HFR Code: A Flexible Replication Scheme for Cloud Storage Systems

Fractional repetition (FR) codes are a family of repair-efficient storage codes that provide exact and uncoded node repair at the minimum bandwidth regenerating point. The advantageous repair properties are achieved by a tailor-made two-layer encoding scheme which concatenates an outer maximum-distance-separable (MDS) code and an inner repetition code. In this paper, we generalize the application of FR codes and propose heterogeneous fractional repetition (HFR) code, which is adaptable to the scenario where the repetition degrees of coded packets are different. We provide explicit code constructions by utilizing group divisible designs, which allow the design of HFR codes over a large range of parameters. The constructed codes achieve the system storage capacity under random access repair and have multiple repair alternatives for node failures. Further, we take advantage of the systematic feature of MDS codes and present a novel design framework of HFR codes, in which storage nodes can be wisely partitioned into clusters such that data reconstruction time can be reduced when contacting nodes in the same cluster.Comment: Accepted for publication in IET Communications, Jul. 201

A Cone-Shaped Typology of Destination Cities in the United States

Based on a panel survey of Americans’ travel behavior, this study adopts cluster analysis and discriminant analysis to build a typology of destination cities in the United States. Past studies relied on supply-side characteristics such as types of attractors and seasonality to categorize destinations; this study adopted tripographic variables for the cluster analysis, such as estimated annual tourist volumes, tourist ratios, trip purposes, accommodation types, trip lengths, and transportation modes. The results validated the 11 cluster solution of cities in the United States. The discriminant analysis results in six discriminant functions in which four are corresponding to the clustering variables. The finding could be useful for various destination marketing, competition, and benchmarking research

Microsofts Monopoly: Anti-Competitive Behavior, Predatory Tactics, And The Failure Of Governmental Will

Thirty years ago, Microsoft Corp. was founded by Bill Gates and Paul Allen.  To understand how the company has gained competitive advantage we examine how the company used unfair, anti-competitive, and predatory approaches in their business.  We discuss how we have come to the belief that the government settlement in United States and State of New York, et al., v. Microsoft Corporation imposing restrictions on Microsoft’s behavior and monitoring its actions for compliance is not enough to keep it from abusing its monopolistic power and does too little to prevent it from dominating the software and operating system industry today

Investigations of afterpulsing and detection efficiency recovery in superconducting nanowire single-photon detectors

We report on the observation of a non-uniform dark count rate in Superconducting Nanowire Single Photon Detectors (SNSPDs), specifically focusing on an afterpulsing effect present when the SNSPD is operated at a high bias current regime. The afterpulsing exists for real detection events (triggered by input photons) as well as for dark counts (no laser input). In our standard set-up, the afterpulsing is most likely to occur at around 180 ns following a detection event, for both real counts and dark counts. We characterize the afterpulsing behavior and speculate that it is not due to the SNSPD itself but rather the amplifiers used to boost the electrical output signal from the SNSPD. We show that the afterpulsing indeed disappears when we use a different amplifier with a better low frequency response. We also examine the short-lived enhancement of detection efficiency during the recovery of the SNSPD due to temporary perturbation of the bias and grounding conditions