bluuebunny/crossref_metadata_2025 huggingface dataset:
Introduction: How to Deal with Uncertainty in Population Forecasting?
Authors: Lutz Wolfgang , Goldstein Joshua R.
Published: August 2010

Demographers can no more be held responsible for inaccuracy in forecasting population 20 years ahead than geologists, meteorologists, or economists when they fail to announce earthquakes, cold winters, or depressions 20 years ahead. What we can be held responsible for is warning one another and our public what the error of our estimates is likely to be.–Nathan Keyfitz (1981)
Random Scenario Forecasts Versus Stochastic Forecasts
Authors: Tuljapurkar Shripad , Lee Ronald D. , Li Qi
Published: August 2010

Probabilistic population forecasts are useful because they describe uncertainty in a quantitatively useful way. One approach (that we call LT) uses historical data to estimate stochastic models (e.g., a time series model) of vital rates, and then makes forecasts. Another (we call it RS) began as a kind of randomized scenario: we consider its simplest variant, in which expert opinion is used to make probability distributions for terminal vital rates, and smooth trajectories are followed over time. We use analysis and examples to show several key differences between these methods: serial correlations in the forecast are much smaller in LT; the variance in LT models of vital rates (especially fertility) is much higher than in RS models that are based on official expert scenarios; trajectories in LT are much more irregular than in RS; probability intervals in LT tend to widen faster over forecast time. Newer versions of RS have been developed that reduce or eliminate some of these differences.
Corbelled Domes in Two and Three Dimensions: The Treasury of Atreus
Authors: Lazar Nicole A. , Kadane Joseph B. , Chen Fang , Cavanagh William G. , Litton Clifford D.
Published: August 2010

Before the development of the true dome, many ancient cultures used the technique of corbelling to roof spaces. Recently, a series of related statistical models have been proposed in the literature for explaining how corbelled domes might have been constructed. The most sophisticated of these models is based on a piecewise linear structure, with an unknown number of changepoints, to guide the building process. This model is analyzed by the reversible jump Markov Chain Monte Carlo (MCMC) technique. All models considered to date have been two‐dimensional, that is, they have taken a single cross section through the dome; even when more extensive data, in the form of measurements on multiple slices through the dome, have been available, these have been averaged together for the purposes of analysis. In this paper, we extend the two‐dimensional analysis to a three‐dimensional analysis, that takes full advantage of the data collected by the archaeologists and of the rotational symmetries inherent in the structure.We also explore ways of graphically presenting the results from a complex, reversible jump MCMC implementation, in order to check convergence, good mixing, and appropriate exploration of the (high dimensional and varying dimension) parameter space. The model and the graphical techniques are demonstrated on the Treasury of Atreus in Mycenae, Greece, one of the finest extant examples of the corbelling method.
Simple Correspondence Analysis: A Bibliographic Review
Authors: Beh Eric J.
Published: August 2010

Over the past few decades correspondence analysis has gained an international reputation as a powerful statistical tool for the graphical analysis of contingency tables. This popularity stems from its development and application in many European countries, especially France, and its use has spread to English speaking nations such as the United States and the United Kingdom. Its growing popularity amongst statistical practitioners, and more recently those disciplines where the role of statistics is less dominant, demonstrates the importance of the continuing research and development of the methodology.

The aim of this paper is to highlight the theoretical, practical and computational issues of simple correspondence analysis and discuss its relationship with recent advances that can be used to graphically display the association in two‐way categorical data.
A Comparative Analysis of Different IV and GMM Estimators of Dynamic Panel Data Models
Authors: Harris Mark N. , Mátyás László
Published: August 2010

It is well known that the usual procedures for estimating panel data models are inconsistent in the dynamic setting. A large number of consistent estimators however, have been proposed in the literature. This paper provides a survey of the majority of mainstream estimators, which tend to consist of IV and GMM ones. It also considers a newly proposed extension to the promising Wansbeek–Bekker estimator (Harris & Mátyás, 2000). To provide guidance to the applied researcher working on micro‐datasets, the small sample performance of these estimators is evaluated using a set of Monte Carlo experiments.
Critique of p‐Values
Authors: Thompson Bill
Published: August 2010

This paper generalizes the notion of p‐value to obtain a system for assessing evidence in favor of an hypothesis. It is not quite a quantification in that evidence is a pair of numbers (the p‐value and the p‐value with null and alternative interchanged) with evidence for the alternative being claimed when the first number is small and the second is at least moderately large. Traditional significance tests present p‐values as a measure of evidence against a theory. This usage is rarely called for since scientists usually wish to accept theories (for the time being) not just not reject them; they are more interested in evidence for a theory. P‐values are not just good or bad for this purpose; their efficacy depends on specifics. We find that a single p‐value does not measure evidence for a simple hypothesis relative to a simple alternative, but consideration of both p‐values leads to a satisfactory theory. This consideration does not, in general, extend to composite hypotheses since there, best evidence calls for optimization of a bivariate objective function. But in some cases, notably one sided tests for the exponential family, the optimization can be solved, and a single p‐value does provide an appealing measure of best evidence for a hypothesis. One possible extension of this theory is proposed and illustrated with a practical safety analysis problem involving the difference of two random variables.
Smoothing Observational Data: A Philosophy and Implementation for the Health Sciences
Authors: Greenland Sander
Published: August 2010

Standard statistical methods (such as regression analysis) presume the data are generated by an identifiable random process, and attempt to model that process in a parsimonious fashion. In contrast, observational data in the health sciences are generated by complex, nonidentified, and largely nonrandom mechanisms, and are analyzed to form inferences on latent structures. Despite this gap between the methods and reality, most observational data analysis comprises application of standard methods, followed by narrative discussion of the problems of entailed by doing so. Alternative approaches employ latent‐structure models that include components for nonidentified mechanisms. Standard methods can still be useful, however, provided their modeling philosophy is modified to encourage preservation of structure, rather than achieving parsimonious description. With this modification they can be viewed as smoothing or filtering methods for separating noise from signal before the task of latent‐structure modeling begins. I here give a detailed justification of this view, and a hierarchical‐modeling implementation that can be carried out with popular software. Concepts are illustrated in the smoothing of a contingency table from an analysis of magnetic fields and childhood leukemia.
Skewed Normal Variance‐Mean Models for Asset Pricing and the Method of Moments
Authors: Tjetjep Annelies , Seneta Eugene
Published: August 2010

Financial returns (log‐increments) data, Yt, t= 1,2,…, are treated as a stationary process, with the common distribution at each time point being not necessarily symmetric.

We consider as possible models for the common distribution four instances of the General Normal Variance‐Mean Model (GNVM), which is described by Y|V∼N(a(b + V), c2V +d2) where V is a nonnegative random variable and a, b, c and d are constants. When V is Gamma distributed and d= 0, Y has the skewed Variance‐Gamma distribution (VG). When V follows a Half Normal distribution and c= 0, Y has the well‐known Skew Normal (SN) distribution. We also consider two cases where V is Exponentially distributed. Bounds for skewness and kurtosis in each case are found in terms of the moments of the V. These are useful in determining whether the Method of Moments for a given model is feasible. The problem of overdetermination of parameters via estimating equations is examined. 5 data sets of actual returns data, chosen because of their earlier occurrence in the literature, are analysed using each of the 4 models.
Comparison of Benchmarking Methods with and without a Survey Error Model
Authors: Chen Zhao‐Guo , Wu Ka Ho
Published: August 2010

For a target socio‐economic variable, two sources of data with different precisions and collecting frequencies may be available. Typically, the less frequent data (e.g., annual report or census) are more reliable and are considered as benchmarks. The process of using them to adjust the more frequent and less reliable data (e.g., repeated monthly surveys) is called benchmarking.

In this paper, we show the relationship among three types of benchmarking methods in the literature, namely the Denton (original and modified), the regression, and the signal‐extraction methods. A new method called “quasi‐linear regression” is proposed under the multiplicative assumption. The numerical Denton method is currently widely used. The aim of this paper is to promote the other two methods which are statistically model‐based; the model for the survey error is assumed to be known. Assuming the survey‐error series follows an autoregressive model of order 1, by simulation, we investigate the impact of misspecification of the model on the benchmarking prediction according to the criterion of minimizing the root‐mean‐squared error of prediction. It is concluded that both statistical methods have great advantages over the Denton method and they are robust to misspecification of the survey‐error model. The problem of how to obtain a survey‐error model is also mentioned.
Improving Statistics on International Migration in Asia
Authors: Hugo Graeme
Published: August 2010

International migration has reached unprecedented scale, diversity and political, economic, social and demographic significance in Asia over the last decade. Despite this data collection of migrant stocks and flows remains very limited in most Asian countries. Accordingly, policy making on migration in the region lacks an evidence base and is influenced by interest groups, anecdotal evidence and prejudice. This paper argues that the heightened security consciousness since 911 together with the development of efficient computer based collection and analysis of migration data systems has created a propitious environment for bringing about a parametric improvement in data collection on international migration in Asia. A number of suggestions are made in this regard, especially the inclusion of relevant international migration questions in the 2010 round of population censuses.
Towards an Integrated Statistical System at Statistics Netherlands*
Authors: Heerschap Nico , Willenborg Leon
Published: August 2010

Changes in circumstances put pressure on Statistics Netherlands (SN) to redesign the way its statistics are produced. Key developments are: the changing needs of data‐users, growing competition, pressure to reduce the survey burden on enterprises, emerging new technologies and methodologies and, first and foremost, the need for more efficiency because of budget cuts.

This paper describes how SN, and especially its business statistics, can adapt to these new circumstances. We envisage an optimum situation as one with a single standardised production line for all statistics and a central data repository at its core. This single production line is supported by generic and standardised tools, metadata and workflow management.

However, it is clear that such an optimum situation cannot be realised in just a few years. It should be seen as the point on the horizon. Therefore, we also describe the first transformation steps from the product‐based stovepipe‐oriented statistical process of the past to a more integrated process of the future.

A similar modernisation process exists in the area of social statistics. In the near future both systems of business and social statistics are expected to connect at pivotal points and eventually converge on one overall business architecture for SN. Discussions about such an overall business architecture for SN have already been started and the first core projects have been set up.
Virtual Environments and the Acceleration of Experiential Learning
Authors: Wild Chris
Published: August 2010

Darius et al. (2007) and Nolan & Temple Lang (2007) give examples of virtual environments that can, for specific purposes, substitute for the real world. We are in the early stages of developments that could revolutionize statistics education by making it possible to capture efficiently important aspects of the thinking and practice of professional statisticians previously learned only from long years of experience. The ability of virtual environments to automate processes provides a potent weapon for tackling the tyranny that Time exercises over such modes of learning. We discuss the many new possibilities that are opened up by virtual environments together with cognitive and pedagogical imperatives to be addressed to ensure that environments actually do teach the lessons they were designed to teach. We echo Nolan and Temple Lang's call for the development of environments to be modular and open source. Taking the R‐project as a model, this can lead to a growing repository of building blocks that make the construction of future environments less costly, thus facilitating the realization of more and more ambitious conceptions.
Exopolysaccharides of Lactobacillus rhamnosus GG form a protective shield against innate immune factors in the intestine
Authors: Lebeer Sarah , Claes Ingmar J. J. , Verhoeven Tine L. A. , Vanderleyden Jos , De Keersmaecker Sigrid C. J.
Published: August 2010

Probiotic bacteria are administered as live microorganisms to provide a health benefit to the host. Insight into the adaptation factors that promote the survival and persistence of probiotics in the gastrointestinal tract (GIT) is important to understand their performance. In this study, the role of the long galactose‐rich exopolysaccharides (EPS) of the prototypical probiotic strain Lactobacillus rhamnosus GG (LGG) was investigated. In a competition experiment with wild type, the isogenic EPS mutant CMPG5351 exhibited a reduced persistence in the murine GIT, especially in the lower parts of the intestine. This was surprising as our previous in vitro studies had shown an increased adhesion capacity for this EPS mutant. Follow‐up assays indicated that this mutant is more sensitive towards host innate defence molecules, such as the LL‐37 antimicrobial peptide and complement factors. This suggests that EPS forms a protective shield for LGG against these molecules in the GIT. Moreover, culturing LGG wild‐type in subinhibitory concentrations of host defence factors such as LL‐37 resulted in increased production of EPS, indicating that bacterial EPS production is modulated in the host to fine‐tune the balance between adhesion and immune evasion. These observations are of interest in understanding the dynamics of adaptation of probiotics to the host environments.
Interobserver variability for retreatment indications after Ranibizumab loading doses in neovascular age‐related macular degeneration
Authors: Framme Carsten , Panagakis Georgios , Walter Andreas , Gamulescu Maria Andreea , Herrmann Wolfgang , Helbig Horst
Published: August 2010

Purpose:  To assess the interobserver variability (IOV) in indicating retreatment for neovascular Age‐related macular degeneration 4 weeks after three Ranibizumab loading doses using spectral domain OCT (SD‐OCT) as the primary objective diagnostic tool.

Material and methods:  Four observers decided for or against 4th Ranibizumab injection in 108 patients by six different rating rounds (RR) based on the SD‐OCT findings after the loading doses. Postoperative OCT images were supplemented consecutively with information from a chart review as the ‘patients subjective estimation of vision (SE)’, the course of best‐corrected visual acuity (BCVA) and the preoperative OCT as well as all information collectively. Agreement rates (AR) and Kappa statistics were calculated.

Results:  Based on post‐treatment OCT findings only (RR1), mean reinjection rate of all observers was 37.5%. Adding supplementary information, mean reinjection rate decreased to 20% when all information was available reflecting the ‘real’ situation (RR 6). Interobserver agreement rates varied from 66.7% to 90.7% depending on rating rounds and interobserver pairs. Mean AR and Kappa values (KV) were as following: AR 81.6%, KV 0.61 (RR1: ‘only post‐OP OCT’); AR 76.7%, KV 0.33 (RR2: post‐OP OCT + SE); AR 80.3%, KV 0.45 (RR3: post‐OP OCT + BCVA); AR 80.7%, KV 0.46 (RR4: pre‐ and post‐OP OCT); AR 82.2%, KV 0.49 (RR5: post‐OP OCT + SE + BCVA); and finally AR 83.6%, KV 0.47 (RR6: pre‐ and post‐OP OCT + SE + BCVA). The overall mean agreement rate was 80.9% with a Kappa of 0.47.

Conclusion:  IOV for indicating retreatment after three Ranibizumab loading doses reveals only moderate agreement in Kappa statistics, which seems to be too low considering the high costs for retreatments. More concise guidelines based on the post‐treatment OCT scans as the presumably most sensitive and noninvasive objective tool to follow choroidal neovascularization activity by judging the course of sub‐ and intraretinal fluid are necessary.
Linum kaynakiae sp. nov. (sect. Syllinum, Linaceae) from Turkey
Authors: Yılmaz Özer
Published: August 2010

Selected characters in related taxa of Linum sect. Syllinum are compared using morphometric data and scanning electron microscopy (SEM). As a result, Linum kaynakiae Yılmaz sp. nov. is described from southwest Anatolia, Turkey. It is closely related to L. tauricum subsp. bosphori, L. boisseri and L. cariense, but differs by having larger linear‐oblanceolte rosette leaves and larger lanceolate sepals. Its relationship with closely related taxa is discussed. Diagnostic characters, description and taxonomic remarks and an identification key to the sect. Syllinum taxa ‐ with persistent basal rosettes of leaves at anthesis ‐ is provided.
Optimal Configuration of a Service Delivery Network: An Application to a Financial Services Provider
Authors: Meester Geoffrey A. , Mehrotra Anuj , Natarajan Harihara Prasad , Seifert Michael J.
Published: August 2010

Driven by market pressures, financial service firms are increasingly partnering with independent vendors to create service networks that deliver greater profits while ensuring high service quality. In the management of call center networks, these partnerships are common and form an integral part of the customer care and marketing strategies in the financial services industry. For a financial services firm, configuring such a call center service network entails determining which partners to select and how to distribute service requests among vendors, while incorporating their capabilities, costs, and revenue‐generating abilities. Motivated by a problem facing a Fortune 500 financial services provider, we develop and apply a novel mixed integer programming model for the service network configuration problem. Our tactical decision support model effectively accounts for the firm's costs by capturing the impact of service requirements on vendor staffing levels and seat requirements, and permits imposing call routing preferences and auxiliary service costs. We implemented the model and applied it to data from an industry partner. Results suggest that our approach can generate considerable cost savings and substantial additional revenues, while ensuring high service quality. Results based on test instances demonstrate similar savings and outperform two rule‐based methods for vendor assignment.
Analysis of Two‐Level Support Systems with Time‐Dependent Overflow—A Banking Application
Authors: Barth Wolfgang , Manitz Michael , Stolletz Raik
Published: August 2010

In this paper, we analyze the performance of call centers of financial service providers with two levels of support and a time‐dependent overflow mechanism. Waiting calls from the front‐office queue flow over to the back office if a waiting‐time limit is reached and at least one back‐office agent is available. The analysis of such a system with time‐dependent overflow is reduced to the analysis of a continuous‐time Markov chain with state‐dependent overflow probabilities. To approximate the system with time‐dependent overflow, some waiting‐based performance measures are modified. Numerical results demonstrate the reliability of this Markovian performance approximation for different parameter settings. A sensitivity analysis shows the impact of the waiting‐time limit and the dependence of the performance measures on the arrival rate.
Improving Right Party Contact Rates at Outbound Call Centers
Authors: Bollapragada Srinivas , Nair Suresh K.
Published: August 2010

Consumer delinquencies are a major problem for banks and other credit card issuers. These firms have collection centers across the country to collect outstanding balances from delinquent accounts. Their main strategy is to first send reminder notices and, if that does not work, to telephone delinquent customers and request payment. The latter often becomes necessary, resulting in high costs of collection. Automated dialers are used to make the calls, and when the call goes through, it is directed to one of several hundred associates manning computer workstations. In this operation, it is important to contact the account holder in order to discuss payment options. Simply getting someone on the line is not sufficient, because such calls would require follow‐up calls. The objective of efficient collections is to maximize dollars collected while minimizing costs, which generally translates to making a “right party contact (RPC)” in the minimum number of attempts. We developed and tested an algorithm that increased the RPC rates by over 10%. This increase translates to annual savings of several million dollars for an average credit card company. Although the focus of our paper is collections, the methodology developed is equally applicable for improving telemarketing efficiency.
Distances between thoracic spinous processes in Warmblood foals: A radiographic study
Authors: SINDING M. F. , BERG L. C.
Published: August 2010

Reason for performing study:The aetiological factors behind impinged or overriding of dorsal spinous processes (‘kissing spine syndrome’, KSS) are not clearly understood. Back conformation, breed, age, training and gender may play important roles in this condition. Radiographic changes vary and abnormalities are seen in many clinically normal horses, but the conclusion of previous studies in mature horses is that interspinous spaces <4 mm are considered too narrow and potentially indicative of KSS.

Objectives:To evaluate whether narrowing of the interspinous space was present in a population of normal Warmblood foals.

Materials and methods:The mean interspinous space width in the area of T10–L1 was measured on radiographs from 25 Warmblood foals aged 9–88 days.

Results:Mean ± s.d. interspinous space width was found to be between 5.9 ± 1.2 and 8.9 ± 2.6 mm with the narrowest space in the area T16–T17 and the widest space in T10–T12. No interspinous spaces were <4 mm wide. Gender and location of the interspinous space significantly affected the width of the distance between the spinous processes.

Conclusions and potential relevance:In this study none of the interspinous spaces were <4 mm and therefore none of the foals showed signs of impinged or overriding of dorsal spinous processes known as KSS based on the current definitions. Consequently, in this population, there did not appear to be a congenital narrowing of the interspinous space. However, long‐term follow‐up studies, including detailed information on imposed factors such as training, are needed in order to further elucidate a possible congenital component in the aetiology of KSS.
Report of the Second Havemeyer EHV‐1 Workshop, Steamboat Springs, Colorado, USA, September 2008
Authors: KYDD J. H. , SLATER J. , OSTERRIEDER N. , ANTCZAK D. F. , LUNN D. P.
Published: August 2010

This report summarises the findings of the Second Havemeyer EHV‐1 Workshop, which was held in Steamboat Springs, Colorado, USA in September 2008. A total of 38 delegates, consisting of veterinary clinicians and scientists from academia and industry participated in a series of sessions that focused on equine herpesvirus myeloencephalopathy (EHM). Each session consisted of a review, followed by short presentations on current research topics. The sessions included EHM epidemiology, in vivo and in vitro models for studying EHM, EHV‐1 virulence determinants, real‐time PCR diagnostics, antiviral medications and new vaccination technologies. The report summarises the key advances identified during and since the meeting. Citations are restricted to selected reviews and papers published since the workshop.
The rank of a hypergeometric system
Authors: Berkesch Christine
Published: August 2010

The holonomic rank of the A-hypergeometric system MA(β) is the degree of the toric ideal IA for generic parameters; in general, this is only a lower bound. To the semigroup ring of A we attach the ranking arrangement and use this algebraic invariant and the exceptional arrangement of non-generic parameters to construct a combinatorial formula for the rank jump of MA(β). As consequences, we obtain a refinement of the stratification of the exceptional arrangement by the rank of MA(β) and show that the Zariski closure of each of its strata is a union of translates of linear subspaces of the parameter space. These results hold for generalized A-hypergeometric systems as well, where the semigroup ring of A is replaced by a non-trivial weakly toric module M⊆ℂ[ℤA] . We also provide a direct proof of the main result in [M. Saito, Isomorphism classes of A-hypergeometric systems, Compositio Math. 128 (2001), 323–338] regarding the isomorphism classes of MA (β) .
Influence of Microstructural Inhomogeneity on the Formability and Fracture of a Carbon Steel
Authors: Mitani N. Yoshito
Published: August 2010

The dependence of drawability in carbon steel on the grain size shows that a finer grain size is desirable for the better production. On the other hand, the characteristics of fracture in Olsen cup test are determined by the microstructural inhomogeneity. Several microstructures are prepared by adequate heat treatment and the formability and fracture mode are examined from the point of view of microstructural inhomogeneity. Good correlation between the second phase distribution and the formability in deep drawing is obtained. An anisotropic factor R/ΔR also well explains the formability.
Reliability as a Materials Property
Authors: Bondi A. A.
Published: August 2010

The introduction of new materials for use in load-bearing applications in a marketplace with very high standards of reliability poses an important design problem because designers had come to take the reliability of their materials for granted. Many decades of manufacturing development brought the commonly used metals to their present perfection. Given the even larger number of processing and innate property variables of the new engineering plastics and composites, they actually exhibit considerably wider dispersions of instantaneous strength properties as well as of fatigue characteristics. The data assembled in this paper suggest that one cannot foretell at present where the ultimately attainable reliability limits of different kinds of composites may be. Current attainments are then compared with the minimum reliability demands of some of the economically important applications foreseen for composites. Can the difference be made up by clever design or only by improved materials?
Use of Forming Limit Criteria in Forging Complex Shapes From Metal-Matrix Composites
Authors: Ertu¨rk Turgay , Kuhn Howard A.
Published: August 2010

Fundamental deformation and fracture behavior of fiber-reinforced metal-matrix composites under deformation processing conditions were determined using upset tests on rectangular specimens. Defects that occur during simulated forging of a 2024 Al-alloy matrix reinforced with 25v/o stainless steel wires were characterized, and forming limit criteria for their prediction and prevention established. These criteria, determining the limits of deformation, provided guidelines for development of a process for forging an airfoil shape from the composite system studied. To this end, the limiting criteria were combined with an analysis of the flow of metal during forging. The forging design method developed, based on the forming limit criteria, demonstrates a rational approach to the design of processes for forging complex shapes from composite materials. Utilizing this approach, process parameters (die and preform geometry, lubrication) can be evaluated for forging sound complex composite shapes.
Residual Fatigue Life Determination of Anchor Bolts
Authors: Mukherjee B.
Published: August 2010

A project was conducted to determine residual fatigue life of transmission tower anchor bolts. Notched and fatigue precracked round bar specimens were used to simulate anchor bolt fatigue and to determine fatigue life experimentally. Fatigue precracked compact tension specimens were used to determine fatigue crack growth rate properties using a fracture mechanics approach. The effect of temperature on crack growth rate was also investigated. A method to estimate fatigue life of surface cracked round bars was developed and predictions were compared against experimental results. This paper shows how a fracture mechanics approach can be used to estimate residual fatigue life of cracked anchor bolts.
A Description of History Dependent Plastic Flow Behavior of Anisotropic Metals
Authors: Lee D. , Zaverl F.
Published: August 2010

An analytical model that describes the loading-history-dependent hardening behavior of anisotropic metals is presented. The proposed hardening model assumes that the rate of change of primary material variables is dependent upon their limiting values, similar to the use of saturation back stress proposed by Rice. The primary material variables are defined by an anisotropic yield function characterizing “distortion,” “translation,” and “size” of the current yield surface. All the material parameters in the model have been obtained from experiments made with hourglass-type specimens loaded in tension and compression along different principal directions of anisotropy and under monotonic and load reversing conditions. Depending on the details of strain hardening characteristics, a set of secondary material variables was defined to describe the behavior at large plastic strains. Results of numerical analysis indicated that the simplified model based on the measured material parameters is capable of simulating the loading-history-dependent hardening behavior of anisotropic metals under uniaxial loading conditions. Sample simulations with Zircaloy-2 were compared with experimental data, and isotropic behavior was demonstrated with 304 stainless steel.
Analysis of Misalignment in the Tension Test
Authors: Wu Han C. , Rummler D. R.
Published: August 2010

Many experimenters fail to appreciate the significance of test system alignment during a tensile test. Poor alignment can increase data scatter and significantly influence some of the test results. In this paper a comprehensive analytical study of the misalignment problem in the plastic strain range is presented and errors caused by misalignment estimated. The results show that the stress-strain curve is not significantly affected by misalignment. However, the strains at the outer most fibers of the specimen cross-section are stongly affected by misalignment. Therefore, the effect of misalignment is most important when properties sensitive to local strain concentrations are being investigated.
Use of Fracture Mechanics Methods for Establishing Inspection Level for Turbine Wheels
Authors: Frishmuth R. E.
Published: August 2010

The establishment of inspection criteria for wheels in rotating machinery is frequently a complex issue. On one hand, safety and reliability of the parts and equipment must be assured while on the other, economical use must be made of available materials. In addition to these often opposing criteria, account must be taken of the limitations and cost of non-destructive evaluation methods. One way of considering all these factors and establishing safe inspection and acceptance criteria for wheels is to employ linear elastic fracture mechanics (LEFM) methods. The purpose of this paper is to outline a method for using LEFM to establish allowable stress levels or fracture toughness required in turbine wheel ferritic steels. The methods proposed are discussed in schematic fashion and it is shown that general application of a single “design curve” to many situations is possible if accuracy in specific cases is sacrificed. If this sacrifice is made so that results are conservative then the resulting plots can be used during the design of the wheel, the acceptance of a part or the evaluation of remaining life of an in-service wheel.
Materials Problems Experienced at the Synthane Coal-Gasification Pilot Plant
Authors: Danyluk S. , Dragel G. M. , Dubis D.
Published: August 2010

Some failure experiences with metallic components at the Synthane coal-gasification pilot plant are presented. In some cases, corrosion caused by a sulfur environment was a major factor in the failure initiation. Several instances of improper component manufacture or heat treatment led to failures. Chloride-assisted stress-corrosion cracking and an improper materials choice contributed to two cases of failure. In most cases, the recommended changes in materials, design or process conditions have resulted in an increase in component life.
Computed Dynamic Compaction of a Two-Layered Copper Powder Medium
Authors: Sano Yukio , Miyagi Kiyohiro
Published: August 2010

In the paper presented a dynamic compaction of a two-layered powder medium is analyzed. A two-layered medium is used because it is the simplest form of layered medium available. The layers are differentiated not in terms of different powdered materials but rather a difference in terms of initial-density (initial specific volume) distribution, that is a higher initial density distribution and a lower initial density distribution. Again for these initial density distributions, two forms of arrangement can be considered; for the first situation, the layer to be impacted has a lower initial density distribution, while for the second situation the arrangement is reversed. The objective of this paper, therefore, is to examine the effect that the initial density sequence has on the compaction process and on the green density of a layered powder medium, especially in terms of shock wave and elastic wave influence.
A Study of Cold Strip Rolling
Authors: Atreya Arvind , Lenard John G.
Published: August 2010

The effect of roll deformation on separating forces in cold strip rolling is studied. The deformed roll shape is determined by a two dimensional finite element routine. The results are then incorporated in an analysis of the mechanics of rolling. The technique consists of assembling individual slabs bounded by planes passing through nodal points on the arc of contact—for each of which an exact solution for the roll pressure is obtained. Comparison to the solution of Orowan’s equations shows that the present technique is reasonably accurate. Comparison to data from a preliminary set of experiments shows that the technique deserves further investigation.
Diametral Compressive Testing Method
Authors: Awaji Hideo , Sato Sennosuke
Published: August 2010

A new approach of diametral compressive testing with circular anvils is proposed. The circular anvils are used to select a suitable contact width or to avoid the collapse of the specimen in the contact edge. Furthermore, the statistical corrections on the diametral compressive strength for the effects of the size and stress distribution are explained by the application of Weibull’s statistical theory. The experimental results of the diametral compressive testing are compared with the uniaxial tensile strengths for some kinds of graphite and marble, and the discrepancies between the two strengths are discussed. According to our macroscopic brittle fracture criterion under biaxial stress state, which was proposed recently, the tensile strength can be deduced from the diametral compressive strength σHC* and the uniaxial compressive strength σC as follows, σt*=KICKIIC12σCσHC*(1+σx/σH)+σC{σHC*(1−σx/σH)−σC}+σC2 where σt* is the deduced tensile strength, σx/σH is the ratio of maximum and minimum principal stresses at the center of the disk, and KIC and KIIC are the values of Mode I and Mode II fracture toughness. The deduced values σt* are ascertained experimentally to agree very well with the uniaxial tensile strength in wide range of brittle materials, such as graphite and marble.
The Statistical Nature of Fatigue Crack Propagation
Authors: Virkler D. A. , Hillberry B. M. , Goel P. K.
Published: August 2010

A statistical investigation of the fatigue crack propagation process was conducted. Sixty-eight replicate constant amplitude crack propagation tests were conducted on 2024-T3 aluminum alloy. From the experimental data, the distribution of N was found to be represented best by the 3-parameter log-normal distribution. Six growth rate calculation methods were investigated and a modified secant method was found to introduce the least amount of error into the growth rate data. No one single distribution was found to describe the distribution of da/dN. A prediction scheme using the distribution parameters of da/dN was partially successful.
Dynamic Fracture Initiation: A Comparison of Two Experimental Methods
Authors: Costin L. S. , Server W. L. , Duffy J.
Published: August 2010

This paper presents a comparison of dynamic fracture initiation results obtained from two independent experimental methods: (1) the instrumented version of the precracked Charpy test and (2) a new dynamic fracture test developed at Brown University (BU). Dynamic fracture tests were conducted using both methods on 4340 steel at room temperature and on 1018 cold-rolled steel (CRS) at temperatures over the range −157 to 107°C. This range covered temperatures on the lower shelf, the transition regime, and the upper shelf of the transition temperature curve. Stress intensity rates of K˙I = 2.2 × 105 MN-m−3/2/s and K˙I = 2.2 × 106 MN-m−3/2/s were used in the instrumented precracked Charpy and BU tests, respectively. In the analysis of test results, both elastic (KIc) and elastic-plastic (J-integral) fracture parameters were computed. Results of the two test methods were found to be generally in good agreement, except that some differences were observed between 1018 CRS test results on the upper shelf. Possible reasons for these differences are discussed.
The Influence of Inclusions on the Toughness and Fatigue Properties of A516-70 Steel
Authors: Wilson A. D.
Published: August 2010

The influence of inclusions on the tensile ductility, upper shelf Charpy-V-notch, dynamic tear and J-integral fracture toughness and the fatigue crack propagation behavior and the fatigue endurance limit of A516-70 normalized, carbon plate steel is reported. Three plates made by conventional steelmaking techniques and 4 plates produced using calcium treatment are examined in thickness from 51 mm (2 in.) to 254 mm (10 in.) in up to 6 different testing orientations per plate. Quantitative image analysis is used to establish correlations between the measured mechanical properties and certain inclusion parameters. Inclusions were found to be detrimental to tensile ductility, upper shelf impact and fracture toughness, and the fatigue endurance limit with predominant effect found to be on the fracture toughness properties. Although inclusions were found to influence adversely the fatigue crack propagation behavior, the effect was not substantial in the steels studied. Quantitative image analysis was used to establish that the fatigue crack propagation behavior and tensile ductility are controlled by the average area of an inclusion on the metallographic cross-section corresponding to the plane of fracture, while the upper shelf toughness properties are controlled by the average length of an inclusion. In general A516-70 was found to be less sensitive to inclusions in both toughness and fatigue crack propagation behavior than A533B Class 1.
Stable and Unstable Fatigue Crack Propagation During High Temperature Creep-Fatigue in Austenitic Steels: The Role of Precipitation
Authors: Lloyd G. J. , Wareing J.
Published: August 2010

The distinction between stable and unstable fatigue crack propagation during high temperature creep-fatigue in austenitic stainless steels is introduced. The transition from one class of behavior to the other is related to the precipitate distribution and to the nature of the prevailing crack path. It is shown by reference to new studies and examples drawn from the literature that this behavior is common to both high strain and predominantly elastic fatigue in austenitic stainless steels. The relevance of this distinction to a mechanistic approach to high temperature plant design is discussed.
Application of Damage Concepts to Predict Creep-Fatigue Failures
Authors: Lemaitre J. , Plumtree A.
Published: August 2010

The damage concept has been developed in terms of strain range in order to give a unified approach to high temperature failure. Interactive tests have been carried out on OFHC copper at 540°C and Sanicro 31 (Alloy 800) at 600°C. For the former, combined strain controlled low frequency and high frequency tests were undertaken whereas the latter metal was subjected to sequential tests involving monotonic creep and high frequency cycling. The damage concept based on non-linear accumulation predicted lives which were in agreement with those observed experimentally for the two materials.
What Makes Usain Bolt Unique as a Sprinter?
Authors: Shinabargar A. J. , Hellrich Matt , Baker Blane
Published: August 2010

For both casual and avid fans alike, Olympic and other sporting events can provide a wealth of data for simple physics analyses. One of the most impressive performances in recent Olympic history is that of Usain Bolt in the track-and-field sprinting events during the 2008 Summer Games. Over a seven-day span, Bolt set world records in the 100-m and 200-m individual sprints and in the 4 × 100-m sprint relay. In addition, Bolt left us all wondering what record time he might have run had he not eased into the finish line in the 100-m dash. Naturally, one question many fans and observers immediately ask is: What makes Usain Bolt unique as a sprinter?
Designer Nuclei — Making Atoms that Barely Exist
Authors: Jones Kate L. , Nazarewicz Witold
Published: August 2010

The physics of nuclei is not a democratic field. It has to be said, some nuclei are just more interesting than others. And some are more useful than others, either to explain the origins of the elements, or the nature of matter itself, or for uses in medicine and other applied fields. The trick is to work out which nuclei are going to be the most important, and then go out and make them. Nuclear physicists are getting increasingly better in fabricating and characterizing short-lived nuclei with desired properties, the designer nuclei. This paper describes selected frontiers of this research. For an in-depth overview, the reader is referred to the recent report.1
A Measurement of g Using Alexander's Diving Bell
Authors: Quiroga M. , Martínez S. , Otranto S.
Published: August 2010

This paper describes a very simple exercise using an inverted test tube pushed straight down into a column of water to determine the free-fall acceleration g. The exercise employs the ideal gas law and only involves the measurement of the displacement of the bottom of the “diving bell” and the water level inside the tube with respect to the water column surface. The experiment is ideal for students in introductory physics courses.
Investigating Diffusion and Entropy with Carbon Dioxide-Filled Balloons
Authors: Jadrich James , Bruxvoort Crystal
Published: August 2010

Fill an ordinary latex balloon with helium gas and you know what to expect. Over the next day or two the volume will decrease noticeably as helium escapes from the balloon. So what happens when a latex balloon is filled with carbon dioxide gas? Surprisingly, carbon dioxide balloons deflate at rates as much as an order of magnitude faster than helium balloons. An investigation into the details of this phenomenon provides students with an excellent opportunity to apply the kinetic theory of gases and the ideal gas law, and it can also be exploited for a dramatic in-class demonstration of diffusion and the second law of thermodynamics.
Tracking Connections: An Exercise about Series and Parallel Resistances
Authors: Jankovic Srdjan
Published: August 2010

Unlike many other topics in basic physics, series and parallel resistances are rarely noticed in the real life of an ordinary individual, making it difficult to design a laboratory activity that can simulate something familiar. The activities described here entail minimal costs and are based on a puzzle-like game of tracking wire connections. A simple resistor-based device is built by students, which enables them to use a common multimeter to track down wire connections in a set of unmarked wires. A similar approach is sometimes used by electricians to identify wire connections.1
Rephrasing Faraday's Law
Authors: Hill S. Eric
Published: August 2010

As physics educators, we must often find the balance between simplicity and accuracy. Particularly in introductory courses, it can be a struggle to give students the level of understanding for which they're ready without misrepresenting reality. Of course, it's in these introductory courses that our students begin to construct the conceptual framework that they'll flesh out over a physics curriculum. So a misrepresentation at this early stage will seed difficulties and stubborn misconceptions that can persist or even strengthen through subsequent courses, especially since many upper-level texts focus more on techniques and would not directly challenge mistaken concepts. In the worst cases, our students retain misunderstandings past graduation, and even pass them on to their own students. One important case is the common representation of Faraday's law as showing that a time-varying magnetic field causes a circulating electric field.
Arginine Usage in Mycobacteria-Infected Macrophages Depends on Autocrine-Paracrine Cytokine Signaling
Authors: Qualls Joseph E. , Neale Geoffrey , Smith Amber M. , Koo Mi-Sun , DeFreitas Ashley A. , Zhang Huiyuan , Kaplan Gilla , Watowich Stephanie S. , Murray Peter J.
Published: August 2010

Mycobacteria trigger the production of cytokines that suppress immune responses in infected and uninfected macrophages.
More Than a Building Block
Authors: Adler Elizabeth M.
Published: August 2010

Phosphatidylcholine biosynthesis promotes ERK signaling and neurite formation in neuroblastoma cells.
Phosphatidylinositol 3-Kinase Signaling in Thymocytes: The Need for Stringent Control
Authors: Fayard Elisabeth , Moncayo Gerald , Hemmings Brian A. , Holländer Georg A.
Published: August 2010

PI3K signaling is important in the development of normal and malignant thymocytes.