Visual representations of isosurfaces are ubiquitous in the scientific and engineering literature. In this paper, we present techniques to assess the behavior of isosurface extraction codes. Where applicable, these techniques allow us to distinguish whether anomalies in isosurface features can be attributed to the underlying physical process or to artifacts from the extraction process. Such scientific scrutiny is at the heart of verifiable visualization - subjecting visualization algorithms to the same verification process that is used in other components of the scientific pipeline. More concretely, we derive formulas for the expected order of accuracy (or convergence rate) of several isosurface features, and compare them to experimentally observed results in the selected codes. This technique is practical: in two cases, it exposed actual problems in implementations. We provide the reader with the range of responses they can expect to encounter with isosurface techniques, both under ""normal operating conditions"" and also under adverse conditions. Armed with this information - the results of the verification process - practitioners can judiciously select the isosurface extraction technique appropriate for their problem of interest...
A focused theme in systems biology is to uncover design principles of biological networks, that is, how specific network structures yield specific systems properties. For this purpose, we have previously developed a reverse engineering procedure to identify network topologies with high likelihood in generating desired systems properties. Our method searches the continuous parameter space of an assembly of network topologies, without enumerating individual network topologies separately as traditionally done in other reverse engineering procedures. Here we tested this CPSS (continuous parameter space search) method on a previously studied problem: the resettable bistability of an Rb-E2F gene network in regulating the quiescence-to-proliferation transition of mammalian cells. From a simplified Rb-E2F gene network, we identified network topologies responsible for generating resettable bistability. The CPSS-identified topologies are consistent with those reported in the previous study based on individual topology search (ITS), demonstrating the effectiveness of the CPSS approach. Since the CPSS and ITS searches are based on different mathematical formulations and different algorithms, the consistency of the results also helps cross-validate both approaches. A unique advantage of the CPSS approach lies in its applicability to biological networks with large numbers of nodes. To aid the application of the CPSS approach to the study of other biological systems...
We increasingly rely on large, complex systems in our daily lives---from the computers that park our cars to the medical devices that regulate insulin levels to the servers that store our personal information in the cloud. As these systems grow, they become too complex for a person to understand, yet it is essential that they are correct. Proof assistants are tools that let us specify properties about complex systems and build, maintain, and check proofs of these properties in a rigorous way. Proof assistants achieve this level of rigor for a wide range of properties by requiring detailed certificates (proofs) that can be easily checked.
In this dissertation, I describe a technique for compositionally building extensible automation within a foundational proof assistant for intensional type theory. My technique builds on computational reflection---where properties are checked by verified programs---which effectively bridges the gap between the low-level reasoning that is native to the proof assistant and the interesting, high-level properties of real systems. Building automation within a proof assistant provides a rigorous foundation that makes it possible to compose and extend the automation with other tools (including humans). However...
Three Dimensional Printing (3DP) is a solid free form fabrication process which enables the construction of parts directly from computer-aided design (CAD) models. In the current process, metal parts are produced by printing a polymer binder into stainless steel powder. The parts are subsequently furnace-treated to debind, lightly sinter, and then infiltrate them with a molten metal alloy. These post-printing processes cause a total linear dimensional change of approximately -1.5 ⁺/â 0.2%. Experiments were conducted to investigate reactive binder systems that would improve the dimensional control of metal parts produced by 3DP. Reactive binders typically require a furnace treatment in order to be activated. To prevent the printed part from deforming before binder activation, the initial furnace treatment is carried out with the part contained in the original powder bed. The binder will remain in the part permanently. Because the part is fired in the powder bed, differentiation between the bound and unbound regions places a limitation on the types of binders that may be used. The three main categories of reactive binders investigated were carbon-based binders, metal salts, and small particles. The carbon-based binders acted to bind the part by enhancing the sintering of the stainless steel powder skeleton (binding shrinkage=0.15% when fired at 800ÌC in argon...
The magnetic behavior of a material is governed by the variation in anisotropy direction from grain to grain as well as the changes in ferromagnetic parameters at grain boundaries and other defect regions. For example, transmission electron microscopy results show that chromium segregation occurs at the grand boundaries in CoCrTa films, which are used in hard disk drives. In this paper, we model the case of two adjacent semi-infinite grains with arbitrary crystalline orientations with respect to each other. A Gaussian distribution is used to model the change in magnetic properties at the interface, and boundary conditions are imposed on the direction of magnetization deep within the grains and at the interface. The effects due to the diffuse interface are included using perturbation theory. The sum of the exchange, anisotropy and Zeeman energies is minimized, and the resulting Euler equation is solved analytically. A profile of the magnetization orientation in an inhomogeneous medium in an applied field is obtained to show the extent of the effects of grain boundary segregation. These results can direct future large-scale computer calculations and media improvement.; by Kristen A. Sunter.; Thesis (S.B.)--Massachusetts Institute of Technology...
The Decision Aids for Tunneling (DAT) allow engineers to simulate tunnel construction considering uncertainties in geology and construction processes for a given tunnel project and to obtain, as a result, distributions of the total cost and duration of tunnel construction. The DAT can be applied to every tunnel situation and can deal with any condition regarding a particular tunnel. The research presented in this thesis demonstrates the applicability and suitability of the DAT for the Sucheon tunnel in Korea. For this study, several developments or modifications of the program, SIMSUPER (the computer code of the DAT) were made and many simulations were run with several case studies and some parametric studies. The different time-cost distributions and other results reflecting differences in tunnel construction were analyzed. A new development of the DAT in form of calendars in SIMSUPER was made to be able to keep track of specific and real calendar dates. This study on the DAT application to the real tunnel project in Korea can be a model for the future DAT applications in tunnel projects and this will also lead and accelerate further applications of the DAT to other tunnel projects.; by Sangyoon Min.; Thesis (S.M.)--Massachusetts Institute of Technology...
Today, we are seeing the beginning of the robotics revolution. In the United States, the company iRobot has developed robots to vacuum the house and scrub the floors. In Japan, Mitsubishi has designed an autonomous robot to live with families, with the ability to take the initiative as well as take commands.2 One of the allures of robotics is the fusion of many academic areas, from mechanical engineering to artificial intelligence. However, this combination of academic fields also leads to the difficulty in teaching robotics. Noticing the future demand for robotics, MIT and other top universities have started teaching undergraduate robotics courses to educate new roboticists. In the fall of 2005, the MIT Computer Science and Artificial Intelligence Lab launched the second part in a two term class, Robotics: Systems and Science II (RSSII). The main goal of this class was to have the students apply all the principles learned over the previous semester on solving a complicated problem. The challenge for the term was to have the robot for the course, SplinterBot, autonomously navigate around the MIT campus and retrieve the plastic bricks scattered around. Once SplinterBot returned to base, it would build a simple structure with the bricks it collected.; by Nicholas Martinez.; Thesis (S.B.)--Massachusetts Institute of Technology...
A supercritical ethane working fluid Brayton power conversion system is evaluated as an alternative to carbon dioxide. The HSC® chemical kinetics code was used to study thermal dissociation and chemical interactions for ethane and other coolants under a variety of conditions. The NIST database was used for reaction rates. Overall results were not conclusive. The supercritical behavior of ethane at high pressures is not well documented, and the recombination rates of its dissociation reactions could prove very important. Ethane is known to crack into ethylene, but computer simulations show that it can, at equilibrium, also form significant amounts of hydrogen and methane. These reactions cracked more than 25% of the ethane above 300°C, even though high (20 MPa) pressure significantly reduced dissociation compared to results at 0.1 MPa. At high pressure it appears that ethane might recombine much faster than it dissociates, which would be highly advantageous. Further research and experimentation is encouraged. Simple experiments should be sufficient to identify the behavior of ethane at high temperatures and pressures. Ethane was calculated to have better heat transfer properties than carbon dioxide. In particular, heat exchanger sizes could be reduced by as much as a factor of three. On the other hand...
This dissertation examined the process of entry into the work of graduates in computer
courses in Goiânia UFG, from a population sample drawn from the graduates of between
2001 and 2010. In order to discern, at least in part, the field of IT professional as well as
understand the reality of this area, aimed to investigate whether the respondents are
employed or not, their career, what kind of activity performed, issues related to the work
itself, the influence of profession on personal life, their perceptions about work s area, and
other factors that made us understand how the city of Goiânia is matched to their interests
and expectations as of computer science workers. Considering that the working computer is
a new profession, it was considered necessary to present relevant historical aspects to
situate this new field, highlighting the changes that have taken place within the capitalist
society and contributed to the consolidation of new ways to work, emphasizing the
profound changes occurring in the late twentieth century, including the context of
technological revolutions in information database that contributed to the development of
computing, information technology and social relationship in society. It is also understood
as necessary for understanding the emergence of the profession of computing in the
The objective of this study was to develop a model to predict transport and fate of gasoline components of environmental concern in the Miami River by mathematically simulating the movement of dissolved benzene, toluene, xylene (BTX), and methyl-tertiary-butyl ether (MTBE) occurring from minor gasoline spills in the inter-tidal zone of the river. Computer codes were based on mathematical algorithms that acknowledge the role of advective and dispersive physical phenomena along the river and prevailing phase transformations of BTX and MTBE. Phase transformations included volatilization and settling. ^ The model used a finite-difference scheme of steady-state conditions, with a set of numerical equations that was solved by two numerical methods: Gauss-Seidel and Jacobi iterations. A numerical validation process was conducted by comparing the results from both methods with analytical and numerical reference solutions. Since similar trends were achieved after the numerical validation process, it was concluded that the computer codes algorithmically were correct. The Gauss-Seidel iteration yielded at a faster convergence rate than the Jacobi iteration. Hence, the mathematical code was selected to further develop the computer program and software. The model was then analyzed for its sensitivity. It was found that the model was very sensitive to wind speed but not to sediment settling velocity. ^ A computer software was developed with the model code embedded. The software was provided with two major user-friendly visualized forms...
With the progress of computer technology, computers are expected to be more intelligent in the interaction with humans, presenting information according to the user's psychological and physiological characteristics. However, computer users with visual problems may encounter difficulties on the perception of icons, menus, and other graphical information displayed on the screen, limiting the efficiency of their interaction with computers. ^ In this dissertation, a personalized and dynamic image precompensation method was developed to improve the visual performance of the computer users with ocular aberrations. The precompensation was applied on the graphical targets before presenting them on the screen, aiming to counteract the visual blurring caused by the ocular aberration of the user's eye. A complete and systematic modeling approach to describe the retinal image formation of the computer user was presented, taking advantage of modeling tools, such as Zernike polynomials, wavefront aberration, Point Spread Function and Modulation Transfer Function. The ocular aberration of the computer user was originally measured by a wavefront aberrometer, as a reference for the precompensation model. The dynamic precompensation was generated based on the resized aberration...
Computer systems increasingly carry out tasks in mixed networks, that is in group settings in which they interact both with other computer systems and with people. Participants in these heterogeneous human-computer groups vary in their capabilities, goals, and strategies; they may cooperate, collaborate, or compete. The presence of people in mixed networks raises challenges for the design and the evaluation of decision-making strategies for computer agents. This paper describes several new decision-making models that represent, learn and adapt to various social attributes that influence people's decision-making and presents a novel approach to evaluating such models. It identifies a range of social attributes in an open-network setting that influence people's decision-making and thus affect the performance of computer-agent strategies, and establishes the importance of learning and adaptation to the success of such strategies. The settings vary in the capabilities, goals, and strategies that people bring into their interactions. The studies deploy a configurable system called Colored Trails (CT) that generates a family of games. CT is an abstract, conceptually simple but highly versatile game in which players negotiate and exchange resources to enable them to achieve their individual or group goals. It provides a realistic analogue to multi-agent task domains...
This paper presents a framework that guides the requirements engineer in the
implementation and execution of an effective requirements generation process.
We achieve this goal by providing a well-defined requirements engineering model
and a criteria based process for optimizing method selection for attendant
activities. Our model, unlike other models, addresses the complete requirements
generation process and consists of activities defined at more adequate levels
of abstraction. Additionally, activity objectives are identified and explicitly
stated - not implied as in the current models. Activity objectives are crucial
as they drive the selection of methods for each activity. Our model also
incorporates a unique approach to verification and validation that enhances
quality and reduces the cost of generating requirements. To assist in the
selection of methods, we have mapped commonly used methods to activities based
on their objectives. In addition, we have identified method selection criteria
and prescribed a reduced set of methods that optimize these criteria for each
activity defined by our requirements generation process. Thus, the defined
approach assists in the task of selecting methods by using selection criteria
to reduce a large collection of potential methods to a smaller...
This work gives an overview of analytic tools for the design, analysis, and
modelling of communication systems which can be described by linear vector
channels such as y = Hx+z where the number of components in each vector is
large. Tools from probability theory, operator algebra, and statistical physics
are reviewed. The survey of analytical tools is complemented by examples of
applications in communications engineering. Asymptotic eigenvalue distributions
of many classes of random matrices are given. The treatment includes the
problem of moments and the introduction of the Stieltjes transform. Free
probability theory, which evolved from non-commutative operator algebras, is
explained from a probabilistic point of view in order to better fit the
engineering community. For that purpose freeness is defined without reference
to non-commutative algebras. The treatment includes additive and multiplicative
free convolution, the R-transform, the S-transform, and the free central limit
theorem. The replica method developed in statistical physics for the purpose of
analyzing spin glasses is reviewed from the viewpoint of its applications in
communications engineering. Correspondences between free energy and mutual
information as well as energy functions and detector metrics are established.
These analytic tools are applied to the design and the analysis of linear
The aim of the FESCA workshop is to bring together both young and senior
researchers from formal methods, software engineering, and industry interested
in the development and application of formal modelling approaches as well as
associated analysis and reasoning techniques with practical benefits for
component-based software engineering.
Component-based software design has received considerable attention in
industry and academia in the past decade. In recent years, with the emergence
of new platforms (such as smartphones), new areas advocating software
correctness along with new challenges have appeared. These include development
of new methods and adapting existing ones to accommodate unique features of the
platforms, such as inherent distribution, openness, and continuous migration.
On the other hand, with the growing power of computers, more and more is
possible with respect to practical applicability of modelling and specification
methods as well as verification tools to real-life software, i.e, to scale to
more complex systems.
FESCA aims to address the open question of how formal methods can be applied
effectively to these new contexts and challenges. The workshop is interested in
both the development and application of formal methods in component-based
development and tries to cross-fertilize their research and application.
From n-Tier client/server applications, to more complex academic Grids, or
even the most recent and promising industrial Clouds, the last decade has
witnessed significant developments in distributed computing. In spite of this
conceptual heterogeneity, Service-Oriented Architectures (SOA) seem to have
emerged as the common underlying abstraction paradigm. Suitable access to data
and applications resident in SOAs via so-called Science Gateways has thus
become a pressing need in various fields of science, in order to realize the
benefits of Grid and Cloud infrastructures. In this context, authors have
consolidated work from three complementary experiences in European projects,
which have developed and deployed large-scale production quality
infrastructures as Science Gateways to support research in breast cancer,
paediatric diseases and neurodegenerative pathologies respectively. In
analysing the requirements from these biomedical applications the authors were
able to elaborate on commonly faced Grid development issues, while proposing an
adaptable and extensible engineering framework for Science Gateways. This paper
thus proposes the application of an architecture-centric Model-Driven
Engineering (MDE) approach to service-oriented developments...
Requirements Engineering Methods (REMs) support Requirements Engineering (RE)
tasks, from elicitation, through modeling and analysis, to validation and
evolution of requirements. Despite the growing interest to design, validate and
teach REMs, it remains unclear what components REMs should have. A
classification framework for REMs is proposed. It distinguishes REMs based on
the domain-independent properties of their components. The classification
framework is intended to facilitate (i) analysis, teaching and extension of
existing REMs, (ii) engineering and validation of new REMs, and (iii)
identifying research challenges in REM design. The framework should help
clarify further the relations between REM and other concepts of interest in and
to RE, including Requirements Problem and Solution, Requirements Modeling
Language, and Formal Method.; Comment: 10 pages, 1 figure
We propose and explore a new paradigm in which every software artifact such
as a class is an intelligent and socially active entity. In this Software
Artifact Choreographed Software Engineering (SACSE) paradigm, humanized
artifacts take the lead and choreograph (socially, in collaboration with other
intelligent software artifacts and humans) automated software engineering
solutions to myriad development and maintenance challenges, including API
migration, reuse, documentation, testing, patching, and refactoring. We discuss
the implications of having social and intelligent software artifacts that guide
their own self-improvement.
Current Internet performs traffic engineering (TE) by estimating traffic
matrices on a regular schedule, and allocating flows based upon weights
computed from these matrices. This means the allocation is based upon a guess
of the traffic in the network based on its history. Information-Centric
Networks on the other hand provide a finer-grained description of the traffic:
a content between a client and a server is uniquely identified by its name, and
the network can therefore learn the size of different content items, and
perform traffic engineering and resource allocation accordingly. We claim that
Information-Centric Networks can therefore provide a better handle to perform
traffic engineering, resulting in significant performance gain.
We present a mechanism to perform such resource allocation. We see that our
traffic engineering method only requires knowledge of the flow size (which, in
ICN, can be learned from previous data transfers) and outperforms a min-MLU
allocation in terms of response time. We also see that our method identifies
the traffic allocation patterns similar to that of min-MLU without having
access to the traffic matrix ahead of time. We show a very significant gain in
response time where min MLU is almost 50% slower than our ICN-based TE method.
Developing CPU architecture is a very complicated, iterative process that requires
significant time and money investments. The motivation for this work is to find ways to
decreases the amount of time and money needed for the development of hardware
The main problem is that it is very difficult to determine the performance of the
architecture, since it is impossible to take any performance measurements untill upon
completion of the development process. Consecutively, it is impossible to improve the
performance of the product or to predict the influence of different parts of the architecture
on the architecture's overall performance. Another problem is that this type of
development does not allow for the developed system to be reconfigured or altered
without complete re-development. .
The solution to the problems mentioned above is the software simulators that allow
researching the architecture before even starting to cut the silicon.. Simultaneous
multithreading (SMT) is a modern approach to CPU design. This technique increases the
system throughput by decreasing both total instruction delay and stall times of the CPU.
The gain in performance of a typical SMT processor is achieved by allowing the
instructions from several threads to be fetched by an operating system into the CPU
simultaneously. In order to function successfully the CPU needs software support.
In modern computer systems the influence of an operating system on overall system
performance can no longer be ignored. It is important to understand that the union of the
CPU and the supporting operating system and their interdependency determines the
overall performance of any computer system. In the system that has been implemented
on hardware level such analysis is impossible...