A Systematic Review of Blockchain Literature in Logistics and Supply Chain Management: Identifying Research Questions and Future Directions

Potential blockchain applications in logistics and supply chain (LSCM) have gained increasing attention within both academia and industry. However, as a field in its infancy, blockchain research often lacks theoretical foundations, and it is not clear which and to what extent organizational theories are used to investigate blockchain technology in the field of LSCM. In response, based upon a systematic literature review, this paper: (a) identifies the most relevant organizational theories used in blockchain literature in the context of LSCM; and (b) examines the content of the identified organizational theories to formulate relevant research questions for investigating blockchain technology in LSCM. Our results show that blockchain literature in LSCM is based around six organizational theories, namely: agency theory, information theory, institutional theory, network theory, the resource-based view and transaction cost analysis. We also present how these theories can be used to examine specific blockchain problems by identifying blockchain-specific research questions that are worthy of investigation

Hydra: practical metadata security for contact discovery, messaging, and voice calls

Protecting communications’ metadata can be as important as protecting their content, i.e., recognizing someone contacting a medical service may already allow to infer sensitive information. There are numerous proposals to implement anonymous communications, yet none provides it in a strong (but feasible) threat model in an efficient way. We propose Hydra, an anonymity system that is able to efficiently provide metadata security for a wide variety of applications. Main idea is to use latency-aware, padded, and onion-encrypted circuits even for connectionless applications. This allows to implement strong metadata security for contact discovery and text-based messages with relatively low latency. Furthermore, circuits can be upgraded to support voice calls, real-time chat sessions, and file transfers - with slightly reduced anonymity in presence of global observers. We evaluate Hydra using an analytical model as well as call simulations. Compared to other systems for text-based messaging, Hydra is able to decrease end-to-end latencies by an order of magnitude without degrading anonymity. Using a dataset generated by performing latency measurements in the Tor network, we further show that Hydra is able to support anonymous voice calls with acceptable quality of service in real scenarios. A first prototype of Hydra is published as open source

Capacity of a bosonic memory channel with Gauss-Markov noise

We address the classical capacity of a quantum bosonic memory channel with additive noise, subject to an input energy constraint. The memory is modeled by correlated noise emerging from a Gauss-Markov process. Under reasonable assumptions, we show that the optimal modulation results from a "quantum water-filling" solution above a certain input energy threshold, similar to the optimal modulation for parallel classical Gaussian channels. We also derive analytically the optimal multimode input state above this threshold, which enables us to compute the capacity of this memory channel in the limit of an infinite number of modes. The method can also be applied to a more general noise environment which is constructed by a stationary Gauss process. The extension of our results to the case of broadband bosonic channels with colored Gaussian noise should also be straightforward.Comment: 11 pages, 4 figures, final corrections mad

Noncompact sigma-models: Large N expansion and thermodynamic limit

Noncompact SO(1,N) sigma-models are studied in terms of their large N expansion in a lattice formulation in dimensions d \geq 2. Explicit results for the spin and current two-point functions as well as for the Binder cumulant are presented to next to leading order on a finite lattice. The dynamically generated gap is negative and serves as a coupling-dependent infrared regulator which vanishes in the limit of infinite lattice size. The cancellation of infrared divergences in invariant correlation functions in this limit is nontrivial and is in d=2 demonstrated by explicit computation for the above quantities. For the Binder cumulant the thermodynamic limit is finite and is given by 2/(N+1) in the order considered. Monte Carlo simulations suggest that the remainder is small or zero. The potential implications for ``criticality'' and ``triviality'' of the theories in the SO(1,N) invariant sector are discussed.Comment: 46 pages, 2 figure

Explaining the creation of the EU Banking Union: the interplay between interests and ideas

How do we explain the outcome of the EU banking union negotiations? Still in 2011, a majority of governments opposed the banking union. They suddenly reversed policies and agreed the creation of a joint supervisor at the Euro Summit in June 2012. This thesis invokes liberal intergovernmentalism to explain the creation of the banking union. Yet, the negotiations pose two major puzzles. First, no clear predictions can be derived from liberal intergovernmentalism for the preferences of arguably the most powerful member state: the German government. Interest groups were divided, public opinion contradictory, and macro-economic preferences unclear. With no clearly most powerful interest, more than one policy was a rational course of action (Folk theorem). To solve this puzzle, the thesis argues that worldviews based on the principles of Ordnungspolitik influenced German policy-makers. In the absence of a unique equilibrium, these worldviews tipped the scale towards a policy of realigning control and liability. The outcome of the interstate negotiations poses the second puzzle for liberal intergovernmentalism. Its power-based theory of interstate bargaining cannot account for German concessions on several issues. Drawing on an account of rhetorical action, the thesis argues that a coalition of Southern European countries used the collectively stated goal to ‘break the vicious circle between banks and sovereigns’ to prove German preferences as unsuitable for achieving this goal. While exposing the weaknesses of the German government’s policy responses, the Southern coalition framed their own preferences for risk-sharing as the most effective solution to the problem. The German government was forced to acquiesce in considerably more risk-sharing than it had initially deemed acceptable. The thesis draws on 84 interviews with negotiators from Germany, France, Italy, Spain, the Netherlands and the EU institutions. The analysis provides several generalisable insights into the role of ideas for domestic preferences and interstate negotiations

¿Cómo convertirse en un artista consagrado?.

Durante el año 2011 realicé una serie de acciones en diferentes museos y centros de arte contemporáneo de España y Francia como parte del proyecto El Artista Consagrado cuyo propósito es cuestionar los mecanismos que confieren valor artístico a los autores y a sus obras. Los museos y ferias de arte, donde he centrado mi atención, se presentan como espacios legitimadores por excelencia al designar y consagrar ciertas obras sobre otras. En otras palabras, tienen cierta autoridad para establecer que es y que no es arte puesto que la presentación de una obra al público implica su legitimación como tal y, en consecuencia, la consagración del autor como artista. Al exponer en la sala de un museo importante o en una feria de renombre un artista obtiene prestigio, un recurso necesario para fortalecer el sentido de pertenencia al ámbito artístico y consolidar una posición frente a los demás. Partiendo de esta idea y en sintonía con la Boite-en-valise (1936/1968) de Marcel Duchamp -que consistía en una maleta con miniaturas de sus obras que el autor podía transportar de un lugar a otro como un museo portátil- llevo mis fotos a cuestas, impresas sobre camisetas, para exponerlas en prestigiosos museos y ferias de arte contemporáneo, asentando cada exposición en mi curriculum y convertirme en un artista consagrado. En esta ponencia expondré los fundamentos teóricos que sustentan el proyecto y las distintas fases de desarrollo

Prediction and Conversion of Corrosion Related UEP-Signatures of Naval Vessels

Wasserfahrzeuge können sich durch elektrische Felder, magnetische Felder und Schallwellen ungewollt ihrer Umgebung mitteilen, was bei der U-Jagd und bei modernen Seeminen intensiv zur Erkennung feindlicher Kräfte ausgenutzt wird. Für militärische Wasserfahrzeuge, insbesondere U-Boote und Minenjagdboote, wird daher als Gegenmaßnahme ein enormer Aufwand zur Reduktion der zuvor genannten Größen, namentlich der (Teil-)Signaturen, betrieben. Diese lassen sich jedoch niemals vollständig eliminieren und weisen teilweise komplexe Abhängigkeiten von den Umgebungsbedingungen auf. Zwecks Risikoabschätzung während kritischer Einsätze ist es deshalb von großem Interesse, die gegenwärtige (Gesamt-)Signatur des eigenen Wasserfahrzeugs kurzfristig ermitteln zu können. Hier setzt die Dissertation an, indem sie verschiedene Konzepte zur Vorhersage und Umrechnung korrosionsbedingter UEP-Signaturen (Underwater Electric Potential) von Wasserfahrzeugen im Kontext von Mine Warfare (MIW), Anti-submarine Warfare (ASW) sowie Mine Countermeasure (MCM) und Integrated Ship Signature Management (ISSM) vorstellt. Zunächst wird anhand von Vergleichen zwischen berechneten, simulierten und gemessenen Werten demonstriert, dass UEP-Signaturen unter Verwendung nichtlinearer Polarisationskennlinien numerisch simuliert werden können. Im nächsten Abschnitt der Arbeit wird ein inverser Modellierungsansatz namens Multipoladaption auf Basis evolutionärer Algorithmen dazu verwendet, gemessene elektrische Signaturen eines Dipols zu adaptieren. Dabei wird differenziert dargelegt, in welchen Fällen die Multipoladaption in der Lage ist, die Quellenverteilungen und/oder die UEP-Signatur korrekt wiederzugeben. Außerdem wird eine Definition zur Abgrenzung zwischen Nah- und Fernfeld von UEP-Signaturen hergeleitet. Es folgt ein Abschnitt, der sich in Hinblick auf ISSM mit diversen Ansätzen zur Echtzeit-Überwachung der eigenen UEP-Signatur mittels Wellenstrom-Messungen, Schleppkörper-Messungen und analytischer Berechnungen beschäftigt. Durch umfangreiche numerische Simulationen mit systematisch variierten Umgebungsbedingungen wird die Leistungsfähigkeit der verschiedenen Ansätze bzw. Ansatz-Kombinationen untersucht und verglichen. Dabei kann gezeigt werden, dass sich der innovative Ansatz der Schleppkörper-Umrechnung hervorragend zur kurzfristigen Bestimmung der gegenwärtigen UEP-Signatur eignet. Im letzten Abschnitt der Dissertation werden die prinzipiellen Eigenschaften der elektrischen Signatur oberhalb der Wasserlinie (Above water Electric Potential, AEP) untersucht, wobei eine erstaunlich einfache Umrechnungsvorschrift zwischen UEP und AEP hergeleitet werden kann. Die Dissertation wurde im Rahmen zweier Forschungsprojekte erstellt, die von der Deutschen Marine bei der Universität Duisburg-Essen (Fachgebiet ATE) in Auftrag gegeben wurden. Sie stellt eine inhaltliche Erweiterung und Konkretisierung der in den Projekten ausgearbeiteten Forschungsergebnisse dar.Naval vessels unintentionally reveal themselves by electric fields, magnetic fields and sound, which is exploited in Anti-submarine Warfare (ASW) and by modern naval influence mines to detect enemy forces. For submarines and mine hunting vessels the aforementioned quantities, called signatures, are therefore reduced elaborately. However the signatures can never be eliminated completely and are highly dependent on the environmental conditions. To conduct risk assessment during critical operations it is therefore of great interest to evaluate the own contemporary signature in real-time. At this point the dissertation comes into play, by introducing different concepts for prediction and conversion of corrosion related UEP signatures (Underwater Electric Potential) in the context of Mine Warfare (MIW), ASW as well as Mine Countermeasure (MCM) and Integrated Ship Signature Management (ISSM). By comparing calculated, simulated and measured values it is first demonstrated, that UEP signatures can be numerically simulated by the use of non-linear polarization curves. In the next chapter an inverse modeling approach called multipole adaption Multipoladaption, based on evolutionary algorithms, is used to adapt measured electric signatures of a dipole. Thereby it is demonstrated in detail under which circumstances the multipole adaption is capable of determining the correct source distribution and/or UEP signature. In the same framework a quantitative relation has been derived for distinguishing between UEP near-field and far-field. With regard to ISSM the following chapter introduces different approaches for real-time assessment of the own UEP signature by shaft currents, measurements with a towfish and analytical calculations. Extensive numerical simulations with systematically variated environmental conditions are carried out to analyze and compare the performance. Thereby it is shown, that the innovative towfish approach is very well suited for obtaining a short-term estimation of the apparent UEP signature. The last chapter of the thesis describes the properties of the electric signature above the waterline (Above water Electric Potential, AEP) and gives a surprisingly simple conversion prescription between UEP and AEP. The dissertation was created in the context of two research projects commissioned by the German navy and conducted by the laboratory for General and Theoretical Electrical Engineering (ATE) at the the University of Duisburg-Essen. It extends and complements the research results obtained during the projects