Gravitational lensing refers to the deflection of light by the gravity of celestial bodies, often predominantly composed of dark matter. Seen through a gravitational lens, the images of distant galaxies appear distorted. A range of mathematical frameworks exist to model the lensing effect, but reconstructing the dark lens mass remains a difficult problem, where different models give different insight. This paper considers the Roulette formalism due to Chris Clarkson, and develops a simulator visualising the lensing effect according to the formalism. The objective is to enhance our understanding of the formalism in order to understand its strengths and limitation with respect to lens-mass modelling.

For many years, NTNU in Ålesund (formerly Aalesund University College) has maintained a close relationship with the maritime industrial cluster, centred in the surrounding geographical region, thus acting as a hub for both education, research, and innovation. Of many common relevant research topics, virtual prototyping is currently one of the most important. In this paper, we describe our first complete version of a generic and modular software framework for intelligent computer-automated product design. We present our framework in the context of design of offshore cranes, with easy extensions to other products, be it maritime or not. Funded by the Research Council of Norway and its Programme for Regional R&D and Innovation (VRI), the work we present has been part of two separate but related research projects (grant nos. 241238 and 249171) in close cooperation with two local maritime industrial partners. We have implemented several software modules that together constitute the framework, of which the most important are a server-side crane prototyping tool (CPT), a client-side web graphical user interface (GUI), and a client-side artificial intelligence for product optimisation (AIPO) module that uses a genetic algorithm (GA) library for optimising design parameters to achieve a crane design with desired performance. Communication between clients and server is achieved by means of the HTTP and WebSocket protocols and JSON as the data format. To demonstrate the feasibility of the fully functioning complete system, we present a case study where our computer-automated design was able to improve the existing design of a real and delivered 50-tonnes, 2.9 million EUR knuckleboom crane with respect to some chosen desired design criteria. Our framework being generic and modular, both clientside and server-side modules can easily be extended or replaced. We demonstrate the feasibility of this concept in an accompanying paper submitted concurrently, in which we create a simple product optimisation client in Matlab that uses readily available toolboxes to connect to the CPT and optimise various crane designs by means of a GA. In addition, our research team is currently developing a winch prototyping tool to which our existing AIPO module can connect and optimise winch designs with only small configuration changes. This work will be published in the near future.

In an accompanying paper submitted concurrently to this conference, we present our first complete version of a generic and modular software framework for intelligent computer-automated product design. The framework has been implemented with a client-server software architecture that automates the design of offshore cranes. The framework was demonstrated by means of a case study where we used a genetic algorithm (GA) to optimise the crane design of a real and delivered knuckleboom crane. For the chosen objective function, the optimised crane design outperformed the real crane. In this paper, we augment our aforementioned case study by implementing a new crane optimisation client in Matlab that uses a GA both for optimising a set of objective functions and for multi-objective optimisation. Communicating with an online crane prototyping tool, the optimisation client and its GA are able to optimise crane designs with respect to two selected design criteria: the maximum safe working load and the total crane weight. Our work demonstrates the modularity of the software framework as well as the viability of our approach for intelligent computer-automated design, whilst the results are valuable for informing future directions of our research.

According to watermark security based on the Kerckhoffs' principle, we should mind that illegal users will be able to access to the host signal which is targeted for embedding in a fingerprinting system. In our system, each user's ID is encoded by a fingerprinting code, and then it is embedded into the host signal employing the obfuscation technique. Considering the operation in the obfuscation technique, we discover that the operation is equivalent to a simple spread spectrum (SS) watermarking method using longer sequences. Its effects are intensively evaluated by simulation in this paper.

Abstract Pseudo-random number generation is a fundamental problem in computer programming. In the case of sequential processing the problem is very well researched, but parallel processing raises new problems whereof far too little is currently understood. Splittable pseudo-random generators (S-PRNG) have been proposed to meet the challenges of parallelism. While applicable to any programming paradigm, they are designed to be particularly suitable for pure functional programming. In this paper, we review and evaluate known constructions of such generators, and we identify flaws in several large classes of generators, including Lehmer trees, the implementation in Haskell's standard library, leapfrog, and subsequencing (substreaming).

A fleet of tugs along the northern Norwegian coast must be dynamically positioned to minimise the risk of oil tanker drifting accidents. We have previously presented a receding horizon genetic algorithm (RHGA) for solving this tug fleet optimisation (TFO) problem. In this paper, we begin by presenting an overview of the TFO problem and the details of the RHGA. Next, we identify and correct a flaw in the original cost function of the RHGA. In addition, we present several new cost functions that can be used for dynamic resource allocation by an algorithm such as the RHGA. In a preliminary simulation study, we correct and extend the simulation scenarios used in our previous work and examine the merit of each of the suggested cost functions. Finally, we discuss the potential for an objective evaluation method for comparing various TFO algorithms and briefly present our TFO simulator.

The main threat against fingerprinting systems is collusion attacks. The attack most commonly assumed in the literature is a combination of averaging the collusion fingerprints and additive noise. In this correspondence, we demonstrate that the recently proposed fingerprinting scheme of Kuribayashi's is very vulnerable to certain nonlinear collusion attacks.

Offshore activity is developing and resulting in new demanding high-risk operations. Operation complexity increases with factors like heavier loads, subsea installations, and arctic waters; operational planning requirements increase as well. Demanding offshore operations are usually planned in detail, where plans may fill several binders, leading to information overload for the ship crews. Extracting critical information becomes a challenge. In some cases, only a basic plan exists, and aborted operations are quite frequent, also where a contingency plan could have enabled recovery. This results in substantial extra costs for the operating company. The industry is facing two key challenges concerning operational planning. One is to develop good planning frameworks, to enable plans with robust risk management and control. This calls for modelling techniques for operational plans. Another is optimal presentation of the plan for each individual crew member, both in the briefing and in the execution phase of the operation. It is important that every individual has easy access to the most relevant and safety critical information for his given role and the current situation, in an easily accessible and comprehensible format. This calls for operational software to support situation-awareness. A fundamental necessity to achieve this is modelling techniques which support a joint understanding of the operation between operational planners, ship crew, software engineers, and ultimately the support software. In this paper we show how to translate hierarchical task analysis (HTA) models into software models and then into situation-aware software prototypes.

We formalize a new attack model for collusion secure codes, incorporating attacks on the underlying watermarking scheme as well as cut-and-paste attacks traditionally considered for collusion secure codes. We use this model to analyze the collusion resistance of two versions of the Tardos code, both for binary and nonbinary alphabets. The model allows us to consider different signal processing attacks on the content, namely the addition of noise and averaging attacks. The latter may result in content segments that have multiple watermarks embedded. We study two versions of the$q$-ary Tardos code in which the accusation method has been modified so as to allow for the detection of multiple symbols in the same content segment. We show that both variants yield efficient codes in the new model, parametrized for realistic attacker strengths.

The Deletion-Insertion Correcting Code construction proposed by Davey and MacKay consists of an inner code that recovers synchronization and an outer code that provides substitution error protection. The inner code uses low-weight codewords which are added (modulo two) to a pilot sequence. The receiver is able to synchronise on the pilot sequence in spite of the changes introduced by the added codeword. The original bit-level formulation of the inner decoder assumes that all bits in the sparse codebook are identically and independently distributed. Not only is this assumption inaccurate, but it also prevents the use of soft a- priori input to the decoder. We propose an alternative symbol-level inner decoding algorithm that takes the actual codebook into account. Simulation results show that the proposed algorithm has an improved performance with only a small penalty in complexity, and it allows other improvements using inner codes with larger minimum distance.

With a digital fingerprinting scheme, a vendor of digital copies of copyrighted material marks each individual copy with a unique fingerprint. If an illegal copy appears, it can be traced back to one or more guilty pirates due to this fingerprint. A coalition of pirates may combine their copies to produce an unauthorized copy with a false, hybrid fingerprint. It is often assumed in the literature that the members of the collusion will make equal contributions to the hybrid fingerprint, because nobody will accept an increased risk of being caught. We argue that no such assumption is validapriori, and we show that a published solution by Sebe and Domingo-Ferrer can be broken by breaking the assumption.

Digital fingerprinting is a forensic method against illegal copying. The distributor marks each individual copy with a unique fingerprint. If an illegal copy appears, it can be traced back to one or more guilty pirates due to this fingerprint. To work against a coalition of several pirates, the fingerprinting scheme must be based on a collusion-secure code. This paper addresses binary collusion-secure codes in the setting of Boneh and Shaw (1995/1998). We prove that the Boneh-Shaw scheme is more efficient than originally proven, and we propose adaptations to further improve the scheme. We also point out some differences between our model and others in the literature.

Collusion-secure codes are used for digital fingerprinting and for traitor tracing. In both cases, the goal is to prevent unauthorised copying of copyrighted material, by tracing at least one guilty user when illegal copies appear. The most well-known collusion-secure code is due to Boneh and Shaw (1995/98). In this paper we improve the decoding algorithm by using soft output from the inner decoder, and we show that this permits using significantly shorter codewords.

We compute the second support weight distribution of the Kasami codes.

Collusion-secure codes are used in digital fingerprinting and traitor tracing. Scattering codes were recently introduced by Sebe and Domingo-Ferrer (2002), and used to contstruct a family of codes allegedly collusion-secure against three pirates. We prove that their codes are insecure against optimal pirate strategies, and we present a new secure construction.

The combinatorial concept of separating systems has numerous applications, such as automata theory, digital fingerprinting, group testing, and hashing. In this correspondence, we derive upper bounds on the size of codes with various separating properties.

Separating codes find applications in many fields including automata theory and digital fingerprinting. It is known that the Kerdock code of sufficient order is (2,1)- and (2,2)-separating, but the separating weight is only known by a lower bound due to Sagalovich. In this correspondence, we prove that the lower bound on the (2,1)-separating weight is met with equality.

We show how to compute the support weight distribution A/sub i//sup r/ for r/spl ges/k-d/sub 2//sup /spl perp//+3, where d/sub 2//sup /spl perp// is the second minimum support weight of a code, provided the weight enumerator of the dual code is known.

The theory of separating systems has been applied in different areas of science and technology such as automata synthesis, technical diagnosis, and authenticating ownership claims. Constructions of (2,2)-separating systems derived from error-correcting codes are given, together with bounds on their parameters based on distance considerations.

The weight of a code is the number of coordinate positions where no codeword is zero. The rth minimum weight d/sub r/ is the least weight of an r-dimensional subcode. Wei and Yang (1993) gave a conjecture about the minimum weights for some product codes. In this article, we find a relation between product codes and the Segre embedding of a pair of projective systems, and we use this to prove the conjecture.