bluuebunny/crossref_metadata_2025 huggingface dataset:
PROCESS MANAGEMENT IN HIGH TECH NEW ZEALAND FIRMS
Authors: WOOD LINCOLN , LU QIANG
Published: July 2008

There are three distinct functions in the product realization chain — product design, process design, and process execution; thus there are two interfaces (product design — process design; process design — process execution) rather than one (product-manufacturing). Case studies of four organizations manufacturing high-tech products in New Zealand are explored to study the organization of process design functions and success strategies. Similarities in structuring, relationships between functional groups, and the methods for product and process design implementation are investigated. De-coupling of process design functions occurs best with high volume production with stable process technology — an infrequent situation with high-tech NZ manufacturers.
Akt and ERK1/2 pathways are components of the vasopressin signaling network in rat native IMCD
Authors: Pisitkun Trairak , Jacob Vinitha , Schleicher Stephen M. , Chou Chung-Lin , Yu Ming-Jiun , Knepper Mark A.
Published: July 2008

Vasopressin regulates water excretion through effects on the renal collecting duct. Vasopressin signaling in the inner medullary collecting duct (IMCD) is mediated by V2 receptor occupation coupled to the generation of cyclic AMP. Here, we employ a “systems” approach to analysis of vasopressin signaling. The objective is to investigate roles of activation of the Akt and ERK1/2 MAP kinase pathways, as well as Ca2+mobilization, in IMCD cells isolated from rat kidney. The V2 receptor-selective vasopressin analog dDAVP increased the state of Akt activation (increased phosphorylation at T308 and S473) and decreased the state of ERK1/2 activation (decreased phosphorylation at T202 and Y204). Akt activation was blocked by an inhibitor of PI3K, LY294002. In microdissected IMCD segments, nonperiodic spike-like increases in intracellular Ca2+(FLUO-4) were accelerated by vasopressin. Chelation of Ca2+or calmodulin inhibition markedly decreased Akt phosphorylation. Decreased ERK1/2 phosphorylation was associated with a decrease in MEK1/2 phosphorylation and an increase in c-Raf phosphorylation at S259 (an inhibitory site). Based on the current findings integrated with previous findings in the IMCD, we now report a 33-node vasopressin signaling network involved in vasopressin regulation of IMCD function.
Temporal and Spatial Allocation of Motor Preparation During a Mixed-Strategy Game
Authors: Mikulić Areh , Dorris Michael C.
Published: July 2008

Adopting a mixed response strategy in competitive situations can prevent opponents from exploiting predictable play. What drives stochastic action selection is unclear given that choice patterns suggest that, on average, players are indifferent to available options during mixed-strategy equilibria. To gain insight into this stochastic selection process, we examined how motor preparation was allocated during a mixed-strategy game. If selection processes on each trial reflect a global indifference between options, then there should be no bias in motor preparation (unbiased preparation hypothesis). If, however, differences exist in the desirability of options on each trial then motor preparation should be biased toward the preferred option (biased preparation hypothesis). We tested between these alternatives by examining how saccade preparation was allocated as human subjects competed against an adaptive computer opponent in an oculomotor version of the game “matching pennies.” Subjects were free to choose between two visual targets using a saccadic eye movement. Saccade preparation was probed by occasionally flashing a visual distractor at a range of times preceding target presentation. The probability that a distractor would evoke a saccade error, and when it failed to do so, the probability of choosing each of the subsequent targets quantified the temporal and spatial evolution of saccade preparation, respectively. Our results show that saccade preparation became increasingly biased as the time of target presentation approached. Specifically, the spatial locus to which saccade preparation was directed varied from trial to trial, and its time course depended on task timing.
Current Status of Gil-Vernet Trigonoplasty Technique
Authors: Simforoosh Nasser , Radfar Mohammad H.
Published: July 2008

Significant controversy exists regarding vesicoureteral reflux (VUR) management, due to lack of sufficient prospective studies. The rationale for surgical management is that VUR can cause recurrent episodes of pyelonephritis and long-term renal damage. Several surgical techniques have been introduced during the past decades. Open anti-reflux operations have high success rate, exceeding 95%, and long durability. The goal of this article is to review the Gil-Vernet trigonoplasty technique, which is a simple and highly successful technique but has not gained the attention it deserves. The mainstay of this technique is approximation of medial aspects of ureteral orifices to midline by one mattress suture. A unique advantage of Gil-Vernet trigonoplasty is its bilateral nature, which results in prevention from contralateral new reflux. Regarding not altering the normal course of the ureter in Gil-Vernet procedure, later catheterization of and retrograde access to the ureter can be performed normally. There is no report of ureterovesical junction obstruction following Gil-Vernet procedure. Gil-Vernet trigonoplasty can be performed without inserting a bladder catheter and drain on an outpatient setting. Several exclusive advantages of Gil-Vernet trigonoplasty make it necessary to reconsider the technique role in VUR management.
Vladimir Nabokov's Invitation to a Beheading or the Artifice of Mortality
Authors: Hasty Olga Peters
Published: July 2008

Invitation was one of Nabokov's favorite novels, written “in one fortnight of wonderful excitement and sustained inspiration.” Although it reads like an attack on dictatorial rule, Nabokov denied it political relevance, aiming at totalitarianism of a higher order: the constraints of mortality that he seeks, as the epigraph indicates, to refute: “Comme un fou se croit Dieu, nous nous croyons mortels.” The novel rebels against the certainty that life is movement toward death operating in conjunction with the uncertainty of when death will come. Its hero is condemned to execution, but denied “compensation for a death sentence”—the “knowledge of the exact hour when one is to die.” His nearing end is manifested metaphorically, but it is in the construction of the world of Invitation that Nabokov—whom one reviewer called “almost as much a theorizer of fiction as a practitioner”—develops narrative strategies that engage the reader in his challenge to mortality. This article considers his strategies.
Time in the Aesthetic Dimension of Visual Art
Authors: White Noel
Published: July 2008

In the spring of 2006 the English artist Noel White met the author J.T. Fraser while staying with friends near Cordoba, Spain. Lively discussion arose between them prompted by a reading of a paper by the social scientist Barbara Adam, which argues for the recognition of a moral dimension in political decisions. What follows here is an essay based on their conversation. The essay does not comment directly on Adam's arguments, but extends the question of the moral dimension to White's own area of expertise, the visual arts. Through an analysis of aspects of the history of modern painting it offers an understanding of morality in art, not as an added extra, to be permitted or not, but, if the making of a thing is to go beyond mere emotional expression, as integral to it. This conclusion is reached by showing how it is the moral dimension that underlies the early discoveries of modern painting, which at the same time links it with earlier forms of painting, but which was an aspect subsequently overlooked in the interpretation of this new form in the modern era with perhaps hidden consequences.
Iconoclast, Iconoclastic, and Iconoclasm: Notes Towards a Genealogy
Authors: Bremmer Jan
Published: July 2008

This article aims to contribute to a better understanding of the genealogy of the terms 'iconoclast(ic)' and 'iconoclasm.' After some observations on the beginning of early Christian art that stress the necessity of abandoning a monolithic view of Jewish, Christian, and Islamic art regarding their iconic/aniconic aspects, it is noted that 'iconoclast' is mentioned first just before the start of the iconoclastic struggle and always remained rare in Byzantium. It became known in the West by Anastasius's Latin translation of Theophanes' Chronographia Tripartita. From there it was probably picked up by Thomas Netter, whose Doctrinale against Wycliffe and his followers proved to be very influential in the early times of the Reformation when images were a focus of intense debate between Catholics and Protestants. Thus the term gradually gained in popularity and also gave rise to 'iconoclasm' and 'iconoclastic.' The present popularity of the term has promoted the grouping together of events that probably should not be considered together. It has also made scholars focus on Protestant vandalism during the Reformation period rather than on the much greater damage to medieval art caused by the Catholic Baroque period.
A Modified Tracer Selection and Tracking Procedure to Derive Winds Using Water Vapor Imagers
Authors: Deb S. K. , Kishtawal C. M. , Pal P. K. , Joshi P. C.
Published: July 2008

The remotely sensed upper-tropospheric water vapor wind information has been of increasing interest for operational meteorology. A new tracer selection based on a local image anomaly and tracking procedure, itself based on Nash–Sutcliffe model efficiency, is demonstrated here for the estimation of upper-tropospheric water vapor winds both for cloudy and cloud-free regions from water vapor images. The pressure height of the selected water vapor tracers is calculated empirically using a height assignment technique based on a genetic algorithm. The new technique shows encouraging results when compared with Meteosat-5 water vapor winds over the Indian Ocean region. The water vapor winds produced by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) from Meteosat-5 and the present algorithm are compared with collocated radiosonde observations according to Coordination Group for Meteorological Satellites guidelines. The proposed algorithm shows better accuracy in terms of mean vector difference, rms vector difference, standard deviation, speed bias, number of collocations, and mean speed and mean direction differences. Also it is found that the sensitivity of the spatial consistency check in the quality indicator is not so significant for the improvement of statistics.
Radar Reflectivity–Based Estimates of Mixed Layer Depth
Authors: Heinselman P. L. , Spencer P. L. , Elmore K. L. , Stensrud D. J. , Hluchan R. M. , Burke P. C.
Published: July 2008

This study investigates the potential for estimating mixed layer depth by taking advantage of the radial gradients in the radar reflectivity field produced by the large vertical gradients in water vapor mixing ratio that are characteristic of the mixing height. During the day, this relationship often results in a ring of maximum reflectivity observed to progress radially outward from the radar as mixed layer depth increases. A comparison of mixed layer depths estimated from the Oklahoma City WSR-88D (KTLX) with those estimated from a nearby 915-MHz profiler reveals that mixed layer depths from the WSR-88D are slightly too high (up to 0.3 km) during the first three hours of the diurnal cycle, nearly unbiased midday, and slightly too low (0.2 km or less) thereafter. The procedure estimates mixed layer depths only during the daytime hours from 1300 to 2300 UTC. The weather conditions for the 17 days studied were fairly quiescent, with sunny skies and light winds.
Improving the Northeast Asian Monsoon Simulation: Remote Impact of Tropical Heating Bias Correction
Authors: An Kyong-Hee , Tam Chi-Yung , Park Chung-Kyu
Published: July 2008

This study investigates the role of model tropical diabatic heating error on the boreal summer northeast Asian monsoon (NEAM) simulation given by a general circulation model (GCM). A numerical experiment is carried out in which the GCM diabatic heating is adjusted toward more realistic values in the tropics. It is found that the seasonal mean NEAM circulation and rainfall are improved in the GCM. This can be attributed to the reduced positive heating bias in the western Pacific Ocean around 10°–15°N in the model, which in turn leads to better-simulated low-level southerly winds over eastern Asia and more moisture supply to the NEAM region. The GCM’s ability in capturing the year-to-year variation of NEAM rainfall is also markedly improved in the experiment. These results show that the diabatic heating error over the western Pacific can be one reason for poor NEAM simulations in GCMs. The authors also suggest a simple method to reduce model heating biases that can be readily applied to dynamical seasonal prediction systems.
The Relationship Between Street Children and the Justice System in Egypt
Authors: Ammar Nawal H.
Published: July 2008

This article examines the relationship between street children and the justice system in Egypt. After introducing the context of street children in the Egyptian case, it explores whether the justice system exacerbates the problem of street children and whether its potential to play a positive part in alleviating the problem should be revisited. The article then explores the basis for the negative perspective on the role of the justice system and the steps required to improve its role in solving the problem of the increasing number of street children. It concludes with a three-pronged approach for the Egyptian justice system to adopt to effectively address the problem of street children. The article is based on an existing knowledge base that is scattered in small-sample empirical studies, large-scale surveys, United Nations reports, newspapers, and a few academic articles written in both English and Arabic.
Progress Monitoring in Middle School Mathematics
Authors: Foegen Anne
Published: July 2008

This study investigated the technical features of six potential progress-monitoring measures in mathematics appropriate for use at the middle school level, including two commercially available measures for sixth-grade mathematics, two measures used in previous middle school studies, and two new measures of numeracy concepts. Five hundred sixty-three students in Grades 6, 7, and 8 completed multiple forms of the measures on four occasions during the school year. Criterion variables included teacher ratings, mathematics grades, and standardized test scores. Results are reported for alternate form and test–retest reliability, concurrent and predictive criterion validity, and changes in student performance over time. Two of the measures demonstrated acceptable technical characteristics across grade levels. Recommendations for future research and implications for practitioners are discussed.
Sexual Harassment Among Students With Educational Disabilities
Authors: Young Ellie L. , Heath Melissa Allen , Ashbaker Betty Y. , Smith Barbara
Published: July 2008

This study investigated the perceptions of special education teachers about the prevalence and characteristics of sexual harassment among students identified with educational disabilities. Utah special education teachers (250) were randomly selected from the state's database. Fifty-two percent ( n = 129) of the surveys were returned. Approximately 92% of respondents reported observing incidents of student-to-student sexual harassment and sexually suggestive behaviors. Although male students were more frequently identified as harassers, similar proportions of males and females were identified as targets of sexual harassment. The most commonly reported behaviors included jokes, rumors of a sexual nature, and name-calling. When special educators observed incidents of sexual harassment, 82% intervened. When confronted, 74% of students immediately stopped their offensive behavior. Suggestions are made to assist special educators in decreasing sexual harassment by accurately identifying behaviors, intervening, and effectively responding.
The Effects of the Paraphrasing Strategy on the Reading Comprehension of Middle School Students at Risk for Failure in Reading
Authors: Hagaman Jessica L. , Reid Robert
Published: July 2008

Reading is an important component of academic success and a skill required for many adult responsibilities. Many strategies exist that claim to increase reading comprehension. However, in contrast to foundational reading skills (e.g., vocabulary, fluency, decoding), there is relatively little research that has been done on reading comprehension strategies. This study investigated the use of self-regulated strategy development paired with the “RAP” paraphrasing strategy as a way to increase reading comprehension. Participants were three sixth-grade students from a midwestern state. Results indicate that use of the RAP paraphrasing strategy increased reading comprehension.
Damage Mechanics Analysis of Transverse Cracking Behavior in Composite Laminates
Authors: Ogihara Shinji , Kobayashi Akira , Takeda Nobuo , Kobayashi Satoshi
Published: July 2008

A damage mechanics analysis is applied to predict transverse cracking in a laminated composite. Two criteria based on the energy release rate and the average ply stress are used to predict transverse cracking. The analytical prediction of transverse crack density as a function of applied laminate strain is favorably compared with the experimental results. An advantage of the present predictive method is that it can be applied to laminates with arbitrary stacking sequences.
A Numerical Parametric Investigation of Localization and Forming Limits
Authors: Horstemeyer M. F.
Published: July 2008

The ability of a theoretical model to accurately predict localization and failure strains, which characterize the formability of materials, has been a controversial subject as researchers have tried various analytical methods over the years to predict forming limit diagrams. In this work, we analyze various aspects of finite element modeling in which large deformation plasticity is coupled with continuum damage evolution. In the context of the Bammann-Chiesa-Johnson (BCJ) internal state variable model, we examine different finite element codes (DYNA3D, PRONTO3D, and JAC3D), sheet thicknesses (1.0 cm and 0.1 cm), types of instabilities (geometric perturbation and various initial void volume fraction mismatches), element types [solid continuum, Hughes and Liu (1980), and Belytschko and Tsay (1983)], mesh refinement, and two-stage nonproportional straining conditions. By varying these parameters in finite element calculations for determining forming limits, we ascertain not only the forming limit diagrams in a short time but an understanding of parametric effects that have been issues of concern for the auto, steel, and aircraft industries.
An Improved Two-Dimensional Micromechanical Theory for Brittle Solids with Randomly Located Interacting Microcracks
Authors: Ju J. W. , Tseng K. H.
Published: July 2008

This paper presents applications of accurate orthogonal function approximation methods to the two-dimensional problems of brittle solids containing many randomly located (and possibly randomly oriented) and strongly interacting microcracks within the framework of micromechanics and ensemble-volume average approach. The randomly located and oriented two-crack interaction problems are solved by using the highly accurate Legendre and Tchebycheff orthogonal polynomials to any desired order. The complex stress potential method is subsequently employed to micromechanically derive microcrack opening displacements under complicated loadings due to microcrack interaction effects-including concentrated loadings, arbitrary loadings and polynomial loadings. Improved local ensemble-averaged and overall effective elastic compliances of brittle solids due to microcracks and their interactions are systematically constructed by using the pairwise microcrack interaction mechanism and the ensemble-volume average approach. A number of interesting analytical-numerical examples containing different random microcrack configurations are also presented to illustrate the capabilities of the proposed framework.
A Non-Linear Fatigue Damage Model for Concrete in Tension
Authors: Vega Idelin Molinas , Bhatti M. Asghar , Nixon Wilfrid A.
Published: July 2008

Although concrete is used primarily because of its properties under compressive loading, a knowledge of its tensile behavior is essential in situations in which cracking, and the resulting change in stiffness, are critical for the service and ultimate load behavior of a structure. One important aspect of the tensile behavior of concrete is its performance under cyclic loading. The majority of past studies on the tensile fatigue performance of concrete have focused on the behavior under constant amplitude loads. However, in recent years, the effect of variable amplitude loading has also been emphasized. In this paper a model is presented for fatigue damage accumulation for concrete subjected to nonconstant tensile cyclic loads. The model is based on the concepts of Continuum Damage Mechanics and is able to account for the nonlinear propagation and accumulation of fatigue damage. Calibration of the model is done using existing experimental data, and its validity is checked against recently published tests.
Stiffness Loss of Composite Laminates with Transverse Cracks under Mode I and Mode III Loading
Authors: Lim E. H. , Tay T. E.
Published: July 2008

In this paper, the stiffness loss of general composite laminates with transverse cracks under mixed-mode loading is analyzed. The effective stiffnesses of the laminates are assumed to be functions of the nonlinear internal state variables (ISVs), which are dependent on crack densities, ply constraints, and crack opening profiles. The ISV corresponding to Mode I cracking is obtained from a series of finite element analysis. The ISV corresponding to Mode III cracking can be related to the Mode I ISV by considering geometrical constraints arising from the layup, for a laminate under tensile loading. Theoretical predictions of stiffness loss of glass/epoxy and graphite/epoxy composite laminates with transverse cracks are compared with experimental data available from published sources, for crossply, angleply, and quasi-isotropic laminates. In addition, the model enables the contributions from respective modes to the overall stiffness reduction to be determined. Results of analyses have shown good and excellent agreement with published experimental data from other researchers.
On Damage Effective Stress and Equivalence Hypothesis
Authors: Zheng Q. S. , Betten J.
Published: July 2008

The concepts of damage effective stress and damage equivalence hypothesis play an important role in the development of continuum damage mechanics. Based on a generalization of the damage equivalence hypothesis, the so-called damage isotropy principle, it is found that the effective stress as a second-order tensor-valued function of the usual stress tensor and the damage tensor(s) has to be isotropic. Particularly, this property is regardless of the initial material symmetry (isotropy or anisotropy) and the type of damage variables; and thus, it allows general invariant modeling of the effective stress by the use of theory of tensor function representations. Damage material constants are then consistently introduced to the invariant models of the effective stress and the damage effect tensors. Three new models of the damage effect tensor capable of including realistic dimensionless damage material constants are proposed. The significance of the damage material constants is examined by micromechanical analysis and computer experiments on effective elastic moduli.
Inelastic Flow Behavior of Argillaceous Salt
Authors: Chan K. S. , Bodner S. R. , Munson D. E. , Fossum A. F.
Published: July 2008

The effects of weak clay particles on the creep response of argillaceous salt have been analyzed by considering the particles as damage initiation sites where local tensile stresses and microcracks are induced under triaxial compression. The thermodynamic driving force for the damage process is formulated in terms of an appropriate power-conjucate equivalent stress measure, and the damage kinetics are described in terms of an evolution equation formulated on the basis of the conjugate equivalent stress and the scalar damage variable from Kachanov (1958). This treatment of clay particle effects is then incorporated into the Multimechanism Deformation Coupled Fracture (MDCF) constitutive model. A summary of the constitutive model is presented with an evaluation of the model calculations against experimental data of clean and argillaceous salt. The results suggest that the higher creep rate observed in argillaceous salt compared to clean salt is the consequence of increased damage growth in argillaceous salt due to the presence of weak clay particles.
Kinematic Waves and Nonuniform Damage Development in Composite Laminates
Authors: Gamby D. , Lafarie-Frenot M. C. , Henaff-Gardin C.
Published: July 2008

When subjected to fatigue loading, the off-axis plies of some polymer matrix laminates undergo a transverse cracking whose density is maximum close to the free edges and decreases toward the specimen center; moreover, this damage distribution evolves as the number of cycles increases. The "kinematic wave" concept is applied to the principle of conservation of number of crack tips, along with suitable assumptions concerning the velocity of a crack tip propagating into a material whose damage state is characterized by a local crack density. This principle gives a nonlinear wave equation governing damage as a function of both distance x from a free edge and number N of cycles. Experimental results pertaining to a cross-ply carbon/epoxy laminate whose 90° layers are thin compared to the longitudinal layers are obtained in the form of successive X-ray pictures taken at different times in the specimen life. Plotting the contour lines of damage in the (x,N) plane results in a family of straight lines which can be interpreted as the characteristic curves of a simple wave solution for the above wave equation. Measuring the slope of each curve of this family, along which damage is constant, allows the coefficient of the wave equation to be determined as a function of damage. A power law is found to fit well with the corresponding curve, which assesses the consistency of the model with the experimental results for the laminate investigated. The damage growth law obtained in this manner is the first step toward the future construction of a more general model which could be used to predict the service life of a composite structural part.
On Representation of Damage Evolution in Continuum Damage Mechanics
Authors: Lacy T. E. , McDowell D. L. , Willice P. A. , Talreja Ramesh
Published: July 2008

The effect of damage patterning on elastic moduli and damage evolution in ideal brittle cracked solids is examined. Key limitations associated with typical continuum damage mechanics approaches are addressed. Critical shortcomings arising from the use of spatially-averaged damage descriptors in the evaluation of effective moduli and thermodynamic forces are investigated using numerical simulations of evolving two-dimensional crack systems. Fundamental elements of a higher-order continuum description of damage based on distribution functions are discussed, which directly include damage interaction effects.
Mode I Damage Modeling in Brittle Preloading
Authors: Yazdani S. , Karnawat S.
Published: July 2008

A new anisotropic damage model for brittle solid inelasticity is developed to accommodate observed behavior in applications where the preloading effects are involved. The shortcomings of conventional damage formulations using the "cumulative damage parameter" is outlined, and a new formulation based on the concept of "effective damage parameter" is proposed. The rate of the effective damage parameter is obtained from the consistency condition associated with a damage surface. The cumulative damage parameter is still used as a measure of total dissipated energy. Anisotropy, dilatation, and strength degradation due to pre-loading effects are captured within the formulation. The model is illustrated for concrete in both proportional and nonproportional stress paths in mode I.
Theory of Dichotomy for Concrete Modelling under Cyclic Biaxial Loading
Authors: Taher Salah El-Din M. Fahmy , Baluch Mohammed H.
Published: July 2008

An orthotropic model which accounts for the inelastic behavior of concrete elements loaded biaxially is developed using the theory of dichotomy. The proposed theory replaces the continuum by a system of orthogonal springs. The behavior of concrete is idealized as elastoplastic damage through splitting the strain tensor into two main components. Consequently, three possible forms of constitutive relation are presented which associate the stress tensor to the total strain, the elastic-damage strain and the plastic-damage strain, respectively. These relations are adopted in diagonal tensorial form in the principal space using proper damage variables. The interdependence between the stress components are taken into account using the biaxiality ratio for all possible combinations of the principal stresses, i.e., compression-compression, compression-tension and tension-tension. Thermodynamical considerations in view of the proposed theory are discussed. The model is shown to be simple and in close agreement with a wide set of the well documented existing experimental data where the salient features of concrete behavior-such as strain softening, stiffness degradation, volumetric dilatation-are captured.
Internal Variable Representation of Microcrack Induced Inelasticity in Brittle Materials
Authors: Basista M. , Gross D.
Published: July 2008

For brittle materials strained in compression, nonlinear constitutive equations are developed within the thermodynamic framework with microstructural internal variables. The sliding crack dissipative micromechanism, activated on preexisting dilutely distributed flaws, is assumed to govern the macroscopic deformation. The losses of energy resulting from frictional sliding on closed preexisting flaws, wing crack propagation, and wing crack rotation are included in the analysis. Two models (displacement-driven vs traction-driven) of the basic deformational micromechanism are considered in detail. The obtained incremental stress-strain relations are compared with the corresponding kinematic solutions available in the literature.
Void Growth in Glassy Polymers: Effect of Yield Properties on Hydrostatic Expansion
Authors: Steenbrink A. C. , Van Der Giessen E.
Published: July 2008

Void growth in plastically deforming glassy polymers is investigated by means of a simple spherical symmetric model. This type of void growth occurs in cavitated polymer-rubber blends and, at a smaller scale, during craze initiation. The study serves to provide approximate values for the stresses required for elastic-viscoplastic void growth under hydrostatic loading conditions. The constitutive model accounts for features such as rate and temperature dependent yield, intrinsic strain softening after yield, and subsequent hardening due to molecular alignment at large deformations. The separate effects of these features on void expansion and the stress distribution are studied. Due to the relatively large strain at yield for most glassy polymers, elastic effects play an important role even at macroscopic yield. Therefore, predictions of the maximum stress are significantly lower than those based on rigid-plastic behaviour, especially for low void volume fractions.
Application of the Orthotropic Damage Growth Rule to Variable Principal Directions
Authors: Skrzypek J. , Ganczarski A.
Published: July 2008

The classical orthotropic brittle damage law [Kachanov (1958)] is applicable for principal directions of the stress tensor. When shear stresses are accounted, the principal directions of the stress tensor rotate with time and, hence, a tensorial formulation of the damage is required [Chow and Lu (1992)]. In general, current principal directions of the stress tensora, and of the damage tensorp3B do not coincide, however, when the principal axes of stress rotate due to the shear effect, the principal axes of damage follow them. The symmetric second rank damage tensor 2 [Murakami and Ohno (1981)] is applied, and the objective derivative Q of the damage tensor is adopted, to account for the effect of rotation of principal directions on the damage accumulation process. Then, a current transformation to the global coordinate system (sampling coordinate space) is performed. The similarity of deviators based on the flow theory and on the time hardening hypothesis, associated with the orthotropic damage growth rule, both written for current principal directions of stress, are taken as constitutive relationships for creep [Boyle and Spence (1983), Kachanov (1986)]. Three examples are considered: rotationally-symmetric disk subjected to stationary radial and tangential forces, disk subjected to sustained radial tension and multiple reverse torsion. and disk subjected to alternating body forces due to acceleration/breaking cycles.
Progressive Fracture of Fiber Composite Thin Shell Structures under Internal Pressure and Axial Loads
Authors: Gotsis Pascal K. , Chamis Christos C. , Minnetyan Levon
Published: July 2008

Graphite/epoxy composite thin shell cylindrical structures were simulated to investigate damage and fracture progression due to internal pressure and axial loading. Defective and defect-free structures (thin cylinders) were examined. The three laminates examined had fiber orientations of [90/0/±O],, where 0 is 450, 600, and 75°. CODSTRAN, an integrated computer code that scales up constituent level properties to the structural level and accounts for all possible failure modes, was used to simulate composite degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture were included in the simulation. Burst pressures for defective and defect-free shells were compared to evaluate damage tolerance.

The results showed that damage initiation began with matrix failure, whereas damage and/or fracture progression occurred as a result of additional matrix failure and fiber fracture. In both thin cylinder cases examined (defective and defect-free), the optimum layup configuration was [90/0/±60], because it had the best damage tolerance with respect to the burst pressure.
A Continuum Damage Mechanics Model for Fiber Reinforced Composites
Authors: Isometsä Juha , Sjölind Stig-Göran
Published: July 2008

Continuum damage mechanics has been proven to be a valuable tool for the determination of material deterioration of composites. Within this framework, a continuum damage model for determination of effective response of fiber reinforced composites is presented. It is assumed that damage evolves on planes with normal orthogonal to the fiber direction and thus is capable of describing the matrix dominated failure of composites. The approach is based on a tensorial representation of damage and on a coordinate-free determination of thermodynamic and dissipative potentials. To simplify the expression of the thermodynamic potential, certain damage tensor components are used to describe the initial material anisotropy. Furthermore, dissipative potentials are formulated which are assumed to be isotropic functions of the thermodynamic forces associated with damage tensors. Parameters for the CDM model are determined using a microscale homogenization method, in which a representative cell of the periodic microstructure consists of fibers, matrix, and two crack fields which are parallel to the fiber direction and evolve independently. The assumption of two independent crack fields in an initially transversely isotropic media makes the material behaviour monoclinic. A representative cell is discretized by the finite element method and the CDM model is fitted by the least squares method to the results obtained. It is concluded from the obtained results that the proposed damage model is capable of describing elastic properties of the damage material. Finally, the CDM model is implemented into the general purpose finite element program ABAQUS in order to capture the effective response of composites. The proposed approach is illustrated by simulating damage growth at the meso-level by calculating the response of a unidirectional laminate loaded in tension. The obtained results show that the essential aspects of the mechanical behaviour of a continuous fiber composite loaded in tension can be captured by the present damage model.
A Model of Quasibrittle Fracture of Solids
Authors: Kanaun S. K. , Chudnovsky A. I.
Published: July 2008

The present work is dedicated to the modeling of damage (microcracks) growth in solids under overall tensile stresses. The model is based on the thermodynamic analysis of damage. The kinetic equations for the density of microcracks and their orientations are obtained from the first and second laws of thermodynamics applied to the proposed model. The condition of the final (local) failure follows naturally from the kinetic equation of the damage growth as instability of its solution. Analysis of the proposed kinetic equations and the application of the model to the damage growth under complex loading history are presented.
3-D Thermoelastic Moduli and Saturation Crack Density for Cross-Ply Laminates with Transverse Cracks
Authors: Schoeppner G. A. , Pagano N. J.
Published: July 2008

For stiffness critical structures, such as those found in space applications, the structural design and functionality may depend on several stiffness components. In this work we study the effect of transverse cracking on the effective Young's moduli, the effective Poisson ratios and the effective coefficient of thermal expansion for glass/epoxy and graphite/epoxy cross-ply laminates. In particular, included in the study are the effect of prescribed boundary conditions on the representative volume element used to describe the problem, the effect of variable crack spacing, and the interaction of transverse crack stress fields. The analysis is accomplished by the use of a model based on Reissner's variational principle that has been shown to accurately model stress fields and energy release rates in flat laminates. The present model predictions are compared to shear lag and finite element predictions from the literature and found to be in good agreement with published experimental data. A criterion to estimate the limiting density for pure transverse cracking damage is presented. Additionally, it is shown that for large crack densities, the model accurately recovers the limiting theory ply-discount effective property values.
Risk Factors Linking Maternal Depressed Mood to Growth in Adolescent Substance Use
Authors: Cortes Rebecca C. , Fleming Charles B. , Mason W. Alex , Catalano Richard F.
Published: July 2008

Maternal depression has been implicated in the development of adolescent substance use. Conceptualizing depression as a continuum, the aims of this study are to (a) understand the relationship between maternal depressed mood and risk factors associated with adolescent substance use; (b) understand the relationship between maternal depressed mood and level and growth in adolescent alcohol, cigarette, and marijuana use assessed at multiple time points during adolescence; and (c) examine the unique and relative contribution of maternal depressed mood after taking into account contextual risk factors related to adolescent substance use. Participants are 792 children and their mothers. Latent growth modeling is used with adolescent alcohol, cigarette, and marijuana use treated as ordinal variables. Child depressive phenomena and child antisocial behavior partially explain the relationship between maternal depressed mood and adolescent alcohol and cigarette use. Mothers' own substance use does not contribute to level or change in adolescent substance use after other risk factors are considered.
Do Enterprise Zones Work?
Authors: Billings Stephen
Published: July 2008

This article analyzes Enterprise Zones in Colorado to study the relationship between geographically targeted tax credits and the location of new businesses and jobs. Enterprise Zone (EZ) programs provide tax incentives for investment and job creation in economically lagging regions. While most states have EZ programs, past program evaluations have found a mixture of effectiveness. This research improves on existing literature by utilizing both establishment-level data and a border effects methodology (1) to control for unobservables that influence the self-selection of EZ regions and (2) to highlight EZ impacts across different industries. Results find that while EZ fiscal incentives have no effect on where new establishments locate in Colorado, they do increase the number of employees hired. Industry results highlight the heterogeneity of tax credit impacts within the EZ Program. Results are robust to a variety of specifications for land-use controls and in comparison to a propensity score matching model.
The Impact of Emissions from Structures on Indoor Air Concentrations in Newly Finished Buildings — Predicted and On-Site Measured Levels
Authors: Järnström H. , Saarela K. , Kalliokoski P. , Pasanen A.-L.
Published: July 2008

The impact of surface emissions (VOCs, ammonia, and formaldehyde) on the indoor air quality (IAQ) in newly established buildings was examined. Six apartment buildings, in which low-emitting, classified building materials were used, were investigated 0, 6, and 12 months after completion of construction work. The predicted indoor air concentrations based on the on-site measured emissions (floor, walls, ceiling) and air exchange rates were in general lower than the measured indoor air concentrations. The contribution of other sources was on the average about 50% for VOCs and 25—35% for ammonia and formaldehyde. The ceiling structure was the main source of pollutants throughout the first year. PVC floor covering affected IAQ significantly in the newly finished buildings. The contribution of walls was relatively low in spite of large surface area. The impact of VOC emissions from surfaces on indoor air clearly decreased during the follow-up period whereas the impact of ammonia and formaldehyde emissions remained about the same. Higher SVOC concentration was measured in the buildings with PVC flooring compared to the rooms with parquet flooring in the 0 to 6-month-old buildings.
Verification of Properties of Concrete Reinforcement Bars: Nigeria as a Case Study
Authors: Arum C.
Published: July 2008

An investigation was conducted into the level of conformance of ribbed steel bars used in Nigeria's structural concrete practice to relevant international and local provisions. In this research, all bars imported into Nigeria from member countries of ISO as well as those marked with the identity of the local producing mill are classified as steel of recognizable origin while bars imported from ISO nonmember countries as well as those without an identifying mark from the producing works are classified as steel of non recognizable origin. The investigation showed that steel of recognizable origin satisfied both local and ISO requirements for strength and ductility whereas those bars of nonrecognizable origin failed to satisfy the above requirements for high-yield bars but satisfied the local specifications if used as mild steel. Based on these findings, appropriate recommendations are made.
Seasonal Variation of Indoor Gamma Dose and Radon, Thoron Measurement in the Dwellings around Kudankulam Nuclear Power Plant (Radhapuram Taluk, Tirunelveli District)
Authors: Brahmanandhan G.M. , Selvasekarapandian S. , Malathi J. , Khanna D. , Meenakshisundaram V. , Santhanam S. , Balasundar S. , Dhanalakshmi B.
Published: July 2008

Indoor gamma dose and indoor radon, thoron and their progeny concentrations have been measured around the upcoming Kudankulam Nuclear Power Plant i.e., in the Radhapuram taluk. The measurements have been carried throughout a year to account for the seasonal variation of indoor gamma dose and indoor radon, thoron, and their progeny concentrations. Indoor gamma dose value is found to be maximum in the summer season (459.2 ± 82.3 nGy·h-1). Indoor radon, thoron and their progeny concentration are found to be maximum in the winter season. The annual effective dose due to indoor gamma radiation to the Radhapuram population is found to be 1.5 mSv. The total annual inhalation dose arising due to radon, thoron, and their progeny concentrations to population is found to be 1.03mSv in Radhapuram taluk.
Review Paper: Design, Aesthetics and the Issue of Integrity in the Built Environment: The Nigerian Example
Authors: Kayode Femi , Ojo Bankole , Sheba E.A.
Published: July 2008

This review advocates that integrity remains a crucial requisite in designing and beautifying any created environment. Integrity of design and aesthetics in the Built Environment has historical antecedent in the Arts and Crafts Movement in Britain in the early 20th century. Already, by this time, there were competing values of concern for prudence, morality and sincerity in the application of materials for design forms and functions, believing that in a created environment, physical features that were produced and modified by man to serve his needs should be governed by `social conscience'. This basic concept is still relevant to contemporary design. It is imperative for the artist/ designer, artisan, architect and planner to consider the matter of integrity in each of its separate applications: to materials, form, function, and ornamentation. Diversity of views concerning the meaning of design and aesthetics and the uncertainties they contain have little or no capacity to negate the principle of integrity of design whether as process or product. Nevertheless, design and aesthetics have common things to share in the harmony of functions. This paper considers the various opinions of scholars concerning the subject and highlights the importance of certain design elements and principles necessary for inducing and sustaining the aesthetics of the environment.
Teaching to Make a Difference
Authors: Holsinger Kristi
Published: July 2008

This article addresses college classes as forums for activism. One course brought college students together with system-involved girls for a mentoring program to provide often-unavailable, relationship-oriented services to girls. A second course provided a unique educational experience for incarcerated youth and traditional college students to study restorative justice. As such, the course itself was an attempt to practice restorative justice principles by strengthening the damaged relationship between offenders and the community. Data collected from participants allow for an exploration of the experiences, perceptions, and changes in attitudes and beliefs. Further discussion on linking activism and teaching is presented.
TTP diagrams for 7055 aluminium alloy
Authors: Liu S. D. , Zhang X. M. , You J. H. , Huang Z. B. , Zhou Z. P.
Published: July 2008

The Vickers hardness and electrical conductivity time–temperature–property (TTP) diagrams for 7055 aluminium alloy were evaluated by an interrupted quench technique. The results show that the critical temperature range was approximately from 230 to 420°C, with the nose temperature of ∼355°C. Rapid decrease in hardness and increase in electrical conductivity were observed with isothermal holding within the critical temperature range.