Academic literature on the topic 'Two-Line-Element sets'

This chapter deals with lamplighter groups. Imagine an infinite main street lined with evenly spaced lamp posts in a rural town. In mathematical terms, the infinite main street may be envisioned as a copy of the integer points on the number line, with a bulb placed at every integer. An element of the lamplighter group consists of two parts: a finite set of integers, corresponding to the bulbs illuminated by the lamplighter, and a single integer denoting the position of the lamplighter. The chapter first considers the generators and relators of a lamplighter group before computing the word lengths of elements of the group. It also describes the dead end elements of the lamplighter group and some geometric properties of its Cayley graph. The discussion includes exercises and research projects.

Multimedia applications are rapidly spread at an everincreasing rate, introducing a number of challenging problems at the hands of the research community. The most significant and influential problem among them is the effective access to stored data. In spite of the popularity of keyword-based search technique in alphanumeric databases, it is inadequate for use with multimedia data due to their unstructured nature. On the other hand, a number of video content and contextbased access techniques have been developed (Deb, 2005). The basic idea of content-based retrieval is to access multimedia data by their contents, for example, using one of the visual content features. While context-based techniques try to improve the retrieval performance by using associated contextual information, other than those derived from the media content (Hori & Aizawa, 2003). Most of the proposed video indexing and retrieval prototypes have two major phases, the database population and the retrieval phase. In the former one, the video stream is partitioned into its constituent shots in a process known as shot boundary detection (Farag & Abdel-Wahab, 2001, 2002b). This step is followed by a process of selecting representative frames to summarize video shots (Farag & Abdel-Wahab, 2002a). Then, a number of low-level features (color, texture, object motion, etc.) are extracted in order to use them as indices to shots. The database population phase is performed as an off-line activity and it outputs a set of metadata with each element representing one of the clips in the video archive. In the retrieval phase, a query is presented to the system that in turns performs similarity matching operations and returns similar data back to the user. The basic objective of an automated video retrieval system (described above) is to provide the user with easy-to-use and effective mechanisms to access the required information. For that reason, the success of a content-based video access system is mainly measured by the effectiveness of its retrieval phase. The general query model adopted by almost all multimedia retrieval systems is the QBE (query by example; Marchionini, 2006). In this model, the user submits a query in the form of an image or a video clip (in case of a video retrieval system) and asks the system to retrieve similar data. QBE is considered to be a promising technique since it provides the user with an intuitive way of query presentation. In addition, the form of expressing a query condition is close to that of the data to be evaluated. Upon the reception of the submitted query, the retrieval stage analyzes it to extract a set of features then performs the task of similarity matching. In the latter task, the query-extracted features are compared with the features stored into the metadata; then matches are sorted and displayed back to the user based on how close a hit is to the input query. A central issue here is the assessment of video data similarity. Appropriately answering the following questions has a crucial impact on the effectiveness and applicability of the retrieval system. How are the similarity matching operations performed and based on what criteria? Do the employed similarity matching models reflect the human perception of multimedia similarity? The main focus of this article is to shed the light on possible answers to the above questions.

Interest in vertical-axis wind turbines (VAWTs) is experiencing a renaissance after most major research projects came to a standstill in the mid 90’s, in favour of conventional horizontal-axis turbines (HAWTs). Nowadays, the inherent advantages of the VAWT concept, especially in the Darrieus configuration, may outweigh their disadvantages in specific applications, like the urban context or floating platforms. To enable these concepts further, efficient, accurate, and robust aerodynamic prediction tools and design guidelines are needed for VAWTs, for which low-order simulation methods have not

Abstract Research to develop new technologies for increasing the safety of passengers and crew in rail equipment is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. Two crash energy management (CEM) components that can be integrated into the end structure of a locomotive have been developed: a push-back coupler (PBC) and a deformable anti-climber (DAC). These components are designed to inhibit override in the event of a collision. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a l

Abstract This paper presents a new computational method for quadrilateral meshing of a thin, or narrow, two-dimensional domain. An output mesh of our method is well-shaped and either single-layered, multi-layered, or partially multi-layered. Element sizes can be uniform or graded. A high quality, layered quadrilateral mesh is often required for finite element analyses of a narrow two-dimensional domain with a large deformation such as the analysis of rubber deformation or sheet metal forming. Our method consists of two steps: (1) extraction of the skeleton of a given domain by the discrete cho

In the two position theory of finite kinematics, we are concerned with not only the displacement of a rigid body, but also with the displacement of a certain element of the body. This paper deals with the displacement of a line and reveals the regulus that characterizes such a displacement. Residing on a special hyperbolic paraboloid, the regulus is obtained by the intersection of three linear line complexes corresponding to a specific set of basis screws of a 3-system. The degeneration of the regulus when two positions of a line intersect is also discussed. In this paper, the regulus of inter

Potash minerals are a source of potassium, which is used for the manufacture of gunpowder and fertilizer. Commercial potash mineralization is often discovered when petroleum wells are drilled through evaporite sequences and the Gamma Ray log “goes off scale”. This is because potassium is one of the naturally occurring radioactive elements, emitting gamma rays from the 40K isotope, in its decay to 40Ar. However, not all potash minerals may be commercial sources of potassium via underground mechanical or solution mining techniques and Potassium is not the only radioactive element. For example, t