bluuebunny/crossref_metadata_2025 huggingface dataset:
Ageing Human Bone: Factors Affecting its Biomechanical Properties and the Role of Collagen
Authors: Zioupos P.
Published: August 2002

The incidence of fractures increases with age. This is partly due to extraosseous factors and partly to the increased fragility of the bone material itself. Ageing adversely affects the “quality” of human bone material, its elastic and ultimate properties. The hypothesis here is that these effects are caused by factors such as architectural changes, compositional changes, physicochemical changes, changes at the micromechanical level, and the degree of prior in vivo microdamage. Examination of the extent of the secondary osteonal area, the porosity level, the calcium content, the mineral/wet weight fraction, the dry density, the condition of the collagen and its content in mature x-links, the elasticity of osteonal and interstitial lamellae at the microscopic level and the numericaland surface-density of the in vivo fatigue microcracks has been undertaken. The findings show that some factors simply affect the stiffness and the strength of bone, while others soley affect its toughness. We discuss the implications of these findings in the context of the composite nature of the ageing bone material matrix.
Dynamic Mechanical Properties of Natural Fiber-Reinforced Epoxy Foams
Authors: Bledzki Andrzej K. , Zhang Wenyang
Published: August 2002

In this work, the dynamic mechanical behavior of jute fiber-reinforced epoxy foams was investigated. The influence of various fiber and microvoid content on shear modulus, frequency and log decrement was discussed. Experimental results showed that the 42 vol.% fiber content significantly enhances the shear modulus. The shear modulus and frequency were decreased with increasing microvoid content in the epoxy matrix. The jute fiber as reinforcement affects the temperature of the log decrement peak. Increasing fiber and microvoid content induced a decrease and an increase of the log decrement peak values, respectively.
Review: Sources, Properties, Applications and Potential uses of Tannin Acyl Hydrolase
Authors: Aguilar C. N. , Gutierrez-Sanchez G.
Published: August 2002

Two critical factors, production costs and insufficient knowledge of the basic characteristics, physicochemical properties, catalytic characteristics, regulation mechanisms and potential uses, limit the use of tannase at the industrial level. Available literature on tannase are out-dated, scarce and confusing. This workreviews the state of the art of the critical aspects related to the tannase, emphasizing aspects such as sources, substrates, metabolic regulation mechanisms, physicochemical properties, inhibitors, production, applications and potential uses.
Effect of Ozone Treatment and Storage Temperature on Physicochemical Properties of Mushrooms (Agaris bisporus)
Authors: Escriche I. , Serra J. A. , Gómez M. , Galotto M. J.
Published: August 2002

The aim of this paper was to determine the effect of ozone, storage time and temperature on postharvest quality of mushroom ( Agaris bisporus var. Gurelan 55). Mushrooms, treated with ozone (100 mg/h) during 0, 15 or 25 minutes, were packed in polystyrene packs, overwrapped with PVC plastic film, and stored at 5, 15 or 25 °C for seven days. Internal and external lightness ( L*) texture properties, maturity index and weight loss were analyzed during storage. Ozone treatment on mushrooms prior to packaging caused an increase in external browning rate and a reduction of the internal browning rate. The ozone treatment exhibited no significant differences in terms of texture, maturity index and weight loss of mushrooms. Increased storage time and temperatures meant an increase in browning, senescence and weight loss, as well as a decrease in firmness, following, in all cases, a zero-order reaction kinetics. Temperature dependence of the reaction rates coule be described by Arrhenius equation. Among all the quality parameters assessed in this research, weight loss was the most affected by temperature increase ( Ea = 17.60 kcal/mol). The lowest storage temperature (5 °C) favored the best quality.
Thermoplastic Matrix Plates in Elasto-Plastic Finite Element Analysis
Authors: Arslan Nurettin , Çelik Mehmet
Published: August 2002

A two-dimensional finite element computer program is developed for elasto and elasto-plastic analysis. The analysis of the semicircular and “U” shaped edge notched plates manufactured from steel-thermoplastic composite is made under the uniform tension loads. Isoparametric quadrilateral element with four and nine nodes is used with Lagrange polynomial as an interpolation function. An initial stress method (modified Newton-Raphson) is used to determine elasto-plastic stresses in the finite element solution. Distribution of the plastic regions near the notch and variations of residual stresses are investigated in different orientation angles and loads for steel-thermoplastic composite plates with edge notches.
Effect of Principal Damage Plane Rotation on Anisotropic Damage Plastic Model
Authors: Chow C. L. , Yang X. J. , Chu Edmund
Published: August 2002

Under nonproportional loading, the principal planes of material, stress and damage are expected to differ, producing a hysteretic effect on the resulting design and failure analysis. This paper describes the development of an anisotropic damage model taking into account the effect of the principal damage plane rotation. All of the required mathematical formulations to generalize the damage model are derived in the principal damage coordinate system. Numerical procedures to include the changing damage planes are described in details. Two example cases of AL6111-T4 sheet material are provided to demonstrate the importance of the rotational effects of the principal planes on the resulting material behaviors under nonproportional loading.
A Constitutive Model for Elastic Damage in Fiber-Reinforced PMC Laminae
Authors: Barbero Ever J. , de Vivo Liliana
Published: August 2002

A practical methodology is presented for modeling the damaging behavior of fiber-reinforced, polymer-matrix composite laminae. It accounts for the basic mechanisms of degradation of properties under mechanical loading and incorporates this knowledge into a simple constitutive model in the framework of Continuum Damage Mechanics. A new expression for the damage surface is proposed, which reduces to the expression of the Tsai-Wu failure criterion in stress space. Model identification allows us to characterize the material through a small number of material parameters, all of which are related to material properties available in the literature. Available experimental results are used to illustrate the proposed methodology.
A Continuous Sensor to Measure Acoustic Waves in Plates
Authors: Sundaresan M. J. , Ghoshal A. , Martin W. N. , Schulz M. J.
Published: August 2002

An active fiber composite tape with segmented electrodes was modeled for use as a continuous sensor for structural health monitoring of plate structures. The material has unidirectional piezoceramic fibers with interdigital electrodes on the top and bottom surfaces and is poled in the fiber direction. The elastic response of a plate with the modeled sensor was computed in closed form at small time steps, and the coupled piezoceramic constitutive equations were solved. Wave propagation responses and the corresponding sensor voltages were computed in the simulations. The simulations indicate that the continuous sensor can detect damage to the plate based upon high frequency wave propagation characteristics. A continuous sensor comprised of monolithic piezoceramic patches was built and tested to measure simulated acoustic emissions on panel structures. The monolithic patches were used to simplify fabrication of the sensor. The sensor detected simulated acoustic emissions in a fiberglass panel using only one channel of data acquisition. The continuous sensor can potentially reduce the cost, complexity, number of channels of data acquisition, and the weight of monitoring instrumentation to a level where it becomes practical to perform health monitoring on large structures.
Pin Reinforcement of Delaminated Sandwich Beams Under Axial Compression
Authors: Wallace Brian T. , Sankar Bhavani V. , Ifju Peter G.
Published: August 2002

The present study is concerned with translaminar reinforcements in a sandwich beam for preventing buckling of the delaminated face sheet under edge-wise axial compression. Sandwich beams consisting of graphite/epoxy face sheets and an aramid honeycomb core were reinforced in the thickness direction using two techniques: Z-pinning using graphite/epoxy pins and a novel “C-pinning technique” developed by the authors. To evaluate the effect of reinforcement type and reinforcement spacing on the ultimate compressive strength of delaminated beams, compression tests were performed. Critical buckling loads and post-buckling behavior of sandwich beams under axial compression were evaluated by finite element analysis to provide insight into the effectiveness of translaminar reinforcement. Pin reinforcement has been shown to significantly improve the ultimate compressive load of a delaminated sandwich beam.
Influence of Crush Mechanisms on Energy Absorption of PMC Square Tubes
Authors: Abdel-Haq M. , Newaz G. M.
Published: August 2002

An experimental investigation was carried out to correlate the crushing response of square unidirectional polymeric composite tubes with the associated major failure modes in the crushing process. The failure modes of interest included axial splitting, transverse cracking, and delamination. The effect of using external constraints on the crushing performance and energy absorption capability of square tubes was also analyzed. The tubes used in the tests were unidirectional fiber-glass/polyester and fiber-glass/vinyl ester tubes. Tests were performed for flat crushing and using initiators with a 12-mm radius. The results showed that the external constraint can significantly affect the major failure modes in the crushing process, leading to considerable improvement in the specific energy absorption (SEA) of the tubes.
Impact Performance of Macrocomposite Laminates-1. Evaluation of Energy Absorbed in Non-Penetration Impact Test
Authors: Akimoto H. , Toda M. , Miyashita J. , Shonaike G. O. , Murakami A. , Hogg P. J. , Ahmadnia A.
Published: August 2002

Cladding of dissimilar materials is one of the several methods for improving the mechanical properties of composite materials. In this investigation, low impact energy test (non-penetration test) was carried out on GFRP/metal composites. The behavior at three energy levels (4, 8, and 12 J) was studied. The samples were divided into three types: Type 1 consisting of GFRP, Type 2 is GFRP with stainless steel (not bonded) and Type 3 is GFRP bonded to stainless steel. The GFRP contains chopped strand mat (CSM), biaxial system (BX) and quasiaxial system (QX). Both force at the initial peak (Fi) and maximum force (Fmax) increased due to the presence of stainless steel in the composite. However, Fmis increases with respect to impact energy whilst Fi was independent of impact energy. A slight improvement on the energy absorption of GFRP layer in the macrocomposite system was achieved at all energy levels except for CSM-GFRP which shows a significant brittle failure.
A Unified Micromechanical Model for the Mechanical Properties of Two Constituent Composite Materials Part II: Plastic Behavior
Authors: Huang Zheng-Ming
Published: August 2002

This series of papers reports a new, general, and unified micromechanical model for estimating the three-dimensional mechanical properties of a composite made from two isotropic constituent materials, i.e., continuous fiber and matrix. The present paper concentrates on the plastic behavior of the composite. Based on a perfect bonding assumption for the fiber and matrix interface during the entire elastic-plastic deformation range under consideration, a bridging relationship connecting the internal stresses generated in the matrix with those in the fiber is dependent only on the constituent geometric and material properties. Thus, the bridging matrix used in Reference [1] for elastic deformation analysis is modified according to the changed material properties of the constituents to account for their plastic deformation effect. With this matrix, the internal stress increments in each constituent material at every load level are explicitly related to the overall stress increments on the composite. The overall instantaneous compliance matrix of the composite follows easily once the constituent compliance matrices have been defined using any existing plastic flow theory of isotropic materials. Such an instantaneous compliance matrix will be of crucial importance in failure analysis of laminated composites. Incorporation of the Prandtl-Reuss flow relations with the explicit formulae proposed for the bridging matrix in Reference [L] has been described in the present paper. Good correlation has been found between predicted and available experimental elastic-plastic stress-strain curves of several unidirectional fibrous composites subjected to both uniaxial and combined load conditions.
Radionuclide Imaging in Parkinson’s Disease: Diagnosis, Treatment, and Disease Progression
Authors: Doudet Doris J.
Published: August 2002

This paper reviews the abilities of positron emission tomography (PET) and single photon emission tomography (SPECT) to detect Parkinson’s disease, monitor its progression and the effect of therapy. It also provides insights on the role these two modalities provide in terms of discriminating atypical syndromes from Parkinson’s disease. Both PET and SPECT are sensitive means of detecting alterations in metabolism and blood flow in the brain and impairments in neurotransmitter function, especially dopaminergic, in the striatum and, more recently, in extrastriatal structures. To date, PET presents the added advantage of quantification, better sensitivity and resolution and a greater variety of tracers for both the dopaminergic and nondopaminergic systems.
Prepreg Treatment with Ar+ Ion Irradiation to Improve GIcof Unidirectional Graphite/Epoxy Laminated Composites
Authors: Rhee Kyong Y. , Choi Nak-Sam , Han Young G. , Koh Seok K.
Published: August 2002

Currently, many methods are used to improve the fracture toughness of graphite/epoxy composites. However, no work has been done on the prepreg treatment with Ar+ ion irradiation. In the present work, the effect of surface treatment of prepreg by Ar+ ion irradiation on the delamination resistance of unidirectional graphite/epoxy laminated compositeswas studied. The surface of the prepregwas treated with Ar+ ion irradiation under oxygen environment, and the change of contact angle with surface-treatment was measured. Two kinds of [06//06] DCB (double cantilever beam) specimens were made: (1) DCB specimens made of graphite/epoxy prepregs that had been surface-treated with Ar+ ion irradiation under oxygen environment (Laminate A) and (2) DCBspecimens made of regular, untreated graphite/epoxy prepregs (Laminate B). The delamination resistance curve of Laminate A was compared with that of Laminate B so that the effect of prepreg treatment on the resistance behavior could be determined.
The Influence of Photodynamic Therapy on the Wound Healing Process in Rats
Authors: Jayasree R. S. , Gupta A. K. , Rathinam K. , Mohanan P. V. , Mohanty M.
Published: August 2002

In photodynamic therapy (PDT), photosensitisers (PS) are used along with lasers for the treatment of tumors. The combined effect of photosensitisers and lasers on the wound healing process is studied using δ-aminolevulinic acid (ALA) (5 mg/kg) and hematoporphyrin derivative (HPD) (5 mg/kg) as photosensitisers in the open excision wounds of rats. The lasers used were He-Ne laser (3 J/cm2) and Nd: YAG laser (30 J/cm2). This study is important for understanding the healing process involved after PDT. Open excision wounds treated with He-Ne lasers in animals that received ALA as photosensitiser showed complete wound closure at the earliest by 13 ± 1 days, and with results obtained for HPD and the combination of lasers with complete closing by 14 ± 1 days. However, the control group of animals that received ALS or HPD with no laser treatment showed wound healing on the twentieth and eighteenth days with a deviation of one day and two days, respectively. ALA with the combination of Nd: YAG and He-Ne lasers and HPD with He-Ne laser alone does not show quicker wound healing effects. Histopathological results also gave similar results. Tensile strength measurements do not vary significantly from control group to the test group.

ALA along with He-Ne laser of HPD along with the combination of He-Ne and low power Nd-YAG lasers are found to be ideal methods for quickening the wound healing process in rat.
Venting of Attics and Pitched, Insulated Roofs
Authors: Blom Peter
Published: August 2002

This paper discusses venting of roof constructions in single-family houses. In Norway, roof venting is considered to be crucial in order to prevent ice formation at the eaves and remove excess moisture. This paper is based on temperature and moisture measurements in a test roof with 12 segments, each with a different roof construction. Additional measurements are made in two attics in inhabited dwellings. A computer program has been developed to simulate the temperature conditions in the test roof.

The paper concludes that venting of roof constructions should not be neglected in modern roofing systems in Norway. However, the paper points out that thermal insulation and continuous wind/vapour barriers in the roof are key factors in preventing ice formation.
Metal Powder-Filled Polyethylene Composites. V. Thermal Properties
Authors: Sofian N. M. , Rusu M. , Neagu R. , Neagu E.
Published: August 2002

Thermal properties—such as thermal conductivity, thermal diffusivity, and specific heat—of metal (copper, zinc, iron, and bronze) powder-filled high-density polyethylene composites are investigated experimentally in the range of filler content 0-24% by volume. Experimental results show a region of low particle content, 0-16% by volume, where the particles are distributed homogeneously in the polymer matrix and do not interact with each other. In this region most of the thermal conductivity models for two-phase systems are applicable. At higher particle content, the filler tends to form agglomerates and conductive chains resulting in a rapid increase in thermal conductivity.
Characterization of Piezoelectric Wafer Active Sensors
Authors: Giurgiutiu Victor , Zagrai Andrei N.
Published: August 2002

In the beginning, the classical one-dimensional analysis of piezoelectric active sensors is reviewed. The complete derivation for a free-free sensor is then extended to cover the cases of clamped and elastically constrained sensors. An analytical model based on structural vibration theory and theory of piezoelectricity was developed and used to predict the electromechanical (E/M) impedance response, as it would be measured at the piezoelectric active sensor’s terminals. The model considers one-dimensional structures and accounts for both axial and flexural vibrations. The numerical analysis was performed and supported by experimental results. Experiments were conducted on simple beam specimens to support the theoretical investigation, and on thin gauge aluminum plates to illustrate the method’s potential. It was shown that E/M impedance spectrum recorded by the piezoelectric active sensor accurately represents the mechanical response of a structure. It was further proved that the response of the structure is not modified by the presence of the sensor, thus validating the sensor’s non-invasive characteristics. The sensor calibration procedure is outlined and statistical analysis was presented. It was found that PZT active sensors have stable and repeatable characteristics not only in as-received condition, but also while mounted on 1-D or 2-D host structure. It is shown that such sensors, of negligible mass, can be permanently applied to the structure creating a non-intrusive sensor array adequate for on-line automatic structural identification and health monitoring.
Quantitative Study of Surface Relief Produced by Martensitic Transformation in Fe-Mn-Si-Cr Shape Memory Alloy Using Atomic Force Microscopy
Authors: Liu D. Z. , Kikuchi T. , Kajiwara S. , Shinya N.
Published: August 2002

Surface relief produced by stress-induced martensitic transformation in Fe28Mn-6Si-5Cr (mass%) shape memory alloy has been observed using atomic force microscopy (AFM). The surface relief of martensites with a preferential orientation and multi-orientations has been analyzed qualitatively and quantitatively. When the martensites are produced along a preferential orientation, i.e., on one of four {111} shear planes in FCC structure, they are formed with the socalled "mono-partial" stacking nature, i.e., only a single variant of martensite is activated. For the case when multi-oriented martensites are produced, the relation between the observed martensite plates and the corresponding motion of a<,/6(112(Shockley partial dislocations have been obtained. The result indicates that only a single variant on each {111} close-packed plane is activated even in such a case. In addition, in some cases, very thin deformation twin plates (1OOnm) and heavily deformed slip bands are observed in the regions of intersection between martensites and they are one of main reasons to produce incomplete shape memory effect in Fe-Mn-Si based shape memory alloys.
Micromechanical Modeling of Polymer Modified Asphalt at Low Temperatures
Authors: Li Guoqiang , Pang Su-Seng , Zhao Yi
Published: August 2002

Polymer modified asphalt (PMA) is treated as a two-phase composite material with polymer particles dispersed in an asphalt matrix. Christensen and Lo's three-phase sphere model is thus extended to a two-layer built-in model to evaluate parameters affecting the low temperature cracking resistance of a PMA mixture. A distinctive characteristic of the proposed model is that it can consider the effect of the PMA layer thickness on the mechanical properties when a PMA is used in an asphalt pavement. In addition, it can consider the effect of the polymer particle size distributions on the mechanical properties of the PMA. Approaches which are beneficial to enhance the low temperature cracking resistance of a PMA mixture are suggested based on the calculated results.
Analytical and Experimental Investigations on the Transient Heat Transfer Process in Moist Wood Wool Slabs
Authors: Baggio Paolo , Campanale Manuela , Moro Lorenzo
Published: August 2002

Heat and moisture transfer in wood wool slabs (shredded wood with Portland cement binder) has been investigated both experimentally and theoretically. The purpose of this study is the analysis of the process of moisture redistribution taking place inside wood wool slabs conditioned to moisture equilibrium (e.g., in a climatic chamber) and then mounted in a guarded hot plate or heat flux meter apparatus to measure the specimen thermal resistance. A theoretical analysis of the heat and mass transfer process for such a material was performed and then a suitable numerical model was used to predict and analyse the moisture redistribution. The porous media may be modelled as a multiphase system constituted by a solid matrix and a network of interconnected pores, partly filled with liquid water and partly with moist air. Three equations have been derived: conservation of the mass of the dry air, the conservation of the mass of water species (liquid and vapour) and the energy balance. These equations have been supplemented with the thermodynamic relations and the constitutive equations needed for the closure of the model. The experimental work was performed on a slab cut into several slices. During the experimental tests, the temperature and heat flow rate data was collected both during the steady state conditions to get the thermal resistance and during the initial transient period, when the heat flow rate is continuously varying. At the end of the test, the slices were weighed to get information on the moisture redistribution. The moisture data versus heat flow rate and temperature on the two faces of the specimen, and information about the final moisture distribution were compared with those obtained by numerical simulation. Substantial agreement between numerical result and experimental data was found.
Clinical Considerations in the Use of Inhalation Delivery Devices
Authors: Brock Tina Penick , Williams Dennis M.
Published: August 2002

Medications delivered through oral inhalation represent the cornerstone of pharmacotherapy for asthma and chronic obstructive pulmonary diseases. Several options exist as methods of delivering aerosols to the lung, including metered-dose inhalers, metered-dose inhalers attached to spacers or valved holding chambers, dry powder inhalers, and nebulizers. Delivery of aerosols to the lung is affected by numerous factors including characteristics of aerosol particles, patients’ ventilatory patterns, and physical condition of the lung. It has become increasingly clear that the device used to deliver the medication is an important factor in the extent of deposition and the ultimate therapeutic effect. Further, the same therapeutic agent may exhibit differing effects depending on which delivery device is used. Each inhalation device has specific instructions for use, and the techniques for use vary significantly among the available products. In each case, patients should be instructed and observed to ensure that they have the proper technique of use to achieve an optimal effect.
The Potential of Rubberwood as a Filler in Epoxidized Natural Rubber Compounds
Authors: Ismail Hanafi
Published: August 2002

The effect of rubberwood on curing characteristics and mechanical properties of epoxidized natural rubber (ENR) was investigated in the loading range of 0 to 50 phr. Results indicate that the scorch and cure times decrease with increasing rubberwood loading. Tensile modulus and hardness of the composites increase with increasing rubberwood loading whereas tensile strength and tear strength show a decrease. SEM studies and rubber-rubberwood adhesion measurements indicate that the increasing rubberwood loading has weakened the rubber-rubberwood interactions.
On the Elastic Stiffnesses of Corrugated Core Sandwich
Authors: Carlsson Leif A. , Nordstrand Tomas , Westerlind Bo
Published: August 2002

The objective of this paper is to review and recast previous analytical approaches to the analysis of the elastic stiffnesses of corrugated core sandwich panels into the framework of first-order shear deformation laminated plate theory. Extensional, shear and bending stiffnesses will be determined and compared to measured data. It is shown that the in-plane extensional and shear stiffness and the bending and twisting stiffnesses are dominated by the face sheets and that calculated values agree with measured data. Transverse shear stiffnesses, however, are highly dependent on the integrity and shape of the core and the details of face-to-core bonding, and predictions were found to be highly unconservative. A major factor for the reduction in stiffnesses of the core is attributed to delamination damage of the web inflicted during the corrugation process.
Transverse Stitched T-Joints in Bending with PR520 Resin: Initial Results
Authors: Stickler P. B. , Ramulu M. , van West B. P.
Published: August 2002

An experimental investigation was undertaken to evaluate the bending strength of transversely stitched T-joints using fiber insertion as the primary load transfer mechanism and using resin transfer molding with PR520 toughened epoxy resin. Tests were conducted to determine the ultimate bending strength of two joint configurations and fractographic examination was performed to determine joint failure mechanisms. This study shows that increasing the web thickness and the subsequent number of rows of stitching has the effect of increasing the initial and maximum bending strength of the T-joint design. As indicated by the fractographic examination, initial joint failure occurs by matrix cracking initiating at the resin rich corner fillet and propagates inward toward the transverse stitching; and ultimate joint failure occurs by fiber breakage and/or fiber pullout.
Characterization of 0.9PMN-0.1PT Patches for Active Vibration Control of Plate Host Structures
Authors: Pablo F. , Petitjean B.
Published: August 2002

Current applications in active vibration control mainly use piezoceramic actuators (PZT). With the aim of improving vibration absorption, electrostrictive actuators have been elaborated. These electrostrictive ceramics show very attractive properties for active vibration control applications. Yet, their non-linear electromechanical behavior tempers these numerous advantages and considerably complicates their use. In usual active vibration control applications, dynamic electric fields with varying magnitudes and frequencies are applied to the ceramic. Earlier measurements, performed at ONERA, showed that the ceramic behavior is strongly sensitive to operating parameters (electric field magnitude, excitation frequency, and surrounding temperature). It is demontrated in this paper that this sensitivity can be reduced to a sensitivity of the material to its own temperature. Indeed, a significant heating of electrostrictive ceramics occurs when they are subjected to a variable electric field. This heating turns out to be, itself, dependent on operating parameters. An experimental electric model of stress-free electrostrictive patches is here presented, taking into account this thermal phenomena. This model is then used to develop constitutive relations for these materials with the view of using them as actuators in active vibration control of thin plate structures.
Note. Consumer Awareness of the Main Sensory Attributes of Tepache, a Traditional Fermented Fruit Beverage
Authors: Moreno-Terrazas R. , Reyes-Morales H. , Huerta-Ochoa S. , Guerrero-Legarreta I. , Vernon-Carter E. J.
Published: August 2002

Four tepache samples (a traditional fermented fruit beverage) from four different sources obtained by different fermentation processes were sensory evaluated. A paired comparison test between the samples was carried out in a monadic sequential fashion in six sessions with 70 consumers each. A sample processed by double fermentation received the highest mean scores for the first impression and overall acceptance and in the sensory attributes of appearance, consistency, odor, flavor and sweetness/sourness ratio. Principal component analysis indicated that appearance, odor, flavor, first impression and overall acceptance are highly intercorrelated. That sample was also the most preferred beverage in the comparative test. Flavor intensity was significantly different in all of the paired comparisons. No significant differences were found in the overall acceptance evaluations between genders. A fairly good correlation was found between overall acceptance and consumers who drank the beverage once a week.
Mapping of Air Leakage in Exterior Wall Assemblies
Authors: Desmarais Guylaine , Derome Dominique , Fazio Paul
Published: August 2002

A full-scale wood frame test hut with nine wall specimens, typical of low-rise residential construction in the province of Quebec, was built inside an environmental chamber. This test hut was subjected to 66 days of simulated winter and 47 days of late spring climatic conditions to verify the feasibility of different methods of mapping and representing graphically air exfiltration. Through a better understanding of the movement of air through the envelope, the risks related to moisture condensation within the envelope for different wall compositions can be better ascertained. The air leakage pattern characterization methods implemented were two-dimensional grid moisture content monitoring and three-dimensional grid temperature monitoring. The moisture content and temperature data were presented in a graphic form, using isohygrons and isotherms. Temperatures without the impact of air leakage were also calculated using a three-dimensional conductive heat transfer model. The air leakage pattern characterization methods and the resulting moisture and temperature maps are presented and discussed herein.
Neuroimaging in Drug Discovery and Development: Paradigms for Accelerating New Drug Availability
Authors: Metz John T. , Cooper Malcolm D. , Brown Terry F. , Kinnunen Leann H. , Cooper Declan J.
Published: August 2002

The process of discovering and developing new drugs is complicated. Neuroimaging methods can facilitate this process. An analysis of the conceptual bases and practical limitations of different neuroimaging modalities reveals that each technique can best address different kinds of questions. Radioligand studies are well suited to preclinical and Phase II questions when a compound is known or suspected to affect well-understood mechanisms; they are also useful in Phase IV to characterize effective agents. Cerebral blood flow studies can be extremely useful in evaluating the effects of a drug on psychological tasks (mostly in Phase IV). Glucose metabolism studies can answer the simplest questions about whether a compound affects the brain, where, and how much. Such studies are most useful in confirming central effects (preclinical and early clinical phases), in determining effective dose ranges (Phase II), and in comparing different drugs (Phase IV).
Smart Flexible Microrobots for Scanning Electron Microscope (SEM) Applications
Authors: Schmoeckel Ferdinand , Fatikow Sergej
Published: August 2002

In the scanning electron microscope (SEM), specially designed microrobots can act as a flexible assembly facility for hybrid microsystems, as probing devices for in-situ tests on IC structures or just as a helpful teleoperated tool for the SEM operator when examining samples. Several flexible microrobots of this kind have been developed and tested. Driven by piezoactuators, these few cubic centimeters small mobile robots can perform manipulations with a precision of up to 10 nm and transport the gripped objects at speeds of up to 30 mm/s. In accuracy, flexibility and price they are superior to conventional precision robots. A new SEM-suited microrobot prototype is described in this paper. The SEM’s vacuum chamber has been equipped with various elements like flanges and CCD cameras to enable the robot to operate. In order to use the SEM image for the automatic real-time control of the robots, the SEM’s electron beam is actively controlled by a PC. The latter submits the images to the robots’ control computer system. For obtaining three-dimensional information in real time, especially for the closed-loop control of a robot endeffector, e.g., microgripper, a triangulation method with the luminescent spot of the SEM’s electron beam is being investigated.
The Influence of Cross-Link Density on the Creep Compliance of an Advanced Polyimide
Authors: Nicholson Lee M. , Gates Thomas S.
Published: August 2002

The effect of cross-link density on the visco-elastic performance of an advanced polymer matrix (LaRC™-PETI-SI) was investigated through creep compliance tests. Testing consisted of short-term isothermal creep and recovery with the creep segments performed under constant load. The tests were conducted at three temperatures below the glass transition temperature of each material with different cross-link density. Through the use of time-aging-time superposition procedures, the material constants, material master curves and aging-related parameters were evaluated at each temperature for a given cross-link density. It was shown that the high cross-link density materials have increased creep compliance and creep compliance rate, and are less sensitive to physical aging than the low cross-link density materials. The temperature sensitivity of the time-temperature superposition (TTSP) shift factor was shown to increase monotonically with increasing cross-link density. Furthermore, at the highest temperature, a separation in the TTSP shift factors was apparent between different cross-link densities. This separation occurred at a molecular weight ( Mc) of ~3321 g/mol.
Weight Minimization of Sandwich Panels with Acoustic and Mechanical Constraints
Authors: Wennhage Per
Published: August 2002

If a structure is carefully designed to fulfill acoustic as well as strength and stiffness requirements, the amount of additional damping materials can be kept to a minimum. In the present work a method to minimize the mass per unit area of a sandwich panel, taking into account both structural and acoustic requirements is presented. The sound reduction index for airborne sound is used as a constraint and the optimization is performed by mathematical programming methods. As an example a standard solution for sandwich plates is used to define maximum deflection and stresses as structural constraints.
Influence of Composition and Dopant on Photostriction in Lanthanum-Modified Lead Zirconate Titanate Ceramics
Authors: Poosanaas P. , Tonooka K. , Abothu I. R. , Komarneni S. , Uchino K.
Published: August 2002

The anomalous photovoltaic effect, i.e., substantial voltage generation exceeding band gap energies, by homogeneous illumination in the non-centrosymmetric materials is a wellknown phenomenon. This mechanism is fundamentally different from those observed in heterojunctions/homojunctions (i.e., solar cells) based on semiconductor materials with a symmetric crystal structure. Recently, light induced strain termed as Photostriction, has been demonstrated in noncentrosymmetric perovskite ferroelectrics as lanthanum-modified lead zirconate titanate (PLZT) ceramics. PLZT ceramics have gained considerable attention due to their large photostrictive responses. When a light is illuminated on a polarized photostrictive bimorph, a large photovoltage of the order of kV/mm is generated across its length in the spontaneous polarization direction which results in strain generation by converse-piezoelectric effect and caused the bimorph to deflect in the direction away from the illumination. The photoactuation has been demonstrated in PLZT ceramic wafers as two different kinds of actuators, (i) photo-driven relay and (ii) photo-driven micro walking machine. These materials are also promising for the photo-acoustic device (e.g., Photophone) of the optical communication system. However, photostriction being a recently observed phenomenon, is far from optimum condition. It is expected that the optimization with respect to materials and microstructural characteristics will lead to a substantial enhancement in the photoactuation efficiency. Increasing the photoactuation efficiency will eliminate the need for electrical energy, and will open up numerous possibilities of contactless actuators. In this paper the influence of composition dependence and impurity doping effects on microstructure and photostrictive responses of PLZT ceramics have been investigated.
Experimental Evaluation of Airflow in Naturally Ventilated Active Envelopes
Authors: Saelens Dirk , Hens Hugo
Published: August 2002

Active envelopes are characterised by two glazed surfaces separated by a ventilated cavity in which a shading device is placed. Thermal performance of active envelopes is governed by the airflow through the cavity. Until now, there is a lack of knowledge about the amplitude and direction of the airflow in naturally ventilated active envelopes. In this paper we report on the airflow in the naturally ventilated active envelope at the Vliet building of the Laboratory of Building Physics in Leuven, Belgium. (1) The airflow was experimentally determined by measuring the pressure difference over a ventilation grid. This method shows several advantages over traditional methods. (2) Thermal buoyancy and wind pressure differences govern the airflow. For both phenomena, measured data were compared with models. It was found that at low windspeeds and upward flow conditions, a linear relation between the pressure and temperature difference could be obtained. For higher windspeeds simple models cannot accurately predict the complexity of the airflow in naturally ventilated active envelopes due to the location of the measurement probes and due to wind washing effects imposed by altering wind directions.
Optoelectrical Properties of Poly(Ethylene Oxide)/Alum Composite
Authors: Ramadin Y. , Saq'an S. , Eid A. , Ahmad M. , Zihlif A.
Published: August 2002

The optical and electrical characteristics of prepared poly(ethylene oxide)/alum composites are studied as a function of alum content and frequency. The optical energy band gaps were determined from the measured absorption spectra. The frequency of the applied electric field and alum content affect the dielectric behavior and the AC electrical conductivity of the prepared solid thin films. Correlation between the observed optical energy gaps and the AC electrical conductivity is presented. Generally, the observed enhancement in the electrical quantities is attributed to impurity, and ionic interactions take place in the bulk of the double electrolyte solid solution.
A Damage-Coupled TMF Constitutive Model for Solder Alloy
Authors: Wei Yong , Chow C. L.
Published: August 2002

This paper presents the development of a damage-coupled constitutive model to characterize the mechanical behavior of 63Sn-37Pb solder material under thermo-mechanical fatigue (TMF) loading. Based on the theory of damage mechanics, two internal state variables, known as the damage parameters, are introduced to characterize material degradation due to the change of material microstructures under load. Then, a damage effect tensor is proposed to define the effective stress for a damaged material. In general, there are two different kinds of damage accumulation depending upon the mode of loading: inelastic damage and fatigue damage. With the aid of irreversible thermodynamics, the damage evolution equations are established. A failure criterion is proposed based on the equivalent damage accumulation in materials. A test program to determine the material parameters is also presented.

The damage model is implemented in a finite element program ABAQUS through its user-defined material subroutine UMAT. The model is applied to predict the behavior for 63Sn-37Pb solder alloy under monotonic tensile loading, load-controlled tensile creep loading and strain-controlled fatigue loading. The behavior of a notched specimen under monotonic tensile loading is also examined. The predicted failure mode and maximum load agree well with those measured experimentally.
The Thermal Conductivity of a Polyethylene Foam Block Produced by a Compression Molding Process
Authors: MartÍnez-DÍez J. A. , RodrÍguez-PÉRez M. A. , De Saja J. A. , Arcos Y RÁbago L. O. , Almanza O. A.
Published: August 2002

The thermal conductivity of 10 mm thick low density polyethylene foam sheets cut from a block produced by a compression molding process has been studied in the temperature range between 24°C and 50°C. The cellular structure and the matrix polymer morphology have also been characterized to find out the main microscopic characteristics that influence on the foam properties. A previously developed theoretical model has been applied to compute the thermal conductivity of the foams under study. This model was successful in the considered temperature range. Moreover, the evolution of the thermal conductivity along the thickness of the foam block has also been considered and explained in terms of the structure of the materials.
Gravity Effects on Fluid Front Dynamics during Mold Filling
Authors: Olivero K. A. , Altan M. C.
Published: August 2002

The effect of gravity on free surface shape during the filling of a disk-shaped cavity is experimentally studied. A disk-shaped mold cavity is constructed to measure spreading of the fluid front due to gravity. Fluid front sensors are mounted on the top and bottom mold walls at three radial locations. The time the fluid front reaches these sensor locations is recorded. This data is used to calculate the radial distance between the top and bottom of the fluid front at each sensor location. The important parameters that govern the fluid front dynamics are identified as the Reynolds, Bond, and Capillary numbers. Spreading is found to be mainly dependent on the Bond number, such that a large change in spreading is observed due to a small change in Bond number. Spreading increases with decreasing Capillary number and remains nearly constant over the range of Reynolds numbers studied.
Curing and Mechanical Properties of Nitrile and Natural Rubber Blends
Authors: Ismail Hanafi , Tan S. , Poh B. T.
Published: August 2002

The curing and mechanical properties of nitrile (NBR) and natural rubber (NR) blends were carried out. Two series of blends were prepared, i.e., NBR/SMR L and NBR/ENR 50 blends. Blends were prepared using a Brabender at a temperature of 60°C. Results indicate that the scorch time, t2 and cure time, t90 increase with increasing NBR content in both blends. In NBR/ENR 50 blends the increasing content of NBR increases the maximum elastic torque, torque difference, tan δ @ MH and viscous torque. However, in NBR/SMR L blends the opposite trend is observed for maximum elastic torque and torque difference. In both blends modulus at 100% elongation (M100) and at 300% elongation (M300) increases with increasing NBR content, whereas tensile strength and elongation at break show a decreasing trend.
Quality Assessment of Heparin Coatings by their Binding Capacities of Coagulation and Complement Enzymes
Authors: Weber N. , Wendel H. P. , Ziemer G.
Published: August 2002

In vitro testing of blood contacting materials before clinical application is generally advisable. Four heparin coatings from different manufacturers were tested for adsorbed proteins and soluble activation markers. The surface with the highest antithrombin, thrombin, high-molecular-weight-kininogen (HMWK) and the lowest fibrinogen binding capacity (Carmeda, Medtronic) showed significantly lower levels of granulocytes and platelet activation (β-TG, PMN-elastase release). No statistically significant differences in soluble markers of the coagulation system could be detected (F1+2, TAT). Interestingly, complement activation (TCC) was significantly reduced within the group of the lowest adsorption of the complement factor C3.

Our data demonstrate that there is a relation between the binding affinity of proteins (C1-inhibitor, C3-complement) and the consecutive changes in complement activation (TCC). Therefore, measuring adsorbed proteins on artificial surfaces is a suitable, sensitive and very reproducible method for assessing the thrombogenicity of biomaterials.
Investigations of the Processing-Structure-Property Relationships of Isotactic Poly(4-Methyl-1-Pentene) Tubular Extruded Films
Authors: Johnson Matthew B. , Wilkes Garth L.
Published: August 2002

An investigation was undertaken of the processing-structure-property relationships of two linear poly(4-methyl-1-pentene) resins (PMP) which differed in molecular weight( Mw). This was done by characterizing tubular films (BUR = 1) extruded at two processing conditions, with specific attention being focused upon the morphological results and the crystal orientation as a function of Mw. Carreau-Yasuda analysis of oscillatory shear data was utilized to evaluate the melt-flow behavior of the two resins. Atomic force microscopy and wide-angle X-ray scattering were utilized to study the morphology of the final films, which was shown to be a stacked lamellar structure for both resins. The Mw and melt-extrusion conditions affected the orientation state and the nature of the stacking, planar or twisted. It was concluded that both extrusion stress and the relaxation behavior of the polymer melt are critical in determining the orientation/structural features of the extruded PMP films.