Carleton University

About: Carleton University is a education organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 15852 authors who have published 39650 publications receiving 1106610 citations.

A note on preliminary tests of equality of variances.

Abstract: Preliminary tests of equality of variances used before a test of location are no longer widely recommended by statisticians, although they persist in some textbooks and software packages. The present study extends the findings of previous studies and provides further reasons for discontinuing the use of preliminary tests. The study found Type I error rates of a two-stage procedure, consisting of a preliminary Levene test on samples of different sizes with unequal variances, followed by either a Student pooled-variances t test or a Welch separate-variances t test. Simulations disclosed that the twostage procedure fails to protect the significance level and usually makes the situation worse. Earlier studies have shown that preliminary tests often adversely affect the size of the test, and also that the Welch test is superior to the t test when variances are unequal. The present simulations reveal that changes in Type I error rates are greater when sample sizes are smaller, when the difference in variances is slight rather than extreme, and when the significance level is more stringent. Furthermore, the validity of the Welch test deteriorates if it is used only on those occasions where a preliminary test indicates it is needed. Optimum protection is assured by using a separate-variances test unconditionally whenever sample sizes are unequal.

Habitat use by black rat snakes (elaphe obsoleta obsoleta) in fragmented forests

Abstract: Declining nest success of forest birds in fragmented habitat has been attri- buted to increased nest predation. Better understanding of this problem and potential so- lutions to it require information on why nest predators are attracted to habitat edges. Toward this end we investigated habitat use by black rat snakes (Elaphe obsoleta obsoleta), an important avian-nest predator in eastern deciduous forests. We radio-tracked 52 black rat snakes for periods of 3-41 mo from 1996 to 1999. All black rat snakes exhibited a strong preference for edge habitats. Consistent with edges being used because they facilitate thermoregulation, gravid females associated more strongly with edges than did males and nongravid females, and sites used by snakes when shedding were significantly associated with habitat edges. Gravid females lost an average of >20% of their body mass, while nongravid females and males did not lose mass, suggesting that edges were not used because they offered high success in foraging. Similarly, an increase in use of edge habitat through the season by all rat snakes was inconsistent with the snakes being attracted principally to hunt: avian prey would have been more abundant in spring when birds were breeding, and the density of small mammals in edges did not vary seasonally. Also, snakes moved longer distances and were found traveling.more often when located in forests. Because our results collectively are most consistent with the hypothesis that rat snakes use edges for ther- moregulatory reasons, the negative impact of the snakes on nesting birds may be coinci- dental; the snakes primarily use edges for reasons other than foraging but opportunistically exploit prey they encounter there. Rat snakes appeared to respond to the edge structure rather than to how the edge was created (natural vs. artificial). Thus, fragmentation of forests by humans has created habitat structurally similar to that preferred by rat snakes in their natural habitat, thereby inadvertently increasing contact between the snakes and nesting birds.

Social behavior of the little brown bat, Myotis lucifugus

Abstract: 1. As part of an overall study of the social behavior of the little brown bat, Myotis lucifugus, we compiled the vocal repertoire of this gregarious species in its natural habitat. Ten vocalizations were identified and associated with certain behavioral contexts. 2. Echolocation pulses, although primarily used for or entation, are also available as interindividual communication signals and modified forms are used in several situations such as during near-collisions in flight and the first flights of newly volant young. 3. Nonecholocation calls are used in three main contexts. Agonistic vocalizations appear to take the place of physical aggression and may be used to protect an individual's position within a roost. Two vocalizations emitted in maternal-infant situations appear to contain vocal signatures which are important for individual recognition. During mating, a distinct copulation call given by males likely conveys a male's sexual motivation to a female in the absence of precopulatory displays. 4. The size of the vocal repertoire is comparable to those of some solitary mammals. Behavioral observations indicate that despite the gregarious nature of the species, a simple social system exists and the small repertoire is therefore not surprising.

Supersymmetry parameter analysis : SPA convention and project

Abstract: High-precision analyses of supersymmetry parameters aim at reconstructing the fundamental supersymmetric theory and its breaking mechanism. A well defined theoretical framework is needed when higher-order corrections are included. We propose such a scheme, Supersymmetry Parameter Analysis SPA, based on a consistent set of conventions and input parameters. A repository for computer programs is provided which connect parameters in different schemes and relate the Lagrangian parameters to physical observables at LHC and high energy e(+)e(-) linear collider experiments, i.e., masses, mixings, decay widths and production cross sections for supersymmetric particles. In addition, programs for calculating high-precision low energy observables, the density of cold dark matter (CDM) in the universe as well as the cross sections for CDM search experiments are included. The SPA scheme still requires extended efforts on both the theoretical and experimental side before data can be evaluated in the future at the level of the desired precision. We take here an initial step of testing the SPA scheme by applying the techniques involved to a specific supersymmetry reference point.

Performance Optimization for Blockchain-Enabled Industrial Internet of Things (IIoT) Systems: A Deep Reinforcement Learning Approach

Abstract: Recent advances in the industrial Internet of things (IIoT) provide plenty of opportunities for various industries. To address the security and efficiency issues of the massive IIoT data, blockchain is widely considered as a promising solution to enable data storing/processing/sharing in a secure and efficient way. To meet the high throughput requirement, this paper proposes a novel deep reinforcement learning (DRL)-based performance optimization framework for blockchain-enabled IIoT systems, the goals of which are threefold: 1) providing a methodology for evaluating the system from the aspects of scalability, decentralization, latency, and security; 2) improving the scalability of the underlying blockchain without affecting the system's decentralization, latency, and security; and 3) designing a modulable blockchain for IIoT systems, where the block producers, consensus algorithm, block size, and block interval can be selected/adjusted using the DRL technique. Simulations results show that our proposed framework can effectively improve the performance of blockchain-enabled IIoT systems and well adapt to the dynamics of the IIoT.