Geometrical Component Research Articles

Authoring Moving Parts of Objects in AR, VR and the Desktop

Creating digital twins of real objects is becoming more popular, with smartphones providing 3D scanning capabilities. Adding semantics to the reconstructed virtual objects is important to possibly reproduce training scenarios that otherwise could demand significant resources or happen in dangerous scenarios in some cases. The aim of this work is to evaluate the usability of authoring object component behaviors in immersive and non-immersive approaches. Therefore, we present an evaluation of the perceived ease of use to author moving parts of objects under three different conditions: desktop, augmented reality (AR) and virtual reality (VR). This paper provides insights into the perceived benefits and issues that domain experts might encounter when authoring geometrical component behaviors across each interface. A within-subject study is the major contribution of this work, from which is presented an analysis based on the usability, workload and user interface preferences of participants in the study. To reduce confounding variables in the study, we ensured that the virtual objects and the environment used for the evaluation were digital twins of the real objects and the environment that the experiment took place in. Results show that the desktop interface was perceived as more efficient and easier to use based on usability and workload measures. The desktop was preferred for performing component selection but no difference was found in the preference for defining a behavior and visualizing it. Based on these results, a set of recommendations and future directions are provided to achieve a more usable, immersive authoring experience.

Parametric study on the internal geometry affecting agricultural air induction nozzle performance

With recent advances in agricultural engineering, precision spraying has become of prime interest to avoid chemical drift or rebound and to minimize water and soil pollution. Air induction nozzles are reliable alternatives for conventional nozzles to overcome these challenges. A parametric study was designed both experimentally and numerically to investigate the effect of each design parameter on the performance of an air induction nozzle. A number of components were designed, manufactured, and tested. The spray structure was captured using a planer Mie scattering imaging system. The mean droplet size was measured using a Malvern particle sizer based on a laser diffraction technique. The results indicated the influence of each geometrical component on the resultant behavior. The internal geometry of the nozzle was found to significantly impact the stability and structure of the spray such as the fluid behavior inside the nozzles and the air-to-liquid mass flow ratio, as well as spray angle, droplet size, and uniformity. The key findings of this study indicate that pre-orifice inlet diameter primarily controls the flow behavior, air, and liquid inlet diameters of the ejector section impact mainly on the air-to-liquid mass flow ratio, the geometry of the mixing chamber mainly controls the stability of the resulting spray, and the geometry of the flat-fan tip essentially controls the spray angle and droplet size. The results can help nozzle designers optimize the design target, enhance atomization efficiency, and understand the effect of the various design parameters on the internal flow behavior of air induction nozzles.

Impact of low inner ring waviness orders on hybrid ball bearing under high speeds

Deep groove ball bearings (DGBB) are widely used in rotating equipment in many fields among which we have electric vehicle Powerpack, so very demanding in terms of noise and vibration. Geometrical design, clearance, component material, and lubricant properties influence vibratory behavior and bearing life cycle. In rotating machines, bearings are acting as friction reducers to allow a smooth rotation but are also exciters inducing vibrations due to the rotation of ball set, even in the case of a theoretical perfect bearing. Bearing performance depends highly on contact surface quality (ring races and balls surface). In a ball bearing, contact surface quality results from several manufacturing processes (heat treatment, turning, grinding, honing and assembly) and directly affects the noise and vibration levels generated by the bearing in the application. Also, component materials and hardness will affect the contact forces between balls and rings path on rotating bearings. Hybrid bearings are known for their performance when operating under high rotation speeds. In this article, inner and outer ring low waviness orders are studied on Hybrid Deep Groove Ball Bearings (DGBB). Both numerical model and, experimental tests were carried out to study the effect of rings waviness on hybrid bearing under high rotation speed.

Investigation of the influence of material and sheet thickness on a three-stage process chain for cold forming of micro gears with a module of 0.1 mm

In many industries, there is a trend towards miniaturization of technical components, such as drive systems, which enable the solution of high-precision positioning tasks because of their low volume and high dynamics. Geared micro parts are currently mainly produced by cutting and LIGA processes, but in mass production cold forming offers ecological and economic benefits. However, the cold forming of micro gears is restricted to a lower module limit of m = 0.2 mm due to high tool stresses, size effects and handling difficulties. To solve these challenges, in this contribution a three-stage forming process chain for the manufacturing micro gears (m = 0.1 mm) is investigated. In the first stage, a pin as wheel blank is extruded from sheet metal, which is geared subsequently by lateral extrusion. Finally, the micro gear is separated from sheet by shear cutting. The aim of this study is to demonstrate the applicability of the process chain for the materials Cu-OFE and CuZn30. In addition, the influence of the sheet thickness, which has a major impact on the forming process and the material efficiency, is analyzed. The geometrical and mechanical component properties as well as the machine data are evaluated to assess the variables.

Locomotion performance for oscillatory swimming in free mode

Oscillatory swimming of a fishlike body, whose motion is essentially promoted by the flapping tail, has been studied almost exclusively in axial mode under an incoming uniform stream or, more recently, self-propelled under a virtual body resistance. Obviously, both approaches do not consider the unavoidable recoil motions of the real body which have to be necessarily accounted for in a design procedure for technological means. Actually, once combined with the prescribed kinematics of the tail, the recoil motions lead to a remarkable improvement on the resulting swimming performance. An inviscid impulse model, linear in both potential and vortical contributions, is a proper tool to obtain a deeper comprehension of the physical events with respect to more elaborated flow interaction models. In fact, at a first look, the numerical results seem to be quite entangled, since their trends in terms of the main flapping parameters are not easy to be identified and a fair interpretation is obtained by means of the model capability to separate the effects of added mass and vortex shedding. Specifically, a prevailing dependence of the potential contribution on the heave amplitude and of the vortical contribution on the pitch amplitude is instrumental to unravel their combined action. A further aid for a proper interpretation of the data is provided by accounting separately for a geometrical component of the recoil which is expected to follow from the annihilation of any spurious rigid motion in case no fluid interactions occur. The above detailed decomposition of the recoil motions shows, through the numerical results, how the single components are going to influence the main flapping parameters and the locomotion performance as a guide for the design of biomimetic swimmers.

Investigation of Different Components of Parallel-Hole Collimator Response to Different Radioisotope Energies Used in Nuclear Medicine Imaging.

The quality of images obtained from the nuclear medicine imaging systems depends on different factors. One of the most important of these factors is the geometrical and physical characteristics of collimator used for imaging with a given radioisotope. The aim of this study is to investigate the contribution of different components of collimator response for determining the most suitable parallel-hole collimator for the different radioisotope energies used in nuclear medicine imaging. In this study, the SIMIND Monte Carlo simulation program is used to determine the contribution of geometrical, penetrating and scattered response components of four hexagonal parallel-hole collimators including low-energy high-resolution (LEHR), low-energy general-purpose (LEGP), medium-energy general-purpose (MEGP), and high-energy general-purpose (HEGP) collimators, for 12 different energies used in nuclear medicine imaging. According to the simulation results, the use of both the LEHR and LEGP collimators leads to a geometrical component above 60% for energies between 69 and 171 keV. On the other hand, for energies between 185 and 245 keV, the MEGP collimator and for energy of 364 keV, the HEGP collimator gives the geometrical components above 70% and 60%, respectively, while for energy of 511 keV, the geometrical response of all four collimators is below 20%. The results of this study show that for two low-energy single-photopeak radioisotopes, Tc-99m and I-123, the LEHR and LEGP collimators, and for high-energy single-photopeak radioisotope, I-131, the HEGP collimator are most suitable collimators. For dual-photopeak In-111 radioisotope and triple-photopeak Ga-67 radioisotope, the MEGP and HEGP collimators and for triple-photopeak Tl-201 radioisotopes, the LEHR and LEGP collimators are proposed as most suitable collimators.

Geometrical-Empirical Channel Propagation Model for Human Presence at 60 GHz

Previous efforts to develop simulation and/or measurement-based channel propagation models for the effect of human blockage on millimeter-wave communication systems have yielded important results, but lack either accuracy, generality, or simplicity. To fill that void, in this paper we propose a hybrid geometrical-empirical model for human presence; we refer to it as human presence because reflection from the body before and after blockage occurs in addition to diffraction around the body during blockage (as in previous efforts) is incorporated. Specifically, propagation is modeled as the superposition of the main transmission path and reflected and/or diffracted paths from the body; the geometrical component of the model accounts for the phase of each path while the empirical component accounts for its amplitude. To validate the proposed model and extract its empirical parameters, an exhaustive measurement campaign with 120 blockage scenarios, comprising varying human subjects and transmitter-human-receiver configurations, was conducted; a total of 180,000 channel acquisitions was recorded with our precision, state-of the-art 60-GHz channel sounder. The overall model is shown to be computationally efficient yet general enough to accurately represent a wide range of scenarios.

Numerical conformal mapping method vs. geometrical separation attitude: Combustion motor chamber internal flow simulation

AbstractThis paper describes the numerical solution of flow analysis in a two‐dimensional combustion chamber with two parallel inlets aided for propellants entrance, addressing a number of different problems that depend on each other: the flow affected by a discrete point in‐cell vortex, the velocity affected by the flow regime in the cell, and the combustion problem affected by the oxygen and fuel entries from the cell walls. The shape geometry of the combustion chamber is made from a square section connected with a semi‐circular one. The mathematical model of the problem consists of an inhomogeneous stream function Laplace equation coupled to partial differential mass conservation equation subjected to a wall non‐intrusion condition and known mass values in the wall openings. Algebraic conformal mapping transformation has been used for modeling the complex cell geometry. The solution was obtained by using the iterative Gauss–Seidel method for both the current function and the mass calculation. Comparison with another modeling method for calibration purpose was performed; considering each geometrical component separately whereas continuous conditions were applied between the two sections. The grid types are: (1) a uniform grid in Cartesian coordinates in the square part, and (2) a uniform circular grid in polar coordinates. It was found that different initial guesses have not effect on the final solution, but an informed initial guess affects the solution time convergence iterations number to solve the problem. Finally, the effect of the mixing vortex on the location of the flame front in the chamber was investigated.

An improved segementation approach for skin lesion classification

Skin cancer is one of the most common types of cancer, its incidence reached epidemic proportions and caused many deaths. Skin cancer can be categorize into three main types; Actinic Keratoses, Basal cell carcinoma and Melanoma. The melanoma skin cancer is the most aggressive and the deadliest form of skin cancer compared to the others. Early Melanoma detection and diagnosis often allows for more treatment option and decreases significantly the number of deaths. Many researchers proposed to use image processing for skin lesion detection. The process can be divided into three main stages: lesion identification based on image segmentation, features extraction and lesion classification. Segmentation and features extraction are the key-steps and significantly influence the outcome of the classification results. In this paper, a new approach for automatic segmentation and classification for skin lesion has been proposed. The proposed approach consists on a preprocessing based on multiscale decomposition that’s separate the input image into two components. The geometrical component will be used in the segmentation stage and the texture component in features extraction. The classification performed using the Support Vector Machine (SVM) classifier. The efficiency and the performance of the proposed approach has been evaluated in comparison with recent and robust dermoscopic approaches from literature.

Optimization of process parameters to improve dimensional accuracy of investment casting using Taguchi approach

In this study, Taguchi method is used to investigate the effect of critical process parameters of investment casting on dimensional variations of thin walled, complex geometrical stainless steel component. A set of experiments have been conducted to calculate shrinkages which is a measure of dimensional variation. The process parameters considered here are number of ceramic coats, pouring time, pouring temperature, and casting cooling rate. The signal-to-noise ratio and analysis of variance are used to study the influence of these parameters on shrinkage. Optimized condition for reduced shrinkage deviation can be obtained by selecting lower number of ceramic coats, faster and laminar metal pouring, lower superheated metal temperature, and faster cooling rate. Analysis of variance reports that the number of ceramic coats is the most significant parameter with more than 80% contribution whereas other parameters are insignificant. Investigation results also indicate that constraint dimension (width) has 25%–27% higher dimensional variability than non-constraint dimensions (height) for the selected component.

Towards Optimization of μ-Injection Molding Process for a New V-shaped Geometrical Component Using X-Ray CT-Based Quality Characterization

The influence of micro-injection molding process parameters on a molded component’s quality is very prominent. Depending on the functional performance of the part, the desired quality is defined by several criteria which may include dimensional tolerances, shrinkage/warpage, fiber characteristics, and internal defects. A correlation of process parameters with the defined quality attributes needs to be investigated for a new geometrical component. In this work, a micro-component with a new V-shaped geometry is chosen, as this type of geometry finds potential applications in the medical industry. The parts are manufactured with polyoxymethylene resin with a full-factorial design of experimental plan with investigating parameters of mold temperature, melt temperature, injection speed, and packing pressure. The number of internal pores and amount of volumetric shrinkage are identified as the critical quality criteria and the effect of the process parameters is studied with respect to those criteria. The measurement results indicated that the presence of pores is inevitable within the chosen process window; however, the amount can be minimized with careful selection of process settings. Moreover, the statistical analyses demonstrated the significance levels of the process parameters.

The quantum centripetal force on a free particle confined to the surface of a sphere and a cylinder

The momentum operator for a spin-less particle when confined to a 2D surface embedded into 3D space acquires a geometrical component proportional to the mean curvature that renders it Hermitian. As a consequence, the quantum force operator for a particle confined to spherical and cylindrical surfaces, and free otherwise, derived by applying the Heisenberg equation of motion is found to have an apparently no-radial component in addition to the standard classical radial centripetal force. This component which renders the force operator Hermitian is shown to be essential for the vanishing of the torque the force exerts on the particle and so for the conservation of orbital angular momentum and energy. It is demonstrated that the total force is in fact radial as should be the case for a torque-less one and so can be identified as the quantum centripetal force.

Геометрическая составляющая технических инноваций

In technical inventions related to innovative developments, the role of one of the main components belongs to geometry. A follow hypothesis has been adopted: in technical inventions the geometrical component is the determining one. This hypothesis applied to technical inventions can be confirmed by any copyright certificate, any patent both in Russia and abroad. In proposed paper this statement is proved by examples developed based on geometry of following inventions. 1. Screen feeder for sticky masses. Screen feeder’s grates are made in pairs, and between grate pairs there are gaps for screening of material’s size-defined fractions. In the screen-feeder has been proposed such geometry of grates that grates of each pair could clean each other, thereby preventing sticking on the surface and destroying the gaps between the pairs, which transforms the usual screen-feeder with cylindrical grates at an ordinary feeder. 2. Double-screw mixer for paste-like masses. The mixer consists of two contiguous worms. Their surfaces are the helical ones, in cross-section consisting of two quarters of circles stacked at the ends. Such cross-section allows homogenize the mixed paste-like material in the best way, and also deliver it under higher pressure in an extrusion head, that improves a final product. 3. Machine for processing of multi-faceted surfaces. This invention serves for manufacture of worms with a cross-section composed of two, three, etc. pieces of circles of the same radius and angle. Worms, made with this machine, are designed for the above mentioned two-screw mixer. 4. Method of mechanical processing. This method is also intended to manufacture of worms for two-screw mixer.

Hydrothermal synthesis of graphene wrapped Fe-doped TiO2 nanospheres with high photocatalysis performance

In this study, graphene wrapped Fe-doped TiO2 (G-TiO2-Fe) spheres were prepared through a simple hydrothermal process. The structural, optical and photocatalytic properties of synthesized composite were characterized by field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), Raman Microprobe (Raman), X-ray photoelectron spectroscopy (XPS) and UV–Vis diffuse reflectance spectrophotometer (DRS). The G-TiO2-Fe composite showed a significant red-shift in light response edge as compared with TiO2. Meanwhile, the band gap exhibited an obvious decline from 3.24 to 2.99eV. The photocatalytic capacity of G-TiO2-Fe was further evaluated by methylene blue (MB) degradation experiments, and the results indicated that the optimized G-TiO2-Fe exhibited a remarkable increase in photocatalytic activity. The superior photocatalytic performance of the novel material could be ascribed to the synthetic effects of doped Fe and wrapped graphene shells. The unique geometrical configuration and constructive component which modified the TiO2 electronic structure will largely improve the electron transporting efficiency and restrain the electron-hole recombination.

Enhanced definition and required examples of common datum imposed by ISO standard

According to the ISO Geometrical Product Specifications (GPS), the establishment and definition of common datum for geometrical components are not fully defined. There are two main limitations of this standard. Firstly: the explications of ISO examples of common datums are not matched with their corresponding definitions, and secondly: a full definition of common datum is missing. This paper suggests a new approach for an enhanced definition and concrete examples of common datum and proposes a holistic methodology for establishment of common datum for each geometrical component. This research is based on the analysis of physical behaviour of geometrical components, orientation constraints and invariance classes of datums. This approach fills the definition gaps of common datum based on ISO GPS, thereby eliminating those deficits. As a result, an improved methodology for a fully functional defined definition of common datum was formulated.

Study of Direct Fabrication of a Ti-6Al-4V Impeller on a Wrought Ti-6Al-4V Plate by Electron Beam Melting

The direct building of a Ti-6Al-4V impeller part onto a wrought Ti-6Al-4V plate using electron beam melting (EBM) has been reported for the first time in this study. From the results of the defect analysis, hardness measurement, microstructural observation, and tensile test of the as-built specimens, it is revealed that the complex geometrical component can be successfully fabricated, and the finished component has a combination of wrought base plate and EBM-built section. The fusion zone is about 150 μm thick and no defect is observed along the fusion zone. Tensile results also reflect a good fusion between the wrought and EBM-built sections.

Pure endmember extraction using robust kernel archetypoid analysis for hyperspectral imagery

A robust kernel archetypoid analysis (RKADA) method is proposed to extract pure endmembers from hyperspectral imagery (HSI). The RKADA assumes that each pixel is a sparse linear mixture of all endmembers and each endmember corresponds to a real pixel in the image scene. First, it improves the re8gular archetypal analysis with a new binary sparse constraint, and the adoption of the kernel function constructs the principal convex hull in an infinite Hilbert space and enlarges the divergences between pairwise pixels. Second, the RKADA transfers the pure endmember extraction problem into an optimization problem by minimizing residual errors with the Huber loss function. The Huber loss function reduces the effects from big noises and outliers in the convergence procedure of RKADA and enhances the robustness of the optimization function. Third, the random kernel sinks for fast kernel matrix approximation and the two-stage algorithm for optimizing initial pure endmembers are utilized to improve its computational efficiency in realistic implementations of RKADA, respectively. The optimization equation of RKADA is solved by using the block coordinate descend scheme and the desired pure endmembers are finally obtained. Six state-of-the-art pure endmember extraction methods are employed to make comparisons with the RKADA on both synthetic and real Cuprite HSI datasets, including three geometrical algorithms vertex component analysis (VCA), alternative volume maximization (AVMAX) and orthogonal subspace projection (OSP), and three matrix factorization algorithms the preconditioning for successive projection algorithm (PreSPA), hierarchical clustering based on rank-two nonnegative matrix factorization (H2NMF) and self-dictionary multiple measurement vector (SDMMV). Experimental results show that the RKADA outperforms all the six methods in terms of spectral angle distance (SAD) and root-mean-square-error (RMSE). Moreover, the RKADA has short computational times in offline operations and shows significant improvement in identifying pure endmembers for ground objects with smaller spectrum differences. Therefore, the RKADA could be an alternative for pure endmember extraction from hyperspectral images.

On the reflection properties of germanium and quartz focusing crystals

A diffraction component of angular resolution of spherical Q2131 and Ge422 crystals was calculated, measured in experiment and the good agreement was found. Simulation of geometrical component of angular resolution of bent crystals was also performed and the code is designed to simulate reflectivity of the concave crystals. Such code is also aimed to estimate the resolution of focusing x-ray spectrometers.

Semantic maps from multiple visual cues

Future service robots targeted to operate in domestic or industrial environment and in close collaboration with humans should possess the ability to produce meaningful internal perceptual representations of their own surroundings, enabling them to fulfill a variety of real-world tasks. For this purpose, we present here a semantic mapping framework featuring geometrical and semasiological attributes that reveal the relationships between objects and places in a real-life environment. The geometrical component consists of a 3D metric map, onto which a topological map is deployed. The semasiological part is realized by putting together a place recognition algorithm and an object recognition one. The categorization of the different places relies on the resolution of appearance-based consistency histograms, while for the recognition of objects in the scene, a hierarchical temporal memory (HTM) network boosted by a saliency attentional model, is utilized. These semantic attributes are then deposited on the topological map to augment it with the belief distributions regarding the visited places, enabling thus the agent to act in an intelligent manner in human populated environments. Thus, the proposed framework outlines a proficient system in the construction of human conceivable environment representations, which has been successfully assessed on real-world scenarios, proving its ability to provide a consistent solution to the emerging problem of the human-robot cohabitation.

Applicability of Blasted Blanks for Adaption of Tribological Conditions in Sheet-bulk Metal Forming

Manufacturing by sheet-bulk metal forming (SBMF) leads to varying stress and strain states that significantly influence the geometrical component accuracy. To improve the product quality, control of the material flow is needed. A suitable approach is given by adapting the surface properties of tool and/or workpiece and the associated tribological conditions. The study investigates blasted blanks as a method to achieve suitable frictional behavior. The influence of different grit sizes and pressures during abrasive blasting on the surface integrity was analyzed. Based on these results, the tribological behavior of the blasted blanks was evaluated using a pin extrusion test. Finally, functional cause-effect relationships to identify the mechanism of blasted blanks regarding a control of the material flow during SBMF processes were derived. The results revealed that a pressure increase and growing grit sizes lead to an enhanced material removal rate during blasting and thus a roughening of the surface. The strengthening increases with increasing blasting pressures and grit size. The surface integrity significantly influences the frictional behavior and thus the material flow. Thus, blasted blanks with rough surfaces and a high strengthening in the near surface area positively affect the material flow what improves the process results of SBMF processes.