bluuebunny/crossref_metadata_2025 huggingface dataset:
Minimalist Jumping Robots for Celestial Exploration
Authors: Burdick Joel , Fiorini Paolo
Published: August 2003

In this paper we describe a novel approach to the design and deployment of small and minimally actuated jumping or hopping robots that are suitable for exploring the unstructured terrains of celestial bodies. We introduce the basic jumping mobility paradigm, as well as the evolution of our hopping robot concept by way of the main prototypes that we have developed. These prototypes show that a small number of actuators can control the vehicle's steering, hopping, and self-righting motions. The last prototype is equipped with wheels so that precision motion can be combined with gross hopping motion. Lessons learned during the development of these prototypes have general applicability to the design of jumping robots. In addition to reviewing the issues relevant to the design of jumping systems, in this paper we describe some of the key mechanisms that enable our approach, we summarize tests obtained with these systems, and we present our future plans of localization and sensing for hopping mobility.
An Advanced High Modulus (HMG) Short Glass-Fiber Reinforced Nylon 6: Part I - Role and Kinetic of Fiber-Glass Reinforcements
Authors: Kagan Val A. , McPherson Rowena , Chung Jerry S.
Published: August 2003

Recent developments were oriented on two high flow, high modulus fiber-glass reinforced nylon 6 (HMG series) grades for automotive and other industrial applications requiring high stiffness and high strength. These materials combined the following improved technological (injection molding, vibration welding, etc.) and mechanical performance properties such as greater dimensional stability, higher short-term (strength and stiffness) and long-term (fatigue and creep). The current and possible applications of these plastics includes auto mirror housing brackets, clutch pedals, clutch master cylinders, ski bindings, steering wheels, levers, auto seat frames, door handles and door lock mechanisms. In Part I of this paper, we are presenting results of reinforcement analysis with the influence of level of loading and geometrical parameters of used fiber-glass.
An Advanced High Modulus (HMG) Short Glass-Fiber Reinforced Nylon 6: Part II - Mechanical Performance
Authors: Kagan Val A. , McPherson Rowena , Chung Jerry S.
Published: August 2003

Recent developments were oriented on two high flow, high modulus grades fiber-glass reinforced nylon 6 (HMG series) grades for automotive and other industrial applications requiring high stiffness and high strength. These materials combined the following improved technological (injection molding, vibration welding, etc.) and mechanical performance properties such as greater dimensional stability, higher short-term(strength and stiffness) and long-term(fatigue and creep). The current and possible applications of these plastics includes auto mirror housing brackets, clutch pedals, clutch master cylinders, ski bindings, steering wheels, levers, auto seat frames, door handles and door lock mechanisms. In Part I of this paper, we presented results on the role and kinetic of reinforcement with the influence of level of loading and geometrical parameters of used fiber-glass. In Part II of this paper, we are presenting results on short-termand long-term mechanical performance of developed high modulus reinforced plastics.
Chemical Resistance and Tensile Properties of Epoxy/Unsaturated Polyester Blend Coated Bamboo Fibers
Authors: Rajulu A. Varada , Devi L. Ganga , Rao G. Babu , Reddy R. Lakshminarayana
Published: August 2003

The untreated and 2%aqueous NaOH treated bamboo fibers (Dendrocalamus strictus) were coated with epoxy, unsaturated polyester (UP) and their blends. The chemical resistance of these fibers to acetic acid, nitric acid, hydrochloric acid, sodium hydroxide, ammonium hydroxide, sodium carbonate, benzene, toluene, carbon tetrachloride and water was studied. The blend coated fibers showed better resistance to the chemicals mentioned above. The blend coated fibers had higher tensile strength. This was attributed to the hydrogen bonding between the unsaturated polyester and epoxides group.
Bounds on Longitudinal and Transverse Modulus of a Multiphase Composite
Authors: Sharma Rajesh , Ranjan Ashish
Published: August 2003

A bound on longitudinal modulus of a multiphase reinforced composite body is deduced in this paper from “the circle diagram” [Sharma, R. and Ranjan, A. (2000). Elastic Properties of Reinforced Solids: Analogue of Mohr Circle Diagram, Journal of Reinforced Plastics and Composites, 19(14): 1147-1158] when the strain in the composite is not uniform. A circle diagram which describes the transverse property of the composite is also reported here and the corresponding bound on transverse modulus is obtained when the stress in the composite is not uniform. The mixture is assumed to possess the properties described in the literature.
Ultimate Strength and Failure Process of Composite Laminated Plates Subjected to Low-Velocity Impact
Authors: Lee Ya-Jung , Huang Chien-Hua
Published: August 2003

A steel impactor was used in drop tests to impact composite laminated plates constructed using carbon-epoxy prepregs. The impact force and strain histories were recorded as well. Damage incurred from a low-velocity impact much closely resembled that from static crushing. This investigation creates a user-defined material subroutine (UMAT) of the FEM software ABAQUS, using our method of stiffness progressive modification, such that extreme failure is accurately simulated until the plates are thoroughly crushed. Using the results from the static crush simulation and the aspect of energy conservation, the dynamic impact force given with different impactor masses and initial velocities can be rapidly predicted while making significant savings in computing resources.
SEM Observations of the Fractured Surfaces of Coir Composites
Authors: Rout J. , Misra M. , Mohanty A. K. , Nayak S. K. , Tripathy S. S.
Published: August 2003

Coir composites had been prepared using coir fiber (both continuous and short fiber) as reinforcement with both thermosetting and thermoplastics as matrices. The composite specimens were prepared using both untreated and chemically modified such as defatted, PMMA grafted, PAN grafted and cyanoethylated coir fibers. Coir-polyester and glass/coir-polyester hybrid composites were prepared by modified hand-lay-up technique whereas coir-BAK composites were prepared by film-stacking method and coir-PP composites were prepared by compression molding technique. The specimens were subjected to tensile and impact tests and the fractured surfaces were observed under SEM. The SEM micrographs of the fractured surfaces of composites showed varied extents of fiber pull-outs under both failure modes. A good correlation between the SEM study and the mechanical strengths of the composites could be established. The improved mechanical strengths of chemically modified coir composites had been explained on the basis of SEM study.
The Activation to Combustion of a Previously Inert Material By Solvent Imbibition
Authors: Jones J. C.
Published: August 2003

Viton is examined in a microcalorimeter and found to display a nil signal, indicating no heat release. Viton having imbibed an organic solvent mixture releases heat quite powerfully. The results are interpreted along the lines of mutual sensitisation to oxidation of the viton and the solvent.
A Comparative Experimental Study on Heat Release Rates of Charring and Noncharring Solid Combustible Materials
Authors: Chen Changkun , Yao Bin , Fan Weicheng , Liao Guangxuan
Published: August 2003

Two commonly used solid combustible materials in China, PMMA(Polymethyl Methacrylate) and Red Pine of Northeast China, are selected as typical noncharring and charring material respectively. Bench-scale experiments were carried out to measure the heat release rates of these two materials under various external radiant heat fluxes. A comparison of similarity and difference was made between the Heat Release Rate (HRR) of PMMA and that of Red Pine and the influence of external radiant fluxes on HRR was analyzed. Bubble layers and char layers formed near the heated surface of burned noncharring and charring materials, respectively, make them differ greatly in pyrolysis and combustion processes as indicated by different HRR profiles, which are closely related to the material's original structural properties and greatly influenced by external radiant heat flux.
Flame Retardant Cotton Blend Highlofts
Authors: Parikh D. V. , Sachinvala N. D. , Sawhney A. P. S. , Robert K. Q. , Graves E. E. , Calamari T. A. , Chen Y. , Jirsak O.
Published: August 2003

Highloft nonwovens are low density fabrics characterized by a high ratio of thickness to weight per unit area, which means that highlofts contain considerable void volume. They are usually made of synthetic fibers. The present research effort was directed to study cotton blended highlofts. The major problems with using cotton in highlofts are cotton's high flammability and lack of resiliency. The objective of this research was to carry out single-bath chemical finishing of perpendicular-laid (P-laid) highlofts to afford the composites' improved flame resistance (FR) and physical resiliency. We have developed two finishing formulations containing the flame retardants (a) diammonium phosphate (DAP)/urea, and (b) DAP and cyclic phosphonate ester along with the crosslinking agent DMDHEU. Both the formulations imparted flame resistance to the highly flammable highlofts, protecting them completely. However, the formulation containing DAP/urea is preferred because it is of lower cost. Using the vertical flame test, damage sustained was limited to charring in the vicinity of the instigating flame. The crosslinking agent was effective in improving compressional resistance and recovery. So, the finishing treatment produced P-laid cotton blend highlofts that were both FR and resilient.
Clean Room Process Compatibility of Polymeric Materials for the Semiconductor Industry
Authors: Tewarson Archibald
Published: August 2003

A protocol has been developed for the process compatibility of materials for the Semiconductor industry. The process compatibility is assessed by the release of organic compounds, ions, elements, and total oxidizable carbon (TOC) considered undesirable as they damage the wafers and adversely affect their manufacturing yields. The total mass of undesirable organic compounds outgassed per unit surface area of the material under normal operating conditions of the clean rooms is expressed as the outgassing parameter (OP). The total mass of undesirable ions, elements, and TOC leached per unit surface area of the material by ultrapure water (UPW) and ozonated UPW is expressed as the leaching parameter (LP). The total mass of undesirable elements extracted per unit surface area of the material by cleaning solutions of chemicals is expressed as the extraction parameter (EP). The results of the study show that the OP, LP, and EP values of the highly fire resistant materials for the clean rooms of the Semiconductor industry (CPVC, ECTFE, and PVDF) are lower than the values for the ordinary materials (PP, FRPP, and PVC). Ordinary materials have been used in clean rooms for many years without any major problems due to process compatibility and thus the highly fire resistant materials are also process compatible. All these materials are process compatible beacuse low boiling point monomers that are weakly bonded and solvents trapped in the polymer matrix are outgassed. In addition, leaching and extraction occur via weak processes of hydrolysis, breaking of bonds, dissolving and extraction of additives, surface attack by chemicals, and penetration of the material matrix through spaces in the chains.
Release Behavior of Ketoprofen from Chitosan/Alginate Microcapsules
Authors: Tan Tian-Wei , Hu Bo , Jin Xian-Hua , Zhang Mu
Published: August 2003

Chitosan/alginate microcapsules were prepared continuously by an air extrusion method. The influences on loading efficiency and release, such as air flow-rate, chitosan molecular weight and concentration, alginate concentration, pH of chitosan solution, ethyl cellulose, and freezing drying the capsules were studied. Freezing drying chitosan/alginate microcapsules was important for controlled release of ketoprofen. High molecular weight and high concentration of chitosan did not increase loading of ketoprofen, but reduced the release of the ketoprofen. The addition of ethyl cellulose increased the loading of ketoprofen and the release time was prolonged. Increasing sodium alginate concentration reduced the loading efficiency with no clear distinction on the release of ketoprofen. The ketoprofen entrapped in the pH sensitive chitosan/alginate microcapsules gave controlled release in intestinal fluid.
Note: Biological Activity of C6-Oxidized Hyaluronic Acid: Antibacterial Properties of the Zn(II) Salt
Authors: Crescenzi Vittorio , Francescangeli Andrea
Published: August 2003

Partially oxidized hyaluronan sodium and zinc salts and hyaluronan zinc salts were prepared. The antibacterial activity of hyaluronic acid and of C(6)-oxidized hyaluronic acid zinc salts (HAZn+2 and HAOXZn+2) were evaluated against Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli bacterial strains. HAOXZn+2 showed a higher antibacterial effect than HAZn+2 with E. coli and S. aureus; however, neither zinc salt was not able to promote any antiseptic activity against P. aeruginosa.
Perceptions Of Leader Charisma, Effectiveness, And Integrity
Authors: Gardner William L.
Published: August 2003

This study explored the extent to which a leader who claims to be either exemplary or pragmatic and is revealed to have a reputation for either deception or honesty is perceived to be charismatic, effective, and morally worthy. The effects of message delivery and participants’ scores on the Romance of Leadership Scale (RLS) were also examined. The results revealed that (a) a strong versus weak delivery produced higher ratings of leader charisma and effectiveness; (b) exemplary versus pragmatic self-presentations yielded higher levels of perceived effectiveness and integrity; (c) the strong delivery × ethical reputation combination produced the highest levels of perceived leader effectiveness and integrity; and (d) only high RLS individuals perceived the leader to be most effective when delivery was strong and least effective when delivery was weak.
The Communicative Cycle Of Employee Emotional Abuse
Authors: Lutgen-Sandvik Pamela
Published: August 2003

Employee emotional abuse (EEA) is repetitive, targeted, and destructive communication by more powerful members toward less powerful members in the workplace. It is costly, widespread, and may be the precursor to workplace aggression and violence. This article synthesizes extant research findings with the author’s own managerial experience into a comprehensive gestalt of EEA as a communicative process that evolves, escalates, and moves to new targets when earlier targets exit the organization. The model proposed depicts a six-stage cycle that provides a means for (a) understanding the dynamics of abuse, (b) recognizing the indicators of abuse, (c) controlling or stopping the abuse, and (d) predicting the development of unchecked abuse. Practical implications of the model and areas for future research are identified.
Preferences, Rationality and Welfare in Becker's Extended Utility Approach
Authors: Rogeberg Ole
Published: August 2003

The controversial extended utility approach of Gary Becker has been used to argue that even `obvious' irrationalities such as drug addictions are rational behaviour. The present article is a systematic and extensive interpretation of Becker's general approach, introducing a distinction between anticipated time and `objective' time. Using this, I argue that the approach allows us to see even time inconsistency and decisions affected by drug-induced changes in cognition as rational. The philosopher Jon Elster's charges of conceptual incoherence are discussed and shown to rest on a misinterpretation of Becker. The two types of time also have implications for welfare economics and the ways one might try to justify paternalism. Becker's approach becomes difficult to use for welfare economics. Instead, it could be taken to question the wisdom of trying to assess real individuals' welfare through theoretical discussions of rationality.
A Matter of Choice: A Micro-Level Study on how Swedish New Agers Choose their Religious Beliefs and Practices
Authors: Brodin Jenny-Ann
Published: August 2003

A necessary, but surprisingly neglected, postulate within economic and rational choice theories on religious phenomena is that religion is a matter of individual choice. But what does it actually mean to choose religion? Is it a choice similar to other choices - or is it something rather different? In this article individual choices of religious beliefs and practices, both from theoretical and empirical points of view, are discussed. The empirical material consists of ten in-depth interviews within one particular, and also rather special, religious field - namely the Swedish New Age movement. Some of the main findings concern the respondents' strategies to estimate costs/benefits and to reduce different kinds of uncertainty. In the interviews we find an interesting duality. On the one hand there seems to be a highly individualized ideology, stressing individual responsibility and authority; on the other hand social contacts and recommendations seem to be of great importance.
Recent Advances in Optimization of Smart Structures and Actuators
Authors: Frecker Mary I.
Published: August 2003

Much of the recent and past work in the area of smart materials and structures has focused on analysis of actuators and actively controlled systems. Although many sophisticated analysis models have been developed, they are often coupled with ad hoc design methods or informal optimization procedures. A subset of the work done by the smart structures community has focused on development of formal design methodologies and optimization methods specifically for smart actuators and structures. The objective of this paper is to review the current work in development of design methodologies and application of formal optimization methods to the design of smart structures and actuators. In a related paper, optimization strategies for sensor and actuator placement were reviewed by a researcher at NASA Langley in 1999. The current paper reviews the recent work done in this area since 1999, in addition to optimization strategies for topology design of actuators, actively controlled structures, and drive electronics design. The main focus is on piezoelectric ceramic actuators, but relevant work in shape memory alloys and magnetostrictive actuation are included as well. Future directions for research in optimization are also recommended.
Acoustic Measurements Using a Fiber Optic Sensor System
Authors: Yu Miao , Balachandran B.
Published: August 2003

Recent work conducted on developing a fiber tip based Fabry-Perot (FTFP) sensor system for acoustic measurements is presented in this article. It has been determined that this system can be used to detect acoustic fields in the frequency range of 20 Hz-6 kHz with an optical phase sensitivity of 0.095 rad/Pa. A series of experiments is performed to investigate the possibility and potential use of this sensor system, which is designed to be implemented in a multiplexed architecture for providing response measurements to a structural acoustic control system.
Manufactured Configurations of Piezoceramic Disk-Style Actuators
Authors: Hyer Michael W. , Jilani Adel B.
Published: August 2003

The thermally-induced deformations of disk-style actuators that are manufactured flat at an elevated temperature to cure the adhesives and are then cooled to room temperature for use are studied. These particular actuators are designed to deform out of plane as they are cooled. Though the intended deformed shape is dome-like, they sometimes cool to a near-cylindrical configuration. This issue is studied by developing an analysis and then using it to explore the influence of geometry, material properties, and fabrication temperature on whether the cooled configuration is dome-like or near-cylindrical. The analysis is based on using the total potential energy in combination with the Rayleigh-Ritz approach. Geometric nonlinearities are included, and as a result, stability of the cooled configurations is studied.
A Neural Network Inverse Model for a Shape Memory Alloy Wire Actuator
Authors: Song G. , Chaudhry V. , Batur C.
Published: August 2003

Tracking control of shape memory alloy (SMA) actuators is essential in many applications such as vibration controls. Due to the hysteresis, an inherent nonlinear phenomenon associated with SMAs, open-loop control design has proven inadequate for tracking control of these actuators. Aimed at eliminating the position sensor to reduce cost of an SMA actuator system, in this paper, a neural network open loop controller is proposed for tracking control of an SMA actuator. A test stand, including a titanium-nickel (TiNi, or Nitinol) SMA wire actuator, a position sensor, bias springs, and a programmable current amplifier, is used to generate training data and to verify the neural networks open loop controller. A digital data acquisition and real-time control system was used to record experimental data and to implement the control strategy. Based on the training data obtained from the test stand, two neural networks are used to respectively model the forward and inverse hysteresis relations between the applied voltage and the displacement of the SMA wire actuator. To control the SMA actuator without using a position sensor, the neural network inverse model is used as a feedforward controller. The experimental results demonstrate the effectiveness of the neural network open loop controller for tracking control of the SMA wire actuator.
Modeling and Design Optimization of a Bimorph-Driven Rotary Motor
Authors: Frank Jeremy E. , Mockensturm Eric M. , Koopmann Gary H. , Lesieutre George A. , Chen Weiching , Loverich Jacob Y.
Published: August 2003

A bimorph-driven rotary motor has been developed, and demonstrated in a flow-control actuation application. A rotary (roller) clutch rectifies bimorph-powered oscillation into rotational motion to convert electrical to mechanical power. Through a progression of varied designs, the development process was based on experimentation and engineering intuition. The resulting motor satisfied the application requirements, and thirty-two actuators were supplied. To further exploit the possibilities of the bimorph-driven motor concept, a mathematical model was developed. Using empirical data collected from a prototype actuator and a roller clutch, the mathematical model was adjusted so that it predicted the power output of the prototype. The model was then used to tune the design parameters using nonlinear optimization techniques. The results predicted that the power density could be increased by more than 30 times. An improved prototype based on the optimization results demonstrated a significant performance improvement over the original design. Though the predicted improvement was not achieved, the power density was increased by a factor of 10.
Characterization of Novel Flextensional Actuators Designed by Using Topology Optimization Method
Authors: Silva Emílio Carlos Nelli , Nader Gilder , Shirahige Alessandro Barbosa , Adamowski Julio Cezar
Published: August 2003

Flextensional actuators consist of a piezoceramic bonded to a flexible structure that amplifies and changes the direction of generated piezoceramic displacement. In this work, some prototypes of novel flextensional actuators designed by using topology optimization are manufactured, and characterized. Experimental resonance frequencies and displacements of each flextensional actuator and single piezoceramic are obtained by using an impedance analyzer and laser interferometry technique, respectively. The main purpose of these measurements is to verify the displacement amplification introduced by new designs of flextensional piezoelectric actuators. To verify the amplification, both displacements of the single piezoceramic and the complete actuator are measured through laser interferometry and compared. The measurements are made considering harmonic and transient excitations. All experimental results are compared with finite element simulations, using ANSYSTM software. The predicted amplification rates provided by these actuators are verified. Therefore, these results validate flextensional actuators designed by using topology optimization.
Vibration Control of Composite Plates via Optimal Placement of Piezoelectric Patches
Authors: Quek S. T. , Wang S. Y. , Ang K. K.
Published: August 2003

A simple optimal placement strategy of piezoelectric sensor/actuator (S/A) pairs for vibration control of laminated composite plate is presented, where the active damping effect under a classical control framework is maximized using the finite element approach. The classical direct pattern search method is employed to obtain the local optimum, where two optimization performance indices based on modal and system controllability are studied. The start point for the pattern search is selected based on the maxima of integrated normal strains consistent with the size of the collocated piezoelectric patches used. This would maximize the virtual work done by the equivalent actuation forces along the strain field of an initial state. Numerical simulation using a cantilevered and a clamped composite square plate illustrate the effectiveness of the proposed strategy, where the results coincide with the global optimal layout from exhaustive search for both modal and system controllability indices. The number of trials to reach the optimal position is few compared to an initial blind discrete pattern search approach. The reduced control effectiveness of both plates under constrained input voltages is illustrated.
Design and Implementation of a Shape Memory Alloy Actuated Reconfigurable Airfoil
Authors: Strelec Justin K. , Lagoudas Dimitris C. , Khan Mohammad A. , Yen John
Published: August 2003

The unique thermal and mechanical properties exhibited by shape memory alloys (SMAs) present exciting design possibilities in the field of aerospace engineering. When properly trained, SMA wires act as linear actuators by contracting when heated and returning to their original shape when cooled. These SMA wire actuators can be attached to points on the inside of an airfoil, and can be activated to alter the shape of the airfoil. This shape-change can effectively increase the efficiency of a wing in flight at several different flow regimes. To determine the necessary placement of the SMA wire actuators within the wing, a global optimization method that incorporates a coupled structural, thermal, and aerodynamic analysis has been utilized. A genetic algorithm(GA) has been chosen as the optimization tool to efficiently converge to a design solution. The GA used in this case is a hybrid version with global search and optimization capabilities augmented by the simplex method with selective line search as a local search technique. A cost function based on the aerodynamic properties of the airfoil has been used to optimize this design problem to maximize the lift-to-drag ratio for a reconfigured airfoil shape at subsonic flow conditions. A wind tunnel model reconfigurable wing was fabricated based on the design optimization to verify the predicted structural and aerodynamic response. Wind tunnel tests indicated an increase in lift for a given flow velocity and angle of attack by activating the SMA wire actuators. The pressure data taken during the wind tunnel tests followed the trends expected from the numerical pressure results.
Modeling and Optimization of Passively Damped Adaptive Composite Structures
Authors: Thornburgh Robert P. , Chattopadhyay Aditi
Published: August 2003

A smart structural model is used to optimally determine both the placement of piezoelectric actuators and parameters describing associated electrical components in a passively damped structure. The technique utilizes a recently developed coupled piezoelectric-mechanical theory to analytically determine the response of arbitrary structures with piezoelectric materials and attached electrical circuitry. The theory simultaneously models both the structural and the electrical components, and the complex state of strain that may exist in the piezoelectric patches, thereby providing accurate mechanical and electrical response. A robust multiobjective optimization procedure is developed to design the passive system for simultaneous damping of several critical modes of interest. The influence of stacking sequence in augmenting passive damping can also be examined by including ply orientations as design variables. Since the optimization problem now involves both continuous and discrete design variables, a hybrid optimization technique is used that allows the inclusion of both types of design variables. Also, since multiple design objectives are introduced, the Kreisselmeier-Steinhauser function approach is used allowing the multiple and conflicting design objectives and constraints to be combined into a single unconstrained function. Results demonstrate the ability of this technique to determine the optimal tuning parameters for damping of multiple modes of vibration using a limited number of piezoelectric actuators.
Combined Optimization of a Recurve Actuator and its Drive Circuit
Authors: Abdalla Mostafa M. , Song Chunping , Lindner Douglas K. , Gurdal Zafer
Published: August 2003

The integrated modeling and combined optimization of a Recurve actuator and its drive circuit is considered. A finite element model for Euler-Bernoulli beams is developed with appropriate coupling interface to the drive circuit. The finite element model considers appropriate charge variation over the actuator and leads to an energy conservative formulation. The actuator model is coupled to the electric circuit model via a charge-voltage transfer function. The drive circuit is based on a half-bridge switching amplifier topology. Both actuator and circuit physical design variables are considered in the optimization formulation. The objective is to minimize the weight of the system while satisfying performance and stability constraints. The interactions and trade offs between the actuator and the drive circuit are investigated. Optimization results show clear interrelations between the design of the electric circuit and the actuator.
Development of Smart Missile Fins with Active Spoiler
Authors: Kim Seung Jo , Yun Chul Yong , Moon Seong Hwan , Jung Sung Nam
Published: August 2003

For conventional missiles, electric or hydraulic actuators are mounted inside the missile fuselage to activate the aerodynamic control surfaces. These internally mounted actuators occupy considerable volume which otherwise can be used for payload or additional fuel. Reducing the size of the internal actuators and hence lowering the total actuator weight may improve the overall performance of missile significantly. The goal of this research is to develop a light-weight, low cost smart missile fin capable of surviving the supersonic operating environment while providing necessary performance comparable to existing missile fins. In this study, in an alternative to facilitate realistic design concepts and to generate enough actuation forces required for missile controls, smart fins with trailing-edge-mounted retractable wedge are considered. The retractable wedge stretches in or out appropriately to decrease the applied pitching moment of the missile fin. For the theoretical calculation, a commercial CFD software package is used to obtain the forces and the moments generated by the fin with retractable wedge. The piezoelectric actuation mechanism that is applicable to the wedge type actuator is also investigated.
Linear Electromechanical Model of Ionic Polymer Transducers -Part I: Model Development
Authors: Newbury Kenneth M. , Leo Donald J.
Published: August 2003

A linear electromechanical model is developed for ionic polymer materials. The model is based on an equivalent circuit representation that is related to the mechanical, electrical, and electromechanical properties of the material. Expressions for the quasi-static and dynamic mechanical impedance are derived from beam theory. The Golla-Hughes-McTavish model of viscoelasticity is incorporated into the model to include effects due to a rate dependent modulus. Similar to previous research, the electrical impedance is modeled as a series combination of resistive and capacitive elements. The major contribution of this work is the derivation of an electromechanical coupling term that is related to an effective bending strain coefficient. This parameter is also frequency dependent to model the low-frequency relaxation that has been measured in certain ionic polymer materials. The resulting linear electromechanical model is based on the measurement of the effective permittivity, elastic modulus, and effective strain coefficient. All input-output relationships related to sensing and actuation can be derived using these three material parameters and the transducer geometry. This model also emphasizes a reciprocity between sensing and actuation that has not been discussed before in relation to these materials. The result of this work is a comprehensive model that enables the design of devices and material systems that incorporate ionic polymer materials as either sensors or actuators.
Linear Electromechanical Model of Ionic Polymer Transducers -Part II: Experimental Validation
Authors: Newbury Kenneth M. , Leo Donald J.
Published: August 2003

A series of experiments are performed to assess the validity of an equivalent circuit model of ionic polymer transducers. The fundamental parameters of the model are the dielectric permittivity of the material, the viscoelastic modulus, and the effective strain coefficient of the transducer. The results demonstrate the validity of a simplifying assumption regarding the reflected impedance of the polymer. This allows us to use a simpler set of expressions to predict the time and frequency response of the polymer. The expressions for sensing and actuation are verified in a series of step response and frequency response tests of cantilevered transducers. The curvefit algorithm used for parameter identification works well but there is always a tradeoff in accuracy between the time domain and frequency domain measurements. This could imply the existence of an input-level dependence on the parameters. In spite of this level dependence, the linear model is able to predict the response of an input-output pair that is independent of the parameter identification. This result supports the validity of the linear model. Experimental results also support the use of a reciprocal model in which each expression for actuation has a dual expression for sensing. Scaling experiments verify the predictions of the model with respect to changes in transducer length and width.
A Domain Wall Model for Hysteresis in Ferroelastic Materials
Authors: Massad Jordan E. , Smith Ralph C.
Published: August 2003

We develop a model that quantifies constitutive nonlinearities and hysteresis inherent to ferroelastic compounds, with emphasis placed on shape memory alloys. We formulate the model in two steps. First, we use the Landau theory of phase transitions to characterize the effective Gibbs free energy for single-crystal and polycrystalline ferroelastics. The resulting nonlinear equations model equilibrium material behavior in the absence of impurities. Second, we incorporate pinning losses to account for the energy required to move domain walls across material inclusions. The full model is analogous to those developed by Jiles and Atherton for ferromagnetic compounds and Smith and Hom for ferroelectric materials. We illustrate aspects of the model through numerical simulations and comparisons with experimental stress-strain data.
Control of Wave Propagation in Sandwich Beams with Auxetic Core
Authors: Ruzzene Massimo , Scarpa Fabrizio
Published: August 2003

The wave propagation in sandwich beams with cellular core is analyzed and controlled. The material properties of cellular cores are highly dependent on the geometry of the cell composing the honeycomb structure. Core materials of different geometry placed periodically along the beam length introduce the proper impedance mismatch necessary to impede the propagation of waves along the beam. A theoretical model is developed to describe the wave propagation characteristics and the vibration of the sandwich beam. The model is used to obtain the transfer matrix for a unit cell of the considered periodic structure, which is then used to analyze the dynamics of wave propagation along the beam. The transfer matrix is also properly recast in order to obtain the dynamic stiffness matrix and formulate a spectral finite element model for the periodic sandwich beam. The spectral finite element model employs dynamic shape functions obtained from the solution of the distributed parameter model, which allow predicting the dynamic behavior of the structure with a significantly reduced number of elements as compared to conventional FEM. The transfer matrix of the sandwich beam identifies the location of the frequency bands where traveling waves are attenuated. The influence of core geometry and periodicity on the location and extension of these stop bands is assessed through a series of simulations. The effect of the periodicity of the structure is also evaluated by considering the vibration response of a clamped free beam excited by the harmonic motion of the base. The results demonstrate the simplicity and the effectiveness of the proposed treatment whereby the transmission of waves and the vibration over specified frequency bands can be significantly reduced without requiring additional passive or active control devices. The unique characteristics of cellular solids therefore can be used to design light-weight composite panels that behave as mechanical filters. The filtering capabilities of such passive composite panels may be easily changed and optimized to reduce their transmissibility over a desired frequency range without compromising the size and the weight of the structure.
Efficient Process Optimization
Authors: Whitfield R. I. , Duffy A. H. B. , Coates G. , Hills W.
Published: August 2003

A computer-based system for modelling and optimizing processes is presented. The Design Structure Matrix (DSM) process representation was used to model the processes due to its compact, generic and easily quantifiable nature. The system is capable of calculating a number of process performance metrics that are focussed towards determining the degree of iteration and concurrency within the process, however, the system is easily extendible to include other process performance measurements. The paper describes the use of a Genetic Algorithm (GA) to optimise the sequence of activities with the focus of reducing the amount of iteration by reducing the number of feedback loops and hence reducing the number of initial guesses that are needed in order to undertake highly dependent tasks. Previous investigations have attempted to define a generic structure for combinatorial optimisation using GAs [Todd, D. (1997). Multiple Criteria Genetic Algorithms in Engineering Design and Operation, Ph.D. Thesis, Engineering Design Centre, University of Newcastle upon Tyne, UK.],however this paper demonstrates that the structure of the GA is intrinsically tied to the domain. The focus of this paper was an investigation to determine the most efficient and timely structure for the GA with respect to process optimisation. Additional criteria are included within the system and it is has been demonstrated that the structure is applicable for these criteria. It is therefore assumed that if the criteria are dependent upon the matrix representation, in particular, the sequence of the activities and dependencies, then the GA structure will remain applicable. This assumption was demonstrated to be correct when the DSM and GA were used with the same GA structure to optimise component modularity using different optimisation criteria [Whitfield R.I., Smith J.S. and Duffy A.H.B. (2002). Identifying Component Modules, Seventh International Conference on Artificial Intelligence in Design AID'02, Cambridge, UK,15-17 July 2002.]. The results indicated that the independent position based crossover and shift mutation operators with 60 and 20% probabilities respectively was the most successful structure for the GA. A relationship between the number of activities and the number of evaluations was determined and may be used to eliminate unnecessary computation in future investigations.
A Comparison of Data Models in Chemical Engineering
Authors: Bayer B. , Marquardt W.
Published: August 2003

Several data models have been developed in the domain of chemical engineering as the basis of specialized computer-aided tools, for the exchange of data between different tools, or to obtain a better understanding of the domain in order to improve its work processes and to provide specific support functionalities. All these data models where developed independently from each other and for specific applications. Within this paper, a comparison of different chemical engineering data models, that are currently developed and used, is attempted. First some fundamentals of data modeling will be presented. General requirements of data models are given as well as requirements that are specific to chemical engineering. These requirements and the covered data scope build the basis for the discussion and comparison of the data models. Based on this analysis, open issues in data modeling are derived that need to be approached in order to obtain high quality data models as a basis for information management and support of concurrent engineering.
Internet-Based Design Visualization for Layered Manufacturing
Authors: Jee Haeseong J. , Campbell R. Ian
Published: August 2003

When considering the use of layered manufacturing (LM), there are many issues a designer has to address for handling a stereolithography tessellation language (STL) model, the de facto standard for LM. In this paper, we propose an Internet-based design visualization tool for decision support when optimizing the LM process in support of a highly interactive and collaborative virtual environment between CAD designers and LM processes over networks. It directly provides designers with an advanced preprocessor functionality, design visualization/optimization, as well as model display, repair, and slicing over the network. This can help smooth data transfer from CAD to the LM process with minimum inconsistency in CAD data.
Distributed Design Support System for Concurrent Process of Preliminary Aircraft Design
Authors: Fujita Kikuo , Kikuchi Shin'ichi
Published: August 2003

This paper proposes a framework for developing a distributed design support system for concurrent design process and applies it experimentally to preliminary aircraft design. The design process of a large complicated system is characterized by compromising between various criteria and relationships among quasi-independently decomposed subproblems. The preliminary design of aircraft is typical of such a design problem. In this paper, after the design problem is defined as a lumped mass system, the types of design phases, knowledge and operations are formally defined. The design process is decomposed horizontally and vertically, and the coordination mechanism is categorized into inter, inner and global aspects. Based on these, a computational method for supporting design refinement is developed using mathematical programming techniques. Furthermore, an experimental computer-aided design system is implemented for the preliminary design of aircraft using knowledge-base system techniques and agent-based distribution of tasks, etc. Its application demonstrates the validity and promises of proposed models and procedures.
Structural Changes During Air Drying of Fruits and Vegetables
Authors: Ramos I. N. , Brandão T. R.S. , Silva C. L.M.
Published: August 2003

This work aims at reviewing structural changes occurring in convective air drying of fruits and vegetables. These include changes in physical properties, such as volume, porosity and bulk and particle density, which directlyaffect textural attributes of the products. Models relating with water content physical properties are also summarised. At microscopic level, the phenomena observed byprevious authors is described, focusing on shrinkage. In particular, a new approach on modelling kinetics of microstructural modifications is presented. Although the air drying process is relatively well studied, there is a lack of research concerning changes in structural properties. Modelling mass transfer during drying frequently does not include those effects and, there has not been established a standard methodologyfor predictive purposes. Correlating microstructure, texture measurements and sensoryanalysis would be an attractive area to be exploited for drying processes of fruits and vegetables. Although this is a wide working field, much is still to be done.
Drying and Dried Products Under the Microscope
Authors: Aguilera J. M.
Published: August 2003

Food engineers do not often realise that drying of foods and biological materials is a problem of preserving or transforming structures rather than one of removing water. Some unique product properties depend on the structure of dried foods: rehydration and instant properties, flavour retention and sensorial attributes (including colour and texture). The role of structure extends in biochemical and pharmaceutical products to the molecular level and plays key role in viability of desiccated plants and organisms and/or specific activity of dried biomolecules. Nowadays different techniques and probes are available to visualise changes in structure down to the nanostructural level, acquire physicochemical data of micron-size regions and perform physical/mechanical testing in situ. Most novel visualisation methods are non-intrusive permitting image and data acquisition in real time under simulated or current drying conditions. An emerging field of work is that of quantification of structural features using advanced image processing techniques and fractal analysis. Meaningful structure-properties relationships of dried foods can then be derived from their analysis that might contribute to the design of new and specific structures to improve food functionality. Combination of the microstructural approach and concepts from food materials science should result in major advances in this important unit operation and in tailoring product properties.
Status and Needs in Drying Technology for the Food and Pharmaceutical Industry
Authors: Lillford P. J.
Published: August 2003

Drying is an important process technology for both the food and pharmaceutical industries. However, despite their common interest in processing and their usage of biological and organic materials there have been little overlap or exchange of ideas and methods. This paper probes the significance and requirements of drying in each industry and identifies divergent and convergent interests. Areas of relative strength and weaknesses in the applied science of each industry is presented, together with some issues of current or future synergy and mutual benefit. An overview of the current state of knowledge in foods is presented, together with suggestions for borrowing or co-developing materials science and measurement techniques from each of the industries.