A Large Along-Track Baseline Approach for Ground Moving Target Indication Using TanDEM-X

In the paper a new method for ground moving target indication (GMTI) using two satellites (i.e. the TerraSAR-X and the TanDEM-X satellite) together is presented. The along-track baseline between the satellites is chosen to be in the order of several kilometres, so that each satellite observes the same moving vehicles at different times in the order of one to several seconds. The proposed method allows the estimation of the ground velocity of the moving targets as well as the estimation of the broadside positions without the need of complex bistatic processing techniques

Quantitative analysis of anti-inflammatory lignan derivatives in Ratanhiae radix and its tincture by HPLC–PDA and HPLC–MS

AbstractRoot preparations of Krameria lappacea (Dombey) Burdet et Simpson are traditionally used against oropharyngeal inflammation. Besides antimicrobial and astringent procyanidines, lignan derivatives, including ratanhiaphenol I, II, III and (+)-conocarpan, contribute to the activity of Ratanhiae radix, exerting a significant topical anti-inflammatory activity in vivo, and in vitro by inhibiting NF-κB and the formation of inflammatory prostaglandins and leukotrienes. Besides gravimetrical analysis of the ratanhiaphenols I, II and III, the content of these compounds in the herbal drug has never been determined. The developed HPLC method enables the quantification of twelve active lignan derivatives in the roots, and is also suitable for the determination of the constituents in Tinctura Ratanhiae. Separation was achieved on a phenyl-hexyl column material using a solvent gradient consisting of 0.02% aqueous TFA and a mixture of acetonitrile/methanol (75:25, v/v). Sensitivity, accuracy (recovery rates were between 95% and 105.6%), repeatability (RSD≤4.6%), and precision (intra-day precision≤4.8%; inter-day precision≤3.4%) of the method were determined. HPLC–MS experiments in positive and negative electrospray ionization mode confirmed identity and peak purity of analytes. The analysis of several root and tincture samples revealed that (+)-conocarpan and ratanhiaphenol II dominated with contents of 0.49–0.71% and 0.51–0.53% in the roots and 0.66–0.68mg/ml and 0.70–0.71mg/ml in the commercial tinctures, respectively

Novel post-Doppler STAP with a priori knowledge information for traffic monitoring applications

The road traffic has worsened over time in most cities, and the methods employed for monitoring and counting the vehicles on the roads (e.g., cameras, induction loops, or even people manually counting) are expensive and limited in spatial coverage. Synthetic aperture radars (SAR) provide an effective solution for this problem due to the wide-area coverage and the independence from daylight and weather conditions. Special attention is given in case of large scale events or catastrophes, when mobile internet is unavailable and phone communication is impossible. In this particular scenario, the traffic monitoring with real-time information ensures the safety of the road users and can even save lives. For that reason, this paper presents a novel a priori knowledge-based algorithm for traffic monitoring, where the powerful post-Doppler space-time adaptive processing (PD STAP) is combined with a road network obtained from the freely available OpenStreetMap (OSM) database. The incorporation of a known road network into the processing chain presents great potential for real-time processing, since only the acquired data related to the roads need to be processed. As a result, decreased processing hardware complexity and low costs compared to state-of-the-art systems can be achieved. In addition, it is a promising solution for detecting effectively the road vehicles and estimating their positions, velocities and moving directions with high accuracy. The PD STAP is well-known for its very good clutter suppression, its sensitivity also to low vehicle velocities, and its accurate target position estimation capabilities. The road information is applied after the PD STAP, where the OSM database fused with a digital elevation model (DEM) is applied in order to recognize and to reject false detections, and moreover, to reposition the vehicles detected in the vicinity of the roads. In other words, the distance between the estimated position of the target and its closest road point is measured and compared to a relocation threshold for deciding whether the target corresponds to a true road vehicle or to a false detection. If the first condition is fulfilled, the target is repositioned to its closest road point; otherwise it is discarded. The relocation threshold is computed adaptively for each detection by using an appropriate performance model. The proposed algorithm was tested using real 4-channel aperture switching data acquired by DLR’s airborne system F-SAR. In the radar data takes examined so far, the PD STAP detected vehicles as slow as 7 km/h, with an overall position estimation accuracy better than 10 m. Besides, the estimated velocities of the vehicles were in very good agreement with the differential GPS reference data. To sum up, the experimental results revealed a powerful algorithm that detects even slow vehicles and discards most of the false detections, being suitable for many traffic monitoring applications. We will not limit our further investigations to the data takes whose results are shown in this paper. We have a large pool of multi-channel F-SAR data takes containing real highway traffic scenarios with dozens or even hundreds of vehicles

Digital Beamforming and Traffic Monitoring Using the new FSAR System of DLR

In November 2006 the first X-band test flight of DLR’s new FSAR system has been performed successfully and in February 2007 the first flight campaign has been conducted for acquiring experimental multi-channel data of controlled ground moving targets. In the paper the performed experiments and the used setup of the FSAR X-band section are described and preliminary results in the field of ground moving target indication and digital beamforming are presented

Multi-Channel Calibration for Airborne PostDoppler Space-Time Adaptive Processing

This paper presents a fast and efficient multichannel calibration algorithm for along-track systems, which in particular is evaluated for the post-Doppler space-time adaptive processing (PD STAP) technique. The calibration algorithm corrects the phase and magnitude offsets among the receiving channels, estimates and compensates the Doppler centroid variation caused by atmospheric turbulences by using the attitude angles of the antenna array. Important parameters and offsets are estimated directly from the radar rangecompressed data. The proposed algorithm is compared with the state-of-the-art Digital Channel Balancing technique based on real multi-channel X-band data acquired by the DLR’s airborne system F-SAR. The experimental results are shown and discussed in the frame of traffic monitoring applications

PDE models of field-effect sensors

Die Verwendung von Nanodrähten als biologisch sensitive Feldeffekttransistoren und somit als markierungsfreie Sensoren birgt eine Reihe von vielversprechenden Anwendungen wie zum Beispiel die Detektion von DNA oder, wie kürzlich in Blut nachgewiesen, von Krankheitsmarkern. Doch trotz des enormen experimentellen Entwicklungsfortschrittes und dem Versuch diese Technologie massenproduktionstauglich zu machen, fehlt ein umfassendes quantitatives Verständins, welches nur durch mathematische Modellierung und durch Simulationen erreicht werden kann. Das mathematische Modell muss dabei zweierlei Dinge berücksichtigen: Den Aufbau solcher Sensoren und das Detektionsprinzip. Der Aufbau besteht grundlegend aus einer nichtleitenden Schicht auf der der halbleitende Nanodraht aufgelegt ist. Der Nanodraht selbst ist wiederum mit einer nichtleitenden Schicht überzogen und der ganze Sensor ist einer wässrigen Lösung ausgesetzt, welche die zu detektierenden Moleküle enthält. Um alle geometrischen Eigenheiten des Sensors zu berücksichtigen muss das Modellierungsgebiet als dreidimensional angenommen werden. Die vorkommenden Materialien können dann mit einem System von partiellen Differentialgleichungen beschrieben werden. Dieses System ist auf der Poisson Gleichung aufgebaut und beinhaltet die Poisson-Boltzmann Gleichung und das Drift-Diffusion-Poisson System. Mit diesen Gleichungen können das elektrostatische Potential und die Ladungsträgerkonzentrationen selbstkonsistent berechnet und somit der Strom durch den Sensor bestimmt werden. Das Detektionsprinzip und somit auch die Sensitivität des Sensors ist von dem, durch den Wechsel der Ladung in einer Grenzschicht, welcher durch die Bindung der zu detektierenden Moleküle an die an der Oberfläche befindlichen Moleküle zu Stande kommt, induzierten, Feldeffekt abhängig. Da diese Moleküle um einige Größenordnungen kleiner sind als die Gesamtgröße des Sensors würde eine herkömmliche Methode zur Lösung des Gleichungssystems, zum Beispiel die finite Volumen Methode, eine sehr feine Auflösung brauchen. Daher ist eine Multiskalenmethode angeraten welche nicht nur das Auflösungsproblem löst sondern gleichzeitig auch den Vorteil mit sich bringt, dass verschiedene Methoden zur Berechnung der Gegenionen in der Grenzschicht verwendet werden können. Nichtsdestotrotz ist das zu lösende lineare System, welches aus der finiten Volumen Methode resultiert, nach wie vor groß. Daher wurde eine Parallelisierungsmethode entwickelt. Parallelisierungsmethoden die auf dem FETI Algorithmus aufbauen haben den Vorteil, dass das Schnittstellenproblem durch Lagrange Multiplikatoren gelöst wird und somit die Sprungbedingungen der Multiskalenmethode in einer intuitiven Art implementiert werden können. Abschließend kann dieses Model dazu benutzt werden, die Sensitivität in Abhängigkeit von geometrischen und physischen Eigenschaften zu optimieren.Nanowires used as biologically sensitive field-effect transistors (biofets) are promising labelfree sensing devices with a wide range of applications, e.g., the detection of DNA or disease markers, recently even in whole blood. Despite the experimental progress in recent years and the push towards mass fabrication, quantitative understanding of the devices has been missing and hence mathematical modeling and simulation are crucial for physical understanding and optimal sensing. Therefore, a mathematical model has to include two major parts, the structure of such devices and the sensing mechanism. The structure is based on a dielectric bulk layer carrying the semiconducting nanowire. The nanowire itself is covered by a second, thin dielectric layer. The whole dielectric surface is functionalized with probe molecules and is exposed to an aqueous solution containing the target molecules. To capture all geometry properties the model domain needs to be in 3d. The different materials are simulated by a system of partial differential equations based on the Poisson equation consisting of the Poisson-Boltzmann equation and the drift-diffusion-Poisson system. A solution of these equations exists and is locally unique around thermal equilibrium. The electrostatic potential and the charge densities are self-consistently computed and hence the current through the device is obtained. The sensing mechanism and hence the sensitivity of the sensor is based on a field effect induced by a change of the boundary layer charge due to binding of target molecules to probe molecules. Since these molecules are some orders of magnitude smaller than the structure of the nanowire, a usual approach, such as the finite volume method, would need a very fine resolution. Hence a multiscale method is recommended which has the advantage that not only the resolution problem is avoided, it also makes it possible to use various methods for the computation of the concentration of counter ions in the boundary layer. Nonetheless, the resulting linear problem, after discretization with the finite volume scheme, is still large and hence a parallelization technique has been developed. Parallelization techniques based on the FETI method have the advantage that the interface problem is solved by Lagrange multipliers and hence the implementation of the jump conditions from the multiscale method is straightforward. In the end, this model can be used to determine the optimal point of sensitivity regarding the geometry as well as the physical properties of such devices

A best practice for gamification in large companies: An extensive study focusing inter-generational acceptance

Gamification is increasingly successful in the field of education and health. However, beyond call-centers and applications in human resources, its utilization within companies remains limited. In this paper, we examine the acceptance of gamification in a large company (with over 17,000 employees) across three generations, namely X, Y, and Z. Furthermore, we investigate which gamification elements are suited for business contexts, such as the dissemination of company principles and facts, or the organization of work tasks. To this end, we conducted focus group discussions, developed the prototype of a gamified company app, and performed a large-scale evaluation with 367 company employees. The results reveal statistically significant intergenerational disparities in the acceptance of gamification: younger employees, especially those belonging to Generation Z, enjoy gamification more than older employees and are most likely to engage with a gamified app in the workplace. The results further show a nuanced range of preferences regarding gamification elements: avatars are popular among all generations, badges are predominantly appreciated by Generations Z and Y, while leaderboards are solely liked by Generation Z. Drawing upon these insights, we provide recommendations for future gamification projects within business contexts. We hope that the results of our study regarding the preferences of the gamification elements and understanding generational differences in acceptance and usage of gamification will help to create more engaging and effective apps, especially within the corporate landscape

Impact of Road Vehicle Accelerations on SAR-GMTI Motion Parameter Estimation

In recent years many powerful techniques and algorithms have been developed to detect moving targets and estimate their motion parameters from single- or multi-channel SAR data. In case of single- and two-channel systems, most of the developed algorithms rely on analysis of the Doppler history. Nowadays it is known, that even small unconsidered across-track accelerations can bias the along-track velocity estimation. Since we want to monitor real and more complex traffic scenarios with a future traffic monitoring system like TRAMRAD, we must know which target accelerations we have to handle in reality. For this reason a common passenger car was equipped with an inertial measurement system and differential GPS to measure accelerations in all three dimensions during rush-hour traffic. In this paper the results of the acceleration measurements are presented and discussed. The standard deviations of the measured accelerations are in the order of 0.5 m/s2 for accelerations in driving direction and 0.6 m/s2 for radial accelerations. A theoretical analysis (which is verified by detailed simulations) of the Doppler slope shows also that at such high across-track accelerations a reliable estimation of the along-track velocity by means of a Doppler slope analysis without further information is unemployable in practice. Also oscillations of the car body along the vertical axis are investigated in this paper. From the field of vehicle dynamics it is known that the eigen frequencies of the car body are in the range from 0.7 to 2.0 Hz. Deflections in the order of one wavelength (X-band) or higher are possible at such frequencies. The simulation results for spaceborne SAR systems with integration times in the order of one second show that the shape and azimuth shift of the impulse response depend beside the oscillation frequency and the deflection also on the initial phase of the oscillation. However, at practical applications the main part of the energy could also be reflected by double bounce from the road surface. Thus, further investigations in the topic of vehicle oscillations by using real radar data are necessary. Finally, some basic ideas are presented which enable a reliable separation between along-track velocity and across-track acceleration. For example, the easiest way to separate both just mentioned motion parameters is the use of a road database, from which the information about the motion direction of the assigned vehicle can be extracted. Hence, the accuracy of along-track velocity estimation is mainly given by the accuracy of the estimated across-track velocity and the angle of the road section in relation to the flight path of the SAR platform

Bistatic Experiment Using TerraSAR-X and DLR’s new F-SAR System

A bistatic X-band experiment was successfully performed early November 2007. TerraSAR-X was used as transmitter and DLR’s new airborne radar system F-SAR, which was programmed to acquire data in a quasi-continuous mode to avoid echo window synchronization issues, was used as bistatic receiver. Precise phase and time referencing between both systems, which is essential for obtaining high resolution SAR images, was derived during the bistatic processing. Hardware setup and performance analyses of the bistatic configuration are pre-sented together with first processing results that verify the predicted synchronization and imaging performance

Does experience matter? Assessing user motivations to accept a vehicle-to-grid charging tariff

Vehicle-to-grid (V2G) could be a cornerstone to ensure the efficient integration of a large number of electric vehicles (EVs) and the resulting electricity demand into the energy system. However, successful V2G adoption requires direct interaction with the EV user. To explore user preferences and requirements in the context of a V2G charging tariff, we conducted a survey (N = 1196). We assess users’ minimum range requirements and willingness to pay for a V2G charging tariff and relate them to users’ experience with EVs. By building a mediation model, we evaluate the importance of three charging strategies to guide users’ minimum range requirements and expected monetary savings. The results reveal EV owners’ preference for a climate-neutral charging strategy, leading to a higher readiness to accept lower minimum ranges and lower monetary savings. These results are especially important to aggregators, aiming to design profitable business models, while accounting for user requirements and preferences