Archives for 2014

Today I read a paper titled “A Parameterized Centrality Metric for Network Analysis”

The abstract is:
A variety of metrics have been proposed to measure the relative importance of nodes in a network

One of these, alpha-centrality [Bonacich, 2001], measures the number of attenuated paths that exist between nodes

We introduce a normalized version of this metric and use it to study network structure, specifically, to rank nodes and find community structure of the network

Specifically, we extend the modularity-maximization method [Newman and Girvan, 2004] for community detection to use this metric as the measure of node connectivity

Normalized alpha-centrality is a powerful tool for network analysis, since it contains a tunable parameter that sets the length scale of interactions

By studying how rankings and discovered communities change when this parameter is varied allows us to identify locally and globally important nodes and structures

We apply the proposed method to several benchmark networks and show that it leads to better insight into network structure than alternative methods

Today I read a paper titled “Dynamic Multi-Vehicle Routing with Multiple Classes of Demands”

The abstract is:
In this paper we study a dynamic vehicle routing problem in which there are multiple vehicles and multiple classes of demands

Demands of each class arrive in the environment randomly over time and require a random amount of on-site service that is characteristic of the class

To service a demand, one of the vehicles must travel to the demand location and remain there for the required on-site service time

The quality of service provided to each class is given by the expected delay between the arrival of a demand in the class, and that demand’s service completion

The goal is to design a routing policy for the service vehicles which minimizes a convex combination of the delays for each class

First, we provide a lower bound on the achievable values of the convex combination of delays

Then, we propose a novel routing policy and analyze its performance under heavy load conditions (i.e., when the fraction of time the service vehicles spend performing on-site service approaches one)

The policy performs within a constant factor of the lower bound (and thus the optimal), where the constant depends only on the number of classes, and is independent of the number of vehicles, the arrival rates of demands, the on-site service times, and the convex combination coefficients

Today I read a paper titled “Stochastic Surveillance Strategies for Spatial Quickest Detection”

The abstract is:
We design persistent surveillance strategies for the quickest detection of anomalies taking place in an environment of interest

From a set of predefined regions in the environment, a team of autonomous vehicles collects noisy observations, which a control center processes

The overall objective is to minimize detection delay while maintaining the false alarm rate below a desired threshold

We present joint (i) anomaly detection algorithms for the control center and (ii) vehicle routing policies

For the control center, we propose parallel cumulative sum (CUSUM) algorithms (one for each region) to detect anomalies from noisy observations

For the vehicles, we propose a stochastic routing policy, in which the regions to be visited are chosen according to a probability vector

We study stationary routing policy (the probability vector is constant) as well as adaptive routing policies (the probability vector varies in time as a function of the likelihood of regional anomalies)

In the context of stationary policies, we design a performance metric and minimize it to design an efficient stationary routing policy

Our adaptive policy improves upon the stationary counterpart by adaptively increasing the selection probability of regions with high likelihood of anomaly

Finally, we show the effectiveness of the proposed algorithms through numerical simulations and a persistent surveillance experiment

Today I read a paper titled “Detecting Separation in Robotic and Sensor Networks”

The abstract is:
In this paper we consider the problem of monitoring detecting separation of agents from a base station in robotic and sensor networks

Such separation can be caused by mobility and/or failure of the agents

While separation/cut detection may be performed by passing messages between a node and the base in static networks, such a solution is impractical for networks with high mobility, since routes are constantly changing

We propose a distributed algorithm to detect separation from the base station

The algorithm consists of an averaging scheme in which every node updates a scalar state by communicating with its current neighbors

We prove that if a node is permanently disconnected from the base station, its state converges to $0$

If a node is connected to the base station in an average sense, even if not connected in any instant, then we show that the expected value of its state converges to a positive number

Therefore, a node can detect if it has been separated from the base station by monitoring its state

The effectiveness of the proposed algorithm is demonstrated through simulations, a real system implementation and experiments involving both static as well as mobile networks

Today I read a paper titled “Brain-Computer Interface Controlled Robotic Gait Orthosis”

The abstract is:
Reliance on wheelchairs after spinal cord injury (SCI) leads to many medical co-morbidities

Treatment of these conditions contributes to the majority of SCI health care costs

Restoring able-body-like ambulation after SCI may reduce the incidence of these conditions, and increase independence and quality of life

However, no biomedical solution exists that can reverse this lost neurological function, and hence novel methods are needed

Brain-computer interface (BCI) controlled lower extremity prosthesis may constitute one such novel approach

One subject with able-body and one with paraplegia due to SCI underwent electroencephalogram (EEG) recording while engaged in alternating epochs of idling and walking kinesthetic motor imagery (KMI)

These data were analyzed to generate an EEG prediction model for online BCI operation

A commercial robotic gait orthosis (RoGO) system (treadmill suspended), was interfaced with the BCI computer

In an online test, the subjects were tasked to ambulate using the BCI-RoGO system when prompted by computerized cues

The performance of this system was assessed with cross-correlation analysis, and omission and false alarm rates

The offline accuracy of the EEG prediction model averaged 86.3%

The cross-correlation between instructional cues and BCI-RoGO walking epochs averaged 0.812 +/- 0.048 (p-value<10^-4)

There were on average 0.8 false alarms per session and no omissions

This is the first time a person with parapegia due to SCI regained basic brain-controlled ambulation, thereby indicating that restoring brain-controlled ambulation is feasible

Future work will test this system in a population of individuals with SCI

If successful, this may justify future development of invasive BCI-controlled lower extremity prostheses

This system may also be applied to incomplete SCI to improve neurological outcomes beyond those of standard physiotherapy

Today I read a paper titled “Characterizing and approximating eigenvalue sets of symmetric interval matrices”

The abstract is:
We consider the eigenvalue problem for the case where the input matrix is symmetric and its entries perturb in some given intervals

We present a characterization of some of the exact boundary points, which allows us to introduce an inner approximation algorithm, that in many case estimates exact bounds

To our knowledge, this is the first algorithm that is able to guaran- tee exactness

We illustrate our approach by several examples and numerical experiments

Today I read a paper titled “Detecting Friendship Within Dynamic Online Interaction Networks”

The abstract is:
In many complex social systems, the timing and frequency of interactions between individuals are observable but friendship ties are hidden

Recovering these hidden ties, particularly for casual users who are relatively less active, would enable a wide variety of friendship-aware applications in domains where labeled data are often unavailable, including online advertising and national security

Here, we investigate the accuracy of multiple statistical features, based either purely on temporal interaction patterns or on the cooperative nature of the interactions, for automatically extracting latent social ties

Using self-reported friendship and non-friendship labels derived from an anonymous online survey, we learn highly accurate predictors for recovering hidden friendships within a massive online data set encompassing 18 billion interactions among 17 million individuals of the popular online game Halo: Reach

We find that the accuracy of many features improves as more data accumulates, and cooperative features are generally reliable

However, periodicities in interaction time series are sufficient to correctly classify 95% of ties, even for casual users

These results clarify the nature of friendship in online social environments and suggest new opportunities and new privacy concerns for friendship-aware applications that do not require the disclosure of private friendship information

Today I read a paper titled “A Neural Network Classifier of Volume Datasets”

The abstract is:
Many state-of-the art visualization techniques must be tailored to the specific type of dataset, its modality (CT, MRI, etc.), the recorded object or anatomical region (head, spine, abdomen, etc.) and other parameters related to the data acquisition process

While parts of the information (imaging modality and acquisition sequence) may be obtained from the meta-data stored with the volume scan, there is important information which is not stored explicitly (anatomical region, tracing compound)

Also, meta-data might be incomplete, inappropriate or simply missing

This paper presents a novel and simple method of determining the type of dataset from previously defined categories

2D histograms based on intensity and gradient magnitude of datasets are used as input to a neural network, which classifies it into one of several categories it was trained with

The proposed method is an important building block for visualization systems to be used autonomously by non-experts

The method has been tested on 80 datasets, divided into 3 classes and a “rest” class

A significant result is the ability of the system to classify datasets into a specific class after being trained with only one dataset of that class

Other advantages of the method are its easy implementation and its high computational performance

Today I read a paper titled “Sensor Management: Past, Present, and Future”

The abstract is:
Sensor systems typically operate under resource constraints that prevent the simultaneous use of all resources all of the time

Sensor management becomes relevant when the sensing system has the capability of actively managing these resources; i.e., changing its operating configuration during deployment in reaction to previous measurements

Examples of systems in which sensor management is currently used or is likely to be used in the near future include autonomous robots, surveillance and reconnaissance networks, and waveform-agile radars

This paper provides an overview of the theory, algorithms, and applications of sensor management as it has developed over the past decades and as it stands today

Today I read a paper titled “Robotic Applications in Cardiac Surgery”

The abstract is:
Traditionally, cardiac surgery has been performed through a median sternotomy, which allows the surgeon generous access to the heart and surrounding great vessels

As a paradigm shift in the size and location of incisions occurs in cardiac surgery, new methods have been developed to allow the surgeon the same amount of dexterity and accessibility to the heart in confined spaces and in a less invasive manner

Initially, long instruments without pivot points were used, however, more recent robotic telemanipulation systems have been applied that allow for improved dexterity, enabling the surgeon to perform cardiac surgery from a distance not previously possible

In this rapidly evolving field, we review the recent history and clinical results of using robotics in cardiac surgery

Today I read a paper titled “Analyzing the Social Structure and Dynamics of E-mail and Spam in Massive Backbone Internet Traffic”

The abstract is:
E-mail is probably the most popular application on the Internet, with everyday business and personal communications dependent on it

Spam or unsolicited e-mail has been estimated to cost businesses significant amounts of money

However, our understanding of the network-level behavior of legitimate e-mail traffic and how it differs from spam traffic is limited

In this study, we have passively captured SMTP packets from a 10 Gbit/s Internet backbone link to construct a social network of e-mail users based on their exchanged e-mails

The focus of this paper is on the graph metrics indicating various structural properties of e-mail networks and how they evolve over time

This study also looks into the differences in the structural and temporal characteristics of spam and non-spam networks

Our analysis on the collected data allows us to show several differences between the behavior of spam and legitimate e-mail traffic, which can help us to understand the behavior of spammers and give us the knowledge to statistically model spam traffic on the network-level in order to complement current spam detection techniques

Today I read a paper titled “Design and Construction of a Brain-Like Computer: A New Class of Frequency-Fractal Computing Using Wireless Communication in a Supramolecular Organic, Inorganic System”

The abstract is:
Here, we introduce a new class of computer which does not use any circuit or logic gate

In fact, no program needs to be written: it learns by itself and writes its own program to solve a problem

Godels incompleteness argument is explored here to devise an engine where an astronomically large number of IfThen arguments are allowed to grow by self assembly, based on the basic set of arguments written in the system, thus, we explore the beyond Turing path of computing but following a fundamentally different route adopted in the last half a century old non Turing adventures

Our hardware is a multilayered seed structure

If we open the largest seed, which is the final hardware, we find several computing seed structures inside, if we take any of them and open, there are several computing seeds inside

We design and synthesize the smallest seed, the entire multilayered architecture grows by itself

The electromagnetic resonance band of each seed looks similar, but the seeds of any layer shares a common region in its resonance band with inner and upper layer, hence a chain of resonance bands is formed (frequency fractal) connecting the smallest to the largest seed (hence the name invincible rhythm or Ajeya Chhandam in Sanskrit)

Today I read a paper titled “Assembly and Disassembly Planning by using Fuzzy Logic & Genetic Algorithms”

The abstract is:
The authors propose the implementation of hybrid Fuzzy Logic-Genetic Algorithm (FL-GA) methodology to plan the automatic assembly and disassembly sequence of products

The GA-Fuzzy Logic approach is implemented onto two levels

The first level of hybridization consists of the development of a Fuzzy controller for the parameters of an assembly or disassembly planner based on GAs

This controller acts on mutation probability and crossover rate in order to adapt their values dynamically while the algorithm runs

The second level consists of the identification of theoptimal assembly or disassembly sequence by a Fuzzy function, in order to obtain a closer control of the technological knowledge of the assembly/disassembly process

Two case studies were analyzed in order to test the efficiency of the Fuzzy-GA methodologies

Today I read a paper titled “An Approach For Robots To Deal With Objects”

The abstract is:
Understanding object and its context are very important for robots when dealing with objects for completion of a mission

In this paper, an Affordance-based Ontology (ABO) is proposed for easy robot dealing with substantive and non-substantive objects

An ABO is a machine-understandable representation of objects and their relationships by what it’s related to and how it’s related

By using ABO, when dealing with a substantive object, robots can understand the representation of its object and its relation with other non-substantive objects

When the substantive object is not available, the robots have the understanding ability, in term of objects and their functions to select a non substantive object in order to complete the mission, such as giving raincoat or hat instead of getting stuck due to the unavailability of substantive object, e.g

umbrella

The experiment is done in the Ubiquitous Robotics Technology (u-RT) Space of National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan

Today I read a paper titled “Using virtual human for an interactive customer-oriented constrained environment design”

The abstract is:
For industrial product design, it is very important to take into account assembly/disassembly and maintenance operations during the conceptual and prototype design stage

For these operations or other similar operations in a constrained environment, trajectory planning is always a critical and difficult issue for evaluating the design or for the users’ convenience

In this paper, a customer-oriented approach is proposed to partially solve ergonomic issues encountered during the design stage of a constrained environment

A single objective optimization based method is taken from the literature to generate the trajectory in a constrained environment automatically

A motion capture based method assists to guide the trajectory planning interactively if a local minimum is encountered within the single objective optimization

At last, a multi-objective evaluation method is proposed to evaluate the operations generated by the algorithm

Today I read a paper titled “NL Understanding with a Grammar of Constructions”

The abstract is:
We present an approach to natural language understanding based on a computable grammar of constructions

A “construction” consists of a set of features of form and a description of meaning in a context

A grammar is a set of constructions

This kind of grammar is the key element of Mincal, an implemented natural language, speech-enabled interface to an on-line calendar system

The system consists of a NL grammar, a parser, an on-line calendar, a domain knowledge base (about dates, times and meetings), an application knowledge base (about the calendar), a speech recognizer, a speech generator, and the interfaces between those modules

We claim that this architecture should work in general for spoken interfaces in small domains

In this paper we present two novel aspects of the architecture: (a) the use of constructions, integrating descriptions of form, meaning and context into one whole; and (b) the separation of domain knowledge from application knowledge

We describe the data structures for encoding constructions, the structure of the knowledge bases, and the interactions of the key modules of the system.

Today I read a paper titled “The effects of graphical interface design characteristics on human-computer interaction task efficiency”

The abstract is:
The main objective of this paper was to investigate the effects of a computer screen interface design and its related geometrical characteristics of 36 graphical objects on a user’s task efficiency

A total of 490 subjects took part in laboratory experiments that focused on the direct manipulation of a visual dialogue between a user and a computer

The subjects were asked to select an object from among a group of items randomly placed on the computer screen that were visible exclusively during the visual search process

A model expressing the mean object acquisition time as a function of graphical object size and the configuration was developed and statistically validated

The model showed an influence of geometrical design characteristics of the graphical objects (icons) and their groupings (icon structures) on the observed task efficiency

The reported results can be used at those stages of a software lifecycle that concentrate on prototyping, designing, and implementing graphical solutions for the efficient graphical user-computer interface