bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity Testing Revisited: The Case of Sol-Gel Transition
Authors: Omegna Federica , Genta Gianfranco , Barini Emanuele M. , Marchisio Daniele L. , Levi Raffaello
Published: July 2009

Classical sensitivity testing addresses mainly problems where the level of one stimulus only governs an abrupt transition in output, or response. Both parametric and nonparametric methods developed, and successfully applied over last century to tackle such problems, provide estimates of critical levels beyond which an item will either respond, or not, to a single stimulus, and of related statistics. However classical methods sometimes may not readily provide an answer, namely when more than one stimulus may reach critical level, and either singularly or jointly trigger transition. Factorial and response surface designs, adequate when dealing with continuous responses, may not perform as well for transition threshold estimation. A practical case at hand in chemical engineering concerns the production, through hydrolysis of a specific precursor, of titania sols and gels that find industrial use as additive for paints, concrete and other building materials due to its optical, photo-catalytic and super-hydrophilic properties. Particles formation and aggregation — controlled by varying the primary process parameters, namely initial alkoxide concentration, water to alkoxide and acid to alkoxide ratios, mixing conditions — may yield either stable, transparent nanometric sols, or monolithic gels, where aggregation of nanometric particles produces a final ceramic object. Depending on the application, one of the two products may be desirable, and therefore it is crucial to control the final product properties. Aggregation kinetics and physical properties of sols, and sol to gel transition, were found to depend strongly upon several factors, that is water to alkoxide initial concentration ratio, acid to alkoxide initial concentration ratio, and their interaction. The approach developed in order to estimate parameters pertaining to transition, and related uncertainty, is presented in the paper, and discussed in the light of experimental results.
Neural Network Predictive Control for Piezoelectric Smart Structures
Authors: Zhang Jingjun , Wang Ercheng , Gao Ruizhen
Published: July 2009

The piezoelectric smart structure is a force-electric coupling structure, and piezoelectric patches can not be patched ideally, so it is difficult to build the accurate mathematical model of piezoelectric smart structure. The traditional vibration control methods depend on the structural mathematical model, and the control result is unsatisfactory. Considering this problem, this paper introduces the nonlinear generalized predictive control algorithm based on neural network predictive model into piezoelectric smart structure. Because of the difficulties of building the mathematical model and extracting dynamic data from experiment, the finite element software (ANSYS) is employed to analyze and obtain the dynamic response data of piezoelectric smart structure through modal analysis and transient analysis. Neural network predictive model of structure is built through off-line training on the basis of the data. The nonlinear generalized predictive control based on neural network has a better ability to solve complex nonlinear problem. Then the author introduces the Neural Network Based System Identification Toolbox (NNSYSID) and Neural Network Based Control System Design Toolkit (NNCTRL), which are two special toolboxes for designing neural network control system and can save lots of time for designers who can commit themselves to sixty-four-dollar question. At last, the author shows the method through a case. A cantilever beam which surface is boned piezoelectric patches used for sensor and actuator respectively is analyzed by ANSYS and controled by the neural network predictive control algorithm on the platform of NNSYSID and NNCTRL. This is a simple and effective method for designers to solve the vibration control problem of piezoelectric smart structure.
Packing Density Insensitive Contact Detection Algorithm for Molecular Dynamics Simulations
Authors: Munjiza A.
Published: July 2009

Molecular dynamics problems involve large numbers of interacting atoms requiring CPU and RAM intensive computational simulations. A contact detection algorithm which detects pairs of interacting atoms is a key component of these simulations. This paper presents a contact detection algorithm that is completely insensitive to packing density in terms of both RAM and CPU requirements — thus permitting near vacuum conditions and dense gases or liquids to coexist in the same simulation. In addition, both CPU and RAM requirements are proportional to the total number of atoms.
Motion Control on Symmetrical Phase Polyhedrons
Authors: Pilishkin V. N.
Published: July 2009

While controlling aircrafts one of the most relevant problems is a problem of the desired (programmed) motion regimes realization. While solving this problem we encounter many obstacles including first of all the existence of various indeterminacies, which prevent us from gaining the full information about aircraft’s model. For example: structural and parametric indeterminacies of aircrafts simulator; external and internal indeterminacies, determined by external disturbances and by disturbances in indicators channels.
A New Instrument for Tensile Testings of Thin Free Standing Films at High Strain Rates
Authors: Ben-David Eran , Shilo Doron , Rittel Daniel , Elata David
Published: July 2009

The design of more reliable and sophisticated Micro Electro Mechanical Systems (MEMS) relies on the knowledge, understanding, and ability to control their mechanical response. In recent years, enormous progress has been made in developing new measurement techniques for studying the mechanical response of sub-micro scale specimens. However, there is still a lack of knowledge and testing techniques regarding the response of MEMS structures to mechanical shocks, which can appear during fabrication, deployment, or operation. We present an instrument for testing the mechanical response of thin free standing films under uniaxial tensile stress at high strain rates of up to 2×103 sec-1. The experimental system consists of a micro-device, which contains the freestanding specimen, and an external system, which includes instrumentation for measuring its mechanical response. The components of the external system are controlled by a single interface, and allow for a variety of displacement profiles to be applied to the specimens. All the instrumentation operates at high sampling rates (above 1 MHz) to allow for high strain rate application. The freestanding specimen is produced by MEMS fabrication techniques on a micro-device that also includes S-springs to protect the specimen and aluminum grating lines for measuring the displacement. One side of the chip is pulled by a piezoelectric translation stage, which allows controlling the displacement with a nanometric resolution and applying high velocities and accelerations. The specimen displacement is monitored by an optical encoder device that measure the displacement of the aluminum grating located on the micro-device close to the specimen with an accuracy of about 10 nm. The load is determined by measuring the charge on a piezoelectric PMN-30%PT shear plate, which is connected to the pin that holds the micro-device. The new instrument is applied for studying the response of thin aluminum films with thickness of 0.5–1 μm, width that varies between 5 to 50 μm, and length of 120 μm. The mechanical response of these specimens is measured at different strain rates and is compared to measurement done by nanoindentation.
In-Situ Investigation of Plasticity at Nano-Scale
Authors: Greer Julia R. , Kim Ju-Young , Brinckmann Steffen
Published: July 2009

Mechanical behavior of crystals is dictated by dislocation motion in response to applied force. While it is extremely difficult to directly observe the motion of individual dislocations, several correlations can be made between the microscopic stress-strain behavior and dislocation activity. Here, we present for the first time the differences observed between mechanical behavior in two fundamental types of crystals: face-centered cubic, fcc (Au, Cu, Al, Ni, etc.) and body-centered cubic, bcc (W, Cr, Mo, Nb, etc.) with sub-micron dimensions subjected to in-situ micro-compression in SEM chamber. In a striking deviation from classical mechanics, there is a significant increase in strength as crystal size is reduced to 100nm; however in gold crystals (fcc) the highest strength achieved represents 44% of its theoretical strength while in molybdenum crystals (bcc) it is only 7%. Moreover, unlike in bulk where plasticity commences in a smooth fashion, both nano-crystals exhibit numerous discrete strain bursts during plastic deformation. These remarkable differences in mechanical response of fcc and bcc crystals to uniaxial micro-compression challenge the applicability of conventional strain-hardening to nano-scale crystals. We postulate that they arise from significant differences in dislocation behavior between fcc and bcc crystals at nanoscale and serve as the fundamental reason for the observed differences in their plastic deformation. Namely, dislocation starvation is the predominant mechanism of plasticity in nano-scale fcc crystals while junction formation and subsequent hardening characterize bcc plasticity, as confirmed by the microstructural electron microscopy. Experimentally obtained stress-strain curves together with video frames during deformation and cross-sectional TEM analysis are presented, and a statistical analysis of avalanche-like strain bursts is performed for both crystals and compared with stochastic models.
A Semi Empirical Methodology for Performance Estimation of a Double Pipe Finned Heat Exchanger
Authors: Rao G. Arvind , Levy Yeshyahou
Published: July 2009

Finned tubes are one of the most widely used means of passively enhancing the heat transfer in circular tubes. Many investigators have proposed different correlations for predicting the performance of such heat exchangers based on their experimental investigations. However, the practical usage of such correlations is limited because of the variety of parameters that can influence Nusselt number and friction factor. Most of the correlations either have been developed with limited databases, or are geometry specific. Using CFD for analyzing performance of such heat exchangers is very computational intensive and hence cannot practically be applied for design optimization purposes. On the other hand, empirical correlations have many limitations in terms of their applicability. The objective of the present article is to present a physically based model for evaluating heat transfer and frictional loss for an internally and / or externally finned double pipe heat exchanger that can be applied in a wide range of operating conditions of practical importance. This paper describes a simple semi-empirical-numerical methodology to evaluate heat transfer and pressure drop characteristics in a finned tube heat exchanger with internal and/or external fins. Conduction and turbulent forced convection are the prominent modes of heat transfer. In order to resolve the operational characteristics of double pipe finned heat exchangers, a numerical methodology is presented which uses well known existing correlations for flow in a smooth pipe and flow over a flat plate. The method of successive substitution is used to solve the problem numerically. The proposed methodology is applied to some simple cases and the results compare well with existing data and correlations available in the literature. It is found that the addition of fins to such double pipe heat exchangers reduce the Nusselt Number; however the corresponding heat transfer rate is enhanced owing to the increase in the overall heat transfer area.
Improvement of Rolling Contact Fatigue Life by a Preliminary Loading in Elastic-Plastic Domain
Authors: Cretu Spiridon
Published: July 2009

An analysis model has been developed to model the nonlinear strain rate dependent deformation of rolling bearing steel stressed in the elastic-plastic domain. The model is developed in the frame of the incremental theory of plasticity by using the von Mises yield criterion and Prandtl-Reuss equations. By considering the isotropic and non-linear kinematic hardening laws of Lemaitre-Caboche, the model accounts for the cyclic hardening phenomena. To attain the final load of each loading cycle, the two bodies are brought into contact incrementally. For each new load increment new increments for the components of stress and strain tensors, but also increments of residual stresses, are computed for each point of the 3D mesh. Both, the new contact geometry and residual stresses distributions, are further considered as initial values for the next loading cycle, the incremental technique being reiterated. The cyclic evaluation process of both, plastic strains and residual stresses is performed until the material shakedowns. The experimental part of the paper regards to the rolling contact fatigue tests carried out on two groups of line contact test specimens and on two groups of deep groove ball bearings. In both cases, the experimental data reveal more than two times greater fatigue life for the group with induced residual stresses versus the life of the reference group. The von Mises equivalent stress is considered in Ioannides-Harris rolling contact fatigue model to obtain theoretical lives. The theoretical analysis revealed greater fatigue lives for the test specimens and for the ball bearings groups with induced residual stresses than the fatigue lives of the corresponding reference groups.
Development of Free Surface Roughness in Expanding/Contracting Cylinders
Authors: Alexandrov Sergei , Manabe Ken-Ichi , Furushima Tsuyoshi
Published: July 2009

Microforming is a modern technology for fabricating very small metallic parts, such as micro-tubes, required in many sectors of industry. Free surface roughness of such components is a very important parameter since the roughness can be considered as the variation of component dimensions in this case. It is therefore of importance to understand an effect of process parameters and parameters of material models used to describe the evolution of roughness on the final result of theoretical predictions. To this end, it is possible to study the solution behavior of a simple problem even if it is not feasible for experimental verification. In the present paper, the solution to a classical problem of plasticity, expansion/contraction of a hollow cylinder, is combined with a finite element technique to predict the evolution of roughness at the free surface.
Adhesive Wear of Duplex-Treated Tool and Structural Steels
Authors: Sucha´nek Jan , Jurcˇi Peter
Published: July 2009

Thin ceramic coatings deposited on the surface of tools and machine parts by PVD methods improve considerably their tribological properties. However these hard brittle coatings can be damaged rapidly if plastic deformation initiates in the substrate near the coating-substrate interface when subject to a relatively high load. The logical way how to treat such problems is improvement of the mechanical characteristics of subsurface layers by heat treatment or thermo-chemical treatment such as plasma nitriding. The typical duplex process involves plasma nitriding and PVD coating treatment of steels. Thickness of the nitride layers depends on the activity of nitrogen in the plasma, process temperature and time. The type and thickness of nitrides can influence considerably the quality of the deposited PVD coatings and their adhesion to a nitrided substrate. High-speed steels and Cr-V ledeburitic steels were plasma nitrided and duplex-coated (pulse plasma nitriding + PVD TiN or CrN coating) at various combinations of processing parameters. The wear resistance of the non-nitrided, PVD coated and duplex-coated steel surface was examined by ring-on-plate and plate-on-plate tribological testers. The effect of subsequent PVD–coating performed on plasma nitrided specimens can be considered as very positive when the specimens were severe loaded. The tested duplex treated low-alloy steel 31CrMoV9 was pulse plasma nitrided and then coated by different PVD coatings (TiN, CrN, TiAlN and (CrN-TiN)x3). The results of tribological tests (ring-on-plate tribometer) confirmed the high wear resistance of duplex treated steels.
Laboratory Support for Service Engineering and Design
Authors: Meiren Thomas , van Husen Christian , Karni Reuven
Published: July 2009

Services are frequently developed unsystematically; and new ideas are not sufficiently conceptualized and tested. This results in expensive improvement measures at a later stage during the operations phase. This challenge is addressed through the recent launching of the “ServLab” facility at the Fraunhofer Institute for Industrial Engineering. It incorporates a stage for acting out service scenarios, furnishings to represent the physical environment, and a large virtual reality (VR) backdrop to simulate the “servicescape”. Situations are played out by professional actors or by employees and invited customers. In particular, the ServLab makes it possible to test services comprehensively. It is just this problem which has not been solved satisfactorily for a long time — neither in science nor in practice. It is still common for concepts to be developed “round the green table”, followed by an attempt to implement them directly. Potential mistakes are discovered very late or not at all, resulting in expensive rectification activities. The ServLab makes it possible to visualise new service concepts (using virtual reality), create an environment that is as close as possible to reality (e.g. by playing back sounds or introducing odours) and to rehearse the interaction between customers and employees with the support of actors (service theatre).
Three-Dimensional Stress Intensity Factors for Arrays of Radial Cracks Emanating From the Inner Surface of a Thick-Walled Spherical Pressure Vessel
Authors: Perl M. , Bernstein V.
Published: July 2009

Some spherical pressure vessels are manufactured by methods such as the Integrated Hydro-Bulge Forming (IHBF) method, where the sphere is composed of a series of double curved petals welded along their meridional lines. Such vessels are susceptible to multiple radial cracking along the welds. For fatigue life assessment and fracture endurance of such vessels one needs to evaluate the Stress Intensity Factors SIF distribution along the fronts of these cracks. However, to date, only two-dimensional SIFs for one through the thickness crack in a thin spherical shells is available. In the present paper, mode I SIF distributions for a wide range of lunular and crescentic cracks are evaluated. The 3-D analysis is performed, via the FE method employing singular elements along the crack front, for three sphere geometries with outer to inner radius ratios of η = Ro/Ri = 1.1, 1.7, and 2.0. SIFs are evaluated for arrays containing n = 1–20 cracks,; for a wide range of crack depth to wall thickness ratio, a/t, from 0.025 to 0.8; and for various ellipticities of the crack, i.e., the ratio of crack depth to semi crack length, a/c, from 0.2 to 1.5. The obtained results clearly indicate that the SIFs are considerably affected by the three-dimensionality of the problem and by the geometrical parameters: the geometry of the sphere – η, the number of cracks in the array – n, the depth of the crack – a/t, and its ellipticity – a/c.
Recovering, Treating and Using Waste From Expandable Polystyrene by Mechanical Breakage Process of Manufacturing Composite Materials
Authors: Pop Petru A. , Ungur Patricia A. , Patcas Elisabeta , Ungur Petru
Published: July 2009

The paper has presented the experimental result obtaining at recovery, treating and using of industrial waste from expandable polystyrene, under shaped of flakes and distortion grains, resulting from manufacturing of thermo and phonic-insulating panels by composite materials manufacturing. The recovering process of waste has done by grinding and mechanical breakage of flakes and grains from expandable polystyrene by disintegrate machines or mills with rotor and cutters with higher spindle speeds. The recovering has realized by using the retrieval as reinforced in composition of lightweight composite materials with matrix from air binding on base of alpha-plaster for modeling. The new material resulted is characterized from small density, great porosity, good mechanical strength and could be used with success in orthopedic technique, or for manufacturing of phonic and thermo insulating panels. The breakage expandable polystyrene had irradiated in air with gamma ray by radioactive isotopes of 137C and 60Co at experimental dozes can be uses as added in therapeutically mud for non-conventional treatment of some rheumatic disorders. This technical paper has presented some receipts of composite materials on base of alpha-plaster for modeling and reinforced expandable polystyrene, which have higher characteristics as lightweight and great porosity necessary for orthopedic gypsum, being use in dressing and orthopedic corsets. These materials are very accessible as cost price, assuring a better respiration of skin and lower pressure about weak organs subjected orthopedic treatment, improving patient’s comfort.
Experiences With International Project Teams Working With Robot Design
Authors: Friesel Anna
Published: July 2009

This paper summarizes the activities, contents and overall outcomes of our experiences with international project teams working with different engineering projects, in particular the Interdisciplinary Project on fourth semester (TVP4E). The TVP4E course combines the theory and practical design of small autonomous robots. The theoretical part includes mathematical modeling, system dynamics, control theory, digital and analogue electronics, and microprocessors. The practical project is to design an autonomous robot performing two tasks: compulsory task decided by the teachers and the free task decided by students. The success of this particular fourth semester project inspired us to start other international project semesters. Globalization makes it necessary to cooperate on an international platform. A great contributor to globalization is the student mobility program within the EU, like the Socrates-Erasmus program. At the Copenhagen University College of Engineering we have more then 50 active Socrates-Erasmus agreements. Beside that we have bilateral agreements with many non-European countries. Usually the exchange students come to us after 2–3 years of studying in their home countries. Their prerequisites are in most cases the basics of mathematics and physics, but there is very big variety in their practical skills, like electronics and programming. Some of them do not have much experience in working with projects. The challenge of supervising the international teams is to motivate the students with different prerequisites to study the theory and work together with other students from very different cultures with a practical engineering project. In conclusion we describe the benefits from this program to all of us: students, teachers and the universities.
Deformation Behavior of a Shape Memory Alloy: Nitinol
Authors: Daly Samantha , Bhattacharya Kaushik , Ravichandran Guruswami
Published: July 2009

Nickel-Titanium, commonly referred to as Nitinol, is a shape-memory alloy with numerous applications due to its superelastic nature and its ability to revert to a previously defined shape when deformed and then heated past a set transformation temperature. While the crystallography and the overall phenomenology are reasonably well understood, much remains unknown about the deformation and failure mechanisms of these materials. These latter issues are becoming critically important as Nitinol is being increasingly used in medical devices and space applications. The talk will describe the investigation of the deformation and failure of Nitinol using an in-situ optical technique called Digital Image Correlation (DIC). With this technique, full-field quantitative maps of strain localization are obtained for the first time in thin sheets of Nitinol under tension. These experiments provide new information connecting previous observations on the micro- and macro-scale. They show that martensitic transformation initiates before the formation of localized bands, and that the strain inside the bands does not saturate when the bands nucleate. The effect of rolling texture, the validity of the widely used resolved stress transformation criterion, and the role of geometric defects are examined.
3D Multi-Scale Topography Analysis in Specifying Quality of Honed Surfaces
Authors: Sabri Leila , Mezghani Sabeur , El Mansori Mohamed , Le Lan Jean-Vincent , Dal Negro Tommaso
Published: July 2009

The quality of the surface texture on cylinder liners of engines has an important influence on oil consumption and running performance. This texture is generated with a succession of three honing operations (rough, finishing and plateau honing). These honing steps are difficult to optimize due to the large number of process variables (Velocity of the rotational motion, velocity of the axial motion ...) and their complex interrelation. This paper discusses the use of the multiscale topographic parameter of the honing process as a new concept to identify the relation between the process variables and the resulting performances in terms of form and surface finish. To achieve this objective, a multi-scale decomposition method of surface topography based on 2D continuous wavelets transform was performed to analyze the evolution of the topographic honing. This approach also shows a good indication of the dependence between the honing steps and the roughness scales. Finally, it provides an efficient tool to predict the surface characteristics corresponding to given process variables and can be extended to optimize other multi-stage abrasive machining processes.
Decomposition and Analysis of Non-Stationary Dynamic Signals Using the Hilbert Transform
Authors: Feldman Michael
Published: July 2009

This paper describes a new technique, called the Hilbert Vibration Decomposition method, dedicated to decomposition of non-stationary wideband dynamic signals. Using the Hilbert transform in the time domain, we extract a number of elementary oscillating components of the initial signal, who’s both the instantaneous frequency and envelope can vary in time. Modeling examples of decomposition of non-stationary signals are included.
Analysis of Goertler Instabilities in the IFMIF Li-Target Flow
Authors: Gordeev Sergej , Heinzel Volker
Published: July 2009

The International Fusion Materials Facility (IFMIF) uses a high speed Lithium (Li) free surface flow as a target, which is hit by two deuteron beams having each a power of 5 MW. The major function of the Li target is to provide a stable Li surface layer for the production of an intense neutron flux, to remove by forced convection the beam energy deposited in the Li layer and to avoid an overheat of the back wall structure beyond material sustainable limits. The target flow is conditioned by sophisticated shaped nozzle. Downstream the nozzle the liquid metal flows along a concave shaped back-wall in order to generate an increased pressure within the Lithium layer, which elevates the boiling temperature of the liquid. This article describes an analytical and numerical fluid dynamic study of the secondary liquid motions potentially occurring due to the concave shaped wall as well as its impact on the temperature distribution within the liquid lithium. First, the secondary flow distributions appearing in a turbulent flow along a curved wall are analyzed, where the major attention is paid to Goertler vortices, which emerge exceeding a critical flow velocity as a convective instability due to centrifugal forces. Further, a large-eddy simulation (LES) of the turbulent flow along the back-wall is conducted and the obtained data are compared to experiments. The results show that both the formation of the Goertler vortices as well as their decay are reasonably well predicted by the simulation. After the validation of the LES method the simulation has been transferred to the lithium target geometry at IFMIF standard operation conditions assuming decreased lithium layer thicknesses down to 23 mm. In this context besides the LES a conventional fluid dynamic computations based on the Reynolds-averaged turbulence model have been performed. The results show that the Reynolds-averaged models are not capable to predict the occurrence of Goertler vortices as the LES does. The formation of the Goertler vortices, however, yields to hot spots at the back wall which can reach temperature rises of more than 100°C compared to the nominal case.
Perceptuo-Motor Transparency in Bilateral Teleoperation
Authors: Nisky Ilana , Mussa-Ivaldi Ferdinando A. , Karniel Amir
Published: July 2009

In bilateral teleoperation, the operator holds a local robot which determines the motion of a remote robot and continuously receives delayed force feedback. Transparency is a measure of teleoperation system fidelity. The ideal teleoperator system is the identity channel, in which there is neither delay nor distortion. During the last decades transparency was widely analyzed using two-port hybrid representation of the system in Laplace domain. Such representations define hybrid matrix that maps between the transmission channel inputs and outputs. However, in measuring transparency one should consider also the human operator, and therefore we propose a multidimensional measure of transparency which takes into account: i) Perceptual transparency: The human operator cannot distinguish when the teleoperation channel is being replaced by an identity channel. ii) Local Motor transparency: The movement of the operator does not change when the teleoperation channel is replaced by an identity channel. iii) Remote transparency: The movement of the remote robot does not change when the teleoperation channel is replaced by an identity channel. We hypothesize that by selecting filters and training protocol it is possible to obtain perceptually transparent teleoperation (i) and remote motor transparency (iii) without local motor transparency (ii), namely, to transparentize the system. We formally define the transparency error, analyze this process in the linear case, and simulate simplified teleoperation system according to typical experimental results in our previous studies about perception of delayed stiffness. We believe that these tools are essential in developing functional teleoperation systems.
Virtual Service System Engineering
Authors: Spath Dieter , Bauer Wilhelm , Dangelmaier Manfred
Published: July 2009

Virtual Engineering is well-known in product design and widely in use i. e. in the automotive industry. The “frontloading” approach uses simulation and visualization to improve planning and communication in the early phases of product development processes. Benefits are: more efficient development processes, better development quality in early stages, and avoidance of error costs. This contribution presents an extension to this approach: Virtual Service System Engineering. It is intended to precede the more traditional product development. The product is considered in a generalized way as hardware and/or software and/or service. The lab environment ServLab at Fraunhofer IAO for the development of such generalized products is described. ServLab combines a team room for service process engineering (1), an immersive 3D-interactive virtual environment for rapid prototyping of generalized products (2), and a stage for performing Service Theatre as part of the development and evaluation process (3). As pilot application project on redesigning the hotel check-in is presented and first experiences are reported.
Design and Simulation of Low Order Control Laws for High Order Thermal Models
Authors: Brand Ziv , Berman Nadav , Rodnay Guy
Published: July 2009

A method for designing small scale control laws for large scale thermal systems is proposed. For high order models, traditional control theory produces high order control laws, which are impractical to implement. Here, Balanced Truncation is used to reduce the order of the model, while preserving as much as possible the dynamical properties that are important for controller design. Then, a low order controller is designed by applying a standard linear quadratic optimal control design procedure on the reduced model. The small scale controller performance is tested by incorporating it in a simulation with the full scale model. A geometric approach is used, in order to propose that the norms that are defined on the input and output spaces of the system should be the same in the model reduction phase and in the optimal controller design phase. This way, the cost function of the optimal controller is taken into account during the model reduction phase. A reduced order observer which allows real time estimation of process values that cannot be directly measured can be easily designed. The input signals that are computed during closed loop simulation can be also used in real time open loop operation. Hence, the work has a pure computational aspect: calculate the heat fluxes that are required in order to track a temperature profile that is given for a set of output points. Integrating standard computational methods with standard control theory via the Balanced Truncation algorithm is proved to be a powerful tool.
Lubrication Analysis Between Piston and Cylinder in High Pressure Piston Pump Considering Circumferential Grooves and Viscosity Variation With Pressure
Authors: Park Tae-Jo
Published: July 2009

In this study, a theoretical study on the lubrication analysis of an axially moving tapered piston with circumferential grooves subjected to a large pressure gradient within cylindrical bore has been done. Taking into account viscosity variation with pressure, analytic expressions for the pressure distribution leakage are obtained solving modified one-dimensional Reynolds equation for the case that the cylinder and the multigrooved piston axis has uniform eccentricity. It is shown that the viscosity variation with pressure highly affect the pressure distribution, lateral force acting on piston and leakage flow rate. Numerical solutions of two-dimensional Reynolds equation are also presented to confirm the validity of the analytical results. It is recommended that the piston used in various piston pumps should be tapered toward its high pressure end.
Shaping of the Face Worm Gear by Means of the Single Edge Cutting Tool
Authors: Staniek Roman
Published: July 2009

The theoretical basics of forming the face toothings in flat wheels of spiroid gears by means of a single cutting edge tool, using NC machine tools, have been presented in the paper. Based on kinematics - geometrical formulas, there is described a geometrical model of creating the tooth spaces, as well as a geometrical model of determination of the modification depth along the tooth line. Equations of the tooth line have been calculated, as well as mathematical formulas enabling the determination of the modification depth, assuming the correct matching of the worm with the flat worm wheel of the spiroid gear. Based on geometrical models and mathematical formulas algorithms have been elaborated in order to determine the envelope condition and modification depth of the tooth line. Then, on the basis of the algorithms computer programs have been elaborated that are going to be used to design the flat spiroid gears, as well as to calculate their geometrical dimensions. It has also been possible to illustrate the modification depth along the tooth line. The simulation results have been illustrated by the gear example. Finally two methods are presented of machining the face toothings in spiroid gears with a single edge-cutting tool: accurate and approximate ones. Based on the algorithms and programs a comparative simulation of both methods has been elaborated.
Free Vibration Characteristics of Composite Shells of Revolution With Variable Stiffness Coefficients
Authors: Kayran Altan
Published: July 2009

In the present study, the effect of initial winding angle, and the starting edge of the winding operation on the variation of the thickness, stiffness coefficients and undamped free vibration characteristics of filament wound composite shells of revolution are investigated. Filaments are assumed to be placed along the geodesic fiber path on the surface of the shell of revolution resulting in the variation of the stiffness coefficients and thickness along the axis of the composite shell of revolution with general meridional curvature. The study is performed by a semi-analytical solution method which exploits the combination of the numerical integration technique, and a modified frequency trial method. The governing shell of revolution equations comprise the full anisotropic form of the constitutive relations, including first order transverse shear deformation, and all components of translatory and rotary inertia. Results are obtained for conical and spherical shells of revolution manufactured by the filament winding process, and the effect of the winding pattern on the vibration characteristics of shells of revolution is investigated thoroughly.
Experimental Investigation of Melting in Vertical Circular Tubes
Authors: Fraiman L. , Benisti E. , Ziskind G. , Letan R.
Published: July 2009

The present study explores experimentally the process of melting of a phase change material (PCM) in vertical circular tubes. The study is performed with a commercially available paraffin-type material with the melting point of about 28 degrees Celsius. The experiments are conducted using vertical tubes of four different diameters, filled with the PCM and immersed in a water bath. In each tube the experiments are performed at the water bath temperatures of 10, 20 and 30°C above the melting point of the paraffin. Three different initial heights of the PCM inside the tubes are considered, thus bringing the total number of cases explored to thirty six. Each tube is thermally insulated at the bottom, and at its top open to atmosphere, to allow free expansion of the melt liquid. The tubes are transparent, and the melting process is monitored and recorded by a digital camera. The digital pictures of the melting process are analyzed, and the results are graphically presented as melt fraction vs. time, showing the effects of tube diameter, PCM height and temperature difference. Generalization of the results is attempted based on the dimensionless groups, including the Fourier, Stefan, and Rayleigh numbers. A correlation connecting the melt fraction with these dimensionless groups is suggested.
Performance-Based Design Geeration
Authors: Oxman Rivka
Published: July 2009

On the basis of analysis of the current state of the art key concepts and issues in the application of performance-based design in architecture are defined. Future directions for performance-based model that couple principles of evaluation and generation are proposed. Here generative and modifications of a design can be automatically achieved employing processes controlled by analytical and numeric findings. Instead of simulating the performance of a design, and re-design it after analysis and evaluation, it may be possible to directly inform, generate and automatically modify the design using performance-based simulations. The ability to directly manipulate the geometric properties of the digital model is defined and demonstrated.
Classic Plane EHL Problem for Pre-Critical Heavy-Loaded Contacts
Authors: Kudish Ilya I.
Published: July 2009

The paper is aimed at considering the classic plane EHL problem for heavy-loaded contacts lubricated by Newtonian and non-Newtonian fluids. The analytical analysis of the problem is based on matched asymptotic expansions. It is shown that depending on the behavior of the lubricant viscosity there are two distinct lubrication regimes: pre- and over-critical regimes. A specific way for determining which regime occurs for given conditions is proposed. For these two lubrication regimes the relationships of the mechanical mechanisms determining the solution are different and, therefore, the solution structures for the two regimes are different. Asymptotic equations for pressure and gap are derived and solved numerically for pre-critical regimes in the inlet and exit zones. The numerical solutions are stable. Formulas for lubrication film thickness for Newtonian and non-Newtonian fluids for pre- and over-critical regimes are derived based on the asymptotic analysis.
Computer Aided Design of Implant Based Dental Restorations
Authors: Leu Ming C. , Gawate Amit
Published: July 2009

Implant based dental restorations have many advantages over standard removable dentures because using implants can prevent the loss of jawbones, help restore facial features, and enable the patients to get firm bites. A critical step in this kind of restorations is the fabrication of the dental bar on which the denture sits. A dental bar is patient-specific because each patient’s jawbone is unique and the device needs to be conforming to the patient’s gingival surface. The design of a dental bar is crucial to the success of dental restorations. Traditionally, designing a dental bar is a lengthy and laborious process and requires high levels of craftsmanship. There have been attempts to develop CAD/CAM systems towards automating design and fabrication of dental restorations. However, currently available commercial CAD/CAM systems are only capable of making crowns, bridges, copings, onlays and veneers, and they are not capable of making dental restorations involving multiple teeth. The present paper describes a method for computer aided design of a dental bar used in implant based dental restorations. The method starts with a set of digital scan data representing the patient’s gingival surface and generates a CAD model of a dental bar that is ready for fabrication of a physical dental bar.
Digital Manufacturing of Implant Based Dental Restorations
Authors: Leu Ming C. , Delli Parthiban
Published: July 2009

Traditional methods of producing dental bars for overdentures involve tedious and time-consuming operations that demand substantial human labor and demanding skills. Though there exist several CAD/CAM systems that have been developed for various dental restorations like bridges, crowns, etc., there exists no commercial CAD/CAM system at present for design and fabrication of dental restorations for missing multiple teeth. In the research described in the present paper, CAD models of dental bars for implant-retained dental restorations were used as input for three types of fabrication processes: rapid prototyping followed by investment casting, CNC milling, and direct digital manufacturing. Details of material and process combinations and results of comparing these three types of processes, including an analysis on dimensional accuracy, are discussed.
Fatigue Laws via Functional Equations
Authors: Patil Navendu , Mahadevan Pradeep , Chatterjee Anindya
Published: July 2009

In routine industrial design, fatigue life estimation is largely based on S-N curves and ad hoc cycle counting algorithms used with Miner’s rule for predicting life under complex loading. However, there are well known deficiencies of the conventional approach. Of the many cumulative damage rules that have been proposed, Manson’s Double Linear Damage Rule (DLDR) has been the most successful. Here we follow up, through comparisons with experimental data from many sources, on a new approach to empirical fatigue life estimation (‘A Constructive Empirical Theory for Metal Fatigue Under Block Cyclic Loading’, Proceedings of the Royal Society A, in press). The basic modeling approach is first described: it depends on enforcing mathematical consistency between predictions of simple empirical models that include indeterminate functional forms, and published fatigue data from handbooks. This consistency is enforced through setting up and (with luck) solving a functional equation with three independent variables and six unknown functions. The model, after eliminating or identifying various parameters, retains three fitted parameters; for the experimental data available, one of these may be set to zero. On comparison against data from several different sources, with two fitted parameters, we find that our model works about as well as the DLDR and much better than Miner’s rule. We finally discuss some ways in which the model might be used, beyond the scope of the DLDR.
Low Intensity Therapeutic Ultrasound Effect on Nano-Particle Motion in a Viscous Medium
Authors: Mizrahi Natalya , Weihs Daphne , Kimmel Eitan
Published: July 2009

While low intensity therapeutic ultrasound irradiation (LITUS) has been shown to have biological effects on tissue and cells, the physical mechanism leading to those effects has yet to be characterized. As a model system to study effects of LITUS on intracellular organelles, we monitor the dynamics of nanoparticles suspended in a viscoelastic medium, before and during LITUS treatment. Particle motion dynamics can indicate: i) forces acting on similarly-sized intracellular organelles; ii) streaming flow induced in cells and in cavities in contact with cells; and iii) instantaneous (under LITUS) changes in the mechanical properties of viscoelastic media in general and cells in particular. Forces and flow can result in shear stresses that act on the cell membrane of, e.g., endothelial cells in blood vessels and may cause biophysical responses. Particle motion in a high-viscosity, viscoelastic model solution, methyl cellulose, was used as an indicator for sample response under LITUS. The ultrasound-induced motion of nano-particles was quantified by real-time particle-tracking microrheology methods. Particle motion without LITUS irradiation demonstrated diffusive-like behavior with no underlying convection. In contrast, during LITUS irradiation convective motion with a particle-velocity profile parabolic in time was observed. Particles were accelerated after initiation of LITUS irradiation, then a transient phase of constant velocity was observed, and finally the speed was reduced. Altogether the results of the study indicate that LITUS may apply considerable direct forces on suspended particles, a model system for cellular organelles. More studying will help elucidate the mechanisms of LITUS effects. Extending this approach to cells in vitro and evaluating their response can promote the use of ultrasound as a therapeutic tool for delicate manipulation of cells in vivo in a controlled, targeted, and non-invasive way. At the same time, one can define the safety limits and optimal range for therapeutic and diagnostic ultrasound by indicating the threshold for irreversible intracellular changes.
Optimal Electrode Shaping for Precise Modal Electromechanical Filtering
Authors: Elka Arie , Bucher Izhak
Published: July 2009

This paper addresses the optimal shape design of segmented spatial sensors and actuators that excite selected mode shapes and perform modal filtering. In MEMS filters, the input signal is converted to external electrostatic forces and in order to perform the desired filtering, the electrodes need to be shaped such that they excite only a desired part of the dynamics. These electrodes are usually designed according to some simplified theoretical identities, often representing lumped models, where in practice, Micro electromechanical structures dynamics are governed by a three dimensional continuum. An optimization scheme that shapes these electrodes to achieve optimal filtering is developed in this paper. The method provides a trimming methodology that can be performed on a real device and it illustrates the need for suitable modeling. Several simulated examples examine the effectiveness of the proposed optimization methods.