Geometric Components Research Articles

Generalized Geometry Projection: A Unified Approach for Geometric Feature Based Topology Optimization

Structural topology optimization has seen many methodological advances in the past few decades. In this work we focus on continuum-based structural topology optimization and more specifically on geomet- ric feature based approaches, also known as explicit topology optimization, in which a design is described as the assembly of simple geometric components that can change position, size and orientation in the con- sidered design space. We first review various recent de- velopments in explicit topology optimization. We then describe in details three of the reviewed frameworks, which are the Geometry Projection method, the Moving Morphable Components with Esartz material method

CHOPPI: A Particle In Cell code for ion beam transport through beam chopper : A demonstration with experiments

A simulation package employing a Particle in Cell (PIC) method is developed to study a high current beam transport through the chopper system designed for producing pulsed ion beams at low energies. This package includes subroutines, which are well suited for high current beam transport dominated by space-charge with a complete 6-dimensional phase-space description including simultaneous dynamics of multiple ion species and electrons. The discretized form of the Poisson equation is generalized to include irregular boundary conditions required to simulated curved or irregular geometric components. In the following paper, the capabilities of CHOPPI are demonstrated through comparison with experimental results from low energy ion beam transport.

Conceptual Design of Spacesuit Hard Hip Joint

Spacesuit hip joint plays an important role on astronaut activities, such as planetary walking and surveying. This paper proposes a conceptual design of hard hip joint in consideration of the coupling effect of spacesuit hip joint and astronaut thigh. Firstly, lower extremity activities are introduced to illustrate the mobility of hard hip joint, such as walking, kneeing, and abduction. A conceptual design of hard hip joint is explained in detail, including geometric structure, components, design parameters, and mechanism models. Secondly, a 3-linkage coupling mechanism model is built up by synthesizing that conceptual design of hard hip joint. An equiangular dual-perpendicular representation method is brought out to parameterize that mechanism model of hard hip joint. Particularly, four geometric constraints are, respectively, given out to avoid impact between the hip joint and the thigh and to ensure the continuity of thigh motion. Finally, motion equations of hip joint parts are established by using coordinate transformation and vector representation. A case study is conducted to verify the correctness of the proposed representation method and that coupling mechanism model.

Numerical and Experimental Studies of Labyrinth Seal Aeroelastic Instability

Abstract A labyrinth seal is commonly used to decrease the flow leakage loss between rotating and static components in aero engines. It is susceptible to aeroelastic instability because of its low stiffness. The aim of this study was to establish methods to predict and suppress it effectively. To achieve this, both numerical and experimental investigations are conducted using ansyscfx and ansys mechanical. These solvers are coupled to simulate the flutter precisely. Also, to assess the accuracy of the simulation qualitatively and quantitatively, a test rig is built. In the first part of this study, the accuracy of the numerical method is confirmed for several test cases with different seal clearance variations. Flutter inception is evaluated in detail for various pressure ratios and rotation speeds. The numerical results show good agreement with the experimental results. It is also confirmed that the aeroelastic instability is very sensitive to the seal clearance variations. These results show the same tendency as those in previous works. In the second part of this study, this paper tries to develop a flutter suppression method with higher leakage performance. This is achieved by changing the seal geometry. To detect the important geometric parameters, the contribution of each geometric component to aeroelastic instability is carefully analyzed. On the basis of this, the seal geometry is modified and its performance is evaluated. The optimized labyrinth seal shows good performance in terms of flow leakage and aeroelastic stability. Through this study, a new flutter suppression method is established.

Evaluation of mountain slope stability considering the impact of geological interfaces using discrete fractures model

The stability of rock slope is often controlled by the existing discontinuous surfaces, such as discrete fractures, which are ubiquitously distributing in a geological medium. In contrast with the traditional approaches used in soil slope with a continuous assumption, the simulation methods of jointed rock slope are different from that of in soil slope. This paper presents a study on jointed rock slope stability using the proposed discontinuous approach, which considers the effects of discrete fractures. Comparing with traditional methods to model fractures in an implicit way, the presented approach provides a method to simulate fractures in an explicit way, where grids between rock matrix and fractures are independent. To complete geometric components generation and mesh partition for the model, the corresponding algorithms were devised. To evaluate the stability state of rock slope quantitatively, the strength reduction method was integrated into our analysis framework. A benchmark example was used to verify the validation of the approach. A jointed rock slope, which contains natural fractures, was selected as a case study and was simulated regarding the workflow of our framework. It was set up in the light of the geological condition of the site. Slope stability was evaluated under different loading conditions with various fracture patterns. Numerical results show that fractures have significant contributions to slope stability, and different fracture patterns would lead to different shapes of the slip surface. The devised method has the ability to calculate a non-circular slip surface, which is different from a circular slip surface obtained by classical methods.

Adaptive view and illumination planning for SVBRDF measurement of complicated three-dimensional objects

Appearance attributes of a three-dimensional (3-D) object, including reflection and color, are modeled as a spatially varying bidirectional reflectance distribution function (SVBRDF). However, a considerable number of images of the object are required to accurately define an SVBRDF when it exhibits complicated geometric components, thereby leading to a considerable amount of time to acquire, store, and process them. We propose a method to considerably decrease the number of images for SVBRDF modeling while maintaining the quality of the model that is achieved with several images. We introduce an acquisition score and its corresponding objective function by considering the local geometry and reflectance properties to estimate the optimal view and illumination directions for the image acquisition in which an object is measured with a reduced number of images. The captured images are subsequently processed to obtain an SVBRDF of the object. The experimental results demonstrate that the proposed method measures the appearance of a 3-D object with complicated shapes by using a few hundred images and efficiently produces an SVBRDF of the object with complicated shapes. The results indicate that the proposed method photorealistically renders an object with fewer artifacts than existing methods when any arbitrary view and illumination directions are given.

HBIM IMPLEMENTATION FOR AN OTTOMAN MOSQUE. CASE OF STUDY: SULTAN MEHMET FATIH II MOSQUE IN KOSOVO

Abstract. National Strategy For Cultural Heritage 2017–2027 is a Kosovo Government document that aims the enhancement of the system for the protection and preservation of Kosovan cultural heritage. Among the listed goals, one can find the promotion of an integrated data management approach towards cooperation platforms that involve advanced technologies and information systems applied to cultural heritage. In a country with a low technological progress, as Kosovo is, an innovative information management system like HBIM is a huge challenge. This research contributes in opening the debate about the use of HBIM even for historical architecture, illustrating a methodology of information management promoting the conservation and the valorization of a Kosovan ottoman mosque. The workflow pipeline started with the close range photogrammetric survey, obtaining first spherical panoramas and then the wire-frame processed in a 3D modelling environment, suitable to implement the HBIM project. Basing on the accuracy of the data acquisition, the availability of information about the building and the related level of knowledge, we proposed a semantic representation of the complex structure integrating in an HBIM collecting in an “ad hoc” database the geometrical building components, enriched with attributes as images, materials, decay, interventions, etc., linked to each features. Our approach is an example of how efficient semantic classification can be repeated for the analysis and the documentation of other similar ottoman mosque, simplifying the management of construction by a sort of unique and searchable archive. The advantage of the interoperability concept allows the data sharing is now stressed by HBIM.

FROM LIDAR DATA TOWARDS HBIM FOR STRUCTURAL EVALUATION

Abstract. In HBIM processes, the extraction of geometric components from 3D point clouds data can sometimes be a complex process. The so-called Scan to BIM process has been widely utilized: deriving 3D models from point clouds often a local modelling of geometric components is necessary. This leads in most cases to use external modelling tools or complex local modelling processes. In both cases, we often get a model that cannot be reused for other items belonging to the same category, contravening the BIM philosophy. Vaulted systems are a typical example of complex elements that we can find in historical architecture. The paper presents the first results of an ongoing research on geometric modelling and structural evaluation of masonry ribbed vaults. An algorithm is developed to generate a NURBS surface of masonry vaults that, starting from the data extrapolated from the point cloud, allows to obtain an HBIM family. The research aims to overcome the inability to reference to standardised objects in local modelling of historical architecture elements. Directed to a standardization in the geometric modelling process of 3D laser scan data, the developed workflow is a possible alternative to commonly used workflows. Particular attention is focused on a case study of stellar vaults, a special class of masonry ribbed vaults whose three-dimensional geometry features a star-shaped projection on the horizontal plane. The work is carried out to verify that this family can be used for the structural analysis of stellar masonry vaults.

A Methodology for the Application of Virtual Evaluation Methods within the Design Process of Cold Forged Steel Pinions

AbstractGears are essential machine elements in the drivetrain and transmission technology. The operational behaviour of a gear pairing is influenced by the design of the gear kinematics as well as the component properties. With regard to an improvement of performance and service life, the targeted modification of tooth geometry and component properties offers a promising approach. Thus, the achievable geometric and mechanical component properties are influenced by the manufacturing process, which must be taken into account in the design process. The application of virtual evaluation methods is suitable for this purpose. For the manufacturing of steel gears, cold forging provides the potential of achieving beneficial mechanical properties in a highly productive process. Major challenges for the industrial application are the short service life of the cost- intensive tools and the low geometric accuracy in comparison to machining processes. Within this study the design of the tooth geometry as well as the associated forming tool are investigated. The aim is to derive recommendations regarding an optimization of the resulting component properties and operational behaviour.

Constrained trajectory simplification with speed preservation

ABSTRACTThe rapid increase in movement trajectory data causes data storage, transmission, computational processing, and visualization problems. These issues can be alleviated through trajectory simplification, which removes unnecessary details from raw trajectories. Most existing studies that focused on trajectory simplification considered freely moving objects, and they attempted to minimize position errors in their simplified representations in a two-dimensional plane. However, a large number of objects move within the constraint of road networks. In such constrained trajectory simplification, position error should be measured in the network space. Moreover, constrained trajectories contain a wealth of speed-change information that reflects the movement patterns of moving objects. In this study, we designed a data model, proposed error measurements, and developed a two-component method to simplify constrained trajectories. The geometric component in our method extended the classic Douglas–Peucker method using network distance to simplify trajectories with a guaranteed position error bound in network space. The semantic component enhanced the simplified representation by employing a data-enrichment strategy that allows users to control speed loss. Real trajectory data were used to assess the effectiveness of the proposed method. Experimental results show that our method has a lower position error than existing algorithms do when road network constrained trajectory data are simplified. The method can also preserve original speed in the simplified representation with a relatively low increase in data size. Our study thus provides an approach to simplifying trajectory data that guarantees error bounds in both location and speed.

Grassmann–Grassmann conormal varieties, integrability, and plane partitions

We give a conjectural formula for sheaves supported on (irreducible) conormal varieties inside the cotangent bundle of the Grassmannian, such that their equivariant K-class is given by the partition function of an integrable loop model, and furthermore their K-theoretic pushforward to a point is a solution of the level 1 quantum Knizhnik–Zamolodchikov equation. We prove these results in the case that the Lagrangian is smooth (hence is the conormal bundle to a subGrassmannian). To compute the pushforward to a point, or equivalently to the affinization, we simultaneously degenerate the Lagrangian and sheaf (over the affinization); the sheaf degenerates to a direct sum of cyclic modules over the geometric components, which are in bijection with plane partitions, giving a geometric interpretation to the Razumov–Stroganov correspondence satisfied by the loop model.

Numerical studies on effect of operating conditions and geometrical components on the timing response and efficiency of RPC

A detailed numerical simulation has been performed to investigate the timing properties of a standard RPC geometry in order to optimize its application in INO-ICAL experiment designed for studying atmospheric neutrinos. The timing information provided by the RPC is an important observable in the experiment to determine the direction of the neutrinos. Effects of various operating conditions and design components on the RPC timing response, mainly the average signal arrival time and the time resolution have been studied in this context. The dependence of the detector efficiency on the same parameters has also been presented.

Sharp-edge diffraction under Gaussian illumination: a paraxial revisitation of Miyamoto-Wolf’s theory

A "genuinely" paraxial version of Miyamoto-Wolf's theory aimed at dealing with sharp-edge diffraction under Gaussian beam illumination is presented. The theoretical analysis is carried out in such a way the Young-Maggi-Rubinowicz boundary diffraction wave theory can be extended to deal with Gaussian beams in an apparently straightforward way. The key for achieving such an extension is the introduction of suitable "complex angles" within the integral representations of the geometrical and boundary diffracted wave components of the total diffracted wavefield. Surprisingly enough, such a simple (although not rigorously justified) mathematical generalization seems to work well within the Gaussian realm. The resulting integrals provide meaningful quantities that, once suitably combined, give rise to predictions that are in perfect agreement with results already obtained in the past. An interesting and still open theoretical question about how to evaluate "Gaussian geometrical shadows" for arbitrarily shaped apertures is also discussed.

Stability analysis for cosmological models in f(R) gravity using dynamical system analysis

Modified gravity theories have received increased attention lately to understand the late time acceleration of the universe. This viewpoint essentially modifies the geometric components of the universe. Among numerous extension to Einstein’s theory of gravity, theories which include higher order curvature invariant, and specifically the class of f(R) theories, have received several acknowledgments. In our current work we try to understand the late time acceleration of the universe by modifying the geometry of the space and using dynamical system analysis. The use of this technique allows to understand the behavior of the universe under several circumstances. Apart from that we study the stability properties of the critical point and acceleration phase of the universe which could then be analyzed with observational data. We consider a particular model f(R) = R - mu R_{c}(R/R_{c})^{p} with 0< p < 1, mu , R_{c} > 0 for the study. As a first case we consider the matter and radiation component of the universe with an assumption of no interaction between them. Later, as a second case we take matter, radiation and dark energy (cosmological constant) where study on effects of linear, non-linear and no interaction between matter and dark energy is considered and results have been discussed in detail.

Lateral error compensation for stitching-free measurement with focus variation microscopy

This paper proposes a practical methodology to quantify and compensate lateral errors for focus variation microscopy measurements without stitching. The main advantages of this new methodology are its fast and simple implementation using any uncalibrated artefact. The methodology is applied by performing measurements with multiple image fields with and without stitching on an uncalibrated artefact and using the stitched measurements as reference. To quantify the lateral errors, the determination of their geometrical components is carried out through kinematic modelling. With the quantified errors, compensation can be applied for lateral measurements without stitching. Over the entire 200 mm lateral range, the lateral errors without stitching and without compensation can reach up to 180 µm. With the proposed error compensation methodology, the lateral errors have been reduced to around 15 µm. The proposed methodology can be applied to any Cartesian-based optical measuring instrument.

Геометрическая модель генерации семейства контурно-параллельных линий для автоматизированного расчета траектории режущего инструмента

In this paper has been proposed a geometric model for forming problem of contour-parallel lines (equidistant lines) for a flat contour with an island, and has been obtained the problem’s analytical solution, which is relevant for computer-aided design of cutting tools processing pocket surfaces on CNC machines. The proposed geometric model is based on cyclograph mapping of space on a plane. Beyond the analytical solution the geometric model differs from the known algebraic models and their solutions for considered forming problem also by the fact that it allows obtain a more complete and evident representation on the relationship and interaction for all its geometric components at the stages of 3D computer visualization. A 3D geometric model based on a cyclograph mapping of space has been proposed for obtaining the families of equidistant lines for connected and multiply connected regions with closed contours taken as a basis for pocket surfaces modeling. An algorithm for the analytical solution of the problem related to equidistant families generation is getting from the geometric model. All stages of the analytical solution are accompanied by a figurative representation of geometric objects and their relations in the geometric model’s virtual electronic space. The proposed in this paper algorithm for the case of a doubly connected polygonal region can be used as a basis for generation of equidistant families for multiply connected polygonal regions. The presence of the analytical solution for the problem related to equidistant families generation simplifies greatly the automated calculation of the tool path and preparation of control programs for pocket surfaces manufacturing on CNC machines. Have been presented an example and algorithm providing support for working capacity of the proposed geometric model for considered forming problem.

Design and off-design optimization procedure for low-temperature geothermal organic Rankine cycles

In this paper, a two-step optimization methodology for the design and off-design optimization of low-temperature (110–150 °C) geothermal organic Rankine cycles (ORCs) is proposed. For the investigated conditions—which are based on the Belgian situation—we have found that the optimal ORC design is obtained for design parameter values for the environment temperature and for the electricity price which are both higher than the respective yearly-averaged values. However, the net present value is negative (−12.62 MEUR) which indicates that the low-temperature (130 °C) geothermal electric power plant is not economically attractive for the investigated case. Nevertheless, and demonstrated by the results of a detailed sensitivity analysis, a low-temperature geothermal power plant might be economically feasible for geological sites with a higher brine temperature or in a country with a more favorable economic situation; e.g., with higher electricity prices (∼70 EUR/MWh). The novelty of our paper is the development of a thermoeconomic design optimization strategy for low-temperature geothermal ORCs, accounting for the off-design behavior already in the design stage. The generic methodology is valid for low-temperature geothermal ORCs (with MW scale power output) and includes detailed thermodynamic and geometric component models, is based on hourly data rather than monthly-averaged data and accounts for economics.

The Computation of Attributes from Multi-fold Seismic Refraction Data

Seismic attributes are any measure that helps to better visualize or quantify features of interest in seismic data. Refraction attributes can be readily computed from multifold seismic data using the standard algorithms of the generalized reciprocal method (GRM), a common offset refraction (COR) modification of the GRM, and the refraction convolution section (RCS). The COR GRM algorithms are applied prior to the parameterization of the traveltime data into individual layers. The COR GRM presentations facilitate the efficient quality control and interpretation of large sets of multi-fold data. Furthermore, the COR GRM algorithms can be readily applied to single ended refraction data, which are routinely recorded with marine and land streamers. The time model attribute obtained with the COR GRM algorithm is of comparable accuracy to that computed with the standard multi-fold GRM. However, the COR GRM seismic velocity model is a smoothed version of the fully optimized standard GRM model. The refraction attributes computed from the head wave amplitudes include the multi-fold head coefficient, and a COR equivalent with the amplitude product. Although the COR amplitude product for each offset is of comparable accuracy to the multi-fold head coefficient, it also includes a residual geometric spreading component. Another refraction attribute computed from the head wave amplitudes is the geometric spreading coefficient, which is generally assumed to be two in the far field for plane homogeneous refractors. This parameter is consistent over a wide range of offsets, but varies considerably from less than one to up to four along the seismic traverse The attribute derived from the RCS is bandwidth in octaves. It is proposed that refraction attributes can be employed to derive more useful models of the regolith using multivariate geostatistics. It is concluded that, refraction attributes offer the opportunity of extending the refraction method to new applications.

SCAN-TO-BIM vs 3D IDEAL MODEL HBIM: PARAMETRIC TOOLS TO STUDY DOMES GEOMETRY

Abstract. The contribution is part of an interdisciplinary research that aims to address the problems of knowledge, interpretation and documentation of vulnerable structures such as the brick Renaissance domes in Campania (XV-XVI century). The goal is to analyze the relationship between Survey, Historic Building Information Modelling (HBIM) and 3D parametric models based on geometric rules from Treaties to study and to manage Cultural Heritage. HBIM is generally based on scan-to-BIM process that allows to generate 3D model from point cloud. The reverse modeling process, from a point cloud to parametric geometric model, poses a series of issues at the center of cultural debate that currently takes place around HBIM. The experimentation underway is part of this research field with the aim of using the parametric approach as a tool able to introduce an additional methodology for big data interpretation. Currently we can identify two different approaches for the construction of a HBIM system: building a simplified model by identifying the shape grammar or building the geometric components from survey without using pre-compiled objects libraries, following the scan to BIM logic. In our research we are going to identify an "hybrid" methodology. Generally the process is based on the knowledge and critical abilities of individual scholars, the idea is to increase the efficiency of the system through collaborative workflow forms that allow to optimize the processes through effective knowledge management actions. We are going to use procedural modeling techniques to generate HBIM domes library.

Tunable local surface plasmon resonance and refractive index sensitivity ability of three-layered dielectric-silver bimetallic nanoshells

Optical properties and refractive index sensitivity abilities of three-layered silver/gold-dielectric-silver bimetallic nanoshells are investigated based on quasi-static theory. The results show that absorption spectra of silver/gold-dielectric-silver bimetallic nanoshells can be well tuned by changing the inner core radius, middle dielectric radius and outer shell layer thickness. Local surface plasmon resonance (LSPR) shifts of |ω−−〉 mode show a red-shift with increasing the inner core radius and the thickness of middle dielectric layer, while a blue-shift with increasing the thickness of outer shell. It is interesting to find that the shifts of |ω−+〉 mode are related to the ratio ε2∕ε4, the component of core and nanoshell. In addition, the refractive index sensitivity abilities of three-layered silver/gold-dielectric-silver bimetallic nanoshells are also reported. A higher refractive index sensitivity ability can be obtained by adjusting its geometric size and component. |ω−−〉 mode gets more intensity with increasing the surrounding medium dielectric function, while |ω−+〉 mode fades down. The intensity difference between |ω−−〉 mode and |ω−+〉 mode is mainly effected by the surrounding medium dielectric function, its geometric parameter, middle layer dielectric function, the component of core and nanoshell. Our study provides a way to analyze sensitivity application of nanoshells and broadens the application of nanoshells in sensor ability.