Suchergebnisse

Characterizing World Wide Web proxy traffic helps identify parameters that affect caching, capacity planning and simulation studies. In this paper we identify invariants that hold across a collection of ten traces representing traffic seen by caching-proxy servers. The traces were collected from governmental, industry, university, high school, and an online service provider environment, with request rates that range from a few accesses to millions of accesses per hour. We also show that the examined traffic is semi-similar. We explore sources of Web self-similarity and we conclude that a strong source is the periodicity in the users behavior. The tests revealed that there is a strong connection between access rate from hour to hour. We also report the hit rate and weighted hit rate obtained by running a trace driven simulation on the workloads to simulate a proxy with infinite cache, similarly, accesses to unique servers and URLs are a small portion of the total. By considering these characteristics of traffic we can improve the utility of caching for WWW clients.

The 2008 financial crisis raised puzzles important for understanding how the capital market prices common stocks and in turn, for the intersection between law and finance. During the crisis, there was a dramatic five-fold spike, across all industries, in "idio­syncratic risk"—the volatility of individual-firm share prices after adjustment for movements in the market as a whole. This phenomenon is not limited to the most recent financial crisis. This Article uses an empirical review to show that a dramatic spike in idiosyncratic risk has occurred with every major downturn from the 1920s through the recent financial crisis. It canvasses three possible explanations for this phenomenon. Thereafter, this Article explores the implications of these crisis-induced volatility spikes for certain legal issues that depend analytically on valuation methodology and hence are affected by volatility: using event studies to determine materiality and loss causation in fraud-on-the-market securities litigation, determining materiality in cases involving claims of both insider trading and misstatements or omissions in registered public offerings, and deter­mining the extent of deference given to a corporate board that rejects an acquisition offer at a premium above the pre-offer market price. This analysis shows that the conventional use of event studies during periods of economic-crisis-induced volatility spikes results in understating the number of occasions when a corporate misstatement can be shown to have had a meaningful impact on a firm's stock price. Relatedly, the analysis suggests that during crisis times, insiders have substantially more opportunities to profit from trading on the nonpublic information that they possess and issuers conducting offerings have more opportunities to sell securities at an inflated price. Analysis shows that trying to cure this problem by lowering the standard of what is considered statistically significant is as likely to be socially harmful as socially beneficial. These conclusions counsel that the best response to the reduced effectiveness of private litigation as a deterrent to securities law violations during crisis times is to provide additional resources to SEC enforcement. Lastly, with respect to Delaware courts' recognition of "substantive coercion" as a justification for target-corporation deploy­ment of takeover defenses—arguably a dubious justification in normal times—crisis-induced idiosyncratic-risk spikes provide an unusually plausible claim that target shareholders may indeed make a mistake in tendering into a hostile offer. Analysis of the timing of the spikes in recent cases, however, shows that the claim is tenuous even in these circumstances.

The goals of this project are to ingest tweets and Web-based content from social media and the general Web, including news and governmental information. In addition to archiving materials found, the project team will build an information system that includes related metadata and knowledge bases, consistent with the 5S (Societies, Scenarios, Spaces, Structures, Streams) framework, along with results from our intelligent focused crawler, to support comprehensive access to event related content. With the support of key partners, the IDEAL team will undertake important research, education, and dissemination efforts, to achieve three complementary objectives: 1. Collecting: The project team will spot, identify, and make sense of interesting events. We also will accept specific or general requests about types of events. Given resource and sampling constraints, we will integrate methods to identify appropriate URLs as seeds, and specify when to start crawling and when to stop, with regard to each event or sub-event. We will integrate focused crawling and filtering approaches in order to ingest content and generate new collections, with high precision and recall. 2. Archiving & Accessing: Permanent archiving, and access to those archives, will be ensured by our partner, Internet Archive (IA). Immediate access to ingested content will be facilitated through big data software built on top of our new Hadoop cluster. 3. Analyzing & Visualizing: We will provide a wide range of integrated services beyond the usual (faceted) browsing and searching, including: classification, clustering, summarization, text mining, theme and topic identification, and visualization.

In this paper we briefly examine the use of Twitter in Iran, Tunisia and Egypt during the mass political demonstrations and protests in June 2009, December 2010 and January 2011 respectively. We compare this usage with methods and findings from other studies on the use of Twitter in emergency situations, such as natural and man-made disasters. We draw on my own experiences and participant-observations as an eyewitness in Iran, and on Twitter data from Tunisia and Egypt. In these three cases, Twitter filled a unique technology and communication gap at least partially. We summarize suggested directions for future research with a view of placing this work in the larger context of social media use in conditions of crisis or social convergence. ; Presented at CHI 2011, May 7-12, Vancouver, Canada

In this paper we examine the use of social media, and especially Twitter, in Iran, Tunisia and Egypt during the mass political demonstrations and protests in June 2009, December 2010 - January 2011, and February 2011, respectively. We compare this usage with methods and findings from other studies on the use of Twitter in emergency situations, such as natural and man-made disasters. We draw on our own experiences and participant-observations as an eyewitness in Iran (first author), and on Twitter data from Iran, Tunisia and Egypt. In these three cases, Twitter filled a unique technology and communication gap at least partially. We summarize suggested directions for future research with a view of placing this work in the larger context of social media use in conditions of crisis and social convergence.

This poster presents one of our efforts developed in the context of Crisis, Tragedy, and Recovery Network (CTRnet) project. One of our derived works from this project is the use of social media by government to respond to emergency events in towns and counties. Monitoring social media information for unusual behavior can help identify these events once we can characterize their patterns. As an example, we analyzed the campus shooting occurred in the University of Texas, Austin, on September 28, 2010. In order to study the pattern of communication and the information communicated using social media on that day, we collected publicly available data from Twitter. Collected tweets were analyzed and visualized using Natural Language Toolkit, word clouds, and graphs. They showed how news and posts related to this event swamped the discussions of other issues.