Optimal component configuration and component routing

Code mobility and mobile agents have received a lot of attention as a paradigm based on which distributed applications can be built. There has been little work however on the mathematical modeling of component mobility. In this direction, we present and analyze three optimization models for component mobility. We are seeking the optimal allocation of components to network nodes and the optimal component routes that will minimize the network traffic that is incurred in the course of component communication. Optimal solutions are found either through a mixed binary integer programming formulation or by employing max flow computations. Complexity results are also reported.     

Periodic attachment in future mobile telecommunications

In mobile telecommunications the network needs to monitor the terminal status, i.e., switched on, switched off, busy, idle. Once a mobile terminal is switched on, it automatically informs the network accordingly (attachment action). Regarding the way that the network identifies that a terminal is switched off (detachment), a procedure called periodic attachment is proposed: the terminal (when switched on) periodically reports to the network its active status. If the network detects silence for more than an agreed time period it considers the terminal switched off. Paging signalling savings can be achieved if the network is informed early that a mobile terminal is switched off. However, periodic attachment requires access to the network database system, which might cause a bottleneck. In this paper the performance characteristics of periodic attachment and the induced signalling load are evaluated as influenced by the selection of the time-out period. A constant time-out period for the whole day can cause a large amount of database transactions especially during low traffic hours. A method for dynamic time-out period selection to fit the varying conditions during the day is proposed and evaluated     

Investigation of the Equivalence of National Dew-Point Temperature Realizations in the ?50?°C to +?20?°C Range

In the field of humidity quantities, the first CIPM key comparison, CCT-K6 is at its end. The corresponding European regional key comparison, EUROMET.T-K6, was completed in early 2008, about 4?years after the starting initial measurements in the project. In total, 24 NMIs from different countries took part in the comparison. This number includes 22 EURAMET countries, and Russia and South Africa. The comparison covered the dew-point temperature range from ?50?°C to +20?°C. It was carried out in three parallel loops, each with two chilled mirror hygrometers as transfer standards in each loop. The comparison scheme was designed to ensure high quality results with evenly spread workload for the participants. It is shown that the standard uncertainty due to the long-term instability was smaller than 0.008?°C in all loops. The standard uncertainties due to links between the loops were found to be smaller than 0.025?°C at ?50?°C and 0.010?°C elsewhere. Conclusions on the equivalence of the dew-point temperature standards are drawn on the basis of calculated bilateral degrees of equivalence and deviations from the EURAMET comparison reference values (ERV). Taking into account 16 different primary dew-point realizations and 8 secondary realizations, the results demonstrate the equivalence of a large number of laboratories at an uncertainty level that is better than achieved in other multilateral comparisons so far in the humidity field.     

Reconfiguration of carrier assignment in cellular networks

We consider the problem of updating nominal carrier assignments in cellular networks, which dymamically operate with channel borrowing and reassignments, to match the timevarying offered traffic demands encountered on these systems. Assuming an existing assignment of nominal carriers and the new requirements in each cell, we formulate the problem of obtaining a new assignment such that the number of carriers required to meet the total traffic demand as well as the number of different assignments between the old and the new allocation are minimized. We introduce two approaches to obtain this new assignment. One approach treats the two objectives independently and is applicable to problems with cochannel interference constraints only. This approach produces a new assignment optimized with respect to the first goal, and then rearranges the frequencies of this new allocation so that the number of different assignments with respect to the previous allocation is minimum. A second approach aims at satisfying both goals at the same time and is applicable to problems with any type of interference constraints. The main advantage of this approach is the introduction of a single window parameter which can control the assignments produced, by favoring one goal at the expense of the other. We study several transition scenarios in macrocellular and microcellular environments, and show that in the majority of cases these objectives are conflicting, and that reconfiguration strongly depends on the amount of change of the traffic requirements.     

Reconfiguration models and algorithms for stateful interactiveprocesses

We present new results in the area of reconfiguration of stateful interactive processes in the presence of faults. More precisely, we consider a set of servers/processes that have the same functionality, i.e., are able to perform the same tasks and provide the same set of services to their clients. In the case when several of them turn out to be faulty, we want to reconfigure the system so that the clients of the faulty servers/processes are served by some other, fault-free, servers of the system in a way that is transparent to all the system clients. We propose a novel method for reconfiguring in the presence of faults: compensation paths. Compensation paths are an efficient way of shifting spare resources from where they are available to where they are needed. We also present optimal and suboptimal simple reconfiguration algorithms of low polynomial time complexity O(nmlog(n²/m)) for the optimal and O(m) for the suboptimal algorithms, where n is the number of processes and m is the number of primary-backup relationships. The optimal algorithms compute the way to reconfigure the system whenever the reconfiguration is possible. The suboptimal algorithms may sometimes fail to reconfigure the system, although reconfiguration would be possible by using the optimal centralized algorithms. However, suboptimal algorithms have other competitive advantages over the centralized optimal algorithms with regard to time complexity and communication overhead     

Intercomparison of the Realizations of the ITS-90 from 83.8058 K to 692.677 K among European NMIs

The EUROMET.T-K3 comparison is the regional extension of CCT-K3. The comparison involved the six European national metrology institutes (NMIs) previously involved in CCT-K3 (LNE-INM/CNAM, SMU, INRiM, NMi-VSL, NPL, PTB) and 18 additional European national laboratories. The comparison was divided into five different loops, each coordinated by a co-pilot chosen from the laboratories having participated in the CCT-K3 comparison. LNE-INM/CNAM played the role of pilot in linking the five loops. In each loop, an artifact in the form of a standard platinum resistance thermometer (SPRT, 25 Ω) was circulated among the participating laboratories. To have sufficient information about the possible drift of the SPRTs, the co-pilots performed a calibration over the full temperature range at the beginning and at the end of the loop. A EUROMET reference value (ERV), taking into account the whole comparison, was defined, and the differences (T _Lab − T _ERV) were calculated with the associated uncertainties. The method for establishing the link between the participants in CCT-K3 and in EUROMET.T-K3 is described. Institut National de Métrologie (BNM-INM/CNAM at the time of the comparison, LNE-INM/CNAM since 1 January 2005), Paris, France.     

Development of a multiple linear regression model for predicting the 28-day compressive strength of Portland pozzolan cement

A multiple linear regression model was developed for the prediction of the 28-day compressive strength of Portland Pozzolan Cement (PPC) containing Santorin Earth as an admixture. The independent variables of the model were: (1) the compressive strength at the age of 2 days, (2) the compressive strength after autoclave hydrothermal treatment at 2.07 N/mm² (300 psi) and 214°C for 3 h, (3) the C₃S/C₂S ratio of the clinker, (4) the insoluble residue of the cement, (5) the pozzolanic activity factor and (6) the C₃A content of the clinker. The evaluation of the proposed model was performed by various statistical tests, all of which were successful. These tests included: multiple correlation, test of the significance of coefficients (t-test), estimation of confidence intervals for coefficients, test for outliers and unusual residuals, test for influential points, conditional sums of squares, R-squared and analysis of variance. There was very good agreement between the strength predicted by the multiple regression model and experimental results.

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Résumé Un modèle de régression multiple linéaire a été developpé pour la prédiction de la résistance en compression du ciment pozzolanique Portland, contenant de la Terre de Santorin comme mélange. Les variables indépendantes du modèle étaient: (1) la résistance en compression pour l’age de 2 jours, (2) la résistance en compression après un traitement de 3 heures dans un autoclave à 2,07 N/mm² (300 psi) et 214°C, (3) le rapport C₂S/C₂S du clinker, (4) la quantité d’insolubles du ciment, (5) le facteur d’activité pozzolanique et (6) la quantité de C₃A du clinker. L’évaluation du modèle proposé à été effectuée par une série d’essais statistiques: une corrélation multiple, un essai de signification des coefficients (t-test), estimation des intervalles de confiance pour les coefficients, essai pour les substances étrangères et les résidus inhabituels, essai pour les points d’influence, somme des moindres carrés conditionnels, carré et une analyse de variance. Un très bon accord entre la résistance prévue par le modèle de régression et les résultats expérimentaux, a été constaté.

     

Bone tissue response to titanium implant surfaces modified with carboxylate and sulfonate groups

The present study assessed in vivo new bone formation around titanium alloy implants chemically grafted with macromolecules bearing ionic sulfonate and/or carboxylate groups. Unmodified and grafted Ti–6Al–4V exhibiting either 100% carboxylate, or 100% sulfonate, or both carboxylate and sulfonate groups in the percent of 50/50 and 80/20 were bilaterally implanted into rabbit femoral condyle. Neither toxicity nor inflammation were observed for all implants tested. After 4 weeks, peri-implant new bone formation varied as a function of the chemical composition of the titanium surfaces. The percent bone-implant contact (BIC) was the lowest (13.4 ± 6.3%) for the implants modified with grafted carboxylate only. The value of BIC on the implants with 20% sulfonate (24.6 ± 5.2%) was significantly (P < 0.05) lower than that observed on 100% sulfonate (38.2 ± 13.2%) surfaces. After both 4 and 12 weeks post-implantation, the BIC value for implants with more than 50% sulfonate was similar to that obtained with the unmodified Ti–6Al–4V. The grafted titanium alloy exhibiting either 100% sulfonate or carboxylate and sulfonate (50% each) groups promoted bone formation. Such materials are of clinical interest because, they do not promote bacteria adhesion but, they support new bone formation, a condition which can lead to osseointegration of bone implants while preventing peri-implant infections.