony for numerical optimisation
This paper presents a new artificial bee colony (ABC) for numerical optimisation. The new approach called NABC, which employs a new multi-population strategy to enhance the diversity of population. The standard ABC is good at exploration, but poor at exploitation. To tackle this issue, a modified solution updating equation is utilised to generate new candidate solutions. Experiments are conducted on ten well-known benchmark functions. Results show that NABC achieves better solutions than the standard ABC and global best guided ABC.
Artificial bee colony with bidirectional search
Artificial bee colony (ABC) is an efficient meta-heuristic, which has shown good search abilities on many optimisation problems. In the standard ABC, its solution updating equation uses a random weight to control the difference vector between the current food source and another randomly selected one, and the random weight between −1 and 1 determines the search directions. How to select a good search direction is not an easy task. In this paper, we propose a new ABC algorithm called ABC with bidirectional search, which employs a new method to control the search direction of ABC. To verify the effectiveness of the bidirectional search method, we embed it into two ABC variants and test compares their performance with their corresponding parent algorithms. Experimental results on six benchmark functions show that the bidirectional search method can effectively improve the performance of ABC.
Artificial bee colony algorithm with improved special centre
Artificial bee colony (ABC) algorithm is a powerful stochastic evolutionary algorithm, which is widely used to solve complex optimisation problems. However, ABC is good at exploration but poor at exploitation because of its search strategy. For overcoming the shortcomings of original ABC algorithm, such as slow convergence and low solution accuracy, we propose a new ABC algorithm - artificial bee colony algorithm with improved special centre (ISC-ABC). Firstly, an improved special centre is used to determine the current gbest position, and lead the colony convergence. Secondly, Employed bees incorporate the information of gbest solution into the search strategy. By this way, the new candidate solutions are always around with gbest. Finally, compare result on 12 classic functions. The results testify that ISC-ABC performs significantly better than original ABC and several recently proposed similar algorithm.
An improved firefly algorithm based on probabilistic attraction
Firefly algorithm (FA) is an efficient optimisation tool, which has been widely applied to various optimisation problems. However, the standard FA still has some drawbacks. For example, the computational time complexity of FA is higher than other swarm intelligence algorithms. Recently, Wang et al. (2016b) designed a random attraction model to reduce the computational time complexity. Based on the random attraction model, we propose a probabilistic attraction model. To test the performance of the proposed approach (PAFA), several benchmark functions are utilised in the experiments. Computational results show that the proposed strategy can effectively improve the performance of FA.
Accruals and real earnings management: testing the debt covenant hypothesis
This paper examines earnings management activities around debt covenant violations. We focus on accruals management and real activities manipulation behaviour of managers in the quarters around the covenant violation. We expect covenant restrictions to influence these activities in the quarters surrounding and the quarter of the violation. The evidence is consistent with managers manipulating earnings using accrual-based and real earnings management activities and provides evidence for the debt covenant hypothesis. Cross-sectional analyses reveal that managers appear to manipulate accruals in successive quarters in order to increase reported earnings. The evidence on the use of real activities suggests that while managers increase reported earnings in the violation quarter, they have limited discretion over the use of real earnings management techniques in the quarters surrounding the violation.
R&D investment, management entrenchment and governance mechanisms: evidence from French listed companies on SFB120 index
The aim of this paper is to investigate the effects of management entrenchment on research and development business decisions in the French listed companies and to detect these effects when we test simultaneously the impact of the board of directors' characteristics and the external audit quality. Using data from the French listed companies on the SBF 120 index during the period 2003-2011, this paper statistically tests the hypotheses on the relationship between corporate R&D intensity and managers' entrenchment indicators associated with two types of corporate governance mechanisms: the board of directors' characteristics and the external audit quality. Our results show that R&D intensity is affected by most of management entrenchment indicators (the age, the career, the stock ownership, the education and the firm's past performance), the external audit quality and some control variables (the size and the industry).
The effectiveness of financial-hedging techniques: a Gulf Cooperation Council perspective
The paper examines the effectiveness of financial-hedging techniques - forward hedging, money-market hedging and cross-currency hedging, for a domestic firm in the Gulf Cooperation Council with foreign-currency exposure to GBP, CHF and JPY. The results show that there is no difference between using forward hedging or money-market hedging, owing to the high correlation between spot and forward rates. However, in relation to cross-currency hedging, the results are mixed: the effectiveness of cross-currency hedging depends on exchange-rate correlation.
Determinants of earnings management in India: 2002-2011
The study examines and quantifies the extent of earnings management (EM) in India by studying a cohort of 1,150 publicly listed Indian companies (non-financial) during 2002-2011. The study shows that the average EM in the Indian non-financial corporate sector is 1.5% of the total assets of these firms in the previous year. The study also finds that EM has recorded a growth of 1.7% per annum during 2002-2011. The average discretionary accruals of small-sized firms at 3.7% were substantially higher than medium (1%) and large-sized firms (0.52%). The increases in earnings management (discretionary accruals) among small firms (4.3% per annum) were higher than those of medium (1.6% per annum) and large firms (decline of 0.5%). The empirical analysis also finds that the firm size and EM are negatively correlated. The study also finds relatively higher earnings management among agriculture, construction and services industries.
Expansion of science-based industries: technological and organisational accumulation vs. fragmentation? Insights from biotechnology in Estonia
The governance of high-technology areas poses considerable strategic challenges to transition and developing countries. This study aims to emphasise the importance of the local context as a root of systemic problems from a new perspective. The specific interest concerns the developments in the field of biotechnology in one of the CEE countries, Estonia. The in-depth analysis of Estonia's case reveals parallel but contradictory tendencies at the local level. Whereas the expansion of the industry (increasing number of start-ups) is converging around the limited major players in the field, the convergence at the organisational level reflects the orientation taken on risk management strategies (as derived from the management of a common structure) rather than R&D-intensive synergies and specialisations. The appropriateness of innovation support measures in use and the respective policy-making capabilities (with specific interest in the usage and the impact of the EU Structural Funds) make the issue even more constrained. Hence, the case of Estonia demonstrates the dysfunction of the local innovation management and governance mechanisms and its adverse effect on the sector's long-term performance.
Innovation management framework: case studies of firms in Thailand
The aim of this paper is to develop a framework of relevant factors of innovation management that will help firms avoid failures in innovation projects in developing country, Thailand. This paper conducted literature review of innovation management models, and analysed the contextual factors from the largest four conglomerates in Thailand that were driven by innovation policy through in-depth semi-structure interviews and observations. The factors were criticised and weighted on whether they are relevant and critical to the innovation management to generate a proposed framework. A quantitative based instrument in the form survey questionnaire is used as research instrument. The item content validity was subsequently applied to verify the instrument. Finally, a survey of 325 samples from firms in Thailand was conducted. This research develops a framework of relevant factors presents a comprehensive innovation management framework for innovation manager and policy maker.
Linking megaprojects for local technological capability development in developing countries - a literature review
Complex megaprojects, costing above $1 billion, gained significant research interest from their engineering, management, complexity, risks and other perspectives. For developing economies especially, they present significant learning opportunity to build technological capability with interaction of local firms with international contractors. Using scholarly articles review, the present paper reviewed past literature, enlightening gap observed and the linkage demanded between megaprojects and their potential for technological capability development. Results indicate that past researches have not given emphasis to investigate technological capability development through megaprojects executed in developing countries. After discussion on relevant subtopics, the gaps to be filled and link the two topics are elaborated individually. Conclusions drawn are directed towards new research paradigm that investigates opportunities that have priceless contribution for developing economies.
International technology transfer as innovation factor in EU countries
Analysis of historical data reveals that European economies have often gained development opportunities thanks to efficient exploitation of technologies obtained from abroad. This did not happen as a result of a simple acquisition of ready-made solutions, but through active operations of enterprises taking advantage of the particular elements of purchased technologies and using them to create their own innovations. Moreover, an accumulation of technological knowledge took place in developing sectors and product groups. The sectors which used imported knowledge elaborated it and generated their own technological capabilities, which enabled them to create new market space, where the improved products and processes could be sold or utilised, also on international markets. In this way, conditions conducive to innovation were created. Transfer of technology from abroad supplemented domestic innovation capacities based on R&D. The purpose of the paper is to analyse the relationship between international technology transfer and innovation growth in the EU. This will make it possible to answer the following question: Why do some economies make use of technology transfer, thus accelerating their development, while others fail to do so. Utilisation of technological opportunities appears to be, therefore, economy-specific.
Modelling and optimisation of wire electrical discharge machining process on D2 steel using ANN and RMSE approach
Attempt has been made to optimise surface roughness (Ra) of cold worked high carbon and high chromium hard die steel (AISI: D2) by wire electrical discharge machining (WEDM) process. In present study fractional factorial design of experiment has been used at two levels to conducted five different sets of experiment. Tan-sigmoid and pure line transfer function-based four layered back propagation artificial neural network (BPANN) approach have been applied to develop a suitable model with six WEDM process input parameters and two output parameters, i.e., Ra and material removal rate (MRR). The effect of input parameters has been analysed by training data for the best model using analysis of variance (ANOVA). The model S2 has been found satisfactory as training correlation coefficient (R2) is 99.2% and adjusted correlation coefficient (Radj)2 is 99.1%. The minimum surface roughness has been found using root mean square error (RMSE) approach.
Strains and microstructures of AZ61 magnesium alloy caused by different channel angles and preheated temperatures of extrusion-shear process
Extrusion-shear (ES), a method having the potentiality of obtaining fine microstructures of magnesium alloys, has been studied to refine grains of AZ61 magnesium alloy. During ES process, the channel angles and preheated temperatures play a critical part in the deformation behaviours of magnesium alloy. Thus, the effects of their effect on the strain distributions and microstructures evolutions in AZ61 magnesium alloy during ES process have been studied using simulation and experiments. The strains in the extruded rods during ES process with different channel angles have been obtained by simulation using three-dimensional (3D) geometric models and finite elements simulations of ES processes. Then, ES processes were conducted to prepare the samples of AZ61 magnesium alloy. With the microstructures evolvements observed, it is found that the strains of ES process decrease with the increasing of the channel angles and they increase with the increasing of preheated temperatures. Smaller channel angles and bigger preheated temperatures could improve the refinements of magnesium alloys.
Corrosion performance of 5182 aluminium alloy in calcium chloride solution
Corrosion behaviour of 5182 aluminium was evaluated in terms of weight change in a 30% calcium chloride solution at temperatures ranging from 0°C to 65°C. The test results indicate that there is a critical temperature (35°C) above which the alloy experiences weight gain and below which the alloy experiences weight loss during the corrosion processes. Optical light microscopy (OLM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were carried out to characterise the corrosion behaviour of this alloy. The results indicate that weight gain and weight loss occur under different corrosion mechanisms.
Semi-solid moulding technology in making automotive turbocharge compressor wheels
Diesel and gasoline engines are the most important sources of energy consuming, emission and global warming. To increase fuel efficiency and reduce emission, air pressure ratio of the engine needs to be further increased. The increase of air pressure is achieved by a compressor wheel in the turbocharger. The compressor wheel needs very complex blade geometry to achieve high pressure ratios. The very latest technique for impeller manufacture is called semi-solid moulding (SSM). This paper will present recent development of SSM including thixo-casting and rheo-casting processes in making aluminium compressor wheels. Experimental results show SSM material has superior microstructure and mechanical properties over cast and is comparable to material machined from solid. Component testing including performance and durability testing proves the SSM compressor wheels emerge as being significantly more durable than cast equivalents and approaching that of machined impellers.
Niobium in cast irons
The effect of niobium on microstructure and mechanical properties of Nb-contening cast irons, including gray cast iron, undercooled cast iron, and nodular cast iron were discussed in this paper. Besides, the application of Nb-contening cast irons was also proposed and expected in the future.
In vitro evaluation of cell compatibility and hemocompatibility of a Cu-bearing titanium alloy
A new antibacterial copper (Cu)-bearing titanium alloy, Ti-6Al-4V-5Cu alloy is fabricated by introducing Cu into conventional titanium alloy. However, Cu is a double-edged sword and excessive Cu ions release may lead to biological problems. In this study, considering the potential toxicity of Cu release from Ti-6Al-4V-5Cu alloy, the cytocompatibility, hemocompatibility and electrochemical corrosion behaviour of the alloy are systematically studied. The results indicate that MC3T3-E1 cells grew well on surface of Ti-6Al-4V-5Cu alloy and the relative growth rate is higher than 75%, showing good cytocompatibility. Platelets on surface of Ti-6Al-4V-5Cu alloy are less and fully spread, and the hemolysis ratio is 0.6%, showing good hemocompatibility of the alloy. Ti-6Al-4V-5Cu alloy shows great potentials in clinical application with strong antibacterial performance, good cytocompatibility and hemocompatibility.
Artificial neural networks and multi response optimisation on EDM of aluminium (A380)/fly ash composites
Aluminium metal matrix composites reinforced with fly ash particles of three different particle size ranges [(53-75) µm, (75-103) µm and (103-125) µm] were fabricated using stir casting technique. Electrical discharge machining was employed to machine the composite materials with copper electrode. The influence of EDM process parameters namely peak current, pulse-on-time, pulse-off-time, particle size and the percentage fly ash on material removal rate, tool wear rate and surface roughness were investigated. Artificial neural network model was employed to predict the material removal rate, tool wear rate and surface roughness of the composites. The experimental values coincide with the predicted values of the proposed networks. The process parameters are then optimised using desirability-based multi response optimisation technique to maximise the MRR and minimise both TWR and SR. Increase in peak current and pulse-on time increased the MRR while increase in pulse-off time, percentage fly ash and fly ash particle size decreased the MRR. The experimental results along with the ANN model and multi response optimisation will serve as a technical database for aerospace, automotive, military and commercial applications.
Compound option pricing under stochastic volatility
The paper proposes a flexible and computationally efficient lattice-based approximation for evaluating European and American compound options under stochastic volatility models. In comparison with the existing evaluation procedures, the method is more flexible because it may accommodate several stochastic volatility specifications of the asset price process, and more efficient because it is computationally faster in computing accurate compound option prices. The method is obtained as an extension of Costabile et al. (2012) discretisation, which consists in approximating the stochastic volatility process by a recombining binomial lattice, and considers the asset value as an auxiliary variable whose dynamics is captured by generating subsets of representative realisations to cover the range of possible asset prices at each time slice. The backward induction scheme based on a linear interpolation technique is adapted to compute both the underlying daughter option and the compound option prices. Numerical experiments confirm the method efficiency and accuracy.
Hedging derivative securities with volatility futures
We show a method to replicate S&P 500 exchange traded fund (ETF) European synthetic put by optimally rebalancing a portfolio of the underlying ETF shares, the VIX futures contracts, and treasury bonds over discrete periods. The motivation for this study is two-fold. Firstly, market-makers in S&P 500 index options may need to hedge a large short position synthetically when the puts are in short supply. Secondly, for an institutional investor holding a large diversified portfolio of US stocks, constructing a long position in synthetic puts is tantamount to providing portfolio insurance. The put replication is useful as the alternative of buying US puts can be prohibitively expensive in a distressed market. The numerical method of Gauss-Hermite quadrature is employed in the optimal solution. Both simulations and empirical validation using historical S&P 500 index ETF and VIX futures price data show effectiveness in the put pricing versus more traditional methods.
Tax motivated derivative structures with 'sweet spot' payoffs
In this paper, we review the role of market microstructure issues in the design and function of tax shelter schemes based on exotic currency option transactions. We review instruments commonly used in the currency derivative markets and discuss the critical role of market frictions in evaluating the sensibility of transactions from an economic perspective. We analyse a sample transaction with a potential 'sweet spot' payoff in order to identify the role of the potential sweet spot payoff in the valuation of the structure. We estimate the fundamental value of the structure using a theoretical value for the sweet spot. We then explain that realistic consideration of market microstructure, or trading frictions, suggest that the actual value claim for a potential sweet spot payoff is zero. Our analysis provides a simple framework for determination of the reasonableness of a claimed profit motive as motivation for entering into structured transactions that contain currency derivatives.
Catching the elusive herder: a second look at herding in heterogeneous samples
We study herd behaviour in security trading by examining Wermers' portfolio change measure or PCM. In this paper, we show that PCM can fail to capture herding in certain heterogeneous samples. We give a theoretical analysis of the underlying mathematical mechanism and provide a proof that PCM can be minimised under certain portfolio conditions. We study the algebraic and geometric properties of PCM in their relations to both the individual and collective decisions of the managers in trading equities. A discussion on the lifting of these conditions is also provided to broaden the analysis in order to adapt to more complex scenarios in the securities market.
On the relative performance of consumption models in foreign and domestic markets
We revisit the literature that explores the relationship between domestic and foreign markets asset pricing puzzles, by evaluating the relative performance of different consumption-based models. We estimate and test the overidentifying restrictions of Euler equations associated with the consumption capital asset pricing model, in its canonical and main reference level versions. Our main findings are: 1) similar, however unreasonable, values for the parameters are obtained for most of the models in both equity and foreign exchange markets; 2) rejections or otherwise of overidentifying restrictions occurs for the two markets, suggesting that success and failure stories for each model takes place in the other market. We also compare the consumption-based pricing kernel with a preference-free pricing kernel built in da Costa et al. (2015) and perform in-sample predictions exercises. Our work provides empirical grounds to believe that progresses on preference-based solutions to puzzles in domestic financial markets will shed light on puzzles in foreign exchange market as, for example, recent work by Verdelhan (2010).
Discrete-time stochastic volatility process in option pricing: a generalisation of the Amin-Ng and the Black-Scholes models
Most option pricing formulas are derived in the framework of continuous-time models, but predominantly they are used in discrete-time models. In this paper, a new discrete-time econometric model with stochastic volatility and stochastic interest rate is proposed, and within its framework the option pricing formula for a European call option is derived. Thanks to this, the model can be directly used (without any discretisation) for option pricing. Moreover, our formula, under some assumptions, reduces itself to the well-known Amin and Ng formula.
A robust method to retrieve option implied risk neutral densities for defaultable assets
Risk neutral densities recovered from option prices can be used to infer market participants' expectations of future stock returns and are a vital tool for pricing illiquid exotic options. Although there is a broad literature on the subject, most studies do not address the likelihood of default. To fill this gap, in this paper we develop a novel method to retrieve the risk neutral probability density function from call options written on a defaultable asset. The primary advantage of the method is that default probabilities inferred by the model can be analytically expressed and, if available, can be incorporated as an input in a flexible, robust and easily implementable manner.