Archives for 2012

Today I read a paper titled “Robustness of the Digital Image Watermarking Techniques against Brightness and Rotation Attack”

The abstract is:
The recent advent in the field of multimedia proposed a many facilities in transport, transmission and manipulation of data.

Along with this advancement of facilities there are larger threats in authentication of data, its licensed use and protection against illegal use of data.

A lot of digital image watermarking techniques have been designed and implemented to stop the illegal use of the digital multimedia images.

This paper compares the robustness of three different watermarking schemes against brightness and rotation attacks.

The robustness of the watermarked images has been verified on the parameters of PSNR (Peak Signal to Noise Ratio), RMSE (Root Mean Square Error) and MAE (Mean Absolute Error).

Today I read a paper titled “Detecting Communities in Tripartite Hypergraphs”

The abstract is:
In social tagging systems, also known as folksonomies, users collaboratively manage tags to annotate resources.

Naturally, social tagging systems can be modeled as a tripartite hypergraph, where there are three different types of nodes, namely users, resources and tags, and each hyperedge has three end nodes, connecting a user, a resource and a tag that the user employs to annotate the resource.

Then, how can we automatically detect user, resource and tag communities from the tripartite hypergraph? In this paper, by turning the problem into a problem of finding an efficient compression of the hypergraph’s structure, we propose a quality function for measuring the goodness of partitions of a tripartite hypergraph into communities.

Later, we develop a fast community detection algorithm based on minimizing the quality function.

We explain advantages of our method and validate it by comparing with various state of the art techniques in a set of synthetic datasets.

Today I read a paper titled “Human expert fusion for image classification”

The abstract is:
In image classification, merging the opinion of several human experts is very important for different tasks such as the evaluation or the training.

Indeed, the ground truth is rarely known before the scene imaging.

We propose here different models in order to fuse the informations given by two or more experts.

The considered unit for the classification, a small tile of the image, can contain one or more kind of the considered classes given by the experts.

A second problem that we have to take into account, is the amount of certainty of the expert has for each pixel of the tile.

In order to solve these problems we define five models in the context of the Dempster-Shafer Theory and in the context of the Dezert-Smarandache Theory and we study the possible decisions with these models.

Today I read a paper titled “Ambient Isotopic Meshing of Implicit Algebraic Surface with Singularities”

The abstract is:
A complete method is proposed to compute a certified, or ambient isotopic, meshing for an implicit algebraic surface with singularities.

By certified, we mean a meshing with correct topology and any given geometric precision.

We propose a symbolic-numeric method to compute a certified meshing for the surface inside a box containing singularities and use a modified Plantinga-Vegter marching cube method to compute a certified meshing for the surface inside a box without singularities.

Nontrivial examples are given to show the effectiveness of the algorithm.

To our knowledge, this is the first method to compute a certified meshing for surfaces with singularities.

Today I read a paper titled “Onboard Flight Control of a Small Quadrotor Using Single Strapdown Optical Flow Sensor”

The abstract is:
This paper considers onboard control of a small-sized quadrotor using a strapdown embedded optical flow sensor which is conventionally used for desktop mice.

The vehicle considered in this paper can carry only few dozen grams of payload, therefore conventional camera-based optical flow methods are not applicable.

We present hovering control of the small-sized quadrotor using a single-chip optical flow sensor, implemented on an 8-bit microprocessor without external sensors or communication with a ground control station.

Detailed description of all the system components is provided along with evaluation of the accuracy.

Experimental results from flight tests are validated with the ground-truth data provided by a high-accuracy reference system.

Today I read a paper titled “Beating Irrationality: Does Delegating to IT Alleviate the Sunk Cost Effect?”

The abstract is:
In this research, we investigate the impact of delegating decision making to information technology (IT) on an important human decision bias – the sunk cost effect.

To address our research question, we use a unique and very rich dataset containing actual market transaction data for approximately 7,000 pay-per-bid auctions.

Thus, unlike previous studies that are primarily laboratory experiments, we investigate the effects of using IT on the proneness to a decision bias in real market transactions.

We identify and analyze irrational decision scenarios of auction participants.

We find that participants with a higher monetary investment have an increased likelihood of violating the assumption of rationality, due to the sunk cost effect.

Interestingly, after controlling for monetary investments, participants who delegate their decision making to IT and, consequently, have comparably lower behavioral investments (e.g., emotional attachment, effort, time) are less prone to the sunk cost effect.

In particular, delegation to IT reduces the impact of overall investments on the sunk cost effect by approximately 50%.

Today I read a paper titled “Multi-Robot Searching Algorithm Using Levy Flight and Artificial Potential Field”

The abstract is:
An efficient search algorithm is very crucial in robotic area, especially for exploration missions, where the target availability is unknown and the condition of the environment is highly unpredictable.

In a very large environment, it is not sufficient to scan an area or volume by a single robot, multiple robots should be involved to perform the collective exploration.

In this paper, we propose to combine bio-inspired search algorithm called Levy flight and artificial potential field method to perform an efficient searching algorithm for multi-robot applications.

The main focus of this work is not only to prove the concept or to measure the efficiency of the algorithm by experiments, but also to develop an appropriate generic framework to be implemented both in simulation and on real robotic platforms.

Several experiments, which compare different search algorithms, are also performed.

Today I read a paper titled “Stealing Reality”

The abstract is:
In this paper we discuss the threat of malware targeted at extracting information about the relationships in a real-world social network as well as characteristic information about the individuals in the network, which we dub Stealing Reality.

We present Stealing Reality, explain why it differs from traditional types of network attacks, and discuss why its impact is significantly more dangerous than that of other attacks.

We also present our initial analysis and results regarding the form that an SR attack might take, with the goal of promoting the discussion of defending against such an attack, or even just detecting the fact that one has already occurred.

Today I read a paper titled “Control of a Lightweight Flexible Robotic Arm Using Sliding Modes”

The abstract is:
This paper presents a robust control scheme for flexible link robotic manipulators, which is based on considering the flexible mechanical structure as a system with slow (rigid) and fast (flexible) modes that can be controlled separately.

The rigid dynamics is controlled by means of a robust sliding-mode approach with wellestablished stability properties while an LQR optimal design is adopted for the flexible dynamics.

Experimental results show that this composite approach achieves good closed loop tracking properties both for the rigid and the flexible dynamics.

Today I read a paper titled “Physical Simulation of Inarticulate Robots”

The abstract is:
In this note we study the structure and the behavior of inarticulate robots.

We introduce a robot that moves by successive revolvings.

The robot’s structure is analyzed, simulated and discussed in detail.

Today I read a paper titled “Inferring Networks of Diffusion and Influence”

The abstract is:
Information diffusion and virus propagation are fundamental processes taking place in networks.

While it is often possible to directly observe when nodes become infected with a virus or adopt the information, observing individual transmissions (i.e., who infects whom, or who influences whom) is typically very difficult.

Furthermore, in many applications, the underlying network over which the diffusions and propagations spread is actually unobserved.

We tackle these challenges by developing a method for tracing paths of diffusion and influence through networks and inferring the networks over which contagions propagate.

Given the times when nodes adopt pieces of information or become infected, we identify the optimal network that best explains the observed infection times.

Since the optimization problem is NP-hard to solve exactly, we develop an efficient approximation algorithm that scales to large datasets and finds provably near-optimal networks.

We demonstrate the effectiveness of our approach by tracing information diffusion in a set of 170 million blogs and news articles over a one year period to infer how information flows through the online media space.

We find that the diffusion network of news for the top 1,000 media sites and blogs tends to have a core-periphery structure with a small set of core media sites that diffuse information to the rest of the Web.

These sites tend to have stable circles of influence with more general news media sites acting as connectors between them.

Today I read a paper titled “Video Stippling”

The abstract is:
In this paper, we consider rendering color videos using a non-photo-realistic art form technique commonly called stippling.

Stippling is the art of rendering images using point sets, possibly with various attributes like sizes, elementary shapes, and colors.

Producing nice stippling is attractive not only for the sake of image depiction but also because it yields a compact vectorial format for storing the semantic information of media.

Moreover, stippling is by construction easily tunable to various device resolutions without suffering from bitmap sampling artifacts when resizing.

The underlying core technique for stippling images is to compute a centroidal Voronoi tessellation on a well-designed underlying density.

This density relates to the image content, and is used to compute a weighted Voronoi diagram.

By considering videos as image sequences and initializing properly the stippling of one image by the result of its predecessor, one avoids undesirable point flickering artifacts and can produce stippled videos that nevertheless still exhibit noticeable artifacts.

To overcome this, our method improves over the naive scheme by considering dynamic point creation and deletion according to the current scene semantic complexity, and show how to effectively vectorize video while adjusting for both color and contrast characteristics.

Furthermore, we explain how to produce high quality stippled “videos” (eg., fully dynamic spatio-temporal point sets) for media containing various fading effects, like quick motions of objects or progressive shot changes.

We report on practical performances of our implementation, and present several stippled video results rendered on-the-fly using our viewer that allows both spatio-temporal dynamic rescaling (eg., upscale vectorially frame rate).

Today I read a paper titled “Accurate 3D maps from depth images and motion sensors via nonlinear Kalman filtering”

The abstract is:
This paper investigates the use of depth images as localisation sensors for 3D map building.

The localisation information is derived from the 3D data thanks to the ICP (Iterative Closest Point) algorithm.

The covariance of the ICP, and thus of the localization error, is analysed, and described by a Fisher Information Matrix.

It is advocated this error can be much reduced if the data is fused with measurements from other motion sensors, or even with prior knowledge on the motion.

The data fusion is performed by a recently introduced specific extended Kalman filter, the so-called Invariant EKF, and is directly based on the estimated covariance of the ICP.

The resulting filter is very natural, and is proved to possess strong properties.

Experiments with a Kinect sensor and a three-axis gyroscope prove clear improvement in the accuracy of the localization, and thus in the accuracy of the built 3D map.

Today I read a paper titled “Infinite Multiple Membership Relational Modeling for Complex Networks”

The abstract is:
Learning latent structure in complex networks has become an important problem fueled by many types of networked data originating from practically all fields of science.

In this paper, we propose a new non-parametric Bayesian multiple-membership latent feature model for networks.

Contrary to existing multiple-membership models that scale quadratically in the number of vertices the proposed model scales linearly in the number of links admitting multiple-membership analysis in large scale networks.

We demonstrate a connection between the single membership relational model and multiple membership models and show on “real” size benchmark network data that accounting for multiple memberships improves the learning of latent structure as measured by link prediction while explicitly accounting for multiple membership result in a more compact representation of the latent structure of networks.

Today I read a paper titled “Dynamic Balance Control of Multi-arm Free-Floating Space Robots”

The abstract is:
This paper investigates the problem of the dynamic balance control of multi-arm free-floating space robot during capturing an active object in close proximity.

The position and orientation of space base will be affected during the operation of space manipulator because of the dynamics coupling between the manipulator and space base.

This dynamics coupling is unique characteristics of space robot system.

Such a disturbance will produce a serious impact between the manipulator hand and the object.

To ensure reliable and precise operation, we propose to develop a space robot system consisting of two arms, with one arm (mission arm) for accomplishing the capture mission, and the other one (balance arm) compensating for the disturbance of the base.

We present the coordinated control concept for balance of the attitude of the base using the balance arm.

The mission arm can move along the given trajectory to approach and capture the target with no considering the disturbance from the coupling of the base.

We establish a relationship between the motion of two arm that can realize the zeros reaction to the base.

The simulation studies verified the validity and efficiency of the proposed control method.

Today I read a paper titled “Detecting Coordination Problems in Collaborative Software Development Environments”

The abstract is:
Software development is rarely an individual effort and generally involves teams of developers collaborating to generate good reliable code.

Among the software code there exist technical dependencies that arise from software components using services from other components.

The different ways of assigning the design, development, and testing of these software modules to people can cause various coordination problems among them.

We claim that the collaboration of the developers, designers and testers must be related to and governed by the technical task structure.

These collaboration practices are handled in what we call Socio-Technical Patterns.

The TESNA project (Technical Social Network Analysis) we report on in this paper addresses this issue.

We propose a method and a tool that a project manager can use in order to detect the socio-technical coordination problems.

We test the method and tool in a case study of a small and innovative software product company.