Probabilistic Approach

With the growing deployment of host and network intrusion detection systems, managing reports from these systems becomes critically important. We present a probabilistic approach to alert correlation, extending ideas from multisensor data fusion. Features used for alert correlation are based on alert content that anticipates evolving IETF standards. The probabilistic approach provides a unified mathematical framework for correlating alerts that match closely but not perfectly, where the minimum degree of match required to fuse alerts is controlled by a single configurable parameter. Only features in common are considered in the fusion algorithm. For each feature we define an appropriate similarity function. The overall similarity is weighted by a specifiable expectation of similarity. In addition, a minimum similarity may be specified for some or all features. Features in this set must match at least as well as the minimum similarity specification in order to combine alerts, regardless of the goodness of match on the feature set as a whole. Our approach correlates attacks over time, correlates reports from heterogeneous sensors, and correlates multiple attack steps.

The reaction of HIV protease to inhibitor therapy is characterized by the emergence of complex mutational patterns which confer drug resistance. The response of HIV protease to drugs often involves both primary mutations that directly inhibit the action of the drug, and a host of accessory resistance mutations that may occur far from the active site but may contribute to restoring the fitness or stability of the enzyme. Here we develop a probabilistic approach based on connected information that allows us to study residue, pair level and higherorder correlations within the same framework. We apply our methodology to a database of approximately 13,000 sequences which have been annotated by the treatment history of the patients from which the samples were obtained. We show that including pair interactions is essential for agreement with the mutational data, since neglect of these interactions results in order-of-magnitude errors in the probabilities of the simultaneous occurence of many mutations. The magnitude of these pair correlations changes dramatically between sequences obtained from patients that were or were not exposed to drugs. Higher-order effects make a contribution of as much as 10% for residues taken three at a time, but increase to more than twice that for 10 to 15-residue groups. The sequence data is insufficient to determine the higher-order effects for larger groups. We find that higher-order interactions have a significant effect on the predicted frequencies of sequences with large numbers of mutations. While relatively rare, such sequences are more prevalent after multi-drug therapy. The relative importance of these higher-order interactions increases with the number of drugs the patient had been exposed to. Correlations are critical for the understanding of mutation patterns in HIV protease. Pair interactions have substantial qualitative effects, while higher-order interactions are individually smaller but may have a collective effect. Together they lead to correlations which could have an from ECCB 2008 Workshop: Annotations, interpretation and management of mutations (AIMM) Cagliari, Italy.

The numerical solution of Partial Differential Equations onto random domains can be done by using a mapping transforming this random domain into a deterministic domain. The issue is then to determine this one to one random mapping. In this paper, we present two methods -one based on the resolution of the Laplace equations, one based on a geometric transformation -to determine the random mapping. A stochastic magnetostatic example is treated to compare these methods.

This paper presents a validation of a recently developed joi nt input-state estimation algorithm for force identification and response estimation in structural dynam ics, using data obtained from in situ experiments on a footbridge. First, the algorithm is used to identi fy two impact forces applied to the bridge deck. Next, the algorithm is used to extrapolate measured ac celerations due to wind loading to unmeasured locations in the structure. The dynamic model of th e ootbridge used in the system inversion is obtained from a detailed finite element model, that is cali br ted using a set of experimental modal characteristics. The quality of the estimated forces and ac celerations is assessed by comparison with the corresponding measured quantities. In both cases, a ver y good overall agreement is obtained.

We consider the task of accurately controlling a complex system, such as autonomously sliding a car sideways into a parking spot. Although certain regions of this domain are extremely hard to model (i.e., the dynamics of the car while skidding), we observe that in practice such systems are often remarkably deterministic over short periods of time, even in difficult-to-model regions. Motivated by this intuition, we develop a probabilistic method for combining closed-loop control in the well-modeled regions and open-loop control in the difficult-to-model regions. In particular, we show that by combining 1) an inaccurate model of the system and 2) a demonstration of the desired behavior, our approach can accurately and robustly control highly challenging systems, without the need to explicitly model the dynamics in the most complex regions and without the need to hand-tune the switching control law. We apply our approach to the task of autonomous sideways sliding into a parking spot, and show that we can repeatedly and accurately control the system, placing the car within about 2 feet of the desired location; to the best of our knowledge, this represents the state of the art in terms of accurately controlling a vehicle in such a maneuver.

In mobile ad hoc networks (MANET), broadcasting is widely used in route discovery and many other network services. The efficiency of broadcasting protocol can affect the performance of the entire network. As such, the simple flooding algorithm aggravates a high number of unnecessary packet rebroadcasts, causing contention and packet collisions. Proper use of probabilistic method can reduce the number of rebroadcasting, therefore reduce the chance of contention and collision among neighbouring nodes. A good probabilistic broadcast protocol can achieve high save rebroadcast and low collision. In this paper, we propose a dynamic probabilistic approach when nodes move according to different mobility models and compare it with simple flooding AODV and fixed probabilistic scheme. Our approach dynamically set the rebroadcast probability according to the number of neighbour nodes distributed in the ad hoc network. Simulation results show our approach performs better than both simple flooding and fixed probabilistic flooding.

Ad hoc network protocols use flooding as the basic mechanism to disseminate control packets. As such, the simple flooding algorithm aggravates a high number of superfluous packet rebroadcasts, causing contention, packet collisions and ultimately wasting valuable limited bandwidth. The efficiency of broadcasting protocol can dramatically affect the performance of the entire network. In a large network, with heavy load, this extra overhead can have severe impact on performance and should be eliminated. In this paper, we proposed a dynamic probabilistic approach when nodes move according to way point mobility and evaluate it against simple flooding and fixed probabilistic scheme. We assess the performance of our approach by comparing it with the ad hoc on-demand distance vector (AODV) protocol (which is based on simple flooding) as well as a fixed probabilistic approach. Moreover, the results indicate that the dynamic probabilistic technique demonstrates better performance as compared to the simple flooding and fixed probabilistic technique.

Advances in hurricane climate science allow forecasts of seasonal landfall activity to be made. The authors begin with a review of the forecast methods available in the literature. They then reformulate the methods using a Bayesian probabilistic approach. This allows a direct comparison to be made while focusing on a single hindcast of the 2004 season over Florida. The models, including climatology, are estimated using Gibbs sampling. Diagnostic checks verify convergence and efficient mixing of the samples from each of the models. A below average sea level pressure gradient over the eastern North Atlantic Ocean during May and June in combination with an above average tropospheric-averaged wind index associated, in part, with a strengthening of the Bermuda high pressure during July resulted in an above average probability of at least one Florida hurricane. The relatively high hindcast probabilities for 2004 were in marked contrast to the most recent 50-yr empirical probabilities for Florida, but fell short in anticipating the unprecedented level of activity that ensued. Similar results are obtained from hindcasts of total U.S. hurricane activity for 2004.

The hip arthroplasty with cementless hip prosthesis is a solution usually used for
the patients suffering the problems of the musculoskeletal system. However, such
a solution has a major disadvantage, pointed by all users: the lack of primary
stability of the prosthesis. This weakness can cause serious complications or failure of the surgery. Therefore, to achieve a good primary fixation is a crucial point of this type of surgery to ensure a short and a long-term clinical satisfaction.
In order to better understand this central issue, a preoperative track is adopted.
A finite element model to describe the mechanical behavior of the coupled system
“Femur-cementless prosthesis: DePuy Corail®” has been created and validated by the experiments in vitro. Then, in order to take into account the high variability of model parameters, inherent to the nature of the problem, the stochastic modeling of random input parameters has been introduced and a mechanical-probabilistic strategy has been proposed, on the one hand to quantify, in probabilistic terms, the effect, on the response, of the uncertainties affecting the input parameters of the model, and on the other hand to evaluate the primary stability of the bone-prosthesis system in reliability context. The practical implementation of this approach is realized by using the numerical tools based on the standard Monte Carlo method and the stochastic collocation procedure.
The originality of the work presented is primarily in the proposition of a probabilistic methodology capable of taking into account the uncertainties in the problem of primary stability of cementless hip prostheses. It also lies in the potentiality of this methodology to be transplantable easily in industrial context.

Conventional methods of palaeoclimate reconstruction provide estimates of climatic parameters using proxy data which have originated from individual sites. These reconstructions yield information on the local environment but only limited information on spatial scales that are required for model-data intercomparisons. We present here a new approach that connects these different scales by an upscaling of the local palaeoinformation together with

Dramatic changes in European vegetation occurred during the transition from the Eemian interglacial to Weichselian glacial climates, correlative with major changes in global ice core and marine records. Quantitative knowledge of climate change is important for understanding of the climate system and for climate modelling, for which reconstructions of this transitional period are of special interest. However, it has been difficult to quantify the climatic changes involved in the Eemian to Early Weichselian transition from terrestrial archives due to the lack of modern vegetation analogues. To circumvent this problem, we applied a suitable multivariate probabilistic approach to pollen and plant macrofossil assemblages to reconstruct temperature and precipitation for this transition in central Europe. Our reconstructions span the interval from the beginning of the Eemian (Marine Isotope Stage (MIS) 5e) to the Odderade interstadial (MIS 5a). They indicate a relatively stable Eemian, with increasing precipitation reducing the continentality of the climate with time. During the transition from the Eemian to the Herning stadial, mean July and January temperatures decreased by $4 1C and by as much as $20 1C, respectively. Temperatures remained high enough to support forests during the stadials, and we infer that the reconstructed decrease of precipitation below 500 mm per year caused the extirpation of forests during these periods. Thus, we conclude that precipitation, although difficult to reconstruct, is of vital importance for explaining vegetation change during the Eemian and Eemian/Early Weichselian transition.

SUMMARY This summary on the paper on erosion model based on grainsize distribution ratios of weathering product of Quaternary volcanic deposits in Bandung Basin, West Java, is the latest development in these issues in Indonesia. USLE formula known as formula for annual erosion prediction is no longer accurate, which needs a modification, in term of involvement of soil variables determining

The problem of object restoration in the case of spatially incoherent illumination is considered. A regularized solution to the inverse problem is obtained through a probabilistic approach, and a numerical algorithm based on the statistical analysis of the noisy data is presented. Particular emphasis is placed on the question of the positivity constraint, which is incorporated into the probabilistically regularized solution by means of a quadratic programming technique. Numerical examples illustrating the main steps of the algorithm are also given.

Pyroclastic density currents (PDCs) are extremely dangerous phenomena so their modeling is essential for hazard and risk purposes. However, PDCs are governed by very complex processes, making their deterministic prediction impossible. Probabilistic approaches are in a pioneering phase and feature large (and still unknown) uncertainties, from the natural variability of PDCs (aleatory uncertainty) to the main sources of epistemic uncertainty (input, parametric, theoretical and structural). In this chapter, we quantify these uncertainties by using the Energy Cone Model (ECM) in a Monte Carlo scheme applied to Mount Vesuvius. According to our results, theoretical uncertainty has the largest impact, 5 to 100 times bigger than input uncertainty, which seems to play a minor role. We find that conditional probabilities of PDC arrival (given an eruption of a specific size)
show spatial distributions related to the surrounding topography. In particular, for medium and large eruptions, the conditional probability of PDCs traveling beyond Mount Somma is 1%–15% and 50%–60%, while they
reach the Napoli airport in about 0%–1% and 0%–15% of the simulations, respectively. Small‐eruption PDCs remain restricted to the south flank and summit area. These results may guide future research devoted to reduce
epistemic uncertainties and improve volcanic hazard analyses associated with PDCs.

Use of probabilistic methods are increasing in civil engineering design. The probabilistic methods allows designers, firstly, to take into account uncertainties of input parameters and to treat them as random variables. Secondly the civil engineering structure can be considered like a system which comprises number of components. Subsequently probabilistic approach aims to determine the true probability of failures of the whole system and to judge its acceptability in the view of the consequences. Having an existing system the actual safety level of the system is interested issue. By application of the probabilistic design this issue is able to be solved by implementing a reliability safety assessment, in which all possible failure mechanisms is taken into consideration as well as uncertainties of the boundary condition. However, questions are often reversed when the structured system is in design phases. Typically, these two following questions may arise: (i) what should be design safety level? And, (ii) given a design safety level, what will be the best design alternative of the system? The first question is possible to answer by optimizing costs of construction and the consequences of system failure. A framework of risk analysis is developed for this purpose and presented by a "risk-based optimization model" in this paper. Since the level of safety is chosen, various geometry alternatives of the system components can be generated. In order to answer the last question, for each of those the failure probability and the total cost of construction need be determined. Again the minimum point of total construction costs in space of failure probability is searched, given a required level of safety (level of protection). This later procedure is, in this study, called "reliability-based optimization model". This paper presents the basis of probabilistic design and risk-based approach and some initial results for these above issues with an application to the sea dikes system in Vietnam. Methods and proposed models can be modified and developed in order to be able to apply widely for other types of structure system in the field of civil engineering.

The use of admixtures particularly plasticizers/water reducing admixtures for improved performance of concrete cannot be over emphasized. However, most researches on concrete containing plasticizers/water reducing admixtures concentrate on mineral oil admixtures which are not eco-friendly. This study is therefore aimed at investigating the performance of castor oil as a bio-admixture (plasticizer) in concrete. The study investigated the properties of castor oil, its water reduction in cement and concrete, compressive strength and flexural strength of concrete specimens. The castor oil was extracted by mechanical method using hydraulic press. The concrete used was grade 20 and the castor oil dosages by weight of cement adopted were 0.0%, 0.25%, 0.5%, 0.75%, and 1.0%. Water reduction capability of castor oil was tested on cement paste using standard consistency and on concrete using slump. A total of 138 specimens were cast of which 108 were cubes of size 100 x 100 x 100mm and 30 were beams of size 100 x 100 x 500mm. The specimens were cured in water until testing period. For compressive strength, the specimens were tested at 3, 7, 28 and 56 days while for flexural strength, the specimens were tested at 7 and 28 days. The physicochemical properties of castor oil were found to conform to the requirements of ASTM D960, BS EN 1008 and IS 456. The chloride content slightly exceeded the maximum value specified for concrete containing embedded steel by 24.07%. The castor oil reduced the quantity of mixing water for both cement paste and concrete mixture however the reduction was higher in concrete with 7.86% at 1.0% dosage. All the castor oil dosages decreased the compressive strength of concrete with 1.0% recording the highest reduction of 27.55% at 7 days. However, there was improvement in the compressive strength of the concrete due to the water reduction effect of castor oil up to 0.5% dosage with 0.25% recording the highest increment of 8.45% compared to the control at 28 days. Similarly, the admixture improves the stiffness of concrete due to its water reduction effect which led to increment in flexural strength of the concrete compared to the control up to 0.5% dosage. The study concludes that castor oil addition reduces compressive strength of concrete however its water reduction effect improves both the compressive and flexural strength. Thus, the study recommends 0.25% of castor oil by weight of cement as optimum dosage for satisfactory performance of concrete.

There exist injective Tauberian operators on L 1 (0, 1) that have dense, nonclosed range. This gives injective nonsurjective operators on ∞ that have dense range. Consequently, there are two quasi-complementary noncomplementary subspaces of ∞ that are isometric to ∞.

This paper presents new statistical methods in the field of exposure assessment. We focus on the estimation of the probability for the exposure to exceed a fixed safe level such as the provisional tolerable weekly intake (PTWI), when both consumption data and contamination data are independently available. Various calculations of exposure are proposed and compared. For many contaminants, PTWI belongs to the exposure tail distribution, which suggests the use of extreme value theory (EVT) to evaluate the risk. Our approach consists in modelling the exposure tail by a Pareto type distribution characterized by a Pareto index which may be seen as a measure of the risk of exceeding the PTWI. Using propositions by EVT specialists, we correct the bias of the usual Hill estimator to accurately estimate this risk index. We compare the results with an empirical plug-in method and show that the Pareto adjustment is relevant and efficient when exposure is low compared to the PTWI while the plug-in method should be used when exposure is higher. To illustrate our approach, we present some exposure assessment for heavy metals (lead, cadmium, mercury) via sea product consumption.

A new automatic method of calculation of a long-term representative wind climate is proposed. The procedure is based on the calculation of the joint probability distribution of the wind at a local station and at a long-term reference meteorological mast. The results obtained with this algorithm are compared with estimations of the long-term climate obtained with a Measure-Correlate-Predict method. The agreement found is good, even for very different periods of measurement.

Reinforced concrete (RC) structures subjected to aggressive environmental exposure conditions are traditionally designed to satisfy safety, serviceability, durability and aesthetics requirements throughout their operational design service life. This is usually established using time-dependent mathematical models, developed through performancebased methodologies in guidelines and European and national standards. However, at present, in most cases, prescriptive methodologies are used. The objective of this paper is to compare, as regards chloride induced corrosion, defined target periods of service life according to a prescriptive methodology with service life results of a performance-based methodology. In the laboratory concrete specimens were manufactured having compositions according to a prescriptive specification. These specimens were tested in order to determine their performance properties (strength, chloride diffusion and capillary absorption). Test results were included in the mathematical models of the performance-based specifications. The classic safety factor and recent probabilistic approaches have been used to estimate the service life of each composition being compared to the target periods defined in the prescriptive specification. Numerical calculations show that the results of the Partial Safety Factor and a full probabilistic approach are distinctly different and consequently their convergence still needs to be improved, due to the complexity of the process of chloride penetration into the concrete, not only the model but also the input values. When compared to performance-based approaches it would be expected that the prescriptive methodology would be more conservative due to its less quantified information on concrete and environment properties, though in this study this was not always true.

Often, High Brightness LEDs (HB-LED) are connected in series to create strings. According to their data sheets, the HB-LEDs have a variation in their forward voltage drop. This forward voltage variation may create a non-uniform illumination if the strings are connected in parallel. This paper proposes a probabilistic approach for modeling the forward voltage drop across the HB-LEDs and determining the value of the resistance needed in each string to control the current. The results of this paper show that when the probabilistic models are used, the value of the added balancing resistance is reduced compared to when using standard worst case models.

The setting of back up zones in distance relays has to deal with fault current infeeds between the relay and remote faults. Traditional approaches to this problem are conservative, some times leaving portions of a Power System without sensitive or selective back up protection. In this paper a probabilistic model for the relay errors resulting from the variation of the infeeds is developed. Other measurement inaccuracies are also considered in order to build a probabilistic approach to setting all zones of distance relays. The developed concepts are associated to automatic tools for computer aided protection coordination and applied to the Portuguese Transmission grid.

Modelling hydrocarbon migration in complex depositional environments is a difficult task. This paper illustrates a workflow that has been developed in order to make use of information at seismic resolution for migration modelling purposes. After a regional identification of the main seismic sequence boundaries and systems tracts, the first step of the workflow consists in a semi-automatic classification of the sand and shale prone seismic facies that are interpretable in the seismic volume. A software based on supervised neural network techniques and textural seismic attributes supports volumetric classification. Each class represents a different facies with specific petrophysical properties (threshold pressure, porosity, irreducible water saturation, etc.), assigned according to concurrent sedimentological studies; the result is a 3D lithofacies model. Petroleum system modelling is performed on a 3D regional model up to the calculation of hydrocarbon quantities expelled from the source rock. Then migration modelling is performed on the smaller area covered by the 3D lithofacies model. Invasion percolation approach has been chosen because it allows to perform migration modelling at a scale that is small enough to maintain a sufficient detail of the channels' shape and of their connections. A probabilistic approach allows to estimate charge risk in new prospects and to check modelling consistency. This workflow has been applied in a deep water setting in West Africa, characterized by an interconnected channel system, where a number of prospects had to be evaluated. A well was drilled in the area prior to this study, resulting dry in spite of being located in a position where the source rock is present and is deemed to have expelled interesting amounts of hydrocarbons. This study has shown that hydrocarbons expelled from the source appear to be deviated laterally by the presence of a local seal and therefore do not reach the channel system in the well location.

Persons working for VKM, either as appointed members of the Committee or as external experts, do this by virtue of their scientific expertise, not as representatives for their employers. The Civil Services Act instructions on legal competence apply for all work prepared by VKM.

Range-Only SLAM (RO-SLAM) represents a difficult problem due to the inherent ambiguity of localizing either the robot or the beacons from distance measurements only. Most previous approaches to this problem employ nonprobabilistic batch optimizations or delay the initialization of new beacons within a probabilistic filter until a good estimate is available. The contribution of this work is the formulation of RO-SLAM as an online Bayesian estimation process based on a Rao-Blackwellized Particle Filter. The conditional distribution for each beacon is initialized using an additional particle filter which, eventually, is transformed into an extended Kalman filter when the uncertainty becomes sufficiently small. This approach allows the introduction of new beacons without either delay or any special non-probabilistic processing. We validate our proposal with experiments for both simulated and real datasets.

Precision Time Protocol (PTP) synchronizes clocks of networked elements by exchanging messages containing precise time-stamps. Based on the available timing information, different algorithms can be developed for the clock synchronization. This paper introduces a novel PTPbased method in which clock synchronization is formulated as a probabilistic inference problem and is solved by Kalman filtering. The performance of this approach is verified by numerical results.

Accurate estimations of the health risks to astronauts due to space radiation exposure are necessary for future lunar and Mars missions. Space radiation consists of solar particle events (SPEs), comprised largely of medium energy protons (less than several hundred MeV); and galactic cosmic rays (GCR), which include high energy protons and heavy ions. While the frequency distribution of SPEs depends strongly upon the phase within the solar activity cycle, the individual SPE occurrences themselves are random in nature. A solar modulation model has been developed for the temporal characterization of the GCR environment, which is represented by the deceleration potential, φ. The risk of radiation exposure to hardware as well as to astronauts from SPEs during extra-vehicular activities (EVAs) or in lightly shielded vehicles is a major concern for radiation protection. To support the probabilistic risk assessment for EVAs, which could be up to 15% of crew time on lunar missions, we estimated the probability of SPE occurrence as a function of solar cycle phase using a non-homogeneous Poisson model to fit the historical database of measurements of protons with energy > 30 MeV, Φ 30. The resultant organ doses and dose equivalents, as well as effective whole body doses, for acute and cancer risk estimations are analyzed for a conceptual habitat module and for a lunar rover during space missions of defined durations. This probabilistic approach to radiation risk assessment from SPE and GCR is in support of mission design and operational planning for future manned space exploration missions.

We establish a structure theorem for the family of Ammann A2 tilings of the plane. Using that theorem we show that every Ammann A2 tiling is self-similar in the sense of [B. Solomyak, Nonperiodicity implies unique composition for self-similar translationally finite tilings, Discrete and Computational Geometry 20 (1998) 265-279]. By the same techniques we show that Ammann A2 tilings are not robust in the sense of [B. Durand, A. Romashchenko, A. Shen. Fixed-point tile sets and their applications, Journal of Computer and System Sciences, 78:3 (2012) 731-764].

Memory devices often consume more energy than microprocessors in current portable embedded systems, but their energy consumption changes significantly with the type of transaction, data values, and access timing, as well as depending on the total number of transactions. These variabilities mean that an innovative tool and framework are required to characterize modern memory devices running in embedded system architectures. We introduce an energy measurement and characterization platform for memory devices, and demonstrate an application to multilevel-cell (MLC) flash memories, in which we discover significant value-dependent programming energy variations. We introduce an energy-aware data compression method that minimizes the flash programming energy, rather than the size of the compressed data, which is formulated as an entropy coding with unequal bit-pattern costs. Deploying a probabilistic approach, we derive energy-optimal bit-pattern probabilities and expected values of the bit...

This paper proposes a new probabilistic approach for describing uncertainty in the ensembles of latent heat flux proxies. The proxies are obtained from hourly Bowen ratio and satellite-derived measurements, respectively, at several locations in the southern Great Plains region in the United States. The novelty of the presented approach is that the proxies are not considered separately, but as bivariate samples from an underlying probability density function. To describe the latter, the use of Gaussian mixture density models—a class of nonparametric, data-adaptive probability density functions—is proposed. In this way any subjective assumptions (e.g., Gaussianity) on the form of bivariate latent heat flux ensembles are avoided. This makes the estimated mixtures potentially useful in nonlinear interpolation and nonlinear probabilistic data assimilation of noisy latent heat flux measurements. The results in this study show that both of these applications are feasible through regionaliz...

In this paper the problem of recovering a regularized solution of the Fredholm integral equations of the first kind with Hermitian and square-integrable kernels, and with data corrupted by additive noise, is considered. Instead of using a variational regularization of Tikhonov type, based on a priori global bounds, we propose a method of truncation of eigenfunction expansions that can be proved to converge asymptotically, in the sense of the L 2 -norm, in the limit of noise vanishing. Here we extend the probabilistic counterpart of this procedure by constructing a probabilistically regularized solution without assuming any structure of order on the sequence of the Fourier coefficients of the data. This probabilistic approach allows us to use the statistical tools proper of time-series analysis, and in this way we attain a new regularizing algorithm, which is illustrated by some numerical examples. Finally, a comparison with solutions obtained by the means of the variational regularization exhibits how some intrinsic limits of the variational-based techniques can be overcome.

Material classification is a key step in creating computer graphics models and images from volume data. We present a new algorithm for identifying the distribution of different material types in volumetric datasets such as those produced with Magnetic Resonance Imaging (MRI) or Computed Tomography (CT). The algorithm assumes that voxels can contain more than one material, e.g. both muscle and fat; we wish to compute the relative proportion of each material in the voxels. Other classification methods have utilized Gaussian probability density functions to model the distribution of values within a dataset. These Gaussian basis functions work well for voxels with unmixed materials, but do not work well where the materials are mixed together. We extend this approach by deriving non-Gaussian "mixture" basis functions. We treat a voxel as a volume, not as a single point. We use the distribution of values within each voxel-sized volume to identify materials within the voxel using a probabilistic approach. The technique reduces the classification artifacts that occur along boundaries between materials. The technique is useful for making higher quality geometric models and renderings from volume data, and has the potential to make more accurate volume measurements. It also classifies noisy, low-resolution data well.

Material classification is a key step in creating computer graphics models and images from volume data. We present a new algorithm for identifying the distribution of different material types in volumetric datasets such as those produced with Magnetic Resonance Imaging (MRI) or Computed Tomography (CT). The algorithm assumes that voxels can contain more than one material, e.g. both muscle and fat; we wish to compute the relative proportion of each material in the voxels. Other classification methods have utilized Gaussian probability density functions to model the distribution of values within a dataset. These Gaussian basis functions work well for voxels with unmixed materials, but do not work well where the materials are mixed together. We extend this approach by deriving non-Gaussian "mixture" basis functions. We treat a voxel as a volume, not as a single point. We use the distribution of values within each voxel-sized volume to identify materials within the voxel using a probabilistic approach. The technique reduces the classification artifacts that occur along boundaries between materials. The technique is useful for making higher quality geometric models and renderings from volume data, and has the potential to make more accurate volume measurements. It also classifies noisy, low-resolution data well.

The paper argues that the weak effect of exports on gdp growth in Mexico is partly explained by two features of the Mexican economy that arose subsequent to trade liberalization: the peso's continued real appreciation and the large and rising share of the maquila sector in manufacturing exports. The argument is developed through an analytical example for a stationary economy with no investment. As motivation for the example's main assumptions, the paper presents empirical evidence gathered from the country's Annual Industrial Survey and the estimation of cointegration equations for maquila and non-maquila intermediate imports. The empirical evidence shows that (a) exports are highly dependent on imports and thus benefit from trade liberalization, and (b) while real exchange rate changes can induce substitution between local and imported intermediate goods generally, this is not the case in the maquila sector.

In mobile ad hoc networks (MANETs), broadcasting plays a fundamental role, diffusing a message from a given source node to all the other nodes in the network. Flooding is the simplest and commonly used mechanism for broadcasting in MANETs, where each node retransmits every uniquely received message exactly once. Despite its simplicity, it however generates redundant rebroadcast messages which results in high contention and collision in the network, a phenomenon referred to as broadcast storm problem. Pure probabilistic approaches have been proposed to mitigate this problem inherent with flooding, where mobile nodes rebroadcast a message with a probability p which can be fixed or computed based on the local density. However, these approaches reduce the number of rebroadcasts at the expense of reachability. On the other hand, counter-based approaches inhibit a node from broadcasting a packet based on the number of copies of the broadcast packet received by the node within a random access delay time. These schemes achieve better throughput and reachability, but suffer from relatively longer delay. In this paper, we propose an efficient broadcasting scheme that combines the advantages of pure probabilistic and counter-based schemes to yield a significant performance improvement. Simulation results reveal that the new scheme achieves superior performance in terms of saved-rebroadcast, reachability and latency.

Reinforced concrete (RC) structures subjected to aggressive environmental exposure conditions are traditionally designed to satisfy safety, serviceability, durability and aesthetics requirements throughout their operational design service life. This is usually established using time-dependent mathematical models, developed through performancebased methodologies in guidelines and European and national standards. However, at present, in most cases, prescriptive methodologies are used. The objective of this paper is to compare, as regards chloride induced corrosion, defined target periods of service life according to a prescriptive methodology with service life results of a performance-based methodology. In the laboratory concrete specimens were manufactured having compositions according to a prescriptive specification. These specimens were tested in order to determine their performance properties (strength, chloride diffusion and capillary absorption). Test results were included in the mathematical models of the performance-based specifications. The classic safety factor and recent probabilistic approaches have been used to estimate the service life of each composition being compared to the target periods defined in the prescriptive specification. Numerical calculations show that the results of the Partial Safety Factor and a full probabilistic approach are distinctly different and consequently their convergence still needs to be improved, due to the complexity of the process of chloride penetration into the concrete, not only the model but also the input values. When compared to performance-based approaches it would be expected that the prescriptive methodology would be more conservative due to its less quantified information on concrete and environment properties, though in this study this was not always true.

In this paper we propose a routing strategy for enabling publish-subscribe communication in a sensor network. The approach is semi-probabilistic, in that it relies partly on the dissemination of subscription information and, in the areas where this is not available, on random rebroadcast of event messages. We illustrate the details of our approach, concisely describe its implementation in TinyOS [19] for the MICA2 platform [1], and evaluate its performance through simulation. Results show that our approach provides good delivery and low overhead, and is resilient to connectivity changes in the sensor network, as induced by the temporary standby necessary to preserve the energy of sensor nodes.

Location information is of paramount importance for Wireless Sensor Networks (WSN). The accuracy of collected data can significantly be affected by an imprecise positioning of the event of interest. Despite the importance of location information, real system implementations, that do not use specialized hardware for localization purposes, have not been successful. In this paper, we propose a location estimation scheme that uses a probabilistic approach for estimating the location of a node in a sensor network. Our localization scheme makes use of additional knowledge of topology deployment. We assume a sensor network is deployed in a controlled manner, where the goal of the deployment is to form a grid topology. We evaluate our localization scheme through simulations, showing localization errors as low as 3% of radio range. We outperform similar localization schemes by obtaining 50% less error in localization, when compared to them. We also evaluate our localization solution and the DV-Hop scheme in a real system deployment, obtaining an average error in location of 79% of radio range, outperforming DV-Hop by approximately 40%. We analyze the significant differences in performance between simulations and the real system deployment and stress the importance of further evaluations of real implementations. The result is an effective and realistic protocol that works in an actual system, under certain assumptions, because it exploits deployment information.

We study a class of second order variational inequalities with bilateral constraints. Under certain conditions we show the existence of a unique viscosity solution of these variational inequalities and give a stochastic representation to this solution. As an application, we study a stochastic game with stopping times and show the existence of a saddle point equilibrium.

We study a class of second order variational inequalities with bilateral constraints. Under certain conditions we show the existence of a unique viscosity solution of these variational inequalities and give a stochastic representation to this solution. As an application, we study a stochastic game with stopping times and show the existence of a saddle point equilibrium.

The paper presents a probabilistic-based methodology for the assessment of a pipeline containing internal corrosion defects. Two different models have been used to predict the future CO 2 corrosion rates namely a linear growth and the deWaard-Milliams models. A probabilistic approach is used to analyse the behaviour of corrosion data obtained from in-line intelligent (ILI) pigging inspections. The outcomes are parameters represented by their corresponding statistical distribution. Due to the availability of these statistical parameters, a Monte Carlo simulation is used to calculate the probability of failure of the pipeline due to bursting failure. The existence of corrosion may reduce the maximum capacity of the pipe, as such causing leakage and bursting when the operational pressure supersedes its threshold. From the analysis of the result, failure probability based on theoretical linear growth model exhibit slightly longer lifetime of the pipeline with three years interval compared to deWaard-Milliams model. This is due to higher mean value of corrosion growth rate estimated using the empirical deWaard-Milliams model. Both results are very useful in prolonging the lifetime of pipelines by having knowledge of the past to schedule the future maintenance work.

ABSTRACTThe paper discusses the role of George L.S. Shackle in fostering an unconventional approach to individual decision making. Up until the early 1970s Shackle was the single critic of the probabilistic approach to decision making who proposed an alternative formal corpus for dealing with uncertainty. The main aim of the paper is to analyse Shackle's non‐probabilistic conceptualization of individual decisions under uncertainty from a specific viewpoint, namely that of a possible connection between his theory and one of the most interesting recent approaches to decision under uncertainty, the so‐called non‐additive probability approach of Gilboa and Schmeidler. The paper shows that these developments in modern decision theory take Shackle's issue seriously and confirm that the reliance of strict Bayesian theory on probabilistic judgements based on point‐probability estimates, a reliance that Shackle intended to oppose, is untenable. Non‐additive decision theory also provi...

This paper argues that Ellsberg's and Shackle's frameworks for discussing the limits of the (subjective) probabilistic approach to decision theory are not as different as they may appear. To stress the common elements in their theories Keynes's Treatise on Probability provides an essential starting point. Keynes's rejection of well-defined probability functions, and of maximisation as a guide to human conduct, is shown to imply a reconsideration of what probability theory can encompass that is in the same vein of Ellsberg's and Shackle's concern in the years of the consolidation of Savage's new probabilistic mainstream. The parallel between Keynes and the two decision theorists is drawn by means of a particular assessment of Shackle's theory of decision, namely, it is interpreted in the light of Ellsberg's doctoral dissertation. In this thesis, published only as late as 2001, Ellsberg developed the details and devised the philosophical background of his criticism of Savage as first put forward in the famed 1961 QJE article. The paper discusses the grounds on which the ambiguity surrounding the decision maker in Ellsberg's urn experiment can be deemed analogous to the uncertainty faced by Shackle's entrepreneur taking "unique decisions." The paper argues also that the insights at the basis of the work of both Shackle and Ellsberg, as well as the criteria for decision under uncertainty they put forward, are relevant to understand the development of modern decision theory.

Summary A wide variety of similarity indices for comparing two assemblages based on species incidence (i.e., presence/absence) data have been proposed in the literature. These indices are generally based on three simple incidence counts: the number of species shared by two assemblages and the number of species unique to each of them. We provide a new probabilistic derivation for any incidence‐based index that is symmetric (i.e., the index is not affected by the identity ordering of the two assemblages) and homogeneous (i.e., the index is unchanged if all counts are multiplied by a constant). The probabilistic approach is further extended to formulate abundance‐based indices. Thus any symmetric and homogeneous incidence index can be easily modified to an abundance‐type version. Applying the Laplace approximation formulas, we propose estimators that adjust for the effect of unseen shared species on our abundance‐based indices. Simulation results show that the adjusted estimators signi...

We introduce a new approach for establishing fixed-parameter tractability of problems parameterized above tight lower bounds. To illustrate the approach we consider three problems of this type of unknown complexity that were introduced by Mahajan, Raman and Sikdar (J. Comput. Syst. Sci. 75, 2009). We show that a generalization of one of the problems and non-trivial special cases of the other two are fixed-parameter tractable.

A model, based on detailed descriptions of spatial configuration and a probabilistic approach to the user's choice, is proposed to measure the relationship between demand and supply locations in urban local systems. According to this model, the articulation of the public space grid, associated to the uneven distribution of facilities, generates a powered supply network to which demand locations are related. Choice, as well as demand satisfaction, will then be a function of the relative position (centrality) and attractiveness of supply locations. The model gives a simultaneous account of the spatial opportunity of demand and the spatial convergence of supply. Concurrently it can offer a picture of the stability of space in terms of possible land-use changes.

Recent advances in air traffic Communication Navigation and Surveillance (CNS) have encouraged investigations into the concept following which Air Traffic Control functions can be delegated to the flight deck, allowing more freedom of movement to airspace users. In late 1995, an initiative, known under the project name FREER, for Free-Route Experimental Encounter Resolution, was introduced at EUROCONTROL to investigate the feasibility of this concept. In this paper, we present the initial results obtained from the Autonomous Aircraft Operations study (FREER-1) that targets full delegation of ATC to aircraft operating in lowdensity airspace. Specific issues of Autonomous Aircraft Operations (AAO) supporting free-route, free flight and userpreferred routing are discussed. A description of the current prototype illustrating the Airborne Interactive Conflict Resolution Advisory service is included. Airspace User Autonomy Degree of Delegation Centralized Control (G)