92 research outputs found

    Active learning with kernel machines

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    Klaus BrinkerPaderborn, Univ., Diss., 200

    High Precision Temperature Control of Normal-conducting RF GUN for a High Duty Cycle Free-Electron Laser

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    High precision temperature control of the RF GUN is necessary to optimally accelerate thousands of electrons within the injection part of the European X-ray free-electron laser XFEL and the Free Electron Laser FLASH. A difference of the RF GUN temperature from the reference value of only 0.01 K leads to detuning of the cavity and thus limits the performance of the whole facility. Especially in steady-state operation there are some undesired temperature oscillations when using classical standard control techniques like PID control. That is why a model based approach is applied here to design the RF GUN temperature controller for the free-electron lasers. A thermal model of the RF GUN and the cooling facility is derived based on heat balances, considering the heat dissipation of the Low-Level RF power. This results in a nonlinear model of the plant. The parameters are identified by fitting the model to data of temperature, pressure and control signal measurements of the FLASH facility, a pilot test facility for the European XFEL. The derived model is used for controller design. A linear model predictive controller was implemented in MATLAB/Simulink and tuned to stabilize the temperature of the RF GUN in steady-state operation. A test of the controller in simulation shows promising results

    Pediatric DXA: clinical applications

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    Normal bone mineral accrual requires adequate dietary intake of calcium, vitamin D and other nutrients; hepatic and renal activation of vitamin D; normal hormone levels (thyroid, parathyroid, reproductive and growth hormones); and neuromuscular functioning with sufficient stress upon the skeleton to induce bone deposition. The presence of genetic or acquired diseases and the therapies that are used to treat them can also impact bone health. Since the introduction of clinical DXA in pediatrics in the early 1990s, there has been considerable investigation into the causes of low bone mineral density (BMD) in children. Pediatricians have also become aware of the role adequate bone mass accrual in childhood has in preventing osteoporotic fractures in late adulthood. Additionally, the availability of medications to improve BMD has increased with the development of bisphosphonates. These factors have led to the increased utilization of DXA in pediatrics. This review summarizes much of the previous research regarding BMD in children and is meant to assist radiologists and clinicians with DXA utilization and interpretation

    On the issue of transparency and reproducibility in nanomedicine.

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    Following our call to join in the discussion over the suitability of implementing a reporting checklist for bio-nano papers, the community responds

    Linguistiche textanalyse : eine einfuhrung in grundbegriffe und methoden

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    Grundlagen der germanistik:29151 p.; 21 cm
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