Actual Domain Research Articles

Level set based topological shape optimization of geometrically nonlinear structures using unstructured mesh

Using hyperelastic materials and unstructured mesh, a level set based topological shape optimization method is developed for geometrically nonlinear structures in total Lagrangian framework. In the level set method, the initial domain is kept fixed and its boundary is represented by an implicit moving boundary embedded in a level set function, which facilitates to handle complicated topological shape changes and eventually leads the initial implicit boundary to an optimal one according to the normal velocity field while both minimizing the objective function of instantaneous structural compliance and satisfying an allowable material volume constraint. In existing level set based methods, an initial reference domain or an ersatz material is employed for the penalization of whole domain to represent the current domain. However, these approaches end up with a convergence difficulty in nonlinear response analysis due to the inaccurate tangent stiffness. To overcome this difficulty, taking advantage of the obtained level set function, the current structural boundary is actually represented using a Delaunay triangulation scheme and a hyperelastic material law is employed to handle the large strain problem. The required velocity field in the actual domain to update the level set equation is determined from the descent direction of Lagrangian derived from optimality conditions. The velocity field outside the actual domain is determined through a velocity extension scheme based on a fast marching method. Since homogeneous material property and actual boundary are utilized, the convergence difficulty is significantly relieved.

Simulation of geological domains using the plurigaussian model: New developments and computer programs

The plurigaussian model is currently used for simulating geological domains (facies) in petroleum reservoirs and mineral deposits, with the aim of assessing the uncertainty in the domain boundaries and of improving the geological controls in the characterization of quantitative attributes. This paper discusses the main aspects of the model and provides a set of computer programs to perform its inference and conditional simulation. Two types of conditioning information are allowed: hard data for which one has an exact knowledge of the actual domain at sample locations, and soft data consisting of inequality constraints on the local domain proportions (probabilities of occurrence) at control points chosen by the mining or reservoir geologist. An application to a Chilean porphyry copper deposit is finally presented, in which three Gaussian fields are used to simulate the spatial distribution of five mineralogical domains: gravels, leached capping, oxides, primary and secondary sulfides. The model is constructed so as to honor the topological contacts between mineralogical domains, their spatial continuity, the information logged at exploration drill holes, as well as the vertical proportion curves that indicate the mineralization profile with depth.

To Restore American Democracy: Political Education and the Modern University and Power to the People: Teaching Political Philosophy in Skeptical Times

To Restore American Democracy: Political Education and the Modern University. Edited by Robert E. Calvert. Lanham, MD: Rowman & Littlefield, 2006. 288p. 28.95 paper. Power to the People: Teaching Political Philosophy in Skeptical Times. By Avner de-Shalit. Lanham, MD: Lexington Books, 2006. 224p. 29.95 paper. The authors of these two books are concerned with a similar question, namely, how can scholars support their students in becoming engaged citizens? Political theorists and philosophers often wrestle with this question as a personal and professional quandary. Many researchers, particularly those whose scholarship is concerned with political questions, wonder to what extent their ideas relate to political reality in a practical way. Can ideas influence, even alter, the processes or norms of behavior in the actual political domain? If what we do is political theory or philosophy, what is political about it? Both books reviewed here grapple with these questions in the context of teaching in higher education institutions.

Multistyle classification of speech under stress using feature subset selection based on genetic algorithms

The determination of an emotional state through speech increases the amount of information associated with a speaker. It is therefore important to be able to detect and identify a speaker’s emotional state or state of stress. Various techniques are used in the literature to classify emotional/stressed states on the basis of speech, often using different speech feature vectors at the same time. This study proposes a new feature vector that will allow better classification of emotional/stressed states. The components of the feature vector are obtained from a feature subset selection procedure based on genetic algorithms. A good discrimination between neutral, angry, loud and Lombard states for the simulated domain of the Speech Under Simulated and Actual Stress (SUSAS) database and between neutral and stressed states for the actual domain of the SUSAS database is obtained.

Flow Control Through the Use of Topography.

In this work, optimal shaft shapes for flow in the annular space between a rotating shaft with axially-periodic radius and a fixed coaxial outer circular cylinder, are investigated. Axisymmetric steady flows in this geometry are determined by solving the full Navier-Stokes equations in the actual domain. A measure of the flow field, a weighted convex combination of the volume averaged square of the L2-norm of the velocity and vorticity vectors, is employed. It has been demonstrated that boundary shape can be used to influence the characteristics of the flow field, such as its velocity component distribution, kinetic energy, or even vorticity. This ability to influence flow fields through boundary shape may be employed to improve microfluidic mixing or, possibly, to minimize shear in biological applications.

WORKING KNOWLEDGE MINING BY PRINCIPLES FOR DEEP KNOWLEDGE

We usually use a set of ideas, thinking paradigms and judgment rules, including alternatives, criteria, outcomes, preferences, to make decision. This set, known as actual domain (working knowledge) of habitual domain, will be stabilized over time unless extraordinary events occur. As such, our working knowledge cannot be broad and deep. Inevitably, we could get into decision traps, which lead us to making wrong decision or solving wrong problems. The actual domain is only a small part of our potential domain, the collection of all thoughts, ideas, thinking paradigms, etc. that have ever been encoded in our brain. In this paper, we will describe nine principles for deep knowledge, so that, we could expand and enrich our working knowledge by utilizing the potential domains of ourselves and other participants in the decision making. As a consequence, good ideas for solving challenging decision problems can be obtained or created. These principles are: The deep and down principle, the alternating principle, the contrasting and complementing principle, the revolving and cycling principle, the inner connection principle, the changing and transforming principle, the contradiction principle, the cracking and ripping principle, the void principle.

From Parallel Universes to Possible Worlds: Ontological Pluralism in Physics, Narratology, and Narrative

This essay explores how theoretical physics, narratology, and narrative itself deal with the idea that reality consists of a plurality of worlds. In physics, the existence of parallel universes has been postulated on the cosmic level to describe what lies on the other side of black holes and, on the level of subatomic particles, to avoid the paradoxes of quantum mechanics. In narratology, the philosophical idea of a plurality of possible worlds and the contrast between the actual and the possible provide a model of the cognitive pattern into which readers organize information in order to interpret it as a story. But the many-worlds interpretation of physics and the possible worlds (PW) model of narrative differ in their conception of the ontological status of the multiple worlds: in physics they are all actual, while narrative theory stresses the contrast between actuality and mere possibility. This does not mean that the PW model is incompatible with the many-worlds cosmology proposed by physics: faced with a narrative that presents multiple realities as existing objectively, the theory would simply claim that the actual domain is made up of a number of different worlds and that the distinction actual/nonactual repeats itself within each of these parts. The last section of the essay explores what it takes for a narrative to impose a many-worlds cosmology, distinguishing these narratives from other texts that present contradictory versions of facts and situating them with respect to three types of story common in fantasy and science fiction: the narrative of transworld exploration, the narrative of alternate history, and the time-travel narrative.

Discovering the events expert practitioners extract from dynamic data streams: the modified unit marking technique

One of the cornerstones of expert performance in complex domains is the ability to perceive problem situations in terms of their task-relevant semantic properties. One such class of properties consists of phenomena that are defined in terms of patterns of change over time, i.e., events. A basic pre-requisite for working towards tools to support event recognition is a method for understanding the events that expert practitioners find meaningful in a given field of practice. In this article we present the modified unit marking procedure (mUMP), a technique adapted from work on social perception to facilitate identification of the meaningful phenomena which observers attend to in a dynamic data array. The mUMP and associated data analysis techniques are presented with examples from a first of a kind study where they were used to elicit and understand the events practitioners found meaningful in a scenario from an actual complex work domain.

Stability of the charged surface of a liquid dielectric

A theory is proposed for the onset of instability of the interface between two liquid dielectrics in the presence of an external electric field normal to that interface. The details of the critical conditions of instability are investigated as functions of the external parameters of the problem: the ratio ε=ε1∕ε2 of the dielectric constants ε1 and ε2 of the two media, the thickness of the liquid films found in contact, etc. In particular, a quantitative difference in the structure of the corrugation of the liquid interface is noted for different ε. In the case of finite values of ε the critical value of the corrugation period remains finite. However, if ε→0 (which corresponds to an infinite conductivity of one of the media) the corrugation period also grows without bound. The possibility of reconstruction of the liquid interface under supercritical conditions is demonstrated (the appearance of mechanically equilibrium corrugation of the liquid interface with a corrugation amplitude that depends on the degree of supercriticality, i.e., the excess of the electric field above the critical value). The existence of two regimes of reconstruction is pointed out: “soft” and “hard,” which are realized under definite relationships among the external parameters of the problem. The details are discussed for the “soft” reconstruction, where the formalism used has an actual domain of applicability. It is noted that manipulations with the parameter ε=ε1∕ε2 in the problem under discussion are qualitatively equivalent to variation of the degree of occupation δ of the surface of the cryogenic liquid by charged particles (electrons or ions) from its zero value (the case of a charge-free liquid surface) up to its maximum value δ=1, when the general problem gives answers that are characteristic for the development of instability of the free interface of a metallic liquid.

Validation of Group Domain Score Estimates Using a Test of Domain

Domain scores have been proposed as a user‐friendly way of providing instructional feedback about examinees' skills. Domain performance typically cannot be measured directly; instead, scores must be estimated using available information. Simulation studies suggest that IRT‐based methods yield accurate group domain score estimates. Because simulations can represent best‐case scenarios for methodology, it is important to verify results with a real data application. This study administered a domain of elementary algebra (EA) items created from operational test forms. An IRT‐based group‐level domain score was estimated from responses to a subset of taken items (comprised of EA items from a single operational form) and compared to the actual observed domain score. Domain item parameters were calibrated both using item responses from the special study and from national operational administrations of the items. The accuracy of the domain score estimates were evaluated within schools and across school sizes for each set of parameters. The IRT‐based domain score estimates typically were closer to the actual domain score than observed performance on the EA items from the single form. Previously simulated findings for the IRT‐based domain score estimation procedure were supported by the results of the real data application.

GDM: A New Graph Based Data Model Using Functional Abstractionx

In this paper, a Graph-based semantic Data Model (GDM) is proposed with the primary objective of bridging the gap between the human perception of an enterprise and the needs of computing infrastructure to organize information in some particular manner for efficient storage and retrieval. The Graph Data Model (GDM) has been proposed as an alternative data model to combine the advantages of the relational model with the positive features of semantic data models. The proposed GDM offers a structural representation for interacting to the designer, making it always easy to comprehend the complex relations amongst basic data items. GDM allows an entire database to be viewed as a Graph (V, E) in a layered organization. Here, a graph is created in a bottom up fashion where V represents the basic instances of data or a functionally abstracted module, called primary semantic group (PSG) and secondary semantic group (SSG). An edge in the model implies the relationship among the secondary semantic groups. The contents of the lowest layer are the semantically grouped data values in the form of primary semantic groups. The SSGs are nothing but the higher-level abstraction and are created by the method of encapsulation of various PSGs, SSGs and basic data elements. This encapsulation methodology to provide a higher-level abstraction continues generating various secondary semantic groups until the designer thinks that it is sufficient to declare the actual problem domain. GDM, thus, uses standard abstractions available in a semantic data model with a structural representation in terms of a graph. The operations on the data model are formalized in the proposed graph algebra. A Graph Query Language (GQL) is also developed, maintaining similarity with the widely accepted user-friendly SQL. Finally, the paper also presents the methodology to make this GDM compatible with the distributed environment, and a corresponding query processing technique for distributed environment is also suggested for the sake of completeness.

Prediction of aerosol deposition in [formula omitted] bends using LES and an efficient Lagrangian tracking method

Aiming at the better prediction of pharmaceutical aerosol deposition in extrathoracic airways, a simpler test case, namely a 90 ∘ bend flow (tubular cross-section) laden with monodisperse particles, is adopted here and studied numerically. The continuous phase is calculated using a large-eddy simulation technique along with a finite-volume method for block-structured curvilinear grids. The particulate phase is simulated using a Lagrangian approach where hundred thousands of individual monodisperse particles with varying particle diameters are released and tracked throughout the computational domain. To allow such a large number of particles, a highly efficient tracking algorithm is applied, where particle paths are predicted in an orthogonal computational domain, avoiding time-consuming search algorithm, normally required when particles are tracked in the actual physical domain of a curvilinear body-fitted block-structured grid. Both simulation algorithms, for the continuous and particulate phases, are completely parallelized using domain decomposition. Additionally, the in-house code applied supports vector processing allowing efficient usage of nearly all kinds of high-performance architectures. Two different Reynolds numbers Re D are considered where Re D is based on the bend diameter and mean flow velocity. The first case is within the laminar regime at Re D = 1000 and serves for the purpose of verification and validation. The second, more challenging case comprises the turbulent regime at Re D = 10 , 000 , which is the intrinsic objective of the present study. Depending on the Stokes number of the particles, 0.001 ⩽ St ⩽ 1.5 , and the releasing locations at the entrance of the bend, the particles will either deposit on the wall or penetrate and exit the computational domain. Simulation results of aerosol deposition efficiency, over the entire range of particle diameters considered here, show an excellent agreement when compared to experimental values obtained by Pui, Romay-Novas, and Liu [(1987). Experimental study of particle deposition in bends of circular cross-section. Aerosol Science and Technology, 7, 301].

Computational Mesh Generation for Vascular Structures with Deformable Surfaces

Computational blood flow and vessel wall mechanics simulations for vascular structures are becoming an important research tool for patient-specific surgical planning and intervention. An important step in the modelling process for patient-specific simulations is the creation of the computational mesh based on the segmented geometry. Most known solutions either require a large amount of manual processing or lead to a substantial difference between the segmented object and the actual computational domain. We have developed a chain of algorithms that lead to a closely related implementation of image segmentation with deformable models and 3D mesh generation. The resulting processing chain is very robust and leads both to an accurate geometrical representation of the vascular structure as well as high quality computational meshes. The chain of algorithms has been tested on a wide variety of shapes. A benchmark comparison of our mesh generation application with five other available meshing applications clearly indicates that the new approach outperforms the existing methods in the majority of cases.

A mapping technique for numerical computations of bed evolutions

Free surface flow is one of the most difficult problems in engineering to be solved, since velocity and pressure fields depend on the free surface. On the other hand, the position of the free surface is unknown previously. Furthermore, the boundary condition on the free surface is expressed by a complicated equation. In an alluvial stream, where the boundaries of the domain are not fixed, addition of free surface at the bed will increase this difficulty. A domain mapping technique is developed in this paper to study the bed evolutions. The flow is considered 2D, choosing two coordinates in streamwise and upward directions. With a proper transformation, the hydrodynamics and sediment transport governing equations in irregular domain will be mapped into a simple rectangular one. The new domain can be discretize by finite elements. The transformed governing equations are solved to obtain desired variables in the mapped domain. With a proper transformation, there is no need of inverse mapping to obtain the free water surface profile and bedform evolution and migration in the actual domain. The model has been applied to streams with movable bed and the results show a good agreement with the experimental experiences.

A reduced basis element method for the steady Stokes problem: Application to hierarchical flow systems

The reduced basis element method is a new approach for approximating the solution of problems described by partial differential equations. The method takes its roots in domain decomposition methods and reduced basis discretizations (Fink & Rheinboldt (1983), Noor & Peters (1980), Prud’homme et al. (2002)), and its applications extend to, for example, control and optimization problems. The basic idea is to first decompose the computational domain into a series of subdomains that are similar to a few reference domains (or generic computational parts). Associated with each reference domain are precomputed solutions corresponding to the same governing partial differential equation, but solved for different choices of some underlying parameter. In this work, the parameters are representing the geometric shape associated with a computational part. The approximation corresponding to a new shape is then taken to be a linear combination of the precomputed solutions, mapped from the reference domain for the part to the actual domain. We extend earlier work (Maday & Ronquist (2002), Maday & Ronquist (2004)) in this direction to solve incompressible fluid flow problems governed by the steady Stokes equations. Particular focus is given to constructing the basis functions, to the mapping of the velocity fields, to satisfying the inf-sup condition, and to “gluing” the local solutions together in the multidomain case (Belgacem et al. (2000)). We also demonstrate an algorithm for choosing the most efficient precomputed solutions. Two-dimensional examples are presented for pipes, bifurcations, and couplings of pipes and bifurcations in order to simulate hierarchical flow systems.

Structure of the Unphosphorylated STAT5a Dimer*

STAT proteins have the function of signaling from the cell membrane into the nucleus, where they regulate gene transcription. Latent mammalian STAT proteins can form dimers in the cytoplasm even before receptor-mediated activation by specific tyrosine phosphorylation. Here we describe the 3.21-A crystal structure of an unphosphorylated STAT5a homodimer lacking the N-terminal domain as well as the C-terminal transactivation domain. The overall structure of this fragment is very similar to phosphorylated STATs. However, important differences exist in the dimerization mode. Although the interface between phosphorylated STATs is mediated by their Src-homology 2 domains, the unphosphorylated STAT5a fragment dimerizes in a completely different manner via interactions between their beta-barrel and four-helix bundle domains. The STAT4 N-terminal domain dimer can be docked onto this STAT5a core fragment dimer based on shape and charge complementarities. The separation of the dimeric arrangement, taking place upon activation and nuclear translocation of STAT5a, is demonstrated by fluorescence resonance energy transfer experiments in living cells.

Modeling Cracks and Cracking Models: Structures, Mechanisms, Boundary Conditions, Constraints, Inconsistencies and The Proper Domains of Natural Laws

The emphasis on models hasn’t completely eliminated laws from scientific discourse and philosophical discussion. Instead, I want to argue that much of physics lies beyond the strict domain of laws. I shall argue that in important cases the physics, or physical understanding, does not lie either in laws or in their properties, such as universality, consistency and symmetry. I shall argue that the domain of application commonly attributed to laws is too narrow. That is, laws can still play an important, though peculiar, role outside their strict domain of validity. I shall argue also that, by way of a trade-off, while the actual domain of application of laws should be seen as much broader. At the same time, what I call ‘anomic’ representational elements reveal themselves as central to the descriptive and explanatory power of theories and model: boundary conditions, state descriptions, structures, constraints, limits and mechanisms. I conclude with a brief consideration of how my discussion has consequences for discussion of understanding, unification, approximation and dispositional properties. I focus on examples from physics, macroscopic and microscopic, phenomenological and fundametal: shock waves, propagation of cracks, symmetry breaking, and others. This law-eccentric kind of knowledge is central to both modeling the world and intervening in it.

Planning conditions in Hong Kong

PurposeThis paper was motivated by the absence of a government examination of and professional interest in planning conditions as a means of development control in Hong Kong. Proposes to examine this situation.Design/methodology/approachThe research objective is achieved by a field survey and legal analysis of its findings. The field survey of all the 60 residential development projects in Hong Kong under comprehensive development area zoning subject to conditional planning permissions from 1998 to 2000 involving 119 planning applications was conducted to assess factual compliance with planning conditions.FindingsThe findings show that, while most physical planning obligations have been duly fulfilled in these projects, the non‐depositing of master layout plans for development poses actual and potential public domain problems of planning enforcement, building permission, conveyancing and property management. The major problems of non‐compliance are property purchasers being unable to fully appreciate the environment of a development when making a decision to buy; subsequent titles defects, unauthorised building works and operations. Suggestions are made to close the loopholes in planning law and to introduce a formal channel for retrospective rectification in the light of the social consequences of non‐compliance.Originality/valueThis paper is the first serious attempt to evaluate the importance of compliance with planning conditions in Hong Kong and its analysis should be of interest not only to local policy makers and professional people in particular, but also to researchers in comparative development control in general.

Decision support for customization of the COTS selection process

Software technologies need to be customized to make them effective and efficient for a specific context. In this position paper, we consider the customization of the COTS selection process. We have developed a methodology which customizes the selection process based on the actual project domain characteristics (PDCs) including attributes such as available effort or project criticality. The customization of the process is done at both the process level and the activity level. We suggest a hybrid approach that integrates formalized knowledge with human expertise. This principle has already been successfully used in the context of the software release planning. The advantage is two-fold: Firstly, we exploit the existing empirical results related to different stages of the COTS selection process. Secondly, we facilitate involvement of human judgment to determine most appropriate decisions among the ones proposed by the formalized and knowledge-based solution techniques.

Axin Contains Three Separable Domains That Confer Intramolecular, Homodimeric, and Heterodimeric Interactions Involved in Distinct Functions

Axin is a major scaffold protein, interacting with diverse molecules involved in a number of signaling pathways. Axin can undergo dimer/oligomerization via its DIX domain. Here we show that whereas deletion of the DIX domain at the C terminus rendered Axin incapable of forming dimer, a larger deletion of the C-terminal region restored the ability of Axin to form dimers. Detailed analyses revealed that Axin actually contains two separate domains (D and I) in addition to the DIX domain for homodimerization. The D, I, and DIX domains alone can form homodimers. Interestingly, D and I domains strongly interact with each other, suggesting that Axin can form an intramolecular structure through D and I interaction in the absence of DIX. We also found that DIX-DIX homodimeric interaction is weak but that point mutations in the DIX domain abolished Axin homodimerization. We propose a model to suggest that Axin forms homodimeric interactions through three domains, D, I, and DIX. More importantly, lack of DIX-DIX interaction caused by point mutations in the DIX domain or deletion causes Axin to form an intramolecular loop through the D and I domains, disallowing homodimer formation. Ccd1 interacts with Axin D domain yet fails to interact with AxinDeltaDIX, confirming that D is masked after D-I looping. The Axin mutants that are defective in homodimer formation fail to activate JNK but have no effect on beta-catenin signaling. Our findings have thus provided a structural basis of conformational changes in Axin, which may underlie the diversity of Axin functions.