44,939 research outputs found
Diesel engine fuel injection monitoring using acoustic measurements and independent component analysis
Air-borne acoustic based condition monitoring is a promising technique because of its intrusive nature and the rich information contained within the acoustic signals including all sources. However, the back ground noise contamination, interferences and the number of Internal Combustion Engine ICE vibro-acoustic sources preclude the extraction of condition information using this technique. Therefore, lower energy events; such as fuel injection, are buried within higher energy events and/or corrupted by background noise.
This work firstly investigates diesel engine air-borne acoustic signals characteristics and the benefits of joint time-frequency domain analysis. Secondly, the air-borne acoustic signals in the vicinity of injector head were recorded using three microphones around the fuel injector (120° apart from each other) and an Independent Component Analysis (ICA) based scheme was developed to decompose these acoustic signals. The fuel injection process characteristics were thus revealed in the time-frequency domain using Wigner-Ville distribution (WVD) technique. Consequently the energy levels around the injection process period between 11 and 5 degrees before the top dead center and of frequency band 9 to 15 kHz are calculated. The developed technique was validated by simulated signals and empirical measurements at different injection pressure levels from 250 to 210 bars in steps of 10 bars. The recovered energy levels in the tested conditions were found to be affected by the injector pressure settings
Ozone: Efficient Execution with Zero Timing Leakage for Modern Microarchitectures
Time variation during program execution can leak sensitive information. Time
variations due to program control flow and hardware resource contention have
been used to steal encryption keys in cipher implementations such as AES and
RSA. A number of approaches to mitigate timing-based side-channel attacks have
been proposed including cache partitioning, control-flow obfuscation and
injecting timing noise into the outputs of code. While these techniques make
timing-based side-channel attacks more difficult, they do not eliminate the
risks. Prior techniques are either too specific or too expensive, and all leave
remnants of the original timing side channel for later attackers to attempt to
exploit.
In this work, we show that the state-of-the-art techniques in timing
side-channel protection, which limit timing leakage but do not eliminate it,
still have significant vulnerabilities to timing-based side-channel attacks. To
provide a means for total protection from timing-based side-channel attacks, we
develop Ozone, the first zero timing leakage execution resource for a modern
microarchitecture. Code in Ozone execute under a special hardware thread that
gains exclusive access to a single core's resources for a fixed (and limited)
number of cycles during which it cannot be interrupted. Memory access under
Ozone thread execution is limited to a fixed size uncached scratchpad memory,
and all Ozone threads begin execution with a known fixed microarchitectural
state. We evaluate Ozone using a number of security sensitive kernels that have
previously been targets of timing side-channel attacks, and show that Ozone
eliminates timing leakage with minimal performance overhead
Timed patterns: TCOZ to timed automata
Abstract. The integrated logic-based modeling language, Timed Communicating Object Z (TCOZ), is well suited for presenting complete and coherent requirement models for complex real-time systems. However, the challenge is how to verify the TCOZ models with tool support, especially for analyzing timing properties. Specialized graph-based modeling technique, Timed Automata (TA), has powerful mechanisms for designing real-time models using multiple clocks and has well developed automatic tool support. One weakness of TA is the lack of high level composable graphical patterns to support systematic designs for complex systems. The investigation of possible links between TCOZ and TA may benefit both techniques. For TCOZ, TA’s tool support can be reused to check timing properties. For TA, a set of composable graphical patterns can be defined based on the semantics of the TCOZ constructs, so that those patterns can be re-used in a generic way. This paper firstly defines the composable TA graphical patterns, and then presents sound transformation rules and a tool for projecting TCOZ specifications into TA. A case study of a railroad crossing system is demonstrated
Interpreting mega-development projects as territorial traps: the case of irrigation schemes on the shores of Lake Chad (Borno State, Nigeria)
From the colonial era up to the present, mega-irrigation projects for agriculture have played a key role in the production of state space in Sahelian Africa. Transferring a concept proposed by Agnew (1994) onto a different scale, it is possible to interpret these mega-projects as \u201cterritorial traps\u201d. In fact, they set up boundaries (physical, relational, cognitive and operative) that force evolutive trajectories of the areas involved along rigid pathways. In the aftermath of the systematic failure of the mega-projects, farmers are faced with constraints determined by the trap imposed, without having any of the promised benefits in terms of productive growth, i.e. income. In many situations, the farmers have identified \u201ca means of escape\u201d from these catastrophes by transgressing the boundaries imposed by the territorial traps and reintroducing parts of the infrastructure to a common use. The case study presented regards the irrigation mega-projects on the shores of Lake Chad, in Nigeria
YF-12 cooperative airframe/propulsion control system program, volume 1
Several YF-12C airplane analog control systems were converted to a digital system. Included were the air data computer, autopilot, inlet control system, and autothrottle systems. This conversion was performed to allow assessment of digital technology applications to supersonic cruise aircraft. The digital system was composed of a digital computer and specialized interface unit. A large scale mathematical simulation of the airplane was used for integration testing and software checkout
Abstractions and Static Analysis for Verifying Reactive Systems
Fokkink, W.J. [Promotor]Sidorova, N. [Copromotor
Time-sensitive Information Flow Control in Timed Event-B
Protecting confidential data in today’s computing\ud
environments is an important problem. Information flow\ud
control can help to avoid information leakage and violations\ud
introduced by executing the software applications. In software\ud
development cycle, it is important to handle security related\ud
issues from the beginning specifications at the level of abstract.\ud
Mu [1] investigated the problem of preserving information flow\ud
security in the Event-B specification models. A typed Event-\ud
B model was presented to enforce information flow security\ud
and to prevent direct flows introduced by the system. However,\ud
in practice, timing behaviours of programs can also introduce\ud
a covert flow. The problem of run-time flow monitoring and\ud
controlling must also be addressed. This paper investigates\ud
information flow control in the Event-B specification language\ud
with timing constructs. We present a timed Event-B system\ud
by introducing timers and relevant time constraints into the\ud
system events. We suggest a time-sensitive flow security condition\ud
for the timed Event-B systems, and present a type system\ud
to close the covert channels of timing flows for the system by\ud
ensuring the security condition. We then investigate how to\ud
refine timed events during the stepwise refinement modelling\ud
to satisfy the security condition
Quantitative Analysis Linking Inner Hair Cell Voltage Changes and Postsynaptic Conductance Change: A Modelling Study
This paper presents a computational model which estimates the postsynaptic conductance change of mammalian Type I afferent peripheral process when airborne acoustic waves impact on the tympanic membrane. A model of the human auditory periphery is used to estimate the inner hair cell potential change in response to airborne sound. A generic and tunable topology of the mammalian synaptic ribbon is generated and the voltage dependence of its substructures is used to calculate discrete and probabilistic neurotransmitter vesicle release. Results suggest an almost linear relationship between increasing sound level (in dB SPL) and the postsynaptic conductance for frequencies considered too high for neurons to phase lock with (i.e., a few kHz). Furthermore coordinated vesicle release is shown for up to 300–400 Hz and a mechanism of phase shifting the subharmonic content of a stimulating signal is suggested. Model outputs suggest that strong onset response and highly synchronised multivesicular release rely on compound fusion of ribbon tethered vesicles
The opportunity cost of capital of US buyouts
This paper addresses the problem of accurately determining buyout opportunity cost of capital for performance analyses. It draws on a unique and proprietary set of data on 133 United States buyouts between 1984 and 2004. For each buyout, we determine a public market equivalent that matches the buyout in timing and systematic risk. We show that under realistic mimicking conditions, the average opportunity cost of capital is below the commonly used benchmark S&P 500. The surprising result has a simple explanation: ex post, many of the transactions mimicking the buyouts would have defaulted in the public market. Only under relaxed assumptions, is the average opportunity cost of capital close to the average index return. Our sensitivity analyses highlight the need for a comprehensive risk adjustment that considers both operating risk and leverage risk for an accurate assessment of buyout performance. This finding is particularly important as existing literature on this topic tends to rely on benchmarks without a proper risk adjustment.Private Equity; Risk-Adjusted Performance; Buyout; Benchmarking Alternative Assets;
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