bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dielectric properties of oxydianiline‐based polyimide thin films according to the water uptake
Authors: Lee Choonkeun , Shul Yonggun , Han Haksoo 
Published: September 2002

AbstractFor polyimide thin films, the dielectric properties were investigated with the capacitance and optical methods. The dielectric constants of the 4,4′‐oxydianiline (ODA)‐based polyimide thin films varied from 2.49 to 3.10 and were in the following decreasing order: 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA)–ODA > 1,2,4,5‐benzenetetracarboxylic dianhydride (PMDA)–ODA > 4,4′‐hexafluoroisopropylidene diphthalic dianhydride (6FDA)–ODA. According to the absorption of water, the diffusion coefficients in the films varied from 4.8 × 10−10 to 7.2 × 10−10 cm2/s and were in the following increasing order: BPDA–ODA < PMDA–ODA < 6FDA–ODA. The dielectric constants and diffusion coefficients of the polyimides were affected by the morphological structures, including the molecular packing order. However, because of the water uptake, the changes in the dielectric constants in the polyimide thin films varied from 0.49 to 1.01 and were in the following increasing order: BPDA–ODA < 6FDA–ODA < PMDA–ODA. Surprisingly, 6FDA–ODA with bulky hexafluoroisopropylidene groups showed less of a change in its dielectric constant than PMDA–ODA. The total water uptake for the polyimide thin films varied from 1.43 to 3.19 wt % and was in the following increasing order: BPDA–ODA < 6FDA–ODA < PMDA–ODA. This means that the changes in the dielectric constants in the polyimide thin films were significantly related to the morphological structure and hydrophobicity of hexafluoroisopropylidene groups. Therefore, the morphological structure and chemical affinity in the polyimide thin films were important factors in controlling the dielectric properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2190–2198, 2002
Studies on the phase structure of ethylene‐vinyl acetate copolymers by solid‐state 1H and 13C NMR
Authors: Zhang Qiujin , Lin Weixin , Yang Guang , Chen Qun 
Published: September 2002

AbstractThe phase structure of a series of ethylene‐vinyl acetate copolymers has been investigated by solid‐state wide‐line 1H NMR and solid‐state high‐resolution 13C NMR spectroscopy. Not only the degree of crystallinity but the relative contents of the monoclinic and orthorhombic crystals within the crystalline region varied with the vinyl acetate (VA) content. Biexponential 13C NMR spin–lattice relaxation behavior was observed for the crystalline region of all samples. The component with longer 13C NMR spin–lattice relaxation time (T1) was attributed to the internal part of the crystalline region, whereas the component with shorter 13C NMR T1 to the mobile crystalline component was located between the noncrystalline region and the internal part of the crystalline region. The content of the mobile crystalline component relative to the internal part of the crystalline region increased with the VA content, showing that the 13C NMR spin–lattice relaxation behavior is closely related to the crystalline structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2199–2207, 2002
Sulfobetaine zwitterionomers based on n‐butyl acrylate and 2‐ethoxyethyl acrylate: Physical properties
Authors: Gauthier Mario , Carrozzella Tony , Snell Greg 
Published: September 2002

AbstractNew materials with potential applications for adhesives and coatings, based on copolymers containing zwitterionic pendent groups, were investigated. n‐Butyl acrylate and 2‐ethoxyethyl acrylate were copolymerized with a series of five zwitterionic sulfobetaine monomers (SBMs). The structures of the SBMs were varied systematically in terms of (1) intercharge spacing in the zwitterionic moiety and (2) substituent bulkiness at the quaternary ammonium functionality. The effect of varying the sulfobetaine content and structure in the copolymers was investigated, with an emphasis on ion aggregation behavior and physical properties, with dynamic mechanical analysis. The zwitterionomers exhibited the expected biphasic morphology, with the appearance of an ion‐rich glass‐transition temperature. An increase in the storage modulus was observed with increasing SBM content in the rubbery and terminal regions, suggesting an increased degree of ionic crosslinking in the rubbery region and decreased chain mobility in the flow region. Intercharge spacing variation in the sulfobetaine moiety did not have a significant effect on the modulus–temperature curves, contrary to our expectations. Increases in the modulus were much less pronounced for the bulkier SBMs than for the other monomers, possibly because of hindered aggregation of the sulfobetaine moieties. Likewise, matrix polarity had a greater influence on the physical properties of these materials than intercharge separation in the SBMs. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2303–2312, 2002
Effect of benzenesulfonamide plasticizers on the glass‐transition temperature of semicrystalline polydodecamide
Authors: De Groote Ph. , Devaux J. , Godard P. 
Published: September 2002

AbstractThe effect of various benzenesulfonamide (BSA) plasticizers on the amorphous phase of semicrystalline polydodecamide (PA‐12) has been investigated. MonoBSAs appear as efficient glass‐transition temperature (Tg) depressors because of their miscibility with the host polyamide (PA), low glass transition, and small molecule size. PA‐12's Tg shifts from 50 to about 0 °C at 20 mol % of the most efficient molecules. Comparatively, the more bulky bisBSAs appear to induce less important absolute Tg decreases (30 K at 20 mol %), although these appear as more important when considering the polymer Tg to plasticizer Tg difference. This unexpected observation could be ascribed to both the amide‐sulfonamide interactions and the sterically generated disorder within the polyamide because of the plasticizer molecule's size. Phase‐separation behavior of BSA plasticizers within the host PA has also been investigated. Crystalline phenyl‐SO2NH2, for instance, dephased beyond 20 mol % in PA‐12, forming distinct 1–2 micrometer wide crystalline domains as a result of its high propensity to crystallize upon cooling from the melt. By contrast, slow crystallizing N,N‐dimethylBSA, which lacks any specific interaction for PA‐12, remained nevertheless dispersed at a molecular level (metastable state, no phase separation) when vitrification of the host PA‐12 amorphous phase occurred on cooling. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2208–2218, 2002
Nafion®/(organically modified silicate) nanocomposites via polymer in situ sol–gel reactions: Mechanical tensile properties
Authors: Young S. K. , Mauritz K. A. 
Published: September 2002

AbstractA series of Nafion®/[organically modified silicate (ORMOSIL)] hybrid materials have been created by in situ sol–gel copolymerizations of tetraethylorthosilicate and semiorganic silicon alkoxide monomers. The trends in the mechanical tensile properties of these hybrid materials were largely rationalized in terms of the entrapment of the long sulfonic acid side chains in silicate or ORMOSIL structures. There is a significant increase in the mechanical strength relative to that of unfilled Nafion®, except in one case. Young's modulus is enhanced relative to that of unfilled acid form Nafion® in a number of cases, although the degree of ductility is reduced relative to that of unfilled Nafion®. The filler fractions are beneath a critical value that would reflect percolation of a glassy, direct load‐bearing silicate phase. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2237–2247, 2002
Modeling the failure of an adhesive layer in a peel test
Authors: Lin Y. Y. , Hui C. Y. , Wang Y. C. 
Published: September 2002

AbstractThe failure of an adhesive layer in a 180° peel test is analyzed by the modeling of the peel as an elastica. The adhesive is assumed to fail by a process of cavitation and fibrillation. The resistance of the fibrillated material to deformation gives rise to a rate‐dependent peel force F. Governing equations, which take into account the large deformation of the fibrillated materials, are derived. Numerical solutions are obtained for the special case of a linear, viscous adhesive. Assuming a critical strain failure criterion for the fibrils, we show that the peel rate is inversely proportional to the square root of the adhesive thickness and directly proportional to F3/4. The connection between the peel test and the tack test is also discussed. The maximum traction on the peel arm is found to be directly proportional to the peel force and inversely proportional to the adhesive thickness. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2277–2291, 2002
Influence of a mixing solvent with tetrahydrofuran and N,N‐dimethylformamide on electrospun poly(vinyl chloride) nonwoven mats
Authors: Lee Keun Hyung , Kim Hak Yong , La Young Min , Lee Douk Rae , Sung Nak Hyun 
Published: September 2002

AbstractWe evaluated the effects of the solvent composition with respect to the solution concentration, applied electric field, and tip‐to‐collector distance on the morphology of electrospun poly(vinyl chloride) (PVC) fibers. The solvent volume ratio was strongly correlated with the diameter of the electrospun fibers with respect to the other processing parameters. Electrospun PVC fibers dissolved in tetrahydrofuran (THF) had diameters ranging from 500 nm to 6 μm; those dissolved in N,N‐dimethylformamide (DMF) had an average diameter of 200 nm. The diameters of the electrospun fibers were obtained from narrow to broad distributions with the solvent composition. Also, the diameters of fibers electrospun from a mixed solvent of THF and DMF were less than 1 μm. The mechanical properties of electrospun PVC nonwoven mats depended on the fiber orientation and linear velocity of the drum surface. With increasing linear velocity of the drum surface, electrospun PVC fibers were arranged toward the machine direction, and the dimensions of the spiral path were shorter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2259–2268, 2002
Mechatronics design of stiffness enhancement for direct‐drive motor system using ER variable damper
Authors: Su Y. X. , Duan B. Y. , Zheng C. H. 
Published: September 2002

AbstractDirect‐drive (DD) motors have the characteristics of simple structure and high controllability without reduction gears or ball screws. However, DD motors are more sensitive to the disturbance torque and parameter variation than other motor systems, which have reduction gears. Enhancement of DD motor stiffness by increasing the gain is one of the effective methods to reduce this influence, but large gain will lead to instability and even vibration. Viewed from mechatronics design, an ER variable damper with a damping coefficient that can be changed depending on how the applicable voltage is designed, and directly attached to the shaft of the DD motor to achieve high servo stiffness. The structure and the damping coefficient model of the proposed ER variable damper are developed. The validation of this mechatronics design is demonstrated by a position PD (proportional derivative) control DD motor system with numerical simulations, which achieved both high stiffness and good stability for the controlled DD motor system. © 2002 Wiley Periodicals, Inc.
Handling uncertainties of robot manipulators and active vision by constraint propagation
Authors: Yang Christopher C. , Ciarallo Frank W. , Marefat Michael M. 
Published: September 2002

AbstractJoint errors are inevitable in robot manipulation. These uncertainties propagate to give rise to translational and orientational errors in the position and orientation of the robot end‐effector. The displacement of the active vision head mounted on the robot end‐effector produces distortion of the projected object on the image. Upon active visual inspection, the observed dimension of a mechanical part is given dimension by the measurement on the projected edge segment on the image. The difference between the observed dimension and the actual dimension is the displacement error in active vision. For different motion of the active vision head, the resulting displacement errors are different. Given the uncertainties of the robot manipulator's joint errors, constraint propagation can be employed to assign the motion of the active sensor in order to satisfy the tolerance of the displacement errors for inspection. In this article, we define the constraint consistency and network satisfaction in the constraint network for the problem of displacement errors in active vision. A constraint network is a network where the nodes represent variables, or constraints, and the arcs represent the relationships between the output variables and the input variables of the constraints. In the displacement errors problem, the tolerance of the displacement errors and the translational and orientational errors of robot manipulators have interval values while the sensor motion has real values. Constraint propagation is developed to propagate the tolerance of displacement errors in the hierarchical interval constraint network in order to find the feasible robot motion. © 2002 Wiley Periodicals, Inc.
Extended Jacobian inverse kinematics algorithms for mobile manipulators
Authors: Tchoń Krzysztof , Jakubiak Janusz 
Published: September 2002

AbstractWe consider the inverse kinematic problem for mobile manipulators consisting of a nonholonomic mobile platform and a holonomic manipulator on board the platform. The kinematics of a mobile manipulator are represented by a driftless control system with outputs together with the associated variational control system. The output reachability map of the driftless control system determines the instantaneous kinematics, while the output reachability map of the variational system plays the role of the analytic Jacobian of the mobile manipulator. Relying on a formal analogy between the kinematics of stationary and mobile manipulators we exploit the extended Jacobian construction in order to design a collection of extended Jacobian inverse kinematics algorithms for mobile manipulators. It has been proved mathematically and confirmed in computer simulations that these algorithms are capable of efficiently solving the inverse kinematic problem. Moreover, a choice of the Jacobian extension may lay down some guidelines for the platform‐manipulator motion coordination. © 2002 Wiley Periodicals, Inc.
Science centers and scientific literacy: Promoting a relationship with science
Authors: Rennie Léonie J. , Williams Gina F. 
Published: September 2002

AbstractThis research explores the perceptions, ideas, and understanding about science of the staff and adult visitors to an interactive science center. Data were collected from 63 staff and 102 visitors through interviews and a survey designed for the study. Visitors' perceptions about science were more limited than those of the Center staff, especially in terms of the nature of science. For example, after their visit, visitors were more likely to think that scientists always agree with each other, that scientific explanations are definite, and that science has the answers to all problems. Staff were more skeptical than visitors about scientists' ability to communicate their work clearly and that scientific knowledge would not be misused. Staff were more positive and confident about their own use of science than were visitors. The research suggests that visitors to the science center have a positive experience, most of them recognize a change in the way they think about science, and this change represents not just learning new knowledge, but a step toward a change in their relationship with science. This outcome is consistent with one of the major roles the staff saw for the Center: that visitors should become more aware of and interested in science, and leave feeling more comfortable with it. Although the staff were very enthusiastic about what they saw as a positive impact on visitors' science‐related experience, many also felt there was room for improvement, especially in terms of how the nature of science was portrayed, and the representation of controversial aspects of science. © 2002 Wiley Periodicals, Inc. Sci Ed 86:706–726, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10030
Longitudinal impact of an inquiry‐based science program on middle school students' attitudes toward science
Authors: Gibson Helen L. , Chase Christopher 
Published: September 2002

AbstractThis study examined the long‐term impact of the Summer Science Exploration Program (SSEP), a 2‐week inquiry‐based science camp, conducted at Hampshire College Amherst, MA from 1992 to 1994. The goal of the program was to stimulate greater interest in science and scientific careers among middle‐school students. One hundred fifty‐eight students were selected from a pool of applicants to attend the program using stratified random sampling procedures. In 1996, 22 participants were selected to participate in follow‐up interviews using stratified random sampling procedures. Two quantitative surveys, the Science Opinion Survey and the Career Decision‐Making Revised Surveys, were administered to 79 SSEP students and 35 students who applied but were not accepted (the control group). Pretest and posttest scores were analyzed for any significant change over time. Additionally, a cohort of over 500 students who were enrolled in the same grades and public schools that SSEP students attended completed the two surveys in both 1992–1994 and 1996–1997. The interviews and surveys suggested that SSEP students maintained a more positive attitude towards science and a higher interest in science careers than students who applied to the program but were not selected. © 2002 Wiley Periodicals, Inc. Sci Ed 86:693–705, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10039
Strata of comprehending ecology: Looking through the prism of feeding relations
Authors: Eilam Billie 
Published: September 2002

AbstractThe present paper focuses on ninth graders' difficulties in learning ecology. Three dimensions, in addition to the macrolevel dimension, were identified as basic obstacles that might hinder students' meaningful learning of ecology: the microlevel dimension, relating to the molecular and micro processes of matter and energy transfer in ecosystems; the spatial dimension of ecosystems, regarding simultaneous occurrences in space and the multiple roles of their biotic elements; and the time dimension, relating to long‐term evolutionary forces acting in ecosystems. These four dimensions were examined in students' understanding of the concept of food chains in ecosystems. Four ninth grade classrooms participated in the study. Two of the classes studied ecology in the traditional mode and served as a control. Two classes were exposed to a novel, specifically designed learning context for ecology study, which integrated several elements known to influence learning, including a special curriculum to guide students' active involvement in a self‐regulated process of inquiry. A qualitative analysis of students' written responses and recorded verbal interactions was used, as well as simple quantitative methods. © 2002 Wiley Periodicals, Inc. Sci Ed 86:645–671, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10041
Automating the management of software maintenance workflows in a large software enterprise: a case study
Authors: Aversano Lerina , Canfora Gerardo , De Lucia Andrea , Stefanucci Silvio 
Published: September 2002

AbstractThis case study presents the results from a pilot project aimed at introducing workflow management technologies and a Web‐based software tool in a large software enterprise. In particular, we analyzed and modeled the workflows and documents at the site of the ordinary maintenance process and implemented a prototype for the management of the process using a commercial‐Web‐based workflow management system. This paper reports on the experience gained from a 10‐month project, which included the experimental use at a single site of the workflow prototype for 4 months in an industrial setting involving more than 800 maintenance service requests on a large software system. Copyright © 2002 John Wiley & Sons, Ltd.
State‐of‐the‐art: software inspections after 25 years
Authors: Aurum Aybuke , Petersson Håkan , Wohlin Claes 
Published: September 2002

AbstractSoftware inspections, which were originally developed by Michael Fagan in 1976, are an important means to verify and achieve sufficient quality in many software projects today. Since Fagan's initial work, the importance of software inspections has been long recognized by software developers and many organizations. Various proposals have been made by researchers in the hope of improving Fagan's inspection method. The proposals include structural changes to the process and several types of support for the inspection process. Most of the proposals have been empirically investigated in different studies.This is a review paper focusing on the software inspection process in the light of Fagan's inspection method and it summarizes and reviews other types of software inspection processes that have emerged in the last 25 years. This paper also addresses important issues related to the inspection process and examines experimental studies and their findings that are of interest with the purpose of identifying future avenues of research in software inspection. Copyright © 2002 John Wiley & Sons, Ltd.
An empirical evaluation of six methods to detect faults in software
Authors: So Sun Sup , Cha Sung Deok , Shimeall Timothy J. , Kwon Yong Rae 
Published: September 2002

Abstract Although numerous empirical studies have been conducted to measure the fault detection capability of software analysis methods, few studies have been conducted using programs of similar size and characteristics. Therefore, it is difficult to derive meaningful conclusions on the relative detection ability and cost‐effectiveness of various fault detection methods. In order to compare fault detection capability objectively, experiments must be conducted using the same set of programs to evaluate all methods and must involve participants who possess comparable levels of technical expertise. One such experiment was ‘Conflict1’, which compared voting, a testing method, self‐checks, code reading by stepwise refinement and data‐flow analysis methods on eight versions of a battle simulation program. Since an inspection method was not included in the comparison, the authors conducted a follow‐up experiment ‘Conflict2’, in which five of the eight versions from Conflict1 were subjected to Fagan inspection. Conflict2 examined not only the number and types of faults detected by each method, but also the cost‐effectiveness of each method, by comparing the average amount of effort expended in detecting faults. The primary findings of the Conflict2 experiment are the following. First, voting detected the largest number of faults, followed by the testing method, Fagan inspection, self‐checks, code reading and data‐flow analysis. Second, the voting, testing and inspection methods were largely complementary to each other in the types of faults detected. Third, inspection was far more cost‐effective than the testing method studied. Copyright © 2002 John Wiley & Sons, Ltd.