Definition Of Shape Research Articles

Form finding of continua shells with lattice spring models

The use of spring cells as an alternative to finite element method (FEM) analysis of deformable continua has numerous advantages, such as its discrete representation and unidimensional stress states.This paper presents an innovative alternative approach to the continua FEM analysis, based on a new discrete model algorithm of bar elements framing a triangulated grid - lattice spring model. A non-uniform optimized thickness distribution, in both continua and discrete models, was implemented. This novel feature is a vital aspect to the optimization of the final shape.Two discrete models were developed, the classic/stiffness model and the innovative/flexibility model, that differ by the calculatory cross-section areas assigned to the bars of the cell. Results demonstrate that the latter performs better, not only for the independency of the mesh quality, but also for the approximation of the results (when compared to the continua model). An incremental shape definition algorithm is also applied to keep the horizontal coordinates unchanged.This new discrete approach led to a structural model that is easier and faster to program than FE method. It is also very accurate, since the final shapes obtained by the continuum method and the discrete methods are practically coincident.

Interactive design and variation of hull shapes: pros and cons of different CAD approaches

Modern paradigms to design complex engineering systems focus on interactive approaches able to simultaneously handle results from multidisciplinary applications. Keeping this in mind and considering that from a ship design perspective the definition of a hull shape is the first step of the whole design process, a reliable computer aided design model for shape representation and morphing becomes a key feature to navigate trough the design spiral. The proposed research focuses on the comparison of two different approaches to handle hull shape variations, namely the fully parametric model and a non-parametric method relying on the free form deformation technique. The comparison is developed considering both the easiness of building the shape of the reference model with its transformations laws and the resulting number of free design variables. The two methods are analyzed in the light of attainable hull shape variation in two design and modification test cases. The first is limited to the bulbous bow of a conventional hull while the second focuses on the whole surface of a fast, displacement, round-bilge hull.

Regression Modelling of Shape Through Triangulation

Recalling the definition of shape as a point on hyper-sphere, proposed by Kendall, the regression model is studied in this paper. In order to simplify the modeling, the triangulation via two landmarks is proposed. The triangulation not only simplifies the regression modelling of the shapes but also provides straightforward computation procedure to reconstruct geometrical structure of the objects. Novelty of the proposed method in this paper is on using the predictor variable, based upon the shape, which suitably describes the geometrical variability of the response. The comparison and evaluation of the proposed methods with the full Procrustes matching through the mean square error criteria are done. Application of two models for the configurations of rat skulls is investigated.

New statistical methods for the comparison and characterization of particle shape

AbstractThis paper presents novel methods for robust statistical testing of particle shape data. Shape (the relative lengths of three orthogonal axes) is a key property of sedimentary particles, providing information on provenance, transport history and depositional environment. However, the usefulness of shape data, including the ability to make robust comparisons between samples, has been constrained by the absence of a satisfactory definition of the mean shape for a sample of particles. Such a definition is proposed and used to develop confidence regions for the population mean shape using both parametric (theoretical) and computational (bootstrap) methods. These techniques are based on a transform that permits multivariate statistical methods for the analysis of compositional data to be extended to shape. These techniques are validated with reference to a dataset of 169 clast samples and found to perform well. A statistical test on the mean – using the multivariate extension of Student's t‐test, Hotelling's T2 – is presented. The benefits of the methods presented are demonstrated with reference to a case study. © 2019 John Wiley & Sons, Ltd.

Approaching Impact Meaningfully in Medical Education Research.

Medical education research faces increasing pressure to demonstrate impact and utility. These pressures arise amidst a climate of accountability and within a culture of outcome measurement. Conventional metrics for assessing research impact such as citation analysis have been adopted in medical education, despite researchers' assertion that these quantitative measures insufficiently reflect the value of their work. Every knowledge community has its own definitions of what counts as knowledge, how that knowledge should be produced, and how the quality of that knowledge production should be evaluated. Definitions of impact and knowledge shape and constrain researchers' foci and endeavors. Therefore, metrics that meaningfully evaluate the knowledge outputs of researchers need to be defined within each field. It is time for medical education research, as a field, to examine how to measure research impact and carefully consider the broader implications these measures may have. The authors discuss developments in research metrics more broadly, then critically examine impact metrics currently used in the medical education field and propose alternatives to more meaningfully track and represent impact in medical education research. Grey metrics and narrative impact stories to more fully capture the richness and nuanced nature of impact in medical education research are introduced. The authors advocate for a continual examination of how impact is defined, eschewing unquestioned use of conventional metrics. A new conversation is needed, as well as a research agenda to help medical education conceptualize and study metrics more appropriate for the field.

Second-generation molecular subgrouping of medulloblastoma: an international meta-analysis of Group 3 and Group 4 subtypes

In 2012, an international consensus paper reported that medulloblastoma comprises four molecular subgroups (WNT, SHH, Group 3, and Group 4), each associated with distinct genomic features and clinical behavior. Independently, multiple recent reports have defined further intra-subgroup heterogeneity in the form of biologically and clinically relevant subtypes. However, owing to differences in patient cohorts and analytical methods, estimates of subtype number and definition have been inconsistent, especially within Group 3 and Group 4. Herein, we aimed to reconcile the definition of Group 3/Group 4 MB subtypes through the analysis of a series of 1501 medulloblastomas with DNA-methylation profiling data, including 852 with matched transcriptome data. Using multiple complementary bioinformatic approaches, we compared the concordance of subtype calls between published cohorts and analytical methods, including assessments of class-definition confidence and reproducibility. While the lowest complexity solutions continued to support the original consensus subgroups of Group 3 and Group 4, our analysis most strongly supported a definition comprising eight robust Group 3/Group 4 subtypes (types I–VIII). Subtype II was consistently identified across all component studies, while all others were supported by multiple class-definition methods. Regardless of analytical technique, increasing cohort size did not further increase the number of identified Group 3/Group 4 subtypes. Summarizing the molecular and clinico-pathological features of these eight subtypes indicated enrichment of specific driver gene alterations and cytogenetic events amongst subtypes, and identified highly disparate survival outcomes, further supporting their biological and clinical relevance. Collectively, this study provides continued support for consensus Groups 3 and 4 while enabling robust derivation of, and categorical accounting for, the extensive intertumoral heterogeneity within Groups 3 and 4, revealed by recent high-resolution subclassification approaches. Furthermore, these findings provide a basis for application of emerging methods (e.g., proteomics/single-cell approaches) which may additionally inform medulloblastoma subclassification. Outputs from this study will help shape definition of the next generation of medulloblastoma clinical protocols and facilitate the application of enhanced molecularly guided risk stratification to improve outcomes and quality of life for patients and their families.

Students\u2019 collaborative decision-making processes in defining and classifying quadrilaterals: a semiotic/dialogic approach

In this paper, we take a semiotic/dialogic approach to investigate how a group of UK 12–13-year-old students work with hierarchical defining and classifying quadrilaterals. Through qualitatively analysing students’ decision-making processes, we found that the students’ decision-making processes are interpreted as transforming their informal/personal semiotic representations of “parallelogram” (object) to more institutional ones. We also found that students’ decision-making was influenced by their inability to see their peers’ points of view dialogically, i.e., requiring a genuine inter-animation of different perspectives such that there is a dialogic switch, and individuals learn to see the problem “as if through eyes of another,” in particular collectively shared definitions of geometrical shapes.

V01-10 NON-BIOLOGICAL 3D PRINTED SIMULATOR FOR PERCUTANEOUS NEPHROLITHOTRIPSY

INTRODUCTION AND OBJECTIVES:The aim of this study was to develop a non-biological 3D printed simulator for percutaneous nephrolithotripsy (PCNL) training and preoperative planning, which would allow doctors to master new skills and perform all stages of the procedure under ultrasound and fluoroscopy guidance.METHODS:A 3D model was constructed based on data of multispiral computed tomography (MSCT) of patients with kidney stones. The simulator consists of two parts: a non-biological 3D printed soft model of the kidney with reproduced intrarenal vascular and collecting systems and a printed 3D model of a human body. With the use of fluoroscopy and ultrasound, PCNL was performed in the interventional radiology operating room.To determine the utility of this model, five residents of the 3D Model group (group A) passed a questionnaire (psychometric Likert scale) in which it was proposed to evaluate their skills in understanding of collecting system's anatomy, definition of stone localization, shape and positio...

Investigations of Shape Definition and Aerodynamics Analysis Methods for Three-Dimensional Aerodynamic Shape Optimization

Investigations of Shape Definition and Aerodynamics Analysis Methods for Three-Dimensional Aerodynamic Shape Optimization

Effects of Temperature on the Shape and Symmetry of Molecules and Solids.

Despite its undeniable problems from a philosophical point of view, the concept of molecular structure, with attributes such as shape and symmetry, directly borrowed from the description of macroscopic objects, is nowadays central to most of the chemical sciences. Descriptions such as "the tetrahedral carbon atom" or "octahedral coordination complexes" are widely used as much in elementary textbooks as in the most up-to-date research articles. The definition of molecular shape is, however, not as simple as it might seem at first sight. Molecules don't behave as macroscopic objects do, and the arrangement of atoms within a molecule changes continuously due to the incessant motion of its constituent particles, nuclei, and electrons. How are molecular shape and symmetry affected by this thermal motion? In this Minireview, we introduce the language of continuous symmetry measures as a new tool to quantitatively describe the effects of temperature on molecular shape and symmetry, enriching in this way the set of molecular descriptors that might be used in the establishment of new empirical structure-property relations, of great interest in concomitant areas such as medicinal chemistry or materials science.

An Investigation on the Loss Generation Mechanisms Inside Different Centrifugal Compressor Volutes for Turbochargers

In centrifugal compressor design, the volute plays a key role in defining the overall efficiency and operating range of the stage. The flow at the impeller outlet is indeed characterized by a high kinetic energy content, which is first converted to potential energy in the diffuser downstream. The compressed gas is then collected by the volute at the cylindrical outlet section of the diffuser and directed to the intake piping, possibly with a further pressure recovery to enhance the stage performance. Due to the high flow speed at the volute inlet, the capability of ensuring the lowest amount of total pressure loss is pivotal to prevent a detriment of the machine efficiency. Moreover, the flow conditions change when the volute operates far from its design point: at mass flow rates lower than the design one, the flow becomes diffusive, while at higher mass flow rates the fluid is accelerated, thus leading to different loss-generation mechanisms. These phenomena are particularly relevant in turbocharger applications, where the compressor needs to cover a wide functioning range; moreover, in these applications, the definition of the volute shape is often driven also by space limitations imposed by the vehicle layout, leading to a variety of volute types. The present paper reports an analysis on the sources of thermodynamic irreversibilities occurring inside different volutes applied to a centrifugal compressor for turbocharging applications. Three demonstrative geometrical configurations are analyzed by means of three-dimensional (3D) numerical simulations using common boundary conditions to assess the overall volute performance and different loss mechanisms, which are evaluated in terms of the local entropy generation rate. The modification of the loss mechanisms in off-design conditions is also accounted for by investigating different mass flow rates. It is finally shown that the use of the entropy generation rate for the assessment of the irreversibilities is helpful to understand and localize the sources of loss in relation to the various flow structures.

The use of function-driven shape definition method and GRA–EMM-based Taguchi method to multi-criterion blade preform optimization

For a blade with complex shape, preform design plays an important part in the quality of an achieved part in the forging process. So many optimization methods were developed in many researches to obtain an optimal preform. However, in these researches, they lack accuracy and efficiency in defining preform shape, and there is no systematical strategy of implementing multi-criterion optimization processes. In order to overcome these defects, a function-driven shape definition method was proposed in this paper. This method can transform geometrical shape into numerical variables which define geometrical shape easily and can be used in mathematical functions in such methods as Taguchi method and response surface method. Besides, a novel Taguchi method coupling with gray relational analysis (GRA) and entropy measurement method (EMM) was developed, which provides a systematic way of optimizing preforms from the perspective of multi-criterion. In this method, GRA transforms multiple objectives into gray relational grade and EMM determines the weights of objectives. Finally, these two methods were applied in blade preform optimization to validate their effectiveness and efficiency. The results showed that the optimized blade was decreased by 16.6% in strain variance and by 20.2% in total load.

An integrated framework for multi-criteria optimization of thin concrete shells at early design stages

Thin shells are crucially dependent on their shape in order to obtain proper structural performance. In this context, the optimal shape will guarantee performance and safety requirements, while minimizing the use of materials, as well as construction/maintenance costs.Thin shell design is a team-based, multidisciplinary, and iterative process, which requires a high level of interaction between the various parties involved, especially between the Architecture and Engineering teams. As a result of technological development, novel concepts and tools become available to support this process. On the one hand, concepts like Integrated Project Delivery (IPD) show the potential to have a high impact on multidisciplinary environments such as the one in question, supporting the early decision-making process with the availability of as much information as possible. On the other hand, optimization techniques and tools should be highlighted, as they fit the needs and requirements of both the shell shape definition process and the IPD concept. These can be used not only to support advanced design stages, but also to facilitate the initial formulation of shape during the early interactions between architect and structural engineer from an IPD point of view.This paper proposes a methodology aimed at enhancing the interactive and iterative process associated with the early stages of thin shell design, supported by an integrated framework. The latter is based on several tools, namely Rhinoceros 3D, Grasshopper, and Robot Structural Analysis. In order to achieve full integration of the support tools, a custom devised module was developed, so as to allow interoperability between Grasshopper and Robot Structural Analysis. The system resorts to various technologies targeted at improving the shell shape definition process, such as formfinding techniques, parametric and generative models, as well as shape optimization techniques that leverage on multi criteria evolutionary algorithms. The proposed framework is implemented in a set of fictitious scenarios, in which the best thin reinforced concrete shell structures are sought according to given design requirements. Results stemming from this implementation emphasize its interoperability, flexibility, and capability to promote interaction between the elements of the design team, ultimately outputting a set of diverse and creative shell shapes, and thus supporting the pre-design process.

Generation of planar tensegrity structures through cellular multiplication

Tensegrity structures are frameworks in a stable self-equilibrated prestress state that have been applied in various fields in science and engineering. Research into tensegrity structures has resulted in reliable techniques for their form finding and analysis. However, most techniques address topology and form separately. This paper presents a bio-inspired approach for the combined topology identification and form finding of planar tensegrity structures. Tensegrity structures are generated using tensegrity cells (elementary stable self-stressed units that have been proven to compose any tensegrity structure) according to two multiplication mechanisms: cellular adhesion and fusion. Changes in the dimension of the self-stress space of the structure are found to depend on the number of adhesion and fusion steps conducted as well as on the interaction among the cells composing the system. A methodology for defining a basis of the self-stress space is also provided. Through the definition of the equilibrium shape, the number of nodes and members as well as the number of self-stress states, the cellular multiplication method can integrate design considerations, providing great flexibility and control over the tensegrity structure designed and opening the door to the development of a whole new realm of planar tensegrity systems with controllable characteristics.

Definition of Wingtip Devices Shape and Dimensions for a Subsonic Airliner

The results of flow field numerical simulation on the typical wing-body prototype of the modern DLR-F4 airliner under sub- and transonic compressible air flow are presented. Using the DLR-F4 CAD model, the effect of the wingtip end plate area and of the cant angle of a typical Whitcomb winglet is studied. The dependencies of the model lift-to-drag ratio increment on the flat wingtip end plate relative area and on the cant angle of an airfoil Whitcomb winglet are obtained. The concept of an elliptic winglet with a variable cant angle that similar to the winglet used on Airbus A350 is studied. A technique is developed for solving the multi-parameter design optimization task for the Whitcomb winglet, taking the maximum lift-to-drag ratio of the wing as a criterion for optimization.

Urine flow rate curve shapes and their descriptors.

To review the descriptors and definitions of urine flow rate curve shape with a view to promoting greater clarity and to propose standard terms METHODS: A search was made in the PubMed and ICS standardization documents on urine flow rate curve shape. The flow shape descriptors and their definitions are summarized and presented. "Normal" was widely used for describing a bell-shaped flow curve, and "plateau" was mostly used where the ICS describe "constrictive" flow shape. The use of shape descriptors "fluctuating," "compressive," "tower-shaped," and "intermittent" varied in the literature. This survey provides an overview of flow shape descriptors and their definitions. We suggest it is clearer to use only descriptors that describe shape alone, that is, normal, fluctuating, intermittent, and plateau, with comments on symmetry and Qmax .

Design guidelines as ideation tools – a user study on exploring the subjectivity of unit-cell design guidelines

A user study is designed and carried out to evaluate the subjectivity of four unit-cell design (UCD) guidelines and demonstrate how inexperienced designers re-design novel unit-cells using the guidelines as ideation tools. UCD guidelines outline a set of instructions on changing important parameters to guide engineers in intentionally redesigning shapes and topologies for unit-cells when considering a desired structural behavior. The subjectivity of the guidelines is evaluated based on the similarities among modified unit-cells as a result of applying guidelines to initial unit-cells. The metric to measure similarity qualitatively is based on topology and shape definitions. The results show there are similarities among the modified unit-cells; however, two guidelines led to generate more diverse modified unit-cells. Furthermore, the effectiveness of the guidelines is demonstrated by conducting comparative simulation studies on the hexagonal honeycomb unit-cell and top modified unit-cells for each guideline. The results of this study demonstrate the guidelines can be used as ideation tools for the conceptual design of novel unit-cells while the novel unit-cells fulfill a conceptual definition of creativity.

Beyond Participation: Politics, Incommensurability and the Emergence of Mental Health Service Users\u2019 Activism in Chile

Although the organisation of mental health service users and ex-users in Latin America is a recent and under-researched phenomenon, global calls for their involvement in policy have penetrated national agendas, shaping definitions and expectations about their role in mental health systems. In this context, how such groups react to these expectations and define their own goals, strategies and partnerships can reveal the specificity of the “user movement” in Chile and Latin America. This study draws on Jacques Rancière’s theorisation of “police order” and “politics” to understand the emergence of users’ collective identity and activism, highlighting the role of practices of disengagement and rejection. It is based on interviews and participant observation with a collective of users, ex-users and professionals in Chile. The findings show how the group’s aims and self-understandings evolved through hesitations and reflexive engagements with the legal system, the mental health system, and wider society. The notion of a “politics of incommensurability” is proposed to thread together a reflexive rejection of external expectations and definitions and the development of a sense of being “outside” of the intelligibility of the mental health system and its frameworks of observation and proximity. This incommensurability problematises a technical definition of users’ presence and influence and the generalisation of abstract parameters of engagement, calling for approaches that address how these groups constitute themselves meaningfully in specific situations.

On the construction of hourly price forward curves for electricity prices

There are several approaches in the literature for the derivation of price forward curves (PFCs) which distinguish among each other by the procedure employed for the derivation of seasonality shapes, smoothing technique and by the design of the optimization procedure. However, a comparative study to highlight the strengths and weaknesses of different methods is missing. For the construction of PFCs we typically incorporate the information about market expectation from the observed futures prices and the deterministic seasonal effects of electricity prices. In most existing approaches, the seasonality shape is fitted to historically observed spot prices, and it is an exogenous input to the optimization procedure. As seasonal effects on electricity prices differ between markets, our model allows a more general and flexible definition of the seasonality shape. In this study, we propose an alternative calibration procedure for the seasonality shape, where the level of futures as well as historical spot prices are simultaneously taken into account in a joint optimization approach. We discuss comparatively the features of existing methods for PFCs, and highlight the advantages of our optimization procedure.

Building energy performance assessment using volatility change based symbolic transformation and hierarchical clustering

This paper presents the development of a symbolic transformation based strategy with interpretability and visualisation for building energy performance assessment. The strategy was developed using shape definition language based symbolic transformation and hierarchical clustering. Advanced visualisation techniques including dendrogram, heatmap and calendar view were used to assist in understanding building energy usage behaviours. A comparison of this proposed strategy with a Symbolic Aggregate approXimation (SAX) based strategy was also performed. The performance of the proposed strategy was tested and evaluated using the three-year hourly heating energy and electricity usage data of a higher education building. The result demonstrated that the proposed strategy can identify distinct building energy usage behaviours. The visualisation techniques used also assisted the information discovery process. The discovered information helped to understand building energy usage patterns. The comparison of the proposed strategy with the SAX based strategy showed that the proposed strategy outperformed the SAX based strategy for the case building tested in terms of the variations in building energy usage. This proposed strategy can also be potentially used to evaluate the operational performance of building heating, ventilation and air-conditioning (HVAC) systems.