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Three-dimensional Space (three-dimensional + space)
Selected AbstractsNavigation by Parallax in Three-Dimensional Space During Fluoroscopy: Application in Guide Wire-Directed Axillary/Subclavian Vein PuncturePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2007ERNEST W. LAU M.D. Background:Fluoroscopy is range ambiguous,the relative positions in three-dimensional space of two structures with superimposed silhouettes cannot be ascertained. The parallax effect can be used to overcome this problem, and was used to develop a technique of axillary/subclavian vein puncture. Method:Patients requiring axillary/subclavian vein puncture were considered for the new technique. The vein was marked by a guide wire placed inside. In the postero-anterior (P-A) caudal projection, the needle was advanced dorsally from medial to the coracoid process at an arbitrary angle until its tip overlay the guide wire over the first intercostal space. Depending on whether the needle tip appeared caudad or cephalad of the guide wire in the P-A projection, the needle was advanced farther into or withdrawn back from the body, with its tip maintained over the guide wire in the P-A caudal projection at all times. Maneuvering of the needle stopped when the needle tip overlay the guide wire in both the P-A caudal and P-A projections or blood was aspirated. Result:Forty-one separate successful punctures were performed in 20 patients. No complications were recorded. Each puncture took no more than 1 minute, and the image intensifier needed to swing between the P-A caudal and the P-A projections only twice. Conclusions:The new technique was effective, efficient, and safe when implemented in clinical practice, justifying the parallax principles on which it is based. The parallax principles may be applied to other invasive medical procedures with due modifications. [source] Grid services for earthquake scienceCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 6-7 2002Geoffrey Fox Abstract We describe an information system architecture for the ACES (Asia,Pacific Cooperation for Earthquake Simulation) community. It addresses several key features of the field,simulations at multiple scales that need to be coupled together; real-time and archival observational data, which needs to be analyzed for patterns and linked to the simulations; a variety of important algorithms including partial differential equation solvers, particle dynamics, signal processing and data analysis; a natural three-dimensional space (plus time) setting for both visualization and observations; the linkage of field to real-time events both as an aid to crisis management and to scientific discovery. We also address the need to support education and research for a field whose computational sophistication is rapidly increasing and spans a broad range. The information system assumes that all significant data is defined by an XML layer which could be virtual, but whose existence ensures that all data is object-based and can be accessed and searched in this form. The various capabilities needed by ACES are defined as grid services, which are conformant with emerging standards and implemented with different levels of fidelity and performance appropriate to the application. Grid Services can be composed in a hierarchical fashion to address complex problems. The real-time needs of the field are addressed by high-performance implementation of data transfer and simulation services. Further, the environment is linked to real-time collaboration to support interactions between scientists in geographically distant locations. Copyright © 2002 John Wiley & Sons, Ltd. [source] Non-linear behavior of mass concrete in three-dimensional problems using a smeared crack approachEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2005H. Mirzabozorg Abstract A smeared crack approach has been proposed to model the static and dynamic behavior of mass concrete in three-dimensional space. The proposed model simulates the tensile fracture on the mass concrete and contains pre-softening behavior, softening initiation, fracture energy conservation and strain rate effects under dynamic loads. The validity of the proposed model has been checked using the available experimental results under static and dynamic loads. The direct and indirect displacement control algorithms have been employed under incremental increasing static loads. It was found that the proposed model gives excellent results and crack profiles when compared with the available data under static loads. The Koyna Dam in India has been used to verify the dynamic behavior of the proposed model. It was found that the resulting crack profiles were in good agreement with the available experimental results. Finally, the Morrow Point Dam was analyzed, including the dam,reservoir interaction effects, to consider its non-linear seismic behavior. It was found that the resulting crack profiles were in good agreement with the contour of maximum principal stresses and no numerical instability occurred during the analysis. Copyright © 2004 John Wiley & Sons, Ltd. [source] A multi-trait test of the leaf-height-seed plant strategy scheme with 133 species from a pine forest floraFUNCTIONAL ECOLOGY, Issue 3 2010Daniel C. Laughlin Summary 1.,Westoby's [Plant and Soil (1998), 199, 213] Leaf-Height-Seed (LHS) plant strategy scheme quantifies the strategy of a plant based on its location in a three-dimensional space defined by three functional traits: specific leaf area (SLA), height, and seed mass. This scheme is based on aboveground traits and may neglect strategies of belowground resource capture if root functioning is not mirrored in any of the axes. How then do fine roots fit into the LHS scheme? 2.,We measured 10 functional traits on 133 plant species in a ponderosa pine forest in northern Arizona, USA. This data set was used to evaluate how well the LHS scheme accounts for the variation in above and belowground traits. 3.,The three most important plant strategies were composed of multiple correlated traits, but SLA, seed mass, and height loaded on separate principle components. The first axis reflected the widely observed ,leaf economics spectrum'. Species at the high end of this spectrum had high SLA, high leaf and fine root nitrogen (N) concentration, and low leaf dry matter content. The second axis reflected variation in seed mass and fine root morphology. Plants at the positive end of this spectrum were plants with large seeds and low specific root length (SRL). The third axis reflected variation in height and phenology. Plants at the positive end of this spectrum were tall species that flower late in the growing season. 4.,Leaf N concentration was positively correlated with fine root N concentration. SRL was weakly positively correlated with SLA. SRL was not correlated with fine root N concentration. Leaf litter decomposition rate was positively correlated with the leaf economics spectrum and was negatively correlated with the height and phenology spectrum. 5.,Leaf traits, seed mass, and height appear to be integrating properties of species that reflect much of the variation in plant function, including root function. Fine root N concentration was positively mirrored by the leaf economics spectrum, and SRL was inversely mirrored by seed mass. The leaf and height axes play a role in controlling leaf litter decomposability, indicating that these strategy axes have important consequences for ecosystem functioning. [source] Human reach envelope and zone differentiation for ergonomic designHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 1 2009Jingzhou (James) Yang In human-centric design, the human reach envelope is one of the most important components to help layout design for workstations, vehicles, and aircrafts. It also can help people to study the range of motion of different body segments. Various methods have been developed to determine human reach envelopes. This article presents different methods and common challenges. Human reach envelopes only give feedback concerning whether a point is reachable. This is not enough for the designers. The more important information the designers need to know is the zones with different discomfort levels. This capability is a powerful tool for ergonomic designers. In addition, a methodology for workspace solid zone differentiation or surface zone differentiation in the three-dimensional space is presented. © 2008 Wiley Periodicals, Inc. [source] Micromechanical modelling of monotonic drained and undrained shear behaviour of granular media using three-dimensional DEMINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 12 2002Thallak. Abstract In this paper, numerical simulation results of isotropic compression and triaxial static shear tests under drained and undrained stress paths on polydisperse assembly of loose and dense spheres are presented. An examination of the micromechanical behaviour of loose and dense assemblies under drained and undrained conditions, considering the particulate nature of granular materials, has been carried out to explain micromechanically the granular material behaviour at the grain scale level. The numerical simulations have been carried out using a discrete element model (DEM) which considers a 1000 sphere particle polydisperse assembly with periodic space representing an infinite three-dimensional space. In this paper, we present how DEM simulations can contribute to developments in constitutive modelling of granular materials through micromechanical approach using information on microstructure evolution. A series of numerical tests are performed using DEM on 3-D assemblages of spheres to study the evolution of the internal variables such as average co-ordination number and induced anisotropy during deformation along with the macroscopic behaviour of the assemblage in drained and undrained shear tests. In a qualitative sense, the macroscopic stress,strain results and stress path evolution in these simulations using 3-D assemblies demonstrate that DEM simulations are capable of reproducing realistic compression and shear behaviour of granular materials. Copyright © 2002 John Wiley & Sons, Ltd. [source] Modified method of characteristics for solving population balance equationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2003Laurent Pilon Abstract This paper presents a new numerical method for solving the population balance equation using the modified method of characteristics. Aggregation and break-up are neglected but the density function variations in the three-dimensional space and its dependence on the external fields are accounted for. The method is an interpretation of the Lagrangian approach. Based on a pre-specified grid, it follows the particles backward in time as opposed to forward in the case of traditional method of characteristics. Unlike the direct marching method, the inverse marching method uses a fixed grid thus, making it compatible with other numerical schemes (e.g. finite-volume, finite elements) that may be used to solve other coupled equations such as the mass, momentum, and energy conservation equations. The numerical solutions are compared with the exact analytical solutions for simple one-dimensional flow cases. Very good agreement between the numerical and the theoretical solutions has been obtained confirming the validity of the numerical procedure and the associated computer program. Copyright © 2003 John Wiley & Sons, Ltd. [source] Shift of attention in depth in a semi-realistic settingJAPANESE PSYCHOLOGICAL RESEARCH, Issue 3 2002Toshiaki Miura Abstract: This research was based on previous research on the useful field of view in real driving, however shift of attention was examined in depth by the use of an improved tunnel simulator. Despite of the importance of this area of research, nothing like this has been performed previously. The subjects' task was judgment of the relative distance of targets (farther, nearer, or the same), in comparison with a fixation point. Reaction times were measured. There were two variables. One was three observing conditions. Subjects moved at apparent speeds of 40 km/h or 80 km/h or were stationary. The second variable was the validity of the precue concerning the location of the appearance of the target relative to the fixation point. There were three conditions, valid, invalid and or neutral. The results clearly showed that reaction times for nearer targets were shorter than those for farther targets in all conditions. This supports a viewer-centered representation of three-dimensional space. Concerning the direction of shift of attention, reaction time for shift of attention from far locations to near locations was shorter than for the opposite. This difference was more remarkable in the moving condition than in the stationary condition. This was called the rubber band metaphor of attention in locomotion (asymmetrical viewer-centered mode of shift of attention in depth). These results are ecologically valid. Possible underlying mechanisms are discussed from the viewpoint of distribution of attention resource. [source] A new analytical method for computing solvent-accessible surface area of macromolecules and its gradientsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 4 2005Shura Hayryan Abstract In the calculation of thermodynamic properties and three-dimensional structures of macromolecules, such as proteins, it is important to have an efficient algorithm for computing the solvent-accessible surface area of macromolecules. Here, we propose a new analytical method for this purpose. In the proposed algorithm we consider the transformation that maps the spherical circles formed by intersection of the atomic surfaces in three-dimensional space onto the circles on a two-dimensional plane, and the problem of computing the solvent-accessible surface area is reduced to the problem of computing the corresponding curve integrals on the plane. This allows to consider only the integrals along the circular trajectories on the plane. The algorithm is suitable for parallelization. Testings on many proteins as well as the comparison to the other analogous algorithms have shown that our method is accurate and efficient. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 334,343, 2005 [source] Three-dimensional map building for mobile robot navigation environments using a self-organizing neural networkJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 6 2004Min Young Kim In recent years, mobile robots have been required to become more and more autonomous in such a way that they are able to sense and recognize the three-dimensional space in which they live or work. In this paper, we deal with such an environment map building problem from three-dimensional sensing data for mobile robot navigation. In particular, the problem to be dealt with is how to extract and model obstacles which are not represented on the map but exist in the real environment, so that the map can be newly updated using the modeled obstacle information. To achieve this, we propose a three-dimensional map building method, which is based on a self-organizing neural network technique called "growing neural gas network." Using the obstacle data acquired from the 3D data acquisition process of an active laser range finder, learning of the neural network is performed to generate a graphical structure that reflects the topology of the input space. For evaluation of the proposed method, a series of simulations and experiments are performed to build 3D maps of some given environments surrounding the robot. The usefulness and robustness of the proposed method are investigated and discussed in detail. © 2004 Wiley Periodicals, Inc. [source] The Nut in Screw TheoryJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 8 2003Michael Griffis This study in projective geometry reveals that the principle of duality applies to the screw. Here, the screw is demonstrated to be an element of a projective three-dimensional space (P3), right alongside the line. Dual elements for the screw and line are also revealed (the nut and spline). Reciprocity is demonstrated for a pair of screws, and incidence is demonstrated for screw and its dual element. Reciprocity and incidence are invariant for projective transformations of P3, but only incidence is invariant for the more general linear transformations of screws. This latter transformation is analogous to a projective transformation of a projective five-dimensional space (P5), which is shown to induce a contact transformation of the original P3, where some points lying on a Kummer surface are directly mapped. © 2003 Wiley Periodicals, Inc. [source] Obstacle Avoidance for Spatial Hyper-Redundant Manipulators Using Harmonic Potential Functions and the Mode Shape TechniqueJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 1 2003F. Fahimi This paper deals with the obstacle avoidance problem for spatial hyper-redundant manipulators in known environments. The manipulator is divided into two sections, a proximal section that has not entered the space among the obstacles and a distal section among the obstacles. Harmonic potential functions are employed to achieve obstacle avoidance for the distal section in three-dimensional space in order to avoid local minima in cluttered environments. A modified panel method is used to generate the potential of any arbitrary shaped obstacle in three-dimensional space. An alternative backbone curve concept and an efficient fitting method are introduced to control the trajectory of proximal links. The fitting method is recursive and avoids the complications involved with solving large systems of nonlinear algebraic equations. The combination of a three-dimensional safe path derived from the harmonic potential field and the backbone curve concept leads to an elegant kinematic control strategy that guarantees obstacle avoidance. © 2003 Wiley Periodicals, Inc. [source] Gravity compensation of spatial two-DOF serial manipulatorsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 7 2002T. Wongratanaphisan This article presents the analysis of gravity compensation of a two-DOF serial manipulator operating in three-dimensional space by means of linear spring suspension. The physical configuration of the serial manipulator is assumed general. The analysis begins with gravity compensation of a one-DOF manipulator in order to form the basis which is then extended to a two-DOF manipulator. The approach taken in the analysis is that of conservation of potential energy. The goal is to seek the location and the stiffness of springs that provide complete compensation of gravity in the manipulator system. It has been found that complete compensation of gravity in a two-DOF serial manipulator system is possible. Unlike many previous works on spring suspension of a rigid body, which assume that one end of the suspending spring is attached to ground, it is proven in this study that, for complete compensation in a two-DOF manipulator, the spring that suspends the distal link cannot be connected to ground. Instead, it must be in certain motion relative to the proximal link. The discussion on how to provide such a motion for the spring is given. It is also explained how the problem of gravity compensation of a robot manipulator can be shifted to that of changing gravity environment within a manipulator system. The concept can be applied to simulation and testing of robot manipulators that will be sent to operate in a different gravity environment, such as space. © 2002 Wiley Periodicals, Inc. [source] Using OXSIM for path planningJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 8 2001Stephen Cameron We address the issue of building scalable and reusable path planners for realistic robot manipulators working in three-dimensional space amid complex geometry, by presenting the latest version of our robot manipulator planning toolbox, OxSIM. OxSIM is designed to greatly simplify the building of planners by providing core competence in three-dimensional geometry. This is done by the provision of efficient routines for computing the distance between parts of the robot and its environment. A new version of OXSIM, written in C++, provides an object-oriented interface to the basic system, which increases its ease of use. Here we give an overview of OxSIM and how it works and describe a modified version of the probabilistic road map planner that we have implemented under the framework. © 2001 John Wiley & Sons, Inc. [source] Producing and Editing Diagrams Using Co-Speech Gesture: Spatializing Nonspatial Relations in Explanations of Kinship in LaosJOURNAL OF LINGUISTIC ANTHROPOLOGY, Issue 1 2003N.J. Enfield This article presents a description of two sequences of talk by urban speakers of Lao (a southwestern Tai language spoken in Laos) in which co-speech gesture plays a central role in explanations of kinship relations and terminology. The speakers spontaneously use hand gestures and gaze to spatially diagram relationships that have no inherent spatial structure. The descriptive sections of the article are prefaced by a discussion of the semiotic complexity of illustrative gestures and gesture diagrams. Gestured signals feature iconic, indexical, and symbolic components, usually in combination, as well as using motion and three-dimensional space to convey meaning. Such diagrams show temporal persistence and structural integrity despite having been projected in midair by evanescent signals (i.e., handmovements anddirected gaze). Speakers sometimes need or want to revise these spatial representations without destroying their structural integrity. The need to "edit" gesture diagrams involves such techniques as hold-and-drag, hold-and-work-with-free-hand, reassignment-of-old-chunk-tonew-chunk, and move-body-into-new-space. [source] Three-dimensional representation of curved nanowiresJOURNAL OF MICROSCOPY, Issue 3 2004Z. HUANG Summary Nanostructures, such as nanowires, nanotubes and nanocoils, can be described in many cases as quasi one-dimensional curved objects projecting in three-dimensional space. A parallax method to construct the correct three-dimensional geometry of such one-dimensional nanostructures is presented. A series of scanning electron microscope images was acquired at different view angles, thus providing a set of image pairs that were used to generate three-dimensional representations using a matlab program. An error analysis as a function of the view angle between the two images is presented and discussed. As an example application, the importance of knowing the true three-dimensional shape of boron nanowires is demonstrated; without the nanowire's correct length and diameter, mechanical resonance data cannot provide an accurate estimate of Young's modulus. [source] Kinetics of self-condensing vinyl hyperbranched polymerization in three-dimensional spaceJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2008Xuehao He Abstract Self-condensing vinyl hyperbranched polymerization (SCVP) with A-B* type monomer is simulated applying Monte Carlo method using 3d bond fluctuation lattice model in three-dimensional space. The kinetics of SCVP with zero active energy of reaction is studied in detail. It is found that the maximal number,average and weight,average polymerization degrees and the maximal molecular weight distribution, at varying the initial monomer concentration and double bond conversion, are about 52, 190, and 3.93, respectively, which are much lower than theoretical values. The maximal average fraction of branching points is about 0.27, obtained at full conversion at the initial monomer concentration of 0.75. The simulation demonstrated the importance of steric effects and intramolecular cyclization in self-condensing vinyl hyperbranched polymerization. The results are also compared with experiments qualitatively and a good agreement is achieved. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4486,4494, 2008 [source] Global weak solution to the flow of liquid crystals systemMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 17 2009Fei Jiang Abstract In this paper, we study a simplified system for the flow of nematic liquid crystals in a bounded domain in the three-dimensional space. We derive the basic energy law which enables us to prove the global existence of the weak solutions under the condition that the initial density belongs to L,(,) for any . Especially, we also obtain that the weak solutions satisfy the energy inequality in integral or differential form. Copyright © 2009 John Wiley & Sons, Ltd. [source] Spherical harmonics in a non-polar co-ordinate system and application to Fourier series in 2-sphere,MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 14 2007H. M. Nasir Abstract A new non-polar spherical co-ordinate system for the three-dimensional space is introduced. The co-ordinate system is composed of six local co-ordinate systems mapped from six faces of a cube on to the 2-sphere. Weakly orthogonal and orthogonal spherical harmonics are constructed in this co-ordinate system. The spherical harmonics are easily computable functions consisting of polynomials and square root of polynomials. Examples of finite Fourier series computations are given in terms of the new spherical harmonics to demonstrate their immediate applicability. Copyright © 2007 John Wiley & Sons, Ltd. [source] Three-dimensional fine-scale genetic structure of the neotropical epiphytic orchid, Laelia rubescensMOLECULAR ECOLOGY, Issue 5 2004Dorset W. Trapnell Abstract Epiphytic plants occupy three-dimensional space, which allows more individuals to be closely clustered spatially than is possible for populations occupying two dimensions. The unique characteristics of epiphytes can act in concert to influence the fine-scale genetic structure of their populations which can, in turn, influence mating patterns and other population phenomena. Three large populations of Laelia rubescens (Orchidaceae) in the Costa Rican seasonal dry forest were sampled at two levels of intensity to determine: (i) whether individual clusters contain more than one genotype, and (ii) the spatial distribution and fine-scale genetic structure of genotypes within populations. Samples were assayed for their multilocus allozyme genotypes and spatial autocorrelation analyses were performed. High levels of genetic diversity, high genotypic diversity and low among-population variation were found. In the larger clusters, multiple genets per cluster were common with discrete clusters containing up to nine genotypes. Spatial autocorrelation analyses indicated significant positive genetic structure at distances of , 45 cm. This result is likely due to the formation of discrete clusters by vegetative reproduction, as well as the establishment of sexually derived progeny within and near maternal clusters. [source] Is the target for thalamic deep brain stimulation the same as for thalamotomy?MOVEMENT DISORDERS, Issue 10 2003FRCSC, Zelma H.T. Kiss MD Abstract Deep brain stimulation (DBS) has virtually replaced thalamotomy for the treatment of essential tremor. It is thought that the site for DBS is the same as the optimal lesion site; however, this match has not been investigated previously. We sought to determine whether the location of thalamic DBS matched the site at which thalamotomy would be performed. Eleven patients who had detailed microelectrode recording and stimulation for placement of DBS electrodes and subsequent successful tremor control were analysed. An experienced surgeon, blinded to outcome and final electrode position, selected the ideal thalamotomy site based on the reconstructed maps obtained intraoperatively. When the site of long-term clinically used DBS and theoretical thalamotomy location was calculated in three-dimensional space and compared for each of the x, y, and z axes in stereotactic space, there was no significant difference in the mediolateral location of DBS and theoretical lesion site. There was also no difference between the theoretical lesion site and the placement of the tip of the electrode; however, the active electrodes used for chronic stimulation were significantly more anterior (P = 0.005) and dorsal (P = 0.034) to the ideal thalamotomy target. This mismatch may reflect the compromise required between adverse and beneficial effects with chronic stimulation, but it also suggests different mechanisms of effect of DBS and thalamotomy. © 2003 Movement Disorder Society [source] Navigation by Parallax in Three-Dimensional Space During Fluoroscopy: Application in Guide Wire-Directed Axillary/Subclavian Vein PuncturePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2007ERNEST W. LAU M.D. Background:Fluoroscopy is range ambiguous,the relative positions in three-dimensional space of two structures with superimposed silhouettes cannot be ascertained. The parallax effect can be used to overcome this problem, and was used to develop a technique of axillary/subclavian vein puncture. Method:Patients requiring axillary/subclavian vein puncture were considered for the new technique. The vein was marked by a guide wire placed inside. In the postero-anterior (P-A) caudal projection, the needle was advanced dorsally from medial to the coracoid process at an arbitrary angle until its tip overlay the guide wire over the first intercostal space. Depending on whether the needle tip appeared caudad or cephalad of the guide wire in the P-A projection, the needle was advanced farther into or withdrawn back from the body, with its tip maintained over the guide wire in the P-A caudal projection at all times. Maneuvering of the needle stopped when the needle tip overlay the guide wire in both the P-A caudal and P-A projections or blood was aspirated. Result:Forty-one separate successful punctures were performed in 20 patients. No complications were recorded. Each puncture took no more than 1 minute, and the image intensifier needed to swing between the P-A caudal and the P-A projections only twice. Conclusions:The new technique was effective, efficient, and safe when implemented in clinical practice, justifying the parallax principles on which it is based. The parallax principles may be applied to other invasive medical procedures with due modifications. [source] Effect of sulfonic group on solubility parameters and solubility behavior of poly(2,6-dimethyl-1,4-phenylene oxide)POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2007Chunli Gong Abstract An investigation on the effect of sulfonic group on solubility parameters and solubility behavior of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) is presented. Sulfonated PPO (SPPO) was prepared using chlorosulfonic acid as a sulfonating agent. The structure of SPPO was confirmed by FT-IR, and the ion exchange capacity (IEC) of SPPO was accurately determined by conductometric titration and 1H-NMR. The three-dimensional solubility parameters of SPPO defined by Hansen were estimated by group contribution, and this approach was used to obtain the three coordinates of a solubility parameter in terms of: a dispersion part ,d, a polar part ,p and a hydrogen bonding part ,h. The theoretical predications of solubility behavior were characterized using "soluble sphere" in three-dimensional space. The estimated results were in accordance with the solubility experiments in different solvents. Copyright © 2006 John Wiley & Sons, Ltd. [source] A simple isohedral tiling of three-dimensional space by infinite tiles and with symmetry IadACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2002O. Delgado Friedrichs A tiling of space by tiles that have all hexagonal faces and are infinite in one direction is described. The tiling is simple (four tiles meet at each vertex, three at each edge and two at each face) and carries a 4-connected net whose vertices are the lattice complex S* with symmetry Iad. The tiling is closely related to the densest cubic cylinder packing, ,. It is shown that the other invariant cubic lattice complexes unique to Iad (Y** and V*) are also related to the same cylinder packing. [source] Discrete Fourier transform in arbitrary dimensions by a generalized Beevers,Lipson algorithmACTA CRYSTALLOGRAPHICA SECTION A, Issue 3 2000Martin Schneider The Beevers,Lipson procedure was developed as an economical evaluation of Fourier maps in two- and three-dimensional space. Straightforward generalization of this procedure towards a transformation in -dimensional space would lead to nested loops over the coordinates, respectively, and different computer code is required for each dimension. An algorithm is proposed based on the generalization of the Beevers,Lipson procedure towards transforms in -dimensional space that contains the dimension as a variable and that results in a single piece of computer code for arbitrary dimensions. The computational complexity is found to scale as , where N is the number of pixels in the map, and it is independent of the dimension of the transform. This procedure will find applications in the evaluation of Fourier maps of quasicrystals and other aperiodic crystals, and in the maximum-entropy method for aperiodic crystals. [source] Rigidity and persistence for ensuring shape maintenance of multi-agent meta-formations,ASIAN JOURNAL OF CONTROL, Issue 2 2008Julien M. Hendrickx Abstract This paper treats the problem of merging formations, where the underlying model of a formation is graphical. We first analyze the rigidity and persistence of meta-formations, which are formations obtained by connecting several rigid or persistent formations. Persistence is a generalization to directed graphs of the undirected notion of rigidity. In the context of moving autonomous agent formations, persistence characterizes the efficacy of a directed structure of unilateral distance constraints seeking to preserve a formation shape. We derive then, for agents evolving in a two- or three-dimensional space, the conditions under which a set of persistent formations can be merged into a persistent meta-formation, and give the minimal number of interconnections needed for such a merging. We also give conditions for a meta-formation obtained by merging several persistent formations to be persistent. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] Marginal relevance of disorder for pinning modelsCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 2 2010Giambattista Giacomin The effect of disorder on pinning and wetting models has attracted much attention in theoretical physics. In particular, it has been predicted on the basis of the Harris criterion that disorder is relevant (annealed and quenched models have different critical points and critical exponents) if the return probability exponent ,, a positive number that characterizes the model, is larger than ½. Weak disorder has been predicted to be irrelevant (i.e., coinciding critical points and exponents) if , < ½. Recent mathematical work has put these predictions on firm ground. In renormalization group terms, the case , = ½ is a marginal case, and there is no agreement in the literature as to whether one should expect disorder relevance or irrelevance at marginality. The question is also particularly intriguing because the case , = ½ includes the classical models of two-dimensional wetting of a rough substrate, of pinning of directed polymers on a defect line in dimension (3 + 1) or (1 + 1), and of pinning of an heteropolymer by a point potential in three-dimensional space. Here we prove disorder relevance both for the general , = ½ pinning model and for the hierarchical pinning model proposed by Derrida, Hakim, and Vannimenus, in the sense that we prove a shift of the quenched critical point with respect to the annealed one. In both cases we work with Gaussian disorder and we show that the shift is at least of order exp(,1/,4) for , small, if ,2 is the disorder variance. © 2009 Wiley Periodicals, Inc. [source] | ||||||||||||||||||||||||||||