Objects Of Complex Geometry Research Articles

Efficiently solving large-scale electrostatic lightning problems by integrating characteristic basis functions into boundary element method

The evaluation of the electric field near objects of complex geometries is critical in the pre-bridging regime of lightning strikes in high-voltage transmission systems, which is subject to an open domain problem and can be computationally expensive. In this paper, the characteristic basis function method (CBFM) is incorporated into the conventional boundary element method (BEM) to efficiently handle large-scale electrostatic problems. Within the CBFM, low-level basis functions have been replaced by high-level macro characteristic basis functions, resulting in a significant reduction in the number of degrees of freedom. This reduction in unknowns allows iteration-free direct solvers to approximate the matrices, further reducing the computational complexity of the problem. Numerical examples of the surface charge distribution of an actual 500 kV tower-transmission-line system and a three MW wind turbine in the lightning environment demonstrate the accuracy of the proposed CBFM, while requiring considerably much fewer computational resources compared with conventional BEM. Furthermore, CBFM is highly parallelizable, implying the feasibility of handling large electrostatic lightning problems with complex geometries.

Study of the Structure of Hyperbranched Polyglycerol Coatings and Their Antibiofouling and Antithrombotic Applications.

While blood-contacting materials are widely deployed in medicine in vascular stents, catheters, and cannulas, devices fail in situ because of thrombosis and restenosis. Furthermore, microbial attachment and biofilm formation is not an uncommon problem for medical devices. Even incremental improvements in hemocompatible materials can provide significant benefits for patients in terms of safety and patency as well as substantial cost savings. Herein, a novel but simple strategy is described for coating a range of medical materials, that can be applied to objects of complex geometry, involving plasma-grafting of an ultrathin hyperbranched polyglycerol coating (HPG). Plasma activation creates highly reactive surface oxygen moieties that readily react with glycidol. Irrespective of the substrate, coatings are uniform and pinhole free, comprising O─C─O repeats, with HPG chains packing in a fashion that holds reversibly binding proteins at the coating surface. In vitro assays with planar test samples show that HPG prevents platelet adhesion and activation, as well as reducing (>3 log) bacterial attachment and preventing biofilm formation. Ex vivo and preclinical studies show that HPG-coated nitinol stents do not elicit thrombosis or restenosis, nor complement or neutrophil activation. Subcutaneous implantation of HPG coated disks under the skin of mice shows no evidence of toxicity nor inflammation.

Mechanical and Electrical Properties of 3D‐Printed Highly Conductive Reduced Graphene Oxide/Polylactic Acid Composite

A conductive network of reduced graphene oxide (rGO) overlaying on a lightweight polymeric scaffold can offer notable electrical properties while maintaining the same mechanical properties as a similar feature without rGO layer. However, conventional methods are unable to produce customized architecture with controllable electronic and mechanical properties. Herein, a simple methodology for preparing objects of complex geometries by 3D printing that possesses the capability to exhibit a diverse spectrum of conductivity levels depending upon the dip‐coating process is reported. The versatile two‐step process is beneficial to create highly conductive objects as low as 100 Ω sq−1 and lightweight rGO networks. Alternative to inkjet printing and direct fluid dispensing methods, the fabrication method for 3D rGO networks provides the opportunity to combine material selection and advanced printing techniques, thus achieving desired performance criteria at a low cost. Simple fabrication techniques for robust 3D rGO networks hold promise for designing objects with unique properties, offering both high resistance to external mechanical force and uniform internal electronic properties.

On modeling radiation-induced charge effects in objects of complex geometry

Algorithms for supercomputer modeling of the radiation-induced charge effects in materials of a complex multimodal structure are constructed. A geometric model of an object is created using Stilinger-Lubachevsky algorithms for objects of complex geometry. The model includes a system of detectors for statistical evaluation of functionals on the space of solutions of the photon-electron cascade transport equations. Visualization of simulation results is carried out using the three-dimensional approximation based on the neural network technology. The thechnique of mathematical simulating the generation and development of a photon-electronic cascade in a medium is used. The examples of results of calculations of the charge effects in a fragment of a bimodal material are presented. The results of the calculations show that the spatial distribution of the radiation-induced charges has a sharply inhomogeneous structure caused by the presence of boundaries of materials with different radiation properties.

Non-contact assessment of porosity in metal 3D printed parts by vibration spectra

Volumetric porosity as a common defect in metal 3D printing (3DP) that can significantly impede the mechanical properties of products. Traditional methods of porosity control (microscopy) and non-destructive testing (computed tomography) usually are not applicable at the production site. In this study, sensitivity of three examined testing modalities based on acoustic methods and vibration analysis to changes in the volumetric porosity of 3DP parts was examined. Test objects were cylindrical specimens made of AlMg powder by 3DP with a gradually dosed porosity from 0.5 to 4.0%. Ultrasonic testing by through transmission showed the best accuracy using ultrasound velocity and pulse intensity parameters. Shifts of resonant frequency and spectral density and appearance of side harmonics were the manifestations of increased porosity using vibration approaches. The method comprising a loudspeaker as a vibration exciter and an optoelectronic device for remote sensing of vibration is the most attractive from the point of view of application to objects of complex geometry.

A Facile and Green Microwave‐Assisted Strategy to Induce Surface Properties on Complex‐Shape Polymeric 3D Printed Structures

AbstractLight‐ induced polymeric 3D printing is becoming a well‐established fabrication method, showing manifold advantages such as control of the local chemistry of the manufactured devices. It can be considered a green technology, since the parts are produced when needed and with minimum amount of materials. In this work 3D printing is combined with another green technology, microwave‐assisted reaction, to fabricate objects of complex geometry with controllable surface properties, exploiting the presence of remaining functional groups on the surface of 3D printed specimens. In this context, surface functionalization with different amines is studied, optimizing formulations, reaction times, and avoiding surface deterioration. Then, two different applications are investigated. MW‐functionalized filter‐type structures have been tested against Staphylococcus aureus bacteria, showing high bactericidal activity on the surface along all areas of the complex‐shaped structure. Second, a fluidic chip composed of three separated channels is 3D printed, filled with different amine‐reactive dyes (dansyl and eosine derivatives), and made to react simultaneously. Complete and independent functionalization of the surface of the three channels is achieved only after 2 min of irradiation. This study demonstrates that light induced 3D printing and microwave‐induced chemistry can be used together effectively, and used to produce functional devices.

Three-Dimensional Modelling of A Bridge by Integrating Terrestrial and Aerial Photogrammetry Applying an Adapted Capture Method

Three-dimensional (3D) photogrammetric modelling is a contemporary remote sensing method for generating digital models with their specific appearance and texture, which are used in various areas of life. The modelling of complex geometry objects, such as masonry bridges, is not an easy task, because of their specific features (the presence of arches and various niches). This determines the choice of an adapted capture method according to the individual characteristics of the object. The paper presents research aimed at generating a highly accurate three-dimensional model of a bridge, by combining terrestrial and aerial photogrammetry. A low-cost unmanned aerial system (UAS) was used for capturing the upper side of the bridge. This significantly optimised capture time. But its capabilities do not allow to capture the bridge arches from the bottom upwards, nor to obtain an accurate model of the bridge railing. Because of this, a terrestrial survey was made with a digital camera, thus complementing the information required to generate a comprehensive model of the bridge. The integration of aerial and terrestrial capturing using low-cost cameras and systems, along with the application of modern algorithms for processing, allow to create precise, accurate, and detailed digital models. It is all very important for future conservation, restoration, adaptation, and socialisation of such type of objects which are monuments of culture.

Rules governing swarm robot in continuum mechanics

To determine material body’s deformation is usual to solve Newton’s equation, under assigned boundary conditions; but this is not the only possibility to obtain a plausible description of the phenomenon. In recent years, position-based dynamic (PBD) concept has consolidated its success. The idea has its roots in computer graphic graphics aimed at saving processing time in computing object’s deformation and breakage in video games applications; PBD tries to give a plausible description of the deformation taking into account only the relative point’s positions to describe the action of internal forces. The aim is to obtain an algebraical equation capable of calculating the position of a point using as input the position of some other points. This kinematic approach has the advantage to work with simple algebraical equations; the complexity of the system increases linearly, rather than quadratically, with increasing the point’s number. Working on swarm robotics we have addressed the problem concerning flocking rules, to determine the behaviour of a single element to achieve an assigned configuration of the group. One possibility to perform this task, for each single robot, is to see what some of its neighbours are doing. We then use these rules to reproduce some behaviour of bi-dimensional deformable bodies both consistent with the standard Cauchy model and according to the second-gradient theory. All constitutive properties of the material are hidden within the rules, determining the displacements of the particles each relative to the others. The tool has an advantage in terms of computational cost and is very flexible to be adapted to objects of complex geometry and problems of different nature. The results are encouraging and fracture can be easily managed. However, a connection between the parameters of the tool and the constitutive parameters of the materials is not yet provided and our efforts are addressed in this direction, to validate the tool by a solid classical theory.

Численное моделирование распространения акустического сигнала в подводном звуковом канале

Object and purpose of research. The progress in numerical simulation methods significantly widens the capabilities of theoretical analysis in the tasks requiring extensive calculations and input data sets, like sound propagation at sea. This paper discusses the feasibility of a numerical model describing the physics of acoustic signal propagation in a deep-water channel. Materials and methods. Acoustic signal calculation is performed as per the ray-path theory with a numerical model taking into account depth-wise variations of sound velocity and seabed parameters. Main results. It was shown that depending on the vertical distribution of sound speed, the source depth and distance, the acoustic wave propagation direction can change over significant range of angles the in vertical plane. In this regard it is advisable to calculate the real target force of an object of complex geometry not only from heading angle in horizontal plane but also in terms of the possible range of angles in the vertical plane. Conclusion. Model-analyzed angles range of long-range wave propagation may be used for change estimation of object target force characteristics. Practical significance of the study lies in improving the methods of calculation of the real target force of complex shape objects in terms of state-of the art capabilities of simulating the propagation of acoustic signals conditions in the ocean.

3D relative dose measurement with a μm thin dosimetric layer

A μm thin dosimetric coating material based on inorganic phosphor particles NaYF4:Yb3+, Er3+ has been developed. A dose dependency of the luminescence decay time is observed in the μs - ms domain which allows relative dose measurement in the kGy range. Dose values are obtained from decay time evaluation which facilitates a measurement independent of luminescence emission intensity. Here, near-IR luminescence after excitation with 5 ms pulses of near-infrared light is analyzed. The dosimetric material can be directly sprayed onto the surface of objects and therefore renders particularly useful for dose distribution measurements on non-planar geometries. Because of the μm thickness and the direct contact of the dosimetric material to the entire surface of an object, the results can be considered as ‘true’ surface doses. Three dimensional dose maps were derived by scanning the entire surfaces of irradiated objects. Proof-of-concept is provided by good agreement in dose results as well as dose pattern with film dosimetry (Risø B3 strips) and the approach therefore qualifies especially for use in 3D dose mapping of complex geometries. This novel approach provides unprecedented insights into dose distributions of irradiated objects of complex geometries, as exemplified by dose results for outer and inner surfaces of e-beam irradiated bottles for two different irradiation set-ups.

Numerical Mesoscale Modelling of Microstructure Evolution during Selective Laser Melting

Selective laser melting (SLM) is one of the most popular additive-manufacturing techniques that are revolutionising the production process by opening up new possibilities for unique product-shape fabrication, generating objects of complex geometry and reducing energy consumption as well as waste. However, the more widespread use of this technology is hindered by a major drawback—the thermal-history-dependent microstructure that is typical of SLM-fabricated objects is linked to uncertainties regarding the crucial material properties. While trial-and-error approaches are often employed to limit these risks, the rapidly developing field of numerical modelling represents a cheap and reliable methodology for predicting the microstructure—and by extension, the mechanical properties—of SLM-fabricated objects. Numerical approaches hitherto applied to predicting the evolution of the microstructure in SLM processes and similar boundary-value problems are reviewed and analysed in this article. The conducted analysis focused on mesoscopic scale models, which currently offer sufficient resolution to recover the key microstructural properties at a computational cost that is low enough for the methodology to be applied to industrial problems.

Električni automobil sa integrisanim fotonaponskim sistemom

- The paper deals with the modeling and analysis of the effects of integrating photovoltaic systems into the body elements of electric vehicles. The aim of this paper was to examine the capacities, opportunities and effects of local electricity generation in real electric cars. Given the complex geometry of the vehicle and its mobility, this task posed a relatively complex engineering challenge. A mathematical model in MATLAB software has been developed that enables the estimation of the time diagram of photovoltaic panels production integrated into moving objects of complex geometry. Based on real irradiation measurement data for several locations in Serbia, analyses and calculations of the energy balances of electric vehicles with and without integrated photovoltaic panels in the car body were carried out. The results of the paper show the cost effectiveness for the application of this solution in the automotive industry. In addition to the local production of clean energy, the effects of increasing vehicle autonomy and longer range, less frequent visit to the charging station, less dependency and less impact of vehicles on power system are also achieved.

Surface quality evaluation of non-sintered powder layers in Selective Laser Sintering by 3D scanning

In Selective Laser Sintering, powders of various materials are deposited layer by layer in order to form 3D objects of complex geometries via sintering or melting by a concentrated laser source. The evaluation of the quality of the non-sintered powder layer is of paramount importance, because it is among the parameters that influence the mechanical properties of the finished part, such as tensile strength and density. In order to monitor the quality of the non-sintered powder layer various methods have been suggested that are either invasive resulting in the destruction of the layer, or unable to provide an accurate measure of the layer’s quality, notably estimation of surface roughness and layer thickness distribution. In this paper, these disadvantages are tackled by a method of optical evaluation of powder surface quality by means of 3D white light scanning. The process is fast, non-invasive and quantitative. A case study is provided to prove its applicability in a prototype SLS machine. The details of the method are explained and indicative surface roughness measurements are given, followed by ANOVA concerning contribution of recoating cylinder rotary speed as main control factor of the surface roughness of the compacted powder layer.

Tunable Porosity in Fused Filament 3D-Printed Blends of Intrinsically Porous Polymer and Thermoplastic Aliphatic Polyesters Polycaprolactone and Polylactic Acid

Future advances and usage of all-organic polymeric materials with permanent void spaces and high surface areas, in applications such as separations or as supports, depends heavily on the development of processing techniques to produce complex geometry objects. Here, the high free volume glassy microporous polymer PIM-1 was fabricated, as a major component in a polymer blend, into complex and customizable 3D objects by fused filament fabrication (FFF). PIM-1 was found to be compatible with polycaprolactone (PCL) and polylactic acid (PLA) and thus could be processed by extrusion into filaments with high loadings of PIM-1 (50% by mass). Ternary PCL/PLA/PIM-1 composite filaments provided an optimal balance of durability and melt flow characteristics for consistent FFF 3D printing of intricate structures. As printed, the micropores of PIM-1 were blocked and inaccessible to N2 during sorption experiments; however, the ternary composite structures displayed significant meso- and macroporosity and nanostructured ...

Development of an Aerodynamics Characteristics Simulator Using Digital Image

The present explains the numerical prediction of the aerodynamics characteristics with the complex geometry objects defined by digital images. Numerical prediction of the aerodynamics characteristics is one of important issues in analysis of the bio-structure flow problem like the severity of sleep disorder. This study aims to presents an automatic analytical tool for evaluating the fluid properties with digital images that the hand-draw images on A4 paper. Laminar flows are considered to simulate the flow caused by the low Reynolds number in upper airway flow problem. The data arrangement of digital image such as BMP 24 bits format can be as Cartesian grid in simulation, which is to save the process of making the mesh and to identify the object boundary by using the image color. As a result, influence of the upper airway on the fluid flow with images is include this model.

Igniting Soaring Droplets of Promising Fuel Slurries

High rates of environmental pollution by boilers and thermal power plants burning coal of different grades are the main reason for active research in the world aimed at the development of alternative fuels. The solution to the formulated problem acceptable in terms of environmental, technical and economic criteria is the creation of composite slurry fuels with the use of fine coal or coal processing and enrichment waste, water of different quality, and oil sludge additive. This study considers modern technologies of burning slurry fuels as well as perspective research methods of the corresponding processes. A model combustion chamber is developed for the adequate study of ignition processes. The calculation of the basic geometric dimensions is presented. The necessity of manufacturing the combustion chamber in the form of an object of complex geometry is substantiated. With its use, several typical modes of slurry fuel ignition are determined. Principal differences of ignition conditions of a single droplet and group of fuel droplets are shown. Typical vortex structures at the fuel spray injection are shown. A comparison with the trajectories of fuel aerosol droplets in real combustion chambers used for the combustion of slurry fuels is undertaken.

Autonomous motion planning and task execution in geometrically adaptive robotized construction work

Abstract This research explores a means by which a construction robot can leverage its sensors and a Building Information Model (BIM) to perceive and model the actual geometry of its workpieces, adapt its work plan, and execute work in a construction environment. The adaptive framework uses the Generalized Resolution Correlative Scan Matching (GRCSM) search algorithm for model registration, a new formulation for fill plan adaptation, and new hardware for robotic material dispensing. Joint filling is used as a case study to demonstrate the formulation of an adaptive plan and evaluate a robot's ability to perform adaptive work in an environment where the actual location and geometry of its workpieces may deviate from their designed counterparts. Averaged across five experiments, the robot was found capable of identifying the true position and orientation of the joint's center with a mean norm positioning error of 0.11 mm and orientation error of 1.1°. The adaptive framework offers significant promise for a range of construction activities, including those involving objects of complex geometry and detailed work.

Identyfikacja stanu technicznego konstrukcji wsporczej napowietrznej linii elektroenergetycznej

Technical diagnostics of the overhead power line supporting structures is very important from the point of view of reliability and the national energy security. The paper presents a method of identification of technical condition of power line supporting structures. The technique is based on testing the correlation between the change of stress in the system and the change of modal parameters caused by damage. Presented approach is comprehensive and accounts for a number of problems related to the diagnostics of large-size objects of complex geometry. The basic advantage of the developed identification algorithm of the overhead power line supporting structures technical condition is low sensitivity to measurement errors, which is very important in the context of exploitational diagnostics

BRL-CAD와 FDS 오픈소스를 이용한 CFD 해석 시스템의 개발

An open source based CFD analysis system is developed using FDS(Fire Dynamics Simulator) as solver and BRL-CAD as geometric modeler. The BRL-CAD objects of complex geometries in the computational domain are converted to the FDS inputs, and then the CFD analysis are carried out by FDS. The conversion from BRL-CAD objects to FDS inputs and the following FDS calculations turned out stable and robust in test runs. The CFD system was tested so as to reproduce a wind tunnel experiments, and the NRMSE(Normalized Root Mean Square Error) of the mean wind calculations were about 15% against the measurements with reasonable computational loads. The CFD tool of present study utilizing BRL-CAD, in wide use in weaponeering, is expected to find its usefulness in military research.

Application of ultrasonic guided waves for non-destructive testing of large and complex geometry engineering structures

The wide group of large engineering constructions made from welded metal components and modern composite materials during daily exploitation under non-stationary loads, continuous influence of vibrations and complicated environmental conditions have demand of periodical tests in order to avoid appearance and evolution of the defects. All of them have one common feature – large areas to be tested and the complex geometry. The objective is to improve air-coupled and contact type testing techniques for excitation and reception of appropriate modes of ultrasonic guided waves in large and complex structures. Also, to develop inspection techniques which enable to detect required types of internal defects. The air-coupled and contact ultrasonic techniques for investigation of large and complex geometry objects, such as composites for aerospace applications and petroleum tanks, have been developed. The investigation of propagation effects of ultrasonic guided (Lamb) waves in the plates of the tank floor has indicated relation between reconstructed properties of guided waves and expected presence of corrosion deposits.