Linear code combinations have been considered for suppressing the ionospheric error. In the L-band, this leads to an increased noise floor. In a combined L- and C-band (5010–5030 MHz) approach, the ...ionosphere can be eliminated and the noise floor reduced at the same time. Furthermore, combinations that involve both code- and carrier-phase measurements are considered. A new L-band code-carrier combination with a wavelength of 3.215 meters and a noise level of 3.92 centimeters is found. The double difference integer ambiguities of this combination can be resolved by extending the system of equations with an ionosphere-free L-/C-band code combination. The probability of wrong fixing is reduced by several orders of magnitude when C-band measurements are included. Carrier smoothing can be used to further reduce the residual variance of the solution. The standard deviation is reduced by a factor 7.7 if C-band measurements are taken into account. These initial findings suggest that the combined use of L- and C-band measurements, as well as the combined code and phase processing are an attractive option for precise positioning.
The refractive index and the extinction coefficient are usually inherent (noncontrollable) material characteristics. Recently, it was reported that the reflectivity of graphene in the mid‐infrared ...spectral range can be modified by an external bias. This report attracted much attention, but the controllable frequency/energy range is too narrow for possible applications. In this work, it is demonstrated that the potential of graphene is not limited to mid‐infrared wavelengths, but spans a much wider range including the visible spectral range. Here, back‐gated bilayer graphene is characterized in air using spectroscopic ellipsometry with a lateral resolution in the micrometer range. By applying a back‐gate voltage, the dielectric function can be modified in a broad spectral range, including the visible spectrum. To explain the change in the dielectric function, a simplified phenomenological approach which assumes that the back‐gating‐induced change in the carrier density of graphene can be described by a modified 2D Drude model is introduced. The trend of increasing values for the dielectric function with increasing sheet charge carrier density is confirmed by theoretical calculations performed in the independent particle picture.
Exfoliated bilayer graphene on a SiO2 substrate is electrically contacted in a back‐gate transistor geometry and investigated by spectroscopic ellipsometry while applying various gate voltages. The applied gate voltage changes the dielectric constant ε1 of graphene substantially from 2.5 to 4.0. Theoretical calculations demonstrate that the values of the dielectric function correlate with the sheet charge carrier density.
INTRODUCTION Günther, Christoph; Dörre, Robert; Pfeifer, Simone
Disentangling Jihad, Political Violence and Media,
10/2023
Book Chapter
Odprti dostop
This edited volume is one of the outputs of the interdisciplinary junior research group ‘Jihadism on the Internet: Images and Videos, their Dissemination and Appropriation’. From 2017 to 2022, the ...project facilitated collaborative work by six researchers with backgrounds in film and media studies, Islamic studies, social and cultural anthropology, and information sciences. The project sought to explore the ways in which groups fighting in the name of jihad communicate their cause through audiovisual media and how people engage with these communicative endeavours. These key questions reflect the field of tension in which our research operated: between our ambitions to
This article explores parallels between the case studies of the Maccabean uprising in the 2 century B.C. and Jihadist battles in contemporary Iraq conducted by the predecessors of the so-called ...Islamic State. In both cases, religio-political actors strive for power through the use of violent acts which they legitimate on the basis of religious duty. In a first step, theoretical considerations of strategies used by certain religio-political actors to delineate themselves from their social environment, consolidate their beliefs and strengthen their own identity, will be discussed. Being regarded as "nonconformist", they try to fight against those in power whom they consider as culturally offensive and politically as well as religiously illegitimate. In the second part of this article we argue that, although one might find the case studies at hand historically too far apart from each other, they are nevertheless comparable in terms of the movements' positions in their socio-political environment, their legitimization as preservers of particular traditions, and their use of violence in order to enforce their claims. Hence, we argue that the movements' descriptions of their battles against the powerful and all the more their confrontations with the 'enemy within' both legitimize their action and motivate their followers. Thus, all people that are regarded by the Maccabees or ISIS as undermining the community of "orthodox" believers and as threatening their "covenant with God" are presented as such to provoke action of a particular kind. Being so strict and even conducting acts of violence against their coreligionists has to be legitimized through the selective use of traditions (mainly the "holy scriptures") as well as through evident changes of traditions if that serves the very purpose. We regard this transformation as a process of cultural dynamics, recognizable in religious practice and the production of media. Zusammenfassung: Dieser Aufsatz beleuchtet Parallelen zwischen den Aufstandsbewegungen der Makkaber des 2. Jh. v. Chr. und der Vorgnger des sog. ,Islamischen Staates (IS) im zeitgenssischen Irak. In beiden Fllen ringen religis-politische Akteure um Macht und weichen dabei nicht vor dem Einsatz von Gewalt zurck, die mit religisen Werten legitimiert wird. Im Sinne einer theoretischen Schrfung des Begriffs religiser Nonkonformismus werden im ersten Teil Strategien diskutiert, die von religis-politischen Akteuren gegenber etablierten Inhabern politischer und religiser Macht benutzt werden. Diese dienen zur Abgrenzung vom sozialen Umfeld sowie zur Konsolidierung der eigenen Bewegung, bestimmter Normen, Werte und Ideen, und sind Artikulation eines wechselseitigen Ablehnungsverhltnisses auf Basis kultureller, religiser und politischer Prmissen, das sich auch in gewaltvollen Auseinandersetzungen Bahn bricht.
With his political cartoons, the Copenhagen-based Sudanese artist Khalid Albaih offers his analyses of the socio-political situation and everyday life in the Middle East and North Africa. Many of his ...cartoons criticise militant movements in the region and the global military and political involvement of local and international actors in conflicts such as that in Syria. In one of his recent cartoons, ‘Scarecrow’ (Figure I.1, overleaf), he responds to US President Donald Trump’s announcement via Twitter of the killing of Abū Bakr al-Baghdādī. Alongside the image, Albaih’s comment on Facebook on 28 October 2019 relates his cartoon to the killing
Different techniques have been developed for determining carrier phase ambiguities, ranging from float approximations to the efficient solution of the integer least square problem by the LAMBDA ...method. The focus so far was on double-differenced measurements. Practical implementations of the LAMBDA method lead to a residual probability of wrong fixing of the order one percent. For safety critical applications, this probability had to be reduced by eight orders of magnitude, which could be achieved by linear multi-frequency code–carrier combinations. Scenarios with single or no differences include biases due to orbit errors, satellite clock offsets, as well as residual code and phase biases. For this case, a linear combination of Galileo E1 and E5 code and carrier phase measurements with a wavelength of 3.285 m and a noise level of a few centimeters is derived. This ionosphere-free combination preserves the orbit and clock errors, and suppresses the E1 code multipath by 12.6 dB. Since integer decorrelation transformations, as used in the LAMBDA method, inflate biases, the number of such transformations must be limited, and applied in a judicious order. With a Galileo type constellation, this leads to a vertical standard deviation of ca. 20 cm, while keeping the probability of wrong fixing extremely low for code biases of 10 cm, and phase biases of 0.1 cycle, combined in a worst case.
The code ionospheric bias, also known as the Differential Code Bias (DCB), is an important correction term for single-frequency receiver. This paper proposes a new method to estimate the biases as ...well as the vertical ionospheric delays using Kriging estimator with a network of receivers. Kriging estimates an unknown variable based on a set of known parameters and a variogram describing the spatial correlation. It is the best estimator in the sense of minimizing the estimation variance. Kriging method is proposed, as it could reconstruct the vertical delays based on a subset to overcome the rank deficiency. A Kalman filter is introduced, and a sub-optimum solution has been obtained based on an iterative Greedy Algorithm. Simulation results have shown cm-level accuracy on the ionospheric bias estimates. The algorithm has also been applied with real GPS data for multiple days, which showed high bias repeatability. The bias estimates have been verified by comparison with published values.
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