Traditional Simplification Research Articles

Simplification of 3D CAD Model in Voxel Form for Mechanical Parts Using Generative Adversarial Networks

Most three-dimensional (3D) computer-aided design (CAD) models of mechanical parts, created during the design stage, have high shape complexity. The shape complexity required of CAD models reduces according to the field of application. Therefore, it is necessary to simplify the shapes of 3D CAD models, depending on their applications. Traditional simplification methods recognize simplification target shape based on a pre-defined algorithm. Such algorithm-based methods have difficulty processing unusual partial shapes not considered in the CAD model. This paper proposes a method that uses a network based on a generative adversarial network (GAN) to simplify the 3D CAD models of mechanical parts. The proposed network recognizes and removes simplification target shapes included in the 3D CAD models of mechanical parts. A 3D CAD model dataset was constructed to train the 3D CAD model simplification network. 3D CAD models are represented in voxel form in the dataset. Next, the constructed training dataset was used to train the proposed network. Finally, a 3D voxel simplification experiment was performed to evaluate the performance of the trained network. The experiment results showed that the network had an average error rate of 3.38% for the total area of the mechanical part and an average error rate of 14.61% for the simplification target area.

A Shape-Preserving Simplification Method for Urban Building Models

With the expansion of model scale and the improvement of model accuracy, the real-time rendering and displaying of 3D mesh models remain infeasible. To relieve such pressure, mesh simplification methods have been proposed to reduce the structural complexity while preserving the appearance. This work introduces a shape-preserving simplification method for urban building models. Compared to traditional simplification methods that only consider preserving local geometric features, we also consider the overall shapes of building models to avoid collapse with an increased simplification rate. The proposed method works in four steps. First, we filter mesh models to yield planar structures while preserving sharp features. Second, we detect the shapes of planar regions. Third, we simplify the planar and non-planar regions constrained by the overall shapes and local geometric features. Finally, we remap the texture. Experiments show the effectiveness of this method by evaluating it on various building models and comparing its performance with the original QEM algorithms. Furthermore, we maintain better spatial consistency in building models with different levels of detail (LOD) than traditional methods.

Assessments of Digital Client Representations: How Frontline Workers Reconstruct Client Narratives from Fragmented Information

Abstract Street-level bureaucrats assess increasing amounts of digital, often text-based, client representations. These representations have been criticized for oversimplification. However, frontline workers have also been known to develop simplified perceptions, or “shortcuts,” in their work. This study explores frontline workers’ assessments of digital client representations using observations of 15 needs assessments and 7 follow-up interviews from the Norwegian Labor and Welfare Administration (NAV). Based on simple information garnered from an online registration, workers decide how much assistance clients need from NAV to find work. Findings show that the online registration deconstructs client narratives into separate pieces of information, which the workers attempt to reconstruct back into coherent narratives. Using a street-level perspective, this article argues that the reconstructions are coping responses to fragmented information. Unlike traditional simplification responses, the workers complicate their perceptions of clients in the assessments. That is, street-level bureaucrats take “detours” to provide responsive services and manage the limitations of electronic government. Thus, this article provides an empirical contribution that also forms the basis for abductive theorization and suggests that the conceptual boundaries of coping strategies should be expanded to include “complication responses.” In contrast to the emphasis on face-to-face meetings in street-level literature, this article highlights the importance of texts.

Numerical analysis of the radiation-induced conductivity in polymers in a large-signal regime

We made numerical calculations of the radiation-induced conductivity by computing current densities, carrier concentrations, and internal electric fields in a disordered sample biased by constant applied voltage under a pulsed or step-function irradiation in a large-signal regime. For this purpose, we used the multiple trapping model featuring an exponential trap distribution with the dispersion parameter α. Calculations of radiation-induced conductivity were done with traditional simplifications (1D-analysis, one-carrier polymer, diffusion currents neglected, and non-injecting electrodes). The nonlinear effects accompanying the large-signal radiation-induced conductivity, such as an internal field variation, the bimolecular recombination, and the charge carrier extraction by electrodes, have been consistently accounted for. Numerical analysis agrees satisfactorily with the results of previously published analytical calculations.

3D building model simplification method considering both model mesh and building structure

AbstractThe simplification of three‐dimensional (3D) building models to improve rendering efficiency has gained widespread attention. To maintain the model's overall appearance features while increasing the simplification rate, we propose a novel 3D building simplification method that considers both the model mesh and building structure. The method divides a 3D building into a primary structure and subsidiary structures. It then organizes these structures using StructureTree, a multi‐way tree. The structures are organized according to the dependency relationships between building structures. When simplifying a building, the decision whether to simplify the mesh or remove the subsidiary structure in the leaf node of the StructureTree depends on the volume change caused by the edge collapse and the visual saliency of the removed structure. The experimental results show that our method exhibits a better simplification effect than the traditional simplification method, and the proposed method can achieve a high simplification rate while maintaining the simplification quality. Furthermore, the results of some spatial analyses based on the highly simplified building model are consistent with those of the original model.

STABILITY AND VIBRATIONS OF THE ELECTRONIC CLOSED SYSTEM STABILIZING THE COURSE OF A CAR WITH A TANK

To describe the disturbed movement of a car with a tank, a discrete mathematical model has been compiled, which allows one to take into account the oscillations of the free surface of the liquid and determine their effect on the directional stability of the car during uniform movement and during emergency braking. Linearization is carried out and an equation is obtained for the natural frequencies of oscillations of the electrohydromechanical system, which combines dynamic changes in the parameters of the movement of a car with a tank, partial layers of liquid in a tank and the operation of an electromagnetic drive of the control valve and an electronic PID controller for a two-circuit scheme to ensure directional stability. It is shown that low-frequency oscillations of the free surface of liquid lead to a significant reduction in the stability region, which indicates the need to take such oscillations into account when solving problems of analysis and synthesis of this system. It has been established that for a car with a tank, where low-frequency transverse oscillations of the liquid occur, which are accompanied by redistribution of mass and disturb the movement, an increase in the speed unambiguously leads to a deterioration in road-holding ability. This made it possible to exclude the speed from the variable parameters and significantly simplify the task. It was found that the liquid level in the tank, taking into account its connection with the maximum speed, has an ambiguous effect on the road-holding ability of the vehicle, and it is unacceptable to limit the research to calculations for 50 % of the load. Instead of this traditional simplification, it is necessary to find a line that bends from above those stability boundaries that correspond to many liquid levels from the entire range of their variation. It is shown that the dynamics of emergency braking weakly depends on the viscosity of the liquid in the tank, but with long-term continuous operation of the brake control system, self-oscillations appear in it. A method for tuning the parameters of an electronic regulator for low-amplitude self-oscillations is proposed.

Parameterization Framework and Quantification Approach for Integrated Risk and Resilience Assessments.

ABSTRACTA growing challenge for risk, vulnerability, and resilience assessment is the ability to understand, characterize, and model the complexities of our joint socioecological systems, often delineated with differing natural (e.g., watershed) and imposed (e.g., political) boundaries at the landscape scale. To effectively manage such systems in the increasingly dynamic, adaptive context of environmental change, we need to understand not just food web interactions of contaminants or the flooding impacts of sea level rise and storm surges, but rather the interplay between social and ecological components within the inherent and induced feedforward and feedback system mechanisms. Risk assessment, in its traditional implementation, is a simplification of a complex problem to understand the basic cause‐and‐effect relationships within a system. This approach allows risk assessors to distill a complex issue into a manageable model that quantifies, or semiquantifies, the effects of an adverse stressor. Alternatively, an integrated risk and resilience assessment moves toward a solution‐based assessment with the incorporation of adaptive management practices as 1 of 4 parts of system resilience (i.e., prepare, absorb, recover, and adapt), and directly considers the complexities of the systems being modeled. We present the Multilevel Risk and Resilience Assessment Parameterization framework for the systematic parameterization and deconstruction of management objectives and goals into assessment metrics and quantifiable risk measurement metrics and complementary resilience measurement metrics. As a proof‐of‐concept, the presented framework is paired with the Bayesian Network–Relative Risk Model for a human‐focused subset of a larger risk and resilience assessment of climate change impacts within the Charleston Harbor Watershed of South Carolina. This new parameterization framework goes beyond traditional simplification and embraces the complexity of the system as a whole, which is necessary for a more representative analysis of an open, dynamic complex system. Integr Environ Assess Manag 2021;17:131–146. © 2020 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC)

Evolutionary derivation of Runge–Kutta pairs for addressing inhomogeneous linear problems

Two new Runge–Kutta (RK) pairs of orders 6(4) and 7(5) are presented for solving numerically the inhomogeneous linear initial value problems with constant coefficients. These new pairs use only six and eight stages per step respectively. Six stages are needed for conventional Runge–Kutta pairs of orders 5(4) while for such a pair of orders 6(5) we use eight stages. Thus, our proposal is an improvement and it is achieved since the set of order conditions is smaller in the case of interest here. Since traditional simplifications for derivation of Runge–Kutta methods do not apply for this reduced set, we proceed using the differential evolution technique for solving it. We finalize by performing tests over some relevant problems with very pleasant results.

Numerical study of cavitation in centrifugal pump conveying different liquid materials

Abstract A numerical study on cavitation in the centrifugal pump during the transportation of pure water and diesel is carried out. An improved cavitation model based on the Zwart–Gerber–Belamri Model is employed in the simulation. A Cash–Karp fourth–fifth order Runge–Kutta method was used to solve the original Rayleigh-Plesset equation to get the numerical solution. The effects from viscosity and surface tension on bubbles’ expansion and compression are taken into account in the improved model instead of the traditional simplification in which the bubble radius is just a function of pressure and density. The coefficients got by fitting the numerical solution are added to the constant pre-multiplier of the Zwart-Gerber-Belrami cavitation model and finally enhance the model. The vapor volume fraction was predicted to be larger in diesel compared to water. The distribution of pressure in diesel is more homogenous than that in pure water.

Effects of Notch Filters on Imbalance Rejection With Heteropolar and Homopolar Magnetic Bearings in a 30-kW 60 000-r/min Motor

Active magnetic bearings (AMBs) have achieved great advantages in the high-speed and high-power-density rotating machine. Various vibration control strategies based on the notch filter have been reported to reduce the rotor imbalance vibration. But, the study is still insufficient to determine why the vibration gets reduced. This paper addresses a concise and direct explanation of the effects of notch filter on the rotor imbalance vibration with AMBs. An analytic solution for the synchronous response of rotor imbalance is introduced using the simple planar rotor model and general notch filter method. Then, combined with practical matters, the amplifier of a heteropolar radial AMB is further specified to uncover the effect of motion induced voltage to rotor self-centering, as a comparison with the homopolar radial AMB. Since the developed motor is equipped with both types of radial AMBs, a detailed control design is exhibited based on the dynamics of rigid body motion. The traditional simplification of two-plane separate control is improved, and a centralized controller is constructed. The effects of the rotor imbalance vibration rejection are demonstrated by the simulation results and experiments in a 30-kW 60000-r/min permanent magnet motor.

Numerical model of nonhydrostatic ocean dynamics based on methods of artificial compressibility and multicomponent splitting

An algorithm is proposed for solving three-dimensional ocean hydrodynamics equations without hydrostatic approximation and traditional simplification of Coriolis acceleration. It is based on multicomponent splitting of the modified model with artificial compressibility. The original system of equations is split into two subsystems describing the transport of three velocity components and adjustment of the density and velocity fields. At the adjustment stage, the horizontal velocity components are represented as a sum of the depth means and deviations; the two corresponding subsystems are derived. For barotropic dynamics, the compressibility effect is represented as the boundary condition at the free surface, while for the baroclinic subsystem, it is introduced as e-regularization of the continuity equation. Then, the baroclinic equations are split into two subsystems describing the hydrostatic and nonhydrostatic dynamics. The nonhydrostatic dynamics is computed at a separate splitting stage. The algorithm is included into the Institute of Numerical Mathematics of the Russian Academy of Sciences model based on “primitive” equations and verified by solving the hydrodynamics problem for the Sea of Marmara.

Cat-eye effect reflected beam profiles of an optical system with sensor array.

In this paper, we propose an applicable propagation model for Gaussian beams passing through any cat-eye target instead of traditional simplification consisting of only a mirror placed at the focal plane of a lens. According to the model, the cat-eye effect of CCD cameras affected by defocus is numerically simulated. An excellent agreement of experiment results with theoretical analysis is obtained. It is found that the reflectivity distribution at the focal plane of the cat-eye optical lens has great influence on the results, while the cat-eye effect reflected beam profiles of CCD cameras show obvious periodicity.

An evolutionary-based methodology for symbolic simplification of analog circuits using genetic algorithm and simulated annealing

In this paper, an evolutionary-based multi-objective criterion is introduced for simplified symbolic small-signal analysis of analog circuits containing MOSFETs. After circuit analysis via modified nodal analysis technique, the derived exact symbolic transfer function of the circuit behavior is automatically simplified. In contrast to traditional simplification criteria, the main objective of our criterion is to control the final simplification error rate. The proposed simplification methodology can be performed by such optimization algorithms as local-search algorithms, heuristic algorithms, swarm intelligence algorithms, etc. In this paper, a hybrid algorithm based on genetic algorithm and simulated annealing is applied to validate the proposed methodology. It is remarkable that all steps including netlist text processing, symbolic analysis, post-processing, simplification, and numerical analysis are consecutively derived in an m-file MATLAB program. The proposed methodology was successfully tested on three analog circuits, and the numerical results were compared with HSPICE.

Simplifying Fragmentation Patterns of Multiply Charged Peptides by N-Terminal Derivatization and Electron Transfer Collision Activated Dissociation

N-terminal peptide derivatization strategies used in conjunction with tandem mass spectrometry to yield simplified fragmentation patterns have shown limited success for the de novo sequencing of multiply charged peptides, including those predominantly formed in LC-ESI-MS experiments. Significant proton mobilization occurs for multiply charged peptides upon collisional activation, resulting in the formation of both N-terminal and C-terminal product ions rather than an exclusive series of C-terminal ions preferred for de novo sequencing algorithms. To circumvent this problem, multiply charged, N-terminally derivatized peptides were subjected to electron transfer reactions with fluoranthene anions to produce singly charged, radical species. Upon subsequent "soft" collision induced dissociation (CID), highly abundant z-type ions were formed nearly exclusively, which yielded simplified fragmentation patterns amenable to de novo sequencing methods. Furthermore, the derivatized peptides retained labile phosphoric acid moieties, and the enhanced set of z ions were also observed for peptides not possessing basic C-terminal residues, a type of peptide that poses more challenges to traditional simplification methods based on collision activated dissociation. This improved LC-MS(n) strategy was demonstrated for a variety of multiply charged model peptides and a tryptic digest of myoglobin.

Plant dispersal across multiple scales: linking models and reality

Plant dispersal across multiple scales: linking models and reality

Punctuated simplification of man-made objects

We present a simplification algorithm for manifold polygonal meshes of plane-dominant models. Models of this type are likely to appear in man-made environments. While traditional simplification algorithms focus on generality and smooth meshes, the approach presented here considers a specific class of man-made models. By detecting and classifying edge loops on the mesh and providing a guided series of binary mesh partitions, our approach generates a series of simplified models, each of which better respects the semantics of these kinds of models than conventional approaches do. A guiding principle is to eliminate simplifications that do not make sense in constructed environments. This, coupled with the concept of “punctuated simplification”, leads to an approach that is both efficient and delivers high visual quality. Comparative results are given.

A method to determine size-specific natural mortality applied to westcoast steenbras ( Lithognathus aureti) in Namibia

In traditional single-species fish stock assessment natural mortality is considered constant, independent of age or size. It is argued that predation mortality is generally related to prey size, that it decreases with increasing size and that such size-specific signals can best be detected in stocks that are close to a virgin state. Size-specific natural mortality rates of westcoast steenbras ( Lithognathus aureti) were determined by using length frequencies of rod-caught fish from a lightly exploited and closed population at Meob Bay, Namibia. It was assumed that natural mortality is inversely proportional to (body) length and approaching a constant minimum rate ( M ∞) as the fish grow bigger. Simple and new length-based catch curve methods were developed using the traditional simplification of neglecting variations in length at age. The von Bertalanffy growth parameters for annual mean growth as well as the coefficient of variation of length at age were estimated from analyzing age-length data. A simple deterministic simulation model was developed to examine the robustness of the methods and the impact of variability in individual growth. The model assumes that fish grow with a constant coefficient of variation in length at age. The simple method works within 10% precision criteria in most real cases. It is shown that overestimating mean length at old age ( L ̄ ∞) counteracts the effects of overlapping lengths for consecutive age groups. This fact can be used to estimate the fundamental mortality-to-growth ratio ( M ∞/ K) without any prior knowledge on growth. The application of M ∞ for steenbras to obtain size-specific natural mortality rate for silver kob ( Argyrosomus inodorus), as an input parameter for virtual population analysis, is also proposed.

Point representation versus solid representation of limb mass and its effect on the moment at a joint

Biomechanical models which assess spinal stresses require estimation of moments at various body articulations. One such moment is the moment due to a body segment mass at the segment's proximal joint. Traditionally, this moment is calculated by multiplying the body segment mass, assumed to be concentrated at the body segment's center of mass (point representation), by the distance of the center of mass from the proximal joint. This technical note describes a study undertaken to test the hypothesis that volumetric representation of a body segment's mass, which more accurately represents the distribution of the body segment's mass, would lead to a different moment at the proximal joint than the moment provided by the point representation of the body segment's mass. The hypothesis was tested on the forearm and moment at the elbow joint was calculated by both the point representation as well as the volumetric representation. No significant difference was found between the two values, thus indicating that traditional simplification to calculate such moments (point representation) is reasonable.

Shape optimization using the boundary element method with substructuring

AbstractApplications of the boundary element method for two‐ and three‐dimensional structural shape optimization are presented. The displacements and stresses are computed using the boundary element method. Sub‐structuring is used to isolate the portion of the structure undergoing geometric change. The corresponding non‐linear programming problem for the optimization is solved by the generalized reduced gradient method. B‐spline curves and surfaces are introduced to describe the shape of the design. The control points on these curves or surfaces are selected as design variables. The design objective may be either to minimize the weight or a peak stress of the component by determining the optimum shape subject to geometrical and stress constraints. The use of substructuring allows for problem solution without requiring traditional simplifications such as linearization of the constraints. The method has been successfully applied to the structural shape optimization of plane stress, plane strain and three‐dimensional elasticity problems.

Repeated impacts on a sinusoidally vibrating table reappraised

The traditional simplification for one commonly used example of repeated collisions is shown to be frequently erroneous for a wide range of coefficients of restitution. Bounded errors arise from an artificial speed constraint whose circumvention is largely but not exclusively unpredictable. Therefore exact equations, whose periodic solutions are detailed, should be generally used.