Showing papers by "Polytechnic University of Catalonia published in 2000"
01 May 2000
TL;DR: This paper proposes a register file architecture composed of multiple banks, which provides low latency and simple bypass logic and shows that a two-level organization degrades IPC and increases performance by 87% and 92% when the register file access time is factored in.
Abstract: The register file access time is one of the critical delays in current superscalar processors. Its impact on processor performance is likely to increase in future processor generations, as they are expected to increase the issue width (which implies more register ports) and the size of the instruction window (which implies more registers), and to use some kind of multithreading. Under this scenario, the register file access time could be a dominant delay and a pipelined implementation would be desirable to allow for high clock rates.However, a multi-stage register file has severe implications for processor performance (e.g. higher branch misprediction penalty) and complexity (more levels of bypass logic). To tackle these two problems, in this paper we propose a register file architecture composed of multiple banks. In particular we focus on a multi-level organization of the register file, which provides low latency and simple bypass logic. We propose several caching policies and prefetching strategies and demonstrate the potential of this multiple-banked organization. For instance, we show that a two-level organization degrades IPC by 10% and 2% with respect to a non-pipelined single-banked register file, for SpecInt95 and SpecFP95 respectively, but it increases performance by 87% and 92% when the register file access time is factored in.
475 citations
TL;DR: In this article, the behavior of the small fractal Koch monopole is numerically and experimentally analyzed, and it is shown that as the number of iterations on the small Koch monopoles are increased, the Q of the antenna approaches the fundamental limit for small antennas.
Abstract: Fractal objects have some unique geometrical properties. One of them is the possibility to enclose in a finite area an infinitely long curve. The resulting curve is highly convoluted being nowhere differentiable. One such curve is the Koch curve. In this paper, the behavior the Koch monopole is numerically and experimentally analyzed. The results show that as the number of iterations on the small fractal Koch monopole are increased, the Q of the antenna approaches the fundamental limit for small antennas.
457 citations
TL;DR: A series of experimental tests on stainless steel beams is presented in this paper, which includes tests to determine the stress-strain relationship of the material, considering the effects of cold work, and a comparative analysis between the experimental results of deflections and those results derived from a numerical model considering material non-linearity.
417 citations
TL;DR: In this article, the performance of both static and kinematic GPS measurements in landslide monitoring has been evaluated in the landslide of Vallcebre, Eastern Pyrenees (Spain), which has been periodically monitored with terrestrial photogrammetry and geodetic measurements.
395 citations
TL;DR: This paper exposes the fallacies in a recent criticism of logratio-based distance measures—in particular, the misstatements thatLogratio methods destroy distance structures and are denominator dependent.
Abstract: The concept of distance between two compositions is important in the statistical analysis of compositional data, particularly in such activities as cluster analysis and multidimensional scaling. This paper exposes the fallacies in a recent criticism of logratio-based distance measures—in particular, the misstatements that logratio methods destroy distance structures and are denominator dependent. Emphasis is on ensuring that compositional data analysis involving distance concepts satisfies certain logically necessary invariance conditions. Logratio analysis and its associated distance measures satisfy these conditions.
390 citations
TL;DR: Two apparently different forms of dealing with the numerical instability due to the incompressibility constraint of the Stokes problem are analyzed and it is shown here that the first method can also be recast in the framework of sub-grid scale methods with a particular choice for the space ofSub-scales.
383 citations
TL;DR: In this article, a Sierpinski dipole FSS has been analyzed and measured and the results show an interesting dual-band behavior, and a near field measurement technique is applied to characterize the FSS response to different angles of incidence.
Abstract: The multiband properties of self-similar fractals can be advantageously exploited to design multiband frequency selective surfaces (FSS). A Sierpinski dipole FSS has been analyzed and measured and the results show an interesting dual-band behavior. Furthermore a near-field measurement technique is applied to characterize the FSS response to different angles of incidence. Finally, it is shown that it is possible to tune the FSS response by properly perturbating the geometry of the Sierpinski dipole.
303 citations
TL;DR: In this paper, the effects of confinement in nanotubes on the hydrogen bond structure of liquid water are studied by molecular dynamics simulation and the results indicate that the averaged number of hydrogen bonds decreases when compared with bulk water and it is roughly independent of the tube radius excepting for very narrow tubes, which suffer a dramatic destruction of the H-bond network.
287 citations
TL;DR: In this paper, two experimental high rate algal ponds (HRAPs) were installed on the roof of the Technical University of Catalonia, Barcelona, Spain (lat. 41° 24′ 42″ N; long. 2° 7′42″ E).
Abstract: Two experimental high rate algal ponds (HRAPs) (1.5m2, 570 L per unit), each with a secondaryclarifier for algal biomass separation (0.025 m2,without recirculation), were fed with urban wastewaterfor a one-year period (June 1993 to July 1994). TheHRAPs were installed on the roof of the Department ofHydraulic, Coastal and Environmental Engineering ofthe Technical University of Catalonia, Barcelona,Spain (lat. 41° 24′ 42″ N; long. 2° 7′42″ E). Nitrogen removal efficiency and changes intotal nitrogen, total organic nitrogen,NH4
+-N, and oxidized nitrogen underdifferent hydraulic retention times (HRTs) werecompared. HRAP A was always operated at a higherHRT than HRAP B. Both HRAPs were subjected to thesame environmental conditions of solar radiation, airtemperature and influent water quality. Grab samplesof influent, effluent of the HRAP (mixed liquor) andfinal effluent from the clarifiers were taken once aweek. The annual average nitrogen removal was 73% forHRAP A, and 57% for HRAP B. Higher removal in HRAP Awas due to a lower inorganic nitrogen concentration inits effluent. Significant differences (p> 0.05) inthe relative proportions of nitrogen forms between thetwo HRAPs were observed only in autumn and winter.This was mainly because HRAP B did not achieve a highlevel of NH4
+-N removal by stripping andalgal uptake, as observed in HRAP A. NH4
+-Nstripping was the most important mechanism fornitrogen removal (mean efficiency of 47% and 32% inHRAP A and B, respectively) followed by algal uptake,and subsequent algal separation in the clarifiers(mean efficiency of 26% and 25% in HRAP A and Brespectively). The conclusion of this study is thatHRT determines both the nitrogen removal efficiencyand the distribution of nitrogen forms in the effluentof a HRAP. The nitrogen removal level can becontrolled through suitable HRT operating strategies.By operating at a HRT of 4 days in spring and summer,and 10 days in autumn and winter, nitrogenconcentration in the effluent of a HRAP system can bereduced to less than 15 mg L-1 N.
284 citations
TL;DR: In this article, a modified biosorbent was used for palladium recovery in an acidic medium (around pH 2), and the influence of several parameters such as pH and competitor anions were studied with respect to sorption equilibrium.
Abstract: The high nitrogen content of chitosan is the main reason for its ability to sorb metal ions through several mechanisms including ion-exchange or chelation, depending on the metal and the pH of the solution. Glutaraldehyde is used to crosslink chitosan through imine linkage between amine groups of chitosan and aldehyde groups of the crosslinking agent. This modified biosorbent was studied for palladium recovery in acidic medium (around pH 2). The influence of several parameters such as pH and competitor anions were studied with respect to sorption equilibrium. Sorption isotherms were obtained and modeled using the Langmuir and the Freundlich model. This study also examines the effect of palladium concentration, particle size, sorbent dosage, and the extent of crosslinking on sorption kinetics. Kinetic curves are modeled using single diffusion model equations to evaluate the predominance of either external or intraparticle mass transfer resistance. The influence of the acid used to control the pH of the solution was examined in conjunction with the influence of competitor anions. Sulfuric acid proves to be unfavorable to palladium sorption, in comparison with hydrochloric acid. However, the addition of chloride anions in a palladium solution, whose pH is controlled with sulfuric acid, enhances metal anion sorption: results are interpreted with reference to chloropalladate speciation.
263 citations
TL;DR: In this paper, the authors summarized results obtained by molecular dynamics simulations of defect clusters and small dislocation loops in α-Fe(bcc) and Cu(fcc), and the structure and stability of vacancy and interstitial loops are reviewed, and the dynamics of glissile clusters assessed.
TL;DR: In this paper, a mixed hierarchical approximation based on finite elements and meshless methods is presented, which couples regions where finite elements or meshless method are used to interpolate: continuity and consistency is preserved.
Abstract: A mixed hierarchical approximation based on finite elements and meshless methods is presented. Two cases are considered. The first one couples regions where finite elements or meshless methods are used to interpolate: continuity and consistency is preserved. The second one enriches a finite element mesh with particles. Thus, there is no need to remesh in adaptive refinement processes. In both cases the same formulation is used, convergence is studied and examples are shown. Copyright © 2000 John Wiley & Sons, Ltd.
TL;DR: In this article, the surface displacement at the contact boundary under applied load and in the unloaded state is correlated with the uniaxial strain hardening exponent, n, and it is found that sinking-in predominates in materials where n > 0.2.
01 Jan 2000
TL;DR: This study provides the results of the open coding process from the application of the grounded theory method and obtains an initial unified model of the critical success factors in ERP implementations, mapped in a matrix with four perspectives: organisational, technological, strategic and tactical.
Abstract: Despite the benefits that can be achieved from a successful ERP system implementation, there is already evidence of high failure risks in ERP implementation projects. Too often, project managers focus mainly on the technical and financial aspects of the implementation project, while neglecting or putting less effort on the nontechnical issues. Therefore, one of the major research issues in ERP systems today is the study of ERP implementation success. Some authors have shown that ERP implementation success definition and measurement depends on the points of view of the involved stakeholders. A typical approach used to define and measure ERP implementation success has been critical success factors approach. Along this line, in this research we seek to contribute to our understanding of the critical success factors of ERP implementations and how these factors can be put into practice to help the process of project management in ERP implementations. We attempt to build a consensus from previous research and to derive a unified model of critical success factors in ERP implementations. For this purpose we apply grounded theory as our main research method. We have collected all the relevant research material and we have coded it. To increase the validity and reliability of the study, the several information sources have been triangulated and inconsistencies have been clarified with additional documentation. This study provides the results of the open coding process from our application of the grounded theory method. After the coding step, we obtain an initial unified model of the critical success factors in ERP implementations. We then map these critical success factors in a matrix with four perspectives: organisational, technological, strategic and tactical.
TL;DR: In this article, a stabilized finite element method for solving convection-diffusion-reaction equations is studied, which is based on the subgrid scale approach and an algebraic approximation to the subscales.
TL;DR: An overview of the impact of Artificial Intelligence techniques on the definition and development of Environmental Decision Support Systems (EDSS) during the last fifteen years is presented.
Abstract: An effective protection of our environment is largely dependent on the quality of the available information used to make an appropriate decision. Problems arise when the quantities of available information are huge and nonuniform (i.e., coming from many different disciplines or sources) and their quality could not be stated in advance. Another associated issue is the dynamical nature of the problem. Computers are central in contemporary environmental protection in tasks such as monitoring, data analysis, communication, information storage and retrieval, so it has been natural to try to integrate and enhance all these tasks with Artificial Intelligence knowledge-based techniques. This paper presents an overview of the impact of Artificial Intelligence techniques on the definition and development of Environmental Decision Support Systems (EDSS) during the last fifteen years. The review highlights the desirable features that an EDSS must show. The paper concludes with a selection of successful applications to a wide range of environmental problems.
TL;DR: In this article, strong discontinuity kinematics (considering jumps in the displacement fields across a discontinuity interface) induces projected discrete constitutive models (traction-displacement jumps) in a consistent manner, which provides possible links between the classical continuum strain-localization analysis and the nonlinear (decohesive) fracture mechanics techniques.
TL;DR: A general summary of the actual situation and recent developments that may be incorporated to architectural design tools in a near future, together with some critical remarks about their relevance to architecture are presented.
TL;DR: In this paper, the co-gasification of residual biomass/poor coal blends and gasification of individual feedstocks used in the blends were performed in a bench scale, continuous fluidized-bed working at atmospheric pressure.
TL;DR: Application of the standard finite element Galerkin method to the modified differential equations leads to a stabilized discrete system of equations overcoming the numerical instabilities emanating from the advective terms and those due to the lack of compatibility between approximate velocity and pressure fields.
TL;DR: In this paper, the authors describe how the nite element method and the finite volume method can be successfully combined to derive two new families of thin plate and shell triangles with translational degrees of freedom as the only nodal variables.
Abstract: SUMMARY The paper describes how the nite element method and the nite volume method can be successfully combined to derive two new families of thin plate and shell triangles with translational degrees of freedom as the only nodal variables. The simplest elements of the two families based on combining a linear interpolation of displacements with cell centred and cell vertex nite volume schemes are presented in detail. Examples of the good performance of the new rotation-free plate and shell triangles are given. Copyright ? 2000 John Wiley & Sons, Ltd.
TL;DR: In this article, the authors present a stabilized finite element formulation for the transient incompressible Navier-Stokes equations, which allows the use of equal interpolation for both velocities and pressures, and provides a stability estimate for the case of the simple backward Euler time integration scheme for both the implicit and explicit treatment of the pressure gradient projection.
TL;DR: A recently introduced technique that consists of filtering that sequence of energies along the frequency dimension is presented and its resulting parameters are compared with the widely used cepstral coefficients, showing that the flexibility of this combined (tiffing) approach can be used to design a robust set of filters.
TL;DR: In this article, a user-based beach climate index based on thermal sensation and bathing water temperature was proposed to evaluate most major Euro-Mediterranean/Black Sea and a range of other beach tourism areas on a month-by-month basis.
Abstract: In many coastal resort areas of the world, it is likely that optimal climatic conditions for beach use might occur outside the peak of the tourist season. Investigation of this issue together with associated publicity might help to spread the tourism load and hence reduce undesirable social and environmental effects of extreme seasonality in tourist demand. For this to take place, better knowledge of beach user preferences in terms of climate and bathing water temperature is required. Questionnaire surveys were carried out in Wales, Malta and Turkey to establish the preferences of north European beach users for thermal sensation and bathing water temperature, plus priority levels for other climatic attributes. A user-based beach climate index based on these preferences and priorities was formulated. Linkage was made between the user-generated ratings for various climatic conditions and published climate data to evaluate most major Euro-Mediterranean/Black Sea and a range of other beach tourism areas on a month-by-month basis. Results showed excessively hot thermal sensation in many southern and eastern Mediterranean coastal destinations during July and August, the present peak of the beach tourism season. Highest preference was given to water temperatures rather lower than those found in these areas during late summer. Many long haul coastal destinations popular with north European visitors had similar unpleasant thermal sensations over several months. Uncertainties and deficiencies still exist with the system, but from the point of view of north European beach users the final scores generated in this study may be regarded as good approximations of the quality of resort area climates for sedentary beach use.
15 May 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the grain growth kinetics of commercially pure Titanium, Ti 0.2Pd in the α and β phases, Ti 6Al-4V and Ni-Ti in the β phase have been studied.
Abstract: The grain growth kinetics of commercially pure Titanium, Ti–0.2Pd in the α and β phases, Ti–6Al–4V and Ni–Ti in the β phase have been studied. The perimeter, diameter and area as grain size parameters have been measured by means of the image analysis technique for different heat treatment temperatures and times. The growth exponents and activation energies have also been determined. The influence of the grain size on the mechanical properties have been evaluated and for the Ni–Ti shape memory alloy, the influence of the grain growth on the transformation temperatures, thermodynamic magnitudes and on the transformation stresses has been determined.
TL;DR: This paper begins the study of small-world networks as communication networks using graph-theoretic methods to obtain exact results and constructs networks with strong local clustering and small diameter (instead of average distance).
TL;DR: In this paper, an optimal control tool for water distribution networks was developed in the context of a European research project and the application to the city of Sintra (Portugal) is presented.
TL;DR: In this paper, a simple model that explains the behavior of the Sierpinski fractal antenna is presented, and the model is applied to predict the behavior when the flare angle is modified and its validity is assessed by comparing its predictions with measured data.
Abstract: A simple model that explains the behavior of the Sierpinski fractal antenna is presented. This model shows that the multiband behavior of the Sierpinski fractal antenna is a consequence of its fractal nature. The model is applied to predict the behavior of the Sierpinski fractal antenna when the flare angle is modified and its validity is assessed by comparing its predictions with measured data.
TL;DR: In this article, the authors improved previous lower bounds on the number of simple polygonizations and other kinds of crossing-free subgraphs of a set of N points in the plane by analyzing a suitable configuration.
Abstract: We improve previous lower bounds on the number of simple polygonizations, and other kinds of crossing-free subgraphs, of a set of N points in the plane by analyzing a suitable configuration. We also prove that the number of crossing-free perfect matchings and spanning trees is minimum when the points are in convex position.
TL;DR: Both the heterogeneity of the folding state and the time‐dependent folding transitions undergone by the aggregated polypeptides indicate that IBs are not mere deposits of collapsed, inert molecules but plastic reservoirs of misfolded proteins that would allow, at least up to a certain extent, their in vivo recovery and transference to the soluble cell fraction.