287 research outputs found
Recasting Residual-based Local Descriptors as Convolutional Neural Networks: an Application to Image Forgery Detection
Local descriptors based on the image noise residual have proven extremely
effective for a number of forensic applications, like forgery detection and
localization. Nonetheless, motivated by promising results in computer vision,
the focus of the research community is now shifting on deep learning. In this
paper we show that a class of residual-based descriptors can be actually
regarded as a simple constrained convolutional neural network (CNN). Then, by
relaxing the constraints, and fine-tuning the net on a relatively small
training set, we obtain a significant performance improvement with respect to
the conventional detector
A reliable order-statistics-based approximate nearest neighbor search algorithm
We propose a new algorithm for fast approximate nearest neighbor search based
on the properties of ordered vectors. Data vectors are classified based on the
index and sign of their largest components, thereby partitioning the space in a
number of cones centered in the origin. The query is itself classified, and the
search starts from the selected cone and proceeds to neighboring ones. Overall,
the proposed algorithm corresponds to locality sensitive hashing in the space
of directions, with hashing based on the order of components. Thanks to the
statistical features emerging through ordering, it deals very well with the
challenging case of unstructured data, and is a valuable building block for
more complex techniques dealing with structured data. Experiments on both
simulated and real-world data prove the proposed algorithm to provide a
state-of-the-art performance
A semantic methodology for (un)structured digital evidences analysis
Nowadays, more than ever, digital forensics activities are involved in any criminal, civil or military investigation and represent a fundamental tool to support cyber-security.
Investigators use a variety of techniques and proprietary software forensic applications to examine the copy of digital devices, searching hidden, deleted, encrypted, or damaged files or folders. Any evidence found is carefully analysed and documented in a "finding report" in preparation for legal proceedings that involve discovery, depositions, or actual litigation.
The aim is to discover and analyse patterns of fraudulent activities.
In this work, a new methodology is proposed to support investigators during the analysis process, correlating evidences found through different forensic tools.
The methodology was implemented through a system able to add semantic assertion to data generated by forensics tools during extraction processes. These assertions enable more effective access to relevant information and enhanced retrieval and reasoning capabilities
Autoencoder with recurrent neural networks for video forgery detection
Video forgery detection is becoming an important issue in recent years,
because modern editing software provide powerful and easy-to-use tools to
manipulate videos. In this paper we propose to perform detection by means of
deep learning, with an architecture based on autoencoders and recurrent neural
networks. A training phase on a few pristine frames allows the autoencoder to
learn an intrinsic model of the source. Then, forged material is singled out as
anomalous, as it does not fit the learned model, and is encoded with a large
reconstruction error. Recursive networks, implemented with the long short-term
memory model, are used to exploit temporal dependencies. Preliminary results on
forged videos show the potential of this approach.Comment: Presented at IS&T Electronic Imaging: Media Watermarking, Security,
and Forensics, January 201
Guided patch-wise nonlocal SAR despeckling
We propose a new method for SAR image despeckling which leverages information
drawn from co-registered optical imagery. Filtering is performed by plain
patch-wise nonlocal means, operating exclusively on SAR data. However, the
filtering weights are computed by taking into account also the optical guide,
which is much cleaner than the SAR data, and hence more discriminative. To
avoid injecting optical-domain information into the filtered image, a
SAR-domain statistical test is preliminarily performed to reject right away any
risky predictor. Experiments on two SAR-optical datasets prove the proposed
method to suppress very effectively the speckle, preserving structural details,
and without introducing visible filtering artifacts. Overall, the proposed
method compares favourably with all state-of-the-art despeckling filters, and
also with our own previous optical-guided filter
A Hypergraph Data Model for Expert-Finding in Multimedia Social Networks
Online Social Networks (OSNs) have found widespread applications in every area of our life. A large number of people have signed up to OSN for different purposes, including to meet old friends, to choose a given company, to identify expert users about a given topic, producing a large number of social connections. These aspects have led to the birth of a new generation of OSNs, called Multimedia Social Networks (MSNs), in which user-generated content plays a key role to enable interactions among users. In this work, we propose a novel expert-finding technique exploiting a hypergraph-based data model for MSNs. In particular, some user-ranking measures, obtained considering only particular useful hyperpaths, have been profitably used to evaluate the related expertness degree with respect to a given social topic. Several experiments on Last.FM have been performed to evaluate the proposed approach's effectiveness, encouraging future work in this direction for supporting several applications such as multimedia recommendation, influence analysis, and so on
Flood propagation modelling with the Local Inertia Approximation: theoretical and numerical analysis of its physical limitations
Attention of the researchers has increased towards a simplification of the
complete Shallow water Equations called the Local Inertia Approximation (LInA),
which is obtained by neglecting the advection term in the momentum conservation
equation. In the present paper it is demonstrated that a shock is always
developed at moving wetting-drying frontiers, and this justifies the study of
the Riemann problem on even and uneven beds. In particular, the general exact
solution for the Riemann problem on horizontal frictionless bed is given,
together with the exact solution of the non-breaking wave propagating on
horizontal bed with friction, while some example solution is given for the
Riemann problem on discontinuous bed. From this analysis, it follows that
drying of the wet bed is forbidden in the LInA model, and that there are
initial conditions for which the Riemann problem has no solution on smoothly
varying bed. In addition, propagation of the flood on discontinuous sloping bed
is impossible if the bed drops height have the same order of magnitude of the
moving-frontier shock height. Finally, it is found that the conservation of the
mechanical energy is violated. It is evident that all these findings pose a
severe limit to the application of the model. The numerical analysis has proven
that LInA numerical models may produce numerical solutions, which are
unreliable because of mere algorithmic nature, also in the case that the LInA
mathematical solutions do not exist. The applicability limits of the LInA model
are discouragingly severe, even if the bed elevation varies continuously. More
important, the non-existence of the LInA solution in the case of discontinuous
topography and the non-existence of receding fronts radically question the
viability of the LInA model in realistic cases. It is evident that classic SWE
models should be preferred in the majority of the practical applications
Design of a Wearable Healthcare Emergency Detection Device for Elder Persons
Improving quality of life in geriatric patients is related to constant physical activity and fall prevention. In this paper, we propose a wearable system that takes advantage of sensors embedded in a smart device to collect data for movement identification (running, walking, falling and daily activities) of an elderly user in real-time. To provide high efficiency in fall detection, the sensor’s readings are analysed using a neural network. If a fall is detected, an alert is sent though a smartphone connected via Bluetooth. We conducted an experimental session using an Arduino Nano 33 BLE Sense board in inside and outside environments. The results of the experiment have shown that the system is extremely portable and provides high success rates in fall detection in terms of accuracy and loss. © 2022 by the authors. Licensee MDPI, Basel, Switzerland
Polymorphism of postmating reproductive isolation within plant species
Speciation can be viewed as the evolution of reproductive isolation between formerly interbreeding populations. Recent years have seen great advances in our understanding of the genetic mechanisms underlying postmating reproductive isolation during plant speciation. Nevertheless, little is known about the early stages of species divergence and the evolution of reproductive isolation at the within species level. Direct or indirect evidence indicates that intrinsic postzygotic mechanisms are prevalent and often polymorphic among allopatric conspecific populations of plants. We review studies that report direct or indirect evidence for polymorphism of genic (i.e., gene-based) postmating reproductive isolation within species' ranges. Specifically, we focus on three genic mechanisms often held responsible for reproductive isolation between species: Bateson-Dobzhansky-Muller (BDM) incompatibilities and two widespread types of genomic conflict, transmission ratio distortion and cytonuclear interactions. We further highlight the close similarity between reported cases of outbreeding depression among conspecific populations, especially those that correspond to the intrinsic co-adaptation model, and the origin of genetic incompatibilities. This association holds great promise to help improve our understanding of the processes involved in the initial stage of speciation, and it highlights the close (and often overlooked) relationship between evolutionary and conservation biology
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