On the Energy Efficiency of Networked Systems

Energy is a first-class resource for datacenter operators since its cost is the biggest limiting factor in scaling a large computing facility. The solution embraced by major operators is to build their facilities in strategic geographical locations and to abandon expensive specialized hardware for cheap commodity systems. However, such systems are not efficient when it comes to energy and a considerable amount of research effort has been put in finding a solution to this problem. Furthermore, the need for more programmable and flexible networking devices is pushing the need for hardware commoditization also within the datacenter network. In this thesis we propose two solutions aimed at improving the overall energy efficiency of a datacenter facility. The first address efficiency in computing, by proposing a different hardware architecture for server systems. We propose a hybrid architecture that blends traditional server processors with very-low-power processors from the mobile devices world. The second solution envisions the usage of current server platforms as network switches or routers and provides guidelines for the implementation of power saving algorithms that do not affect peak performance while saving up to 50% power. This work is based on both theoretical modeling and simulation and experimentation with real-world prototypes

Last-Meter Smart Grid Embedded in an Internet-of-Things Platform

The customer domain of the smart grid natu- rally blends with smart home and smart building systems, but typical proposed approaches are “distributor-centric” rather than “customer-centric,” undermining user acceptance, and are often poorly scalable. To solve this problem, we propose a detailed architecture and an implementation of a “last-meter” smart grid—the portion of the smart grid on customer premises—embedded in an internet-of-things (IoT) platform. Our approach has four aspects of novelty and advantages with respect to the state of the art: 1) seamless integration of smart grid with smart home applications in the same infrastructure; 2) data gathering from heterogeneous sensor communication protocols; 3) secure and customized data access; and 4) univocal sensor and actuator mapping to a common abstraction layer on which additional concurrent applications can be built. A demonstrator has been built and tested with purposely-developed ZigBee smart meters and gateways, a distributed IoT server, and a flexible user interface

Subclassification of the “Grey Zone” of Thyroid Cytology; A Retrospective Descriptive Study with Clinical, Cytological, and Histological Correlation

Undetermined thyroid cytology precludes any definitive distinction between malignant and benign lesions. Recently several classifications have been proposed to split this category into two or more cytological subcategories related to different malignancy risk rates. The current study was performed retrospectively to investigate the results obtained separating “undetermined” cytologic reports into two categories: “follicular lesion” (FL) and “atypia of undetermined significance” (AUS). Biochemical, clinical, and echographic features of each category were also retrospectively analyzed. Altogether, 316 undetermined fine-needle aspirated cytologies (FNACs) were reclassified as 74 FL and 242 AUS. Histological control leads to a diagnosis of carcinomas, adenomas, and nonneoplastic lesions, respectively, in 42.2%, 20%, and 37.8% of AUS and in 8.3%, 69.4%, and 22.2% of FL. Among biochemical, clinical, cytological, and echographic outcomes, altered thyroid autoantibodies, multiple versus single nodule, AUS versus FL, and presence of intranodular vascular flow were statistically significant to differentiate adenoma from carcinoma and from nonneoplastic lesions, whereas no significant differences were found between carcinomas and nonneoplastic lesions for these parameters. The results of this retrospective study show that undetermined FNAC category can further be subclassified in AUS and FL, the former showing higher malignancy rate. Further prospective studies are needed to confirm our results

Metronome: adaptive and precise intermittent packet retrieval in DPDK

DPDK (Data Plane Development Kit) is arguably today's most employed framework for software packet processing. Its impressive performance however comes at the cost of precious CPU resources, dedicated to continuously poll the NICs. To face this issue, this paper presents Metronome, an approach devised to replace the continuous DPDK polling with a sleep&wake intermittent mode. Metronome revolves around two main innovations. First, we design a microseconds time-scale sleep function, named hr_sleep(), which outperforms Linux' nanosleep() of more than one order of magnitude in terms of precision when running threads with common time-sharing priorities. Then, we design, model, and assess an efficient multi-thread operation which guarantees service continuity and improved robustness against preemptive thread executions, like in common CPU-sharing scenarios, meanwhile providing controlled latency and high polling efficiency by dynamically adapting to the measured traffic load

Propagazione di difetti nei laminati fibrometallici e modellazione FEM

I laminati fibrometallici esibiscono elevate resistenze a fatica, fondamentali in campo aeronautico. Scopo del presente lavoro è modellare con software agli elementi finiti dei provini su cui sono state condotte prove di fatica, confrontando i risultati ottenuti. Il modello FEM è stato poi impiegato per calcolare il fattore di intensificazione degli sforzi all'apice della cricca di pannelli fessurati

Studio delle comunità microbiche associate a colture di Acartia tonsa (Copepoda, Calanoida) e coinvolte nella degradazione del poli(butilene succinato-co-butilene adipato) (PBSA)

Acartia tonsa is a crustacean belonging to the subclass Copepoda, order Calanoida, which feeds mainly on phytoplankton through filtration of the water column. The feeding strategy facilitates the continuous turnover of macro- and micronutrients, promoting bacterial colonization, therefore, Acartia tonsa represents a microbial hotspot. At the end of the life cycle, the bacterial communities associated with carcasses of this species show lipase, protease, and chitinase activities involved in the degradation of high molecular weight macromolecules, recalcitrants to biodegradation. These enzymes might find application in the degradation of biopolymers, interesting in this thesis, in particular poly(butylene succinate-co-butylene adipate) (PBSA), a bio-based polyester suggested as an alternative to petroleum-derived plastics, specifically, for the production of nets to support the replanting of Posidonia oceanica. In this thesis, microbial communities associated with the culture of the copepod A. tonsa, reared under controlled conditions, and fed with a monoalgal diet of Rhinomonas reticulata, were characterized. A culture-independent approach was adopted by means of 16S rDNA metabarcoding accompanied by a predictive functional metagenomics study with a particular interest in the Carboxylic-ester hydrolases activities involved in PBSA degradation. In detail, the carboxylesterase, triacylglycerol lipase and cutinase activities were investigated, providing a taxonomic and functional profile of the bacterial communities investigated. especially in the carboxylesterase, triacylglycerol lipase activities and cutinase, Attention regarded bacterial communities associated with individuals that had just reached the adult stage and those that had reached it after 7 days. In addition, bacterial communities associated with carcasses of newly formed dead individuals and after 4 and 33 days, were considered. Bacterial communities associated with carcasses differ from those associated with the alive, adult copepod A.tonsa. In particular, the data obtained suggest that the differences increase with time, in fact, the carcasses at 33 days differ significantly in taxonomic and functional terms from the bacterial communities associated with adult organisms and from recently formed carcasses. The bacterial communities associated with the copepod carcasses offer a greater contribution to the carboxyl-ester hydrolase activities and this contribution shows an important equidistribution among the bacterial taxa that characterize the carcasses formed from 33 days, not necessarily the most represented ones. A culture-dependent approach was also adopted for the isolation of microorganisms by the debris derived from dead cultures of A. tonsa. The main interest was isolating bacterial and fungal candidates that employ hydrolytic enzymatic activities involved in the degradation of PBSA. Eleven bacterial morphotypes and four fungal morphotypes were isolated and selected for their ability to use PBSA as the only carbon source. One of the bacterial morphotypes has been characterized by the genus Vibrio sp. which carries out extracellular carboxyl-ester hydrolase and lipase activities, promoting the reduction of the number of PBSA surface ester bonds. Vibrio sp. also catalyzed hydrolysis in the crystalline regions of polyester which are generally less accessible to enzymatic activities. One of the fungal morphotypes has been characterized by the genus Cladosporium sp. which perform carboxyl-ester hydrolase and lipase activities, promoting the reduction of the number of PBSA surface ester bonds and catalyzing hydrolysis of not accessible crystalline regions and more accessible amorphous region of polymers. Acartia tonsa represents a nursery of microorganisms of interest for the degradation of complex macromolecules, with possible implications for the design of processes dedicated to the transformation of recalcitrants to biodegradation, in both marine and anthropogenic environments. The latter being considered as the complex bio-based industrial processes for the transformation of recalcitrants in the environment. Of particular interest is the composting of biopolymers in the treatment of organic wastes or accelerating the biodegradation of biopolymers with potential applications in marine environment. In perspective, the further identification of fungal and bacterial morphotypes coupled with the sequencing of their genomes will allow identifying metabolic pathways potentially involved in the degradation of biopolymers, and their regulation to design innovative bio-based processes of interest for human activities in marine environment. Thus, new Culture dependent approaches will be designed for the isolation of bacterial and fungal taxa capable of PBSA degradation and other biopolymers with applications in marine environment

Energy efficient scheduling of VoIP traffic in IEEE 802.16 wireless networks

WiMAX is the industry name given to the IEEE 802.16 standard, which provides fixed and mobile broadband wireless access in metropolitan areas. In spite of the growing popularity of data services, voice services still remain the most requested, especially when mobility is concerned. Mobile terminals are typically powered by rechargeable batteries with limited ca-pacity, hence the necessity to develop efficient power-saving mechanisms to im-prove the life span of the terminals. The contribution of the present study is twofold. First, we design an energy-efficient scheduler for IEEE 802.16 connections using the enhanced real-time poll-ing service (ertPS) scheduling service, which is mostly intended for Voice over IP (VoIP) services. Then, we provide a detailed investigation of the performance of our contributed algorithm in terms of power saving and application metrics. The results show that the proposed algorithm is best fit to be used for VoIP traffic, rather than UGS and rtPS and that QoS requirements can be achieved even when a large amount of energy is saved

Building a power-proportional software router

We aim at improving the power efficiency of network routers without compromising their performance. Using server-based software routers as our prototyping vehicle, we investigate the design of a router that consumes power in proportion to the rate of incoming traffic. We start with an empirical study of power consumption in current software routers, decomposing the total power consumption into its component causes. Informed by this analysis, we develop software mechanisms that exploit the underlying hardware’s power management features for more energy-efficient packet processing. We incorporate these mechanisms into Click and demonstrate a router that matches the peak performance of the original (unmodified) router while consuming up to half the power at low loads, with negligible impact on the packet forwarding latency

Fault-tolerant streaming computation with BlockMon

As the amount of data being exchanged over the network increases, algorithms originally implemented for running on a single machine have been re-designed to work in a distributed manner, with a processing platform that splits tasks among machines and cores. Brand new frameworks have emerged for the analysis of unbound streams of data, aiming at processing data and retrieving information nearly real-time by using clusters of machines. Node failure and recovery are crucial issues related to distributed systems, especially when using commodity hardware and when continuously processing data coming real- time into the system. In this paper we present the performance of the distributed stream-processing platform Blockmon, with the novel fault-tolerant mechanism that we implement on top, and compare it against Spark, the state-of-the art in terms of fault-tolerant stream-processing platform. Our experimental results suggest that Blockmon performs around two times faster than Spark, with a twenty times reduced memory footprint, showing the feasibility of using Blockmon on popular energy- efficient architectures such as the ARM ones