Data-Driven Models for Traffic Flow at Junctions

The simulation of traffic flow on networks requires knowledge on the behavior across traffic intersections. For macroscopic models based on hyperbolic conservation laws there exist nowadays many ad-hoc models describing this behavior. Based on real-world car trajectory data we propose a new class of data-driven models with the requirements of being consistent to networked hyperbolic traffic flow models. To this end the new models combine artificial neural networks with a parametrization of the solution space to the half-Riemann problem at the junction. A method for deriving density and flux corresponding to the traffic close to the junction for data-driven models is presented. The models parameter are fitted to obtain suitable boundary conditions for macroscopic first and second-order traffic flow models. The prediction of various models are compared considering also existing coupling rules at the junction. Numerical results imposing the data-fitted coupling models on a traffic network are presented exhibiting accurate predictions of the new models.Comment: 27 pages, 9 figures, 6 table

Röntgenographische und spektroskopische Charakterisierung der lichtgetriebenen Ionenpumpe Halorhodopsin aus Halobacterium salinarum

In der vorliegenden Arbeit wird die Isolierung, die Kristallisation und die Röntgenstrukturanalyse der lichtgetriebenen Anionenpumpe Halorhodopsin (HR) aus Halobacterium salinarum vorgestellt. Aufbauend auf die 3-dimensionale Struktur von HR und von Bakteriorhodopsin (BR) wird ein Modell des Ionentransportes (Protonen und Halidionen) in archaealen Ionenpumpen entwickelt, welches die unterschiedliche Spezifität und Vektorialität dieser Retinalproteine mit Rücksicht auf die bekannten biochemischen Daten erklärt. Eine quantitative Analyse der Chromophorenkonformation im HR-Grundzustand (Resonanz-Raman-Spektroskopie) sowie lichtinduzierter Veränderungen (UV/VIS- und FTIR-Spektroskopie) vervollständigt die Beschreibung der HR-Kristalle und ermöglich die Durchführung weitergehender Strukturanalysen zum Anionentransport in HR

A data-driven microscopic on-ramp model based on macroscopic network flows

While macroscopic traffic flow models consider traffic as a fluid, microscopic traffic flow models describe the dynamics of individual vehicles. Capturing macroscopic traffic phenomena remains a challenge for microscopic models, especially in complex road sections such as on-ramps. In this paper, we propose a microscopic model for on-ramps derived from a macroscopic network flow model calibrated to real traffic data. The microscopic flow-based model requires additional assumptions regarding the acceleration and the merging behavior on the on-ramp to maintain consistency with the mean speeds, traffic flow and density predicted by the macroscopic model. To evaluate the model's performance, we conduct traffic simulations assessing speeds, accelerations, lane change positions, and risky behavior. Our results show that, although the proposed model may not fully capture all traffic phenomena of on-ramps accurately, it performs better than the Intelligent Driver Model (IDM) in most evaluated aspects. While the IDM is almost completely free of conflicts, the proposed model evokes a realistic amount and severity of conflicts and can therefore be used for safety analysis.Comment: 15 pages, 5 figure

Political Reality: Attack Ads are Here to Stay

The primary research questions of this study center on two largely overlooked areas in negative political advertising: (1) Would the sponsor of the attack ad message be better off with a positive message? (2) When one is targeted by an attack ad, how should the attacked candidate respond? M-Turk subjects (n = 1,380) were used to conduct a multi-stage experimental design to capture the dynamic aspects of how subjects react to the use of attack ads in a hypothetical political campaign. In general, subjects did not respond favorably to attack ads, as these negative political messages caused damage to the image of both the attacker and the attacked. However, it was found that attack ads did cause greater harm to the evaluations of the attacked candidate than to the attacker. Positive ads offered in response to an attack ad helped the attacked candidate recover, whereas negative counter ads, when executed in response to an attack ad, inflicted greater damage to the attacked than the attacker. Suggestions for future research are offered in this highly relevant area of political campaigning

Increased Light Extraction of Thin-Film Flip-Chip UVB LEDs by Surface Texturing

Ultraviolet light-emitting diodes (LEDs) suffer from a low wall-plug efficiency, which is to a large extent limited by the poor light extraction efficiency (LEE). A thin-film flip-chip (TFFC) design with a roughened N-polar AlGaN surface can substantially improve this. We here demonstrate an enabling technology to realize TFFC LEDs emitting in the UVB range (280-320 nm), which includes standard LED processing in combination with electrochemical etching to remove the substrate. The integration of the electrochemical etching is achieved by epitaxial sacrificial and etch block layers in combination with encapsulation of the LED. The LEE was enhanced by around 25% when the N-polar AlGaN side of the TFFC LEDs was chemically roughened, reaching an external quantum efficiency of 2.25%. By further optimizing the surface structure, our ray-tracing simulations predict a higher LEE from the TFFC LEDs than flip-chip LEDs and a resulting higher wall-plug efficiency

Effect of electron blocking layer doping and composition on the performance of 310 nm light emitting diodes

The effects of composition and p-doping profile of the AlGaN:Mg electron blocking layer (EBL) in 310 nm ultraviolet B (UV-B) light emitting diodes (LEDs) have been investigated. The carrier injection and internal quantum efficiency of the LEDs were simulated and compared to electroluminescence measurements. The light output power depends strongly on the temporal biscyclopentadienylmagnesium (Cp 2 Mg) carrier gas flow profile during growth as well as on the aluminum profile of the AlGaN:Mg EBL. The highest emission power has been found for an EBL with the highest Cp 2 Mg carrier gas flow and a gradually decreasing aluminum content in direction to the p-side of the LED. This effect is attributed to an improved carrier injection and confinement that prevents electron leakage into the p-doped region of the LED with a simultaneously enhanced carrier injection into the active region