bluuebunny/crossref_metadata_2025 huggingface dataset:
Non‐linear matrix modeling of forest growth with permanent plot data: The case of uneven‐aged Douglas‐fir stands
Authors: Ralston R. , Buongiorno J. , Schulte B. , Fried J.
Published: August 2003

Uneven‐aged forest management is acquiring increasing importance throughout the world as an alternative to clear cutting. Simple stage‐structured matrix models can be used to predict the growth of uneven‐aged stands, and they are easily incorporated in optimization analysis. Parameters of these models can be estimated from readily available permanent plot data. Such a growth and yield model is presented for mixed, uneven‐aged Douglas‐fir and hardwood stands. The model was calibrated with data from 66 permanent plots in Oregon and Washington. The density‐dependent matrix model predicts the number of trees by diameter class and species type, softwood or hardwood. The parameters are based on individual tree growth equations, individual tree mortality equations, and stand ingrowth equations. The individual tree equations are a function of tree diameter, stand density, species, and site index. The stand‐level ingrowth equations are a function of stand density. The model was validated in the short term by comparing the number of trees in each diameter and species class at the time of the second inventory with the number predicted by the model, given conditions at the first inventory. A long‐term validation of the model was also done by comparing the steady‐state stand structure and stand volume with those observed for old‐growth stands. The model was applied to show the effects of different cutting cycles on productivity, diversity of tree species and size, and financial returns. The results suggest that uneven‐aged management of the Douglas‐fir forest type in the Pacific Northwest can be as productive as even‐aged management, with the added benefits of continuous cover forestry.
Can mature patch constraints mitigate the fragmenting effects of harvest opening size restrictions?
Authors: Rebain S. , McDill M. E.
Published: August 2003

Harvest scheduling models often include maximum harvest opening size constraints, a restriction generally imposed for legal or policy reasons. The maximum harvest opening size restriction can greatly affect the spatial layout of the forest, with the dispersed harvesting increasing forest fragmentation. Because they can offset the negative impacts of maximum harvest opening size constraints, mature patch size constraints, which require a certain amount of the forest to be in patches meeting both minimum size and age requirements, have also been included in these models. This paper looks at the economic and spatial effects of ten harvest scheduling formulations with these two constraint sets on 21 hypothetical forest landscapes. Analyses of their age‐class distributions, border distributions, and patch size distributions at the end of a 60‐year planning horizon confirm that maximum harvest opening size constraints tend to fragment forest landscapes and that mature patch constraints can significantly reduce these effects.
An Asymmetric "Implicit" Potential on the Real Line
Authors: Williams Brian Wesley , Lévai Géza
Published: August 2003

An exactly solvable, two-parameter implicit quantum mechanical potential is derived and characterized. With a change of variable, this potential is shown to belong to the Natanzon class, and for at least one value of the potential parameters, an explicit, rather than implicit, potential results.
Standard-Model Coupling Constants from Compositeness
Authors: Besprosvany J.
Published: August 2003

A coupling-constant definition is given based on the compositeness property of some particle states with respect to the elementary states of other particles. It is applied in the context of the vector-spin-1/2-particle interaction vertices of a field theory, and the standard model. The definition reproduces Weinberg's angle in a grand-unified theory. One obtains coupling values close to the experimental ones for appropriate configurations of the standard-model vector particles, at the unification scale within grand-unified models, and at the electroweak breaking scale.
An Exact Equation for Wilson Loops in Two-Dimensional Euclidean Space
Authors: Azam Mofazzal
Published: August 2003

We derive an exact equation for simple self non-intersecting Wilson loops in non-Abelian gauge theories with gauge fields interacting with fermions in two-dimensional Euclidean space.
On circle map coupled map lattice
Authors: Ahmed E. , Hegazi A. S.
Published: August 2003

The circle map in one and two dimensions is studied. Both its
stability and synchronization, using a bounded control and persistence, are discussed. This work is expected to be applicable in ecology where spatial effects are known to be important. Also, it will be relevant to systems where delay effects are not negligible.
Chern‐Simons forms of pseudo‐Riemannian homogeneity on theoscillator group
Authors: Gadea P. M. , Oubiña J. A.
Published: August 2003

We consider forms of Chern‐Simons type associated to homogeneous
pseudo‐Riemannian structures. The corresponding secondary classes
are a measure of the lack of a homogeneous pseudo‐Riemannian
space to be locally symmetric. In the present paper, we compute
these forms for the oscillator group and the corresponding
secondary classes of the compact quotients of this group.
Algorithm of J‐factorization of rational matrices with zeros and poles on the imaginary axis
Authors: Larin Vladimir B.
Published: August 2003

The problem of J‐factorization of rational matrices, which have zeros and poles on the imaginary axis, is reduced to construction of the solutions of two algebraic Riccati equations. For construction of these solutions, it is offered to use appropriate
algorithms. These algorithms permit to find the solutions in cases when the Hamiltonian matrices, which are corresponding to these equations, have eigenvalues on
the imaginary axis. Algorithms of factorization, which had been offered, permit to find the solution of the problem when the matrix, which will be factored, has zeros at infinity.
The lattice‐isometric copies of ℓ∞(Γ) in quotients of Banach lattices
Authors: Wójtowicz Marek
Published: August 2003

Let E be a Banach lattice and let M be a norm‐closed and
Dedekind σ‐complete ideal of E. If E contains a lattice‐isometric copy of ℓ∞, then E/M contains such a copy as well, or M contains a lattice copy of
ℓ∞. This is one of the consequences of more general
results presented in this paper.
An approximation to discrete optimal feedback controls
Authors: Zhu Jinghao , Zou Zhiqiang
Published: August 2003

We study discrete solutions of nonlinear optimal control
problems. By value functions, we construct difference equations
to approximate the optimal control on each interval of “small” time. We aim to find a discrete optimal feedback control. An algorithm is proposed for computing the solution of the optimal control problem.
On resolving edge colorings in graphs
Authors: Saenpholphat Varaporn , Zhang Ping
Published: August 2003

We study the relationships between the resolving edge chromatic number and other graphical parameters and provide bounds for the resolving
edge chromatic number of a connected graph.
An indirect boundary integral method for an oscillatory Stokesflow problem
Authors: Kohr Mirela
Published: August 2003

The purpose of this paper is to present an indirect boundary
integral method for the oscillatory Stokes flow provided by the
translational oscillations of two rigid spheres in an
incompressible Newtonian fluid of infinite expanse.
Existence of entire explosive positive radial solutions of quasilinear elliptic systems
Authors: Zuodong Yang
Published: August 2003

Our main purpose is to establish that entire explosive positive radial solutions exist for quasilinear elliptic systems. The main results of the present paper are new and extend previous results.
A survey of limit laws for bootstrapped sums
Authors: Csörgő Sándor , Rosalsky Andrew
Published: August 2003

Concentrating mainly on independent and identically distributed (i.i.d.)
real‐valued parent sequences, we give an overview of first‐order limit theorems available for bootstrapped sample sums for Efron′s bootstrap. As a light unifying theme, we expose by elementary means the relationship between corresponding conditional and unconditional bootstrap limit laws. Some open problems are also
posed.
Can We Build Artificial Stem Cell Compartments?
Authors: Semino Carlos E.
Published: August 2003

Animals carry stem cells throughout their entire life, from
embryogenesis to senescence. Their function during development
and adulthood consists basically of forming and sustaining
functional tissues while maintaining a small self‐renewing
population. They reside in a complex three‐dimensional environment
consisting of other nearby cells extracellular matrix components,
endogenous or exogenous soluble factors, and physical,
structural, or mechanical properties of the tissues they inhabit.
Can we artificially recreate tissue development such that stem
cells can both self‐renew and be instructed to mature properly?
The main factors required to regulate the maintenance and
differentiation of some types of stem cells are known. In
addition, new bioengineered synthetic materials that mimic
extracellular matrix components can be used as initial
scaffolding for building stem cell microenvironments.
Rapid Site‐Directed Mutagenesis Using Two‐PCR‐Generated DNA Fragments Reproducing the Plasmid Template
Authors: Allemandou Flore , Nussberger Jürg , Brunner Hans R. , Brakch Noureddine
Published: August 2003

We describe a new rapid and efficient polymerase chain reaction
(PCR)‐based site‐directed mutagenesis method. This procedure is
effective with any plasmid and it employs four oligonucleotide
primers. One primer contains the desired mutation, the second is
oriented in the opposite direction (one of these two primers
should be phosphorylated), and the third and fourth should be
coding in complementary fashion for a unique restriction site to
be introduced in a nonessential region. The method consists of
two simultaneous PCR reactions; the PCR products are digested with
the enzyme that recognizes the newly introduced unique
restriction site and then ligased and used to transform competent
bacteria. Additionally, the use of Dpn I facilitates the
elimination of template DNA. The newly introduced restriction
site is essential for ligation in the correct orientation of the
two‐PCR products and is further used for mutant screening.
Resulting plasmids carry both the new restriction site and the
desired mutation. Using this method, more than 20 mutants have
already been generated (using two different kinds of templates);
all these mutants were sequenced for the desired mutation and
transfected into AtT‐20 cells and the expressed mutant proteins
encoded by the vector were assayed.
Novel HLA Class I Alleles Associated with Indian Leprosy Patients
Authors: Shankarkumar U. , Ghosh K. , Badakere S. , Mohanty D.
Published: August 2003

Convincing results on HLA Class II associations have been
reported, however data on HLA class I association are limited and
inconsistent from studies in Leprosy. We present here the HLA A,
B, and C allele distribution by molecular high resolution PCR‐SSOP
technique in 32 leprosy patients compared with the 67 controls,
from the same ethnic background. The significant results from the
present study were a significant increase in frequency of HLA
A*0206, A*1102, B*4016, B*5110, Cw*0407, and Cw*0703 was observed when compared to controls. A striking decrease in the frequency of HLA
A*0101, Cw*04011, and Cw*0602 leprosy patients was observed when compared to the controls. Further haplotype A*1102‐B*4006‐Cw*1502 was significantly increased among the lepromatous leprosy patients when compared to the controls. It seems that HLA class I alleles play vital roles in disease association/pathogenesis with leprosy among Indians.
A Critique and Improvement of an Evaluation Metric for Text Segmentation
Authors: Pevzner Lev , Hearst Marti A.
Published: August 2003

The Pk evaluation metric, initially proposed by Beeferman, Berger, and Lafferty (1997), is becoming the standard measure for assessing text segmentation algorithms. However, a theoretical analysis of the metric finds several problems: the metric penalizes false negatives more heavily than false positives, overpenalizes near misses, and is affected by variation in segment size distribution. We propose a simple modification to the Pk metric that remedies these problems. This new metric—called Window Diff—moves a fixed-sized window across the text and penalizes the algorithm whenever the number of boundaries within the window does not match the true number of boundaries for that window of text.
Syllable-Pattern-Based Unknown-Morpheme Segmentation and Estimation for Hybrid Part-of-Speech Tagging of Korean
Authors: Lee Gary Geunbae , Cha Jeongwon , Lee Jong-Hyeok
Published: August 2003

Most errors in Korean morphological analysis and part-of-speech (POS) tagging are caused by unknown morphemes. This paper presents a syllable-pattern-based generalized unknown-morpheme-estimation method with POSTAG (POStech TAGger), 1 which is a statistical and rule-based hybrid POS tagging system. This method of guessing unknown morphemes is based on a combination of a morpheme pattern dictionary that encodes general lexical patterns of Korean morphemes with a posteriori syllable trigram estimation. The syllable trigrams help to calculate lexical probabilities of the unknown morphemes and are utilized to search for the best tagging result. This method can guess the POS tags of unknown morphemes regardless of their numbers and/or positions in an eojeol (a Korean spacing unit similar to an English word), which is not possible with other systems for tagging Korean. In a series of experiments using three different domain corpora, the system achieved a 97% tagging accuracy even though 10% of the morphemes in the test corpora were unknown. It also achieved very high coverage and accuracy of estimation for all classes of unknown morphemes.

1 The binary code of POSTAG is open to the public for research and evaluation purposes at http://nlp.postech.ac.kr/. Follow the link OpenResources→DownLoad.
Sexual Satisfaction in Young Adulthood
Authors: Pedersen Willy , Blekesaune Morten
Published: August 2003

It has been suggested in several studies that marriage provides the best framework for a sexual relationship. During the past few decades, however, the majority of young singles have maintained a partnered sex life, and marriage has given way to cohabitation as the typical way for heterosexual couples to live together in young adulthood. Taking a longitudinal population-based sample of young Norwegian adults ( n = 2695, age 20-26), we investigated the degree to which sexual satisfaction was associated with the type of relationship in which they were engaged. Among both males and females, the sexually active unattached were the least satisfied with their sex lives, and a committed and long-lasting relationship seemed to be of greater importance for women than for men. In these relationships, however, a decrease in sexual activity and sexual satisfaction was observed over time, suggesting that boredom and routine may rapidly decrease sexual satisfaction. Most striking was the finding that females seem to profit in their sexual relationships from traditionally feminine and masculine gender roles in the form of androgyny. Men, on the other hand, still seem to manoeuvre on the basis of less flexible gender roles.
Development of a Numerical Model to Predict In-Plane Heat Generation Patterns During Induction Processing of Carbon Fiber-Reinforced Prepreg Stacks
Authors: Kim Hee June , Yarlagadda Shridhar , Shevchenko Nicholas B. , Fink Bruce K. , Gillespie John W.
Published: August 2003

A numerical model is proposed to describe in-plane heat generation spatial response during induction processing of carbon fiber-reinforced thermoplastics. The model is based on a unified approach that considers three possible heating mechanisms: fiber heating (Joule losses in fiber), noncontact junction heating (dielectric hysteresis), and contact junction heating (Joule losses at junctions). A lumped meshing scheme is used to construct a numerical representation for cross-ply and angle-ply orientations of 2-ply prepreg stacks. Heat generation patterns are calculated based on voltage and current conservation laws and verified with induction heating of AS4 carbon fiber-reinforced polyetherimide (AS4/PEI) prepreg stacks. Excellent agreement is found except at very low angle-ply orientations where the predicted heating patterns show significant deviations from the experiment results. A sensitivity analysis is also performed to assess the relationship between heating patterns and material and process parameters. The results show that the stack angle between plies and intrinsic prepreg microstructure can significantly affect the heating patterns.
Gas Flow Method for Detecting Local Preform Defects by Inverse Estimation of Space-Varying Permeability
Authors: Kim Sun K. , Opperer Jeremy G. , Daniel Isaac M.
Published: August 2003

A method using gas flow is proposed for testing the quality of fibrous preforms in the resin transfer molding process. The method is based on the idea that preform defects cause variation in permeability and deviation from Darcy's law. This paper presents a gradient-based inverse method that estimate space-varying permeability by examining the consistency between computed and measured pressures at various locations in the mold during steady-state gas flow through the enclosed preform. Such consistency is achieved by the conjugate gradient method. The computed pressures are obtained by the control volume finite element method (CVFEM). The proposed method was demonstrated by using a specially designed mold with multiple ports for gas injection and pressure measurement, and testing for various cases with and without defects.
Beyond Translation... Cultural Fit
Authors: Hendrickson Sherry Garrett
Published: August 2003

Reaching non-English-speaking families, the economically disadvantaged, and those who are disproportionately represented in disease and injury statistics is challenging. This article describes the process of making a questionnaire developed in English, culturally appropriate for low-income, monolingual, Mexican and Mexican American mothers. The questionnaire, guided by the Health Belief Model, assesses maternal childhood injury health beliefs and was originally used with a 96% African American, English-speaking sample in the Eastern United States. Two research assistants from the target population worked with the non-Hispanic, bilingual investigator to redesign the questionnaire’s language and presentation and to collect data. Sixty monolingual Latina mothers participated in the study to determine the internal consistency of the 42-item Spanish language Maternal Childhood Injury Health Belief Questionnaire (MCIHB). Cronbach’s alpha coefficients ranged from .76 (Benefits subscale) to .90 (Consequences subscale).
Differences between Gay and Lesbian Cohabiting Couples
Authors: Kurdek Lawrence A.
Published: August 2003

Partners from gay and lesbian couples were compared on variables from four domains relevant to close relationships (individual differences, relationship beliefs/attitudes, conflict resolution, and social support); change in relationship quality over time; relationship dissolution; and the correlates of relationship satisfaction and relationship dissolution. Participants completed mailed surveys at least once over 14 assessments, n= 80 gay couples and 53 lesbian couples at the first time assessment with additional couples recruited at later assessments. Although few type-of-couple differences were significant, partners from lesbian couples reported more positive beliefs/attitudes about relationships, as well as more positive relationship satisfaction.
Lying, Cheating, Complaining, and Other Aversive Interpersonal Behaviors: A Narrative Examination of the Darker Side of Relationships
Authors: Kowalski Robin M. , Walker Sherri , Wilkinson Rachel , Queen Adam , Sharpe Brian
Published: August 2003

People do a lot of mean and nasty things to one another. Collectively, these behaviors are referred to as aversive interpersonal behaviors. To examine the structural elements of different aversive interpersonal behaviors and individual differences in perceptions of those behaviors, 96 male and 149 female students each wrote a victim narrative and a perpetrator narrative about one of seven aversive behaviors: betrayal, lying, improprieties, teasing, complaining, arrogance, and dependency. Significant victim/perpetrator differences were obtained, but, importantly, they were influenced by the particular aversive behavior being examined. Relative to perpetrators, victims perceived betrayal, lying, teasing, and arrogance more negatively. Victims and perpetrators did not differ in their evaluations of complaining and dependency. In addition, differences among victims and among perpetrators were obtained such that victims evaluated the behaviors of betrayal, lying, and arrogance as more aversive than the other behaviors. Perpetrators reported feeling more guilt when they had perpetrated a betrayal than when they had complained or engaged in excessive reassurance-seeking. Implications of these differences for relationships are discussed.
Couple Perceptions of Their Similarities and Differences: A Dialectical Perspective
Authors: Baxter Leslie A. , West Lee
Published: August 2003

This interview study of 27 friendship and 14 romantic pairs examined the dialectical unity of two contradictions: similarity/difference and positivity/negativity. Relationship partners were able to identify phenomena upon which they were similar and upon which they were different. In addition, partners identified phenomena upon which they were both similar and different. Partners were able to identify similarities and differences that were positively valenced in addition to those that were negatively valenced; also, partners identified similarities and differences that were both positive and negative. Similarities and differences involved five kinds of phenomena: personality, leisure pursuits, attitudes and beliefs, communication style, and demographic/family background. Similarities were positive because they were perceived to facilitate communication, provide pleasure/fun, and provide assistance/support. Differences were positive because they contributed to individual growth and the facilitation of communication. Similarities and differences were negative because they resulted in conflict or other challenges to communication.
Relational Well-Being and Perceptions of Relational History in Married and Dating Couples
Authors: Flora Jeanne , Segrin Chris
Published: August 2003

This study examined how participants perceive their relational history with their current partner, and how those perceptions predicted relational well-being in 66 dating and 65 married couples. Perceptions of relationship development history were assessed through (1) coding of cognitive appraisals in the Oral History Interview and (2) self-reports from a measure of Relationship Development Breadth, which documented whether participants experienced certain thoughts, feelings, or behaviors typical of relationship development. Relational well-being was operationalized as relational satisfaction and stability, and was measured both concurrently and at a six-month follow-up. Greater Time 1 relational well-being was explained by reports of greater relationship development breadth and more positive oral history appraisals. Lower Time 2 satisfaction and Time 2 break-up (stability) were related to reports of little relational development breadth and negative oral history appraisals made by females. The results indicated similar patterns in the oral history appraisals of married and dating couples. In addition, the Relationship Development Breadth measure demonstrated good concurrent and predictive validity.
Are Argumentative People Better or Worse at Seeing Both Sides?
Authors: Frantz Cynthia McPherson , Seburn Mary
Published: August 2003

This study investigated the relationship between argumentativeness and perspective taking in interpersonal conflicts. Previous research suggests that those high in argumentativeness may be more open-minded and able to see both sides of an argument than those low in argumentativeness. However, their chronic motivation to argue may lead them to respond less evenhandedly to arguments in which they possess a strong personal preference. Participants high and low in argumentativeness responded open-endedly to two conflicts differing in degree of personal preference. High argumentatives were more evenhanded in the low-preference conflict than were low argumentatives, but less evenhanded in the high-preference conflict. Results highlight the importance of underlying preferences and motivations in perspective taking, as well as the importance of underlying mechanisms for predicting situation–personality interactions.
Path Planning for Robotic Demining: Robust Sensor-Based Coverage of Unstructured Environments and Probabilistic Methods
Authors: Acar Ercan U. , Choset Howie , Zhang Yangang , Schervish Mark
Published: August 2003

Demining and unexploded ordnance (UXO) clearance are extremely tedious and dangerous tasks. The use of robots bypasses the hazards and potentially increases the efficiency of both tasks. A first crucial step towards robotic mine/UXO clearance is to locate all the targets. This requires a path planner that generates a path to pass a detector over all points of a mine/UXO field, i.e., a planner that is complete .The current state of the art in path planning for mine/UXO clearance is to move a robot randomly or use simple heuristics . These methods do not possess completeness guarantees which are vital for locating all of the mines/UXOs. Using such random approaches is akin to intentionally using imperfect detectors. In this paper, we first overview our prior complete coverage algorithm and compare it with randomized approaches. In addition to the provable guarantees, we demonstrate that complete coverage achieves coverage in shorter time than random coverage. We also show that the use of complete approaches enables the creation of a filter to reject bad sensor readings, which is necessary for successful deployment of robots. We propose a new approach to handle sensor uncertainty that uses geometrical and topological features rather than sensor uncertainty models. We have verified our results by performing experiments in unstructured indoor environments. Finally, for scenarios where some a priori information about a minefield is available, we expedite the demining process by introducing a probabilistic method so that a demining robot does not have to perform exhaustive coverage.
Manipulability of Wheeled Mobile Manipulators: Application to Motion Generation
Authors: Bayle B. , Fourquet J. -Y. , Renaud M.
Published: August 2003

We propose a systematic modeling of the nonholonomic mobile manipulators built from a robotic arm mounted on a wheeled mobile platform. We use the models derived to generalize the standard definition of manipulability to the case of mobile manipulators. The effects of mounting a robotic arm on a nonholonomic platform are shown through the analysis of the manipulability thus defined. Several applications are evoked, particularly applications to control. The optimization of criteria inherited from manipulability considerations are given to generate the controls of our system when its end effector motion is imposed.
Electro-Oculographic Guidance of a Wheelchair Using Eye Movements Codification
Authors: Barea R. , Boquete L. , Bergasa L. M. , López E. , Mazo M.
Published: August 2003

In this paper we present a new method to guide mobile robots. An eye-control device based on electro-oculography (EOG) is designed to develop a system for assisted mobility. Control is made by means eye movements detected using electro-oculographic potential. Using an inverse eye model, the saccadic eye movements can be detected and know where the user is looking. This control technique can be useful in multiple applications, but in this work it is used to guide a wheelchair for helping people with severe disabilities. The system consists of a standard electric wheelchair, an on-board computer, sensors and a graphical user interface. Finally, we comment on some experimental results and conclusions about electro-oculographic guidance using ocular commands.
Interfacial Phenomena of Newspaper Fiber-Reinforced Polypropylene Composite, Part I: The Development of Interfacial Interaction
Authors: Hon David N.-S. , Ren Shan
Published: August 2003

In the process of developing interfacial interaction between newspaper fiber (NPF) and polypropylene (PP) by an intensive mixing, the morphological and microstructural characteristics which influence the mechanical behavior of the mixture were investigated by means of a scanning electron microscope (SEM) and a rheometer. The effects of mixing temperature and moisture content in the NPF on the mechanical behavior were elucidated.

The development of interfacial interaction took place in two stages, in which the first stage took place over a relatively short time. In this stage, the fiber was not uniformly dispersed in the melted PP matrix. A fully developed interfacial interaction was not developed until the second stage. In this stage, the fiber was uniformly dispersed into the matrix and coated with PP. The mechanical strength of the composite was maximized in the second stage of mixing.
Tow Impregnation of Unidirectional Fibrous Preform During Resin Transfer Molding
Authors: Chang Chih-Yuan
Published: August 2003

The flow pattern determines the formation and distribution of the voids, and subsequently the quality of the products during the mold filling of RTM. A model is developed to simulate the interaction between the flow in the gaps around the fiber bundles and the flow inside the fiber bundles. Brinkman's equation is used to calculate the flow fields inside the fiber bundles, while the Stokes approximation is used to simplify the resin flow equation in the gaps. Results show that the mechanism of air entrapment is formed inside the fiber bundles. A boundary layer occurs along the permeable interface of the fiber bundles. The thickness of the boundary layer increases with larger permeability and larger gap size. The thickness of the boundary layer is about O(K½). For flow outside of boundary layer regions the Brinkman's equation can reduce to the Darcy's law.
Active Stiffening and Active Damping Effects on Closed Loop Vibration Control of Composite Beams and Plates
Authors: Raja S. , Sinha P. K. , Prathap G.
Published: August 2003

The influences of active stiffening (displacement control) and active damping (velocity control) effects introduced by collocated piezoelectric actuators and sensors on vibration control of composite structures are studied in this paper. A nine-node piezoelectric plate finite element is derived using the first order shear deformation theory to model the distributed actuation and sensing numerically. An output feedback control strategy is developed with the linear quadratic regulator theory in modal domain to estimate the optimal gains for different control efforts off line. Further, the developed control procedure is realised experimentally in an active control system. As an illustration, the effects of both displacement and velocity controls are shown on a CFRP beam. A periodic excitation is applied as disturbance and the amplitude response control is achieved by controlling the displacement and velocity of the vibrating system. It is observed that the active stiffening effect through displacement control is more effective for modes that have the amplitude of vibration relatively high. However, the active damping effect introduced by velocity control is efficient in the third mode control, which shows that a small amount of active damping is sufficient to stabilise a mode having comparatively less amplitude of vibration. Influence of active stiffening on the closed loop system frequency is observed to be more than that of active damping effect.
Elastic Properties of PEEK/IM7 Related to Temperature
Authors: Melo Jose Daniel D. , Radford D. W.
Published: August 2003

An approach using laminate Coefficient of Thermal Expansion (CTE) measurements and two measured elastic constants is applied to predict the elastic properties of PEEK-IM7 prepreg laminae. This study assesses the feasibility of the use of this method to compute elastic properties over a range of temperatures. Three-dimensional elastic constants of PEEK/IM7 are determined for the temperature range of 20°Cto 120°C. The results indicate good agreement with quoted values measured by standard techniques, at room temperature. Moreover, the technique allows the study of the temperature dependence of the elastic properties over a range of temperatures. Thus, the technique demonstrates an ability to generate elastic properties data for a transversely isotropic material, over a wide temperature range, which ultimately can be used for improved performance prediction of structural composites.
Flexible Polyurethane Foams: Flammability
Authors: Lefebvre Jérôme , le Bras Michel , Bastin Benoît , Paleja Rakesh , Delobel René
Published: August 2003

Polyurethane flexible foam is a very versatile, high quality cushioning material. By its chemical nature, polyurethane foam is a combustible material. Test methods have been progressively introduced to classify the fire behaviour of foam and legislation based on these tests has been introduced in various countries to ensure that the foam complies with these fire standards. A notable example of this is British Standard 5852 on which the United Kingdom bedding and furniture legislation is based. The influence of formulation variables such as the type and particle size of the filler, the foam density, the air flow (openness) are some of the well documented parameters. Another important variable is the liquid flame retardant (halogenated phosphate type) which is the objective of the present study. This paper provides a basic understanding of foam combustibility based on the British Standard 5852 test method. Dynamic weight loss made with two types of liquid flame retardants with and without melamine is used to provide this understanding. Thermogravimetric analysis and cone calorimeter have been used to support the discussion. In melamine free foams, our study has shown that the decomposition temperature of the liquid flame retardant is a key parameter, which governs the foam combustion. In melamine containing foams, the overall combustion behavior is dependant on the type of liquid flame retardant used. However, intrinsic differences do exist and synergy is seen between melamine and liquid flame retardant under specific conditions. Applying this basic understanding and the actual combustion standards, foam producers can attain flexibility in designing cost effective foam formulations.
A Debate on Heat Transfer Analysis in Domestic Flues
Authors: Jones J. C.
Published: August 2003

The Forum is intended to provide for dialogue and discussion among fire experts, scientists and consultants. Contributions to The Forum will not be refereed in the conventional sense, but will be subject to review by the Editor or a member of the Journal's Editorial Board relative to appropriateness, clarity, timeliness, and scope of interest. The Editor will be the sole judge of those contributions to be published. Opinions expressed, however, are those of the authors and not of the Editor or Sage Publications Ltd.
Polymeric Drug for Antimicrobial Activity Studies: Synthesis and Characterization
Authors: Arun A. , Reddy B. S. R. , Rajkumar M.
Published: August 2003

In this study, 2′,4-dichloro-5′-fluoro-1-ene-2-(4-hydroxyphenyl)phenone (EHP) was synthesized using 4-hydroxybenzaldehyde and 2, 4-dichloro-5-fluoro acetophenone (DFA); 4-[3-(2,4-dichloro-5-fluorophenyl)-3-oxoprop-1-en-1-yl]phenyl acrylate (EAP) was prepared by reacting EHP with acryloyl chloride. Poly(EAP) was prepared by solution polymerization and was characterized by IR, 1H and 13C NMR. The molecular weights of the polymer (EAP) (Mw: 3900 and Mn: 3600) were characterized by gel permeation chromatographic. Thermal stability of the polymer was characterized by thermogravimetric analysis method. Antimicrobial activity of the DFA, EHP, EAP and poly(EAP) were tested on three microorganisms; Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Salmonella typhi ATCC 6539. The minimum concentration of the drug needed to inhibit the growth of the bacteria was estimated using a photometry assay.
Influence of Quaternized Polyurethane Membrane Surfaces on Human Endothelial Cell Attachment and Growth
Authors: Hong Yi , Gao Changyou , Guan Jianjun , Shen Jiacong
Published: August 2003

Poly(ester urethane) (PU) membranes with cationic groups on the surface was prepared by grafting N,N-dimethylaminoethyl methacrylate (DMA), followed by quaternization with iodomethane. Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy, X-ray photo-eletron spectroscopy (XPS) and scanning electron microscopy (SEM) evaluations verified the occurrence of the grafting polymerization and the quaternization. The endothelial cell attachment, viability, proliferation and morphology were investigated by in vitro cultures of the cationic membrane (PU-g-PDMAQ). The results show that the cytocompatibility of the cationic membrane with a specific amount of PDMAQ was improved. However, compared with its precursor, the PDMA grafted membrane (PU-g-PDMA), the cytocompatibility was not very different. These results suggest that the positive charges do not significantly improve the cytocompatibility to endothelial cells in comparison with the PU-g-PDMA neutral surface.
EGF Loaded Chitosan Sponges as Wound Dressing Material
Authors: Denkbas Emir B. , Öztürk Eylem , Özdemi Nalan , Keçeci Kaan , Ergün M. Ali
Published: August 2003

The aim of this study was to prepare and characterize chitosan sponges using epidermal growth factor (EGF) for wound healing. Chitosan sponges were prepared by solvent evaporation (or precipitation) combined with chemical cross-linking techniques. The chitosan polymer was weighed and dissolved in aqueous acetic acid solution (5% v/v) and injected into absolute ethanol containing a cross-linker (ethylene glycol diglycydyl ether). The growth factor (EGF) was loaded into sponges by adding it into the chitosan solution. The EGF loaded chitosan sponges were used in fibroblast cell culture studies to investigate the effects of EGF released on cell proliferation and to determine the effects of the different variables on EGF release; such as, chitosan Mw, cross-linker, the needle injecting the chitosan solution into the precipitation medium, chitosan/EGF ratio and pH of the medium. The swelling of the sponges was higher in the lower molecular weight chitosan, with less cross-linker and using a small diameter injection needle. The swelling increased with decreasing chitosan/EGF ratio and the EGF release rate was increased by increasing the sponge swelling. The cell proliferation (cell growth) increased with increasing swelling ratio.
Strategies For Managing Multiple Organizational Identifications
Authors: Larson Gregory S. , Pepper Gerald L.
Published: August 2003

This case study reveals how organization members communicatively manage multiple targets and sources of identification during a time of company transition. Interview accounts are used to examine how members discursively construct understanding as they discuss two competing value-based identity structures. Results reveal three distinct discursive strategies—comparison, logic, and support—that members use to manage identity tensions, and eight corresponding communicative tactics used to enact those strategies. This focus on communicative strategies and tactics is important because identities are expressed through language, and discourse is the means available to organization members for negotiating various identity structures. Discursive strategies are central to the identity formation process and provide a window into the sensemaking of participants.
The Dilemma of Social Democracy in 1914
Authors: Herreros Francisco
Published: August 2003

In 1914, socialist parties voted in favour of war credits. This was a surprising decision given their pre-war commitment to the keeping of peace. The decision has usually been explained by the so-called chauvinist preferences of the socialist leaders. In this article, an alternative hypothesis is advanced. A game theoretic model is used to explain why socialist parties betrayed their pre-war commitments. It is maintained that the socialist parties' voting decision is compatible with pacifist preferences. The game theoretic model indicates that socialist parties were trapped in a coordination problem that they could not solve. They voted in favour of war credits even though they were pacifists because they could not coordinate themselves in a joint negative vote. This conclusion goes against the common perception of historical fact.
Policy-Making by Different Means
Authors: Nixon David C.
Published: August 2003

Formal theories of majority voting suggest that the organizing rules of the Judicial Conference of the United States (JCUS) present the Chief Justice of the Supreme Court with the opportunity to sway the policy statements of the JCUS in favor of his preferred language. Existing political science literature on the Chief Justice demonstrates that Chiefs use their authority to pursue their policy agendas in a variety of other settings. The membership of the JCUS Executive Committee - a particularly important committee in the Conference - is examined over the 1970-98 period. Both Chiefs during this period consistently stacked the committee with conservative policy outliers, and did so in a sophisticated strategic fashion.
The Role of Intrahousehold Bargaining in Gender Discrimination
Authors: Ishida Junichiro
Published: August 2003

Two alternative intrahousehold resource allocation rules are considered and the role of intrahousehold bargaining in gender discrimination is explained. A model is constructed in which male and female agents interact at the household level in the form of marriage. It is shown that an asymmetric equilibrium in which male and female agents behave differently exists under either rule, but that welfare implications of the model depend critically on the nature of intrahousehold resource allocation. The asymmetric equilibrium is strictly welfare-reducing for female agents when total output is divided through Nash bargaining, but not when each household acts as one utility-maximizing unit. The model indicates that the nature of intrahousehold resource allocation has critical policy implications.
Shape Control with Karhunen-Loéve-Decomposition: Theory and Experimental Results
Authors: Zhang Weihua , Michaelis Bernd
Published: August 2003

The Finite Element Method is a powerful method that can be used to describe the dynamic behavior of mechanical systems. The most crucial problem to use this method is the large degree of freedom in FE-models. It is very difficult or even impossible to design controllers. Consequently, it is necessary to reduce the model. However, the model reduction deals only with the state variables, therefore the model reduction is not sufficient for the shape control, because a great number of reference and measured data are needed for the shape description and control.

In [Zhang, W. and Michaelis, B. 2000. “Shape Control with Karhunen-Loève-Decomposition,” 11th Int. Conference on Adaptive Structures and Technologies, Nagoya, Japan, October 23-26, pp. 119-126.], we have developed a new method using the Karhunen-Loève-Decomposition to realize the shape control. In this paper, we will first give the theory briefly and then the experimental results.
Topology Optimization Applied to The Design of Linear Piezoelectric Motors
Authors: Silva Emílio Carlos Nelli
Published: August 2003

Topology optimization is a general computer design method applied to design optimal topology of structures that maximizes (or minimizes) a specified objective function (stiffness, for example) according to some constraints (such as volume). In this work, topology optimization is applied to design linear piezoelectric motors. These motors consist essentially of a flexible structure actuated by two or more piezoceramics excited with different phases. The actuated piezoceramics deform the flexible structure which moves due to friction over a fixed structure, called stator. The flexible structure acts as a mechanical transform by amplifying and changing the direction of the output displacement generated by piezoceramics. The objective is to develop a method which allows us to design systematically a flexible structure for a linear piezoelectric motor taking into account its performance for a given configuration of piezoceramics. This performance is related to the displacement generated in the motor moving direction and clamping force between the flexible structure and stator. Both quantities depend on the distribution of flexibility and stiffness in the flexible structure domain, which is related to its topology. By designing other types of flexible structures connected to the piezoceramics, novel types of linear piezoelectric motors can be obtained. Only quasi-static applications of motors are considered. The design of an “inchworm-type” piezoelectric motor is presented to illustrate the implementation of the method.
Computer Support for Systematic Design Applied in a Cross-functional Commercial Concept Development Project
Authors: Almefelt Lars , Sutinen Krister , Malmqvist Johan
Published: August 2003

In this paper, an empirical study aiming at exploring the practical applicability of a computer support for systematic design methodology is presented. During a six-month project, a cross-functional product development team in the automotive industry was studied using an action-based research approach. The team applied a systematic design methodology and used a computer tool that provides support for systematic design. In this paper we set out our conclusions on the effects of the methodology and tool with regard to creativity, quality, time consumption, and the work process of the team. In addition, suggestions for future development of systematic design tools are listed. Finally, recommendations for the application of systematic design in industry are given.