bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Cues Reduce the Latency to Name Rotated Images of Objects
Authors: Nicholson Karen G , Humphrey G Keith
Published: August 2002

Jolicoeur (1985, Memory & Cognition13 289–303) found a linear increase in the latency to name line drawings of objects rotated (0° to 120°) from the upright (0°) in the initial trial block. This effect was much shallower in later blocks. He proposed that the initial effect may indicate that mental rotation is the default process for recognising rotated objects, and that the decrease in this effect, seen with practice, may reflect the increased use of learned orientation-invariant features. Initially, we were interested in whether object–colour associations that may be learned during the initial block, could account for the reduced latency to name rotated objects, seen in later blocks. In experiment 1 we used full-cue colour images of objects that depicted colour and other surface cues. Surprisingly, given that Jolicoeur's findings were replicated several times with line drawings, we found that even the initial linear trend in naming latency was shallow. We replicated this result in follow-up experiments. In contrast, when we used less-realistic depictions of the same objects that had fewer visual cues (ie line drawings, coloured drawings, greyscale images), the results were comparable to those of Jolicoeur. Also, the initial linear trends were steeper for these depictions than for full-cue colour images. The results suggest that, when multiple surface cues are available in the image, mental rotation may not be the default recognition process.
The salt-waterlogging tolerance of Eucalyptus camaldulensis x E. globulus hybrids
Authors: Meddings R. L. A. , McComb J. A. , Bell D. T.
Published: August 2002

The salt–waterlogging tolerance of
Eucalyptus camaldulensis ×
E. globulus hybrids was compared with parental clones of
E. camaldulensis, open-pollinated seedlings of
E. globulus and
Eucalyptus camaldulensis ×
E. camaldulensis seedlings in a glasshouse trial.
Seven-month-old plants were waterlogged for 10 weeks with a saline solution of
increasing concentration to 350 mmol NaCl/L.
Eucalyptus camaldulensis had higher tolerance to
salt–waterlogging than E. globulus as assessed by
survival and height growth rate. The performance of the hybrid families was
intermediate between the 2 parental species as was the performance of progeny
from crosses between salt tolerant E. camaldulensis
parents. Within families some hybrid individuals performed as well as the
E. camaldulensis parents. The most tolerant plants have
been micropropagated for further experiments and field trials on saline
agricultural land.
Monimiaceae sensu lato, an element of Gondwanan polar forests: Evidence from the late Cretaceous-early tertiary wood flora of Antarctica
Authors: Poole Imogen , Gottwald Helmut
Published: August 2002

Palaeofloristic studies of the Antarctic Peninsula region are important in
furthering our understanding of (i) the radiation and rise to ecological
dominance of the angiosperms in the Southern Hemisphere during the Late
Cretaceous and (ii) the present day disjunct austral vegetation.
Investigations of Upper Cretaceous and Early Tertiary sediments of this region
yield a rich assemblage of well-preserved fossil dicotyledonous angiosperm
wood which provides evidence for the existence, since the Late Cretaceous, of
temperate forests similar in composition to those found in present-day
southern South America, New Zealand and Australia. This paper describes two
previously unrecognised morphotypes, which can be assigned to the Monimiaceae
sensu lato, and represents the first record of this
family in the wood flora of Antarctica. Specimens belonging to the first
fossil morphotype have been assigned to Hedycaryoxylon
SÜss (subfamily Monimioideae) because they exhibit anatomical features
characteristic of Hedycaryoxylon and extant
Hedycarya J.R.Forst. & G.Forst. and
Tambourissa Sonn. Characters include diffuse porosity,
vessels which are mainly solitary with scalariform perforation plates,
opposite to scalariform intervascular pitting, paratracheal parenchyma,
septate fibres and tall (>3 mm), wide multiseriate rays with a length:
breadth ratio of approximately 1: 4. Specimens belonging to the second
morphotype have been assigned to Atherospermoxylon
KrÄusel, erected for fossil woods of the Monimiaceae in the tribe
Atherospermeae (now Atherospermataceae) in that they exhibit anatomical
features similar to Atherospermoxylon and extant
Daphnandra Benth., Doryphora Endl.
and Laurelia novae-zelandiae A.Cunn. These characters
include diffuse to semi-ring porosity, scalariform perforation plates with up
to 25 bars, septate fibres, relatively short (<1 mm) rays with a length:
breadth ratio of between 1: 4 and 1: 11.
Pecking preferences in hatchlings of the Australian brush-turkey, Alectura lathami (Megapodiidae): the role of food type and colour
Authors: Göth Ann , Proctor Heather
Published: August 2002

Chicks of megapodes, including the Australian brush-turkey,
Alectura lathami, live independently, without parents to
show them where and what to eat. This paper represents the first investigation
of how megapode chicks find and identify food. The specific questions
addressed are: whether naive brush-turkey hatchlings are able to differentiate
between food and objects that do not give a nutritional reward; whether they
possess a preference for certain types of food; and which factors are most
likely to trigger feeding in hatchlings.
The three questions were approached by pairwise choice tests of two types. In
Type 1, chicks were offered mealworm larvae, fruit cubes, seeds and
non-nutritious objects (pebbles); in Type 2, chicks were offered beads of four
different colours (red, green, blue and yellow). The median peck rate at
pebbles was always significantly lower than that at mealworms, fruit or seeds.
Mealworms received significantly more pecks than seeds or pebbles. Chicks
showed no clear preference for any colour. All chicks also directed some pecks
at ‘other items’ that appeared to display a strong contrast
against the background of the box they were kept in, either in colour (e.g.
dark knotholes in light brown wood) or in shape (three-dimensional, such as
claws and faeces). Hatchlings seem to direct their initial pecks at objects
that have certain characteristics in common, such as contrast, movement (for
live prey) and reflective surfaces (for fruit or seeds). Preference for these
rather general characteristics may be adaptive considering that chicks can
hatch in various habitats and different months of the year, making the types
of food available at hatching unpredictable.
Development of High-Performance Actuators Using ER Fluids
Authors: Sakaguchi Masamichi , Furusho Junji
Published: August 2002

We developed ER actuators with high performance. An ER actuator consists of ER clutch, reduction gear unit and electric motor. The electrodes of the output-shaft side in the developed ER actuators are made of light material such as CFRP, and the moment of inertia of the ER actuators with respect to the output-shaft becomes very small. As a result, the large torque/inertia ratio can be obtained, compared with conventional actuators. When comparing with powder clutches in which the torque/inertia ratio is considered to be extremely high, the torque/inertia ratio of small-size ER actuators is not inferior. Considering the slow response property of powders in powder clutches, it can be stated that ER actuators are devices with extremely high response characteristics. Firstly we discuss the design and structure of ER actuators. Secondly the experimental results are presented. Then, the control experiments are executed. The developed ER actuators are used in order to develop the new force display system which has high-fidelity force-presentation ability.
Static Energy Absorption Capacity of Graphite-Epoxy Tubes
Authors: Schultz Marc R. , Hyer Michael W.
Published: August 2002

This paper examines the energy absorption capacity of Akzo Nobel Fortafil 50k carbon fiber composite tubular specimens crushed axially in a quasi-static fashion. The towpreg form of this material, obtained from Thiokol, was filamentwound to produce specimens. Circular and square tubular specimens with ± 45° and ± 45°/0° fiber orientation schemes were studied. As a baseline comparison, similar tubular specimens were fabricated using T300 12k fiber, an aerospace standard. The fundamental issue was to study the energy absorption capacity of the lower cost 50k material in comparison to the 12k material, and to determine the influence of specimen geometry and fiber orientation schemes on the energy absorption capacity. It can be concluded that, overall, the specimens made of the 50k material had lower average crush loads and specific energy absorptions (SEAs) than the specimens made of 12k material. The load ratios for the 50k specimens were slightly higher than for the 12k specimens. It can be also concluded that for both the 12k and 50k material the square specimens had lower SEAs than the circular specimens. The presence of the 0° fibers had some influence on the SEAs of the circular 50k specimens and some influence on the load ratios of the circular 12k specimens, but otherwise they had little influence. The work is important and timely because of the current search for more cost-effective rawmaterial forms and the need to understand their response characteristics.
Influence of Fiber Surface Characteristics on the Flax/Polypropylene Interface
Authors: van de Velde Kathleen , Kiekens Paul
Published: August 2002

Dew retted hackled long flax was treated with propyltrimethoxysilane, phenylisocyanate, and maleic acid anhydride modified polypropylene (MAA-PP). The wetting parameters of the untreated and treated flax fibers were obtained with dynamic contact angle measurements. The results showed that the treated flax fibers are less polar than the untreated flax fiber. The interfacial adhesion between the flax fibers and poly-propylene, respectively, maleic acid anhydride modified polypropylene, was studied with fiber pull-out tests. The highest increase in apparent shear stress was obtained by treatment of the flax fiber with MAA-PP.
Acoustic Emission Analysis for Fatigue Prediction of Lap Solder Joints in Mode Two Shear
Authors: Van De Wal Bryan J. , Kendall Gay , Sammakia, Bahgat , Sahay C. , Constable James
Published: August 2002

This current research method combined the disciplines of Fractography, ConFocal analysis, and Acoustic Emission to discover and identify failure modes of eutectic (62%Sn36%Pb2%Ag) solders (with and without rosin core flux) and lead free (99CSn-Cu) solder under cyclic displacement controlled Mode II shear fatigue. Results show a strong pattern of acoustic emission correlating to stages of failure. Three distinct stages were found: “Stage I” (crack initiation), “Stage II” (nucleation), and “Stage III” (failure and/or propagation). Time domain analysis shows distinct waveforms for each stage of fatigue. The frequency domain analysis shows a distinct pattern in the PSD. The combination of these two trends allows for a basis to predict solder joint fatigue in an acoustical manner utilizing acoustic emissions. Fractographic results support the trends seen in the acoustic emission analysis for each stage of fatigue. Dominant failure modes of specimens appeared to be intermetallic crack growth, grain coarsening, and dislocation energy effects. These failure modes can be explained in both the time and frequency responses of these specimens. The conclusion is that utilizing acoustic emissions with the disciplines of Acoustic Emissions, Fractography, ConFocal analysis has uncovered and identified failure modes of eutectic (62%Sn36%Pb2%Ag) solders (with and without rosin core flux) and lead free (99CSn-Cu) solder under cyclic displacement controlled Mode II shear fatigue.
Thermal Diffusivities of Simulated Fuel-Mineral Blends
Authors: Jones J. C. , Bailey R. S. , Bale K.
Published: August 2002

Using blends of an organic polymeric material and sand and gravel, solid fuels of widely varying ash content are simulated and their thermal diffusivities are determined experimentally. The results are processed in terms of the product (thermal diffusivity × bulk density), as a function of the organic fraction, and tested against previously reported experimental results for high-ash low-rank coals, with very gratifying agreement.
Electrically Driven Polypyrrole Film Actuator Working in Air
Authors: Okuzaki Hidenori , Funasaka Keiichi
Published: August 2002

The polypyrrole (PPy) films containing tetrafluoroborate ions were electrochemically synthesized and electrically driven motion of the film was investigated. The application of dc voltage brought about reversible contraction of the film in air, where the degree of contraction increased with increasing both applied voltage and ambient humidity. The contraction of the film was associated with desorption of water vapor due to the Joule heating, which was different from electrochemical doping and dedoping. The degree of contraction attained 1.2% under 2 V, where the initial speeds of contraction and expansion of the film were 4.4 and 1.8% min-1, respectively. Under loading conditions, the power density increased with increasing load and the value attained 0.78 W kg-' (6 V.W) under the load of 60 g (4 MPa). The energy efficiency, defined as the ratio of work done by the PPy film to the electric energy, was calculated as 6.6 x 10-3%.
Active Control of ER Valves with Application to Seaport Cargo Handling System
Authors: Choi S. B. , Sung K. G. , Chung D. D. , Kim H. S.
Published: August 2002

This paper presents the position control of a cylinder system using electro-rheological (ER) valves with application to a seaport cargo handling system. On the basis of the field-dependent yield stress of the ER fluid, cylindrical ER valves are designed and manufactured. The ER valve bridge circuit for the position control of the cylinder is formulated and its governing equation of motion is derived. In order to demonstrate the position controllability, the bridge circuit is applied to a laboratory model of a cargo handling system consisting of two principal components: container palette transfer car and platform controlled by ER valve-bridge cylinder. After describing the principle of loading and unloading procedures, a sliding mode controller is designed for the platform which needs to be tracked the position of the cargo ship subjected to time-varying tide and wave motion. The controller is experimentally realized and position control results are presented.
Failure Modes of Foams: The Influence of Orientation of Voids
Authors: Theocaris Pericles S. , Sokolis Dimitrios P.
Published: August 2002

An experimental investigation is undertaken in this paper for the assessment of the failure behavior of a series of polyurethane foams of variable specific density. All foamy materials examined here were acknowledged as transversely isotropic materials, whose axis of symmetry is, however, the weak axis of the medium. Simple uniaxial tension and compression tests were executed, and the experimental data were introduced into the elliptic paraboloid failure surface criterion. This condition was utilized for the comparison of the failure loci, associated with primary failure, of the polyurethane foams of different porosities.

As a result, it is shown that, when the specific density of the foamy solids is raised, the shape, position and alignment of their failure loci intersections by the principal stress planes, as well as by the principal diagonal planes, is adjusted significantly. In addition to this fact, their degree of anisotropy is augmented; however, it is noted that the totality of the foamy materials tested exhibit solely compression-strong failure characteristics. Next, the influence of the voids’orientation on the failure modes of foams is investigated, by evaluating the variation of the essential parameters, required for the precise definition of the failure loci of the weak-axis polyurethanes, with respect to their specific density. And, further, by contrasting this variation with the respective one for the strong-axis foams encountered in previous studies of the senior author (Theocaris, 1992a,b; 1998). Hence, a comprehensive comparison of the failure behavior of foams, which display a weak and strong-axis of symmetry, is succeeded, revealing their similarities, but most importantly, their peculiarities and idiosyncrasies. Finally, a numerical analysis is disclosed as a means of determining the failure characteristics of mixed foams, that consist of both strong and weak-axis polyurethane materials of different specific densities. Accordingly, the effect of variation of the relative proportions and the specific densities of the constituent foamy phases on the characteristic parameters, designating the failure loci of mixed foams, is studied, offering interesting results concerning the modes of failure of such foams.
A Comparison between Electrorheological and Magnetorheological Fluids Subjected to Impulsive Loads
Authors: El Wahed Alu K. , Sproston John L. , Schleyer Graham K.
Published: August 2002

This paper is concerned with an experimental comparison of the dynamic performance of an Electrorheological and a Magnetorheological fluid when subjected to impulsively applied loads. The ER device was built as a squeeze cell incorporating an ER fluid sandwiched between two electrodes which, during impact, move towards each other, whilst the MR device was a commercially available vibration absorber. Each device was mounted in an experimental rig which was capable of determining the instantaneous responses of the fluids. The transient characteristics of the devices were assessed for various mechanical force levels and, for the ER device, under DC excitation of the fluid in conjunction with a digital controller to provide a constant applied electrical field.
Motion Control of Direct-Drive Motor by a Homogeneous ER Fluid
Authors: Takesue Naoyuki , Zhang Guoguang , Furusho Junji , Sakaguchi Masamichi
Published: August 2002

Since a direct-drive (DD) motor system doesn't have the reduction gear, the structure of the servo system can be simple and stiff. On the other hand, in the DD system, the disturbance torque directly influences the accuracy of the motor control. The high servo gain is effective and important for reducing the influence of the disturbance torque. However, the high servo control often makes the control system unstable or vibratory. Therefore, the servo gain must be lowered for assuring stability, and the influence of the disturbance becomes serious. In this study, the DD motor system using an ER fluid damper is discussed. By applying the ER damper to the DD motor system, it is possible to obtain the mechanical damping and to realize a high servo gain in the motion control. Finally, the effectiveness of the proposed system is confirmed experimentally.
Foaming of Thermoplastic Elastomers with Water
Authors: Sahnoune Abdelhadi
Published: August 2002

We present results on foaming of a thermoplastic elastomer (TPE) using water as the physical blowing agent. The TPE is a blend of polypropylene and fully crosslinked EPDM rubber made by a dynamic vulcanization process. The influence of the blowing agent content, and the processing conditions on foam density, cell nucleation, and foam structure are discussed. A brief discussion about the similarities and the differences between foaming in homopolymers and in TPEs is also included.
Modeling Low-Velocity Impact Damage of Composite Sandwich Panels
Authors: Fatt Michelle S. Hoo , Park Kyong S.
Published: August 2002

Analytical solutions for the low-velocity impact damage of composite sandwich panels are found by considering systems of discrete masses, springs and constant-force dashpots. Equivalent spring and dashpot forces for the sandwich panel are derived from the static load-indentation response and adjusted with dynamic material properties of the facesheet and core. Predictions of the maximum impact force are about 15% higher than experimental values, which is the same order of accuracy that is obtained from the static load-indentation analysis. Damage initiation due to tensile failure by hemispherical-nose shape projectiles and shear failure by blunt projectiles are examined. Predicted tensile and shear failure loads are about 20% higher than experimental results.
Damage Tolerance and Repair of GFRP Warships
Authors: Elliott D. M. , Trask R. S.
Published: August 2002

The United Kingdom has operated glass-fiber-reinforced plastic (GFRP) minesweeper vessels since the early 1970s. Under typical operating conditions they may sustain minor impact damage, leading to delaminations within the hull shell and debonding of the stiffener frames. Such damage is costly to repair, and hence there has been a move towards cost reduction through better understanding of the structural behavior of typical defects under the loading conditions present within the structure. This approach, using damage tolerance techniques, has led to a relaxation in the requirement for repair, and consequently the number of repairs has been substantially reduced. In addition, advance techniques have been developed using resin infusion technology for the re-attachment of debonded stiffener frames.

The structural element tests used to validate the damage tolerance philosophy will be examined and the resin-infusion repair method explained using a case study detailing its first successful application.
Constitutive Equations of Viscoelasticity and Estimation of Viscoelastic Parameters of Unidirectional Fibrous Polymeric Composites
Authors: Klasztorny M. , Wilczynski A. P.
Published: August 2002

A method for modelling viscoelastic properties of fibre reinforced polymeric composites, based on the original reinforcement theory as well as original description of viscoelasticity of the matrix [4}, is developed in the paper. The composite material consists of a viscoelastic isotropic polymer matrix and elastic monotropic fibres. In order to model arbitrary shear/bulk creep in the matrix, the Mittag-Leffler fractional exponential functions are used as the generating functions. Hence, the viscoelastic model of the polymer matrix is described with 2 elastic constants and 6 viscoelastic constants, while the elastic properties of the fibres are described with 5 well-known elastic constants. Both groups of the material constants can be estimated experimentally relatively easy. Coupled constitutive equations of linear viscoelasticity of a unidirectional fibrous polymeric composite, modeled as a homogeneous monotropic material are formulated in the study. The viscoelastic model of the composite is described using 5 elastic constants and 27 viscoelastic constants, i.e., 9 long-lasting compliance ratios, 9 retardation times, and 9 fractions defining an order of the fractional exponential functions. The elastic-viscoelastic analogy is used to predict theoretically the complex compliances of the composite [4]. An iterative optimization procedure for theoretical prediction of the viscoelastic constants of the composite is formulated, computerised and positively tested on the selected composite materials.
Efficiency of Frequency-Rectified Piezohydraulic and Piezopneumatic Actuation
Authors: Nasser Khalil , Leo Donald J.
Published: August 2002

Piezohydraulic and piezopneumatic frequency rectification is analyzed with a steady-state model of work and energy transfer. In this paper, piezohydraulic actuation is defined as the use of incompressible fluid to rectify the oscillatory motion of a piezoelectric device into unidirectional motion; piezopneumatic actuation is the use of a compressible gas such as air. The steady-state analysis is based on the definition of two efficiency metrics. The mechanical efficiency is defined as the ratio of mechanical work transferred to the load to the total mechanical work performed by the actuator, and the electrical efficiency is defined as the ratio of electrical energy expended to the peak energy required. The analysis demonstrates that piezohydraulic rectification is inherently more efficient than piezopneumatic rectification due to the assumption of fluid incompressibility. The mechanical efficiency is 100% when using incompressible fluid (ideal) but drops to below 40% when using compressible gas. The maximum electrical efficiency of piezohydraulic rectification is also four times higher than that of piezopneumatic actuation (29% to 7%). The overall efficiency of the rectification process (defined as the product of the mechanical and electrical efficiencies) is an order of magnitude greater when using incompressible fluid than when using compressible gas (29% to 2.8%). Thus, frequency rectification using compressible gas will require peak energy inputs that are ten times greater than that of incompressible fluid for an equivalent amount of mechanical work output. The significant difference in peak energy requirements is attributed to the reduced coupling between the actuator and the load that occurs due to compressibility of the gas. These results represent an upper bound on the efficiency because they neglect other sources of system losses, such as material hysteresis and frictional losses within the piston and seals of the actuator.
Influence of Microstructure Coarsening on Thermomechanical Fatigue Behavior of Pb/Sn Eutectic Solder Joints
Authors: Tang Hong , Basaran Cemal
Published: August 2002

The influence of microstructure coarsening on thermomechanical fatigue behavior of eutectic solder joint is investigated by numerical simulation. A phase growth model is selected based on the experimental observation and incorporated in a damage mechanics based viscoplastic constitutive model. Comparisons between the simulations with and without coarsening effect are made for isothermal, cyclic shear testing and thermal cycling of solder joints in BGA electronic packaging.
Robust Pole Assignment for Vibration Control of Flexible Structures
Authors: Okubo Hiroshi , Ichikawa Hiroyuki
Published: August 2002

This paper proposes a method of structure/controller design by robust pole assignment for active vibration suppression of flexible structures. The proposed method assigns the closed-loop poles at the specified point in the complex plane and quasi-minimizes the condition number of the closed-loop modal matrix via structure/controller design. Reducing the condition number improves stability robustness and control performance of the designed closed-loop system. This paper also introduces a new index of condition number for the cost function. Use of this index in place of an actual condition number reduces computational effort and improves problem solvability significantly. Feasibility of the proposed method is demonstrated with numerical examples.
Catastrophe Dynamics of Dust-Cloud Ignition Phenomena
Authors: Zhikang Xie
Published: August 2002

This paper takes ignition and quenching phenomena of a dust-cloud explosion system as an example to illustrate the application prospect of catastrophe theory in dust explosion science. Through comparative study on catastrophe dynamics of a dust-cloud explosion system under different heat loss models, the significance of catastrophe dynamics of radiation effect in igniting behavior of a dust explosion system is indicated. It is also pointed out that a simplified representation of igniting process model may possibly change catastrophe set’s topological structure and stationary state structure of a dust explosion system, and therefore may have an important influence on realizing igniting process laws. The statement may be useful for understanding many other discontinuity phenomena widely existent in objective world system.
Improved Helicopter Aeromechanical Stability Analysis Using Segmented Constrained Layer Damping and Hybrid Optimization
Authors: Liu Qiang , Chattopadhyay Aditi
Published: August 2002

Aeromechanical stability plays a critical role in helicopter design and lead-lag damping is crucial to this design. In this paper, the use of segmented constrained damping layer (SCL) treatment and composite tailoring is investigated for improved rotor aeromechanical stability using formal optimization technique. The principal load-carrying member in the rotor blade is represented by a composite box beam, of arbitrary thickness, with surface bonded SCLs. A comprehensive theory is used to model the smart box beam. A ground resonance analysis model and an air resonance analysis model are implemented in the rotor blade built around the composite box beam with SCLs. The Pitt-Peters dynamic inflow model is used in air resonance analysis under hover condition. A hybrid optimization technique is used to investigate the optimum design of the composite box beam with surface bonded SCLs for improved damping characteristics. Parameters such as stacking sequence of the composite laminates and placement of SCLs are used as design variables. Detailed numerical studies are presented. It is shown that optimum blade design yields significant increase in rotor lead-lag regressive modal damping compared to the initial system.
Hysteresis Modeling of Semi-Active Magnetorheological Helicopter Dampers
Authors: Wereley Norman M. , Kamath Gopalakrishna M. , Madhavan Vijay
Published: August 2002

MR dampers in soft-inplane rotors such as hingeless and bearingless rotors have potential benefits including semi-active control of aeromechanical instabilities, such as ground and air resonance. An experimental performance characterization of hybrid elastomeric/MR dampers for the 1/6th scale Comanche wind tunnel model rotor is presented. These dampers are similar to prior fluidelastomeric Comanche wind tunnel model dampers, except that the passive fluid is replaced by an MR fluid. MR lag dampers were tested under a compressive preload with the magnetic field turned on (ON condition) and off (OFF condition). Damping was characterized for single frequency sinusoidal excitation at the lag/rev (10 Hz) frequency; that is, the lightly damped inplane rotor blade bending mode that plays a dominant role in aeromechanical instabilities. Dual frequency testing was also carried out at 10 Hz and 15 Hz corresponding to the model rotor lag/rev and 1 /rev or rotor RPM frequencies respectively. In all of these tests, the force versus displacement hysteresis cycle or energy diagram was measured for the MR dampers. Two nonlinear models are compared: (1) a stiffness plus viscoelastic-plastic model, and (2) a stiffness-viscosity-elasto-slide model. These models were developed to capture the nonlinear behavior of these dampers. The model parameters were identified by minimizing the mean squared error between the predicted and measured MR damper force time histories due to a lag/rev harmonic excitation. Model validation for both single and dual frequency data was carried out. A key conclusion is that both models accurately predict damping performance, which suggests that the underlying hysteresis model is not unique when only damping is the performance metric.
Parameters Affecting the Migration of Molluscicidal Saponin from Styrene Butadiene Rubber Formulations Containing Phytolacca Dioica L.
Authors: Helaly F. M. , Ahmed A. A.
Published: August 2002

Discs of SBR containing Phytolacca dioica L. plant can be used to release saponin of the plant which has an efficient toxic effect on Bimpholaria alexandrine snails, the intermediate hosts of Schistosomiasis. Such a snail control system is used to protect the human beings from schistosomiasis. Schistosomiasis is a major health problem of increasing severity, especially in the developing countries. High abrasion furnace black (HAF) and hydrated silica (HISIL) are some inert fillers which improve the properties of rubber, and they play an important role in controlling the porosity of controlled release styrene butadiene rubber formulations containing Phytolacca dioica L. plant. Also, the leaching rate of saponin depends on the concentration of filler, type of water, temperature of the environment as well as surface to volume ratio of the discs. The scanning electron micrographs illustrate the cracks and pore structure which are formed after release of saponin. The leaching rate of saponin from SBR/HAF filled formulation is greater than the leaching rate from SBR/HISIL filled formulation.
Electric-Current Induced Crack Growth in Thin Films: Experimental Observations and Continuum Description
Authors: Bastawros Ashraf F. , Kim Kyung-Suk
Published: August 2002

Electric-current (EC) induced failure of pre-cracked, wide unpassivated interconnections is studied on a 0.2 mmthick, pure aluminum film. The film is deposited by high vacuum evaporation coating (HVEC) and patterned into test structures of varying widths. The specimens were electrically loaded to failure under EC via step, and slow or fast ramp loading. The EC induced failure was observed as localized crack growth or spread of a damage zone, depending on the rate of EC loading and the uncracked ligament width. Both crack and damage zone grew or spread towards the positive electrode. The experimental measurements of EC to failure showed a square root dependence on the uncracked ligament width, irrespective of the details of the failure mechanics. Based on this observation, the macroscopic critical current intensity factor is proposed to be used as the material property of the failure criterion, similar to the fracture toughness KIC for brittle fracture.
An Integrated Health Monitoring Technique Using Structural Impedance Sensors
Authors: Park Gyuhae , Cudney Harley H. , Inman Daniel J.
Published: August 2002

This paper presents an integrated methodology to detect and locate structural damage. Two different damage detection schemes are combined in this methodology, which involves utilizing the electromechanical coupling property of piezoelectric materials and tracking the changes in the frequency response function data, respectively. Physical changes in the structure cause changes in mechanical impedance. Due to the electromechanical coupling in piezoelectric materials, this change in structural mechanical impedance causes a change in the electrical impedance of the piezoelectric sensor. Hence, by monitoring the electrical impedance one can qualitatively determine when structural damage has occurred or is imminent. Based on the fact that damage produces local dynamic changes, this technique utilizes a high frequency structural excitation (typically greater than 30 kHz) through the surface-bonded piezoelectric sensor/actuators. As a second step, a newly developed model-based technique, using a wave propagation approach, has been used to quantitatively assess the state of structures. Direct frequency response function data, as opposed to modal data, are utilized to characterize the damage in the structures. A numerical example and an experimental investigation of one-dimensional structures are presented to illustrate the performance of this technique.
Appliance Foams with Reduced Levels of HFC-245fa
Authors: Doerge Herman P. , Schilling Steven L.
Published: August 2002

The HCFC-141b blowing agent used in most appliance foams in the United States is scheduled for phase-out on January 1, 2003. The most promising replacement is HFC-245fa. It has met many of the requirements for a blowing agent such as zero ozone depletion potential (ODP), low toxicity, good miscibility with polyols, low vapor phase thermal conductivity, and a reasonable boiling point of 59.5°F (15.3°C). Also, because it is non-flammable, HFC-245fa will save manufacturers of household refrigerated appliances the costs associated with retrofitting their factories to safely handle flammable blowing agents. However, refrigerator manufacturers have concerns about higher product manufacturing costs. Foam insulation costs may rise. New processing equipment and procedures may need to be installed in factories for new blowing agents. Refrigerator producers want to know if their foam operation productivity and product quality will be affected. They are also concerned about staying compliant with the 2001 Energy Consumption Standards. This paper will report on work done at Bayer Corporation to address these concerns. We will show the effect of lowering the level of HFC-245fa on foam thermal conductivity, physical properties and demold characteristics. Thermal stability and pressure generation studies on HFC-245fa containing masterbatches are presented which provide insight into handling the new generation formulations. The information presented will assist household refrigerator producers in selecting the most cost-effective solution to their manufacturing concerns when replacing HCFC-141b with HFC-245fa.
The Role of Neuroimaging in Development of and Treatment With Antipsychotics
Authors: Verhoeff Nicolaas P. L. G. , Kapur Shitij
Published: August 2002

This article addresses how neuroimaging can impact the development of and therapy with antipsychotics. The article explains how drug development, disease pathophysiology and neuroimaging approaches can be understood within a single neurobiological framework. It then highlights the relative strengths and applicability of the two streams of neuroimaging: neurochemical neuroimaging that reveals regional concentrations of particular neurochemical species (receptors, transporters or enzymes) and functional neuroimaging that reveals the effects of drug or disease on regional indices of neuronal function such as blood flow and oxygen and glucose metabolism. The application of these techniques is exemplified with recent examples from development and therapeutic use of antipsychotics. To assist decision making in the context of these imaging possibilities, the article presents an algorithm that can be used to guide decisions regarding the application of neuroimaging in the development of and treatment with antipsychotics.
Active Control of the Structural Intensity in Beams Using a Frequency-Domain Adaptive Method
Authors: Pereira Allan K. A. , Arruda José Roberto F. , Moreira Fernando J.O.
Published: August 2002

This paper presents an active control method which consists of minimizing the active part of the structural intensity aiming at reducing the overall vibration level in beams. The basic idea behind this strategy is that the control forces dissipate the input power due to the perturbing forces, thus preventing the structure from having to vibrate in order to dissipate the incoming energy. A frequency-domain adaptive structural intensity control method (ASIC) is used. The method is investigated using a simple example consisting of an aluminum beam which is fitted at one end with a quasi-anechoic termination (sandbox) and has the other end free. Numerically simulated and experimental results are presented. The numerical simulation uses a state-space model which was identified using experimental data. Results are compared with those obtained minimizing measured vibration directly, and with results using the instantaneous wave amplitudes as error signals in time-domain LMS control schemes. In the preliminary experimental results, the ASIC method and the method that controls the wave amplitudes outperformed one another at different frequencies. At frequencies where the power-flow-based methods performed well, their performance was equivalent to that of the direct control of vibrations. The relative advantages and disadvantages of the different control methods are discussed.
Note. Safranal Content in Spanish Saffron
Authors: Alonson G. L. , Salinas M. R. , Sánchez-Fernández M. A. , Garijo J.
Published: August 2002

Safranal is the compound mainly responsible for the aroma of saffron spice and can be used as a measure of saffron quality. It is described a “safranal value” of 269 (mostly Spanish) saffron samples by means of a spectrophotometric method based on ISO 3632 and the safranal content using a thermal desorption-gas chromatography method. The variation range of safranal was obtained from both methods, although there was no acceptable lineal correlation between them. Among all saffron samples the Spanish ones had the highest levels and those from Iran the lowest, which might be attributed to the different processes used for dehydrating the stigmas.
Fundamental Behavior of Piezoceramic Sheet Actuators
Authors: Sirohi Jayant , Chopra Inderjit
Published: August 2002

This paper investigates the behavior of piezoceramic sheet actuators under different types of excitation and mechanical loading. The research especially focuses on the application of these actuators to the development of smart rotor systems. The free strain response of the actuators under DC excitation is experimentally investigated along with the associated drift of the strain over time. Effect of tensile stress on the free strain response is examined. The magnitude and phase of the free strain response of the actuator under different excitation voltages and frequencies is measured, and a phenomenological model to predict this behavior is developed and validated. The power consumption of the free actuator and a pair of actuators surface bonded to a host structure is calculated by the impedance method and validated by measurement. Additionally, depoling of the actuators is discussed, along with the feasibility of recovering performance by repoling in the event of accidental depoling.
Studies on the Modification of Thermoplastic Polyolefins (TPOs). II. Effect of Processing Conditions on the Morphology and Adhesion of Two Components (2K) Polyurethane Coatings to the Modified TPOs
Authors: Hailat M. , Xiao H. X. , Frisch K. C. , Klempner D.
Published: August 2002

The morphology of thermoplastic polyolefins (TPOs) has a profound effect on their paintability. Paint molecules can penetrate an amorphous surface easier than a crystalline one. The effects of the compression molding processing conditions, such as molding temperature and cooling rate, on the crystallinity of TPOs were investigated. The effect of crystallinity on the adhesion properties of TPOs was evaluated using a two-component solvent-based polyurethane coating. The adhesion of the coating was better for the panels with less crystallinity. The compression molding temperature was found not to have a significant effect on the crystallinity of TPOs. The cooling rate was found to have a profound effect on the crystallinity and as a result on the paintability of modified TPOs.
Better Performing Dryable Insulation System for Low-Slope Roofs
Authors: Rudbeck Claus
Published: August 2002

Low-slope roofs are widely used but they are often vulnerable to water damage. As removal of water is difficult and expensive, low-slope roofs often have short service life and poor cost-performance ratio. To improve the durability of low-slope roofs, a dryable-on-demand roofing system has been proposed. The design, which includes a mechanism for moisture detection, was evaluated by means of numerical modeling and laboratory measurements.

Compared to traditional low-slope roofs, the suggested design offers several advantages including better cost-effectiveness, lower replacement costs, and lower use of resources. The paper shows that building envelope components that are prepared for repair and maintenance may be cost-effective.
Influence of Steroid Hormones on Bovine Pericardial Calcification
Authors: Vasudev Sindhu C. , Chandy Thomas , Sharma Chandra P.
Published: August 2002

Calcification is a frequent cause of the clinical failure of bioprosthetic heart valves fabricated from glutaraldehyde pretreated bovine pericardium (GABP). The present investigation describes the influence of steroid hormones in the mineralization of GABP, in an extra-circulatory environment. Calcification was studied on GABP incubation in a metastable solution of calcium phosphate containing steroid hormones such as estrone, progesterone, 7(OH) progesterone, testosterone and β-estradiol. It is interesting to note that certain steroids can variably increase the GABP calcification. Further, the effect of these steroids in an in vitro hydroxyapatite (HA) formation was investigated. In addition, we observed these steroids alter the calcium transport through GABP in diffusion experiments and also in HA formation. Therefore, it is conceivable that prolonged use of steroids or steroids containing oral contraceptive agents may not be advisable for patients having bioprosthetic implants in contact with blood. A better understanding of the mechanism of these drugs under in vivo conditions is needed to develop applications.
Determination of the Isothermal Moisture Transport Properties of Porous Building Materials
Authors: Carmeliet Jan , Roels Staf
Published: August 2002

A multiscale network approach is proposed as a practical method for estimating the isothermal permeability of porous building materials covering hygroscopic and overhygroscopic ranges. The multiscale approach is based on the concept of examining the porous space at different levels of magnification, and it allows modeling of combined liquid water and water vapor transfer over a wide saturation range. The proposed method simply requires the knowledge of common moisture properties, such as the capillary pressure curve, the capillary absorption coefficient and water vapor permeability, which can be determined from standard experiments. Hysteresis between drainage and wetting due to air entrapment can be adequately modeled by considering only those pores that become filled by water. The calculated network permeability is validated comparing experimental and simulation results of isothermal capillary absorption and drying processes in ceramic brick and calcium silicate. It is shown that transient moisture processes of capillary absorption from a dry sample and the isothermal drying from an initially capillary saturated sample can be accurately modeled by a single nonlinear permeability and capillary pressure curve. The capillary pressure curve to be used is the main wetting curve, which describes the moisture content relationship from the dry state to the capillary moisture content, correctly taking into account air entrapment phenomena. The description of the absorption or drying moisture processes by a single or a double exponential diffusivity relation was found to be less accurate.
Fatigue Damage Mechanism Characterization and Modeling of a Woven Graphite/Epoxy Composite
Authors: Naik Rajiv A. , Patel Sneha R. , Case Scott W.
Published: August 2002

A 5-harness satin woven graphite/epoxy composite was studied in both the as-fabricated and a hygrothermally aged condition. The fatigue damage mechanisms for both unaged and aged specimens were characterized using dynamic stiffness loss monitoring during fatigue loading. The major damage mechanisms of transverse yarn cracking, inter-yarn debonding, and delamination also were modeled using simple mechanistic models. It was possible to use the dynamic stiffness loss curves along with the simple damage mechanism models to characterize the evolution of transverse yarn cracking and delamination during fatigue, for both the as-fabricated and the aged specimens at room temperature (RT) and at 121°C (250°F). The present analysis predicted the trends in the matrix crack evolution and the delamination growth reasonably well. Based on the experiments and the analysis, the unaged material tested at RT and had the lowest rate of increase in the crack density with fatigue cycles. The unaged material tested at 121°C had the highest rate of crack density increase with cycles. Crack density for the 12,000 hour hygrothermally aged material increased at a rate of 95% higher than the unaged material tested at RT. Delaminations were computed to initiate at higher fatigue cycles and also reach higher delamination levels with decreasing cyclic stress levels. For the same stress level, elevated temperature and aging led to more rapidly increasing and larger delamination lengths. The hygrothermally aged material tested at 121°C had a very low threshold for delamination, which initiated below 1,000 cycles. The aged material tested at 121°C also had the largest delamination length. The models developed in this paper provide a simple means to derive information about fatigue damage mechanisms (which are often difficult to characterize), using stiffness loss measurements, which are quite easy to make.