bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact Monitoring of Smart Composite Laminates Using Neural Network and Wavelet Analysis
Authors: Sung Dae-Un , Oh Jung-Hoon , Kim Chun-Gon , Hong Chang-Sun
Published: August 2002

Low-velocity impact damage is a major concern in the design of structures made of advanced laminated composites, because such damage is mostly hidden inside the laminates and cannot be detected by visual inspection. It is necessary to develop the impact monitoring techniques providing on-line diagnostics of smart composite structures susceptible to impacts. In this paper, we discuss the process for impact location detection in which the generated acoustic signals are detected by PZT using the improved neural network paradigms. To improve the accuracy and reliability of a neural network based impact identification method, the Levenberg-Marquardt algorithm and the generalization methods were applied. This study concentrates not only on the determination of the location of impacts from sensor data, but also the implementation of time-frequency analysis such as the Wavelet Transform (WT) to measure the characteristic frequencies of acoustic emission waves for the determination of the occurrence and the estimation of impact damage.
Driving Rain Course Simulation Based on Daily Data
Authors: KoronthÁlyovÁ Ol'ga , MatiaŠovskyý Peter
Published: August 2002

Numerical models of the Heat-Air-Moisture (HAM) transfer need the hourly values of climatic elements including the driving rain loads. This paper presents a method of creating the hourly data of the driving rain loads on an exposedwall applicable as a boundary condition forHAMnumerical calculations. It is suitable in case the real hourly values of the driving rain are not available. The method uses the measured daily characteristics of climatic elements—the daily amounts of the horizontal rainfall and the daily means of the wind speed. Results of the numerical simulation of hygrothermal performance of a wall that use the approximated daily courses of the driving rain are in satisfactory agreement with the results that use the real measured hourly data independently of the consideredwall material.
Moisture Sorption Effects on Carbon Fiber-Reinforced Pheny L Ethnyl-Terminated UltemTM Composites
Authors: Bullions T. A. , Jungk J. M. , Loos A. C. , Mcgrath J. E.
Published: August 2002

High-performance aerospace applications require materials that are able to withstand exposure to extreme temperatures, high relative humidities, solvents, and other chemicals. Due to their high-performance thermal and mechanical characteristics, poly(etherimide)s are being implemented in such applications. Prior to such use, environmental effects on material performance must be understood. In this study, the effects of moisture sorption on the mechanical properties of carbon-fiber-reinforced phenylethynyl-terminated poly(etherimide) matrix composites were investigated. The through-the-thickness moisture diffusion coefficient and the maximum moisture equilibrium content were determined for the unidirectional composites for exposure to 90'C and 85% relative humidity. In addition, the composites were tested for retention of transverse flexural strength and apparent interlaminar shear strength at maximum moisture equilibrium content. The same properties were tested for property retention following desorption of moisture to a 90'C, 2% relative humidity moisture content. The composite showed high mechanical property retention with recoverable matrix plasticization being the source of property reductions.
A Comparative Evaluation of Coefficient of Friction and Mechanical Properties of Commercially Available Foley Catheters
Authors: Ramesh P. , Joseph R. , Sunny M. C.
Published: August 2002

Three commercially available urinary catheters were evaluated for their coefficient of friction and mechanical properties, which are two important parameters as far as the intended use is considered. The apparent coefficient of friction was measured from the slope of the force versus normal load graph using an in-house fabricated setup. Themechanical properties like ultimate tensile strength, elongation at break and modulus were evaluated before and after aging in synthetic urine. The swelling behavior of the catheter samples was studied in toluene and found to correlate well with the mechanical properties.
Applications of Instructional Design Mapping Strategies in the Development of Complex Integrated Courses
Authors: Kerr Robert A.
Published: August 2002

Courses that attempt to integrate information from multiple disciplines are often difficult to design and implement. Such courses may tend to become an unorganized conglomerate of content that satisfies the needs of discipline specific faculty rather than the learning needs of students. By using a course mapping strategy that is grounded in instructional systems design theory, faculty from different disciplines can work together to design complex courses that facilitate successful learning and accomplishment of pre-determined curricular outcomes. This article will present an approach to course mapping and examples of its application to several integrated courses developed by faculty at the University of Maryland School of Pharmacy.
Eigenstrain Techniques for Modeling Adaptive Structures: II. Active Damping
Authors: Alghamdi Abdulmalik A. A. , Dasgupta Abhijit
Published: August 2002

This is the second paper, in a two-part series, that demonstrates the utility of Eshelby’s eigenstrain techniques for modeling adaptive structures. The first paper addressed adaptive stiffening (Alghamdi and Dasgupta, 2000). The objective of this second paper is to model adaptive damping. Distributions of small active piezoceramic devices embedded in the adaptive structure are treated as elastic heterogeneous inclusions. Sensors are treated as elastic heterogeneities subjected to external loads, whereas actuators are modeled as elastic heterogeneities subjected to both external loads and internal induced strains caused by the converse piezoelectric effect. The coupled electromechanical boundary value problem is solved using a generalized form of Hamilton’s principle where the energy functional is evaluated using the eigenstrain method. System dynamic equations are developed for active damping and a numerical solution to the variational problem is obtained by using the Raleigh-Ritz approach. Numerical results are verified experimentally using a cantilever beam with distributions of embedded piezoelectric (PZT-5H) mini-devices. A significant amount of damping is achieved for low volume fraction of devices and good agreement is obtained between numerical and experimental results. The eigenstrain technique is demonstrated to be a capable three-dimensional tool for modeling adaptive structures with embedded distributions of mini-devices.
Flow Analysis of Field-Controllable, Electro- and Magneto-Rheological Fluids Using Herschel-Bulkley Model
Authors: Wang Xiaojie , Gordaninejad Faramarz
Published: August 2002

The Bingham plastic constitutive model has been widely used to predict the post-yield behavior of electro- and magneto-rheological fluids (ER and MR fluids). However, if these fluids experience shear thinning or shear thickening, the Bingham plastic model may not be an accurate predictor of behavior, since the post-yield plastic viscosity is assumed to be constant. In a recent study, it was theoretically and experimentally demonstrated that the Herschel-Bulkley fluid model can be successfully employed when evaluating non-Newtonian post-yield behavior of ER and MR fluids. In this paper, we extend our previous work and adopt the Herschel-Bulkley model to include a detailed analysis of ER and MR fluid dynamics through pipes and parallel plates. Simplified explicit expressions for the exact formulation are also developed. It is shown that the proposed simplified model of the Herschel-Bulkley steady flow equations for pipes and parallel plates can be used as an accurate design tool while providing a convenient and generalized mathematical form for modeling ER and MR fluids. Theoretical and experimental analyses are presented for a MR fluid damper, which is designed, developed, and tested at the University of Nevada, Reno (UNR).
Hydrophilic Polymers Derived from Vitamin E
Authors: Vazquez B. , Ortíz C. , Román J. San , Plasencia M. A. , López-Bravo A.
Published: August 2002

Vitamin E containing copolymers for biomedical applications was obtained by copolymerization reaction of vitamin E methacrylate (VEMA) with 2-hydroxyethyl methacrylate (HEMA), N,N-dimethyl acrylamide (DMA) or vinyl pyrrolidone (VP), in different experiments. High molecular weight copolymers prepared by free radical reactions initiated by azobisisobutironitrilo, AIBN, present a random distribution of vitamin E derivatives along the macromolecular chains, and the average composition depends on the initial composition of the reaction medium. The relative flexibility of the polymeric systems was analyzed measuring the glass transition temperature of copolymeric sequences and that of the pure alternating diad ( T g12) obtained by the application of the treatments proposed by Johnston and Barton to all the systems. T g12 was higher than the average T g of both homopolymers ( T g) for the VEMA-HEMA system, T g12 was lower than T g for the VEMA-DMA system and T g12 was similar to T g for the VEMA-VP system. VEMA-HEMA copolymers gave rise to hydrogels in water, acidic and alkaline media. VEMA-DMA copolymers gave rise to hydrogels in acidic medium and dissolved in water and alkaline medium. VEMA-VP copolymers were soluble in all media. The swelling of all the hydrogels fit a second order kinetics. A VEMA-HEMA hydrogel was selected for in vivo experiments in order to study the influence of vitamin E on the regeneration process of Achilles tendon. The polymeric derivatives of vitamin E stimulated the regenerative process as a consequence of the antiaging effect in the local area of application.
Network Structure and Properties of Dimethacrylate-Styrene Matrix Materials
Authors: Li H. , Burts E. , Bears K. , Ji Q. , Lesko J. J. , Dillard D. A. , Riffle J. S. , Puckett P. M.
Published: August 2002

One of the major classes of polymer matrix resins under consideration for structural composite applications in the infrastructure and construction industries is theso-called "vinyl esters." These are comprised of low molecular weight poly (hydroxyether) oligomers with methacrylate endgroups diluted with styrene monomer. The methacrylate oligomeric endgroups co-cure with the styrene in free radical copolymerization to yield thermoset networks. Selected properties of such resins and resultant networks where the molecular weights of the poly(hydroxyether) oligomers have been varied from 700 to 1200 g/mole and the concentration of styrene has been systematically changed are presented. In general, both the glass transition temperatures and fracture toughness of the fully cured networks increased as the styrene was decreased in each oligomer series with different molecular weights. As expected, the volume contraction upon cure also decreased significantly as styrene was decreased, and thus residual cure stresses may be reduced in fiber reinforced composites. The resistance to crack propagation was significantly improved for networks prepared with the 1200 Mndimethacrylate oligomer relative to those from the 700 g/mole material. Crosslink densities were estimated from measurements of the rubbery moduli at Tg+ 40°C and relationships between network density, chemical composition and properties are discussed.
Health Monitoring and Diagnosis for Flexible Structures with PVDF Piezoelectric Film Sensor Array
Authors: Wang D. H. , Huang S. L.
Published: August 2002

How to access the health situation of civil infrastructures is a brand-new challenge that scientists and civil engineers faced up to. Therefore, the method of health monitoring and diagnosis for flexible structures is a very active area of both academic and industrial research and development. For the large flexible structures, the mini cracks, which are the premise to induce the large cracks and damages in the structures, exert a little influence on the resonant frequencies of the structures. So the health monitoring method based on the changes of the resonant frequencies need that the cracks are so large that it can influence the resonant frequencies. However the mini cracks would change the vibration amplitude determined through monitoring the strain near the cracks, which can be used as the information sources realizing the health monitoring and diagnosis. It is a pity that the random external disturbances would influence the vibration amplitude, which can influence the effectiveness of the method that based on the vibration amplitude, so the key problem using the health monitoring and diagnosis method based on the vibration amplitude is how to avoid the influence of the random external disturbance. In this paper, a health monitoring and diagnosis method for flexible structures, which based on the relative outputs between sensors among PVDF piezoelectric film sensor array, is put forward. A Functional Link Neural Network (FLNN) is used as the damage modes classification unit. The experimental results show that the health monitoring method proposed in this paper is effective for diagnosing the damage and its severity, although the damage modes are not too complicated. Because the FLNN realizes the classification through enhancing the input patterns, the architecture of the neural network used in this paper is simple, the learning algorithm is easy, and the learning speed is fast. During the training and validation of the FLNN, its input patterns are formed by the relative outputs between the PVDF piezoelectric film sensors, which are affixed on the surface of flexible structures and formed into the sensor array. So the external exciting amplitude is not needed to be fixed or to be confined to a fixed variation range for the health diagnosis, which is validated by the experiment on the flexible beams and guarantees the method proposed in this paper to be suitable for a general usage.
Pharmacological fMRI: A New Tool for Drug Development in Humans
Authors: Tracey Irene , Wise Richard G.
Published: August 2002

Until now, our understanding of human brain pharmacology has depended on indirect assessments or animal models. The advent of pharmacological functional magnetic resonance imaging (phMRI) has enabled researchers to focus directly on human pharmacology and brain function.

Functional MRI, with its increased spatial and temporal resolution, has a further advantage over other neuroimaging methods in that being totally noninvasive, it allows serial, longitudinal studies to be performed on the same subject. This opens the door to a new era of phMRI, as the effects of drugs can be readily monitored in one subject (control or patient) over time. In addition, sophisticated paradigms can be developed that can isolate specific brain regions of activation. These regions can then be subsequently targeted and challenged with appropriate drugs. This allows for a “battery” of paradigms aimed at determining a drug’s mechanism and site of action, which would be valuable for drug development and discovery.
Elastic-Plastic Stress Analysis and Residual Stresses in a Woven Steel Fiber Reinforced Thermoplastic Composite Cantilever Beam Loaded Uniformly
Authors: Sayman Onur , Zor Mehmet
Published: August 2002

In this study an elastic-plastic stress analysis is carried out in a woven steel fiber reinforced thermoplastic (LDFE, F.2.12) composite cantilever beam loaded uniformly at the upper surface. The intensity of the uniform force is chosen as a small value; therefore the normal stress component of ay is neglected during the elastic-plastic solution. An analytical solution is found, satisfying both equations of equilibrium and boundary conditions for a plane stress case. The orientation angle of the fibers is chosen as 00, 150, 300 and 45. The intensity of the residual stress component of ox is maximum at the upper or lower surfaces of the beam. Yielding begins earlier at the upper surface of the beam for 150 and 300 orientation angles. The intensity of the residual stress component of the shear stress is maximum on or around the longitudinal axis of the beam.
Determination of Fumonisins B1 and B2 Produced by Isolates of Gibberella fujikuroi Complex in Corn and Rice
Authors: Mateo J. J. , Mateo R. , Jiménez M.
Published: August 2002

Fumonisins B1 (FB 1) and B2 (FB2) are the major mycotoxins produced mainly by some strains of Gibberella fujikuroi complex, fungi that occur worldwide on cereals. Contamination of food and feed with these fungi has been associated with a number of diseases in animals and humans. In this work, some steps in the analysis of FB 1 and FB 2 by HPLC to reduce analysis time, costs and impurities in the extracts are evaluated. Fumonisins were extracted with acetonitrile/water (1:1), and the extract was cleaned up by solid-phase extraction through C 18 cartridges. These cartridges have the advantage over SAX cartridges of being less time-consuming and producing cleaner extracts. The fumonisins were eluted from the cartridge with methanol/water (7:3) and derivatized with ophthaldialdehyde and 2-mercaptoethanol to yield highly fluorescent derivatives. Reversed-phase HPLC with fluorescence detection is used for the final separation and determination. Under these conditions, the analytical method proved to be linear for mycotoxin amounts in the range from 10–4000 ng. The detection limits in corn and rice samples (at a signal-to-noise ratio of 3:1) were 5 ng/g for both fumonisins.
Damping Effect of Multi-Layer Beams with Embedded Electro-Rheological Fluid
Authors: Qiu Jinhao , Tani Junji , Hajika Tomoaki
Published: August 2002

The damping effect of multi-layered composite beams with embedded ER fluid layers is investigated. A three-layer beam was composed of the aluminum layers bonded together by silicone rubber with an internal cavity filled with ER fluid. The damping factor of the beam can be controlled by the voltage between the elastic layers. To increase the damping effect, an inner layer was inserted into the cavity so that the composite beam consists of three elastic layers and two ER fluid layers. The frequency characteristics of the three-layer beam and the five-layer beam were investigated experimentally and numerically. The results show that the damping factor of the composite beams can be considerably raised by increasing the electric field. The natural frequency of the beams increases with the field due to the variation of stiffness of the ER fluid layers. The influence of size of inner layer on the damping effect of the five-layer beam was also investigated. It is shown that the damping factor of a five-layer beam could be larger than that of a three-layer beam if the size of the inner beam is appropriately designed.
“Microflex”—A New Assembling Technique for Interconnects
Authors: Stieglitz Thomas , Beutel Hansjoerg , Meyer J. -Uwe
Published: August 2002

A new interconnection technique has been developed that allows versatile multiple strand connections between microsensors, sensor arrays, and chips designed for wire bonding. The new technique has been termed “Microflex interconnection” technique (MFI).

Conventional wire bonding technique is commonly restricted to planar interconnects with a limited degree of freedom for placing microsystem components in hybrid assemblies. The MFI technique has overcome this limitation by interconnecting microsystem components through custom designed flexible substrates with embedded metallized conductors, pad arrays for integrated circuits’ assembly and substrate integrated electrodes. Standard CMOS components without additional pad metallization can be used. The integration density of the MFI technique corresponds to one of the flip-chip technology. Special advantages of the MFI technique are three-dimensional interconnects, the flexibility in design and shape, and easy visual inspection of alignment qualities. The method is especially suitable for small volumes of customer specified devices and biomedical implants because all materials used are biocompatible.

Within this paper, the MFI technique is introduced, described in detail, and tested according to international standards. The evaluation of the electrical and mechanical properties of the interconnection sites exhibited promising results regarding stability and reliability. First applications in the biomedical field were presented on the example of a neural implant and a sensorized cardiac catheter.
Effective Thermo-Elastic Constants Angle-Ply Laminates Containing 90 Degree Ply Cracks
Authors: Whitney James M.
Published: August 2002

Effective elastic moduli and thermal expansion coefficients for a composite containing transverse cracks through the middle layers are determined analytically. The laminate portion of the layered composite is treated as a single plate with effective properties (global laminate model), and the ply clusters are modeled as a homogeneous, orthotropic material (local model). The global model is a displacement based, higher order laminated plate theory, while the local model is a stress based homogeneous plate theory. Both models include the effect of transverse shear and normal stresses. This global/local scheme leads to considerable flexibility in modeling cracked laminates without resorting to an inordinate number of degrees of freedom. Numerical results are compared to other approaches.
Effect of Vinyl and Silicon Monomers on Mechanical and Degradation Properties of Bio-Degradable Jute-Biopol® Composite
Authors: Khan M. A. , Kopp C. , Hinrichsen G.
Published: August 2002

Composites of jute fabrics (Hessian cloth) and Biopol® were prepared by compression molding process. Three types of Biopol® (3-hydroxbutyrate- co-3-hydroxyvalarate) such as D300G, D400G and D600G, depending on the concentration of 3-hydroxyvalarate (3HV) in 3-hydroxbutyrate (3HB) were taken for this purpose. Mechanical properties such as tensile strength (TS), bending strength (BS), elongation at break (Eb) and impact strength (IS) of the jute-Biopol® composites were studied. It was found that the composite with D400G produced higher mechanical properties in comparison to the other two types of Biopol®. To increase mechanical properties as well as interfacial adhesion between fiber and matrix, 2-ethyl hydroxy acrylate (EHA), vinyl tri-methoxy silane (VMS) and 3-methacryloxypropyl tri-methoxy silane (MPS) were taken as coupling agents. Enhanced mechanical properties of the composites were obtained by using these coupling agents. Biopol® D400G composites showed the highest mechanical properties. Among the coupling agents EHA depicts the highest increase of mechanical properties such as tensile strength (80%), bending strength (81%), elongation at break (33%) and impact strength (130%) compared pure Biopol. SEM investigations demonstrate that the coupling agents improve the interfacial adhesion between fiber and matrix. The surface of the silanized jute was characterized by FTIR and found the deposition of silane on jute fiber was observed. Soil degradation test proved that the composite prepared with EHA treated jute exhibits better degradation properties in comparison to pure Biopol®.
Detection of Buckling and Crack Growth in the Delaminated Composites Using Fiber Optic Sensor
Authors: Park Joong-Wan , Ryu Chi-Young , Kang Hyun-Kyu , Hong Chang-Sun
Published: August 2002

To estimate the overall performance of composites, it is necessary to identify the influence of the buckling and delamination failure. For that reason, a fiber optic sensor was applied to the delaminated composite beams to detect the buckling occurrence and delamination growth. The delaminated composite beams subjected to the compressive load were tested to identify the signal characteristics of the fiber optic sensor. The signals of the fiber optic sensor from buckling or delamination growth were quantitatively evaluated by short time Fourier transform and wavelet transform.
Mindlin-Type Finite Elements for Piezoelectric Sandwich Plates
Authors: Bisegna Paolo , Caruso Giovanni
Published: August 2002

New finite-element formulations are developed for the analysis of a plate having thin piezoelectric actuators bonded on its upper and/or lower surfaces. The proposed finite elements are two-dimensional, quadrangular, four-node, Mindlin-type, locking-free, and have five degrees of freedom per node. These are the deflection of the middle plane of the plate, the rotations of the fibers normal to the middle plane and the actuation electric potentials of the piezoelectric actuators. The effectiveness of the proposed finite-element formulations is shown by studying some case problems, whose analytical solutions are available.
In-Plane Impedance Spectroscopy of Doped Polyaniline Films
Authors: Ou Runqing , Samuels Robert , Gerhardt Rosario A.
Published: August 2002

In-plane impedance measurements were made on lightly doped polyaniline (PANI) films. A Debye-like conductivity relaxation was observed for HCl-doped PANI samples. The relaxation shifts to higher frequency as the doping level is increased. The conductivity shows a dramatic increase at low doping levels and levels off at higher doping levels. The in-plane conductivity is over three orders of magnitude higher than the through-plane conductivity.
Seismic Response of Civil Structures Utilizing Semi-Active MR and ER Bracing Systems
Authors: Hiemenz Gregory J. , Wereley Norman M.
Published: August 2002

Magnetorheological (MR) and electrorheological (ER) dampers are a promising class of semi-active devices for the control of civil engineering structures for earthquake hazard mitigation. ER and MR dampers exhibit both viscous damping and friction damping, where the friction damping level is controlled by an applied electric or magnetic field, respectively. These unique characteristics lend them to be very suitable devices for the semi-active control of such seismically loaded structures. Inspection of the equation of motion for such a system yields a non-dimensional variable, 3, which is the ratio of the yield force of the damper to the forcing input (the product of a characteristic mass of the building and the seismic acceleration). It is shown that maintaining D < I prevents a damper lockup condition that will stiffen the structure. This stiffening may cause the structural response spectrum to coalesce with the earthquake spectrum, and worsen the seismic response. D is also useful because it can be used to scale a damper to a structure for a desired response reduction, and it can be used as a non-dimensional control parameter. It is also shown that for lightly viscous damped structures (like most civil structures), the response reduction is approximately linear with P. Numerical analyses are performed on a three-story model structure for different damper locations. It is shown that placing dampers near the base of the structure, as opposed to the upper levels, yields better frequency response reduction. Lastly, it is shown that passively controlling structures undergoing seismic accelerations with constant field applied to the damper greatly reduces the seismic response.
State-Switched Absorber for Semi-Active Structural Control
Authors: Cunefare Kenneth A. , de Rosa Sergio , Sadegh Nader , Larson Gregg
Published: August 2002

A system that has the capability to make instantaneous changes in its mass, stiffness, or damping may be termed a state-switchable dynamical system. Such a system will display different dynamical responses dependent upon its current state. For example, state-switchable stiffness may be practically obtained through the control of the termination impedance of piezoelectric stiffness elements. If such a switchable stiffness element is incorporated as part of the spring element of a vibration absorber, the change in stiffness causes a change in the resonance frequencies of the system, thereby instantaneously “retuning” the state-switched absorber to a new frequency. This paper briefly develops the fundamental analysis tools for a Single-Degree-of-Freedom state-switchable device, and then considers the application of such a device for the purpose of vibration control in a 2-DOF system. Simulation results indicate that state-switched vibration absorbers may be advantageous over classical passive tuned vibration absorbers under certain conditions.
Improved Barrier Properties with Metallized Films from Corona Process Improvements and from Copolymer Characteristics
Authors: Campbel R. Neil , Wolters Detlef
Published: August 2002

Vastly improved film surface tension values were achieved using elevated corona treater roll temperatures in the production of BOPP film with a coextruded skin layer designed for subsequent metallization. These film surface tension values did not significantly decrease with time. A new propylene/butene-1 copolymer was coextruded as the metallizing layer in the BOPP film construction. When metallized, this film provided improved barrier to water vapor transmission by a factor of 5:1 when compared to a similar film produced with a propylene/ethylene copolymer as the metallizing layer. Stringent analysis of the surface of the propylene/butene copolymer revealed that the unique smoothness of its surface enhanced the barrier properties of the film after metallizing. The surface of the ethylene/propylene copolymer was much rougher.
Hybrid Control of a Cantilevered ER Sandwich Beam for Vibration Suppression
Authors: Shaw Jinsiang
Published: August 2002

In this paper experimental studies on vibration suppression of a cantilevered ER sandwich beam subjected to periodic disturbances are conducted. The employed controller combines a semi-active controller with an active controller and is thus termed hybrid controller. The semi-active controller is based on fuzzy-like control strategy and the active controller uses a plant disturbance canceler for disturbance canceling The semi-active controller can apply an optimal electric field to the ER sandwich beam for improving the transient response, while the active controller provides a negating actuation force for improving the steady state response. Experimental results show that performance of the hybrid controller is superior to those of the semi-active and active controllers in suppressing the undesired vibration of the ER sandwich beam.
Investigation of the Radiation Crosslinked Foams Produced from Metallocene Polyolefin Elastomers/Polyethylene Blend
Authors: Kim D. W. , Kim K. S.
Published: August 2002

In order to produce low-density crosslinked foam of superior properties having a uniform cell structure from POEs/LDPE blends, the crosslinking efficiency of resin, behavior of crosslinking sensitizer, mechanical properties according to the irradiation dose, and compressive strength in different cell sizes have been examined. When POE/LDPE (70/30) was irradiated at 3 Mrad, the gel content was 18.5%, but the addition of 0.3 phr of TATM only increased gel content up to 36%. The lower the melt index of the resin, the more the gel fraction increase was confirmed. Although tensile strength increased up to a certain point in proportion to the gel content, the decrease of tensile strength was observed over the fixed gel content. The effect of polyfunctionality was investigated by analyzing the gel fraction in accordance with the number of double bonds in molecules of crosslinking sensitizers. As a result of the measurement of changes on compressive strength according to the sizes of different foam cells, having the same degree of density, bigger cells showed stronger compressive strengths when compressed at 25%, while foams containing smaller cells showed superior compressive strengths when compressed over 50%.
Determination of the Elastic Properties of Composite Materials by Tensile Testing and Ultrasound Measurement
Authors: Mistou S. , Karama M.
Published: August 2002

A comparative study on different ways to determine the mechanical properties of four glass fiber composite materials, two of which with orthotropic behaviour, is developed in this paper. This work highlights the accuracy of the results obtained by means of a low cost dynamic characterization method which is developed as part of nondestructive evaluation by ultrasonic wave velocities measurement, compared to a static characterisation method by tensile testing.
Gas Diffusion in Closed-Cell Foams
Authors: Pilon Laurent , Fedorov Andrei G. , Viskanta Raymond
Published: August 2002

The objective of this paper is to present an engineering model, based on fundamentally sound but simplified treatment of mass diffusion phenomena, for practical predictions of the effective diffusion coefficient of gases through closed-cell foams. All assumptions and simplifications that define the range of applicability of the proposed model are clearly stated. The model developed is based on the electrical circuit analogy and on the first principles. The analysis suggests that the effective diffusion coefficient through the foam can be expressed as a product of the geometric factor and the gas diffusion coefficient through the foam membrane. Comparison of model predictions with experimental data available in the literature shows satisfactory agreement. Discrepancies between predictions and data have been noted for gases with high solubility in the condensed phase for which Henry's law does not apply. Additional experimental data for both the foam morphology and the diffusion coefficient in the membrane are needed to fully validate the model.
Characterization and Performance of Electrorheological Fluids Based on Pine Oils
Authors: Mäkelä Kimmo K.
Published: August 2002

The purpose of this paper is to study the characteristics and performance of pine oil and its ester as a base fluid material for electrorheological fluids. Here, all the tested fluids had a relatively low concentration level of between 5-15% of weight to study the electrorheological strength and phenomena for rotary machines as an application for keeping the working fluid in a steady position while the machine is not working.

The objective of this basic study is to give an introduction to the electrorheological fluids based on polyaniline particles and pine oil and to measure their dependencies on changes in the applied external electric field, temperature, shear rate, dynamic viscosity and concentration, and to study the influence of grinding the particles.
Strategies for Injection Filling Velocity Control
Authors: Yang Yi , Gao Furong
Published: August 2002

Injection velocity during filling stage was experimentally controlled using different control algorithms, from simple open-loop control and Proportional-Integral (PI) closed-loop control, to more advanced strategies such as Self-Tuning Regulator (STR), fuzzy control and Generalized Predictive Control (GPC). It is shown that the advanced control can effectively overcome the nonlinear and time-varying characteristics of the filling velocity. The advantages and drawbacks of each strategy are presented and experimentally illustrated. The use of advanced control strategies is shown to be necessary for accurate control of the injection velocity with good repeatability.
On the Integration of Piezoceramic Actuators in Composite Structures for Aerospace Applications
Authors: Durr Johannes K. , Herold-Schmidt Ursula , Zaglauer Helmut W. , Arendts Franz Joseph
Published: August 2002

Up to now experimental and theoretical research on active structures for aerospace applications has put the focus mainly on surface bonded actuators. Simultaneously piezoceramics became the major type of actuating device being investigated for smart structures. In this context various techniques of insulating, bonding and operating these actuators have been developed. However, especially with regard to actuators, only a few investigations have dealt with embedding of these components into the load bearing structure so far. With increasing shares of fibre-reinforced plastics applied in aerospace products the option of integrating the actuation capability into the components should be reconsidered during the design process.

This paper deals with different aspects related to the integration of piezoceramic actuators into fibre reinforced aerospace structures. An outline of the basic possibilities of either bonding an actuator to the structure's surface or embedding it into the composite is given while the emphasis is put on different aspects related to the latter technology. Subsequently, recent efforts at DaimlerChrysler Aerospace Dornier concerning aircraft components with surface bonded actuators are presented. Design considerations regarding embedded piezoceramic actuators are discussed. Finally, some techniques of nondestructive testing applicable to structures with surface bonded as well as embedded piezoelectric actuators are described.
Dispersion of Birefringence and its Influence on On-Line Measurement of Stresses in Polymer Films
Authors: Redner A. S. , Treadway B. , Greener J.
Published: August 2002

Birefringence distribution in biaxially oriented polymer films is often used to assess non-uniformities in processing and in physical properties. Off-line characterization of this property can be performed by direct measurement of anisotropy in the refractive index, a process that is slow and not suitable for on-line use. By comparison, the spectral contents analysis (SCA) method is fast and easily adaptable for on-line process monitoring and real-time process control. However, implementation of this method requires accurate knowledge of the chromatic dispersion of birefringence. This paper discusses the contribution of birefringence dispersion to the precision of birefringence measurements by the SCA method, and it describes a new spectrometric procedure for accurate measurement of this material property.
The Management of Acute Severe Asthma
Authors: Kelly H. William
Published: August 2002

Acute severe asthma exacerbations resulting in emergency department visits and hospitalization usually constitute a failure of long-term control therapy. However, even patients with relatively mild asthma can have severe life-threatening episodes. In both children and adults, viral respiratory infections are the major triggering event, although outbreaks of severe asthma have been associated with high concentrations of aeroallergens. Patients should be provided with written action plans on what to do for acute deterioration, and more severe patients may keep prednisone at home to begin after consultation with their physician. The primary therapy of acute asthma exacerbations remains frequent administration of aerosol β2-agonists and systemic corticosteroids for those patients not fully responding to the β2-agonists. Mild exacerbations may be treated with an increased dosage of inhaled corticosteroids. Patients at risk for acute exacerbations may benefit from peak flow measurement, particularly those who have difficulty perceiving airway obstruction. It is recommended that patients remain on full dose of prednisone until they achieve 70-80 percent of predicted normal or personal best peak flow. In the emergency department, the use of β2-agonists by metered-dose inhaler and holding chamber is as effective as nebulizer if given in a sufficient dose 6-10 puffs equivalent to 5 mg via nebulizer. In those patients not responding completely, the addition of ipratropium bromide has shown to produce additive bronchodilation and reduce hospitalizations. Other therapies such as magnesium sulfate, intravenous β2-agonists, heliox and ketamine have been used, but data demonstrating efficacy are insufficient to warrant recommending their general use.
The Use of Clay in an EVA-Based Intumescent Formulation. Comparison with the Intumescent Formulation Using Polyamide-6 Clay Nanocomposite As Carbonisation Agent
Authors: Dabrowski FrançOis , Le Bras Michel , Cartier Laurent , Bourbigot Serge
Published: August 2002

This work deals with the use of clay as a filler in an intumescent EVA-based formulation using a charring polymer (polyamide-6) as a carbonization agent. Using PA-6 clay nanocomposite instead of pure PA-6 had been shown to improve the fire properties of the intumescent blend. In this study, using clay as a “classical” filler enabled the same level of FR performance to be obtained in the first step of the combustion as when directly using exfoliated clay in PA-6. But in the second half of the combustion, the clay destabilizes the system and increases the flammability.

Moreover, a kinetic modeling of the degradation of the EVA-based formulations shows that adding clay to the blend enables the same mode of degradation and the same invariant parameters as for the polyamide-6 clay nanocomposite containing intumescent blend. It is assumed that these kinetic data can be correlated with the improvement of the fire performance in the first step of combustion as observed under the cone calorimeter. The increase in the flammability by the K-10 in the second half of the combustion shows the advantages of using nanoclay rather than micronclay in an intumescent system.
The Effect of Padding Foam on the Compression Characteristics of Some Agglomerated Food Powders
Authors: Yan H. , Barbosa-Cánovas G. V.
Published: August 2002

Selected padding foam was used to reduce attrition in agglomerated food powders. This is a widely used strategy in fruits and vegetables during harvesting and processing to minimize impact damage. The objective of this research was to determine the padding effect on some agglomerated food powders when plastic foams of different thicknesses were added in the powder bed at different positions while conducting confined uniaxial compression tests. The padding effect was evaluated by two proposed indices: padding index and padding efficiency. The former index was based on the force-deformation behavior of the compression process, while the latter was based on weight comparisons of agglomerates retaining their original particle size with or without the use of padding foams. The padding thickness and positions significantly affect the force-deformation relationships for both agglomerates: instant coffee and instant milk. The padding effect, in terms of padding efficiency and padding index, was more obvious when the padding material was put at the top of the powder bed. The padding efficient index is more useful, in the cases under consideration, than the other index, because it should be more sensitive in depicting attrition.
Application of Internal Model Based Controller to Active Vibration Suppression System
Authors: Yuan Shu-Qing , Xu Qing-Yu , Zhang Ling
Published: August 2002

More and more attention has been attracted to active vibration control with intelligent materials such as piezoelectric materials, etc. This paper deals with the problem of active vibration control of mechanisms. An internal model based controller is suited for regulation problems with periodic disturbance or tracking problems with periodic input. It has the ability to reject periodic disturbances, at the same time it is robust to parameter perturbation. In this paper an internal model principle is introduced, and simulations are carried out to show its features. In addition, the control strategy is implemented for active vibration suppression of a flexible four bar linkage bonded with piezoelectric materials as sensors and actuators. When the mechanism rotates, periodic inertial forces serve as a disturbance to induce vibration along the flexible coupler. The purpose of the experiment is to suppress this vibration using a piezoelectric actuator. The experimental system is built up with computer, A/D and D/A converter, piezoelectric sensor and actuator, low-pass filter, voltage amplifier and charge amplifier. Encouraging results are gained when the strategy is implemented in the experiments.
A Means of Calculating the Fire Points of Organic Compounds
Authors: Jones J. C.
Published: August 2002

Flash points for four liquid organic compounds— m-Xylene, n-butanol, n-decane and n-dodecane—are calculated on the principle that the fire point occurs when the pressure of the vapour is 1.5 times the stoichiometric value. Fire points so calculated are compared with experimental values from the literature, and agreement is very good.
Analysis of the Ductility on Short Fiber Reinforced Polypropylene Plates
Authors: Barbosa Silvia E. , Kenny Jose M.
Published: August 2002

The incorporation of fibers improved the mechanical properties of the thermoplastic matrix and also modified impact and fracture behavior. An experimental study of dynamic fracture behavior of short fiber reinforced poly-propylene was carried out in an instrumented impact pendulum on notched izod specimens and the variation of the ductility in different points of a rectangular injected plate was studied. The different mechanisms of fracture were analyzed following the information given by force-time and energy-time curves obtained from experiments performed on the neat matrix and on its glass fibers composites.
Design and Development of Tunable Multi-Layer Smart Antennas Using Ferroelectric Materials
Authors: Teo P. T. , Vinoy K. J. , Jose K. A. , Varadan V. K. , Varadan V. V. , Gan Y. B.
Published: August 2002

It is well known that microstrip antennas on high permittivity substrates (e.g., ferroelectric materials) suffer from narrow bandwidth and poor efficiency that is due to the energy loss associated with the excitation of surface waves modes. This problem could be solved with several multi-layered antenna configurations presented in this paper. It is known that the optimization of these multi-layer antennas requires simultaneous variation of the dielectric constant, air gap, and the thickness of substrate layer. The simulation studies presented in this paper, using An soft Ensemble shows that for electromagnetically-coupled air gap multi-layered structure, a positive gain of 2 dB is achieved, resulting in a gain improvement of at least 5 dB compared to the poor gain performance of a single layered structure. It is shown that stacking a ferroelectric layer directly on top of a conventional microstrip antenna could eliminate the air gap spacing. This design has additional advantages like improvement in gain and creates a tunable dual band antenna performance. A larger gain improvement is also realized with this direct-stacking arrangement compared to the air-gap coupled structure. These antennas may find wide applications in intelligent systems and structures.
Molecular Design of Self-Oscillating Polymer Gels and Their Dynamic Swelling-Deswelling Behaviors
Authors: Yoshida Ryo , Yamaguchi Tomohiko , Kokufuta Etsuo
Published: August 2002

We report a novel "intelligent" gel that undergoes an autonomous swellingdeswelling oscillation without reliance on an alteration in external conditions. The mechanical oscillation in our gel system was produced via oscillating chemical reaction similar to metabolic reaction, called the Belousov-Zhabotinsky (BZ) reaction. We prepared gels composed of crosslinked Nisopropylacrylamide (NIPAAm) networks to which ruthenium tris(2,2'-bipyridine) (Ru(bpy)3), a catalyst for the BZ reaction, was covalently bonded. The BZ reaction occurring within the gel matrix generates periodic redox changes of the catalyst moiety: Ru(bpy)32+ T Ru(bpy)33+. As a result, the gel exhibits a periodical swelling-deswelling change. When the gel size is smaller than the chemical wavelength, the redox change occurs homogeneously in the gel. In this case, the swelling-deswelling oscillation is isotropic and the chemical and mechanical oscillations are synchronized without a phase difference. In the case of a large rectangular gel, the total length of the gel periodically changes with the propagation of chemical waves. However, an "anti-phase mode" between the chemical and mechanical oscillations was observed. This phenomenon was explained by a theoretical model simulation. It has become apparent that a change in the overall gel length is equivalent to that in the last stationary wave at the free end. The dynamic behavior that locally shrunken (or swollen) parts propagate is similar to the peristaltic motion observed in worms.