90 research outputs found
Cryptanalysis of an Encryption Scheme Based on Blind Source Separation
Recently Lin et al. proposed a method of using the underdetermined BSS (blind
source separation) problem to realize image and speech encryption. In this
paper, we give a cryptanalysis of this BSS-based encryption and point out that
it is not secure against known/chosen-plaintext attack and chosen-ciphertext
attack. In addition, there exist some other security defects: low sensitivity
to part of the key and the plaintext, a ciphertext-only differential attack,
divide-and-conquer (DAC) attack on part of the key. We also discuss the role of
BSS in Lin et al.'s efforts towards cryptographically secure ciphers.Comment: 8 pages, 10 figures, IEEE forma
Adapting Content Delivery to Limited Resources and Inferred User Interest
This paper discusses adaptation policies for information systems
that are subject to dynamic and stochastic contexts such as mobile
access to multimedia web sites. In our approach, adaptation agents
apply sequential decisional policies under uncertainty. We focus on
the modeling of such decisional processes depending on whether the
context is fully or partially observable. Our case study is a movie
browsing service in a mobile environment that we model by using
Markov decision processes (MDPs) and partially observable MDP
(POMDP). We derive adaptation policies for this service, that take
into account the limited resources such as the network bandwidth. We
further refine these policies according to the partially observable
users' interest level estimated from implicit feedback. Our
theoretical models are validated through numerous simulations
Unsupervised discovery of character dictionaries in animation movies
Automatic content analysis of animation movies can enable an objective understanding of character (actor) representations and their portrayals. It can also help illuminate potential markers of unconscious biases and their impact. However, multimedia analysis of movie content has predominantly focused on live-action features. A dearth of multimedia research in this field is because of the complexity and heterogeneity in the design of animated characters-an extremely challenging problem to be generalized by a single method or model. In this paper, we address the problem of automatically discovering characters in animation movies as a first step toward automatic character labeling in these media. Movie-specific character dictionaries can act as a powerful first step for subsequent content analysis at scale. We propose an unsupervised approach which requires no prior information about the characters in a movie. We first use a deep neural network-based object detector that is trained on natural images to identify a set of initial character candidates. These candidates are further pruned using saliency constraints and visual object tracking. A character dictionary per movie is then generated from exemplars obtained by clustering these candidates. We are able to identify both anthropomorphic and nonanthropomorphic characters in a dataset of 46 animation movies with varying composition and character design. Our results indicate high precision and recall of the automatically detected characters compared to human-annotated ground truth, demonstrating the generalizability of our approach
Interim research assessment 2003-2005 - Computer Science
This report primarily serves as a source of information for the 2007 Interim Research Assessment Committee for Computer Science at the three technical universities in the Netherlands. The report also provides information for others interested in our research activities
Biosignal controlled recommendation in entertainment systems
With the explosive growth of the entertainment contents and the ubiquitous access of them via fixed or mobile computing devices, recommendation systems become essential tools to help the user to find the right entertainment at the right time and location. I envision that by integrating the bio signal input into the recommendation process, it will help the users not only to find interesting contents, but also to increase one’s comfort level by taking into account the biosginal feedback from the users. The goal of this project was to develop a biosignal controlled entertainment recommendation system that increases the user’s comfort level by reducing the level of stress. As the starting point, this project aims to contribute to the field of recommendation systems with two points. The first is the mechanism of embedding the biosignal non-intrusively into the recommendation process. The second is the strategy of the biosignal controlled recommendation to reduce stress. Heart rate controlled in-flight music recommendation is chosen as its application domain. The hypothesis of this application is that, the passenger's heart rate deviates from the normal due to unusual long haul flight cabin environment. By properly designing a music recommendation system to recommend heart rate controlled personalized music playlists to the passenger, the passengers' heart rate can be uplifted, down-lifted back to normal or kept within normal, thus their stress can be reduced. Four research questions have been formulated based on this hypothesis. After the literature study, the project went mainly through three phases: framework design, system implementation and user evaluation to answer these research questions. During the framework design phase, the heart rate was firstly modeled as the states of bradycardia, normal and tachycardia. The objective of the framework is that, if the user's heart rate is higher or lower than the normal heart rate, the system recommends a personalized music playlist accordingly to transfer the user’s heart rate back to normal, otherwise to keep it at normal. The adaptive framework integrates the concepts of context adaptive systems, user profiling, and the methods of using music to adjust the heart rate in a feedback control system. In the feedback loop, the playlists were composed using a Markov decision process. Yet, the framework allows the user to reject the recommendations and to manually select the favorite music items. During this process, the system logs the interactions between the user and the system for later learning the user’s latest music preferences. The designed framework was then implemented with platform independent software architecture. The architecture has five abstraction levels. The lowest resource level contains the music source, the heart rate sensors and the user profile information. The second layer is for resource management. In this layer are the manager components to manage the resources from the first layer and to modulate the access from upper layers to these resources. The third layer is the database, acting as a data repository. The fourth layer is for the adaptive control, which includes the user feedback log, the inference engine and the preference learning component. The top layer is the user interface. In this architecture, the layers and the components in the layers are loosely coupled, which ensures the flexibility. The implemented system was used in the user experiments to validate the hypothesis. The experiments simulated the long haul flights from Amsterdam to Shanghai with the same time schedule as the KLM flights. Twelve subjects were invited to participate in the experiments. Six were allocated to the controlled group and others were allocated to the treatment group. In addition to a normal entertainment system for the control group, the treatment group was also provided with the heart rate controlled music recommendation system. The experiments results validated the hypothesis and answered the research questions. The passenger's heart rate deviates from normal. In our user experiments, the passenger's heart rate was in the bradycardia state 24.6% of time and was in the tachycardia state 7.3% of time. The recommended uplifting music reduces the average bradycardia state duration from 14.78 seconds in the control group to 6.86 seconds in the treatment group. The recommended keeping music increases the average normal state duration from 24.66 seconds in the control group to 29.79 seconds in the treatment group. The recommended down-lifting music reduces the average tachycardia state duration from 13.89 seconds in the control group to 6.53 seconds in the treatment group. Compared to the control group, the stress of the treatment group has been reduced significantly
Language-independent pre-processing of large document bases for text classification
Text classification is a well-known topic in the research of knowledge discovery in
databases. Algorithms for text classification generally involve two stages. The first
is concerned with identification of textual features (i.e. words andlor phrases) that
may be relevant to the classification process. The second is concerned with
classification rule mining and categorisation of "unseen" textual data. The first
stage is the subject of this thesis and often involves an analysis of text that is both
language-specific (and possibly domain-specific), and that may also be
computationally costly especially when dealing with large datasets. Existing
approaches to this stage are not, therefore, generally applicable to all languages. In
this thesis, we examine a number of alternative keyword selection methods and
phrase generation strategies, coupled with two potential significant word list
construction mechanisms and two final significant word selection mechanisms, to
identify such words andlor phrases in a given textual dataset that are expected to
serve to distinguish between classes, by simple, language-independent statistical
properties. We present experimental results, using common (large) textual datasets
presented in two distinct languages, to show that the proposed approaches can
produce good performance with respect to both classification accuracy and
processing efficiency. In other words, the study presented in this thesis
demonstrates the possibility of efficiently solving the traditional text classification
problem in a language-independent (also domain-independent) manner
Adaptive Methods for Color Vision Impaired Users
Color plays a key role in the understanding of the information in computer environments. It
happens that about 5% of the world population is affected by color vision deficiency (CVD),
also called color blindness. This visual impairment hampers the color perception, ending up by
limiting the overall perception that CVD people have about the surrounding environment, no
matter it is real or virtual. In fact, a CVD individual may not distinguish between two different
colors, what often originates confusion or a biased understanding of the reality, including web
environments, whose web pages are plenty of media elements like text, still images, video,
sprites, and so on.
Aware of the difficulties that color-blind people may face in interpreting colored contents,
a significant number of recoloring algorithms have been proposed in the literature with the
purpose of improving the visual perception of those people somehow. However, most of those
algorithms lack a systematic study of subjective assessment, what undermines their validity, not
to say usefulness. Thus, in the sequel of the research work behind this Ph.D. thesis, the central
question that needs to be answered is whether recoloring algorithms are of any usefulness and
help for colorblind people or not.
With this in mind, we conceived a few preliminary recoloring algorithms that were published in
conference proceedings elsewhere. Except the algorithm detailed in Chapter 3, these conference
algorithms are not described in this thesis, though they have been important to engender
those presented here. The first algorithm (Chapter 3) was designed and implemented for people
with dichromacy to improve their color perception. The idea is to project the reddish hues onto
other hues that are perceived more regularly by dichromat people.
The second algorithm (Chapter 4) is also intended for people with dichromacy to improve their
perception of color, but its applicability covers the adaptation of text and image, in HTML5-
compliant web environments. This enhancement of color contrast of text and imaging in web
pages is done while keeping the naturalness of color as much as possible. Also, to the best of our
knowledge, this is the first web recoloring approach targeted to dichromat people that takes
into consideration both text and image recoloring in an integrated manner.
The third algorithm (Chapter 5) primarily focuses on the enhancement of some of the object
contours in still images, instead of recoloring the pixels of the regions bounded by such contours.
Enhancing contours is particularly suited to increase contrast in images, where we find adjacent
regions that are color indistinguishable from dichromat’s point of view. To our best knowledge,
this is one of the first algorithms that take advantage of image analysis and processing techniques
for region contours.
After accurate subjective assessment studies for color-blind people, we concluded that the CVD
adaptation methods are useful in general. Nevertheless, each method is not efficient enough to
adapt all sorts of images, that is, the adequacy of each method depends on the type of image
(photo-images, graphical representations, etc.).
Furthermore, we noted that the experience-based perceptual learning of colorblind people
throughout their lives determines their visual perception. That is, color adaptation algorithms must satisfy requirements such as color naturalness and consistency, to ensure that dichromat
people improve their visual perception without artifacts. On the other hand, CVD adaptation
algorithms should be object-oriented, instead of pixel-oriented (as typically done), to select
judiciously pixels that should be adapted. This perspective opens an opportunity window for
future research in color accessibility in the field of in human-computer interaction (HCI).A cor desempenha um papel fundamental na compreensão da informação em ambientes computacionais.
Porém, cerca de 5% da população mundial é afetada pela deficiência de visão de
cor (ou Color Vision Deficiency (CVD), do Inglês), correntemente designada por daltonismo. Esta
insuficiência visual dificulta a perceção das cores, o que limita a perceção geral que os indivíduos
têm sobre o meio, seja real ou virtual. Efetivamente, um indivíduo com CVD vê como iguais
cores que são diferentes, o que origina confusão ou uma compreensão distorcida da realidade,
assim como dos ambientes web, onde existe uma abundância de conteúdos média coloridos,
como texto, imagens fixas e vídeo, entre outros.
Com o intuito de mitigar as dificuldades que as pessoas com CVD enfrentam na interpretação de
conteúdos coloridos, tem sido proposto na literatura um número significativo de algoritmos de
recoloração, que têm como o objetivo melhorar, de alguma forma, a perceção visual de pessoas
com CVD. Porém, a maioria desses trabalhos carece de um estudo sistemático de avaliação
subjetiva, o que põe em causa a sua validação, se não mesmo a sua utilidade. Assim, a principal
questão à qual se pretende responder, como resultado do trabalho de investigação subjacente
a esta tese de doutoramento, é se os algoritmos de recoloração têm ou não uma real utilidade,
constituindo assim uma ajuda efetiva às pessoas com daltonismo.
Tendo em mente esta questão, concebemos alguns algoritmos de recoloração preliminares que
foram publicados em atas de conferências. Com exceção do algoritmo descrito no Capítulo 3,
esses algoritmos não são descritos nesta tese, não obstante a sua importância na conceção
daqueles descritos nesta dissertação. O primeiro algoritmo (Capítulo 3) foi projetado e implementado
para pessoas com dicromacia, a fim de melhorar a sua perceção da cor. A ideia consiste
em projetar as cores de matiz avermelhada em matizes que são melhor percebidos pelas pessoas
com os tipos de daltonismo em causa.
O segundo algoritmo (Capítulo 4) também se destina a melhorar a perceção da cor por parte de
pessoas com dicromacia, porém a sua aplicabilidade abrange a adaptação de texto e imagem,
em ambientes web compatíveis com HTML5. Isto é conseguido através do realce do contraste
de cores em blocos de texto e em imagens, em páginas da web, mantendo a naturalidade da
cor tanto quanto possível. Além disso, tanto quanto sabemos, esta é a primeira abordagem de
recoloração em ambiente web para pessoas com dicromacia, que trata o texto e a imagem de
forma integrada.
O terceiro algoritmo (Capítulo 5) centra-se principalmente na melhoria de alguns dos contornos
de objetos em imagens, em vez de aplicar a recoloração aos pixels das regiões delimitadas por
esses contornos. Esta abordagem é particularmente adequada para aumentar o contraste em
imagens, quando existem regiões adjacentes que são de cor indistinguível sob a perspetiva dos
observadores com dicromacia. Também neste caso, e tanto quanto é do nosso conhecimento,
este é um dos primeiros algoritmos em que se recorre a técnicas de análise e processamento de
contornos de regiões.
Após rigorosos estudos de avaliação subjetiva com pessoas com daltonismo, concluiu-se que os
métodos de adaptação CVD são úteis em geral. No entanto, cada método não é suficientemente
eficiente para todos os tipo de imagens, isto é, o desempenho de cada método depende do tipo de imagem (fotografias, representações gráficas, etc.).
Além disso, notámos que a aprendizagem perceptual baseada na experiência das pessoas daltónicas
ao longo de suas vidas é determinante para perceber aquilo que vêem. Isto significa que os
algoritmos de adaptação de cor devem satisfazer requisitos tais como a naturalidade e a consistência
da cor, de modo a não pôr em causa aquilo que os destinatários consideram razoável
ver no mundo real. Por outro lado, a abordagem seguida na adaptação CVD deve ser orientada
aos objetos, em vez de ser orientada aos pixéis (como tem sido feito até ao momento), de
forma a possibilitar uma seleção mais criteriosa dos pixéis que deverão ser sujeitos ao processo
de adaptação. Esta perspectiva abre uma janela de oportunidade para futura investigação em
acessibilidade da cor no domínio da interacção humano-computador (HCI)
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