Recognition of singularities of rectifying worldsheets generated by framed worldlines

2021 ◽  
Vol 36 (23) ◽  
pp. 2150172
Author(s):  
Hongyu Guo ◽  
Siyao Liu ◽  
Zhigang Wang ◽  
Haiming Liu

In this paper, we consider the local topological structures of a class of new worldsheets, call it the rectifying worldsheets, which are generated by a class of singular worldlines. Using the classification approaches of the finite type on the tangent developables and defining the extended striction curve, this paper gives the detailed classification of the rectifying worldsheets of singular worldlines. It is demonstrated that the rectifying worldsheets of singular worldlines will appear not only in cuspidal edge and swallowtail, but cuspidal beaks under suitable conditions. Especially the singularities of rectifying worldsheets of singular worldlines are associated with curvature functions such that the singularities can be characterized by these functions. Two examples are provided to put the theoretical results into the practice of computation and classification.

1993 ◽  
Vol 17 (1) ◽  
pp. 287-298 ◽  
Author(s):  
Bang-yen Chen ◽  
Susumu Ishikawa

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
George Iakovakis ◽  
Constantinos-Giovanni Xarhoulacos ◽  
Konstantinos Giovas ◽  
Dimitris Gritzalis

The COVID-19 outbreak has forced businesses to shift to an unprecedented “work from home” company environment. While this provides advantages for employees and businesses, it also leads to a multitude of shortcomings, most prevalent of which is the emergence of additional security risks. Previous to the outbreak, company computer networks were mainly confined within its facilities. The pandemic has now caused this network to “spread thin,” as the majority of employees work remotely. This has opened up a variety of new vulnerabilities, as workers’ cyber protection is not the same at home as it is in office. Although the effects of the virus are now subsiding, working remotely has embedded itself as the new normal. Thus, it is imperative for company management to take the necessary steps to ensure business continuity and be prepared to deal with an increased number of cyber threats. In our research, we provide a detailed classification for a group of tools which will facilitate risk mitigation and prevention. We also provide a selection of automated tools such as vulnerability scanners, monitoring and logging tools, and antivirus software. We outline each tool using tables, to show useful information such as advantages, disadvantages, scalability, cost, and other characteristics. Additionally, we implement decision trees for each category of tools, in an attempt to assist in navigating the large amount of information presented in this paper. Our objective is to provide a multifaceted taxonomy and analysis of mitigation tools, which will support companies in their endeavor to protect their computer networks. Our contribution can also help companies to have some type of cyber threat intelligence so as to put themselves one step ahead of cyber criminals.


Author(s):  
I.O. Mikulionok

The basic data on the volume of production of pneumatic tires in the world and in Ukraine are presented. The need to improve the ways of handling pneumatic tires that have lost their con-sumer properties (worn out tires as a result of their intended use and tires rejected as a result of passing quality control during their manufacture) is shown as one of the most dangerous for the environment and promising in terms of using their properties. A detailed classification of methods for handling worn out and defective tires is proposed and a critical analysis of each of them is given. Particular attention is paid to the methods of utilization of tires, in particular, recycling, which makes it possible to efficiently use the secondary raw materials obtained from tires directly for their intended purpose. The features of physical, physicochemical and chemical processing methods, in particular combustion, gasification, pyrolysis of tires and their frag-ments, as well as the prospects for their decomposition under the influence of environmental factors, in particular microorganisms, are also considered. The main ways of solving the prob-lem of tires that have lost their consumer properties in Ukraine are proposed. Bibl. 88, Fig. 2.


2003 ◽  
Vol 15 (3) ◽  
pp. 278-285
Author(s):  
Daigo Misaki ◽  
◽  
Shigeru Aomura ◽  
Noriyuki Aoyama

We discuss effective pattern recognition for contour images by hierarchical feature extraction. When pattern recognition is done for an unlimited object, it is effective to see the object in a perspective manner at the beginning and next to see in detail. General features are used for rough classification and local features are used for a more detailed classification. D-P matching is applied for classification of a typical contour image of individual class, which contains selected points called ""landmark""s, and rough classification is done. Features between these landmarks are analyzed and used as input data of neural networks for more detailed classification. We apply this to an illustrated referenced book of insects in which much information is classified hierarchically to verify the proposed method. By introducing landmarks, a neural network can be used effectively for pattern recognition of contour images.


PEDIATRICS ◽  
1971 ◽  
Vol 47 (6) ◽  
pp. 1103-1104
Author(s):  
David S. Walton

The authors begin their presentation–in this, the first textbook I know of devoted entirely to pediatric glaucomas–with a detailed classification of glaucomas in childhood. This is followed by a discussion of diagnostic techniques and the important clinical signs encountered in the pediatric glaucomas. A description of the conditions assoiated with childhood glaucomas follows, including a concise review of their distinguishing ocular features, with additional comments on treatment. The final section deals with methods of treatment; appropriate emphasis is given to the operative techniques used in performing a goniotomy.


1981 ◽  
Vol 33 (5) ◽  
pp. 1097-1110 ◽  
Author(s):  
A. T. Huckleberry ◽  
E. L. Livorni

Throughout this paper a surface is a 2-dimensional (not necessarily compact) complex manifold. A surface X is homogeneous if a complex Lie group G of holomorphic transformations acts holomorphically and transitively on it. Concisely, X is homogeneous if it can be identified with the left coset space G/H, where if is a closed complex Lie subgroup of G. We emphasize that the assumption that G is a complex Lie group is an essential part of the definition. For example, the 2-dimensional ball B2 is certainly “homogeneous” in the sense that its automorphism group acts transitively. But it is impossible to realize B2 as a homogeneous space in the above sense. The purpose of this paper is to give a detailed classification of the homogeneous surfaces. We give explicit descriptions of all possibilities.


Author(s):  
Nils Braakmann ◽  
Joachim Wagner

SummaryWe use unique rich data for German manufacturing enterprises to investigate the product diversification - firm performance relationship.We find that an increase in the degree of product diversification has a negative impact on profitability when observed and unobserved firm characteristics are controlled for. The effects are statistically significant and large from an economic point of view. This helps to understand the fact that nearly 40 percent of all enterprises with at least 20 employees are single-product firms according to a detailed classification of products, and that multi-product enterprises with a large number of goods are a rare species.


1896 ◽  
Vol 32 (4) ◽  
pp. 276-286
Author(s):  
Harald Westergaard

[After some interesting preliminary remarks on the subject of statistics generally, and the utility of interpolation in their preparation, Professor Westergaard points out that in vital statistics the enumeration of the population at each year of age is seldom wanted, and, in fact, owing to the well known exaggeration in census returns of the numbers living at decennial ages, an adjustment is generally needed. He then proceeds:] The decennial reports by the English Registrar-General of births, deaths and marriages, contain full materials for the study of the mortality of professional men. The report published in 1875 gives a very detailed classification of ages, but it is not so with the next decennial report, which divides the ages into five periods only—15–20, 20–25, 25–45, 45–65, 65 and upwards.


Radiocarbon ◽  
1959 ◽  
Vol 1 ◽  
pp. 199-214 ◽  
Author(s):  
Frederick Johnson

The scope of the problems which are involved in the determination of radiocarbon dates renders complete, or detailed, classification of the published results of the research most complicated. In assembling this bibliography several such classifications were discarded before the present simplified one emerged. It was found, for example, that in a detailed classification of subject titles a large number of papers would have to be listed under several, sometimes as many as four, different headings. This complicated and lengthened the listing and also materially increased the chance of inaccurately locating a title. In such an event it would be “lost” to all but the most meticulous searcher. The reduction in the number of subject headings is open to criticism. We suspect, however, that these are answered by the simplicity of the present outline.


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