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Design of supports for high performance optimistic simulations with special focus on multi-core hosting environments
No full textParallel Discrete Event Simulation (PDES) is a classical means to achieve high performance simulations. This is especially important on contexts entailing real-time constraints, as for the case of decision making tools, where target configurations have to be identified, via simulation, within bounded time. PDES is based on splitting the model to simulate in different simulation objects, that are mapped onto logical processes (LPs), which can process simulation events in parallel, thus potentially allowing for (large) speedups when compared to traditional serial execution of the simulation model. On the other hand, synchronization mechanisms need to be actuated in order to allow the parallel run to provide correct results, hence correct evolution of the objects’ state along the simulation time axis.
In this dissertation we cope with performance of PDES systems, with special focus on deploys of the PDES platforms onto multi-core architectures. These architectures represent the current CPU trend and nowadays it is common to have chips with a significant number of cores, sometimes enough for effectively performing parallel computations within a single chip. By design, these architectures share most of the CPU internal components across different cores, and physical memory across the different CPUs. This implies several drawbacks, mainly due to the contention, but at the same time, such a sharing can become a resource, if well exploited through sector specific software design.
The base building block for our work is the optimistic PDES synchronization paradigm, which has been shown to be highly promising in terms of potential for fruitful parallelism exploitation.
As a first contribution, we will present the design and implementation of optimized supports for state log/restore operations, which are at the base of the rollback procedures used to guarantee consistency in the optimistic paradigm. System requirements for these supports only entail the x86 instruction set, with no particular additional facilities to be offered by the underlying computing platform. On the other hand, the provided solution has a further reflection on performance for deploys on multi-core systems since it aims at automatizing the optimization of a set of CPU/memory tradeoffs among which we also find virtual memory usage, which may impact physical memory (e.g. cache) contention for the case of multi-core architectures.
Secondly, we address the issue of optimizing the behavior of the caching hierarchy by providing an innovative buffer delivery mechanism suited for memory demands in optimistic PDES systems. This is a quite relevant aspect to cope with, given the intrinsic high-demand of virtual memory by optimistic PDES runs. The proposed solution tends to reduce the impact of virtual memory demand on physical memory, which is achieved in a highly general manner, thus making the approach applicable to differentiated types of hardware architectures. However, by nature, it reveals particularly suited for the case of multi-core systems, given the aforementioned issue if physical memory contention across the cores.
Finally, we provide an additional contribution, specifically tailored to the multi-core architecture, which introduces an innovative load-sharing paradigm for optimistic PDES platforms. It is aimed at improving performance and fruitful resource usage in a fully orthogonal manner with respect to traditional load-balancing. In fact, it allows the computing resources to be (dynamically) assigned to each simulation platform instance on the basis of its current workload, instead of migrating the workload from one kernel to another. This also has the advantage of not suffering from all the issues related to workload (namely LPs) remapping (i.e. data and metadata migration), leading to the simplification of the job of both application programmers and simulation-system developers.
To assess the real benefits, all the above approaches have been implemented within ROOT-Sim, an open source C-based Optimistic Simulation platform targeting the optimistic synchronization paradigm, and several experimental studies have been conducted, whose outcomes are reported in the thesis
CONDITIONAL MOMENT CLOSURE FOR LES OF COMPRESSIBLE TURBULENT REACTIVE FLOWS
No full textWhile the Conditional Moment Closure (CMC) method has been de- veloped with reference to low Mach number flows, the formulations considered in this thesis work avoid taking any simplification on the acoustics, so as to pursue a fully compressible formulation. Two cou- pling strategies for a LES formulation of fully compressible reactive flows adopting the CMC method are presented.
Similarly to standard CMC approaches, both strategies rely on re- casting the full Navier-Stokes system into two sub-systems, the first filtered and solved by means of LES in the physical space, the other conditionally filtered and solved in the CMC space.
The two approaches differ by the way the two sub-systems are cou- pled. In the first coupling strategy, referred to as ”Vector Field Up- date” (VFU), the CMC interacts with the LES sub-system by actually modifying the density and sensible energy LES fields. In the second coupling strategy, referred to as ”Energy Source Update” (ESU), the source term in the LES energy equation is computed on the basis of the species source terms obtained by the time integration of the CMC system. This way, the CMC interaction with the LES sub-system re- lies on the modification of the LES energy source term, while any LES state variable is directly modified.
The numerical implementation of the LES/CMC equations for both coupling strategies has been carried out and explained in detail. The LES flow solver relies on central two-to-six order discretization of the convective terms of the Navier-Stokes equations cast in fully split form, leading to a locally conservative formulation which guarantees discrete conservation of the total kinetic (mechanical) energy. This approach allows a stable and accurate spatial discretization of the convective terms without the addition of numerical dissipation.The conditionally filtered CMC subsystem is discretized on a Carte- sian mesh in the CMC space, and the time advance is based on a further splitting in time between an explicit treatment of the convec- tive operator and an implicit treatment (using BDF, as in CVODE) of the fully coupled reactive-diffusive operators.
The predictive capabilities of a zero-dimensional version of the CMC code are presented. The solution sensitivity to scalar dissipations is tested varying its strength and shape. An a-priori prediction of the SANDIA-D flame has been performed, and the comparison with ex- perimental results is presented. The VFU and ESU CMC-LES cou- pling strategies are compared by means of 2D test case, and the differ- ences are discussed. The scalability performance, and the preliminary results of a 3D version of the code are presented
Thermal noise issue in the monolithic suspensions of the Virgo+ gravitational wave interferometer
No full textFrom quality factor measurements we can estimate thermal noise using an
analytical or numerical model of the physical system and dissipative processes.
Moreover, for some resonances, we know the loss mechanisms and the regions where
there is the larger deformation during the vibrational motion. In that case, the
knowledge of quality factors allows us to understand if there is a further damping
process acting on a system component and, when required, to modify its technical
design and realization. This is mandatory to correctly design and realize a low-dissipative suspension for a gravitational wave interferometer
study on virological and immunological factors involved in determining the course of HPV anogenital infection
No full textInfection by high-risk HPV types is necessary but not sufficient for
progression to cancer. In fact, the majority of HPV infections do not lead to
cytological anomalies or cancer but only a small percentage (10-15%)
persist and promote the development of low and high-grade lesions.
It is known that to persist HPV must escape the host immune system and
persistence could be due to an impaired IFN-system activation in the
infected individual.
In literature, most studies were conducted in cell lines with constitutively
oncogenes expression, whereas in vivo, the majority of HPV infections that
resolve with time have a transient oncogene expression. To clarify the role
of innate immune response, we analysed, for the first time, the expression of
several TLRs (TLR2, TLR3, TLR4, TLR7 and TLR9), the IFN lambda
pathways (INF-lambda 1, INF-lambda II, the IFN-lambda receptors), and
the activation of several IFN induced genes (ISG15, MxA and p56) in HPV
positive and negative cervical cells from 154 patients.
The expression levels of TLR2, TLR3, TLR4 and TLR7 resulted highly
variable both in HPV negative and in HPV positive patients.
Differently, TLR9 was activated at different levels during HPV infection,
with a tendency to be higher in LR-HPV infected women and significantly
higher in patients with HPV persistent infection.
Furthermore, we correlated TLRs expression with histological grade of
lesions; TLR7 and TLR9 increased with the histopathological grade, but
TLR9 in patients with persistent HPV infection was greater then in patients
with CIN II or worse lesion, independently of lesions grade
We hypothesize that the inability to clear HPV DNA after one year could be
a risk factor to later develop high-grade lesions due to the persistence of the
virus and the high levels of TLR9.
IFN lambda 1 was expressed at higher level in patients with LR HPV
infection compared to HR HPV and negative and we observed the same
trend for IFN lambda 2/3. The elevated expression level of IL28R in
patients with LR HPV infection respect to the other study groups confirmed
the data obtained with IFN-lambda
A Fabry-Perot interferometer for ground-based millimetric spectroscopy
No full textAstrophysical observations at millimeter and sub-millimeter wavelengths are one of
the most useful tools to understand the history of the Universe. Although ground-based observations are affected by the presence of the Earth atmosphere, space telescopes remain limited in size offering only modest angular resolution not suitable to detect small spatial features of so compact objects. To date the ground-based solution seems to be the only feasible way to perform high angular resolution deep sky surveys. In this context a Fabry-Perot Interferometer (FPI) has been developed in order to improve the capabilities of MAD (Multi Array of Detectors), a 4-channel photometer optimized for multi-frequency observation of Sunyaev-Zel’dovich effect that will operate at Millimetre and Infrared Testagrigia Observatory (MITO), a 2.6-m in diameter telescope located in the Alps in Val d’Aosta (3480 m a.s.l.). The transmission response of an innovative system composed of two resonant metal grids in a FPI configuration is explored.
A semi-empirical approach to perform an analysis of atmospheric transmission and emission at Dome C (Antartic Plateau) is suggested.
The spectrometer CASPER2 (Concordia Atmospheric SPectroscopy of Emitted Ra-
diation - MITO version) has been developed specifically to record atmospheric spectra assisting cosmological observations with the 2.6-m in diameter Cassegrain telescope at MITO
“La malattia emorroidaria recidiva post-prolassectomia: ipotesi su fattori predittivi e strategia chirurgica”
No full textINTRODUCTION
The surgical procedure of stapled haemorrhoidopexy is now considered safe and its safety is improving with experience and technical upgrading. Compared to conventional procedures, stapled haemorrhoidopexy has the advantage - in the short term results - of less postoperative pain but the main disadvantage - in the long term follow-up- of possible recurrent prolapse.
This occurs between three months and one year after the operation and should be differentiated -for a more correct evaluation of the results- by the persistent prolapse, that is immediately evident after surgery or in the first two months. Both –persistent and recurrent prolapse- required treatment if symptomatic.
The percentage of symptomatic prolapse -persistent and recurrent- after stapled procedures varies widely in the several clinical trials described in the literature, ranging from a minimum of 2% to the worst results of 53.3% (1-9). The unsatisfactory results mainly depend on incorrect indications (IV grade haemorrhoids with predominant external, fibrous component), technical mistakes during surgical procedure and insufficient prolapse correction.
Avoiding or minimizing the possibility of a recurrent prolapse should be demanded to a well realized primary operation, calibrated on the effective amount of the prolapse (using single or double stapled technique, instruments with larger case, parachute technique, or with an immediate, intraoperative correction of the persistent prolapse or excision of a residual pile).
The aim of this work is to analyze the different features of recurrences after stapled haemorrhoidal operations and the procedures realized to treat them in order to lay down solid and firm starting points to focalize some guidelines of treatment of recurrences after stapled prolapsectomy
MATERIAL AND METHODS
We performed a retrospective study on 69 patients, affected by recurrent or residual prolapse after a primary operation of stapled haemorrhoidopexy (58 patients treated with a single PPH -PPH- and 11 with a double stapling procedure -DSPPH-) and undergoing reoperative surgery for the treatment of recurrence (Table I). This cohort of patients was recruited between January 2005 and January 2011 in three Italian national reference centers for proctological surgery (Pisa, Rome and Pordenone) and was retrospectively analyzed.
RESULTS
The symptoms of primary onset had been: haemorrhoidal crisis in 17 patients, bleeding in 5 patients, prolapse in 45 patients and finally both prolapse and bleeding in 2 patients. (Table 2)
58 out of 69 patients had undergone a PPH at the primary operation and 11 out of 69 a DSPPH.
In 23 patients (34%) primary surgery had been performed in other Hospitals.
Prolapse degree according to Goligher’s classification was: II degree in 15 cases, III degree in 36 cases, IV degree in 18 cases (Table 3).
The mean time of recurrence was 18 months (range 2-42 months) in the 58 patients, who had undergone a PPH and 12 months (range 2-42 months) in those who had undergone a D-PPH (Table 4).
All operations were performed at least six months after the onset of the recurrence’s symptoms. Only two patients underwent a reoperation after about two months for a haemorrhoidal thrombosis.
The clinical onset of recurrence appeared in the form of: haemorrhoidal crisis in 12 patients, bleeding in 8 patients, recurrent prolapse in 29 patients and residual prolapse in 20 patients (Table 5).
Intraoperative findings in the 58 patients, who had undergone a previous single PPH, were: 30 recurrent or residual prolapsed haemorrhoids with single or multiple piles- ≤3- (17 residual and 13 recurrent), 4 congested haemorrhoids, 18 mobile prolapse, 6 mobile prolapse associated with thrombosed haemorrhoids.
In these cases the operations chosen were: 34 excisional surgery, 12 PPH, 6 DSPPH, 6 PPH plus excisional surgery.
Intraoperative findings in the 11 patients, who had undergone a previous DSPPH, were: 6 recurrent or residual prolapsed haemorrhoids with single or multiple piles- ≤3- (3 residual and 3 recurrent), 2 congested haemorrhoids, 2 mobile prolapse, 1 mobile prolapse associated with thrombosed haemorrhoids.
In these cases the operations chosen were: 8 excisional surgery, 1 PPH, 1 DSPPH, 1 PPH plus excisional surgery.
Table 6 and 7 describe the intraoperative reports after a previous PPH and after a previous DSPPH and the operations applied.
The preoperative and postoperative management (use of painkillers drugs, antibiotics and laxatives), the kind of anaesthesia -general or local- of the patients undergoing reoperative surgery for recurring haemorrhoids was similar to that applied in the first operation.
The mean operative time was comparable to that of the primary surgery in patients treated with PPH or DSPPH or excisional surgery.
The hospital stay and return to full activity were similar to the primary operations.
Postoperative complications after a “stapled” operation (PPH, DSPPH) and after a “non stapled”operation are summarised in Table 8. They were comparable to those relative to primary surgery.
In the “stapled” group bleeding occurred in 3 patients.
In one case the bleeding was controlled by introducing a Foley catheter into the anorectum and by inflating its balloon at 30-40 cm3, one case was coped with a local application of a hemostatic device, one case required a surgical revision under anaesthesia.
In the “non stapled” group, instead, bleeding occurred in 1 patient and required a surgical revision.
2 patients in the “stapled” group and 2 patients in the “non stapler” group complained of urgency but this symptoms solved spontaneously one month after operation.
Postoperative pain was under control in both group thanks to the use of the routine FANS usually employed. However, there were 2 patients in the “stapled” group and 2 patients in the “non stapler” group, who reported persisting anal pain in the 2 weeks following operation and required further use of painkillers. After this time, the pain symptoms disappeared in these three patients and continued in the other one.
The mean follow-up after reoperative surgery resulted in 40 months (range, 23-96)
No cases of second recurrence occurred in the treated patients.
The outcome assessed on the basis of the clinical examination, as well as at the opinion expressed by the patients was excellent in 34 patients, good in 23 patients, sufficient in 8 patients, poor in 4 patients because two considered their symptoms (bleeding and congested haemorrhoids) unchanged, one reported a worsening of constipation and another complained of persistent pain.
DISCUSSION
The presence of a residual or recurrent prolapse can be derived or from an incorrect indication to surgery or from an insufficient resective approach. Alternatively it may be due to an operation, which had been previously carried out incorrectly with an insufficient pull of the prolapsed tissue in the operative case.
In case of recurrence, symptoms guide to the decision of a reoperation and the surgical technique is determined according to the intraoperative report, that in almost equal percentage is divided between the mobility of the prolapse and the presence of recurrent and/or residual haemorrhoidal prolapsed piles.
In the case of a mobile prolapse the choice was a transrectal resection with stapler (PPH or DSPPH, depending on the amount of the prolapse that should be resected). On the contrary, in the case of a fixed prolapse or single or multiple piles -≤3_, the choice should be a traditional surgery (Milligan Morgan, whatever performed). In case of multiple piles ≥3 the choice is a transrectal resection with stapler (PPH or DSPPH, depending on the amount of the prolapse that should be resected). A PPH combined with Milligan Morgan Haemorrhoidectomy is applied in case of a mobile prolapse with some residual pile.
CONCLUSIONS
Avoiding or minimizing the possibility of a recurrent prolapse should be demanded to a well realized primary operation, calibrated on the effective amount of the prolapse.
A complete clinical study with a correct evaluation of the symptoms and a careful intraoperative assessment of the recurrence’s features are of primary importance for the choice of the technique to be applied.
Re-excisional surgery but also a re-stapled procedure can be safely and successfully realized with the same operating methods of a primary operation, with no more complications or difficulties
UTILIZZO DI STRATEGIE E BIOMATERIALI PER LA RIDUZIONE DELLA DEGENZA E DELLE COMPLICANZE IN CHIRURGIA TIROIDEA
No full textLe indicazioni alla chirurgia tiroidea hanno subito, negli ultimi anni, modificazioni sostanziali rispetto alle tecniche comunemente adottate, proponendo la tiroidectomia totale in tutti i casi di patologia diffusa, anche se di tipo benigno. Questo orientamento si è arricchito, inoltre, di nuove tecnologie di dissezione che hanno ulteriormente perfezionato la tecnica operatoria, riducendo considerevolmente il trauma chirurgico ed i tempi di intervento. L'impiego di questi strumenti trova una precisa indicazione nelle incisioni dei tessuti molli e laddove si desideri un accurato controllo dell'emostasi con il minimo effetto termico laterale. La chirurgia della tiroide richiede un'indiscussa manualità chirurgica e comporta di norma l'uso di strumenti che possono esporre a fastidiosi sanguinamenti, spesso di non semplice controllo durante l'isolamento e la dissezione dei peduncoli vascolari e dei tessuti. Così, alle necessarie legature delle arterie polari se ne possono aggiungere numerose altre dirette ad emostasi non sempre agevoli, in particolare in ghiandole molto vascolarizzate e con rete venosa sviluppata e friabile. Tutto questo può comportare un allungamento dei tempi operatori e, quando si ricorre all'uso del bisturi elettrico, gravi rischi per le lesioni determinate dalla diffusione del calore, soprattutto in prossimità di strutture anatomiche molto delicate.
Gli obiettivi di questo studio sono l’individuazione di indicatori di processo ed outcome per una chirurgia con degenza post-operatoria breve, senza complicanze
Network Communication Privacy: Traffic Masking against Traffic Analysis
No full textAn increasing number of recent experimental works have been demonstrating the supposedly secure channels in the Internet are prone to privacy breaking under many respects, due to traffic features leaking information on the user activity and traffic content. As a matter of example, traffic flow classification at application level, web page identification, language/phrase detection in VoIP communications have all been successfully demonstrated against encrypted channels. In this thesis I aim at understanding if and how complex it is to obfuscate the information leaked by traffic features, namely packet lengths, direction, times. I define a security model that points out what the ideal target of masking is, and then define the optimized and practically implementable masking algorithms, yielding a trade-off between privacy and overhead/complexity of the masking algorithm. Numerical results are based on measured Internet traffic traces. Major findings are that: i) optimized full masking achieves similar overhead values with padding only and in case fragmentation is allowed; ii) if practical realizability is accounted for, optimized statistical masking algorithms attain only moderately better overhead than simple fixed pattern masking algorithms, while still leaking correlation information that can be exploited by the adversary
Control Algorithms and Architectures for Resource Management in Multi-Layered Systems: Application to SatCom, Security and Manufacturing Domains
No full textLast two decades have seen an exponential increase in the availability of innovative and cost effective technological solutions in a wide variety of fields, ranging from electronics to chemistry, from mechanics to computer science. These new potentialities have led to a growth in systems’ complexity, thus making their control and optimization a challenging task, eager for new methodologies, approaches, paradigms. With respect to this context, the doctorate research presented in this thesis aims at providing the scientific and industrial communities with enriched solutions to cope with a specific class of control applications, resource management, in a well-defined class of complex systems, the multi-layered ones.
Multi-layered systems are commonly obtained by incremental design or hierarchical approaches: several layers, each one assigned to a specific task, are put together to jointly create an enriched, vertical or end-to-end, behaviour. In such conditions, resources are necessarily distributed between layers and information sharing is limited, thus resulting in an underutilization of system’s potentialities and poor performances: efficient resource management solutions are needed.
Resource management is in fact the set of mechanism, procedures and algorithms that allow to control the allocation, distribution or utilization of systems’ capabilities (being them hardware or software functionalities, physical or logical resources): for this reason, they play a key role for the overall system’s performances; in recent years, control and optimization theories have proven to be the best candidates to address this class of problems.
This doctorate work provides original results in the following selected multi-layered domains:
- Satellite Communication, with the design of innovative cross-layer algorithms
- Security, with the formalization of the “composable security” by means of control theory
- Manufacturing, with the identification of a closed-loop “cognitive architecture” for the Factories of the Future.
To achieve these results, original research has been performed in the areas of: i) modelling techniques; ii) control algorithms; iii) optimization algorithms.
Some of these results have been jointly developed in the scope of European funded research, in particular in the MONET Project (Satellite Communication) and in the p/nSHIELD Projects (Security in Embedded Systems), where they have represented an original contribution with promising industrial exploitation perspectives.Results have been partially achieved in the scope of the following projects: MONET (FP7), pSHIELD (ARTEMIS-JU), nSHIELD (ARTEMIS-JU