Valuing Africa's inland fisheries: overview of current methodologies with an emphasis on livelihood analysis

While Africa’s inland fisheries are widely recognized to be of great importance to local people, accurate and up-to-date information on their value is sparse and its absence is a serious constraint to the formulation of effective fisheries policies and management practices. As a contribution to current efforts to address this constraint, this paper reviews the different methods that are potentially applicable to the valuation of inland fisheries and discusses their respective rationales and limitations within a multi-sectoral, multi-user context. The livelihood analysis approach is given special emphasis. The complementarity of this recently developed approach with the other, more conventional, environmental economics methods is illustrated.

First demonstration of a full C-band tunable WDM-PON system with novel high-temperature DS-DBR lasers

We demonstrate automatic operation of a cooler-less tunable-laser based WDM-PON system. Using a pilot-tone based overhead channel and centralized wavelength locking scheme, 1 Gb/s and 10 Gb/s data transmission is demonstrated in a multi-user set-up. © 2013 Optical Society of America.

基于单向陷门置换的长消息签密方案

在随机Oracle模型的基础上, 提出一种基于单向陷门置换（trapdoor permutations, TDPs）的、可并行的、长消息签密方案——PLSC （parallel long-message signcryption）. 该方法采用“整体搅乱, 局部加密（scramble all, and encrypt small）”的思想, 用一个伪随机数对要传送的消息和用户的身份（ID）进行“搅乱（scrambling operation）”, 然后对两个固定长度的小片段（并行地）进行单向陷门置换（TDP）操作. 这种设计使得整个方案可直接高效地处理任意长度的消息, 既可避免循环调用单向陷门置换（如CBC模式）所造成的计算资源的极度消耗, 也可避免由“对称加密方案”与“签密方案”进行“黑盒混合（black-box hybrid）”所造成的填充（padding）冗余. 不仅可以显著地节约消息带宽, 而且可以显著地提高整体效率. 具体地说, 该方法对任何长度的消息进行签密, 仅需进行一次接收方的TDP运算（相当于加密）, 以及一次发送方的TDP运算（相当于签名）, 从而最大限度地降低了TDP运算的次数, 提高了整体的运算效率. 因为, 对于公钥加密算法来说, 运算量主要集中在TDP运算上, TDP运算是整个算法的瓶颈所在. 另一方面, 由于避免了填充上的冗余, 新方案的效率也高于标准的“黑盒混合”方案.重要的是, 新方案能够达到选择密文攻击下的紧致的语义安全性（IND- CCA2）、密文完整性（INT-CTXT）以及不可否认性（non-repudiation）. 而且所有这些安全要求都可以在多用户（multi-user）、内部安全（insider-security）的环境下得以实现. 另外, 尽管新方案主要针对长消息的签密, 但它也可应用于某些不能进行大块数据处理的环境（智能卡或其他只有少量内存的环境）. 也就是说, 对于这些小内存设备来说, 仍然可以用该方案来实现长消息的签密处理.

一种个体软件过程能力度量方法

个体软件过程(PSP)是由卡内基×梅隆大学软件工程研究所的Humphrey领导开发的.它是一种可用于控制、管理和改进个人工作方式的自我持续改进过程.随着工业界对软件过程改进需求的日益增长,PSP成为了软件组织为达成完全(从宏观到微观)量化过程管理研究中的一个热点课题.软件过程研究表明,高水平的个体软件过程能力是软件项目成功的关键,如何进行有效的个体软件过程能力度量是PSP中的一个核心问题.现有方法不能同时有效处理个体软件过程能力度量中的可变规模收益、多变量输入/输出以及决策者偏好问题.提出了一种综合了数据包络分析(DEA)和层次分析法(AHP)的个体软件过程能力评价方法--PSPADA,介绍了PSPADA的个体软件过程能力评价模型和核心算法(集成决策者偏好和估计规模收益).实验结果显示,PSPADA能够在考虑决策者偏好的同时,有效地进行多指标、规模收益可变的量化评估.

Identifying functional stakeholder clusters to maximise communication for the ecosystem approach to fisheries management

Interaction with ecological models can improve stakeholder participation in fisheries management. Problems exist in efficiently communicating outputs to stakeholders and an objective method of structuring stakeholder differences is lacking. This paper aims to inform the design of a multi-user communication interface for fisheries management by identifying functional stakeholder groups. Intuitive categorisation of stakeholders, derived from survey responses, is contrasted with an Evidence-Based method derived from analysis of stakeholder literature. Intuitive categorisation relies on interpretation and professional judgement when categorising stakeholders among conventional stakeholder groups. Evidence-Based categorisation quantitatively characterises each stakeholder with a vector of four management objective interest-strength values (Yield, Employment, Profit and Ecosystem Preservation). Survey respondents agreed little in forming intuitive groups and the groups were poorly defined and heterogeneous in interests. In contrast the Evidence-Based clusters were well defined and largely homogeneous, so more useful for identifying functional relations with model outputs. The categorisations lead to two different clusterings of stakeholders and suggest unhelpful stereotyping of stakeholders may occur with the Intuitive categorisation method. Stakeholder clusters based on literature-evidence show a high degree of common interests among clusters and is encouraging for those seeking to maximise dialogue and consensus forming. © 2013 Elsevier Ltd.

Threshold-based substream selection for closed-loop spatial multiplexing

We propose a low-complexity closed-loop spatial multiplexing method with limited feedback over multi-input-multi-output (MIMO) fading channels. The transmit adaptation is simply performed by selecting transmit antennas (or substreams) by comparing their signal-to-noise ratios to a given threshold with a fixed nonadaptive constellation and fixed transmit power per substream. We analyze the performance of the proposed system by deriving closed-form expressions for spectral efficiency, average transmit power, and bit error rate (BER). Depending on practical system design constraints, the threshold is chosen to maximize the spectral efficiency (or minimize the average BER) subject to average transmit power and average BER (or spectral efficiency) constraints, respectively. We present numerical and Monte Carlo simulation results that validate our analysis. Compared to open-loop spatial multiplexing and other approaches that select the best antenna subset in spatial multiplexing, the numerical results illustrate that the proposed technique obtains significant power gains for the same BER and spectral efficiency. We also provide numerical results that show improvement over rate-adaptive orthogonal space-time block coding, which requires highly complex constellation adaptation. We analyze the impact of feedback delay using analytical and Monte Carlo approaches. The proposed approach is arguably the simplest possible adaptive spatial multiplexing system from an implementation point of view. However, our approach and analysis can be extended to other systems using multiple constellations and power levels.

Improving Bandwidth Efficiency in E-band Communication Systems

The allocation of a large amount of bandwidth by regulating bodies in the 70/80 GHz band, i.e., the E-band, has opened up new potentials and challenges for providing affordable and reliable Gigabit per second wireless point-to-point links. This article first reviews the available bandwidth and licensing regulations in the E-band. Subsequently, different propagation models, e.g., the ITU-R and Cane models, are compared against measurement results and it is concluded that to meet specific availability requirements, E-band wireless systems may need to be designed with larger fade margins compared to microwave systems. A similar comparison is carried out between measurements and models for oscillator phase noise. It is confirmed that phase noise characteristics, that are neglected by the models used for narrowband systems, need to be taken into account for the wideband systems deployed in the E-band. Next, a new multi-input multi-output (MIMO) transceiver design, termed continuous aperture phased (CAP)-MIMO, is presented. Simulations show that CAP-MIMO enables E-band systems to achieve fiber-optic like throughputs. Finally, it is argued that full-duplex relaying can be used to greatly enhance the coverage of E-band systems without sacrificing throughput, thus, facilitating their application in establishing the backhaul of heterogeneous networks.

Language learning and MUDs : an overview. 'Aprendizaje de idiomas y MUDs : una visión general'.

La traducción literal de MUD es Mazmorra o Calabozo multiusuario o Dimensión multiusuario. Un MUD es un juego de rol en línea que es ejecutado en un servidor. El artículo incluye direcciones de varios MUDs

Maximising concurrency and scalability in a consistent, causal, distributed virtual reality system, whilst minimising the effect of network delays

The development of large scale virtual reality and simulation systems have been mostly driven by the DIS and HLA standards community. A number of issues are coming to light about the applicability of these standards, in their present state, to the support of general multi-user VR systems. This paper pinpoints four issues that must be readdressed before large scale virtual reality systems become accessible to a larger commercial and public domain: a reduction in the effects of network delays; scalable causal event delivery; update control; and scalable reliable communication. Each of these issues is tackled through a common theme of combining wall clock and causal time-related entity behaviour, knowledge of network delays and prediction of entity behaviour, that together overcome many of the effects of network delay.

Maximising concurrency and scalability in a consistent, causal, distributed virtual reality system, whilst minimising the effect of network delays

The development of large scale virtual reality and simulation systems have been mostly driven by the DIS and HLA standards community. A number of issues are coming to light about the applicability of these standards, in their present state, to the support of general multi-user VR systems. This paper pinpoints four issues that must be readdressed before large scale virtual reality systems become accessible to a larger commercial and public domain: a reduction in the effects of network delays; scalable causal event delivery; update control; and scalable reliable communication. Each of these issues is tackled through a common theme of combining wall clock and causal time-related entity behaviour, knowledge of network delays and prediction of entity behaviour, that together overcome many of the effects of network delays.

A Real-time, Predictive Architecture for Distributed Virtual Reality

User interaction within a virtual environment may take various forms: a teleconferencing application will require users to speak to each other (Geak, 1993), with computer supported co-operative working; an Engineer may wish to pass an object to another user for examination; in a battle field simulation (McDonough, 1992), users might exchange fire. In all cases it is necessary for the actions of one user to be presented to the others sufficiently quickly to allow realistic interaction. In this paper we take a fresh look at the approach of virtual reality operating systems by tackling the underlying issues of creating real-time multi-user environments.

Continuous prewarping of time for multiuser interactive virtual environments

Dynamic multi-user interactions in a single networked virtual environment suffer from abrupt state transition problems due to communication delays arising from network latency--an action by one user only becoming apparent to another user after the communication delay. This results in a temporal suspension of the environment for the duration of the delay--the virtual world `hangs'--followed by an abrupt jump to make up for the time lost due to the delay so that the current state of the virtual world is displayed. These discontinuities appear unnatural and disconcerting to the users. This paper proposes a novel method of warping times associated with users to ensure that each user views a continuous version of the virtual world, such that no hangs or jumps occur despite other user interactions. Objects passed between users within the environment are parameterized, not by real time, but by a virtual local time, generated by continuously warping real time. This virtual time periodically realigns itself with real time as the virtual environment evolves. The concept of a local user dynamically warping the local time is also introduced. As a result, the users are shielded from viewing discontinuities within their virtual worlds, consequently enhancing the realism of the virtual environment.

An Environmental Analysis Corroborating PDA and the Winthrop Example

Libraries seek active ways to innovate amidst macroeconomic shifts, growing online education to help alleviate ever-growing schedule conflicts as students juggle jobs and course schedules, as well as changing business models in publishing and evolving information technologies. Patron-driven acquisition (PDA), also known as demand-driven acquisition (DDA), offers numerous strengths in supporting university curricula in the context of these significant shifts. PDA is a business model centered on short-term loans and subsequent purchases of ebooks resulting directly from patrons' natural use stemming from their discovery of the ebooks in library catalogs where the ebooks' bibliographic records are loaded at regular intervals established between the library and ebook supplier. Winthrop University's PDA plan went live in October 2011, and this article chronicles the philosophical and operational considerations, the in-library collaboration, and technical preparations in concert with the library system vendor and ebook supplier. Short-term loan is invoked after a threshold is crossed, typically number of pages or time spent in the ebook. After a certain number of short-term loans negotiated between the library and ebook supplier, the next short-term loan becomes an automatic purchase after which the library owns the ebook in perpetuity. Purchasing options include single-user and multi-user licenses. Owing to high levels of need in college and university environments, Winthrop chose the multi-user license as the preferred default purchase. Only where multi-user licenses are unavailable does the automatic purchase occur with single-user title licenses. Data on initial use between October 2011 and February 2013 reveal that of all PDA ebooks viewed, only 30% crossed the threshold into short-term loans. Of all triggered short-term loans, Psychology was the highest-using. Of all ebook views too brief to trigger short-term loans, Business was the highest-using area. Although the data are still too young to draw conclusions after only a few months, thought-provoking usage differences between academic disciplines have begun to emerge. These differences should be considered in library plans for the best possible curricular support for each academic program. As higher education struggles with costs and course-delivery methods libraries have an enduring lead role.

H-N2N : uma arquitetura hierárquica escalável para ambientes de realidade mista de grande porte

In this work, we propose a solution to solve the scalability problem found in collaborative, virtual and mixed reality environments of large scale, that use the hierarchical client-server model. Basically, we use a hierarchy of servers. When the capacity of a server is reached, a new server is created as a sun of the first one, and the system load is distributed between them (father and sun). We propose efficient tools and techniques for solving problems inherent to client-server model, as the definition of clusters of users, distribution and redistribution of users through the servers, and some mixing and filtering operations, that are necessary to reduce flow between servers. The new model was tested, in simulation, emulation and in interactive applications that were implemented. The results of these experimentations show enhancements in the traditional, previous models indicating the usability of the proposed in problems of all-to-all communications. This is the case of interactive games and other applications devoted to Internet (including multi-user environments) and interactive applications of the Brazilian Digital Television System, to be developed by the research group. Keywords: large scale virtual environments, interactive digital tv, distributed

GATE - Uma abordagem baseada em middleware para aplicações interperceptivas envolvendo múltiplos dispositivos

In this work, we present the GATE, an approach based on middleware for interperceptive applications. Through the services offered by the GATE, we extension we extend the concept of Interperception for integration with several devices, including set-top box, mobile devices (cell phones), among others. Through this extension ensures the implementation of virtual environments in these devices. Thus, users who access the version of the computer environment may interact with those who access the same environment by other devices. This extension is just a part of the services provided by the GATE, that remerges as a new proposal for multi-user virtual environments creation.