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  • MECHANICAL ENGINEERING  (1)
  • Mixed-layer dynamics  (1)
  • 1995-1999  (2)
  • 1975-1979
  • 1950-1954
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Boundary layer meteorology 93 (1999), S. 47-73 
    ISSN: 1573-1472
    Keywords: Boundary-layer model ; Mixed-layer dynamics ; Organized large eddies ; Ekman flow ; Cold-air outbreak
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The internal thermal boundary layer developing over the Mediterranean during a cold-air outbreak associated with a Tramontane event has been studied by means of airborne lidar, in situ sensors, and a modelling approach that consisted of nesting the University of Washington (UW) planetary boundary-layer (PBL) model in an advective zero-order jump model. This approach bypasses some of the deficiencies associated with each model: the absence of the dynamics in the mixed layer for the zero-order jump model and the lack of an inversion at the PBL top for the UW PBL model. Particular attention is given to the parameterization of the entrainment flux at the PBL top. Values of the entrainment closure parameter derived with the model when matching PBL structure observations are much lower than those derived with standard zero-order jump models. They also are in good agreement with values measured in different meteorological situations by other studies. This improvement is a result of the introduction of turbulent kinetic energy production in the mixed layer.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2019-06-28
    Description: A wheeled exploratory vehicle is under construction at the Mars Mission Research Center at North Carolina State University. In order to serve as more than an inspection tool, this vehicle requires the ability to interact with its surroundings. A crane-type manipulator, as well as the necessary control hardware and software, has been developed for use as a sample gathering tool on this vehicle. The system is controlled by a network of four Motorola M68HC11 microcontrollers. Control hardware and software were developed in a modular fashion so that the system can be used to test future control algorithms and hardware. Actuators include three stepper motors and one solenoid. Sensors include three optical encoders and one cable tensiometer. The vehicle supervisor computer provides the manipulator system with the approximate coordinates of the target object. This system maps the workspace surrounding the given location by lowering the claw, along a set of evenly spaced vertical lines, until contact occurs. Based on this measured height information and prior knowledge of the target object size, the system determines if the object exists in the searched area. The system can find and retrieve a 1.25 in. diameter by 1.25 in. tall cylinder placed within the 47.5 sq in search area in less than 12 minutes. This manipulator hardware may be used for future control algorithm verification and serves as a prototype for other manipulator hardware.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-197423 , NAS 1.26:197423
    Format: application/pdf
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