Influence of channel base current and varying return stroke speed on the calculated fields of three important return stroke models

Compared here are the calculated fields of the Traveling Current Source (TCS), Modified Transmission Line (MTL), and the Diendorfer-Uman (DU) models with a channel base current assumed in Nucci et al. on the one hand and with the channel base current assumed in Diendorfer and Uman on the other hand. The characteristics of the field wave shapes are shown to be very sensitive to the channel base current, especially the field zero crossing at 100 km for the TCS and DU models, and the magnetic hump after the initial peak at close range for the TCS models. Also, the DU model is theoretically extended to include any arbitrarily varying return stroke speed with height. A brief discussion is presented on the effects of an exponentially decreasing speed with height on the calculated fields for the TCS, MTL, and DU models

Virtual Reality - Chancen und Risiken für die Eventbranche am Beispiel des Corporate Events Certified Logistics Leader der Deutsche Post DHL Group

Die vorliegende Arbeit beschäftigt sich mit der Digitalisierung und den technologischen Innovationen von Virtual Reality und Augmented Reality im Zusammenhang mit der Eventbranche. Mit einer eigens durchgeführten empirischen Untersuchung sollen die Chancen und Risiken von Virtual Reality und Augmented Reality für die Eventbranche ermittelt werden. Der tatsächliche Nutzen dieser Technologien wird sowohl auf der Seite des Eventmanagers als auch auf der Seite des Besuchers analysiert. Die Chancen und Risiken werden am Praxisbeispiel des Corporate Events Certified Logistics Leader der Deutsche Post DHL Group modellhaft dargestellt. Ausgehend von allgemeinen Handlungsempfehlungen für den Einsatz von Virtual Reality und Augmented Reality auf Events werden konkrete Handlungsempfehlungen für das Praxisbeispiel entwickelt. Abschließend werden allgemeine Folgerungen für die Eventbranche in Bezug auf die digitalen Herausforderungen mit Virtual Reality und Augmented Reality formuliert

Innovation industrienaher Dienstleistungen : eine fallstudienbasierte Analyse dynamischer Fähigkeiten und des unterstützenden IT-Einsatzes

The thesis deals with the innovation of industrial services. Starting from the dynamic capability view, the innovation of services is understood as a dynamic capability, which enables companies to sense opportunities and threats in the market, seize them and finally transform their resource base accordingly. The aim of this research is the empirical description of the innovation of industrial services, from which the contextualized characteristics, the roots of dynamic capabilities as well as the role of IT are derived. For this purpose, the dynamic capabilities are investigated in comparative case studies at the level of microfoundations. The focus is particularly on structures, processes, procedures and systems as well as on individuals underlying the dynamic capabilities. This research provides an overview of concrete innovation practices, causal factors for different characteristics of dynamic capabilities, and insights into the role and function of IT in service innovation

A multi-method approach to study the geodynamic evolution of eastern Dronning Maud Land in East Antarctica by integrating geophysical data with surface geology

Planet Earth has not always been as it appears today. Since billions of years, continents have been drifting continually caused by lateral variations of mantle density resulting in convection. Analyzing the movement of lithospheric plates back in eartha s history is essential for the determination of the shape of ancient supercontinents. It further provides paleogeographic information and is vital for biogeographic and climate studies. Whereas the break-up of the former extensive landmass of Gondwana can be reconstructed fairly well by analyzing seafloor-spreading anomalies of the oceanic crust, the amalgamation of Gondwana still needs to be understood in more detail. This is because oceanic crust, that rarely exceeds 180 million years in age, does not provide any direct evidence for the amalgamation of Gondwana in Late Neoproterozoic/Early Palaeozoic times as well as for older supercontinent cycles. East Antarctica, once centerpiece of Gondwana, can be considered a rather stable region as it has not been affected by orogenic processes since the Early Paleozoic except for its Palaeo-Pacific margin. Furthermore, the Antarctic plate is mainly surrounded by mid-ocean ridges and features continental rift systems widely related to the break-up of Gondwana. Therefore, exposed regions that can be found in Sor Rondane, East Antarctica, are well suited for studying the formation and break-up of Gondwana as well as preceding collision and break-up processes. Sor Rondane is situated in eastern Dronning Maud Land and exposes the contact zone of crustal blocks of different origin and architecture. Therefore, it is considered to be a site of at least one suture between East and West Gondwana. This study examines the final amalgamation and break-up history of Gondwana by investigating Sor Rondane and adjacent regions. To answer those questions, a detailed understanding of the crustal architecture is essential. This encompasses the number of involved crustal fragments, the location of their boundaries and their geological evolution. Moreover, this comprises the structural and metamorphic evolution as well as the shallow crustal dynamics of Sor Rondane. Due to the extensive ice-coverage of this region, the study of exposed rocks by various geological methods was combined with regional aerogeophysical investigations. In the austral summers 2010/11 and 2011/12, structural field work and geological sampling were executed by the Federal Institute for Geosciences and Natural Resources (BGR). Additional airborne geophysical surveys were flown in collaboration with the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), between 2010 and 2015. The data set includes ice-penetrating radar, aeromagnetic and aerogravity measurements. These combined geological and geophysical data sets are used to analyse the structure and composition of rock units and enable to map units beneath the ice not accessible to geological methods. For instance, fault systems may correlate with magnetic lineaments gained from aeromagnetic anomaly data. These can be tracked over large distances underneath the ice and thus facilitate interpretations at a larger scale

Determination of Lightning Currents from Far Electromagnetic Fields: Effect of a Strike Object

We discuss in this paper the influence of the presence of an elevated strike object on the peak of the lightning return stroke current determined from remote field measurements. We develop analytical expressions relating the lightning return stroke channel-base current and the far electromagnetic field for different specific cases, namely, (1) ground-initiated return strokes (classical transmission line (TL) model), (2) ground-initiated return strokes including possible reflections at ground level, (3) tall strike objects for which the current's zero-to-peak time is smaller than the travel time along the object, and (4) electrically short strike objects. It is shown that for tall structures, the field enhancement relative to a return stroke initiated at ground level is expressed through a factor equal to ktall = [1 + c / v (1 - 2 ρt)] / (1 - ρt), where v and c are the return stroke front speed and the speed of light in vacuum, respectively, and ρt is the top reflection coefficient. For very short towers and/or very slow return stroke current wavefronts, when the condition tf very much greater than h / c applies, expressions relating the far electromagnetic field and the return stroke current were also derived. For case (2), return strokes initiated at ground level, the field enhancement relative to a return stroke initiated at ground level, case (1), is expressed through a factor equal to kshort = (1 + (c / v) ρch - g) / (1 + ρch - g), where ρch-g represents the reflection coefficient between the lightning channel and the grounding impedance

Scaffolds in vascular regeneration: current status

Neelima Thottappillil, Prabha D Nair Division of Tissue Engineering and Regeneration Technologies, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Kerala, IndiaAbstract: An ideal vascular substitute, especially in <6 mm diameter applications, is a major clinical essentiality in blood vessel replacement surgery. Blood vessels are structurally complex and functionally dynamic tissue, with minimal regeneration potential. These have composite extracellular matrix (ECM) and arrangement. The interplay between ECM components and tissue specific cells gives blood vessels their specialized functional attributes. The core of vascular tissue engineering and regeneration relies on the challenges in creating vascular conduits that match native vessels and adequately regenerate in vivo. Out of numerous vascular regeneration concerns, the relevance of ECM emphasizes much attention toward appropriate choice of scaffold material and further scaffold development strategies. The review is intended to be focused on the various approaches of scaffold materials currently in use in vascular regeneration and current state of the art. Scaffold of choice in vascular tissue engineering ranges from natural to synthetic, decellularized, and even scaffold free approach. The applicability of tubular scaffold for in vivo vascular regeneration is under active investigation. A patent conduit with an ample endothelial luminal layer that can regenerate in vivo remains an unanswered query in the field of small diameter vascular tissue engineering. Besides, scaffolds developed for vascular regeneration, should aim at providing functional substitutes for use in a regenerative approach from the laboratory bench to patient bedside.Keywords: scaffold, vascular regeneration, in viv

Determination of lightning currents from far electromagnetic fields

Expressions relating far electromagnetic fields and return stroke channel base current have been derived in the literature for various lightning return stroke models. The use of such relations permits the estimation of channel base currents of return strokes, testing of the individual models using sets of simultaneous current and field measurements, and also the determination of nondirectly measurable parameters of the models. The authors derive a relation between the far electromagnetic field and the channel base current for the Diendorfer-Uman (DU) and the modified Diendorfer-Uman (MDU) models. Additionally. the current-field relations for all models for which such an analytical relation can be derived are summarized. Finally, a numerical solution technique is proposed to solve the equations relating to the far field and channel base current of the DU and the traveling current source (TCS) model