Aufbereitung meteorologischer Daten zur Unterstützung einer globalen agrarmeteorologischen Beratung

<p>Im Rahmen einer agrarmeteorologischen Beratung ist die Berechnung der Verdunstung für spezifische Agrarkulturen mit geeigneten Modellen möglichst auf einer stündlichen Zeitskala erforderlich. Im DWD ist hierzu das Modell AMBAV (Agrarmeteorologisches Modell zur Berechnung der aktuellen Verdunstung) entwickelt worden und wird für die nationale agrarmeteorologische Beratung operationell mit Vorhersagedaten und für Wirkanalysen auch mit Klimadaten verwendet. Insbesondere hinsichtlich globaler Anwendungen liegen gemessene oder mit Klimamodellen berechnete meteorologische Datenzeitreihen häufig nur für eine tägliche Zeitskala, oder als Modelldaten für ausgewählte Elemente bestenfalls in einer 6-stündigen Zeitskala, vor. Dies sind Tagesmittel oder Tagessummen (z.B. Wind bzw. Globalstrahlung und Niederschlag) sowie gegebenenfalls tägliche Extremwerte (Minimum und Maximum der Lufttemperatur, stärkste Tagesböe).</p> <p>Zur Bereitstellung stündlicher Daten aus Tagesdaten wurde daher ein Präprozessor entwickelt, der gemessene Stationsdaten (Modus „Station“) oder modellierte Daten globaler Modelle (Modus „Gitter“) verwendet. Dabei wurde vorausgesetzt, dass im Vorfeld einer Erarbeitung von zeitlichen Disaggregierungsverfahren keine umfangreichen Klimaanalysen durchgeführt werden müssen sondern weitestgehend auf Erfahrung zurückgegriffen werden kann. Vorhandene Programme (z.B. MELODIST) konnten jedoch wegen teilweise anderer Zielstellung oder Datenanforderungen nicht ohne weiteres verwendet werden. So wurde z.B. für die Tagessumme der Globalstrahlung auf das Angström-Verfahren (FAO, 1998), für den Niederschlag auf das Kaskadenverfahren nach Olsson (1998), für die Lufttemperatur auf den „sin-exp-Ansatz“ nach Parton und Logan (1981) und für den Wind auf die „normierte Böen­geschwindigkeit“ (Verkaik, 2000) zurückgegriffen. Für erforderliche Interpolationen werden das Newton-Verfahren und das „cubic hermite spline“ verwendet.</p> <p>Die vorgestellten Verfahren werden mit Stationsdaten des ZAMF und beispielhaft mit Modelldaten des GFCS für Madagaskar angewendet.</p> <p><strong>Literatur</strong></p> <p>FAO (Food and Agriculture Organization), 1998: Crop evaporation – Guidelines for computing crop water requirements. Irrigation and Drainage Paper 56, 300 p.</p> <p>Olsson, J., 1998: Evaluation of a scaling cascade model for temporal rainfall disaggregation. Hydrology and Earth System Sciences, 2, p.19-30.</p> <p>Parton, W.J. and J.A. Logan, 1981: A model for diurnal variation in soil and air temperature. Agricultural Meteorology, 23, p.205-216.</p> <p>Verkaik, J.W., 2000: Evaluation of two gustiness models for exposure correction calculations. Journal of Applied Meteorology, 39, p.1613-1626.</p>

Adjustable Piecewise Quartic Hermite Spline Curve with Parameters

In this paper, the quartic Hermite parametric interpolating spline curves are formed with the quartic Hermite basis functions with parameters, the parameter selections of the spline curves are investigated, and the criteria for the curve with the shortest arc length and the smoothest curve are given. When the interpolation conditions are set, the proposed spline curves not only achieve C1-continuity but also can realize shape control by choosing suitable parameters, which addressed the weakness of the classical cubic Hermite interpolating spline curves.

Geodesic Hermite Spline Curve on Triangular Meshes

Curves on a polygonal mesh are quite useful for geometric modeling and processing such as mesh-cutting and segmentation. In this paper, an effective method for constructing C1 piecewise cubic curves on a triangular mesh M while interpolating the given mesh points is presented. The conventional Hermite interpolation method is extended such that the generated curve lies on M. For this, a geodesic vector is defined as a straightest geodesic with symmetric property on edge intersections and mesh vertices, and the related geodesic operations between points and vectors on M are defined. By combining cubic Hermite interpolation and newly devised geodesic operations, a geodesic Hermite spline curve is constructed on a triangular mesh. The method follows the basic steps of the conventional Hermite interpolation process, except that the operations between the points and vectors are replaced with the geodesic. The effectiveness of the method is demonstrated by designing several sophisticated curves on triangular meshes and applying them to various applications, such as mesh-cutting, segmentation, and simulation.

Existence and Uniqueness of Weak Solutions for a New Class of Convex Optimization Problems Related to Image Analysis

This paper proposes a new anisotropic diffusion model in image restoration that is understood from a variational optimization of an energy functional. Initially, a family of new diffusion functions based on cubic Hermite spline is provided for optimal image denoising. After that, the existence and uniqueness of weak solutions for the corresponding Euler–Lagrange equation are proven in an appropriate functional space, and a consistent and stable numerical model is also shown. We complement this work by illustrating some experiments on different actual brain Magnetic Resonance Imaging (MRI) scans, showing the proposed model’s impressive results.

Genetic Optimization of a Manipulator: Comparison between Straight, Rounded, and Curved Mechanism Links

There are several ubiquitous kinematic structures that are used in industrial robots, with the most prominent being a six-axis angular structure. However, researchers are experimenting with task-based mechanism synthesis that could provide higher efficiency with custom optimized manipulators. Many studies have focused on finding the most efficient optimization algorithm for task-based robot manipulators. These manipulators, however, are usually optimized from simple modular joints and links, without exploring more elaborate modules. Here, we show that link modules defined by small numbers of parameters have better performance than more complicated ones. We compare four different manipulator link types, namely basic predefined links with fixed dimensions, straight links that can be optimized for different lengths, rounded links, and links with a curvature defined by a Hermite spline. Manipulators are then built from these modules using a genetic algorithm and are optimized for three different tasks. The results demonstrate that manipulators built from simple links not only converge faster, which is expected given the fewer optimized parameters, but also converge on lower cost values.

Interpolating Industrial Robot Orientation with Hermite Spline Curve Based on Logarithmic Quaternion

Smooth orientation planning has an important influence on the working quality and service life as for industrial robot. Based on the logarithmic quaternion, a compact method to map a spline curve from Cartesian space to quaternion space is proposed, and consequently the multi-orientation smooth interpolation of quaternion is realized. Combining with the relevant example case, the detailed method and steps of multi-orientation interpolation are introduced for mapping Hermite spline curve into quaternion space, and the validity of the principle is verified by using the example case. The present multi-orientation smooth interpolation of quaternion has the characteristics of simple construction, easy implementation and intuitive understanding. The method is not only applicable to multi-orientation interpolation of quaternion with Hermite spline curve, but also can extended to the spline curves such as Bezier spline and B-spline.