Relative group cohomology and the orbit category

Cataloged from PDF version of article.Let G be a finite group and ℱ be a family of subgroups of G closed under conjugation and taking subgroups. We consider the question whether there exists a periodic relative ℱ-projective resolution for ℤ when ℱ is the family of all subgroups H ≤ G with rk H ≤ rkG - 1. We answer this question negatively by calculating the relative group cohomology ℱH*(G, F{double-struck}2) where G = ℤ/2 × ℤ/2 and ℱ is the family of cyclic subgroups of G. To do this calculation we first observe that the relative group cohomology ℱH*(G, M) can be calculated using the ext-groups over the orbit category of G restricted to the family ℱ. In second part of the paper, we discuss the construction of a spectral sequence that converges to the cohomology of a group G and whose horizontal line at E 2 page is isomorphic to the relative group cohomology of G. © 2014 Copyright Taylor & Francis Group, LLC

An algorithm for energy-efficient bluetooth scatternet formation and maintenance

We discuss an energy-efficient, distributed Bluetooth Scatternet Formation algorithm based on Device and Link characteristics (SF-DeviL). SF-DeviL forms multihop scatternets with tree topologies and increases battery lif etimes of devices by using device types, battery levels and received signal strengths. The topology is dynamically reconfigured in SF-DeviL by depleting battery levels and it is shown through simulations that the network lifetime is increased by at least 32% compared to LMS algorithm [1]

SF-Devil: Distributed Bluetooth scatternet formation algorithm based on device and link characteristics

Bluetooth has become very popular owing to the fact that it is a promising ad-hoc networking technology for short ranges. Although construction and operation of piconets is well defined in Bluetooth specifications, there is no unique standard for scatternet formation and operation. In this paper, we propose a distributed Bluetooth scatternet formation algorithm based on device and link characteristics (SF-DeviL). SF-DeviL handles energy efficiency using class devices and the received signal strength. SF-DeviL forms scatternets that are robust to position changes and battery depletions. © 2003 IEEE

A two phase successive cancellation decoder architecture for polar codes

We propose a two-phase successive cancellation (TPSC) decoder architecture for polar codes that exploits the array-code property of polar codes by breaking the decoding of a length-TV polar code into a series of length-√ L decoding cycles. Each decoding cycle consists of two phases: a first phase for decoding along the columns and a second phase for decoding along the rows of the code array. The reduced decoder size makes it more affordable to implement the core decoder logic using distributed memory elements consisting of flip-flops (FFs), as opposed to slower random access memory (RAM), leading to a speed up in clock frequency. To minimize the circuit complexity, a single decoder unit is used in both phases with minor modifications. The re-use of the same decoder module makes it necessary to recall certain internal decoder state variables between decoding cycles. Instead of storing the decoder state variables in RAM, the decoder discards them and calculates them again when needed. Overall, the decoder has O(√ L) circuit complexity excluding RAM, and a latency of approximately 2.57V. A RAM of size O(N) is needed for storing the channel log-likelihood variables and the decoder decision variables. As an example of the proposed method, a length N = 214 bit polar code is implemented in an FPGA and the synthesis results are compared with a previously reported FPGA implementation. The results show that the proposed architecture has lower complexity, lower memory utilization with higher throughput, and a clock frequency that is less sensitive to code length. © 2013 IEEE

Decentralised innovation systems and poverty reduction: experimental evidence from Central Africa

We use experimental data to investigate whether a decentralised approach to promoting innovation in central African agriculture outperforms conventional extension ap proaches. Our main result is that this decentralised approach, based on so-called innova tion platforms, is effective in reducing poverty – more effective than conventional extension approaches. However, we also document considerable heterogeneity in terms of platform performance

Acylation Reaction of Polystyrene with Organic Anhydrides and Investigation of the Physico-Mechanical Properties

The acylation reaction of polystyrene with organic anhydrides, such as maleic and ace-tic anhydrides were investigated in the presence of cationic catalysis (AlCl3, BF3В·O(C2H5)2, FeCl3, SnCl4, TiCl4, ZnCl2), to synthesise some polyfunctional (carbonyl-, carboxyl-, keto-, olefinic) polystyrene. The incorporation of functional groups to polystyrene were caused an increase of adhesion capability, physico-mechanical properties, elasticity and photosensitivity polyfunctional product

The Future Mortality of High Mortality Countries: A Model Incorporating Expert Arguments

This paper examines the future of mortality in the 65 countries still experiencing high mortality in 2010, as defined by a cutoff of 40 deaths before age five per thousand live births. Mortality declines in several countries stagnated or reversed in the last two decades of the twentieth century due mainly to HIV/AIDS. The forces underlying past mortality trends and affecting the future course of mortality are examined by reviewing the existing literature and reporting the results of the global survey and invited meeting, both involving mortality experts. The experts assessed the likelihood and weight of forces hypothesized to influence mortality. A statistical model is combined with these expert assessments to produce a set of mortality assumptions that are incorporated into the projections reported in this paper. This paper also addresses the limited availability of reliable data on age-specific mortality rates

Ceramics studio to podiatry clinic: The impact of multi-media resources in the teaching of practical skills across diverse disciplines

This paper draws on the experiences of students from two vastly different disciplines to both explore the theoretical background supporting the use of multimedia resources to teach practical skills and provide a qualitative evaluation of student perceptions and experiences of using bespoke resources. Within ceramics and podiatry, practical skills are traditionally taught via an apprenticeship model within small groups. We explore the practical and pedagogic benefits of developing bespoke multimedia resources to teach practical skills, identifying common themes from these disparate discipline areas. Student focus groups revealed that, practically, the opportunity for repeated viewing at convenient times promoted less reliance on lecturers and better preparation prior to practical demonstrations. Pedagogically, time for reflection and sense making underpinned an increase in confidence which in turn led to increased creativity. The student voice was also used to identify recommendations and challenges driving future change