Unstructured Method Research Articles

Finite element reverse time migration imaging in tunnels using an unstructured mesh

Wave field extrapolation is critical in reverse time migration (RTM). At present, wavefield extrapolation in RTM imaging for tunnels is mostly carried out via the finite difference method. However, complex tunnel models, such as those for karst and fault fracture zones, are constructed using regular grids with straight curves which can easily cause numerical dispersion and reduce imaging accuracy. In this study, the wavefield extrapolation for tunnel RTM was conducted using the finite element method, where an unstructured mesh is employed as the body-fitted partition in a complex model. The Poynting vector calculation equation suitable for the unstructured mesh finite element method was established to suppress low-frequency noise interference. The tunnel space was considered during the wavefield extrapolation to suppress mirror artefacts by using the flexibility of mesh generation. Finally, the influence of the survey layouts (one-sidewall and two-sidewall) on the tunnel imaging results was explored. The RTM results for a simple tunnel model with an inclined interface show that the method based on unstructured meshes can effectively suppress low-frequency noise and mirror artefacts, thus obtaining clearer imaging results. Also, the two-sidewall tunnel survey layout more accurately obtains the real position of the inclined interface ahead of the tunnel face. Complex tunnel numerical modelling and actual data migration results further illustrate the effectiveness of the finite element unstructured mesh method.

Expert predictions of changes in vegetation condition reveal perceived risks in biodiversity offsetting.

Biodiversity offsetting typically involves the trade of certain losses of habitat with uncertain future conservation benefits. Predicting the latter requires estimates of two outcomes; the biodiversity losses without conservation management (averted loss), and the biodiversity gains with conservation management (management gain). However, because empirical data to inform these estimates are limited, they are normally guided by expert opinion, often derived via unstructured methods without consideration of uncertainty. Here we used a structured elicitation with 29 experts to gather estimates of averted loss and management gain at offset sites. We used two methods; (i) experts estimated change in an aggregate biodiversity value (vegetation condition) and; (ii) experts provided probabilistic estimates of change for individual vegetation condition attributes, such as the richness and cover of plant growth forms. On average, experts predicted there would be only modest improvements with conservation management, yet uncertainty and variation among experts was large; in some cases, conservation benefits were not predicted. Estimates of change in vegetation condition suggested that benefits were from both averted loss and management gains and were thought to most likely arise in cases where starting condition was low to moderate. Similar patterns were observed for individual vegetation condition attributes, with management gains, relative to a reference, tending to be negatively correlated with starting value. Our study finds that: (i) on average, gains at offset sites are expected to be small, (ii) at many sites, experts do not believe gains can be obtained, and (iii) experts’ opinions can be divergent resulting in elevated levels of uncertainty. The potential for losses under conservation management highlights the need to: identify those components of biodiversity most likely to benefit from conservation management; better understand those situations when offset obligations are most likely to be met and conversely those situations with higher risk; and further develop offset mechanisms that encourage early or prior gains. These findings together with the global proliferation of biodiversity offsetting, provide a strong imperative to improve empirical data and investment in long-term, site-based monitoring of biodiversity outcomes at offset sites.

Optimal Runge–Kutta schemes for pseudo time-stepping with high-order unstructured methods

In this study we generate optimal Runge–Kutta (RK) schemes for converging the Artificial Compressibility Method (ACM) using dual time-stepping with high-order unstructured spatial discretizations. We present optimal RK schemes with between s=2 and s=7 stages for Spectral Difference (SD) and Discontinuous Galerkin (DG) discretizations obtained using the Flux Reconstruction (FR) approach with solution polynomial degrees of k=1 to k=8. These schemes are optimal in the context of linear advection with predicted speedup factors in excess of 1.80× relative to a classical RK4,4 scheme. Speedup factors of between 1.89× and 2.11× are then observed for incompressible Implicit Large Eddy Simulation (ILES) of turbulent flow over an SD7003 airfoil. Finally, we demonstrate the utility of the schemes for incompressible ILES of a turbulent jet, achieving good agreement with experimental data. The results demonstrate that the optimized RK schemes are suitable for simulating turbulent flows and can achieve significant speedup factors when converging the ACM using dual time-stepping with high-order unstructured spatial discretizations.

The Meaning of Business Success: Moslem Women Entrepreneur in Surakarta

This study aims to understand the meaning of business success for Moslem women entrepreneurs in Surakarta. The various roles attached to Moslem women and social complexity they faced, become the reason to conduct a study related Moslem women entrepreneurs in Surakarta holistically. This study is conducted using qualitative method under phenomenology approach. Informant is selected as research subject through purposive sampling technique based on the predetermined criteria. The data is collected for a year using in-depth interview and unstructured interview methods. Moslem women entrepreneurs in Surakarta interpret the success of business in the economic aspect that is related to the creation of business sustainability through the maximisation of business potential and asset growth. Then, the aspect of spirituality becomes the basis for Moslem women entrepreneurs to achieve self-improvement. So they also interpret the success of their business from non-economic aspects through the absence of selfishness, creating maslahah for family and society.

Blogging towards understanding: rethinking the notion of data

PurposeFrom the standpoint of a novice researcher, the author has examined how blogging as a literacy practice enables one to explore and understand self in relation to analysing data and making meaning. The purpose of this paper is to discuss how blogging can be used as a reflective and critical tool and explore the notion of blogging as transgressive, or stumble data.Design/methodology/approachThe theoretical underpinnings of blogging as a literate critical practice are congruent with the work of Freire. Thinking about research through this paradigm thus becomes transformative because it enables one to do data differently. This paper also considers and interrogates different approaches to the analysis of data, and frames blogging as a way to inquire more subjectively.FindingsIn this paper, blogging is represented as uncoded data; a concurrent and seemingly unstructured method of analysis. To this end, the definition of data is questioned in terms of what is legitimate, and what counts. Subjectivity puts blogging into a relevant context, as one’s positioning and experiences become a layered foundation upon which to understand one’s research more closely and meaningfully. Self-representation is deeply entwined with self-documentation, which can enable the identity of the writer/researcher to attain greater definition.Originality/valueFlirting with data in unconventional ways and inhabiting a space of unknowing enabled original thinking and creative processes to enter the research space. Reading and writing are framed as methods of inquiry and analysis that are separate, or an alternative, to coding data.

Achieving pervasive fracture and fragmentation in three-dimensions: an unstructuring-based approach

There are few methods capable of capturing the full spectrum of pervasive fracture behavior in three-dimensions. Throughout pervasive fracture simulations, many cracks initiate, propagate, branch and coalesce simultaneously. Because of the cohesive element method framework, this behavior can be captured in a regularized manner. However, since the cohesive element method is only able to propagate cracks along element facets, a poorly designed discretization of the problem domain may introduce artifacts into the simulated results. To reduce the influence of the discretization, geometrically and constitutively unstructured means can be used. In this paper, we present and investigate the use of three-dimensional nodal perturbation to introduce geometric randomness into a finite element mesh. We also discuss the use of statistical methods for introducing randomness in heterogeneous constitutive relations. The geometrically unstructured method of nodal perturbation is then combined with a random heterogeneous constitutive relation in three numerical examples. The examples are chosen in order to represent some of the significant influencing factors on pervasive fracture and fragmentation; including surface features, loading conditions, and material gradation. Finally, some concluding remarks and potential extensions are discussed.

Метод построения неструктурированных сеток

Метод построения неструктурированных сеток

Numerical Simulation of Thermoacoustic Wave Induced by Thermal Effects by Using Discontinuous Galerkin Method

This paper describes a numerical model based on discontinuous Galerkin method for thermoacoustic investigation. Numerical investigation was conducted to study the behaviour of thermoacoustic wave propagations induced by thermal effects in 2-dimensional enclosure. The compressible Navier-Stokes equations are used as the governing equations. The spatial domain was discretized by using unstructured discontinuous Galerkin method and the explicit fourth-order Runge-Kutta was used to integrate the temporal domain. The accuracy of the numerical results was assessed against other numerical methods and linear solutions. The comparisons with linear solutions show excellent agreement and comparisons with flux corrected transport (FCT) method show fair agreement.

Policy making for global food security in a volatile, uncertain, complex and ambiguous (VUCA) world

PurposeThis paper aims to explain the uncertainties associated with food security and, in doing so, classifies them within the context of volatility, uncertainty, complexity and ambiguity (VUCA). In using this lens to frame the challenges of food security, the viewpoint proffers the need to be even more sensitive to heightened levels of uncertainty and highlights the need of governments to be prepared to meet a wider variety of external forces, risks, opportunities and threats to mitigate food insecurity.Design/methodology/approachThis research constructs a novel morphology of food security and food waste policy futures based upon a range of scenario types based on contextual narratives relating to constraint, collapse, growth and transformation. In doing so, offering a representation that suggests order, complexity and chaos occur across a range of four domains of interaction: known (repeatable cause and effect); knowable (cause and effect separated over time); complex (cause and effect are unique and non-repeatable); and chaos (no cause and effect relationship perceivable). This orientation is represented in the form of a novel morphology that can be used to support decision-making and policymaking/consideration.FindingsThe authors have presented and identified a combination of a structured and unstructured methods to develop and hence classify a range of food security scenarios. Using the VUCA worldview and classification, the authors subsequently identify seven underlying and seven United Nations (UN) Sustainable Development Goals (SDG)-derived factors, which when combined with the Institute for the Future (IFTF) four food security scenarios in a pairwise manner led to the generation of a further 16 subsequent VUCA-inspired scenarios composed within a morphological grid. These were subsequently reclassified against three sets of stakeholders and then finally mapped to the Cynefin framework as a set of ten scenarios to show the potential of making greater sense of the VUCA nature of food security.Practical implicationsThe paper proposes a novel conceptual approach to framing and understanding the wider holistic aspects of explaining and providing foresight to the complexities of food security. Hence, this paper provides policymakers with two contrasting, yet complementary, food security scenario planning techniques (VUCA and Cynefin), which envelope 16 narrative food security scenarios which can be used with stakeholders and advocacy groups in facilitating discussion about complex, messy and “wicked” interlinkages within the food security domain.Originality/valueThis is the first time in the extant literature that a combination of structured and unstructured, problem-based versus mess-based, contrasting perspectives have been brought together and developed, with the intention of creating a normative family or portfolio of narrative-driven food security scenarios. The authors present and extend four existing scenarios from the extant food security literature, and subsequently, through interpreting these scenarios via a dual and combined lens (notably using UN SDG and VUCA elements), a grid of alternative food security scenarios is produced. By then using applying the Cynefin complexity framework to these new configurations, a thematic categorisation of alternative futures is presented, which may aid policy and decision-makers when considering this topic.

A Utilização do Protocolo Verbal Think Aloud para Rastreamento de Processos em Pesquisas Sobre a Tomada de Decisão do Consumidor

Este artigo tem como objetivo ilustrar didaticamente a utilizao e fomentar uma reflexo a respeito da utilizao do mtodo de protocolo verbal think aloud para rastreamento de processos em pesquisas sobre a tomada de deciso do consumidor. Diferentemente de mtodos de entrada-sada, cujo uso est consolidado nas pesquisas experimentais sobre o comportamento do consumidor, os mtodos utilizados para rastreamento de processos, entre eles o protocolo verbal think aloud, enfatizam o teste de modelos e hipteses por meio de dados processuais. Definido como mtodo simultneo e no-estruturado de coleta de dados verbais realizado durante a execuo de uma tarefa, cujo procedimento consiste em solicitar aos pesquisados que manifestem em voz alta seus pensamentos, sem, no entanto, interpret-los, o protocolo verbal think aloud defendido por pesquisadores da rea de julgamento e tomada de deciso uma importante fonte de dados em pesquisas a respeito do processo decisrio individual. De acordo com o objetivo geral proposto, o trabalho apresenta uma descrio procedimentos necessrios para a operacionalizao do mtodo think aloud para rastreamento de processos e detalha dois estudos que utilizaram protocolos verbais para investigar a tomada de deciso do consumidor do consumidor publicados em peridicos de marketing.

Development of unstructured mesh-based numerical method for sodium–water reaction phenomenon in steam generators of sodium-cooled fast reactors

ABSTRACTWhen pressurized water or vapor leaks from a failed heat transfer tube in a steam generator of sodium-cooled fast reactors, a high-velocity and high-temperature jet with sodium–water chemical reaction may cause wastage on the adjacent tubes. For safety assessment of the steam generator, a computational fluid dynamics code called SERAPHIM calculating compressible multicomponent multiphase flow with sodium–water chemical reaction has been developed. The original SERAPHIM code is based on the finite difference method. In this study, unstructured mesh-based numerical method for the SERAPHIM code was developed to advance a numerical accuracy for the complex-shaped domain including multiple heat transfer tubes. Numerical analysis of an underexpanded jet experiment was performed as part of validation of the unstructured mesh-based SERAPHIM code. The calculated pressure profile showed good agreement with the experimental data. To investigate the effect of the introduction of the unstructured mesh and to confirm applicability of the numerical method for the actual situation, water vapor discharging into liquid sodium was analyzed. The calculated behavior of the reacting jet agreed with the previous experimental knowledge. It was demonstrated that the proposed numerical method could be applicable to evaluation of the sodium–water reaction phenomenon.

Indigenous knowledge of the use of medicinal plants in the North-West of Morocco and their biological activities

IntroductionThis study is the first ethnopharmacological survey that investigates the traditional uses of medicinal plants in the province of Ouezzane (North-West of Morocco) as well as the indigenous knowledge related to the use of this natural resource in healthcare by the local population in order to preserve and protect this invaluable inheritance. We aimed also to reveal the in vitro pharmacological activities of some reported medicinal plants in this study. MethodsIn the survey, 113 informants (local inhabitants and herbalists) were interviewed using the semistructured and unstructured methods and using a stratified sampling technique. Data collected were analyzed calculating three quantitative parameters: Use Value (UV), Fidelity Level (FL) and Informant Consensus Factor (ICF). Pharmacological properties of some reported medicinal plants were evaluated. The antioxidant activity was estimated by the DPPH radical scavenging assay and the antibacterial activity was evaluated using agar well diffusion assay and microtitration method. ResultsThe results showed that 11% of the local population use traditional medicine, against 67% who use both traditional and modern medicine. The ethnomedicinal uses of 44 medicinal species representing 28 families were reported on. Lamiaceae were the most representative and include 32% of the identified species. The medicinal use revealed that leaves are the most used part of plants to prepare drugs, the decoction is the most widely used preparation method and remedies are often administered orally. The highest value of MUV was obtained for Origanum compactum Benth. (MUV=0.62) and Myrtus communis L. (MUV=0.52). In addition, In addition, the highest value of FL was recorded for Origanum compactum Benth. (100%), Myrtus communis L. (93.50%) and Arbutus unedo L. (93.50%). While, while the highest value of ICF was mentioned for respiratory system diseases (ICF=0.69), dermocosmetology (ICF=0.68), digestive system problems (ICF=0.63) and nervous system disorders (ICF=0.69). Plant extracts and essential oils showed important antibacterial properties against pathogenic strains and significant antioxidant capacities. ConclusionsThe ethnopharmacological data documented in this work revealed the use of medicinal plants in North-West of Morocco to fight against diseases. Therefore, efforts are needed for improving the level of the documentation, the conservation and standardisation of these species, and to preserve the transmission of traditional healing knowledge. Also, further studies testing other plant extracts in other pharmacological systems are needed to explore the scientific biological potential of these plants.

Constraining Knowledge: Traditions and Rules that Limit Medical Innovation

ABSTRACTNon-medical innovation has become progressively more open, harnessing the enterprise and creativity of a variety of players (including venturesome consumers) and relying on diverse structured and unstructured methods to generate and select advances. Medical innovation, however, remains more closed and regimented because of age-old traditions, reinforced by modern funding and regulatory practices that require the costly ex-ante demonstration of efficacy. These practices, which seek to replicate those of the natural sciences, militate against the pluralistic creation and use of medical innovations and suppress ad-hoc, accretive—and potentially life-saving—advances.

有限要素法に基づく異材接合体の特異応力場解析に対する非構造三角形メッシュ生成法の提案

有限要素法に基づく異材接合体の特異応力場解析に対する非構造三角形メッシュ生成法の提案

A control volume finite element method with spines for solutions of fractional heat conduction equations

ABSTRACTThe focus of this paper is the numerical solution of space-fractional heat conduction equations. Typical numerical treatments for fractional diffusion equations (FDEs) are constructed to function on structured grids and cannot be readily applied to problems in arbitrarily shaped domains. Presented is an unstructured control volume finite element method for the solution of FDEs in non-Cartesian domains. This method approximates the fractional derivative flux at given integration points with a weighted sum of gradients along orthogonal spines. Accuracy and utility of the approach are demonstrated by solution of one- and two-sided FDEs in rectangular and cylindrical domains.

Assessing Symptoms in Adolescents Following Sport-Related Concussion: A Comparison of Four Different Approaches

This study compared post-concussion symptom endorsements on the Post-Concussion Symptom Scale (PCSS) between a clinical open-ended interview, clinician-guided PCSS, parent-report PCSS, and computer-based PCSS in youth athletes with sport-related concussion (SRC). Participants included 54 patients aged 13–17 years (M = 15.19, SD = 1.29, 51.8% male) with a diagnosed SRC seen at a concussion clinic. Participants were administered a computer-based version (COMP) of the PCSS followed by clinical open-ended symptom interview (OPEN) and clinician-guided PCSS (GUIDED). Participants’ parents concurrently and independently endorsed their children's symptoms by completing the PCSS in the waiting room (PARENT). Total number of symptoms reported and total symptom severity score were analyzed and compared across the four PCSS administration methods. Results revealed significantly lower total number of symptoms for OPEN compared to GUIDED (p = .002), PARENT (p < .001), and COMP (p = .006); and significantly lower total severity score for OPEN compared to GUIDED (p = .04) and PARENT (p < .001). These data support using the PCSS as a structured method of assessing post-concussion symptoms and question the utility of unstructured interview methods for assessing symptoms in youth athletes with SRC.

Case Study of Functional Neurological Disorder (Aphonic)

Mr. S (initial instead of real name), the clients, age was 23 years. He visited to the clinic along with his cousin. His cousin informed that client is suffering from speech disorder while his medical reports are clear. His cousin also mentioned about his aggressive behaviour, disturbed sleep, and use of drugs. The client was not able to answer vocally so his answers were in written form. After that, further informations were collected from his parents and family. Pre morbid history was taken in six days from him (in written form) and from his parents. Unstructured method was used for data collecting. After data collecting, client was diagnosed by “Functional Neurological Disorder (Aphonic).” He was fully recovered after ninety sessions.

An Unstructured Road Detection Method with Multi-Environmental Adaptability

An Unstructured Road Detection Method with Multi-Environmental Adaptability

AN EMPIRICAL METHOD FOR FAST PREDICTION OF RAREFIED FLOW FIELD AROUND A VERTICAL PLATE

Numerical study is conducted to investigate the effects of free-stream Knudsen (Kn) number on rarefied flow field around a vertical plate employing an unstructured DSMC method, and an empirical method for fast prediction of flow-field structure at different Kn numbers in a given inflow velocity is proposed. First, the flow at a velocity 7500m/s is simulated using a perfect-gas model with free-stream Kn changing from 0.035 to 13.36. The flow-field characteristics in these cases with varying Kn numbers are analyzed and a linear-expansion phenomenon as a function of the square of Kn is discovered. An empirical method is proposed for fast flow-field prediction at different Kn based on the least-square-fitting method. Further, the effects of chemical reactions on flow field are investigated to verify the applicability of the empirical method in the real gas conditions. Three of the cases in perfect-gas flow are simulated again by introducing five-species air chemical module. The flow properties with and without chemical reactions are compared. In the end, the variation of chemical-reaction flow field as a function of Kn is analyzed and it is shown that the empirical method are also suitable when considering chemical reactions.

An effective 3D leapfrog scheme for electromagnetic modelling of arbitrary shaped dielectric objects using unstructured meshes

In computational electromagnetics, the advantages of the standard Yee algorithm are its simplicity and its low computational costs. However, because of the accuracy losses resulting from the staircased representation of curved interfaces, it is normally not the method of choice for modelling electromagnetic interactions with objects of arbitrary shape. For these problems, an unstructured mesh finite volume time domain method is often employed, although the scheme does not satisfy the divergence free condition at the discrete level. In this paper, we generalize the standard Yee algorithm for use on unstructured meshes and solve the problem concerning the loss of accuracy linked to staircasing, while preserving the divergence free nature of the algorithm. The scheme is implemented on high quality primal Delaunay and dual Voronoi meshes. The performance of the approach was validated in previous work by simulating the scattering of electromagnetic waves by spherical 3D PEC objects in free space. In this paper we demonstrate the performance of this scheme for penetration problems in lossy dielectrics using a new averaging technique for Delaunay and Voronoi edges at the interface. A detailed explanation of the implementation of the method, and a demonstration of the quality of the results obtained for transmittance and scattering simulations by 3D objects of arbitrary shapes, are presented.