597 research outputs found
Modeling of premixing-prevaporizing fuel-air mixing passages
The development of a computer program for the analytical prediction of the distribution of liquid and vapor fuel in the premixing-prevaporizing passage by the direct injection method is described. The technical approach adopted for this program is to separate the problem into three parts each with its own computer code. These three parts are: calculation of the two-dimensional or axisymmetric air flow; calculation of the three-dimensional fuel droplet evaporation; and calculation of the fuel vapor diffusion. This method of approach is justified because premixing passages operate at lean equivalence ratios. Hence, a weak interaction assumption can be made wherein the airflow can affect the fuel droplet behavior but the fuel droplet behavior does not affect the airflow
Analytical modeling of operating characteristics of premixing-prevaporizing fuel-air mixing passages. Volume 2: User's manual
A user's manual describing the operation of three computer codes (ADD code, PTRAK code, and VAPDIF code) is presented. The general features of the computer codes, the input/output formats, run streams, and sample input cases are described
Detecting time-fragmented cache attacks against AES using Performance Monitoring Counters
Cache timing attacks use shared caches in multi-core processors as side
channels to extract information from victim processes. These attacks are
particularly dangerous in cloud infrastructures, in which the deployed
countermeasures cause collateral effects in terms of performance loss and
increase in energy consumption. We propose to monitor the victim process using
an independent monitoring (detector) process, that continuously measures
selected Performance Monitoring Counters (PMC) to detect the presence of an
attack. Ad-hoc countermeasures can be applied only when such a risky situation
arises. In our case, the victim process is the AES encryption algorithm and the
attack is performed by means of random encryption requests. We demonstrate that
PMCs are a feasible tool to detect the attack and that sampling PMCs at high
frequencies is worse than sampling at lower frequencies in terms of detection
capabilities, particularly when the attack is fragmented in time to try to be
hidden from detection
PerfWeb: How to Violate Web Privacy with Hardware Performance Events
The browser history reveals highly sensitive information about users, such as
financial status, health conditions, or political views. Private browsing modes
and anonymity networks are consequently important tools to preserve the privacy
not only of regular users but in particular of whistleblowers and dissidents.
Yet, in this work we show how a malicious application can infer opened websites
from Google Chrome in Incognito mode and from Tor Browser by exploiting
hardware performance events (HPEs). In particular, we analyze the browsers'
microarchitectural footprint with the help of advanced Machine Learning
techniques: k-th Nearest Neighbors, Decision Trees, Support Vector Machines,
and in contrast to previous literature also Convolutional Neural Networks. We
profile 40 different websites, 30 of the top Alexa sites and 10 whistleblowing
portals, on two machines featuring an Intel and an ARM processor. By monitoring
retired instructions, cache accesses, and bus cycles for at most 5 seconds, we
manage to classify the selected websites with a success rate of up to 86.3%.
The results show that hardware performance events can clearly undermine the
privacy of web users. We therefore propose mitigation strategies that impede
our attacks and still allow legitimate use of HPEs
Top Quark Production in Extended Bess Model
We study top production at Tevatron collider in the extended BESS model,
which is an effective lagrangian parametrization of a dynamical symmetry
breaking of the electroweak symmetry. The existence of a colored octet of gauge
vector bosons can increase top production at a rate still consistent with
recent experimental data and lead to distorsions in the transverse momentum
spectrum of the top.Comment: 13 pages, LaTeX, 4 figure
High Pressure Angle Spur Gears for Epicyclic Gear Trains
Advanced in engineering technology have resulted in increased gearing performances. The use of high power density transmission systems such as epicyclic gear trains is the way to achieve the goal reducing the overall volume and mass compared with traditional configurations. Gears are the main component of the transmissions because they play the crucial role of transmitting the power from the input to the output with a defined ratio. In terms of gear performances, tooth geometry has a direct influence on load carrying capacity: increase the pressure angle modifies the tooth profile with a direct influence on bending and contact stress. To test the benefits of high pressure angles gears in epicyclic transmissions, four different epicyclic systems with same boundary design conditions have been modelled. The reference pressure angle have been varied from 20° to 35° and other gear parameters such as profile shift coefficient, addendum and dedendum length have been modified consequently to match the design requirements. The results show that increasing the pressure angle has a reductive effect on contact and bending stresses. Using high pressure angle gears in epicyclic transmissions has a beneficial effect on tensile stresses but is unfavourable for the compressive ones. Moreover, it has been seen that pressure angle effect might be enhanced or nullified if other modifications such as profile shift are used concurrently
Z' Physics
The limits on extra neutral gauge bosons, which could be reached at LEP2, are
reviewed. Exclusion and discovery limits are discussed for f\bar f and WW
production.Comment: 20 pages Latex, 7 figures included by epsfig, Contribution to the
Proceedings the workshop "Physics at LEP2", Geneva, 199
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