204 research outputs found
A Network Analysis of Countries’ Export Flows: Firm Grounds for the Building Blocks of the Economy
No full textIn this paper we analyze the bipartite network of countries and products from UN data on country production. We define the country-country and product-product projected networks and introduce a novel method of filtering information based on elements’ similarity. As a result we find that country clustering reveals unexpected socio-geographic links among the most competing countries. On the same footings the products clustering can be efficiently used for a bottom-up classification of produced goods. Furthermore we mathematically reformulate the “reflections method” introduced by Hidalgo and Hausmann as a fixpoint problem; such formulation highlights some conceptual weaknesses of the approach. To overcome such an issue, we introduce an alternative methodology (based on biased Markov chains) that allows to rank countries in a conceptually consistent way. Our analysis uncovers a strong non-linear interaction between the diversification of a country and the ubiquity of its products, thus suggesting the possible need of moving towards more efficient and direct non-linear fixpoint algorithms to rank countries and products in the global market.</p
A high throughput Intrusion Detection System (IDS) to enhance the security of data transmission among research centers
No full textData breaches and cyberattacks represent severe problem in higher education institutions and universities that can result in illegal access to sensitive information and data loss. To enhance the security of data transmission, Intrusion Prevention Systems (IPS, i.e., firewalls) and Intrusion Detection Systems (IDS, i.e., packet sniffers) are used to detect potential threats in the exchanged data. IPSs and IDSs are usually designed as software programs running on a server machine.
However, when the speed of exchanged data is too high, this solution can become unreliable. In this case, IPSs and IDSs designed on a real hardware platform, such as ASICs and FPGAs, represent a more reliable solution. This paper presents a packet sniffer that was designed using a commercial FPGA development board. The system can support a data throughput of 10 Gbit/s with preliminary results showing that the speed of data transmission can be reliably extended to 100 Gbit/s. The designed system is highly configurable by the user and can enhance the data protection of information transmitted using the Ethernet protocol. It is particularly suited for the security of universities and research centers, where point-to-point network connections are dominant and large amount of sensitive data are shared among different hosts
Comparison Study of Constitutive Models in Predicting the Hot Deformation Behavior of AA6060 and AA6063 Aluminium Alloys
No full textThe aim of the present paper is to study the hot deformation behavior of two different Al alloys (AA6060 and AA6063) by means of hot torsion tests in the 400-550°C temperature range, typical of real extrusion temperatures. The behavior of the alloys, in terms of equivalent stress vs. equivalent strain, was modeled by different constitutive equations: Power law, Garofalo and Hensel-Spittel equations defined for different parameters. The flow stress curves predicted by the models were compared with experimental results for both alloys and discussed in order to define the accuracy of the models in predicting the materials hot flow stresses
A numerical model for NVH analysis of gearboxes employed on agricultural equipment
No full textThe aim of this paper is to describe a numerical vibro-acoustic methodology, experimentally assessed, for
the estimation of the overall vibratory and acoustic level of a gearbox employed on agricultural equipment.
The process is carried out in order to create the NVH digital twin of the real gearbox. The vibro-acoustic
model is the combination of three sub-models: a lumped-parameter (LP) model, a structural finite-element
(SFE) model and an acoustical finite-element (AFE) model. The LP model is used to obtain the reaction
forces on the bearings during working conditions. Reaction forces are employed as an input for the further
SFE dynamic model to evaluate the dynamic response of the gearbox’s case, which is the only meshed part.
The dynamic response is exploited to set-up an AFE model which allows to estimate the noise generation in
terms of overall acoustic pressure. The numerical simulation results are validated using experimental data
acquired on a real gearbox. Testing activities have been carried out at Comer Industries facility in Reggiolo,
where specimens and test benches have been set. Advantages and limitations of the model are reported
Clinical predictors of small intestinal bacterial overgrowth by duodenal aspirate culture
No full textBACKGROUND:
There has been increasing interest in small intestinal bacterial overgrowth (SIBO) after reports of a link with irritable bowel syndrome (IBS), yet our understanding of this entity is limited.
AIM:
Our aim was to estimate the yield of patients undergoing duodenal aspirate culture, and to identify symptoms and features that predict SIBO.
METHODS:
A medical chart review of patients who had undergone duodenal aspirate culture at an academic medical centre in 2003 was performed to record clinical characteristics and culture results. The associations between aspirate results and symptoms, medical diagnoses and medication use were assessed using logistic regression.
RESULTS:
A total of 675 patients had available aspirate results. Mean age of the sample was 53 (s.d. 17) and 443 (66%) were female patients. Overall, 8% of aspirates were positive for SIBO; 2% of IBS patients had SIBO. Older age, steatorrhoea and narcotic use were associated with SIBO (P < 0.05). PPI use was not associated with SIBO, but was associated with bacterial growth not meeting criteria for SIBO (P < 0.05). Inflammatory bowel disease (IBD), small bowel diverticula and pancreatitis were positively associated with an abnormal duodenal aspirate (P < 0.05), but other conditions including IBS were not associated with SIBO.
CONCLUSION:
Older age, steatorrhoea, narcotic use, IBD, small bowel diverticula and pancreatitis were associated with small intestinal bacterial overgrowth based on abnormal duodenal aspirate culture results. However, no clear associations of true small intestinal bacterial overgrowth with IBS or PPI use were detected, in contrast to recent speculation
Optimal Holding Period for a Real Estate Portfolio
No full textThis paper considers the use of simulated cash flows to determine the optimal holding period of a real estate portfolio to maximize its present value. The traditional DCF approach with an estimation of the resale value through a growth rate of the future cash flow does not let appear this optimum. However, if the terminal value is calculated from the trend of a diffusion process of the price, an optimum may appear under certain conditions. Finally we consider the sensitivity of the present value to the different parameters involved in the cash flow estimations.Cash Flows Simulations; Holding Period; Real Estate Portfolio Management
Topical Antiseptics in Minimizing Ocular Surface Bacterial Load Before Ophthalmic Surgery: A Randomized Controlled Trial
No full textPurpose: To investigate the reduction of the ocular surface bacterial load induced by 2 commercially available ophthalmic antiseptic formulations, povidone-iodine (PVI) 0.6% and chlorhexidine (CLX) 0.02%, before ocular surgery. Design: Randomized controlled trial. Methods: Seventy adult patients undergoing intraocular surgery (phacoemulsification) were randomized to receive in the index eye PVI (group A) 4 times a day for 3 days or CLX (group B) 4 times a day for 3 days before surgery. The untreated eye was used as control. A conjunctival swab was taken in both eyes before (T0) and after (T1) therapy. Microbial DNA was quantified with real-time polymerase chain reaction (PCR) analysis. The Mick algorithm was used to compare the abundance of each genus/genera against the distribution of abundances from the reference. At T1, patients filled a questionnaire to evaluate therapy-induced symptoms. Primary outcome was the reduction of bacterial DNA at T1 (microbial load), vs control arm, expressed as mean number of real-time PCR cycle times (CTs). Secondary outcomes were taxonomic composition, differential abundance, and therapy-induced ocular symptoms. Results: The T0-T1 difference in CT was significant in group B, but not in group A (mean [95% CI], 0.99 [0.33] vs 0.26 [0.15], P < .001, and 0.65 [0.3] vs 0.45 [0.41], P = .09, respectively). The taxonomic composition, alpha, and beta diversity remained consistent at all time points in both groups. The rate of patients reporting therapy-induced ocular symptoms and the mean discomfort grade were greater in group A than in group B (97% vs 26% and 4.97±2.48 vs 0.66±1.53, respectively). Conclusions: Compared with PVI 0.6%, CLX 0.02% induced a greater reduction of ocular surface bacterial load, with no significant alterations of the taxonomic composition. Moreover, CLX was better tolerated than PVI
Combining Monte Carlo Simulations and Options to Manage the Risk of Real Estate Portfolios
No full textThis paper aims to show that the accuracy of real estate portfolio valuations can be improved through the simultaneous use of Monte Carlo simulations and options theory. Our method considers the options embedded in Continental European lease contracts drawn up with tenants who may move before the end of the contract. We combine Monte Carlo simulations for both market prices and rental values with an optional model that takes into account a rational tenant's behavior. We analyze to what extent the options exercised by the tenant significantly affect the owner's income. Our main findings are that simulated cash flows which take account of such options are more reliable that those usually computed by the traditional method of discounted cash flow. Moreover, this approach provides interesting metrics, such as the distribution of cash flows. The originality of this research lies in the possibility of taking the structure of the lease into account. In practice this model could be used by professionals to improve the relevance of their valuations: the output as a distribution of outcomes should be of interest to investors. However, some limitations are inherent to our model: these include the assumption of the rationality of tenant's decisions, and the difficulty of calibrating the model, given the lack of data. After a brief literature review of simulation methods used for real estate valuation, the paper describes the suggested simulation model, its main assumptions, and the incorporation of tenant's decisions regarding break options influencing the cash flows. Finally, using an empirical example, we analyze the sensitivity of the model to various parameters, test its robustness and note some limitations.Monte Carlo Simulations ; Real Estate Portfolio Valuation ; Break options ; Lease Structure ; Options
Optimal holding period In Real Estate Portfolio
No full textThis paper considers the use of simulated cash flows to determine the optimal holding period in real estate portfolio to maximize its present value. The traditional DCF approach with an estimation of the resale value through a growth rate of the future cash flow does not let appear this optimum. However, if the terminal value is calculated from the trend of a diffusion process of the price, an optimum may appear under certain conditions. Finally we consider the sensitivity of the optimal holding period to the different parameters involved in the cash flow estimations. This methodology may be applied in commercial valuation and enables to get an optimal holding period for a given portfolio.valuation, DCF, optimal holding period, commercial property
L’intervento di Trabucco per la riparazione dell’ernia inguinale e crurale in anestesia locale in regime ambulatoriale : esperienza personale
No full textSince Bassini performed the first hernioplasty, more than one hundred years ago, all types of surgical procedure to repair groin and femoral hernias have a common defect: tension on suture line. This is the first pathological factors of recurrence hernia. Utilizing modern new prosthetic materials it's now possible to repair all types of hernias without changing normal anatomy of the region and without unwillingly tensions. After 15 years of experience with Shulman and Amid, Irwing L. Lichtenstein introduces the real change in hernia repair: the tension free repair. Trabucco aquired and changed the technique popularized by Lichtenstein. The technique championed by the authors is simple, effective, rapid, the postoperative pain is reduced and all patients return rapidly to full activities. Authors using Trabucco procedure to repair groin and femoral hernias in day hospital, describe their experience between January 1991 to November 1993
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