bluuebunny/crossref_metadata_2025 huggingface dataset:
Conservation Strategies for Endemic Fish Species Threatened by the Three Gorges Dam
Authors: PARK YOUNG‐SEUK , CHANG JIANBO , LEK SOVAN , CAO WENXUAN , BROSSE SEBASTIEN
Published: December 2003

Abstract:  The largest damming project to date, the Three Gorges Dam has been built along the Yangtze River (China), the most species‐rich river in the Palearctic region. Among 162 species of fish inhabiting the main channel of the upper Yangtze, 44 are endemic and are therefore under serious threat of global extinction from the dam. Accordingly, it is urgently necessary to develop strategies to minimize the impacts of the drastic environmental changes associated with the dam. We sought to identify potential reserves for the endemic species among the 17 tributaries in the upper Yangtze, based on presence/absence data for the 44 endemic species. Potential reserves for the endemic species were identified by characterizing the distribution patterns of endemic species with an adaptive learning algorithm called a “self‐organizing map” (SOM). Using this method, we also predicted occurrence probabilities of species in potential reserves based on the distribution patterns of communities. Considering both SOM model results and actual knowledge of the biology of the considered species, our results suggested that 24 species may survive in the tributaries, 14 have an uncertain future, and 6 have a high probability of becoming extinct after dam filling.
An Environmental Domain Classification of New Zealand and Its Use as a Tool for Biodiversity Management
Authors: LEATHWICK J. R. , OVERTON J. McC , McLEOD M.
Published: December 2003

Abstract:  Successful biodiversity management, including the selection and subsequent management of protected areas, depends in large measure on classifications showing land areas with similar ecosystem character. In contrast to widely used, qualitative land‐classification techniques, we used a numerical classification of explicit spatial layers describing aspects of New Zealand's climate and landforms. We chose input variables for their strong functional links with major physiological processes of trees and high statistical correlations with geographic distributions of individual tree species as determined from previous studies. Higher‐level divisions of the resulting classification were dominated by macroclimatic variation associated with change in both latitude and orographic protection provided by New Zealand's main mountain ranges, but variation in landform became more important at finer scales of classification. Classification units showed marked variation in the proportional extent of both indigenous vegetation cover and land set aside for conservation purposes. Indigenous ecosystem remnants of the highest priority for increased protection occurred in warm, lowland domains, particularly in drier environments, where both indigenous cover and protected areas are of minimal geographic extent. Such results underline the considerable potential of an environmental classification to provide a landscape context for systematic conservation management, particularly in environments where the natural ecosystem pattern has been severely modified by human activity.
Response of Soil Fauna to Landscape Heterogeneity: Determining Optimal Scales for Biodiversity Modeling
Authors: CHUST G. , PRETUS J. L. , DUCROT D. , BEDÒS A. , DEHARVENG L.
Published: December 2003

Abstract:  The concept of scale is inherent to ecological processes that occur over landscapes. To address this issue, we examined the response of soil fauna (Collembola) to landscape heterogeneity at different spatial scales. We derived spatial features from satellite images of the Massif of Arize in the French Pyrenees. We developed a multiscale approach to test the effect of scale of the landscape pattern on species abundance and biodiversity, with a Mantel test and stepwise multiple linear regression analysis, respectively. We distinguished the effect of the “regional” habitat (landscape descriptors) on soil fauna, which is a spatially explicit concept, and that of the “local” habitat (topography and forest type). We carried out a variance‐partitioning analysis of species composition and richness to assess the relative contribution of regional and local habitat. The effect of the spatial structure on species abundance was especially strong at a well‐defined scale of 48 ha. The surrounding environment that primarily structured the soil fauna assemblages was vegetation cover, measured as the mean of a radiometric vegetation index. Our results show that regional habitat can play an important role in structuring species composition, which is frequently hidden when the scale component is not taken into consideration. Further, we modeled endemic Collembolan richness based on a combination of landscape features at two spatial scales (2.25 ha and 292 ha). The landscape descriptors accounted for 72% of endemic richness variance, although within that variation 41% is shared with local habitat and spatial terms. We used the linear regression model to extrapolate endemism scores over the landscape. Such spatial models could be powerful tools for the selection and delimitation of high‐biodiversity areas in conservation policies.
The Use of Bayesian Model Averaging to Better Represent Uncertainty in Ecological Models
Authors: WINTLE B. A. , McCARTHY M. A. , VOLINSKY C. T. , KAVANAGH R. P.
Published: December 2003

Abstract:  In conservation biology, uncertainty about the choice of a statistical model is rarely considered. Model‐selection uncertainty occurs whenever one model is chosen over plausible alternative models to represent understanding about a process and to make predictions about future observations. The standard approach to representing prediction uncertainty involves the calculation of prediction (or confidence) intervals that incorporate uncertainty about parameter estimates contingent on the choice of a “best” model chosen to represent truth. However, this approach to prediction based on statistical models tends to ignore model‐selection uncertainty, resulting in overconfident predictions. Bayesian model averaging (BMA) has been promoted in a range of disciplines as a simple means of incorporating model‐selection uncertainty into statistical inference and prediction. Bayesian model averaging also provides a formal framework for incorporating prior knowledge about the process being modeled. We provide an example of the application of BMA in modeling and predicting the spatial distribution of an arboreal marsupial in the Eden region of southeastern Australia. Other approaches to estimating prediction uncertainty are discussed.
Understanding PTSD: Forgetting “Trauma”
Authors: Ehrenreich John H.
Published: December 2003

The concept of “psychological trauma” conflates emotional responses to traumatic events such as motor vehicle accidents, muggings, and house fires, responses to natural disasters such as earthquakes and volcanic eruptions, and responses to war, chronic physical abuse, prolonged torture, and repeated gang‐rape as an act of “ethnic cleansing.” It is argued that, from a psychological, human, and moral perspective, use of a single construct to describe responses to such a range of horrific happenings makes no sense. The benefits and limits of conceptualizing PTSD as a unifying concept for describing psychological responses to calamitous events are discussed. The consequences (with respect to clinical work, research, and social policy) of failing to distinguish between responses to relatively circumscribed traumatic events, more extreme, prolonged, or repeated individual traumatization, and collectively experienced mass violence against entire communities are examined.
The Legalization of Abortion and Subsequent Youth Homicide: A Time Series Analysis
Authors: Berk Richard A. , Sorenson Susan B. , Wiebe Douglas J. , Upchurch Dawn M.
Published: December 2003

In this article, we examine the association between the legalization of abortion with the 1973 Roe v. Wade decision and youth homicide in the 1980s and 1990s. An interrupted time series design was used to examine the deaths of all U.S. 15‐ to 24‐year‐olds that were classified as homicides according to the International Classification of Diseases (codes E960‐969) from 1970 to 1998. The legalization of abortion is associated over a decade later with a gradual reduction in the homicides of White and non‐White young men. The effect on the homicides of young women is minimal. We conclude that the 1990s decline in the homicide of young men is statistically associated with the legalization of abortion. Findings are not consistent with several alternative explanations, such as changes in the crack cocaine drug market. It is almost inconceivable that in the United States of today, policies affecting the choice to have children would be justified as a means to control crime. Yet, if the legalization of abortion had this unintended effect, the full range of policy implications needs to be discussed.
Car Sharing: A New Approach to Urban Transportation Problems
Authors: Katzev Richard
Published: December 2003

The concept of car sharing is introduced as an innovative approach to the growing transportation problems of the major metropolitan areas of the United States. After the history of car sharing in Europe and North America is outlined, three studies of the early adopters of Car Sharing Portland (CSP), the first commercial car‐sharing organization in the United States, are reported. Study 1 found that these individuals were primarily motivated to join CSP because of their occasional need for a vehicle, and secondarily because of the financial savings they expected to realize by becoming members. Study 2 found that the two most important predictors of CSP trip usage were distance to the nearest vehicle station and length of membership, and that both factors had more influence on vehicle owners than on nonowners. Study 3 found that although members did not drive fewer vehicle miles after they joined CSP, 26% sold their personal vehicles and 53% were able to avoid an intended purchase. In addition, a majority of members reported increasing use of public transit, walking, and cycling. The results are discussed in terms of the potential environmental consequences of car sharing and the effects of the car‐sharing experience on mobility behavior.
The Gender Pay Gap: Concrete Indicator of Women's Progress Toward Equality
Authors: Lips Hilary M.
Published: December 2003

A male–female earnings gap has persisted through the last half century. Attempts to explain the disparity by attributing it to gender differences in work patterns reveal the unexamined assumption that male work patterns should form the basis of comparison. The gap affects full‐ and part‐time workers and appears within racial/ethnic groups, educational levels, and occupations, and across countries. Forecasting analyses show no convincing evidence that the gap is narrowing. Although the causes of the gender pay gap are complex, data on women's lower pay within educational levels and occupations and data on women's dramatically lower recognition in domains where their talents and achievements are equal to men's (e.g., literary awards) implicate the undervaluing of work associated with women. Approaches to narrowing the gap are discussed. As psychologists, we should address this problem because our expertise bears directly on the issues and because our discipline is increasingly populated by women.
Authoritarians, the Next Generation: Values and Bullying Among Adolescent Children of Authoritarian Fathers
Authors: Knafo Ariel
Published: December 2003

The author comments on an article by Altemeyer (2003). The implications of authoritarianism to social phenomena are extended to the values and bullying behaviors of adolescent children of authoritarian fathers. Eighty‐two authoritarian and 252 nonauthoritarian Israeli fathers participated with their adolescent children. Authoritarian fathers expected their children to give high importance to power, tradition, and conformity values and lower‐than‐average importance to benevolence, universalism, and self‐direction values. In comparison with offspring of nonauthoritarian fathers, offspring of authoritarian fathers gave more importance to power values and less importance to universalism values. Offspring of authoritarian fathers also tended to associate more with bully friends. The combination of high adolescent power values and their fathers' authoritarian parenting was associated with the highest degrees of bullying by adolescents. The social implications of the findings are discussed.
Are We Training Future Pain Specialists?
Authors: Livengood Janice M. , Johnson Benjamin W.
Published: December 2003

▪ Abstract:  The purpose of this study was to determine whether pain practices in Tennessee are training future pain specialists. Following IRB approval, a questionnaire designed for the study was administered to members of the TN Pain Society. Results indicate that none of the subjects are training residents at their pain practice and the majority are not training pain fellows. Few attendings reported having trained in a pain fellowship themselves and the majority are reportedly not engaged in continuing pain management education through national or international organizations, such as the American Pain Society (APS) or the International Association for the Study of Pain (IASP). Of concern is whether or not this sample reflects the nature of pain practices throughout the country. If so, will there be a shortage of pain residents and fellows in the near future? Will pain practices be opened and operated by those who are not trained to treat chronic pain? ▪
Is the Second Phase of the Formalin Test Useful to Predict Activity in Chronic Constriction Injury Models? A Pharmacological Comparison in Different Species
Authors: K Vissers , V Hoffmann , F Geenen , R Biermans , T Meert
Published: December 2003

▪ Abstract:  This study presents data of several reference drugs in rats and gerbils for both the second phase of the formalin test and the cold allodynia in animals with a constriction injury of the sciatic nerve. A pharmacological validation of the formalin test and the CCI model in gerbils was performed. It was evaluated whether the second phase of the formalin test could be used as a pharmacological screening to predict outcome in the cold plate test in CCI animals. Male Sprague Dawley and Wistar rats and male gerbils were used for both tests. For the formalin test, animals were injected in the right hind paw (5% formalin rat: 0.05 microl; gerbil: 0.01 microl) and flinching and licking or biting were recorded. For CCI testing, a Bennett operation was performed on the left hind paw 7 days before testing. Cold plate allodynia was evaluated before and after drug treatment. In rats, a good correlation between both test conditions for morphine, fentanyl, MK‐801 and flunarizine was found. Clonidine tends to have more activity in the second phase of the formalin test, whereas baclofen, tramadol, amitryptiline, ketamine and topiramate demonstrate to be more active in the cold plate. In gerbils, a good correlation between both test conditions for fentanyl and ketoprofen was found. Tramadol and CP‐96345 tend to have more activity in the second phase of the formalin test, whereas morphine, SR‐48968, SR‐142801 and R116301 demonstrates to be more active in the cold plate test. In the present acute test conditions, there is a correlation in the pharmacological activity in rats and gerbils for the tested compounds a correlation between the second phase of the formalin test and the cold allodynia in CCI animals is found. Comparing to human data the screening drugs tested in this study show a correlation between animal and human studies in these specific circumstances. Further validation studies are needed to make these correlations clinical applicable. ▪
The Numeric Rating Scale for Clinical Pain Measurement: A Ratio Measure?
Authors: Hartrick Craig T. , Kovan Juliann P. , Shapiro Sharon
Published: December 2003

▪ Abstract:  The Numeric Rating Scale (NRS‐11) has been widely used clinically for the assessment of pain. Its use for clinical research is controversial. Reports differ as to whether or not the NRS‐11 should be treated as a ratio pain measurement tool. This study compared the NRS‐11 to a ratio measure for pain assessment: the visual analog scale (VAS). Simultaneous pain measurements using these 2 scales were compared in clinical situations commonly encountered in a tertiary community hospital. Whereas linear relationships were noted in laboring patients and in postoperative patients with thoracic or abdominal incisions during cough, no such correlations were noted for the same postoperative patients at rest or for postoperative orthopedic patients. The NRS‐11 should not be considered to be interchangeable with the VAS. Its use for clinical research should be limited to situations where it has specifically demonstrated linear properties. ▪
Treatment of Chronic Pain with Zonisamide
Authors: Krusz John Claude
Published: December 2003

▪ Abstract:  Mechanistic similarities underlying neuropathic pain and epilepsy suggest that anticonvulsants can be used for treating neuropathic pain. This open‐label prospective study assesses the use of zonisamide in patients with chronic neuropathic pain. Fifty‐five patients were initiated on zonisamide, given 100 mg every fourth night and titrated to a stable maintenance dosage (mean=285 mg/d, range=100 to 700 mg/d). Patients rated their pain on a 0 to 10 scale in pain diaries. After ≥3 months on a stable maintenance zonisamide dosage, pain ratings were compared with baseline. Adverse events (AEs) were monitored. Forty‐two patients had efficacy data available. Fifteen patients (35.7%) had a >50% improvement in daily pain scores; 10 patients (23.8%) had a 25% to 50% improvement. Zonisamide was well tolerated; only 5 patients discontinued for AEs (drowsiness, nausea, and itching). These results suggest that zonisamide may be useful for treating neuropathic pain. Further investigation in double‐blind, placebo‐controlled trials is warranted. ▪
Internal and External Factors Affecting the Development of Neuropathic Pain in Rodents. Is It All About Pain?
Authors: Vissers K. , De Jongh R. , Hoffmann V. , Heylen R. , Crul B. , Meert T.
Published: December 2003

▪ Abstract:  It is important to know the factors that will influence animal models of neuropathic pain. A good reproducibility and predictability in different strains of animals for a given test increases the clinical relevance and possible targeting. An obligatory requirement for enabling comparisons of results of different origin is a meticulous definition of the specific sensitivities of a model for neuropathic pain and a description of the test conditions.

Factors influencing neuropathic pain behavior can be subdivided in external and internal factors. The most important external factors are; timing of the measurement of pain after induction of neuropathy, circadian rhythms, seasonal influences, air humidity, influence of order of testing, diet, social variables, housing and manipulation, cage density, sexual activity, external stress factors, and influences of the experimenter. The internal factors are related to the type of animal, its genetic background, gender, age, and the presence of homeostatic adaptation mechanisms to specific situations or stress. In practice, the behavioral presentations to pain depend on the combination of genetic and environmental factors such as accepted social behavior. It also depends on the use of genetic manipulation of the animals such as in transgenic animals. These make the interpretation of data even more difficult. Differences of pain behavior between in‐ and outbred animals will be better understood by using modern analysis techniques. Substrains of animals with a high likelihood for developing neuropathic pain make the unraveling of specific pathophysiolocal mechanisms possible. Concerning the effect of stress on pain, it is important to differentiate between external and internal stress such as social coping behavior. The individual dealing with this stress is species sensitive, and depends on the genotype and the social learning.

In the future, histo‐immunological and genetic analysis will highlight similarities of the different pathophysiological mechanisms of pain between different species and human subjects. The final objective for the study of pain is to describe the genetics of the eliciting pain mechanisms in humans and to look for correlations with the knowledge from basic research. Therefore, it is necessary to know the genetic evolution of the different mechanisms in chronic pain. In order to be able to control the clinical predictability of a putative treatment the evolutionary pharmacogenomic structure of specific transmitters and receptors must be clarified. ▪
Diagnosis and Management of the Painful Ankle/Foot. Part 2: Examination, Interpretation, and Management
Authors: Sizer Phillip S. , Phelps Valerie , Dedrick Greg , James Roger , Matthijs Omer
Published: December 2003

▪ Abstract:  Diagnosis, interpretation, and subsequent management of ankle/foot pathology can be challenging to clinicians. A sensitive and specific physical examination is the strategy of choice for diagnosing selected ankle/foot injuries and additional diagnostic procedures, at considerable cost, may not provide additional information for clinical diagnosis and management. Because of a distal location in the sclerotome and the reduced convergence of afferent signals from this region to the dorsal horn of the spinal cord, pain reference patterns are low and the localization of symptoms is trustworthy. Effective management of the painful ankle/foot is closely linked to a tissue‐specific clinical examination. The examination of the ankle/foot should include passive and resistive tests that provide information regarding movement limitations and pain provocation. Special tests can augment the findings from the examination, suggesting compromises in the structural and functional integrity of the ankle/foot complex. The weight bearing function of the ankle/foot compounds the clinician's diagnostic picture, as limits and pain provocation are frequently produced only when the patient attempts to function in weight bearing. As a consequence, clinicians should consider this feature by implementing numerous weightbearing components in the diagnosis and management of ankle/foot afflictions. Limits in passive motion can be classified as either capsular or non‐capsular patterns. Conversely, patients can present with ankle/foot pain that demonstrates no limitation of motion. Bursitis, tendopathy, compression neuropathy, and instability can produce ankle/foot pain that is challenging to diagnose, especially when they are the consequence of functional weight bearing. Numerous non‐surgical measures can be implemented in treating the painful ankle/foot, reserving surgical interventions for those patients who are resistant to conservative care. ▪
Forty Years of Civil Jury Verdicts
Authors: Seabury Seth A. , Pace Nicholas M. , Reville Robert T.
Published: December 2003

Debate over civil justice reform in the United States frequently centers on the extent to which damage awards granted by juries have been escalating over time. However, past studies on civil juries have been hampered by lack of data on verdicts spanning a sufficiently long time period. Average jury awards tend to be highly variable from year to year, making it difficult to distinguish trends over relatively short periods of time. We use the longest time series of data on jury verdicts ever assembled: 40 years of data on tort cases in San Francisco County, CA and Cook County, IL collected by the RAND Institute for Civil Justice. We find that while there has been a substantial increase in the average award amount in real dollars, much of this trend is explained by changes in the mix of cases, particularly a decreasing fraction of automobile cases and an increase in medical malpractice. Claimed economic losses, in particular claimed medical losses, also explain a great deal of the increase. Although there appears to be some unexplained growth in awards for certain types of cases, this growth is cancelled out on average by declines in awards in other types of cases.
Attorney Fees in Class Action Settlements: An Empirical Study
Authors: Eisenberg Theodore , Miller Geoffrey P.
Published: December 2003

Study of two comprehensive class action case data sets covering 1993–2002 shows that the amount of client recovery is overwhelmingly the most important determinant of the attorney fee award. Even in cases in which the courts engage in the lodestar calculation (the product of reasonable hours and a reasonable hourly rate), the client's recovery generally explains the pattern of awards better than the lodestar. Thus, the time and expense of a lodestar calculation may be wasteful. We also find no robust evidence that either recoveries for plaintiffs or fees of their attorneys increased over time. The mean fee award in common fund cases is well below the widely quoted one‐third figure, constituting 21.9 percent of the recovery across all cases for a comprehensive data set of published cases. A scaling effect exists: fees constitute a lower percent of the client's recovery as the client's recovery increases. Fees are also correlated with risk: the presence of high risk is associated with a higher fee, while low‐risk cases generate lower fees. Fees as a percent of class recovery were found to be higher in federal than state court. The presence of “soft” relief (such as injunctive relief or coupons) has no material effect on the fee, regardless of whether the soft relief was included in the quantified benefit for the class used as the basis for computing the attorney fee. The study also addresses costs and expenses. Like fees, these display significant scale effects. The article proposes a simple methodology by which courts can evaluate the reasonableness of fee requests.
Determinants of Civil Rights Filings in Federal District Court by Jail and Prison Inmates
Authors: Piehl Anne Morrison , Schlanger Margo
Published: December 2003

This article uses panel data estimation techniques to examine the relation between the number of federal court civil filings by inmates and jail and state prison populations (and, hence, the relation between jail and prison inmate filing rates) both before and after the effective date, in 1996, of the Prison Litigation Reform Act (PLRA). The research issue matters for several reasons. First, the amount of litigation by inmates is a crucial component of the regulatory regime governing jails and prisons and thus what factors drive filings, and by how much, deserves close attention and assessment. In addition, the PLRA was a major congressional attempt to control and ration litigation; understanding its effects in finer gauge seems itself worthwhile. Finally, we hope to show, methodologically, how research about litigation rates can be carried out sensitively, even if the litigation results from case filings by two separate populations. We make three major findings. (1) As expected, inmate filings vary positively with prison population. However, the relationship with jail population is less secure. (2) As the prison proportion of inmates in a particular state increases, so too does the number of filings. (3) The PLRA's passage has significantly lessened but not eliminated this prison proportion effect.
The Determinants of Professional Fees in Large Bankruptcy Reorganization Cases
Authors: LoPucki Lynn M. , Doherty Joseph W.
Published: December 2003

This article reports on one of the most extensive studies to date of the professional fees and expenses awarded by U.S. bankruptcy courts in the reorganizations of large, public companies.
Empirical Estimates of Filtering Failure in Court‐Supervised Reorganization
Authors: Fisher Timothy C.G. , Martel Jocelyn
Published: December 2003

We present the first comprehensive empirical estimates of filtering failure in court‐supervised reorganization. Using a sample of 303 firms attempting reorganization in Canada during 1977–1988, we find that Type I errors (accepting a plan from a nonviable firm) are four times more likely to occur than Type II errors (rejecting a plan from a viable firm) and that the incidence of filtering failure is between 22 and 53 percent or 18 and 44 percent, depending on the definition of a firm's viability.
Explaining Death Row's Population and Racial Composition
Authors: Blume John , Eisenberg Theodore , Wells Martin T.
Published: December 2003

Twenty‐three years of murder and death sentence data show how murder demographics help explain death row populations. Nevada and Oklahoma are the most death‐prone states; Texas's death sentence rate is below the national mean. Accounting for the race of murderers establishes that black representation on death row is lower than black representation in the population of murder offenders. This disproportion results from reluctance to seek or impose death in black defendant‐black victim cases, which more than offsets eagerness to seek and impose death in black defendant‐white victim cases. Death sentence rates in black defendant‐white victim cases far exceed those in either black defendant‐black victim cases or white defendant‐white victim cases. The disproportion survives because there are many more black defendant‐black victim murders, which are underrepresented on death row, than there are black defendant‐white victim murders, which are overrepresented on death row.
Effect of Schmidt number on small-scale passive scalar turbulence
Authors: Antonia RA , Orlandi P
Published: November 2003

Previous reviews of the behavior of passive scalars which are convected and mixed by turbulent flows have focused primarily on the case when the Prandtl number Pr, or more generally, the Schmidt number Sc is around 1. The present review considers the extra effects which arise when Sc differs from 1. It focuses mainly on information obtained from direct numerical simulations of homogeneous isotropic turbulence which either decays or is maintained in steady state. The first case is of interest since it has attracted significant theoretical attention and can be related to decaying turbulence downstream of a grid. Topics covered in the review include spectra and structure functions of the scalar, the topology and isotropy of the small-scale scalar field, as well as the correlation between the fluctuating rate of strain and the scalar dissipation rate. In each case, the emphasis is on the dependence with respect to Sc. There are as yet unexplained differences between results on forced and unforced simulations of homogeneous isotropic turbulence. There are 144 references cited in this review article.
Computational strategies for flexible multibody systems
Authors: Wasfy Tamer M , Noor Ahmed K
Published: November 2003

The status and some recent developments in computational modeling of flexible multibody systems are summarized. Discussion focuses on a number of aspects of flexible multibody dynamics including: modeling of the flexible components, constraint modeling, solution techniques, control strategies, coupled problems, design, and experimental studies. The characteristics of the three types of reference frames used in modeling flexible multibody systems, namely, floating frame, corotational frame, and inertial frame, are compared. Future directions of research are identified. These include new applications such as micro- and nano-mechanical systems; techniques and strategies for increasing the fidelity and computational efficiency of the models; and tools that can improve the design process of flexible multibody systems. This review article cites 877 references.
Rotor Configuration Effects on the Performance of a HAWT With Tip-Mounted Mie-Type Vanes
Authors: Shimizu Y. , Ismaili E. , Kamada Y. , Maeda T.
Published: November 2003

In this paper, the relationships between the power augmentation of a HAWT due to Mie-type tip vane application and other factors influencing the efficiency of a wind turbine such as the blade aspect ratio, number of blades, blade pitch angle and Reynolds number are investigated. Experiments were carried out in a wind tunnel with an open, 3.6 m diameter, test section. Rotor models included two- and three-blade upwind turbines with four sets of blades with different aspect ratios. With the rotor blades tested, a maximum power augmentation of about 14.5% was achieved due to Mie vane application. The relationships between power augmentation due to the Mie vane and the above factors are investigated. It is found that the application of a tip-mounted Mie vane results in a larger increase in maximum power coefficient for rotors with smaller aspect ratios and for lower wind speeds. Surface oil film and surface tuft visualization methods were used to detect the flow patterns at the blade tip. Addition of the Mie vanes causes significant changes in flow behavior near the blade tip, resulting in additional blade lift.
Periodic Disturbance Accommodating Control for Blade Load Mitigation in Wind Turbines
Authors: Stol Karl A. , Balas Mark J.
Published: November 2003

Performance of a model-based periodic gain controller for wind turbines is presented using Disturbance Accommodating Control (DAC) techniques to estimate fluctuating wind disturbances. The control objective is to regulate rotor speed at above-rated wind speeds while mitigating cyclic blade root loads. Actuation is via individual blade pitch, and sensors are limited to rotor angle and speed. The modeled turbine is a two-bladed, downwind machine with simple blade and tower flexibility having four degrees of freedom. Comparisons are made to a time-invariant DAC controller and to a proportional-integral-derivative (PID) design. Simulations are performed using a fluctuating wind input and a nonlinear turbine model. Results indicate that the state-space control designs are effective in reducing blade loads without a sacrifice in speed regulation. The periodic controller shows the most potential because it uses a time-varying turbine model to estimate unmeasured states. The use of additional sensors to help reconstruct the blade flap rate can significantly improve the level of load attenuation, as witnessed in full-state feedback results.
Design of State-Space-Based Control Algorithms for Wind Turbine Speed Regulation
Authors: Wright Alan D. , Balas Mark J.
Published: November 2003

Control can improve the performance of wind turbines by enhancing energy capture and reducing dynamic loads. At the National Renewable Energy Laboratory, we are beginning to design control algorithms for regulation of turbine speed and power using state-space control designs. In this paper, we describe the design of such a control algorithm for regulation of rotor speed in full-load operation (Region 3) for a two-bladed wind turbine. We base our control design on simple linear models of a turbine, which contain rotor and generator rotation, drive train torsion, rotor flap (first mode only), and tower fore-aft degrees of freedom (DOFs). Wind-speed fluctuations are accounted for using Disturbance Accommodating Control (DAC). We show the capability of these control schemes to stabilize the modeled turbine modes via pole placement, while using state estimation to reduce the number of turbine measurements that are needed for these algorithms. These controllers are incorporated into a simulation code and simulated for various conditions. Finally, conclusions to this work and future studies are outlined.
Dynamic Simulation of a Wind Farm With Variable-Speed Wind Turbines
Authors: Muljadi E. , Butterfield C. P.
Published: November 2003

Wind power generation has increased very rapidly in the past few years. The total U.S. wind power capacity by the end of 2002 was 4,685 megawatts. As wind power capacity increases, it becomes increasingly important to study the impact of wind farm output on the surrounding power networks. In this paper, we attempt to simulate a wind farm by including the properties of the wind turbine, the wind speed time series, the characteristics of surrounding power network, and reactive power compensation. Mechanical stress and fatigue load of the wind turbine components are beyond the scope this paper. The paper emphasizes the impact of the wind farms on the electrical side of the power network. We investigate a typical wind farm with variable-speed wind turbines connected to an existing power grid. We also examine different control strategies for feeding wind energy into the power network and present the advantages and disadvantages.
Optimization of Wind Turbines Using Helicoidal Vortex Model
Authors: Chattot Jean-Jacques
Published: November 2003

The problem of the design of a wind turbine for maximum output is addressed from an aerodynamical point of view. It is shown that the optimum inviscid design, based on the Goldstein model, satisfies the minimum energy condition of Betz only in the limit of light loading. The more general equation governing the optimum is derived and an integral relation is obtained, stating that the optimum solution satisfies the minimum energy condition of Betz in the Trefftz plane “in the average.” The discretization of the problem is detailed, including the viscous correction based on the 2-D viscous profile data. A constraint is added to account for the thrust on the tower. The minimization problem is solved very efficiently by relaxation. Several optimized solutions are calculated and compared with the National Renewable Energy Laboratory (NREL) rotor, using the same profile, but different chord and twist distributions. In all cases, the optimization produces a more efficient design.
Boundary Layer State and Flow Field Structure Underlying Rotational Augmentation of Blade Aerodynamic Response
Authors: Schreck S. , Robinson M.
Published: November 2003

Blade rotation routinely and significantly augments aerodynamic forces during zero yaw horizontal axis wind turbine (HAWT) operation. To better understand the flow physics underlying this phenomenon, time dependent blade surface pressure data were acquired from the National Renewable Energy Laboratory (NREL). Unsteady Aerodynamics Experiment (UAE), a full-scale HAWT tested in the NASA Ames 80-by-120-foot wind tunnel. Time records of surface pressures and normal force were processed to obtain means and standard deviations. Surface pressure means and standard deviations were analyzed to identify boundary layer separation and shear layer impingement locations. Separation and impingement kinematics were then correlated with normal force behavior. Results showed that rotational augmentation was linked to specific separation and impingement behaviors, and to associated three-dimensionality in surface pressure distributions.
Navier-Stokes and Comprehensive Analysis Performance Predictions of the NREL Phase VI Experiment
Authors: Duque Earl P. N. , Burklund Michael D. , Johnson Wayne
Published: November 2003

A lifting-line code, CAMRAD II, and a Reynolds-Averaged Navier-Stokes code, OVERFLOW-D, were used to predict the aerodynamic performance of a two-bladed horizontal axis wind turbine. All computations were compared with experimental data that was collected at the NASA Ames Research Center 80-by-120-foot Wind Tunnel. Lifting-line computations were performed for both axial and yawed operating conditions while the Navier-Stokes computations were performed for only the axial conditions. Various stall delay models and dynamic stall models were used by the CAMRAD II code. For axial operating conditions, the predicted rotor performance varied significantly, particularly for stalled wind speeds. The lifting-line required the use of stall delay models to obtain the proper stall behavior, yet it still has difficulty in predicting the proper power magnitude in stall. The Navier-Stokes method captures the stall behavior and gives a detailed insight into the fluid mechanics of the stall behavior.
New Fatigue Data for Wind Turbine Blade Materials
Authors: Mandell John F. , Samborsky Daniel D. , Wang Lei , Wahl Neil K.
Published: November 2003

This paper reports on recent fatigue data of interest to the wind turbine industry in several areas: (a) very high-cycle fatigue data; (b) refined Goodman Diagram; (c) effects of fiber waviness; and (d) large-tow carbon fibers. Tensile fatigue results from a specialized high-frequency small strand testing facility have been carried out to 1010 cycles in some cases, beyond the expected cycle range for turbines. While the data cannot be used directly in design due to the specialized test specimen, the data trends help to clarify the proper models for extrapolating from standard coupons to higher cycles. The results for various fiber and matrix systems also provide insight into basic failure mechanisms. For spectrum loading predictions, a more detailed Goodman Diagram has been developed with additional R-values (R is the ratio of minimum to maximum stress in a cycle). The data of greatest interest were obtained for tensile fatigue with low cyclic amplitudes, close to R=1.0, to clarify the shape of the diagram as the cyclic amplitude approaches zero. These data may significantly shorten lifetime predictions compared with traditional Goodman Diagram constructions based on more limited data. The effects of material/process induced flaws on properties continues to be a major concern, particularly with large-tow carbon fabrics. The results of a study of fiber waviness effects on compressive strength show significant strength reductions for severe waviness which can be introduced in resin infusion processes. The final section presents new fatigue results for large-tow carbon/fiberglass hybrid composites. Epoxy resin laminates show marginally higher compressive strength and fatigue resistance with carbon fibers. Improved compressive static and fatigue performance is found with stitched fabrics as compared with woven fabrics.
Prediction of Delamination in Wind Turbine Blade Structural Details
Authors: Mandell John F. , Cairns Douglas S. , Samborsky Daniel D. , Morehead Robert B. , Haugen Darrin J.
Published: November 2003

Delamination between plies is the root cause of many failures of composite material structures such as wind turbine blades. Design methodologies to prevent such failures have not been widely available for the materials and processes used in blades. This paper presents simplified methodologies for the prediction of delamination in typical structural details in blades under both static and fatigue loading. The methodologies are based on fracture mechanics. The critical strain-energy release rate, GIC and GIIC, are determined for opening mode (I) and shearing mode (II) delamination cracks; fatigue crack growth in each mode is also characterized. These data can be used directly for matrix selection and as properties for the prediction of delamination in structural details. The strain-energy release rates are then determined for an assumed interlaminar flaw in a structural detail. The flaw is positioned based on finite-element analysis (FEA), and the strain-energy release rates are calculated using the virtual crack closure feature available in codes like ANSYS®. The methodologies have been validated for a skin-stiffener intersection. Two prediction methods differing in complexity and data requirements have been explored. Results for both methods show good agreement between predicted and experimental delamination loads under both static and fatigue loading.
Roughness Sensitivity Considerations for Thick Rotor Blade Airfoils
Authors: van Rooij R. P. J. O. M. , Timmer W. A.
Published: November 2003

In modern wind turbine blades, airfoils of more than 25% thickness can be found at mid-span and inboard locations. At mid-span, aerodynamic requirements dominate, demanding a high lift-to-drag ratio, moderate to high lift and low roughness sensitivity. Towards the root, structural requirements become more important. In this paper, the performance for the airfoil series DU FFA, S8xx, AH, Risø and NACA are reviewed. For the 25% and 30% thick airfoils, the best performing airfoils can be recognized by a restricted upper-surface thickness and an S-shaped lower surface for aft-loading. Differences in performance of the DU 91-W2-250 (25%), S814 (24%) and Risø-A1-24 (24%) airfoils are small. For a 30% thickness, the DU 97-W-300 meets the requirements best. Reduction of roughness sensitivity can be achieved both by proper design and by application of vortex generators on the upper surface of the airfoil. Maximum lift and lift-to-drag ratio are, in general, enhanced for the rough configuration when vortex generators are used. At inboard locations, 2-D wind tunnel tests do not represent the performance characteristics well because the influence of rotation is not included. The RFOIL code is believed to be capable of approximating the rotational effect. Results from this code indicate that rotational effects dramatically reduce roughness sensitivity effects at inboard locations. In particular, the change in lift characteristics in the case of leading edge roughness for the 35% and 40% thick DU airfoils, DU 00-W-350 and DU 00-W-401, respectively, is remarkable. As a result of the strong reduction of roughness sensitivity, the design for inboard airfoils can primarily focus on high lift and structural demands.
Output Power Correlation Between Adjacent Wind Power Plants*
Authors: Wan Yih-huei , Milligan Michael , Parsons Brian
Published: November 2003

The National Renewable Energy Laboratory (NREL) started a project in 2000 to record long-term, high-frequency (1-Hz) wind power data from large commercial wind power plants in the Midwestern United States. Outputs from about 330 MW of installed wind generating capacity from wind power plants in Lake Benton, MN, and Storm Lake, Iowa, are being recorded. Analysis of the collected data shows that although very short-term wind power fluctuations are stochastic, the persistent nature of wind and the large number of turbines in a wind power plant tend to limit the magnitude of fluctuations and rate of change in wind power production. Analyses of power data confirms that spatial separation of turbines greatly reduces variations in their combined wind power output when compared to the output of a single wind power plant. Data show that high-frequency variations of wind power from two wind power plants 200 km apart are independent of each other, but low-frequency power changes can be highly correlated. This fact suggests that time-synchronized power data and meteorological data can aid in the development of statistical models for wind power forecasting.
Probabilistic Analysis of LIST Data for the Estimation of Extreme Design Loads for Wind Turbine Components*†
Authors: Pandey M. D. , Sutherland H. J.
Published: November 2003

The robust estimation of wind turbine design loads for service lifetimes of 30 to 50 years that are based on limited field measurements is a challenging problem. Estimating the long-term load distribution involves the integration of conditional distributions of extreme loads over the mean wind speed and turbulence intensity distributions. However, the accuracy of the statistical extrapolation can be sensitive to both model and sampling errors. Using measured inflow and structural data from the Long Term Inflow and Structural Test (LIST) program, this paper presents a comparative assessment of extreme loads using three distributions: namely, the Gumbel, Weibull and Generalized Extreme Value distributions. The paper uses L-moments, in place of traditional product moments, with the purpose of reducing the sampling error. The paper discusses the effects of modeling and sampling errors and highlights the practical limitations of extreme value theory.