Throughput and delay analysis of an opportunistic tree algorithm

Tree algorithms are a well-known class of random access algorithms with a provable maximum stable throughput under the infinite population model (as opposed to ALOHA or the binary exponential backoff algorithm). In this article, we propose a tree algorithm for opportunistic spectrum usage in cognitive radio networks. A channel in such a network is shared among so-called primary and secondary users, where the secondary users are allowed to use the channel only if there is no primary user activity. The tree algorithm designed in this article can be used by the secondary users to share the channel capacity left by the primary users.

We analyze the maximum stable throughput and mean packet delay of the secondary users by developing a tree structured Quasi-Birth Death Markov chain under the assumption that the primary user activity can be modeled by means of a finite state Markov chain and that packets lengths follow a discrete phase-type distribution.

Numerical experiments provide insight on the effect of various system parameters and indicate that the proposed algorithm is able to make good use of the bandwidth left by the primary users.     

Deaf studies meets autistic studies

What might deaf studies and autistic studies have in common? Why, in many cases, is deafness considered to be a norm to be analyzed through linguistic and cultural frameworks, while autism is (still) seen as pathological? Utilizing ethnographic research, participation in two conferences on autism and sign language, and an analysis of deaf peoples’ and autistic peoples’ self-(re)presentation, we attend to sensory solidarities that might exist between deaf and autistic people, communities, and studies. We argue that an analysis of the two fields side-by-side offers important insights into new ways of conceptualizing sociality, identity, and community both in the specific cases of deafness and autism, and more broadly. Additionally, attending to deaf and autistic peoples’ language and communication desires and practices opens up analytic and empirical space for considering interdependent and multimodal communicative approaches.     

100 key research questions for the post‐2015 development agenda

The Sustainable Development Goals (SDGs) herald a new phase for international development. This article presents the results of a consultative exercise to collaboratively identify 100 research questions of critical importance for the post‐2015 international development agenda. The final shortlist is grouped into nine thematic areas and was selected by 21 representatives of international and non‐governmental organisations and consultancies, and 14 academics with diverse disciplinary expertise from an initial pool of 704 questions submitted by 110 organisations based in 34 countries. The shortlist includes questions addressing long‐standing problems, new challenges and broader issues related to development policies, practices and institutions. Collectively, these questions are relevant for future development‐related research priorities of governmental and non‐governmental organisations worldwide and could act as focal points for transdisciplinary research collaborations.     

Road socialism

Road socialists maintain that government is the best manager for the nation's vehicular transportation arteries. Contrary to their views, the present author maintains that the managerial role can best be fulfilled by private entrepreneurs. Under highway privatization, he claims, traffic fatalities and automobile congestion will be sharply reduced.The author wishes to thank the North American Editor of Transport Policy, and an anonymous referee from the present journal, for helpful suggestions and commentary on an earlier draft of this paper.     

Professionalism and the physician leader

The perception of the well-respected, knowledgeable, empathetic physician of early 20th century medicine is slowly being eroded in American society today. Consider the causes of the breakdown and how to restore the image.     

CMHS/CSAT Collaborative Demonstration Program for Homeless Individuals

The Collaborative Demonstration Program for Homeless Individuals is providing an opportunity for several community agencies in the United States to explore innovative intervention and treatment strategies to address the needs of homeless people with co-occurring (mental illness and substance abuse) disorders. This cooperative agreement, funded jointly by the Center for Mental Health Services (CMHS) and the Center for Substance Abuse Treatment (CSAT), is a $3 million project supporting programs in various community agencies to develop, document, and evaluate programs for persons who are homeless with co-occurring disorders to be used as models in other communities. The program models include: Assertive Community Treatment, Psychosocial Rehabilitation, Therapeutic Community, and an integrated treatment model. The first phase of the two-phase project funded 16 programs in the U.S. to develop manuals within their primary treatment modalities for homeless people with co-occurring disorders. For Phase II of the project, six of the 16 model programs were competitively selected to demonstrate program impact through formal program evaluation efforts. The data derived from the various projects will be compiled into a compendium of information for state agencies and community service providers throughout the U.S.     

The Dilemma of Social Work Education: Restructuring the Curriculum

The roles of social work libraries are reexamined in light of recent trends in library information science The implementation of special services is advocated in the following areas: Information Retrieval and Selective Dissemination of Information (SDI) programs, computer-produced subject bibliographies, regional and national union catalogues in book format, cooperative acquisition plans, and improved interlibrary loan services. Local, regional, and national consortia social work libraries are seen as a possible approach, utilizing existing and future data bank networks.