Parameterized Description Research Articles

Parameterized data handling for forming tool tryout: reverse engineering, data consolidation and springback compensation

The forming tool design process generates large amounts of data up to the first falling parts. On the one hand, simulation results, geometric measurements and design models originate from different software tools, which leads to a non-consolidated set of data inventory. On the other hand, the total data volume is hard to handle economically. A stable and user-friendly data structure for overarching tool tryout is missing. Often several experience-based iterations are necessary to derive the tool’s working surfaces, which is both time- and resource consuming and even may lead to postponed start of production. Meanwhile, early-generated data does not involve into the manual optimization process. Therefore, in this paper a parameterized data handling methodology is introduced, which enables systematic reverse engineering, data consolidation, and springback compensation. Each generated dataset during tryout is traced back to a mathematical description of geometry using so called control points (B-Spline model). Through, the parameterized description, the different data formats interact straightforward and need minimum storage. The developed concept is demonstrated for the springback analysis of a forming component using design models and numerical data.

Optimization Design of Cable-Frame Antennas Based on Tension Compensation Method

Tension truss reflectors are flexible structures characterized by strong geometric nonlinearities, thus the surface error and the real cable tensions of a reflector cannot be controlled efficiently to anticipant levels by their initial cable tensions. To ensure both appropriate node positions and anticipant cable tensions, an optimization method based on Tension Compensation Method is presented. First, a parameterized description of the zero-stress states of the front net and the rear net is proposed and the strategy of Tension Compensation Method is used to control the cable tensions to anticipant levels. Second, a mathematical optimization model for the cable tensions and the zero-stress state design of the cable network is established based on Tension Compensation Method with the optimization target of minimizing surface error of the reflector. Finally, the feasibility and effectiveness of the presented method are validated by some numerical examples. The results show that the cable tensions can be effectively controlled by the proposed method, and this method can generate regular zero-stress states of the cable-nets which may bring great convenience to the lofting work of the cable network.

A new method of discrete optimization for cross-section selection of truss structures

The main goal of this article is to develop a new method of discrete optimization for cross-section selection of truss structures. First, it introduces a parameterized description of discrete cross-section areas in an admissible list, which is an ordered list of manufacturing available cross-section areas (i.e. the ‘available list’ of cross-section areas) and constructs a discrete optimization model for truss structures. Secondly, the generalized shape function-based parameterization (GSFP) method is proposed to transform discrete variables obtained previously into continuous ones, thus transforming the discrete optimization problem into a continuous optimization problem which can be readily solved with gradient-based methods. Thirdly, by comparing the influences of different admissible lists formed with elements of the same available list, on the convergences of the optimization process, an ordering rule is proposed to determine the order of elements in the admissible list. Lastly, the proposed method is applied to several benchmark design examples, generating results with similar or improved accuracy compared to those from heuristic methods, showing significantly improved computational efficiency. The method is shown to be accurate and efficient, which would prove especially beneficial to large-scale problems.

Reverse Engineering of Turbocharger Compressor Designs Based on Non-Parametric CAD Data

The improvement of turbocharger components-such as compressor-by means of virtual methods can be done most efficiently if those component’s geometries are given in a parameterized format. It is shown here how the geometric description of turbocharger compressors that have a neutral format (ASCII or STEP/IGES) can be transformed in a parameterized description. This description is then used to perform parameter variations which are validated via simulation methods like CFD. The parameterization of the geometry is therefore a very important step within the workflow of the virtual design of turbocharger components as without it the investigation of different geometries are very time-consuming and expensive.

Prioritizing Information Technology Service Investments under Uncertainty

We explore the challenge of selecting the best among a set of alternative IT investments. Solving this problem is important since the difference between alternative investment options may be drastic in terms of business results, both positive and negative. The resulting model takes as input a set of investment alternatives and a parameterized description of IT services, and provides as output a Preference Index for each alternative. The solution takes into account such characteristics as epistemic and aleatory uncertainty as well as the decision maker's attitude toward risk. Through a case study and a sensitivity analysis, we conclude that the model is useful in practice and robust; we also describe its domain of validity.

An architecture based on reconfigurability and asynchronism for real-time image processing

This paper presents the evolution of the Associative Mesh, a massively parallel SIMD architecture based on reconfigurability and asynchronism. To favor its System on Chip implementation, we introduce a reorganization of the structure based on processors virtualization and evaluate its consequences on hardware cost and algorithmic performances. Using an evaluation environment based on a programming library and a parameterized description of the architecture, we show that a virtualized Associative Mesh achieves real-time execution for a number of complex image processing algorithms, including split and merge segmentation, watershed segmentation and motion detection.

Cold atom interferometer in a satellite: orders of magnitude of the tidal effect

We consider an experiment in which an atomic wave interferometer is tied to a telescope pointing towards a faraway star in a nearly free falling satellite. Such a device is sensitive to the acceleration and the rotation relatively to the local inertial frame, as well as to the tidal gravitational effects which are considered here as a perturbation to the signal. We present briefly the method to calculate the rotation of the telescope due to the aberration and the deflection of the light in the gravitational field of a central mass. Within the framework of a general parameterized description of the problem, we discuss the contributions which must be taken into account in order to observe a specific process. We study the case of a satellite orbiting around the Earth, Jupiter and the Sun in order to measure the Lense–Thirring effect.

Experimental estimation of the spatial statistics of turbulence-induced index of refraction fluctuations in the upper atmosphere.

We present results from an experiment to estimate the parameters of homogeneous, isotropic optical turbulence in the upper atmosphere. The balloon-borne experiment made high-resolution temperature measurements at seven points on a hexagonal grid for altitudes from 12,000 to 18,000 m. From the temperature data, we obtained index of refraction fluctuations that can be used to compute a sample-based estimate for a parameterized description of the spatial autocorrelation of the turbulence. The three parameters of interest were a proportionality constant Pc, the power-law parameter alpha, and the outer scale L0. The results obtained for Pc are within the expected range and agree well with independent measurements made from a standard rising thermosonde measurement made approximately simultaneously with the data collection. Values for a were in the range 1.52 < or = alpha < or = 1.73 were observed, which are significantly less than the power law used in the Kolmogorov and von Karman models, alpha = 1.833. Values observed for L0 were in the range 5 < or = L0 < or = 19 m. Evidence that alpha may be consistently less than that used in the Kolmogorov and von Karman models likely has the most significant implications for systems that must work in or through the tropopause.

Evolution of rain water profiles resulting from pure sedimentation: Spectral vs. parameterized description

The paper focuses on a comparison of solutions of the budget equations for specific moments of a hydrometeor size distribution, simplified to the problem of pure drop sedimentation, as following from models with a one-moment or a two-moment parameterization of microphysical processes and from a reference model based on spectral treatment of sedimentation. The solutions for the transient vertical profiles of liquid water content show remarkable differences in their spatial structure: starting from an idealized, discontinuous initial profile in form of a square wave, shock and rarefaction waves evolve in the parameterized models, while the reference solution describes a smooth distribution. These principle differences follow from the fact, that the budget equations for the moments in the parameterized models are of the form of quasi-linear advection equations, with the decisive nonlinearity arising from the parameterization relation for the sedimentation flux, whereas the reference solution follows from a linear partial differential equation. Hence, the quasi-linear shock effects have to be interpreted as a mathematical artifact of the parameterization assumptions. The differing evolution of the liquid water profiles finds expression in remarkable differences in the time series of surface precipitation rate for the spectral and parameterized models.

High-speed customizable fuzzy-logic processor: architecture and implementation

A generic field-programmable logic device (FPLD)-based fuzzy logic system aimed at high-speed applications that can be easily customized for practically any application is presented. It implements fuzzy logic systems that vary in terms of the numbers of inputs and outputs and their accuracy, the membership functions (MFs), fuzzy rules, and the speed at which new outputs have to be generated. This is achieved by using the sysstem's unique architecture and its parameterized description, which is based on VHDL generics. The system can be used as either a stand-alone system or as an application-specific co-processor added to standard or customized microprocessors.

On the effective coupling of optimization algorithms to solve inverse problems of electromagnetism

The hybrid optimization tool presented in this paper combines generational genetic algorithms (GA) and variable metric (VM) optimizers. Both GA and VM may deal with the same, parameterized description of the inverse problem and a switch from GA to VM is being made automatically. GA is used to locate a subdomain in the design variables space containing the global minimum of the objective function. This global minimum may be found then, quickly and precisely, with the deterministic optimizer. The crucial concern of the hybrid algorithm design is to switch from stochastic to deterministic algorithm is such a way as to ensure that the global solution will be found in the fastest way. The article is focused on the algorithm which is able to determine whether GA has already found the desired subdomain described above. This algorithm is based on the cluster analysis using seed points and density‐determined hyperspheres.

Bipolar, Collimated Outbursts in the Planetary Nebula Hb 4

Spatially resolved profiles of the Hα and [N II] 6548, 6584 A emission lines obtained with the Manchester Echelle Spectrometer combined with the 2.1 m San Pedro Martir telescope have revealed the remarkable velocity structure in the peculiar planetary nebula Hb 4. The compact, elliptical core shows a moderate splitting in the [N II] 6584 A line profiles of only 2Vexp = 43 km s-1. However, the detection of high velocities in the nebular line profiles from the elongated, ionized knots protruding symmetrically on both sides of the core give direct evidence of the presence of highly collimated outflows in Hb 4. The line profiles in these symmetric, elongated knots are complex, with radial velocities of ±150 km s-1 with respect to the systemic radial velocity and detached emission regions at further extreme radial velocities. The long-slit spectra are analyzed with a parameterized description of the emissivity and velocity field of the fast-moving, collimated, ionized flow. The observed profiles are simulated in detail by a model of the emission from a bow shock at the head of the jet followed by a faster high-density component. In Hb 4 we are probably observing the first stages of intermittent outflows that could develop into episodic two-sided jets, as observed in the case of the planetary nebula Fleming 1.

Interstate Mortality Differentials in the United States: a parameterized Description

La mortalité différentielle aux États-Unis : une description paramétrée. L'article traite de la mortalité différentielle entre états américains de 1979 à 1981. Il s'ouvre sur un rapide panorama sur les données, qui révèle des contrastes étonnamment larges d'espérance de vie entre états. Les auteurs ont construit un modèle de mortalité d'Heligman-Pollard à partir des paramètres de valeurs similaires qui met en évidence l'existence de plusieurs familles de profils de mortalité par âge, leurs caractéristiques principales et les différences entre états.