bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Linear Matrix Inequalities in the Control of Smart Structural Systems
Authors: Sana Sridhar , Rao Vittal S.
Published: August 2002

Natural frequency variations, unmodeled dynamics and control input constraints are some of the major problems in the design of controllers in smart structural systems. The performance and robustness of the closed-loop system are often constrained by the limited actuation force available from Lead Zirconate Titanate (PZT) actuators. Hence, it is desirable to design controllers to maximize the performance and robustness without violating the control input constraints. In this paper, we give a methodology for designing output feedback robust controllers for smart structural systems using Linear Matrix Inequalities (LMIs). A procedure is developed to incorporate the real parameter uncertainty resulting from natural frequency variations and complex uncertainty due to unmodeled dynamics in a Linear Fractional Representation (LFR) to be utilized in the design. The control input constraints are satisfied by finding an invariant ellipsoid of closed loop trajectories for a given set of initial condition disturbances. An iterative procedure is given to solve the optimization problem involving Bilinear Matrix Inequalities (BLMIs). The design procedure is applied on a smart structural test article and the effectiveness of the proposed method is verified by robustness analyses and experimental tests.
Processing and Performance of Continuous Fiber Ceramic Composites by Preceramic Polymer Pyrolysis: II—Resin Transfer Molding
Authors: Ghasemi Nejhad Mehrdad N. , Bayliss Jocelyn K. , Yousefpour Ali
Published: August 2002

Vacuum Assisted Resin Transfer Molding (VARTM) was used in conjunction with preceramic polymer pyrolysis to manufacture Continuous Fiber Ceramic Composites (CFCCs). Two VARTM techniques were used: (a) the use of injection pressure in the presence of a vacuum and (b) the use of vacuum only without the injection pressure. After initial testing, eight CFCC tubes were fabricated using these techniques. The matrix material used was Blackglas™. C-Nicalon™ in the form of woven fabric and BN-Nextel ®312 in the form of braided textile were used as reinforcements. C-Nicalon™ CFCC tubes with 4%–6% porosity, 55%–57% fiber volume fraction, and 2.12–2.18 g/cm3 density reached convergence by weight in 10 cycles (with about 17 hours per cycle), while BN-Nexlet ®312 CFCC tubes with 4%–6% porosity, 70%–72% fiber volume fraction, and 2.42–2.48 g/cm3 density converged by weight in 8 cycles. TheVARTMprocessing time averaged 15 minutes for each tube. The mechanical performance of the components was evaluated at room and high temperatures using a C-ring test. Scanning Electron Microscopy (SEM) was employed to study the microstructure of the parts. The results show that the without injection pressure technique offers a promising method to produce tubular CFCCs in terms of lower manufacturing costs, part uniformity, and enhanced mechanical properties. BN-coating performs better at high temperature compared with C-coating. Also, a combination of BN-coating and a textile braided architecture of fiber preform proved to enhance the performance of the manufactured CFCCs. Finally, the mechanical performances of the manufactured CFCC tubes using VARTMtechnique were compared with those using a cure-on-the-fly filament winding technique for a similar geometry using the same materials.
Driving Rain on Building Envelopes— II. Representative Experimental Data for Driving Rain Estimation
Authors: Blocken Bert , Carmeliet Jan
Published: August 2002

A practical numerical method for driving rain estimation was presented in “Driving Rain on Building Envelopes—I” (Blocken and Carmeliet, 2000). An important prerequisite in employing this method is that the climatic data used as input are representative. In this paper, the attainment of representative experimental data for driving rain estimation is analysed. The importance of a sufficiently small time step to obtain representative climatic data measurements is indicated. It is shown that representative averaged values for wind speed and rainfall intensity for longer time steps can be obtained by averaging the measured data with the rainfall amounts as weighting factors. The effects of using different averaging techniques on the accuracy of the calculated driving rain results are investigated. It is found that the presented weighted averaging technique can provide accurate representative averaged data, whereas commonly used averaging techniques can give rise to large errors.
Carbon Fiber Reinforced Shape Memory Polymer Composites
Authors: Gall Ken , Mikulas Martin , Munshi Naseem A. , Beavers Fred , Tupper Michael
Published: August 2002

In this paper we present results on the deformation of carbon fiber reinforced shape memory polymer matrix composites for deployable space structure applications. The composites were processed using resin transfer molding or a pre-impregnated (pre-preg) laminate press, with both satin and plain weave fiber architectures. The polymer matrix glass transition temperature, T g, was approximately 95°C. Composite specimens were bent to specific radii at T = 120°C, and cooled while constrained to a temperature of 25°C, which left them frozen in the bent state. Heating the specimens above T g caused the composites to return to their original unbent shape with up to 95% recovery based on bend angle. The effect of constraint hold times up to 350 hours on the recoverability was found to be negligible. Microscopic investigations revealed that the dominant local deformation mode of the composites was buckling of the carbon fibers on the inner surface of the bend. Localized buckling out of the material plane lead to detrimental interfacial matrix failure while dispersed in-plane buckling was elastic and non-damaging. A clear path for tailoring the shape memory polymer composites to facilitate in-plane elastic buckling is presented and tested. The improved materials can bend to local radii of curvature, R, of 1.6 mm with full recoverability and negligible local damage.
Locating Structural Defects Using Operational Deflection Shapes
Authors: Jin Si , Pai P. Frank
Published: August 2002

This paper presents a Boundary Effect Detection (BED) method for pinpointing defects in plates using Operational Deflection Shapes (ODSs) measured by a scanning laser vibrometer. An ODS consists of central and boundary solutions. Central solutions are periodic functions, and boundary solutions are exponentially decaying functions due to boundary constraints. Because defects introduce new boundaries to a structure, boundary solutions exist around structural boundaries and defects. The BED method uses a sliding-window surface-fitting technique to extract boundary solutions from a measured ODS to reveal locations of defects. The proposed defect detection method is non-destructive because structures only need to be excited to have very small vibrations, and it works without using any structural model or historical data for reference. An in-house finite element code GESA1 is used to analyze a 579 × 762 × 3.10 mm aluminum plate using 108 higher-order rectangular plate elements. Numerical results show that high-order spatial derivatives of ODSs are sensitive defect indicators for locating small defects. Experimental studies on the 579 × 762 × 3.10 mm aluminum plate with four different defects show that this defect detection method is capable of pin-pointing small defects.
Design of Passive Energy Dissipation Systems Based on LQR Control Methods
Authors: Agrawal A. K. , Yang J. N.
Published: August 2002

The design of passive energy dissipation systems, referred to as passive dampers, involves the determination of the required capacity of each damper installed at selected locations. Generally, dampers with an identical capacity are installed in various story units of a building. However, installing identical dampers in various story units does not achieve the optimal performance for the building and it may result in a conservative and more expensive design. In this paper, two design methods, based on the concepts of linear quadratic regulator (LQR) control theories, are presented for the design of the capacity of passive dampers. For most of the passive dampers, the force applied to the structure depends only on the displacement and velocity across the damper. From the standpoint of control theories, the passive control force depends only on the local measurements of the displacement (i.e., drift across the damper) and velocity. This type of controller is referred to as the decentralized controller. Consequently, LQR control theories for the design of active controllers are modified and applied to the design of passive dampers. Advantages of the proposed methods for different types of passive dampers are demonstrated through numerical simulations.
Surface Temperature a Thermal Bridges
Authors: Csoknyai TamÁs
Published: August 2002

The recent work aimed at the determination of the correct film coefficient value at design, since the practical experiences do not ensure the theory. It was proved by monitoring the film coefficient value along the edges and at thermal bridges and showing that it differs from the overall standard design value and varies in function with the temperature and several further random effects. Therefore, different hi values should be taken into consideration while calculating heating load and surface temperature.
Note. Antimicrobial Effect of Pressurized Carbon Dioxide on Yersinia enterocolitica in Broth and Foods
Authors: Erkmen O.
Published: August 2002

Antimicrobial effect of 15, 30 and 60 atm CO 2 pressures was studied on Yersinia enterocolitica at 25, 35 and 45 °C. Two stages were observed in the destruction curves. The earlier stage was characterized by a slow rate of inactivation in number of Y. enterocolitica, which increased sharply at the later stage. An increase of pressure and/or temperature enhanced the antimicrobial effects of CO 2. The D values of 6.1 and 4.9 min were obtained for Y. enterocolitica at 45 °C under 15 and 30 atm CO 2 pressure, respectively, while only 1.3 min D value was found at 60 atm. A rapid and significant ( p < 0.05) reduction was obtained in the number of Y. enterocolitica at treated pressures and temperatures. Pressure, temperature, exposure time, and the suspending medium influenced the inactivation rates of Y. enterocolitica.
Dynamic Modeling of an Innovative Piezoelectric Actuator for Minimally Invasive Surgery
Authors: Edinger Benjamin , Frecker Mary , Gardner John
Published: August 2002

A small piezoelectric inchworm actuator has been designed for use with a monolithic compliant end-effect or in minimally invasive surgery procedures. A dynamic model of the inchworm actuator has been developed using SIMULINK. Utilizing the equations of motion for the inchworm actuator, the dynamic characteristics of the piezoelectric stack material, and the known compliance of the gripper, a force measurement model has been developed which extracts resisting force information from the piezoelectric signal. The focus of this paper is on the development of the dynamic model and the results of a simulation study that will be used to develop optimal driving signals for the inchworm actuator. Simulation results include the predicted displacement capabilities and settling time of the inchworm actuator over a range of driving frequencies.
Modal Analysis of a Non-Circular Cylindrical Laminated Shell Using Conformal Mapping
Authors: Thamburaj Priya , Sun J. Q.
Published: August 2002

This paper presents a method to analyze the free and forced vibration responses of a finite uniform cylindrical shell. The cross section of the shell is a square with rounded corners. This geometry makes the analysis of the system difficult. The approach in this work is to apply a conformal mapping to map the physical domain onto a circular cylindrical domain. The Rayleigh-Ritz method is applied to solve for the solution. Numerical results of the mode shapes and the forced response at different frequencies are presented.
Influence of the Selection of the Suture Material on the Mechanical Behavior of a Biomaterial to be Employed in the Construction of Implants. Part 1: Calf Pericardium
Authors: Páez J. M. García , Carrera A. , Herrero E. Jorge , Millán I. , Rocha A. , Cordón A. , Sainz N. , Mendez J. , Castillo-Olivares J. L.
Published: August 2002

A hydraulic stress simulator was employed to study the mechanical behavior of the calf pericardium used in the construction of cardiac valve leaflets. One hundred eighty pairs of tissue samples were subjected to tensile testing to rupture. One of the two samples from each of 144 pairs (four series of 36 pairs each) was sutured with commercially available threads made of nylon, silk, Prolene or Gore-Tex, while the other sample in each of these pairs was left unsewn. The remaining 36 pairs were employed as controls in which neither of the two samples was subjected to suturing. The sutured tissue samples showed a significant decrease in tensile strength at rupture (range: 11.81 to 26.04 MPa) when compared with unsutured samples (range: 39.38 to 87.96 MPa; p < 0.01). The application of morphological and mechanical selection criteria to maximize the homogeneity of the samples provided excellent fit with respect to the stress/strain curves. This method made it possible to carry out a predictive study of the mechanical behavior of a sutured sample, based on that observed in the corresponding unsutured fragment. The interaction of the different suture materials with the pericardial tissue was also assessed by comparing the mechanical behavior of the sutured samples with that of the control samples. At stresses of less than 0.8 MPa, samples sewn with Gore-Tex were found to show the least difference with respect to the controls, indicating that this material presented the lowest degree of interaction with the pericardium.

In conclusion, the degree of the loss of resistance to tearing of the sutured samples is of no value in the selection of the optimal suture material. The selection process applied makes it possible to predict the mechanical behavior in response to suturing of a given unsewn tissue specimen by determining that of its sutured mate. The similarity between the findings in samples sewn with Gore-Tex and in the unsutured controls indicates a lesser degree of interaction between thesuture material and the pericardium employed in the construction of cardiac valve leaflets.
Polymers for Use in Controlled Release Systems: The Effect of Surfactants on their Swelling Properties
Authors: Vlachou M. , Hani N. , Efentakis M. , Tarantili P. A. , Andreopoulos A. G.
Published: August 2002

The effect of an ampholytic surfactant on the swelling properties of polymeric materials was studied, using various swelling liquids. Tablets were prepared consisting of hydroxypropyl methylcellulose, poly(oxyethylene) and sodium alginate. Tego betain was the non-ionic surfactant used as an additive in a series of samples made of the above polymers. Those tablets were immersed in distilled water, phosphate buffer and 0.1 N HCl, and their weight uptake was recorded as a function of time, in order to assess the swelling process. Measurements of the contact angle of the above systems were also carried out for estimating their wetting properties.

The results of this study showed a selectivity among polymers, surfactant and surrounding liquid. Clearly, an enhancement of the swelling capacity of hydroxypropyl methylcellulose tablets due to the surfactant was recorded. An unclear effect was observed in the case of poly(oxyethylene), whereas for sodium alginate, the dominant factor is its water solubility that controls swelling behaviour.
On the Heat Release of Burning Karaoke Music Compartments
Authors: Chow W. K. , Lui Gigi C. H.
Published: August 2002

The possible heat release rates of fires resulting from burning combustibles in 900 karaoke music compartments of 19 local karaokes were studied. Combustibles of concern are furniture foam, partitions and surface lining materials. Equations appearing in the literature for calculating the heat release rates of these combustibles are used. Heat release rates of furniture foams were studied first, followed by igniting surface lining materials classified under the Swedish system. The likelihood of flashover in those 900 karaoke music compartments was then investigated. Further, the total heat release rate curves for burning foam, surface lining materials and carpets are studied using the results reported in the literature. Based on this study, it is recommended to select furniture foam with less heat release rates upon burning, and replace timber surface lining materials as soon as possible. As an urgent action, a good fire safety management scheme “tailor-made” for individual karaokes is to be implemented.
CNS Assessment Using Functional Neuro-PET Imaging
Authors: Laven David L. , Bednarczyk Edward M.
Published: August 2002

Disorders of the brain manifest in a variety of manners ranging from feeling or thought abnormalities to total paralysis. Until recently, most imaging methods of the brain have been limited to anatomic considerations, with little information about actual function of the brain except that deduced from clinical examination and physical and cognitive assessment testing. With the advent of positron emission tomography (PET) and enhanced computer and scintigraphic image detection systems, there is keen interest in applying this imaging technique to better understand brain physiology and pathophysiology. Potential applications of PET in CNS assessment is expanding avenues for improved diagnosis and staging of disease, as well as monitoring therapeutic interventions. A general review of the radiopharmaceuticals used for neuro-PET imaging, as well as their application in situations such as cerebrovascular disease, brain activation studies, various movement disorders and dementias, depression, epilepsy, obsessive-compulsive disorder, schizophrenia, and neuropharmacology (including cerebral receptor studies) will be presented.
Damage Metric-Based Mapping Approaches for Developing Accelerated Thermal Cycling Guidelines for Electronic Packages
Authors: Pucha Raghuram , Pyland James , Sitaraman Suresh K.
Published: August 2002

The accumulated equivalent inelastic strain per cycle and the maximum strain energy density over one cycle have been used as damage metrics to map the solder fatigue damage during Field-Cycling (FC) and Accelerated Thermal Cycling (ATC) simulations. The objective of this work is to develop accelerated thermal cycling guidelines for flip-chip on board and flip-chip chip-scale electronic packages used in, for example, automotive applications. The percentage contributions of plastic and creep strains to the total inelastic strain and contributions within the accelerated cycling are used as a basis for developing modified accelerated thermal cycles. Different temperature regimes are explored to match the contributions of plastic and creep strains to total inelastic strain during field-cycling and accelerated thermal cycling and to reduce the time required for accelerated thermal cycling. The process mechanics of component assembly, time-and temperature-dependent material behavior and critical geometric features of the assembly are taken into consideration while developing the comprehensive virtual accelerated thermal cycling methodology.
A Domain Wall Model for Hysteresis in Piezoelectric Materials
Authors: Smith Ralph C. , Ounaies Zoubeida
Published: August 2002

This paper addresses the modeling of hysteresis and nonlinear constitutive relations in piezoelectric materials at moderate to high drive levels. Hysteresis and nonlinearities are due to the domain structure inherent to the materials and both aspects must be addressed to attain the full potential of the materials as sensors and actuators in high performance applications. The model employed here is based on previously developed theory for hysteresis in general ferroelectric materials. This theory is based on the quantification of the reversible and irreversible motion of domain walls pinned at inclusions in the material. This yields an ordinary differential equation (ODE) model having five parameters. The relationship of the parameters to physical attributes of the materials is detailed and algorithms for determining estimates of the parameters using measured values of the coercive field, differential susceptibility and saturation properties of the materials are detailed. The accuracy of the model and its capability for the prediction of measured polarization at various drive levels is illustrated through a comparison with experimental data from PZT5A, PZT5H and PZT4 compounds. Finally, the ODE model formulation is amenable to inversion which facilitates the construction of an inverse compensator for linear control design.
Mechanical and Electrical Properties of an Electrorheological Fluid
Authors: Nilsson Magnus , Ohlson G.
Published: August 2002

Adaptive structures contain parts whose properties may be tuned so as to suit some purpose. Certain fluids change viscosity when subjected to an electrical field. This paper concerns the behaviour of such an electrorheological fluid, ERF, which may be characterized as visco-plastic with some elasticity present. The stress response to a prescribed strain is studied in tests. Various models for describing the observed behaviour are analyzed. Results show that modelling the ERF as a Bingham fluid gives a rather close fit for low field strength. A solid mechanics model which displays yielding with kinematic strain hardening is preferred for high field strength as it then describes the observed amplitude and frequency dependence quite well. Relevant constants for investigated models are listed as functions of the field strength. The electrical behaviour is essential in designing parts for on-line response of structures, in order to control vibrations. Results show that a damper containing ERF responds to applied voltage as a capacitor whose leak resistance depends on voltage whereas its capacity does not. AC as well as DC fields are treated. When subjected to harmonic displacement the force response of the damper contains superharmonics owing to the non-linearity of the ERF. In AC powered dampers, intermodulation frequencies between field and displacement are identified.
Reducing Pulmonary Disease: The Pharmacist’s Role in Smoking Cessation
Authors: Hudmon Karen Suchanek , Corelli Robin L. , Kroon Lisa A. , Shreve Marilyn Standifer , Prokhorov Alexander V.
Published: August 2002

As an important interface with the healthcare system for many patients, pharmacists are in a unique position to assist patients with quitting smoking, thereby improving patients’ pulmonary health. Because nicotine replacement therapy products and bupropion are available to patients largely via pharmacies, the pharmacist has become a logical candidate for providing smoking cessation assistance. Furthermore, research has shown that when pharmacists counsel patients on medications for quitting smoking, their intervention positively impacts smoking cessation rates. This article provides a review of methods for cessation and provides pharmacists with feasible and effective smoking cessation counseling strategies for implementation into everyday practice. The intervention approach draws heavily upon the U.S. Public Health Service Clinical Practice Guideline for Treating Tobacco Use and Dependence.
Influence of Quick Ageing on the Fatigue Behaviour of SMC Composite Materials
Authors: Quaresimin M. , Guglielmino E.
Published: August 2002

This paper summarises the results of an investigation on the influence of environmental exposure, simulated by means of quick ageing conditioning, on the static and fatigue strength of an SMC-R25 composite material. The material under investigation consisted of an unsaturated polyester matrix reinforced with 25% E-glass fibres and with 50% of aluminium hydroxide as filler. Three environmental conditionings were analysed: thermal cycles, salt mist, thermal cycles and salt mist; the static and fatigue properties were evaluated on specimens taken from the SMC blanks after conditioning and the results were compared with those obtained for the material as moulded. An increase both in the static and fatigue strength together with a decrease in the static tensile modulus was noticed for the conditioned material, although the scatter of the results was in some cases too wide to identify a well defined influence. The analysis of the stiffness reduction during the fatigue tests showed differences in the damage evolution between as moulded and preconditioned material.
Ionic Doping of Low Conductivity Structural Resins for Improved Direct Current Sensing
Authors: England Kenric M. , Gillespie John W. , Fink Bruce K.
Published: August 2002

This investigation developed amethodology for doping high resistivity vinyl-ester resins with an organic dopant to increase ionic conductivity. The polymeric resin system investigated was a Dow Derakane 411-C50 vinyl-ester (VE) resin. Anumber of potential dopants were studied and two in particular, tetrabutylammonium acetate and tetrabutylammonium iodide, were found capable of increasing the ionic conductivity of VE resin an order of magnitude without adversely affecting the resin viscosity, mechanical properties, or reaction kinetics. The most suitable dopant found in this investigation was a tetrabutylammonium acetate (TA) organic salt. TA, at a 0.1 wt% concentration, was shown to have negligible effects on themechanical properties and reaction kinetics of a curing VE part. TA was found to slightly increase the rate at which viscosity increases, but not to the extent that would hinder resin transfer molding of a doped VE system. This investigation has proven that doping of VE resin with 0.1 wt% TA is a viable means of controlling and tailoring the conductivity of high resistivity resins for the application of direct current (DC) sensing technology.
Management and Prevention of Opportunistic Infections in the HIV-Infected Patient
Authors: Purdy Bonnie D.
Published: August 2002

With the introduction of potent antiretroviral therapy, the incidence of opportunistic infections (OIs) as well as death has dramatically decreased since 1996. Opportunistic infections are seen mainly in three groups: (1) newly diagnosed patients not receiving antiretroviral therapy and presenting with an OI, (2) patients nonadherent to antiretroviral and OI treatment regimens or (3) patients whose antiretroviral therapy has failed. This article will review the most common opportunistic infections (OIs) seen in the HIV-infected individual and their treatment. The current guidelines for the prophylaxis against these OIs will also be discussed.
Fractal Analysis of Damage Evolution of Rock
Authors: Zhou J. Z. , Yu T. Q. , Xu X. H.
Published: August 2002

It is well known that rock is a natural material containing inherent micro-defects and its mechanical properties strongly relate to the presence of micro-pores and micro-cracks in the material. The damage in rock is believed to be mainly due to initiation and development of micro-defects with irregularity and fractal characteristics. In this paper the damage evolution process in rock is examined and the relationship between the damage variable and the fractal dimension is established based on the fractal geometry method.
Fail-Safe Magneto-Rheological Fluid Dampers for Off-Highway, High-Payload Vehicles
Authors: Gordaninejad Faramarz , Kelso Shawn P.
Published: August 2002

This paper presents the study of a field-controllable, semi-active magneto-rheological fluid (MRF) shock absorber for high-payload, off-highway vehicles. A MRF damper is developed that is tailored for ground vehicles which undergo a wide range of dynamic loading. The MRF damper also has the capability for different rebound and compression characteristics. The new MRF shock absorber emulates the original equipment manufacture shock absorber behavior in its passive-off mode. Theoretical and experimental studies are performed to examine this MRF damper. The Bingham Plastic theory is employed to model the nonlinear behavior of the MRF. A fluid-mechanics-based theoretical model along with a three-dimensional finite element electromagnetic analysis is utilized to predict the MRF damper performance. The theoretical and experimental results are demonstrated to be in good agreement.
A Simplified Thermal Treatment of Fireballs
Authors: Jones J. C.
Published: August 2002

A simple means of estimating fireball temperatures, for particular sizes of leakage, is developed on the basis of the use of a previously existing plot of radiation heat transfer against time as a “template.” Such calculations are performed for large and small propane fireballs.
Performance Evaluation of a Mixed Mode ER Engine Mount Via Hardware-in-the-Loop Simulation
Authors: Choi S. B. , Choi Y. T. , Cheong C. C. , Jeon Y. S.
Published: August 2002

This paper proposes a new type of an ER (electro-rheological) engine mount which has a mixed mode as fluid working mode (the combination of shear and flow modes). As a first step, a mixed mode ER engine mount, which is applicable to a medium-sized passenger vehicle, is designed and manufactured by incorporating Bingham model of the ER fluid. The vibration isolation performance of the ER engine mount with different intensity of electric fields is evaluated in the frequency domain and compared with that of conventional hydraulic type engine mount. Subsequently, a full car system installed with the proposed ER engine mounts is constructed and modeled by considering engine excitation forces. After deriving its governing equations of motion, HIh control algorithm is formulated by taking into account the semi-active actuating condition. The vertical engine displacement and body acceleration are evaluated via hardware-in-the-loop simulation (HILS) at various engine excitation frequencies.
Theoretical Analysis of the Effects of Cigarette Design Parameters on the Smoldering Rates, Heat Flux, and Total Heat Released during Smoldering of a Cigarette
Authors: Yi Sung-Chul , Song Eun-Seok , Oh Seong-Geun , Bae Seong-Youl , Moon Sei Ki , Hajaligol Mohammad R.
Published: August 2002

A mathematical model developed by Muramatsu, Umemura, and Okada (1979) was modified and improved by changing the relative amounts of radiative and conductive heat transfer to study the effects of moisture content in the cigarette, cigarette packing density, and cigarette circumference on the smoldering rates, heat flux, and total heat released during natural smolder of a cigarette.

A mathematically predicted temperature profile was fitted to the corresponding experimental values with a nonlinear least-square fitting routine to obtain a smoldering rate and the relative amounts of radiative and conductive heat transfer. Then, based on the relative contribution of heat transfer modes, the heat flux and the total heat released were calculated with the fitted smoldering rate as a function of cigarette design parameters. Results show that the circumference of the cigarette is the major physical factor affecting mass burn rate (MBR), while the packing density of the cigarette strongly affects the linear burn rate (LBR), heat flux, and total heat released.
Polymer Matrix Woven Fabric Composites Subjected to Low Velocity Impact: Part III—Effect of Incident Impact Velocity and Impactor Mass
Authors: Naik N. K. , Meduri Sailendra , Chandrasekher Y.
Published: August 2002

The studies have been carried out on the damage initiation behavior of polymer matrix woven fabric composite plates subjected to a transverse central low velocity point impact load. Specifically, the effect of incident impact velocity and impactor mass for the same incident impact energy on the impact behavior has been investigated with a square plate of 150 mm × 150 mm × 6 mm. The material systems considered are: E-glass/epoxy and T300/5208 carbon/epoxy woven fabric composites. Inplane failure of the layers in the form of matrix cracking / lamina splitting and delaminations were the primary objectives of the study. The studies have been carried out using an in house Finite Element Analysis code. The inplane failure functions and the interlaminar failure functions have been predicted using quadratic failure criteria. It is observed that the use of incident impact energy alone as a parameter to characterize the impact behavior is inadequate. Instead, the effect of both incident impact velocity and impactor mass should be considered separately.
Degradation of Continuous Carbon Fiber Reinforced Polyetherimide Composites During Induction Heating
Authors: Augh L. , Gillespie J. W. , Fink B. K.
Published: August 2002

Induction heating of carbon-fiber-reinforced thermoplastic-matrix composites has numerous advantages over conventional methods. Volumetric heating and high heating rates offer a significant reduction in cycle times for processing high-quality thick-section composites. However, the influence of high-frequency electromagnetic fields on the composite is not well understood. Two mechanisms of degradation during electromagnetic induction heating of AS4 carbon-fiber polyetherimide (PEI) were studied—thermal degradation and dielectric breakdown. Crosslinking and chain scission reactions are two major thermal degradation mechanisms that occur during melt processing of PEI. Changes in the molecular weight and glass transition temperature of the polymer were quantified over a wide range of process temperatures and times. The rheological properties of the composite system are also monitored to investigate viscosity changes due to molecular weight changes during the process. Dielectric breakdown during the induction process was also carefully examined. No significant change in polymer properties resulted from exposure to high electromagnetic fields.
Development of Two- and Three-Dimensional Bi-Material Elements
Authors: Soh Ai Kah
Published: August 2002

A procedure for developing two- and three-dimensional bi-material elements, which are able to eliminate the weakness of the conventional finite elements in determining the stress distributions along fibre-matrix interfaces, has been proposed. Two- and three-dimensional mulitfibre composite models were employed to illustrate the versatility and potential accuracy of the proposed elements. The results obtained by these bi-material elements are in good agreement with the experimental results and are superior to the conventional finite element results. A comparison is made between the proposed approach of improving the interfacial stress calculations and another approach which employs the least squares fitting method. The comparison shows that the two approaches provide comparable accuracy but the latter is more difficult to implement.
New Algorithms for 3-D Imaging and Analysis of Open-Celled Foams
Authors: Montminy Matthew D. , Tannenbaum Allen R. , Macosko Christopher W.
Published: August 2002

Open-celled foams are three-dimensional networks of polymeric cells. The mechanical properties of a foam depend on the size and geometry of its cells. Since foams have a three-dimensional polyhedral structure, the two-dimensional characterization techniques currently used provide limited accuracy.

Nuclear magnetic resonance and x-ray tomography methods offeropportunities for three-dimensional imaging of these polyhedral structures. Software, which can use digital three-dimensional images to determine structural parameters such as strut length distribution, connectivity, and cell size, is being developed.

The image processing approach uses conformal curvature flow (CCF)segmentation to find the surfaces of foam struts in the 3-D images. Once these surfaces have been found, volume thinning is used to find the structural skeleton of the foam. The resulting data set can then be used to determine many statistical characteristics of the foam, including strut length distributions, window size and shape distributions, and cell size information.

Analysis of a reticulated polyurethane foam sample using these methods yielded a reasonable approximation of the structural skeleton of the sample.
An Investigation into the Accuracy of a One-Parameter Nonlinear Model for Unidirectional Composites
Authors: Winn Victoria M. , Sridharan Srinivasan
Published: August 2002

The nonlinear response of unidirectional composites has often been modeled using orthotropic plasticity theories. Of these, the one-parameter model developed by Sun and Chen is the simplest and hence attractive from the point of view of applications. The range of applicability of this theory is investigated by performing a number of off-axis tension tests on laminae, shear tests on 0°/90° laminates and uniaxial tension tests on +45°/–45° laminates. The theory appears to explain the results of off-axis tension test of laminae, but is unable to accommodate the full range of stress-strain response observed in the case of laminates. This is clearly due to extensive micro-cracking that laminates with orthogonal fiber orientations are able to withstand prior to failure—a phenomenon the single parameter model is not designed to account for. Nevertheless, it appears from the limited number of results presented, that the model if properly calibrated, can be used to predict the behavior of both laminae and laminates with reasonable accuracy.
Flextensional Transducers with Shape Memory Caps for Tunable Devices
Authors: Meyer R. J. , Newnham R. E.
Published: August 2002

Shape memory alloys were used as caps for the “cymbal” flextensional transducer. The active caps provide a tunable resonance frequency and a damage recovery mechanism associated with the alloy’s martensitic phase transformation. These two concepts were investigated and a 25% change in resonance frequency was observed for Ni-Ti alloy caps. It was also demonstrated that complete shape recovery could be achieved after hydrostatic pressures buckled the transducer caps. Cap deformation and recovery were demonstrated with profilometer and d h measurements.
Haptic Device Working with an Electrorheological Fluid
Authors: Bose Holger , Berkemeier Hans-Joachim
Published: August 2002

A haptic device based on an electrorheological fluid has been designed and tested. The device is similar to ajoystick which controls the motion of a cursor on a computer screen. In electric fields of different strength the shear stress of the electrorheological fluid is increased accordingly, which is perceived by the user by different resistance forces against the motion of the joystick. Controlled by the software the user can feel if the cursor enters a selected field on the screen. Such haptic devices can be useful in various possible applications like supporting tools for the operation of machines, assisting interfaces for blind persons working with a computer, virtual reality or computer games. The design of the haptic device, its components and the electrorheological fluid used are described.
Ripening-Associated Microstructural Changes in Antisense ACC Synthase Tomato Fruit
Authors: Sozzi G. O. , Fraschina A. A. , Castro M. A.
Published: August 2002

The ultrastructural impact of low ethylene biosynthesis (less than 0.5% of normal levels) was evaluated in transgenic (A11.1) tomatoes ( Lycopersicon esculentumMill.) expressing an antisense 1-aminocyclopropane-1-carboxylic acid synthase (ACC-S) transgene by means of transmission and environmental scanning electron microscopy. In 48-day mature green fruit, no significant ultrastructural differences were found between transgenic and control tomatoes. In 78-day control fruit, which were overripe and showed deteriorated texture, many areas of the cytoplasm were devoid of structures, and micrographs showed cell collapse with folding and dissolution of the cell wall. On the other hand, in 90-day transgenic fruit, which were firm and not ripe, the cytoplasm showed a relatively high electron density. Plastids retained remnants of chloroplast thylakoids along with significant amounts of osmiophylic plastoglobuli, but lycopene was not detected. Conspicuous starch granules were observed in mature green transgenic tomatoes, but were not detected in 90-day chlorochromoplasts. Electron-dense regions reflecting the integrity of the middle lamella alternated with other partially degraded regions. This incipient dissolution of the middle lamella pectic polymers may be attributable to nonenzymatic deaggregation or to cell-wall hydrolases which could be ethylene independent or responsive to very low levels of ethylene. Besides, cells were attached along extended contact areas and appeared turgid. This feature may provide an explanation of firmness retention that does not solely involve cell walls. Disruption of the middle lamella and development of lycopene crystalloids were observed when exogenous ethylene (12 ppm) was applied.
Establishing an Ambulatory Care Clerkship at a Coast Guard Clinic
Authors: Huntzinger Paul E.
Published: August 2002

This paper describes the experience and benefits of establishing a pharmacy student clerkship program with the University of California, San Francisco (UCSF) at a U.S. Coast Guard (USCG) ambulatory care clinic. The goal of the paper is to provide pharmacists with information that can be used to institute a clerkship program. The implementation of the clerkship at the Integrated Support Command Alameda (ISCA) pharmacy involved an uncomplicated, step-wise approach that can be readily emulated. The clerkship provided the ISCA pharmacy with several benefits, including the opportunity for the pharmacist to mentor, that clearly outweighed the challenges.
Development of Conductive Knitted- Fabric-Reinforced Thermoplastic Composites for Electromagnetic Shielding Applications
Authors: Cheng K. B. , Ramakrishna S. , Lee K. C.
Published: August 2002

This paper presents a feasibility study to develop conductive knitted-fabric-reinforced thermoplastic composites for electromagnetic shielding applications. Polypropylene is the matrix phase, and glass fibers are the reinforcement phase of the composite material. Stainless steel wires and staple yarns are incorporated as conductive fillers to facilitate the electromagnetic shielding properties of the composite material. Owing to their high stiffness, knitting of glass fibers and stainless steel wires is very difficult. To facilitate the knitting, uncommingled yarns comprising stainless steel wires, glass, and polypropylene fibers are produced using a hollow spindle spinning method. Different kinds of weft knitted fabrics are produced, which are subsequently consolidated into composite materials using a compression molding method. The electromagnetic shielding effectiveness (EMSE) of various knitted composites is measured in the frequency range of 300 kHz to 3 GHz. The variations of EMSE of knitted composites with the fabric structure, stitch density, number of plies, and amount of stainless steel are described. The suitability of the knitted composites developed in this study for electromagnetic shielding applications is also discussed.
In Vitro Release Behavior of Dextran-Methacrylate Hydrogels Using Doxorubicin and other Model Compounds
Authors: Kim Sin-Hee , Chu Chih-Chang
Published: August 2002

In vitro drug release behavior of doxorubicin, Alizarin Red S, FITC-dextran from photocross-linked dextran-methacrylate hydrogel was studied. The effects of pH of media, degree of substitution (DS) of dextran-methacrylate hydrogel, and molecular weight of model compounds on their release profiles were investigated. Each model compound was successfully incorporated into dextran-methacrylate hydrogel matrix through photo-polymerization of the hydrogel precursor. Delayed release of model compounds was observed with these hydrogels having a higher DS. Doxorubicin and Alizarin Red S showed pH-dependent release behavior because of the presence of ionizable groups in their structure. Different types of ionization of doxorubicin and Alizarin Red S resulted in more release into an acidic or alkaline media. As molecular weights of drugs increased, the total amount of released drug at the end of 240 hrs decreased significantly and reached a minimum level as the MW of drugs reached about 10,000. Release of these three model compounds followed simple Fickian diffusion at an early stage of release, i.e., cumulative release of model compounds was proportional to the square root of time. Dextran-methacrylate hydrogel effectively delayed and controlled the release of anticancer antibiotics, doxorubicin.
A Quarter-Car Experimental Analysis of Alternative Semiactive Control Methods
Authors: Ahmadian Mehdi , Pare Christopher A.
Published: August 2002

The performance of three semiactive control policies, including the well-known skyhook control and two others that are referred to as “groundhook” and “hybrid” control, are studied experimentally. The experiments use a single suspension apparatus that is commonly referred to as “quarter-car” rig, and a magnetorheological damper that is built and tuned for the purpose of this study. Upon describing the mathematics of the three semiactive control policies and the construction of the quarter-car rig, the results of a series of experiments with each control policy are presented. The transmissibility plots of the test results confirm the features of each control policy, as discussed in the past analytical studies. The results indicate that skyhook control can significantly reduce the transmissibility of the sprung mass, as compared with passive dampers. Similarly, groundhook control substantially reduces the unsprung mass transmissibility. For vehicle applications, reducing the sprung mass transmissibility often results in improving the ride comfort, and reducing the unsprung mass transmissibility provides less wheel hop, therefore resulting in better road holding ability and improved vehicle stability. The test results for hybrid control, which is intended to provide a combined effect of skyhook and groundhook, indicate that it holds the promise of achieving a semiactive control policy that can be slowly adapted to the driving condition and vehicle dynamics for better vehicle stability and ride comfort.
An Energy-Efficiency, Performance Study of, Vacuum Insulation Panels
Authors: Tao Wei-Han , Chang Chih-Chen , Lin Jian-Yuan
Published: August 2002

Vacuum insulation panel (VIP) consists of the core materials that were encapsulated at low pressure in a very thin, low gas permeability and low conducting barrier. The paper presented herein focuses on a unique panel design based on the evacuated 100% open cell rigid polyurethane foam with getters encapsulated in laminated films under various conditions and the application of VIPs. A series of studies of the effect of the batch manufacture efficiency and the thermal conductivity performance of the VIPs was discussed. In this study, several pieces of VIPs were installed on the walls of a refrigerator, show-case and refrigerator vehicle cabinet to evaluate the energy efficiency by measuring the heat loss. Heat loss from a cabinet located in an environmental room was measured by a reversed heat leak method under testing conditions. The results show heat loss energy efficiency improving over 25% for mounting the VIPs on the refrigerator and the reverse heat leak is improved by 8.0% and 28.9% for the refrigerator vehicle cabinet and showcase, respectively