1,721,332 research outputs found
Hourly Particle Number Size Distribution (PNSD) measurements at Melpitz (2008)
No full textOne year of hourly Particle Number Size Distribution (PNSD) measurements at three different location with different air masses. Different kinds of Mobility Particle Size Spectrometers, MPSS has been used for the measurements.
---
Melpitz (2008), Central European background,
Neo (2012), Clean Remote background
Zeppelin (2010), Marine background
---
Melpitz: Lat 51.53 deg, Long 12.93 deg
Neo: Lat 36.83 deg, long 21.70 deg
Zeppelin: lat 78.90, long 11.86 de
Hourly Particle Number Size Distribution (PNSD) measurements at Neo (2012)
No full textOne year of hourly Particle Number Size Distribution (PNSD) measurements at three different location with different air masses. Different kinds of Mobility Particle Size Spectrometers, MPSS has been used for the measurements.
---
Melpitz (2008), Central European background,
Neo (2012), Clean Remote background
Zeppelin (2010), Marine background
---
Melpitz: Lat 51.53 deg, Long 12.93 deg
Neo: Lat 36.83 deg, long 21.70 deg
Zeppelin: lat 78.90, long 11.86 de
Hourly Particle Number Size Distribution (PNSD) measurements at Zeppelin (2010)
No full textOne year of hourly Particle Number Size Distribution (PNSD) measurements at three different location with different air masses. Different kinds of Mobility Particle Size Spectrometers, MPSS has been used for the measurements.
---
Melpitz (2008), Central European background,
Neo (2012), Clean Remote background
Zeppelin (2010), Marine background
---
Melpitz: Lat 51.53 deg, Long 12.93 deg
Neo: Lat 36.83 deg, long 21.70 deg
Zeppelin: lat 78.90, long 11.86 de
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Auswirkungen von Verschmutzung auf konzentrierende solarthermische Kraftwerke
No full textThe soiling of solar mirrors compromises significantly the efficiency of concentrating solar power (CSP)-plants. It causes a partial loss of incoming radiation when being
reflected at the mirror surfaces of the solar field. This reduces the output of the power plant or causes increased cleaning costs. Many potential CSP-sites lack
information on soiling. In this thesis measurement methods are presented to quantify the effect of soiling. The collected data is applied in a financial yield analysis study and a statistical analysis concerning the meteorological causes of
soiling. A novel measurement device called Tracking Cleanliness Sensor (TraCS) is presented. It is an accessory to an existing irradiance measurement station with a
solar tracker. It consists of a second pyrheliometer that is installed to measure the direct normal irradiance as reflected by a sample mirror. Comparing the reflected
to the directly measured DNI is a measurement for the reflectivity of the sample mirror. The parameter cleanliness is calculated by comparing the reflectivity of a soiled mirror to its reflectivity in the clean state. In a next step, the soiling-rate is calculated. The soiling-rate is defined as the daily loss of cleanliness with time. TraCS is a low cost instrument that requires little additional maintenance. Further advantages compared to currently employed measurement methods are its high time resolution, the use of the current sun spectrum and the measurement of a
large mirror surface area of 30 cm2. A soiling-rate dataset of 1, 5 years measured at Plataforma Solar de Almería (PSA) in Spain in daily time resolution is presented
and analyzed. The mean soiling-rate is - 0, 0052 /Tag.
The dataset is applied in a yield analysis study for two types of power plants at two different sites. The focus lies on the exact reproduction of cleaning activities and costs. Adjustment of cleaning activities to a daily measurement of the soilingrate can increase the profit of a power plant project over its lifetime. Candidate cleaning strategies are compared to a constant cleaning activity with one vehicle
(reference). The increase in profit ranges up to 2, 6 %. In existing yield analysis software packages the mean cleanliness of the solar field (xFeld) is assumed as
constant. Setting xFeld equal to the yearly mean value of xFeld resulting from the reference strategy and calculating the yearly monetary yield results in a 0, 58 %
higher profit than that resulting from a time resolved xFeld. The assumption of a constant xFeld overestimates the project’s revenues in this case because the different
weighting of daily DNI-sums by xFeld is not accounted for. Time resolved soiling-rate measurements therefore are an important pre-requisite for the correct estimation of yield analysis studies and optimization of cleaning activities.
In a next step, the soiling-rate dataset is compared to the simultaneously measured weather parameters airborne particle mass concentration, diffuse irradiance, dew, wind speed, wind direction, relative humidity and combinations of the latter. It follows, that the particle mass concentration for particles up to 10 �m (PM10) correlate best with the soiling rate. The adherence of particles of this size class to the mirror surface is potentiated by the occurence of dew. On days where particles impact mainly perpendicular to the mirror surface, the correlation coefficients between PM10 and the soiling-rate are higher for many subperiods of two to four vii months. The slopes of linear fits between soiling-rate and the investigated weather parameters vary with time. This can be explained by alternating properties of the adhered particles. For the definition a general model, further measurement parameters have to be included. The novel instrument TraCS enables measurements of time-resolved soilingdatasets. These are necessary for a refinement of yield analysis and the development of improved cleaning strategies as shown here. The influence of several weather
parameters on the soiling-rate has been identified
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Verknüpfung aerodynamischer und optischer Eigenschaften nichtkugelförmiger atmosphärischer Grobstaubpartikel
Full text linkDie entsprechend der Quellstärke größte Fraktion des atmosphärischen Aerosols ist der natürliche Grobstaub (Seesalz, Mineralstaub und primär biologische Partikel). Nahezu alle natürlichen Grobstaubpartikel in trockener Phase weisen mehr oder weniger starke Abweichungen von der sphärischen Form auf. Der Einfluss der Asphärizität auf die aerodynamischen und optischen Eigenschaften kann durch sogenannte Formfaktoren unter Verwendung einer Referenzgröße berücksichtigt werden. Für wissenschaftliche Fragestellungen, die sowohl auf aerodynamischen wie auch optischen Aspekten beruhen, bedarf es einer vollständigen Betrachtung des Einflusses der Partikelmorphologie, um ein physikalisch plausibles Ergebnis zu erhalten.
Gegenstand dieser Arbeit ist die Analyse der Relationen zwischen aerodynamischen und optischen Eigenschaften. Ziel ist die approximative Darstellung der optischen Formfaktoren durch den aerodynamischen Formfaktor als Maßzahl der Asphärizität. Hierfür wurden sowohl geometrische Formparameter als auch aerodynamische und optische Formfaktoren für ein Ensemble von regelmäßigen und unregelmäßigen Partikeln simuliert. Der Approximation der optischen Formfaktoren durch den aerodynamischen Formfaktor werden theoretische Überlegungen und Ergebnisse numerischer Simulationen vorangestellt. Die optischen Formfaktoren sind dabei primär eine Funktion des Größenparameters (Partikelgröße und Wellenlänge) und des aerodynamischen Formfaktors. In Laborexperimenten wurden beide Abhängigkeiten unter Verwendung von Proben mit Partikeln unterschiedlicher Asphärizität validiert. Die resultierende Approximation ermöglicht eine einfache und konsistente Beschreibung des Einflusses der Partikelmorphologie auf die aerodynamischen und optischen Eigenschaften. Dies ist eine unabdingbare Voraussetzung für eine genauere Analyse von Partikeleigenschaften, die aus aerodynamisch und optisch basierten In-situ-Messungen abgeleitet werden
Experimental determination of the mass deposition flux of mineral dust at the Cape Verde Islands
Full text linkDer Eintrag von Mineralstaub in den Ozean geschieht entweder durch trockene oder durch nasse Deposition. Dies ist ein wichtiger Prozess um ozeanische Organismen wie Phytoplankton mit Nährstoffen (z.B. Nitrat, Phosphat oder Eisen) zu versorgen. Viele Modelle befassen sich mit der Simulation von Depositionsflüssen von Mineralstaub in den Ozean. Messungen von Massendepositionsflüssen von Mineralstaub sind hingegen selten. Daher ist es von großer Notwendigkeit, diese Messungen durchzuführen um die vielen Modelle zu validieren und den Mineralstaubzyklus besser zu verstehen.
Innerhalb des SOPRAN Projektes (Surface Ocean PRocesses in the ANthropocene) wird der Materialtransport zwischen der Atmosphäre und dem Ozean untersucht. Die Messungen dafür wurden auf den Kapverdischen Inseln durchgeführt, über welchen der Saharastaub durch die Passatwindzirkulation vorwiegend transportiert wird. Im Rahmen dieser Arbeit werden in-situ Messungen von trockener Deposition von Mineralstaub in den Ozean präsentiert. Verschiedene Methoden wurden auf ihre Anwendbarkeit getestet und deren Ergebnisse miteinander verglichen. Alle Messergebnisse liegen im Bereich der Messunsicherheiten, wodurch ein Satz qualitätsgesicherter Daten aufgebaut werden konnte. Diese Daten wurden mit den Ergebnissen eines regionalen Chemie-Transport Modells verglichen. Modellierte Massendepositionsflüsse von Mineralstaub waren manchmal doppelt so hoch wie gemessene. Die größte Unsicherheit der Modelle liegt in der Emission des Mineralstaubs, die im Transport und der Deposition fortgesetzt wird. Weitere Unterschiede entstehen durch den Vergleich von Punktmessungen mit einer Gitterzelle, wenn der Staub nicht gleichmäßig über die Gitterzelle verteilt ist.
Zusammenfassend wurden Massendepositionsmessungen von Mineralstaub erfolgreich mit verschiedenen Methoden durchgeführt. Mit den Erfahrungen aus dieser Studie ist es nun möglich, Langzeitmessungen von Mineralstaubdeposition in den Ozean erstellen. Diese Daten können von Atmosphärenmodellierern für ihre Modellvalidierung genutzt werden. Anwender von Ozeanmodellen und SOPRAN Partner werden diese Ergebnisse nutzen um z.B. die ozeanische Reaktion auf den Mineralstaubeintrag zu untersuchen.The input of mineral dust to the oceans, via dry or wet deposition, is an important process, because the entrainment of nutrients (e.g., Nitrate, Phosphor and Iron) is essential for oceanic life such as phytoplankton. A lot of effort has been done to model the dust deposition fluxes to the ocean. However, field measurements concerning the deposition flux are sparse. Therefore, those measurements are needed in order to verify the huge amount of model outputs and to better understand the mineral dust cycle.
Within the project SOPRAN (Surface Ocean PRocesses in the ANthropocene), the influence of material exchange between the atmosphere and the ocean is investigated. Measurements were carried out at the Cape Verde Islands in the direct outflow of the Saharan Desert. This study presents the first in-situ measurements of the dry mass deposition flux of mineral dust to the ocean. The applicability of different methods was tested and the results were compared to each other. The results of the measured data were comparable and a set of quality assured data could be built up. Those results were compared to the output of a regional chemistry- transport model. The modeled mass deposition flux was sometimes double as high as the measured one. The main uncertainty of the models is the emission of mineral dust at the source region, proceeding in the transport and emission of mineral dust. Furthermore, comparing single point measurements with outputs of a grid cell leads to differences in deposition fluxes by an inhomogeneous distribution of the mineral dust layer.
Summarizing, the measurements of the mass deposition flux of mineral dust could be performed successfully with several methods. With the expertise of this study, long-term observations of the mineral dust deposition to the ocean can now be established. These data can be used by atmosphere modelers to validate their models. Ocean modelers and partners of the SOPRAN project will use these data to investigate e.g., the biological response of the ocean to mineral dust entrainment
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
