Design and analysis of fault-tolerant multibus interconnection networks

AbstractIn this paper a new class of fault-tolerant multibus interconnection networks is presented and analyzed. Efficiency and fault tolerance have been the driving forces in the design of these structures. The most common types of faults have been explicitly considered and in particular the jabbering problem has been adequately resolved. The analysis covers the evaluation of capacity, throughput and average delay and it includes faults of one or more channels. The system is shown to be very efficient and to be able to adequately support channel and station faults

Modeling of Call Dropping in Well-Established Cellular Networks

The increasing offer of advanced services in cellular networks forces operators to provide stringent QoS guarantees. This objective can be achieved by applying several optimization procedures. One of the most important indexes for QoS monitoring is the drop-call probability that, till now, has not deeply studied in the context of a well-established cellular network. To bridge this gap, starting from an accurate statistical analysis of real data, in this paper an original analytical model of the call dropping phenomenon has been developed. Data analysis confirms that models already available in literature, considering handover failure as the main call dropping cause, give a minor contribution for service optimization in established networks. In fact, many other phenomena become more relevant in influencing the call dropping. The proposed model relates the drop-call probability with traffic parameters. Its effectiveness has been validated by experimental measures. Moreover, results show how each traffic parameter affects system performance

Video Smoothing of Aggregates of Streams with Bandwidth Constraints

Compressed variable bit rate (VBR) video transmission is acquiring a growing importance in the telecommunication world. High data rate variability of compressed video over multiple time scales makes an efficient bandwidth resource utilization difficult to obtain. One of the approaches developed to face this problem are smoothing techniques. Various smoothing algorithms that exploit client buffers have been proposed, thus reducing the peak rate and high rate variability by efficiently scheduling the video data to be transmitted over the network. The novel smoothing algorithm proposed in this paper, which represents a significant improvements over the existing methods, performs data scheduling both for a single stream and for stream aggregations, by taking into account available bandwidth constraints. It modifies, whenever possible, the smoothing schedule in such a way as to eliminate frame losses due to available bandwidth limitations. This technique can be applied to any smoothing algorithm already present in literature and can be usefully exploited to minimize losses in multiplexed stream scenarios, like Terrestrial Digital Video Broadcasting (DVB-T), where a specific known available bandwidth must be shared by several multimedia flows. The developed algorithm has been exploited for smoothing stored video, although it can also be quite easily adapted for real time smoothing. The obtained numerical results, compared with the MVBA, another smoothing algorithm that is already presented and discussed in literature, show the effectiveness of the proposed algorithm, in terms of lost video frames, for different multiplexed scenarios

Priority Traffic Modeling in Multicellular Communication Networks

In this paper we analyze a cellular communication environment which offers specific users priority access to network resources. We foresee a finite number of widespread disparate mobiles moving in a geographical region covered by a finite set of cells. Each user belongs to a class characterized by a specific service, load and mobility profile. In this paper we will consider two classes, namely high priority class and low priority class. The developed analytical network model, validated by simulation experiments, allows us to evaluate the main system performance parameters in terms of new call blocking probability, hand-off blocking probability and forced termination probability

Does the association of therapeutic exercise and supplementation with sucrosomial magnesium improve posture and balance and prevent the risk of new falls?

Background Fracture of the proximal femur is the most feared complication of osteoporosis. Given the numerous physiological functions that magnesium performs in our body, in the literature there is a correlation between osteoporosis and low serum levels of magnesium. Aim Evaluate the incidence of hypomagnesemia in patients with lateral fragility fracture of the proximal femur, the possible correlation between serum magnesium levels and fractures, and the efectiveness of supplementing Sucrosomial® magnesium associated with therapeutic exercise on the outcome of these patients. Methods We divided the study into two parts. In the frst part, we assessed the preoperative incidence of hypomagnesemia in patients using a blood test. In the second part, patients with hypomagnesemia were divided, in the post-operative period, into two groups, who received, respectively, only therapeutic exercise or oral supplementation with sucrosomial magnesium associated with therapeutic exercise. Results Half of the patients with fragility femoral fracture had hypomagnesemia, with a higher incidence of the subclinical form. From the comparison between the two groups, the T1 treatment group showed a signifcant improvement in blood levels of magnesium (2.11±0.15 vs. 1.94±0.11; p<0.05), on the NRS scale (5.7±0.81 vs. 6.6±1.18; p<0.05), the Tinetti scale (17.3±1.15 vs. 15.2±2.98; p<0.05) and the SarQoL questionnaire (47.3±5.21 vs. 44.9±5.54; p<0.05). Conclusions More attention would be needed in the diagnosis and correction of subclinical hypomagnesemia and not just the simple and clinically evident one, including hypomagnesemia among the modifable risk factors for osteoporosis

At the intersection of cultural and natural heritage: Distribution and conservation of the type localities of Italian endemic vascular plants

We conducted a GIS spatial analysis with the aim of providing the first quantitative large-scale overview of the distribution patterns of 1536 type localities (loci classici) of 1216 Italian endemic vascular plants and their relationship with a set of descriptive variables. Whereas some variables were used to model the presence-absence distribution patterns of the type localities for the whole set of endemics as well as for the subset of narrow endemics, others (e.g., presence inside or outside protected areas and Italian Important Plant Areas) were considered with the purpose of assessing potential assets or risks for conservation. The largest number of type localities was found within the Mediterranean biogeographic region (1134), followed by the Alpine region (306) and Continental region (96). A total of 670 locations are located on islands, whereas 866 are located on the Italian mainland (139 and 124 in the case of narrow endemics, respectively). A large number of type localities are located in mountainous areas and along the coastline, which can be seen as a potential risk for conservation. On the contrary, we detected a positive correlation with the distance from roads, which might be considered to be an asset. Importantly, 1030 type localities fall inside protected areas, whereas 506 localities fall outside protected areas, with 259 of these unprotected localities on islands. We propose considering the results of the analysis of the distribution of type localities of Italian endemics to be a strategic tool for conservation planning and resource management. Application of plant micro-reserves and integration of diverse legislation tools are suggested to strengthen efforts and increase conservation success