Semantics of Protocol Modules Composition and Interaction

This paper studies the semantics of protocol modules composition and interaction in configurable communication systems. We present a semantic model describing Cactus and Appia -- two frameworks that are used for implementing modular systems. The model covers protocol graph, session and channel creation, and inter-module communication of events and messages. To build the model, we defined a source-code-validated specification of a large fragment of the programming interface provided by the frameworks; we developed an operational semantics describing the behaviour of the operations through state transitions, making explicit interactions between modules. Developing the model and a small example implementing a configurable multicast helped us to better understand the design choices in these frameworks. The work reported in this paper is our first step towards reasoning about systems composed from collections of modules

Hip fracture prognosis: could bioimpedance be an alternative to conventional nutritional assessment?

Background: Risk-factors for mortality in hip fractures encompass nutritional status, nominally body mass index, but not body composition. Given the difficulty of anthropometric assessment in bedridden patients a prospective study with bioimpedance analysis was designed. Methods: Elderly patients with hip fracture were consecutively recruited. Biochemical tests, primitive bioimpedance measurements (resistance, reactance and phase angle) and follow-up till one year were targeted. Results: Patients (N = 69, 81.2 +/- 8.1 years old, 72.5% females) stayed in the hospital for 15.5 +/- 17.1 days, and 18.8 %(13/69) required further hospitalization during the ensuing months. Mortality was 11.6% within 30 days, coinciding with hospital mortality, and an additional 11.6% till one year, thus reaching 23.2%. Anemia, hypoalbuminemia and low transferrin, along with elevated glucose and urea were frequent, suggesting undernutrition with metabolic derangements. Reactance, urea and creatinine were different in patients suffering both early and late demise. Resistance, white blood cell count and osteoporosis were risk factors for early mortality only, and anemia exclusively for late mortality. Conclusions: Primitive bioimpedance measurements, which had not been hitherto investigated, were prognostically related to early and late mortality. These markers of disease-related malnutrition and especially reactance should be further studied in patients unfit for anthropometric evaluation due to fracture and immobility

Integration of phase change materials in building structures

Disertační práce se zabývá integrací materiálů s fázovou změnou do stavebních konstrukcí. Základním požadavkem je zlepšení tepelné stability v letním období bez využití klimatizačních zařízení. Toho je možné dosáhnout zvýšením tepelně akumulační kapacity stavebních konstrukcí objektu. Jestliže nelze zvýšit akumulační kapacitu v rovině hmotnostní, je možné využít materiály s fázovou změnou. Ty jsou schopny akumulovat latentní teplo a tím zvýšit tepelně akumulační kapacitu objektu. V rámci zpracování disertační práce byly materiály s fázovou změnou zkoumány v termickém inkubátoru, termickou analýzou a především ve full-scale experimentech při komparativním měření. Pro komparativní měření byly využity podkrovní místnosti na Fakultě stavební v Brně, kde jedna funguje jako referenční a druhá jako experimentální. Do té byly instalovány vyrobené tepelně akumulační panely. Ty jsou složeny z nosné desky, na které jsou umístěny kapilární rohože, které jsou omítnuty modifikovanou omítkou. Sádrová omítka je modifikována mikrokapslovaným parafínem ke zlepšení tepelně akumulační kapacity. Tento systém je napojen na tepelné čerpadlo vzduch-voda, čímž je možné akumulační panely dochlazovat nebo dohřívat. V experimentálních měřeních byly zkoumány různé režimy provozu a byl vyhodnocován jejich vliv na vnitřní mikroklima. Akumulace tepla v PCMs tlumí teplotní amplitudu v budově během letního období a zároveň umožňuje odvod akumulovaného tepla přesunout do nočních hodin. Časový interval, kdy je elektrická energie ze sítě odebírána, je nepoměrně kratší než u klimatizace. Konvenční klimatizační zařízení musí pracovat souběžně s působením tepelné zátěže, tzn. v době špičkového odběru elektrické energie. Instalovaný systém dokáže díky nastaveným režimům reagovat na venkovní tepelné podmínky. Nelze však udržet vnitřní teplotu v místnosti na konstantní teplotní hladině, ale lze redukovat denní maxima a udržet teplotu v místnosti v teplotním rozsahu požadovaném legislativou. Zjištěné výslThe thesis deals with the integration of phase change materials (PCMs) into building structures. The basic requirement is improved thermal stability during the summer season without using an air conditioner. This can be achieved by increasing the thermal storage capacity of the building structures. If the thermal capacity cannot be increased on the level of weight, phase change materials can be used. These materials are capable of storing latent heat and thus increasing the thermal storage capacity of the building. In the thesis the phase change materials were investigated in a thermal incubator by thermal analysis and, above all, in full-scale experiments using comparative measurements. The comparative measurements were carried out in two attic rooms at the Faculty of Civil Engineering, Brno University of Technology, where in one was used as a reference and the other for the experiment. Manufactured heat storage panels were installed in the experimental room. These panels are composed of a base plate; the capillary tubes placed on it are coated with modified plaster. The gypsum plaster is modified with micro-capsules paraffin for improving the thermal storage capacity. This system is connected to a thermal air-water pump, by which the storage panels can be additionally cooled or heated. In the experimental measurements, different operating modes were investigated and their effect on the indoor environment was evaluated. Thermal storage in PCMs dampens the temperature amplitude in the building during the summer season and, at the same time, allows the stored heat to be discharged during the night. Moreover, the time interval of withdrawing electric energy from the supply mains is much shorter than in the case of air conditioning. A conventional air conditioner must operate simultaneously with the thermal load, i.e. at the time of peak consumption of electric energy. Thanks to the set regimes, the installed system is capable of responding to external thermal condit

A framework for formalization and strictness analysis of simulation event orderings

10.1177/0037549705054930Simulation814325-335SIMU

Distributed agreement and its relation with error-correcting codes

Abstract. The condition based approach identifies sets of input vectors, called conditions, for which it is possible to design a protocol solving a distributed problem despite process crashes. This paper investigates three related agreement problems, namely consensus, interactive consistency, and k-set agreement, in the context of the condition-based approach. In consensus, processes have to agree on one of the proposed values; in interactive consistency, they have to agree on the vector of proposed values; in k-set agreement, each process decides on one of the proposed values, and at most k different values can be decided on. For both consensus and interactive consistency, a direct correlation between these problems and error correcting codes is established. In particular, crash failures in distributed agreement problems correspond to erasure failures in error correcting codes, and Byzantine and value domain faults correspond to corruption errors. It is also shown that less restrictive codes can be used to solve k-set agreement, but without a necessity proof, which is still an open problem

Multimedia Transport Protocol And Multicast Communication

The emerging of high speed networks provides the infrastructure for handling a wide set of new applications, covering distributed multimedia cooperative features. In this framework, multipeer communication is a major service/protocol issue because most of these applications exhibit the need for such a functionality. Besides many functions and mechanisms, the semantics of transport layer multicast conversation has to be defined. We show that a new service semantic called statistical-reliable, in which the reliability is enforced when desired by applications, is of major interest for the high-performance networking paradigm. This new reliability semantic can be implemented using a protocol akin to the XTP bucket algorithm. The interest of the developed protocol is that 1) it can perform efficiently on top of wide area (for instance ATM-based) networks as well as LANs, 2) it provides a continuous reliability service from best-effort to all-reliable as a function of the application require..

PolyCert: Polymorphic Self-optimizing Replication for In-Memory Transactional Grids

Part 6: Replication and CachingInternational audienceIn-memory NoSQL transactional data grids are emerging as an attractive alternative to conventional relational distributed databases. In these platforms, replication plays a role of paramount importance, as it represents the key mechanism to ensure data durability. In this work we focus on Atomic Broadcast (AB) based certification replication schemes, which have recently emerged as a much more scalable alternative to classical replication protocols based on active replication or atomic commit protocols. We first show that, among the existing AB-based certification protocols, no “one-fits-all” solution exists that achieves optimal performance in presence of heterogeneous workloads. Next, we present PolyCert, a polymorphic certification protocol that allows for the concurrent coexistence of different certification protocols, relying on machine-learning techniques to determine the optimal certification scheme on a per transaction basis. We design and evaluate two alternative oracles, based on parameter-free machine learning techniques that rely both on off-line and on-line training approaches. Our experimental results demonstrate the effectiveness of the proposed approach, highlighting that PolyCert is capable of achieving a performance extremely close to that of an optimal non-adaptive certification protocol in presence of non heterogeneous workloads, and significantly outperform any non-adaptive protocol when used with realistic, complex applications that generate heterogeneous workloads