Browsing by Subject "Ultraviolet"

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    A scanning eye-safe rotational Raman lidar in the ultraviolet for measurements of tropospheric temperature fields
    (2009) Radlach, Marcus; Wulfmeyer, Volker
    Within the frame of the virtual Institute COSI-TRACKS the first scanning rotational Raman lidar has been developed and deployed successfully in two large field campaigns. This has allowed new investigations of the convective boundary layer and contributed to studies on the initiation of convection during the PRINCE campaign (PRediction, Identification and trackiNg of Convective cElls) in July 2006 and the COPS experiment (Convective and Orographically-induced Precipitation Study) from June to August 2007. The University of Hohenheim rotational Raman lidar was deployed in both these campaigns on Hornisgrinde (48.61 °N, 8.20 °E, 1161 m above sea level), the highest peak in the Northern Black Forest in southwest Germany. The lidar provides measurements of atmospheric temperature fields in the troposphere with high spatial and temporal resolution at day and night. Daytime scanning temperature measurements within a range of 3 km using a temporal resolution of 169 s and a moving average of 300 m in range show statistical temperature uncertainties of less than 1 K while pointing at 21 directions. Temperature uncertainties of less than 1 K are achieved during nighttime up to a range of 8 km using a temporal resolution of 3 minutes and a range resolution of 300 m. The lidar resolves also turbulence in the convective boundary layer, e.g., at 470 m height with a temporal resolution of 10 s and statistical uncertainties of only 0.41 K. In addition to temperature, also the particle backscatter coefficient and the particle extinction coefficient are measured independently. The instrument operates with a primary wavelength of 355 nm. This has instrumental advantages compared to 532 nm but also yields eye-safety beyond a range of 500 m which facilitates the deployment. Highly efficient spectral separation of the atmospheric backscatter signals is performed by a polychromator with narrow-band interference filters in a sequential setup. The spectral characteristics of these filters were optimized with respect to high measurement performance in the daytime planetary boundary layer and the lower free troposphere. Pioneering measurements of the 2-dimensional temperature distribution in the lower troposphere in the vicinity of a mountain ridge are presented.
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    Drying behavior and curcuminoids changes in turmeric slices during drying under simulated solar radiation as influenced by different transparent cover materials
    (2022) Komonsing, Nilobon; Reyer, Sebastian; Khuwijitjaru, Pramote; Mahayothee, Busarakorn; Müller, Joachim
    Dried turmeric is used as a spice and traditional medicine. The common drying methods for turmeric (Curcuma longa L.) are sun drying and solar drying. In this study, turmeric slices with a thickness of 2 mm were dried at 40, 50, 60, and 70 °C in a laboratory hot-air dryer with a simulated solar radiation applied through transparent polycarbonate cover (UV impermeable) and PMMA cover (UV permeable). Air velocity and relative humidity of drying air were fixed at 1.0 M·s−1 and 25 g H2O kg−1 dry air, respectively. Light significantly increased the sample temperature under both covers. Page was the best model to predict the drying characteristics of turmeric slices. Drying rate correlated with the effective moisture diffusivity, which increased at higher temperature. The hue angle (h°) of turmeric was distinctly lower at 70 °C under both covers. The dried products were of intensive orange color. Curcumin, demethoxycurcumin, and total curcuminoids were affected by the cumulated thermal load (CTL). The lowest curcumin content was found at 40 °C under PMMA (highest CTL). The optimum drying condition was 70 °C under polycarbonate cover due to shorter drying time and better preservation of color and curcuminoids in the dried product.