Visual Cryptography for General Access Structures

A visual cryptography scheme for a set ofnparticipants is a method of encoding a secret imageSIintonshadow images called shares, where each participant in receives one share. Certain qualified subsets of participants can “visually” recover the secret image, but other, forbidden, sets of participants have no information (in an information-theoretic sense) onSI. A “visual” recovery for a setX⊆ consists of xeroxing the shares given to the participants inXonto transparencies, and then stacking them. The participants in a qualified setXwill be able to see the secret image without any knowledge of cryptography and without performing any cryptographic computation. In this paper we propose two techniques for constructing visual cryptography schemes for general access structures. We analyze the structure of visual cryptography schemes and we prove bounds on the size of the shares distributed to the participants in the scheme. We provide a novel technique for realizingkout ofnthreshold visual cryptography schemes. Our construction forkout ofnvisual cryptography schemes is better with respect to pixel expansion than the one proposed by M. Naor and A. Shamir (Visual cryptography,in“Advances in Cryptology—Eurocrypt '94” CA. De Santis, Ed.), Lecture Notes in Computer Science, Vol. 950, pp. 1–12, Springer-Verlag, Berlin, 1995) and for the case of 2 out ofnis the best possible. Finally, we consider graph-based access structures, i.e., access structures in which any qualified set of participants contains at least an edge of a given graph whose vertices represent the participants of the scheme.     

Liquefaction characteristics of some Colombian coals: 1. Reactivity in catalytic hydrogenation

The liquefaction characteristics of two Colombian coal have been investigated using catalysis. Cerrejon coal 81% C (the biggest coal mine in Colombia) and Amaga coal 75% C were treated at different reaction temperatures (380–450 °C) and different reaction times (15–60min). At 425 °C and 60min reaction time the products obtained from both coals using a Ni catalyst were almost 100% soluble in THF. At temperatures lower than 425 °C, the Cerrejon coal is more reactive than the Amaga coal.     

A Cluster-Based Data-Centric Model for Network-Aware Task Scheduling in Distributed Systems

Big Data processing architectures are now widely recognized as one of the most significant innovations in Computing in the last decade. Their enormous potential in collecting and processing huge volumes of data scattered throughout the Internet is opening the door to a new generation of fully distributed applications that, by leveraging the large amount of resources available on the network will be able to cope with very complex problems achieving performances never seen before. However, the Internet is known to have severe scalability limitations in moving very large quantities of data, and such limitations introduce the challenge of making efficient use of the computing and storage resources available on the network, in order to enable data-intensive applications to be executed effectively in such a complex distributed environment. This implies resource scheduling decisions which drive the execution of task towards the data by taking network load and capacity into consideration to maximize data access performance and reduce queueing and processing delays as possible. Accordingly, this work presents a data-centric meta-scheduling scheme for fully distributed Big Data processing architectures based on clustering techniques whose goal is aggregating tasks around storage repositories and driven by a new concept of “gravitational” attraction between the tasks and their data of interest. This scheme will benefit from heuristic criteria based on network awareness and advance resource reservation in order to suppress long delays in data transfer operations and result into an optimized use of data storage and runtime resources at the expense of a limited (polynomial) computational complexity.     

Identifying Quality-Based Requirements

This article proposes a model for identifying quality requirements based on three different views of quality. By specifying quality requirements in this manner, the framework establishes quailty requirements that can be quanitfied and measured as part of an overall quality assurance program. This results in two levels of quality: one at the system level that ensures a quality software product and another at the process level that mitigates project risk.     

Designing Quality Architecture: Incorporating ISO Standards into the Unified Process

Requirements change with the ebbs and flows of a business. Applications must be able to react to changes in the business model and, likewise, their technology platform (i.e., architecture) must be agile. Often, the operations and environment requirements of a system affect the application's ability to be modified quickly. This article presents a methodology that combines ISO standards and UML (Unified Modeling Language) standards. the ISO model is used to identify the quality characteristics for software architecture. These attributes form an evaluation framework. Each functional requirement is defined as a use case model using UML notation. This model is expanded with the specific quality properties required based on the ISO model. the resulting use cases are prioritized on the basis of their architectural impact. With these use cases, several candidate architectures can be identified. Alternatives are compared to the evaluation framework to select one architecture design. A real-time monitoring system is used as a case study to reinforce the methodology introduced in the article.     

Predicting riparian evapotranspiration from MODIS vegetation indices and meteorological data

A vegetation index (VI) model for predicting evapotranspiration (ET) from data from the Moderate Resolution Imaging Spectrometer (MODIS) on the EOS-1 Terra satellite and ground meteorological data was developed for riparian vegetation along the Middle Rio Grande River in New Mexico. Ground ET measurements obtained from eddy covariance towers at four riparian sites were correlated with MODIS VIs, MODIS land surface temperatures (LSTs), and ground micrometeorological data over four years. Sites included two saltcedar (Tamarix ramosissima) and two Rio Grande cottonwood (Populus deltoides ssp. Wislizennii) dominated stands. The Enhanced Vegetation Index (EVI) was more closely correlated (r=0.76) with ET than the Normalized Difference Vegetation Index (NDVI; r=0.68) for ET data combined over sites and species. Air temperature (T_a) measured over the canopy from towers was the meteorological variable that was most closely correlated with ET (r=0.82). MODIS LST data at 1- and 5-km resolutions were too coarse to accurately measure the radiant surface temperature within the narrow riparian corridor; hence, energy balance methods for estimating ET using MODIS LSTs were not successful. On the other hand, a multivariate regression equation for predicting ET from EVI and T_a had an r²=0.82 across sites, species, and years. The equation was similar to VI-ET models developed for crop species. The finding that ET predictions did not require species-specific equations is significant, inasmuch as these are mixed vegetation zones that cannot be easily mapped at the species level.     

Security and privacy issues in the Portable Document Format

The Portable Document Format (PDF) was developed by Adobe in the early nineties and today it is the de-facto standard for electronic document exchange. It allows reliable reproductions of published materials on any platform and it is used by many governmental and educational institutions, as well as companies and individuals. PDF documents are also credited with being more secure than other document formats such as Microsoft Compound Document File Format or Rich Text Format.This paper investigates the Portable Document Format and shows that it is not immune from some privacy related issues that affect other popular document formats. From a PDF document, it is possible to retrieve any text or object previously deleted or modified, extract user information and perform some actions that may be used to violate user privacy. There are several applications of such an issue. One of them is relevant to the scientific community and it pertains to the ability to overcome the blind review process of a paper, revealing information related to the anonymous referee (e.g., the IP address of the referee).     

Thesaurus-based 3D Object Retrieval with Part-in-Whole Matching

Research in content-based 3D retrieval has already started, and several approaches have been proposed which use in different manner a similarity assessment to match the shape of the query against the shape of the objects in the database. However, the success of these solutions are far from the success obtained by their textual counterparts. A major drawback of most existing 3D retrieval solutions is their inability to support partial queries, that is, a query which does not need to be formulated by specifying a whole query shape, but just a part of it, for example a detail of its overall shape, just like documents are retrieved by specifying words and not whole texts. Recently, researchers have focused their investigation on 3D retrieval which is solved by partial shape matching. However, at the extent of our knowledge, there is still no 3D search engine that provides an indexing of the 3D models based on all the interesting subparts of the models. In this paper we present a novel approach to 3D shape retrieval that uses a collection-aware shape decomposition combined with a shape thesaurus and inverted indexes to describe and retrieve 3D models using part-in-whole matching. The proposed method clusters similar segments obtained trough a multilevel decomposition of models, constructing from such partition the shape thesaurus. Then, to retrieve a model containing a sub-part similar to a given query, instead of looking on a large set of subparts or executing partial matching between the query and all models in the collection, we just perform a fast global matching between the query and the few entries in the thesaurus. With this technique we overcame the time complexity problems associated with partial queries in large collections.     

A comparison of formulations and solution methods for the minimum-envy location problem

We consider a discrete facility location problem with a new form of equity criterion. The model discussed in the paper analyzes the case where demand points only have strict preference order on the sites where the plants can be located. The goal is to find the location of the facilities minimizing the total envy felt by the entire set of demand points. We define this new total envy criterion and provide several integer linear programming formulations that reflect and model this approach. The formulations are illustrated by examples. Extensive computational tests are reported, showing the potentials and limits of each formulation on several types of instances. Finally, some improvements for all the formulations previously presented are developed, obtaining in some cases much better resolution times.     

Characterization of mesoscale spatio‐temporal patterns and variability of remotely sensed Chl a and SST in the Interior Sea of Chiloe (41.4–43.5° S)

This study characterizes the spatial and temporal distribution of chlorophyll a (Chl a) and sea surface temperature (SST) in the Interior Sea of Chiloe in Chile at a moderate spatial resolution using SeaWiFS and MODIS‐Aqua time series data from the Goddard Earth Science (GES) Data and Information Services Center (DISC) imported into the GES DISC Interactive Online Visualization and Analysis System (‘Giovanni’). The Interior Sea of Chiloe is home to Chile's salmon farming industry, the world's second largest salmonid producer. This study undertakes the characterization of the main patterns of spatial and temporal variability of Chl a and SST in the Interior Sea of Chiloe using a continuous set of time series ocean colour and SST data. Both Chl a and SST exhibit a marked spatial and temporal distribution, with values being significantly higher in the northern area (41.4–42.7° S; total area 41.4–43.5° S) and during the spring–summer period. Peak Chl a concentrations tend to occur in a temporal interval from October to April (austral spring–austral autumn), whereas monthly averaged peak SST values occur consistently in the month of February (austral summer). Chl a concentrations exhibit strong interannual variations, with monthly averaged peak Chl a concentrations experiencing a twofold increase between the year with the lowest and highest Chl a peak concentration in the time series. Results suggest that at the present scale of analysis two spatial domains can be distinguished, regarding the differential behaviour of SST and Chl a in the northern and southern areas of the Interior Sea of Chiloe. The concurrent analysis of Chl a time series data with accumulated rainfall time series data as a proxy of solar radiation, on the other hand, supports previous hypothesis suggesting solar radiation to be a limiting factor for phytoplankton development in the Interior Sea of Chiloe. The role of geomorphological factors on pattern formation and the results presented in this study in relation to results from seasonal oceanographic cruises in the area are briefly discussed.