Justin Lloyd's Thinkering

Today I read a paper titled “An Approximation Algorithm for Stackelberg Network Pricing”

The abstract is:
We consider the problem of maximizing the revenue raised from tolls set on the arcs of a transportation network, under the constraint that users are assigned to toll-compatible shortest paths.

We first prove that this problem is strongly NP-hard.

We then provide a polynomial time algorithm with a worst-case precision guarantee of ${1/2}\log_2 m_T+1$, where $m_T$ denotes the number of toll arcs.

Finally we show that the approximation is tight with respect to a natural relaxation by constructing a family of instances for which the relaxation gap is reached.

Today I read a paper titled “Virtual Observatory: From Concept to Implementation”

The abstract is:
We review the origins of the Virtual Observatory (VO) concept, and the current status of the efforts in this field.

VO is the response of the astronomical community to the challenges posed by the modern massive and complex data sets.

It is a framework in which information technology is harnessed to organize, maintain, and explore the rich information content of the exponentially growing data sets, and to enable a qualitatively new science to be done with them.

VO will become a complete, open, distributed, web-based framework for astronomy of the early 21st century.

A number of significant efforts worldwide are now striving to convert this vision into reality.

The technological and methodological challenges posed by the information-rich astronomy are also common to many other fields.

We see a fundamental change in the way all science is done, driven by the information technology revolution.

Today I read a paper titled “Optimized Color Gamuts for Tiled Displays”

The abstract is:
We consider the problem of finding a large color space that can be generated by all units in multi-projector tiled display systems.

Viewing the problem geometrically as one of finding a large parallelepiped within the intersection of multiple parallelepipeds, and using colorimetric principles to define a volume-based objective function for comparing feasible solutions, we develop an algorithm for finding the optimal gamut in time O(n^3), where n denotes the number of projectors in the system.

We also discuss more efficient quasiconvex programming algorithms for alternative objective functions based on maximizing the quality of the color space extrema.

Today I read a paper titled “Markerless Human Motion Capture for Gait Analysis”

The abstract is:
The aim of our study is to detect balance disorders and a tendency towards the falls in the elderly, knowing gait parameters.

In this paper we present a new tool for gait analysis based on markerless human motion capture, from camera feeds.

The system introduced here, recovers the 3D positions of several key points of the human body while walking.

Foreground segmentation, an articulated body model and particle filtering are basic elements of our approach.

No dynamic model is used thus this system can be described as generic and simple to implement.

A modified particle filtering algorithm, which we call Interval Particle Filtering, is used to reorganise and search through the model’s configurations search space in a deterministic optimal way.

This algorithm was able to perform human movement tracking with success.

Results from the treatment of a single cam feeds are shown and compared to results obtained using a marker based human motion capture system.