Basic System (basic + system)

Distribution by Scientific Domains

Selected Abstracts

QOS and call admission control of multimedia traffic in a PCS network

Duan-Shin Lee
Abstract In this paper we study the quality of service of integrated voice and data services in a wireless network. The voice traffic is transmitted in circuit-switched mode and data traffic is transmitted in packet-switched mode. Voice traffic has high transmission priority and data packets are transmitted only when there are available channels not used by the voice traffic. Otherwise, the data packets wait in a data buffer. We consider two schemes to reduce the forced termination probability for the handoff voice calls. The two schemes are the reserved channel scheme and the queueing priority scheme. We apply a fluid analysis to study the performance of the data buffer under the two handoff schemes and the basic system in which there is no arrangement to reduce the forced termination probability of handoff calls. From this analysis, we derive admission controls for voice traffic as well as for data traffic. This analysis also enables us to conclude that the reserved channel scheme not only is more effective in reducing the forced termination probability of handoff calls, it is also more effective in providing the QOS guarantee for the data traffic. Another contribution of this paper is to develop a perturbation analysis to solve the fluid models efficiently and quickly. Copyright 2004 John Wiley & Sons, Ltd. [source]

Performance improvement of the vapour compression refrigeration cycle by a two-phase constant area ejector

Nagihan Bilir
Abstract The performance of a vapour compression system that uses an ejector as an expansion device was investigated. In the analysis, a two-phase constant area ejector flow model was used. R134a was selected as the refrigerant. According to the obtained results, for any operating temperature there are different optimum values of pressure drop in the suction chamber, ejector area ratio, ejector outlet pressure and cooling coefficient of performance (COP). As the difference between condenser and evaporator temperatures increases, the improvement ratio in COP rises whereas ejector area ratio drops. The minimum COP improvement ratio in the investigated field was 10.1%, while its maximum was 22.34%. Even in the case of an off-design operation, the performance of a system with ejector is higher than that of the basic system. Copyright 2008 John Wiley & Sons, Ltd. [source]

Using OXSIM for path planning

Stephen Cameron
We address the issue of building scalable and reusable path planners for realistic robot manipulators working in three-dimensional space amid complex geometry, by presenting the latest version of our robot manipulator planning toolbox, OxSIM. OxSIM is designed to greatly simplify the building of planners by providing core competence in three-dimensional geometry. This is done by the provision of efficient routines for computing the distance between parts of the robot and its environment. A new version of OXSIM, written in C++, provides an object-oriented interface to the basic system, which increases its ease of use. Here we give an overview of OxSIM and how it works and describe a modified version of the probabilistic road map planner that we have implemented under the framework. 2001 John Wiley & Sons, Inc. [source]

Compactness under constructive scrutiny

Hajime Ishihara
Abstract How are the various classically equivalent definitions of compactness for metric spaces constructively interrelated? This question is addressed with Bishop-style constructive mathematics as the basic system , that is, the underlying logic is the intuitionistic one enriched with the principle of dependent choices. Besides surveying today's knowledge, the consequences and equivalents of several sequential notions of compactness are investigated. For instance, we establish the perhaps unexpected constructive implication that every sequentially compact separable metric space is totally bounded. As a by-product, the fan theorem for detachable bars of the complete binary fan proves to be necessary for the unit interval possessing the Heine-Borel property for coverings by countably many possibly empty open balls. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Dynamic stability of a porous rectangular plate

Daniel Debowski
The study is devoted to a axial compressed porous-cellular rectangular plate. Mechanical properties of the plate vary across is its thickness which is defined by the non-linear function with dimensionless variable and coefficient of porosity. The material model used in the current paper is as described by Magnucki, Stasiewicz papers. The middle plane of the plate is the symmetry plane. First of all, a displacement field of any cross section of the plane was defined. The geometric and physical (according to Hook's law) relationships are linear. Afterwards, the components of strain and stress states in the plate were found. The Hamilton's principle to the problem of dynamic stability is used. This principle was allowed to formulate a system of five differential equations of dynamic stability of the plate satisfying boundary conditions. This basic system of differential equations was approximately solved with the use of Galerkin's method. The forms of unknown functions were assumed and the system of equations was reduced to a single ordinary differential equation of motion. The critical load determined used numerically processed was solved. Results of solution shown in the Figures for a family of isotropic porous-cellular plates. The effect of porosity on the critical loads is presented. In the particular case of a rectangular plate made of an isotropic homogeneous material, the elasticity coefficients do not depend on the coordinate (thickness direction), giving a classical plate. The results obtained for porous plates are compared to a homogeneous isotropic rectangular plate. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Occupational therapists' perception of their practice: A phenomenological study

Liv Grethe Kinn
Background:,International literature seems consistent in reporting that occupational therapists value their methods. However, little empirical evidence has been generated supporting the basic system of belief for occupational therapy. Few studies have explored the nature of the occupational therapists' experiences and thoughts about their use of occupation as means and ends, and which strategies they use to implement their tools in their current practice. Accordingly, the aim of this study was to explore how occupational therapists understood and presented their practice and interventions. Methods:,A sample of six occupational therapists graduated in different decades, from diverse client populations and health-care settings was selected to participate in a semistructured interview. Results:,Three main themes were developed: ,To make the client's potentials visible', ,reaching a position one values' and ,looking with other eyes'. Whatever their specialities, the participants were unanimous in the way they described their role. Their common focus was ,activities of daily living'. However, they had problems describing their therapeutic tools, and were not able to clearly articulate the ,common sense aspects' of their own methods. The participants were engaged in constructing their professional identities, and stressed the need to construct professional boundaries relevant to their particular work. Conclusion:,The occupational therapists perceived their practice and interventions as distinctly different from other team members, thus, they provided a ,counterpoint'. The participants used various ways of marketing their perspectives. While the novices tended to go along with the team, the experienced therapists tended to assert their own special contribution. [source]

Effective Contracting of Social Services

Barbara Peat
The continued growth in the use of privatization for the delivery of social services increases the need for a systematic method to analyze the contracting process. Using a modified form of the basic systems model, the authors examine the impact of antecedents and situational factors and explore the use of traditional management steps in the contracting process. The authors focus on one state's experience with contracting to explore the implications of such a model. [source]

Panic disorder: from respiration to the homeostatic brain

Giampaolo Perna
There is some experimental evidence to support the existence of a connection between panic and respiration. However, only recent studies investigating the complexity of respiratory physiology have revealed consistent irregularities in respiratory pattern, suggesting that these abnormalities might be a vulnerability factor to panic attacks. The source of the high irregularity observed, together with unpleasant respiratory sensations in patients with panic disorder (PD), is still unclear and different underlying mechanisms might be hypothesized. It could be the result of compensatory responses to abnormal respiratory inputs or an intrinsic deranged activity in the brainstem network shaping the respiratory rhythm. Moreover, since basic physiological functions in the organism are strictly interrelated, with reciprocal modulations and abnormalities in cardiac and balance system function having been described in PD, the respiratory findings might arise from perturbations of these other basic systems or a more general dysfunction of the homeostatic brain. Phylogenetically ancient brain circuits process physiological perceptions/sensations linked to homeostatic functions, such as respiration, and the parabrachial nucleus might filter and integrate interoceptive information from the basic homeostatic functions. These physiological processes take place continuously and subconsciously and only occasionally do they pervade the conscious awareness as ,primal emotions'. Panic attacks could be the expression of primal emotion arising from an abnormal modulation of the respiratory/homeostatic functions. [source]