Dynamic Simulation

In this paper, we compare three observers and methods for estimation of the longitudinal and latéral velocity of the vehicle. These methods are based on the First Order Sliding Mode (FOSM), Second Order Sliding Mode (SOSM) and on the use of algebraic approach ALIEN. Their performance are studied using a 16 DoF dynamic simulator.

The study of the dynamics of a simple batch distillation usually assumes the equilibrium between the liquid and vapour phases. In contrast to that approach, this work considers the analysis of the dynamic behaviour of a nonequilibrium simple batch distillation. A simple batch distillation device is similar to an evapouration unit because no reflux is employed. A mathematical model and their singular points are analysed through the usual technique of linearization followed by the eigenvalues analysis. The stability nature of those points is presented for ideal solutions. Phase plane plots are made to show the occurrence of some unexpected behaviours such as 'dynamic azeotropic points' and 'inversion of the distillation order'. The dependence of these phenomena on the vapour withdrawal flowrate is established for simple batch distillation. #

Molecular dynamics a b s t r a c t This study reports the comparative molecular modeling, docking and dynamic simulations of human a9a10 nicotinic acetylcholine receptors complexed with acetylcholine, nicotine and a-conotoxin RgIA, using as templates the crystal structures of Aplysia californica and Lymnaea stagnalis acetylcholine binding proteins. The molecular dynamics simulations showed that Arg112 in the complementary a10(À) subunit, is a determinant for recognition in the site that binds small ligands. However, Glu195 in the principal a9(+), and Asp114 in the complementary a10(À) subunit, might confer the potency and selectivity to a-conotoxin RgIA when interacting with Arg7 and Arg9 of this ligand.

This paper presents a method for analysis and design of steady state recycling (SSR) chromatography under arbitrary purity or yield requirements. The approach applies to SSR processes in mixed-recycle operation and allows for the direct prediction of the steady state and the design parameters without performing dynamic simulations. Therefore, it simplifies optimal design of SSR processes and evaluation of process performance, while allowing minimizing the startup time of the process.

The power system network is becoming more complex nowadays and it is very difficult to maintain the stability of the system. Today's enhancement of technology makes it possible to include new energy storage devices in the electric power system. In addition, with the aid of power electronic devices, it is possible to independently exchange active and reactive power flow with

Abstract—This paper reports on the control structure of the pneumatic biped Lucy. The robot is actuated with pleated pneumatic artificial muscles, which have interesting characteristics that can be exploited for legged machines. They have a high power to weight ratio, an ...

We present a new approach for computing generalized proximity information of arbitrary 2D objects using graphics hardware. Using multi-pass rendering techniques and accelerated distance computation, our algorithm performs proximity queries not only for detecting collisions, but also for computing intersections, separation distance, penetration depth, and contact points and normals. Our hybrid geometry and image-based approach balances computation between the CPU and graphics subsystems. Geometric object-space techniques coarsely localize potential intersection regions or closest features between two objects, and image-space techniques compute the low-level proximity information in these regions. Most of the proximity information is derived from a distance field computed using graphics hardware. We demonstrate the performance in collision response computation for rigid and deformable body dynamics simulations. Our approach provides proximity information at interactive rates for a variety of simulation strategies for both backtracking and penalty-based collision responses.

As seen in textbooks of polymer physics, a linear polymer chain can be modeled as a filament of connected beads. This concept can also be adapted to fibers and, for example, flexible fibers can be modeled by considering a stretch force, bending and torsion torques with a non-slip condition between adjacent beads, following the particle simulation method. In predicting fiber motions and their relating rheological properties, the importance of hydrodynamic interactions should be analyzed, so in this work we study the effect of hydrodynamic interactions on the behavior of a single flexible fiber under shear using Stokesian dynamics simulation with a 11N × 11N mobility matrix, where N is the aspect ratio of the fiber. Our results indicate that hydrodynamic interaction becomes significant when the fiber is highly flexible.

This paper presents fast algorithms for penetration and contact determination between general polyhedral models in dynamic environments. The main contribution is an extension of an earlier expected constant time algorithm between convex polytopes to detect penetrations and contacts. For each pair of non-convex polyhedral models, the algorithm uses the convex hull of each object to determine which regions of the objects are colliding. After identifying these regions, it uses a new dynamic technique, sweep and prune, to overcome the bottleneck of O(n 2) pairwise feature checks of these regions. The resulting algorithm has been implemented and in practice its performance in dynamic environments is O(n + m), where m corresponds to the number of feature pairs close to each other.

This paper presents a technique to differentially diagnose two localized gear tooth faults: a spall and a crack in the gear tooth fillet region. These faults could have very different prognoses, but existing diagnostic techniques only indicate the presence of local tooth faults without being able to differentiate between a spall and a crack. The effects of spalls and cracks on the behavior/response of gear assemblies were studied using static and dynamic simulation models. Changes in the kinematics of a pair of meshing gears due to a gear tooth root crack and a tooth flank spall were compared using a static analysis model. The difference in the variation of the transmission error caused by the two faults reveals their characteristics. The effect of a tooth crack depends on the change in stiffness of the tooth, while the effect of a spall is predominantly determined by the geometry of the fault. The effect of the faults on the gear dynamics was studied by simulating the transmission error in a lumped parameter dynamic model. A technique had previously been proposed to detect spalls, using the cepstrum to detect a negative echo in the signal (from entry into and exit from the spall). In the authors' simulations, echoes were detected with both types of fault, but their different characteristics should allow differential diagnosis. These concepts are presented prior to experimental validation in hopes that the diagnostic techniques will be useful in the failure analysis community prior to the validation by ongoing experimental testing of the concepts and the evaluation of how metallurgical defects may influence fault development and detection.

A prototype tool to assist architects during the early design stage of floor plans has been developed, consisting of an Evolutionary Program for the Space Allocation Problem (EPSAP), which generates sets of floor plan alternatives according to the architect's preferences; and a Floor Plan Performance Optimization Program (FPOP), which optimizes the selected solutions according to thermal performance criteria. The design

The TRIUMF ISAC facility has two variable energy heavy ion linacs as post accelerators for radioactive ion beams. The ISAC I linac is a warm IH-DTL with five accelerating tanks and three bunchers, the ISAC II linac uses twenty independently phased superconducting cavities. The first linac operates between 150keV/u and 1.8Mev/u; the second boosts the 1.5MeV/u injected beam by 20MV. The DTL is tuned based on the energy spectrum from an analysing magnet. The superconducting linac is tuned on energy and time profiles with a diagnostic based on a gold foil scattering ions to a silicon detector. The silicon requires lower beam intensity. Furthermore the tuning time is reduced and streamlined by means of a MATLAB graphical user interface. This interface uses a simple cosine model to characterize the energy gain versus RF phase of each cavity. Based on this we have pursued a new tuning procedure for the DTL using a gold foil/silicon detector diagnostic. The more complex RF structures of the DTL require measurements and beam dynamics simulations (done with the LANA code) to produce a model for a dedicated MATLAB interface. In the paper we describe the two existing tuning methods and present the new DTL procedure and interface.

Many dynamic simulators have been developed in the last thirty years for different types of vehicles. Flight simulators and drive simulators are very well known examples. This paper describes the design and implementation of a dynamic simulator for the testing of inertial sensors devoted to vehicle navigation through a Hardware-In-The-Loop test rig composed of an industrial robot and a commercially available Inertial Measurement Unit (IMU). The authors are developing an innovative localization algorithm for railway vehicles which integrates inertial sensors with tachometers. The opportunity to set up a testing simulator capable of replicating in a realistic fashion the dynamic effects of the vehicle motion on inertial sensors allows to avoid expensive on board acquisitions and to speed up algorithm tuning. The real-time control architecture featured by the available industrial robot allows to precisely specify and execute motion trajectories with tight path and time law constraints required by the application at hand.

Seladin-1 Cholesterol biosynthesis Homology modelling MD simulation Enzymatic product egress a b s t r a c t Recent biochemical and clinical evidences unveiled that DHCR24 enzyme (3-␤-hydoxysterol-24 -reductase, also named seladin-1), which catalyzes the last step of the cholesterol biosynthesis, is implicated in relevant neuroprotective processes by modulating the level of cholesterol in membrane. The present study was undertaken with a view to model the DHCR24 enzyme and its catalytic site, analyzing the substrate recognition at an atomic level. A homology model of the enzyme was obtained based on plant Cytokinin Dehydrogenase, and its active site was found to bind the desmosterol plus a set of post-squalenic intermediates of the cholesterol biosynthesis in a binding mode conducive to catalysis, even if the docking results suggested that the enzyme has a clear preference for the last intermediates of such biosynthetic pathway. Since DHCR24 possesses a putative transmembrane segment, the enzyme was, then, inserted in a suitable membrane model and the membrane-anchored structure in complex with desmosterol and cholesterol underwent 10 ns MD simulations.

We develop a systematic coarse-graining procedure which establishes the connection between models of mixtures of immiscible fluids at different length and time scales. We start from the Cahn-Hilliard model of spinodal decomposition in a binary fluid mixture under flow from which we derive the coarse-grained description. The crucial step in this procedure is to identify the relevant coarse-grained variables and find the appropriate mapping which expresses them in terms of the more microscopic variables. In order to capture the physics of the Doi-Ohta level, we introduce the interfacial width as an additional variable at that level. In this way, we account for the stretching of the interface under flow and derive analytically the convective behavior of the relevant coarsegrained variables, which in the long wavelength limit recovers the familiar phenomenological Doi-Ohta model. In addition, we obtain the expression for the interfacial tension in terms of the Cahn-Hilliard parameters as a direct result of the developed coarse-graining procedure. Finally, by analyzing the numerical results obtained from the simulations on the Cahn-Hilliard level, we discuss that dissipative processes at the Doi-Ohta level are of the same origin as in the Cahn-Hilliard model. The way to estimate the interface relaxation times of the Doi-Ohta model from the underlying morphology dynamics simulated at the Cahn-Hilliard level is established.

This paper describes how damage propagation can be modeled within the modules of aircraft gas turbine engines. To that end, response surfaces of all sensors are generated via a thermo-dynamical simulation model for the engine as a function of variations of flow and efficiency of the modules of interest. An exponential rate of change for flow and efficiency loss was imposed for each data set, starting at a randomly chosen initial deterioration set point. The rate of change of the flow and efficiency denotes an otherwise unspecified fault with increasingly worsening effect. The rates of change of the faults were constrained to an upper threshold but were otherwise chosen randomly. Damage propagation was allowed to continue until a failure criterion was reached. A health index was defined as the minimum of several superimposed operational margins at any given time instant and the failure criterion is reached when health index reaches zero. Output of the model was the time series (cycles) of sensed measurements typically available from aircraft gas turbine engines. The data generated were used as challenge data for the Prognostics and Health Management (PHM) data competition atPHM'08.

The point-chart approximation of the Miertus-Scrocco-Tomasi solvation model (MST-PC) based on a continuum representation of the solvent has been incorporated in force field calculations. Application in molecular mechanics (MM) involves conformational equilibria in solution: rotational isomers of ethylene glycol (I), 1,2-difluoroethane (10, fluoroacetic acid (110, and representative conformers of macrocyclic receptors such as 18-crown-6 (IV), cryptand 2.2.2 (V), and t-butyl-calix[4]arenetetraamide (VI). Assessment of the MST-PC results is based on the comparison with ab initio reactive field calculations (for I-111), with the continuum model of Still (W. C. Still et al., J.

The development of aerodynamic foil bearings in the past decade is due, for a major part to environmental reasons because: first, air is a clean lubricant and second foil bearings can be used in very critical thermal environment: air has a poor sensitivity to high temperature changes. Foil bearings are often used for very high velocity turbines. Experimental studies have shown the capability of foil bearing to work under rather high load capacity with good dynamic behavior. Numerical simulations are now able to predict with a good accuracy foil bearing load capacity. They take into account foil deformation and dry friction between foils. For dynamic simulation, dry friction has been taken into account only through damping coefficient. As damping is not completely similar to dry friction, this paper is a first attempt in taking account its effect in the foil bearing dynamic behavior. A non-linear model, coupling a simplified equation for the rotor motion to both Reynolds equation and foil assembly model is described. Then the dynamic behavior, for a given unbalance is studied. For different values of friction coefficient, the rotor trajectory is studied when velocity increased. For low and high friction coefficient, the dynamic behavior shows critical speeds. For medium values (between 0.2 and 0.4), these critical speeds disappear. This work outlines that it is possible to optimize the friction between the foils in order to greatly improve the dynamic behavior of foil bearings. With a detailed analysis of these first results we propose primary physical explanation of this phenomena. r

Due to its heat integration utility, heat exchange reformer (HER) is suitable to use for PEMFC-based residential power generation system. Since dynamics response of reformer affects overall dynamics of fuel processing system, response of HER with step change in various input parameters also needs to be studied. In this study, we present an improved distributed dynamic model for HER which is capable of computing load following characteristics. The dynamic model consists of 20 partial differential equations which are discritized using spline collocation on finite elements. Resulting differential equations along with boundary conditions are solved by stiff solver which utilizes variable order method based on numerical differentiation formulae. Step variations in various input parameters are considered and dynamic response of HER is simulated at those variations. The results provide valuable information about dynamic nature of HER which can be used to frame suitable control strategy.

This study simulated the effects of thermal insulations on the ground, in the foundations and in the base floor in order to achieve as dry conditions as possible in outdoor air ventilated crawl spaces in a cold climate. The objectives of the study were to find out how the thermal capacity and resistance and the placement of insulation layers affect relative humidity (RH) in the crawl space. The possibilities to reduce the air change rate to very low levels corresponding to natural ventilation, and to control RH by minimising the thermal capacity present in the crawl space were simulated. Mold growth analyses were used as performance criteria to predict the acceptability of the hygrothermal conditions in the studied crawl spaces. Most of the simulations were carried out with a low U-value for the base floor which normally results in a low temperature and high RH in the crawl space during the summer. The results show that there are two alternative ways to use ground covers in combination with air change in order to achieve acceptable conditions in crawl spaces. First, a traditional thin layer of lightweight expanded clay aggregate (LWA) or expanded polystyrene (EPS) may be used, but in this case, the air change rate has to be increased in the summer at least to 1 ach. An alternative solution is to use thicker ground covers, such as at least 30 cm lightweight aggregate or 10 cm polystyrene, and a low air change rate of approximately 0.5 ach all the year round. This solution provides even lower RH values and mold growth index values because the thick ground covers effectively insulate the massive ground whereby the crawl space warms up quickly when the warm season starts.

Colloidal spheres driven through water along a circular path by an optical ring trap display unexpected dynamical correlations. We use Stokesian Dynamics simulations and a simple analytical model to demonstrate that the path's curvature breaks the symmetry of the two-body hydrodynamic interaction, resulting in particle pairing. The influence of this effective nonequilibrium attraction diminishes as either the temperature or the stiffness of the radial confinement increases. We find a well defined set of dynamically paired states whose stability relies on hydrodynamic coupling in curving trajectories.

A number of recent papers have focused on the role of real factors in accounting for the persistent effects of monetary shocks. These factors include habit persistence in consumption, variable capital utilization, and produced inputs. In this chapter, I focus on labor market rigidities that prevent unemployed workers from Þnding new jobs immediately and Þrms with job vacancies from Þlling them immediately. I employ dynamic simulations to investigate the role the job matching process plays in affecting the economy's adjustment to real and monetary shocks. By combining labor market rigidities with sticky prices, it is possible to study the relative roles of real and nominal rigidities in accounting for the impact of monetary shocks.

We investigate the stability of barium sulphate precipitation in an ideally mixed reactor under stoichiometric conditions. The process is modelled by a population balance equation describing the crystal size distribution coupled with a system of integro-differential equations for the substances in solution. A reduction to a closed moment model is used to analyse the stability of equilibrium solutions. In a certain range of parameters an unstable equilibrium is detected by a numerical calculation of the eigenvalues of the moment system. In this case sustained oscillations of the crystal size distribution are observed in numerical simulations. The numerical results are compared to data obtained from chemical experiments.

In this paper the optimization of a crank-rocker mechanism driven by an asynchronous electrical motor is presented. The optimization is based on the analysis of the sensitivity of the objective function in relation to the design variables. The objective function is determined by performing a dynamic simulation of the mechanism. Finally a numerical example of crank-rocker mechanism optimization is presented.

I describe a procedural animation system that uses techniques from behavior-based robot control, combined with a minimalist physical simulation, to produce believable character motions in a dynamic world. Although less realistic than motion capture or full biomechanical simulation, the system produces compelling, responsive character behavior. It is also fast, supports believable physical interactions between characters such as hugging, and makes it easy to author new behaviors.

Over the past few decades many vibration and signal analysis techniques have been investigated, developed, and used to provide operational response information about mechanical power transmission systems for monitoring and diagnosis of components and their worn/faulted condition. The presence of multiple sources of excitation and forcing in a complex distributed mechanical structure (rotor transmission shafting, gearing, bearings, casing, and foundation) presents problems for algorithms that are designed to present a single feature associated with a single fault mechanism. The consequence of the mechanical structures dynamic interaction is not always clear but an understanding of it is critical for the successful development of effective integral signal p rocessing algorithms and automated reasoning components used in CBM systems. As part of a combined experimental-theoretical analysis effort, ARL is investigating mechanical fault evolution in damaged rotating components. A dynamics model of the system using component fault models was developed for response simulations. Comparison of experimentally measured and simulated results of system vibratory responses allow physical insights into vibratory measurement sensor placement and specification, dynamic system response to a fault, and the development of fault detection signal processing algorithms. In this paper, the dynamics modeling of the gearbox rotor/bearing-foundation system using the Finite Element method is outlined and it's relevance to diagnostics and prognostics is highlighted.

The objective of this study was to dynamically simulate the response of vegetation distribution, carbon, and fire to the historical climate and to two contrasting scenarios of climate change in California. The results of the simulations for the historical climate compared favorably to independent estimates and observations, but validation of the results was complicated by the lack of land use effects in the model. The response to increasing temperatures under both scenarios was characterized by a shift in dominance from needle-leaved to broad-leaved life-forms and by increases in vegetation productivity, especially in the relatively cool and mesic regions of the state. The simulated response to changes in precipitation were complex, involving not only the effect of changes in soil moisture on vegetation productivity, but also changes in tree-grass competition mediated by fire. Summer months were warmer and persistently dry under both scenarios, so the trends in simulated fire area under both scenarios were primarily a response to changes in vegetation biomass. Total ecosystem carbon increased under both climate scenarios, but the proportions allocated to the wood and grass carbon pools differed. The results of the simulations underscore the potentially large impact of climate change on California ecosystems, and the need for further use and development of dynamic vegetation models using various ensembles of climate change scenarios.

This paper describes an application of multibody dynamics to the determination of global physical behavior patterns that mimic traditional empirical laws. The main idea is to sift out such patterns from virtual experiments carried out with a simulation package. The concrete investigation in this setting is the dynamics of trains colliding onto buffer stops. Using a rigid-body model with nonlinear couplers featuring hysteresis, it is shown that, for typical train constellations, the highest load at the buffer stops is almost independent of the number of coaches, and that the value and the location of the maximum force within the train does not increase from a particular train length on. These results are compared with traditional formulas for dimensioning of buffer stops used in rail-vehicle industry.

Planet formation models suggest the primordial main belt experienced a short but intense period of collisional evolution shortly after the formation of planetary embryos. This period is believed to have lasted until Jupiter reached its full size, when dynamical processes (e.g., sweeping resonances, excitation via planetary embryos) ejected most planetesimals from the main belt zone. The few planetesimals left behind continued to undergo comminution at a reduced rate until the present day. We investigated how this scenario affects the main belt size distribution over Solar System history using a collisional evolution model (CoEM) that accounts for these events. CoEM does not explicitly include results from dynamical models, but instead treats the unknown size of the primordial main belt and the nature/timing of its dynamical depletion using innovative but approximate methods. Model constraints were provided by the observed size frequency distribution of the asteroid belt, the observed population of asteroid families, the cratered surface of differentiated Asteroid (4) Vesta, and the relatively constant crater production rate of the Earth and Moon over the last 3 Gyr. Using CoEM, we solved for both the shape of the initial main belt size distribution after accretion and the asteroid disruption scaling law Q * D . In contrast to previous efforts, we find our derived Q * D function is very similar to results produced by numerical hydrocode simulations of asteroid impacts. Our best fit results suggest the asteroid belt experienced as much comminution over its early history as it has since it reached its low-mass state approximately 3.9-4.5 Ga. These results suggest the main belt's wavy-shaped size-frequency distribution is a "fossil" from this violent early epoch. We find that most diameter D 120 km asteroids are primordial, with their physical properties likely determined during the accretion epoch. Conversely, most smaller asteroids are byproducts of fragmentation events. The observed changes in the asteroid spin rate and lightcurve distributions near D ∼ 100-120 km are likely to be a byproduct of this difference. Estimates based on our results imply the primordial main belt population (in the form of D < 1000 km bodies) was 150-250 times larger than it is today, in agreement with recent dynamical simulations.

Safety critical software requires integrating verification techniques in software development methods. Software architectures must guarantee that developed systems will meet safety requirements and safety analyses are frequently used in the assessment. Safety engineers and software architects must reach a common understanding on an optimal architecture from both perspectives. Currently both groups of engineers apply different modelling techniques and languages: safety analysis models and software modelling languages. The solutions proposed seek to integrate both domains coupling the languages of each domain. It constitutes a sound example of the use of language engineering to improve efficiency in a software-related domain. A model-driven development approach and the use of a platform-independent language are used to bridge the gap between safety analyses (failure mode effects and criticality analysis and fault tree analysis) and software development languages (e.g. unified modelling language). Language abstract syntaxes (metamodels), profiles, language mappings (model transformations) and language refinements, support the direct application of safety analysis to software architectures for the verification of safety requirements. Model consistency and the possibility of automation are found among the benefits.

Using the finite element technique, the stress characteristics within the mandible are evaluated during a dynamic simulation of the implant insertion process. Implantation scenarios considered are implant thread forming (S1), cutting (S2) and the combination of forming and cutting (S3). Ultimately, the outcome of this study will provide an improved understanding of the failure mechanism consequential to the stress distribution characteristics in the mandible during the implantation process. Material and Methods: Parameters considered herein include bone cavity diameters of 3.9mm (for S2), 4.25mm (for S1) and a tapered cavity of diameters linearly varying from 3.9 to 4.25mm (for S3). The bone-implant system is modelled using three-dimensional tetrahedral elements. Idealised bone and implant interaction properties are assumed. The stress profiles in the mandible are examined for all bone cavity diameters. Results and Conclusion: The stress levels within the cancellous and cortical bone for S1 are significantly reduced when compared to scenarios S2 and S3. For S3, during the initial insertion steps, the stress is marginally less than that for S2. Close to the end of the insertion process, the stress level within the cancellous bone in S3 is approximately half way between that of S1 and S2. Generally for all scenarios, as the insertion depth increases the stress increases less significantly in the cortical bone than in the cancellous bone. Overall, different implant surface contact areas are the major contributors to the different stress characteristics of each scenario.

This paper presents a dynamic simulator of water-in-tube boilers with natural recirculation, the kind of equipment widely used in industries for steam generation either as a source of power or for providing heating capabilities in process plants. The development is based on a combination of two non-linear models, one for the evaporation in the vertical tubes and the other for the phase separation in the steam drum. An application is made to the boiler of a 30 MW thermoelectric power plant and the results are discussed. The dynamic responses of all variables show the consistency of the model representation with the expected behavior, including the effects of a PI level control adjusted using classic Ziegler -Nichols tuning rules.

: When under influence of dynamic events such as jumping from a diving board or bouncing off a wall, our method using morph targets produces deformations consistent with Herbert's morph targets defined in (a). The fat morph target is associated with a crunched pose to mimic a bulging belly (and only for that pose). As shown in (b), the simulation without dynamic morph targets does not show bulging, whereas our method shown in (c) does. Image (d) is a snapshot of our run-time diving demo.

China is home to one-fifth of the world's population and that population is increasingly urban. The landscape is also urbanizing. Although there are studies that focus on specific elements of urban growth, there is very little empirical work that incorporates feedbacks and linkages to assess the interactions between the dynamics of urban growth and their environmental impacts. In this study, we develop a system dynamics simulation model of the drivers and environmental impacts of urban growth, using Shenzhen, South China, as a case study. We identify three phases of urban growth and develop scenarios to evaluate the impact of urban growth on several environmental indicators: land use, air quality, and demand for water and energy. The results show that all developable land will be urban by 2020 and the increase in the number of vehicles will be a major source of air pollution. Demand for water and electricity will rise, and the city will become increasingly vulnerable to shortages of either. The scenarios also show that there will be improvements in local environmental quality as a result of increasing affluence and economic growth. However, the environmental impacts outside of Shenzhen may increase as demands for natural resources increase and Shenzhen pushes its manufacturing industries out of the municipality. The findings may also portend to changes other cities in China and elsewhere in the developing world may experience as they continue to industrialize.

A dynamic model of a discrete reversible fuel cell (RFC) system has been developed in a Matlab Simulink ® environment. The model incorporates first principles dynamic component models of a proton exchange membrane (PEM) fuel cell, a PEM electrolyzer, a metal hydride hydrogen storage tank, and a cooling system radiator, as well as empirical models of balance of plant components. Dynamic simulations show unique charging and discharging control issues and highlight factors contributing to overall system efficiency.

In this paper we present the synthesis of novel reactionless spatial three-degrees-of-freedom (3-DoF) and 6-DoF mechanisms without any separate counter-rotation, using four-bar linkages. Based on the conditions of dynamic balancing of a single planar four-bar linkage developed elsewhere, the spatial problem is shown to be equivalent to ensuring that the inertia tensor of reactionless four-bar linkage(s), which is(are) attached on the moving link of a reactionless fourbar linkage, remains constant while moving. The reactionless conditions for planar four-bar linkages undergoing spatial motion are first given. Then, reactionless spatial 3-DoF mechanisms using four-bar linkages are synthesized. A numerical example of the reactionless spatial 3-DoF mechanism is given and, with the help of the dynamic simulation software ADAMS, it is shown that the mechanism is reactionless for arbitrary trajectories. Finally, this mechanism is used to synthesize reactionless 6-DoF parallel mechanisms.

During open-heart surgery roller pumps are often used to keep the circulation of blood through the patient body. They present numerous key features, but they suffer from several limitations: (a) they normally deliver uncontrolled pulsatile inlet and outlet pressure; (b) blood damage appears to be more than that encountered with centrifugal pumps.A lumped parameter mathematical model of a roller pump (Sarns™ 7000, Terumo CVS, Ann Arbor, MI, USA) was developed to dynamically simulate pressures at the pump inlet and outlet in order to clarify the uncontrolled pulsation mechanism. Inlet and outlet pressures obtained by the mathematical model have been compared with those measured in various operating conditions: different rollers’ rotating speed, different tube occlusion rates, and different clamping degree at the pump inlet and outlet.Model results agree with measured pressure waveforms, whose oscillations are generated by the tube compression/release mechanism during the rollers’ engaging and disengaging phases. Average Euclidean Error (AEE) was 20 mmHg and 33 mmHg for inlet and outlet pressure estimates, respectively. The normalized AEE never exceeded 0.16.The developed model can be exploited for designing roller pumps with improved performances aimed at reducing the undesired pressure pulsation.

A key prerequisite for effective GIS based Infiltration Excess Overland Flow (IEOF) simulation and visualization is good knowledge of GIS core concept and prediction of soil infiltration rates due to impervious area coverage. The success or failure for a GIS based IEOF simulation and visualization resides initially with the georeference system used. Cartographers have long complained about the poor quality of the output from GIS, which generally today is not due to limitation of the GIS itself, but to lack of understanding of cartographic principles among hydrologists and environmentalists. Implementation of soft geo-objects representing flow elements such as streams, mudflows and runoff provides better dynamic visualization in terms of velocity and direction. Inclusion of volumetrical overland flow would offer substantial effort towards determining volume of runoff that hits the flood-plain areas, estimating channel flow capacity, routing and diversions to reduce flood disasters realistically. With rapid growth of urbanization, industrialization and climate change, previous historical runoff and infiltration rate would provide improper guide for the future enhanced visualization of the current 2D land use surface to improve future hydrologic impact assessment. This study aims to visualize the influence of georeferencing towards IEOF simulation represented by volumetric soft geo-objects dynamically within 3D environment, which is driven by physically based Green-Ampt method. Visualization is analyzed by focusing on infiltration and overland flow process using conformal based Malaysian Rectified Skew Orthomorphic (MRSO) and equidistant based Cassini-Soldner projection. Appropriate usage of georeferencing system to visualize 3D dynamic IEOF simulation may obtain high demands from civil engineers, environmentalists, town planners, geologists and meteorologists as base for producing scientific results of flood management control, sustainability for long-term development purposes, stream restoration, rehabilitation and hydrologic impact assessment.

This paper presents a preliminary study concerning a multibody model of the desmodromic valve train used in the Ducati MotoGP engines. The desmodromic mechanism has a positive cam that causes the dynamic effects to be partly different from common valve trains, where the valve spring plays an important role. The presented model includes only one camvalve mechanism. In a further step of the research, it will be possible to develop and expand the model by introducing the other cam-valve mechanisms and other mechanical parts that compose the system in order to obtain a complete model of the valve train. In the first part of this work, the generation of the cam profiles is explained. The second part is focused on the description of the multibody model employed for the dynamic simulations. Finally, the experimental validation is presented and discussed. The comparison between the numerical results and the experimental data is encouraging even if it shows that the effectiveness of the model is not completely achieved. Therefore, it will be necessary to improve the model by including the presence of other mechanical parts of the valvetrain, as well as other important dynamic effects as, for example, the link flexibility.

A method and a model for analyzing visually and quantitatively mutual shading between buildings is presented. The method allows fast and efficient calculation of the ratio between insolated and total surface areas of any given examined object that is shaded by other irregular and nonplanar elements. The calculation of this ratio is carried out for all the months and hours for which either shading or insolation is required. The information obtained may serve as hourly input data for any dynamic simulation model which evaluates the thermal performance of the different external or internal shading systems. For a visual and a qualitative evaluation of the shadows among buildings, the suggested model permits a very realistic representation, in which the light source is defined according to the azimuth and the altitude of the sun at the particular time of examination. The self shading and brightness of the different surfaces and the shadows cast by the different elements at the designated time are then generated and can be evaluated visually. The method is demonstrated by a case study.

An experimental and theoretical study of forced unsteady-state operation of trickle-bed reactors in comparison to the steady-state operation is the subject of this paper. It is well known that changes in the control variables influence the regime and the performance of trickle-bed reactors. In this study as one example for a forced periodic operation of a trickle-bed reactor an unsteady-state technique was used in which the catalyst bed is contacted periodically with different liquid flow rates. The unsteady-state operation was considered as square-waves cycling liquid flow rate at the reactor inlet. The hydrogenation of alpha-methylstyrene to cumene: C 6 H 5 (CH 3 ) = CH 2(L) + H 2(G) → C 6 H 5 CH(CH 3 ) 2(L) over a Palladium-catalyst (0.7% Pd/ -Al 2 O 3 ) was selected as a model reaction. The experimental results of the alpha-methylstyrene hydrogenation in a laboratory-scale trickle-bed reactor showed, that the reactor performance can be significantly improved by feed liquid flow modulation.