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Modern CAD systems facilitate the creation of any surface geometry imaginable, and complex surfaces for free-form grid shells are often represented by a set of Non-Uniform Rational B-Splines surface patches. But it remains an intractable issue how to generate high-quality grids on complex surfaces efficiently. To solve this issue, an automatic triangular mesh generation method is presented, based on bubble dynamics simulation and a modified Delaunay method.

A moderate amount of points are first distributed on a given surface. Next, by regarding the points as elastic bubbles with the same size and introducing the forces acting on bubbles, the motion control equations of bubbles are established. The equilibrium state of the bubble system is found by Verlet algorithm. Then, the Voronoi diagram on the surface is obtained by calculating the intersection between the surface and the three-dimensional (3D) Voronoi diagram of the centers of bubbles. Finally, a triangular mesh, Delaunay triangulation on the surface, is determined based on the dual change of the Voronoi diagram.

This method generates meshes on the surface directly, unlike mapping-based methods, avoiding the mapping distortion. Examples are given to demonstrate the successful execution of this method. The result also illustrates that this method is applicable to various surfaces in high automation level and resultant meshes are highly uniform and well-shaped.

Thus, this method provides the convenience for the geometry design of complex free-form grid structure.

The purpose of this paper is to propose a new stabilized finite volume element method for the Navier-Stokes problem.

This new method is based on the multiscale enrichment and uses the lowest equal order finite element pairs P₁/P₁.

The stability and convergence of the optimal order in H¹-norm for velocity and L²-norm for pressure are obtained.

Using a dual problem for the Navier-Stokes problem, the convergence of the optimal order in L²-norm for the velocity is obtained. Finally, numerical example confirms the theory analysis and validates the effectiveness of this new method.

This study examines the extent to which gold and silver bubbles are correlated and which metal’s bubble spills over to the other. In addition, the overlap in bubble-like episodes for the two metals is demonstrated and the influence of crises (global financial crises, European debt crisis and the COVID-19 pandemic) on the development of these episodes is compared.

This study proposes a two-step approach. In the first step, price bubbles are identified based on the backward sup augmented Dickey–Fuller of Phillips et al. (2015a, 2015b) and modified by Phillips and Shi (2018). In the second step, the correlation in the contagion effect of the bubbles between the two precious metal prices is measured using a nonparametric regression with a time-varying coefficient approach developed by Greenaway-McGrevy and Phillips (2016).

The findings suggest that the safe-haven property of gold and silver during financial market turbulence induces excessive price increases beyond their fundamental values. Furthermore, the results indicate that bubbles are contagious among precious metal markets and flow mainly from gold to silver; these findings are associated with the period after 2005, particularly during the global financial crisis. A contagious bubble effect is not found between gold and silver during the coronavirus disease 2020 pandemic.

The results suggest that financial market participants should consider portfolio weights in precious markets in light of the bubble correlation between gold and silver, especially during crises.

To the best of the authors’ knowledge, this is the first study that explores the correlation of bubble-like episodes between gold and silver.

The authors make a fundamental initial effort to conduct a systematic review analysis on “cryptocurrency,” mainly to analyze the way it has been changing the “stereotype” financial transactions, and also identify the probable unexplored research avenues on this innovative investment regime. The study aims to draw the landscape of the current state, prospects, challenges, trends and possible agendas of cryptocurrency in the global market.

Using a quali-quantitative approach widely known as meta-literature review, the synthesis analysis on “cryptocurrency” is conducted. Methodologically, the authors review and analyze the most recent and relevant papers preferably published between 2016 and 2020 in leading business and finance journals of ISI Web of Science (ISI WOS) through bibliometric analysis particularly coupled with content analysis.

The findings of the meta-analysis summarize the relevant stylized facts of the cryptocurrency market: distinctive features of blockchain technology, decentralized payment method, low-cost facility, ensuring pseudo-anonymity, independence from central authority, double spending attack protection, organic and instantaneous nature, among others. In addition, the analysis identified several future research regimes: pricing model, prospect of investment regime, hedging properties, volatility dynamics, information asymmetry, underlying risk factors and bubble-like nature in global cryptocurrency market.

This academic novelty significantly contributes to enhance our knowledge on the current state-of-the-art of digital finance, outlines the research agenda and eventually provides important investment implications for financial managers, research analysts, investors, market practitioners, regulatory compliance professionals and policymakers. Therefore, the findings shed the lights on new investment opportunity in the global market.

Cryptocurrency, virtual currency or digital asset having cryptography for idiosyncratic security features, seems to be a persistent paradigm shift in the digitalized financial system. Despite the continuing growth, the academic research on cryptocurrency is still at nascent stage, particularly because researchers did not deeply draw attention at this financial innovation. In addition, the authors argue that none of the earlier studies yet conducted a meta-analysis on this latest investment regime. Therefore, this review study is the initial attempt to fill up the gap in the finance literature.

The purpose of this paper is to study numerically the effects of heat transfer on the strength of shock waves emitted upon spherical bubble collapse.

The motion of bubble under ultrasound is predicted by solutions of the Navier‐Stokes equations for the gas inside a spherical bubble. The Gilmore model and the method of characteristics are used to model the shock wave emitted at the end of the bubble collapse.

The theory permits one to predict correctly the bubble radius‐time curve and the characteristics of shock wave in sulphuric acid solution. These simulations indicated that the heat transfer inside the bubble and the liquid layer plays a major role in the bubble behaviour and the strength of the shock waves. Also, the developed numerical scheme is checked for different gas bubble like air, Argon and Xenon. It is observed that the gas thermal conductivity plays an important role in the shock wave strength. A good agreement is observed by comparison of the results with the experimental data.

The effect of heat transfer on the emitted shock wave strength has not been studied previously. In this paper, a numerical scheme is developed to consider heat transfer on the shock. Also, this simulation is checked for different gas conductivities.

This paper analyzes the efforts made by the Telefonica Group (the main Spanish firm in the telecommunications sector) to evolve from a bureaucratic culture to another oriented towards total quality and the customer. The need for this change came as a result of the liberalization in the telecommunications sector in the early 1990s. Through an analysis of the internal documents generated in the process, and also by means of several interviews with executives and consultants who took part in the design and introduction of the change mentioned above, we study the validity and effectiveness of the steps taken. The methodology used by the firm was based on the “bubble‐like” (from one division to the whole organization) and “cascade‐like” (from the top management to the lowest levels) implementation systems, based on the support of strong training, communications and participation programmes.

This paper aims to first explain short selling and its benefits and damages; then, using experts’ opinions and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method as well as based on the legal, financial and jurisprudential criteria adopted, evaluate and prioritize Islamic alternatives to short selling; and finally, introduce the most proper approach for implementing it in Iran’s stock market.

The methods applied in the paper are as follows: Library method to collect the required data for developing the theoretical and jurisprudential foundations of the study, identifying the appropriate criteria for prioritizing; the alternative methods for short selling in the Islamic markets; and the field method to determine the level of significance of the ranking criteria and prioritize the alternative methods for short selling in the Islamic markets on the basis of such criteria. The alternative methods for short selling in Iranian stock market were identified and analyzed jurisprudentially and legally. Afterwards, these strategies were prioritized based on the (legislative, financial and jurisprudential) criteria which were adopted in the form of Delphi from the related literature, research and expert opinions by means of TOPSIS approach. The method with the highest ranking will be introduced as the alternative method for short selling.

The paper suggests that among all Islamic alternatives to short selling, based on experts’ opinions and legal considerations, method of combining Murabaha and Wa’ad is the most proper strategy in Iranian stock market.

An important limitation we faced in this study was limited familiarity of Iran, capital market participants with Islamic finance concepts including Islamic alternatives to short selling. Therefore, designed questionnaire was sent only to participants who had experience in the field of Islamic finance that they were not more than 31 people. Of course, in this study, large sample size was not necessary because the questionnaire was completed by experts, and therefore, results were scientific and reliable.

One of the transaction strategies which significantly contributes to the enhancement of market liquidity is short selling. However, this strategy is not applicable to the Islamic stock markets because of its contradictions with a number of Islamic laws. Therefore, Islamic financial researchers have attempted to design relevant legal mechanisms drawing on the Islamic contracts to make use of the merits of this transaction strategy. In addition to introducing short selling and its demerits for the stock market, the paper explored the alternative methods and proposed the most proper one for implementing in Iranian stock market.

This chapter aims at shedding light upon how transforming or detrending a series can substantially impact predictions of mixed causal-noncausal (MAR) models, namely dynamic processes that depend not only on their lags but also on their leads. MAR models have been successfully implemented on commodity prices as they allow to generate nonlinear features such as locally explosive episodes (denoted here as bubbles) in a strictly stationary setting. The authors consider multiple detrending methods and investigate, using Monte Carlo simulations, to what extent they preserve the bubble patterns observed in the raw data. MAR models relies on the dynamics observed in the series alone and does not require economical background to construct a structural model, which can sometimes be intricate to specify or which may lack parsimony. The authors investigate oil prices and estimate probabilities of crashes before and during the first 2020 wave of the COVID-19 pandemic. The authors consider three different mechanical detrending methods and compare them to a detrending performed using the level of strategic petroleum reserves.

To investigate the potential to employ tactile form‐shaping as a prerequisite to the production of physical industrial design models by rapid prototyping.

Using a haptic feedback device to allow the designer to “feel” 3D virtual geometry as part of the evaluation and sculpting process. To maintain a close association with professional practice, this was undertaken as part of a product design case study in which a haptic feedback/rapid prototyping strategy was compared and contrasted with the more traditional workshop‐based shaping of Styrofoam by hand.

The use of a haptic feedback device facilitated the production of rapid prototype components that had been defined through feel and sculpting, albeit prior to the build process. Despite shortcomings in the ability to replicate activities undertaken in a workshop environment, other creative opportunities emerged that could not have effectively been produced using any other methods.

Whilst based on generic industrial design methods, the findings are drawn from only one case study.

A useful evaluation for those wishing to undertake further research into haptic feedback modelling or employ such a system during professional practice.

The study moves forward the debate into the merits and application of virtual and physical modelling techniques and provides useful case study evidence of direct comparison.

The purpose of this paper is to test for bubbles in the US hard red spring (HRS) wheat market from 2004 to 2014, with particular focus on 2007-2008 when the market experienced record-high price volatility.

The authors apply a recently developed bubble testing procedure to cash, rolling nearby futures contract, and individual futures contract prices of HRS wheat sampled at daily, weekly, and monthly frequencies. Two critical value (CV) sequences are derived to date-stamp bubbles, one from Monte Carlo simulations, and the other from recursive wild bootstrap procedure.

The authors find that regardless of the price series adopted, sampling frequency chosen, or CVs used, bubbles account for only a small fraction of the HRS wheat price behavior during 2004-2014. However, much sharper differences are detected regarding the key policy question of bubble behavior during 2007-2008. Individual futures contract prices during this period suggest only a minimal number of bubble days, while rolling nearby futures and cash prices indicate bubbles lasting much longer. Since theory suggests that prices for individual futures contracts are more likely to provide a clearer test of bubble components, the authors conclude there is little evidence that the spike in spring wheat prices to $25 per bushel in 2007-2008 was a bubble.

This paper is the first in the literature to examine the sensitivity of bubble testing to different types of data, sampling frequencies, and inference procedures.