Paleophysiology of Permian and Triassic Seed Plants

This study utilized both anatomically and morphologically preserved fossil plants to investigate plant paleophysiology using known form/function relationships. The fossils examined in this project come from fossil localities ideal for studying various paleophysiological relationships. At the beginning of the Permian Period (~299 Ma), atmospheric CO2 and O2 concentrations were comparable to current day values. By the end of the Permian (~251 Ma), atmospheric CO2 concentration and temperature had risen sharply as the Earth underwent a time of rapid global warming. The distinctive leaf of Glossopteris plants can be found at southern high paleolatitude localities throughout the Permian, allowing for changes in plant physiology to be tracked through a drastically shifting climate. The environmental conditions at the beginning of the Permian are also the same as those that are thought to have favored the evolution of the C4 photosynthetic pathway in the Oligocene (~25 Ma). Using known relationships between leaf anatomy and the C4 pathway, along with stable carbon isotope analysis, the presence or absence of this pathway was tested. The combination of both approaches demonstrated the C3-C4 intermediate photosynthetic pathway was present in Glossopteris during the Late Permian. In the ancient past, plants existed in warm environments at high paleolatitudes where they were subjected to light regimes not experienced by plants today (4 months of continuous light and 4 months of continuous dark). A study of leaf economics of Permian Glossopteris leaves reveals that the plant possessed deciduous leaves and adaptations to continuous light environments. Analysis of Permian and Triassic leaf hydraulic conductance demonstrates that leaf venation density in Glossopteris decreases in response to increasing CO2 but does not change in response to latitude. Glossopteris leaves, which dominated the Permian landscapes of Antarctica, demonstrated a higher leaf venation density than any co-occurring leaves. Such an advantage would benefit leaf hydraulic conductance. In contrast, the Dicroidium leaf type, which dominated the Triassic, had leaf hydraulic values similar to co-occuring leaf morphotypes

Experimental investigation of tangential blowing for control of the strong shock boundary layer interaction on inlet ramps

A 0.165-scale isolated inlet model was tested in the NASA Lewis Research Center 8-ft by 6-ft Supersonic Wind Tunnel. Ramp boundary layer control was provided by tangential blowing from a row of holes in an aft-facing step set into the ramp surface. Testing was performed at Mach numbers from 1.36 to 1.96 using both cold and heated air in the blowing system. Stable inlet flow was achieved at all Mach numbers. Blowing hole geometry was found to be significant at 1.96M. Blowing air temperature was found to have only a small effect on system performance. High blowing levels were required at the most severe test conditions

Validation of the Quasi-Two-Level Operation for a Flying Capacitor Converter in Medium-Voltage Applications

Standard medium-voltage converters are operated at low switching frequencies using bulky passive components. One concept to change this involves the quasi-two-level operation (Q2O) of multilevel converters that use fast-switching semiconductors to minimize the need for passive components. The flying capacitor converter (FCC) uses SiC semiconductors and operates with Q2O to minimize passive components. In this paper, two different quasi-two-level algorithms are analyzed. A medium-voltage prototype was built and low-voltage and medium-voltage measurements were used to validate the concept. A particular focus is on the overvoltage, the dv/dt behavior of the converter, as well as the dynamic behavior

Injury Standards in Section 337 Investigations

In this article the authors analyze the impact of the Trade Act of 1974 on Section 337 cases. They focus on the standards the International Trade Commission (ITC) uses in making its injury determinations in Section 337 cases. The authors also address the limited nature of judicial review over final ITC determinations, and conclude that the enhanced role of the ITC in Section 337 proceedings brought about by the Trade Act of 1974 creates a need for private litigants to build a thorough record on the issue of actual or incipient injury in proceedings before the IT

A Highly Integrated 25-Level Cascaded H-Bridge Active Filter for the Mitigation of High Order Current Harmonics

The increasing share of power electronics in the conversion and distribution of electrical energy represents a novel challenge for energy quality and supply stability. It is to be expected that high-frequency current harmonics will increase significantly with the number of grid-connected power converters. To reduce the associated disadvantages, this paper presents a 25-Level Cascaded H-Bridge Active Filter for mitigating converter-induced current harmonics in the kilohertz range.~Compared to conventional active filters, the proposed use of a voltage-source active filter does not require high control bandwidth, tuning to specific frequencies or measurement and tracking of high frequency currents.~The highly integrated design on printed circuit boards allows a high number of voltage levels and a high power density at small additional effort and costs. A 12 kVA-demonstrator is used to mitigate the switching frequency current harmonics of a grid-connected two-level converter, verifying the effectiveness of the active filter configuration

Cómo Alemania respondió a las inundaciones en Julio del 2021 con la ayuda de tecnologías espaciales?

Actualmente, es muy comun ver en las noticias de Asia, Africa, America como rios se desbordan, destrozan todo a su paso y/o inundan ciudades. En Julio del 2021, eso ocurrió en Alemania, masivas precipitaciones causaron inundaciones en Renania del Norte-Westfalia y Renania-Palatina. En casos de emergencia como este, lo primero que se necesita saber es: ¿cuál es la zona afectada?. Muchas veces las imágenes opticas no pueden ser utilizadas en la detection de inundaciones porque la mayoria de ellas están llenas de nubes. Las imágenes RADAR penetra las nubes y detecta inundaciones pero su grado de precision es de media a baja. Teniendo en cuenta las limitaciones de esas imágenes y la urgencia que el caso amerita, DLR sobrevoló el area y tomó fotografias aéreas de < 15 cm de resolución para ser usadas en la detección de los daños causados por las inundaciones. Para eso se crearon muestras y se las entrenó con el modelo Mask R-CNN. Los resultados fueron enviados inmediatamente a las instituciones federales Alemanas para el Desarrollo de las acciones humanitarias de rescate y de reconstrución correspondientes

A 60 kW Power Hardware-in-the-Loop Test Bench for grid emulation based on a Series Hybrid Cascaded H-Bridge Converter

In this paper the requirements for a Power Hardware-In-the-Loop (PHIL) system for the emulation of grids and grid faults are discussed. Solutions for all parts of the PHIL system – the power electronics, the signal processing system and the software structure – are presented. Subsequently, an analysis of the accuracy, bandwidth and stability of the PHIL testbench is done and the effects of different interface algorithms are shown. Concluding, measurement results of emulated highly dynamic grid faults such as voltage dips and spikes, distorted grids and weak grid situations are shown, which prove the performance of the PHIL system

Injury Standards in Section 337 Investigations

In this article the authors analyze the impact of the Trade Act of 1974 on Section 337 cases. They focus on the standards the International Trade Commission (ITC) uses in making its injury determinations in Section 337 cases. The authors also address the limited nature of judicial review over final ITC determinations, and conclude that the enhanced role of the ITC in Section 337 proceedings brought about by the Trade Act of 1974 creates a need for private litigants to build a thorough record on the issue of actual or incipient injury in proceedings before the IT

Aerodynamic characteristics of a vectored-thrust V/STOL fighter in the transition speed range

A wind-tunnel investigation was conducted with a vectored-thrust V/STOL fighter configuration. The model was equipped with two nacelle-mounted vectored-thrust jet simulators and one lift-jet simulator. The vectored-thrust jet could be tested at two alternate longitudinal positions and three nozzle deflection angles. The vectored-thrust configuration with the rear nozzles showed an increase in lift and a decrease in pitching moment when compared with the forward nozzles. The rear nozzles also improve stall characteristics

Portable Generator to Detect Cracks on Large Steel Structures: An Application of Inductive Thermography

The demand of non-destructive methods to detect cracks caused by fatigue or brittle behavior in large steel structures has increased in the last years. Thermography based on electromagnetic induction is a promising method to detect cracks in weld seams and notches. This paper presents a portable experimental setup, which allows to perform in situ crack detection tests on large steel structures. The success of this configuration is based on the use of a highly efficient switched H-Bridge circuit, which can generate a square-wave output voltage with a fundamental frequency up to 100 kHz. Due to the low losses and the low necessary DC-link voltage, the circuit can be supplied by a lithium-ion battery, which allows a small and light setup. The generated square-wave output voltage supplies an air coil resulting in a high frequent triangle current. The induced electromagnetic field caused by the current signal generates eddy currents in the steel structure. Due to an increased current density of the eddy currents in the crack area, there is a measurable temperature increase near the crack. The resulting temperature field is visualized and recorded with an infrared (IR) camera, which shows in real time the occurrence of cracks