bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Lending Practices on the Foreclosure Crisis: Evidence from Indiana and Ohio
Authors: Yilmazer Tansel , Babiarz Patryk , Kiss D. E.
Published: May 2012

The goal of this study was to understand the role of loan approval and denial decisions and interest rates on mortgage defaults. The researchers identified the effect of lending practices on mortgage defaults by exploiting the variation in foreclosure rates across counties in Indiana and Ohio. The foreclosure rates were calculated using data from different sources of foreclosure listings. The loan approval–denial decisions and loan characteristics were obtained from the Home Mortgage Disclosure Act (HMDA) data. The analysis also attempted to understand the characteristics of “unqualified borrowers” who were extended credit before the foreclosure crisis. The findings showed that the counties that had higher loan approvals and positive interest rate spread had higher foreclosure rates. However, foreclosure rates did not seem to be correlated with loan‐to‐income ratios and the magnitude of the interest rate spread. The findings also suggested that the applicant’s income or the ratio of debt‐to‐applicant’s income was not sufficient to identify the unqualified borrowers who were extended mortgage loans.
Employment and real macroeconomic stability: The regressive role of financial flows in Latin America
Authors: FFRENCH‐DAVIS Ricardo
Published: May 2012

The author examines economic reforms carried out in Latin America since the 1990s. Price stabilization was achieved, but there has been insufficient growth and economic instability has been detrimental to productive investment and employment. Frequent crises have had a serious recessionary effect and have discouraged capital formation and the creation of decent jobs. Financial capital flows were the chief cause of this general economic situation. A positive recovery in 2010 resumed the climb towards progress begun in the 2004–08 period, but was accompanied by high levels of precarious employment and serious deficiencies in macroeconomic policy.
Deer herbivory as an important driver of divergence of ground vegetation communities in temperate forests
Authors: Suzuki Maki , Miyashita Tadashi , Kabaya Hajime , Ochiai Keiji , Asada Masahiko , Kikvidze Zaal
Published: May 2012

Ungulate herbivory can fundamentally affect terrestrial vegetation at the landscape and regional levels, but its impact has never been analyzed from meta‐community perspectives. Here, we study a meta‐community of forest ground‐layer plants in a warm‐temperate region along a clear gradient of deer density interplaying with gradients of other environmental factors (forest type, sky openness and topographic wetness). Canonical corresponding analysis showed that deer density was the most important determinant of species distributions. These distributions conformed to a two‐directional filtering model, which selects for competitive species at low deer density but favours herbivory‐tolerant plants at high deer density, with these two directions counterbalancing each other when herbivory is intermediary. This resulted in a bi‐directionally nested meta‐community, in which local species richness was highest at intermediate levels of deer density, conforming also to the intermediate disturbance hypothesis. Our results suggest that herbivory can be the most important driver of meta‐community structure in mesic systems; this contrasts with the results of earlier studies conducted in harsh environments, where species sorting by abiotic factors at early life stages reduced the role of biotic interactions, including herbivory.
Toll‐Like Receptor 4 Expression in Decidual Cells and Interstitial Trophoblasts Across Human Pregnancy
Authors: Schatz Frederic , Kayisli Umit A. , Vatandaslar Emre , Ocak Nehir , Guller Seth , Abrahams Vikki M. , Krikun Graciela , Lockwood Charles J.
Published: May 2012

Problem

Toll‐like receptor‐4 (TLR‐4) protects against Gram‐negative bacteria expressed lipopolysaccharide and ‘danger signals’ from injured or dying cells. Although decidual cells (DCs) and interstitial trophoblasts (ITs) are in close contact, TLR‐4 has been studied extensively only in ITs.

Method of study

Formalin‐fixed, paraffin‐embedded serial sections of endometrium in follicular and luteal phases and deciduas from first and second trimester elective terminations and third trimester normal deliveries were immunostained for TLR‐4, trophoblast‐specific cytokeratin, and DC‐specific vimentin. HSCORE assessed TLR‐4 immunostaining in DCs versus ITs.

Results

TLR‐4 HSCORES were significantly higher in: (i) first trimester DCs than luteal phase pre‐decidual stromal cells; (ii) first and third versus second trimester DCs, but similar between third trimester deciduas parietalis and basalis; (iii) first versus second trimester ITs; (iv) DCs versus ITs across gestation.

Conclusion

Higher TLR‐4 in DCs than ITs suggests DCs as primary targets for Gram‐negative bacteria and/or inflammation‐related danger signals.
Noradrenaline use for septic shock in children: doses, routes of administration and complications
Authors: Lampin ME , Rousseaux J , Botte A , Sadik A , Cremer R , Leclerc F
Published: May 2012

Aim:  To report our 10 year experience with noradrenaline use in children with septic shock focusing on doses, routes of administration and complications.

Methods:  Retrospective single‐centre review of children with septic shock who received noradrenaline between 2000 and 2010.

Results:  We identified 144 children with septic shock treated with noradrenaline, in 22% as the first‐line drug. The median volume resuscitation before vasoactive agent administration was 50 mL/kg interquartile range [IQR: 30–70]. Mean doses of noradrenaline ranged from 0.5 ± 0.4 μg/kg per min (starting dose) to 2.5 ± 2.2 μg/kg per min (maximum dose). Noradrenaline was administered via peripheral venous access or intra‐osseous route in 19% of cases for a median duration of 3 h [IQR: 2–4] without any adverse effects. The use of noradrenaline increased over the study period. Mortality rate was 45% with a significant decrease over the study period. Adverse effects included arrhythmia in two children and hypertension in eight children. None of these arrhythmias required treatment and hypertension resolved with the noradrenaline dose reduction.

Conclusion:  Higher doses of noradrenaline than those suggested in the literature may be necessary to reverse hypotension and hypoperfusion. The use of noradrenaline through peripheral venous access or intra‐osseous route was safe, without any adverse effects.
Therapeutic choices, and the nurse practitioner's role, in type 2 diabetes when metformin alone is no longer enough
Authors: Tierney Kathryn
Published: May 2012

Abstract Purpose:This article provides an overview of the currently available treatments for type 2 diabetes (T2D), outlining the most up to date information to assist nurse practitioners (NPs) to make informed prescribing decisions for T2D therapy once patients are no longer able to maintain blood glucose control using lifestyle modification and/or metformin therapy.

Data sources:Published guidelines for the management of T2D, review articles, primary manuscripts, and FDA prescribing information documents.

Conclusions:In the past, options for the treatment of T2D were limited. However, there is now an ever increasing number of available therapeutic choices for T2D, that, as well as glycemic control, offer significant additional benefits, particularly in terms of reducing hypoglycemic risk and weight gain. Consequently, these newer agents provide both patients and NPs with a much greater choice for ongoing therapy.

Implications for practice:The differing benefits and risk profiles shown by the currently available antidiabetic treatments provide NPs with a unique opportunity to tailor treatment plans more closely to the requirements of each patient. This approach can ensure that the right drug reaches the right patient, which should in turn promote greater treatment compliance and improved outcomes, ultimately slowing disease progression.
TRAITS AND STATES: INTEGRATING PERSONALITY AND AFFECT INTO A MODEL OF CRIMINAL DECISION MAKING*
Authors: VAN GELDER JEAN‐LOUIS , DE VRIES REINOUT E.
Published: May 2012

We propose and test a model of criminal decision making that integrates the individual differences perspective with research and theorizing on proximal factors. The individual differences perspective is operationalized using the recent HEXACO personality structure. This structure incorporates the main personality traits, but it carries the advantage of also incorporating Self‐Control within its personality sphere, and an additional trait termed Honesty‐Humility. Furthermore, the model offers a new perspective on proximal predictors, “states,” of criminal decisions by adding affect (i.e., feelings) to the rational choice–crime equation. The proposed model is tested using scenario data from a representative sample of the Dutch population in terms of gender, age, education level, and province (N = 495). As predicted by the model, personality was both directly and indirectly related to criminal decision making. Specifically, the traits Emotionality, Self‐Control, and Honesty‐Humility were mediated by both affect and rational choice variables. Conscientiousness operated only indirectly on criminal decision making via rational choice. Together, the findings support a trait‐state model of criminal decision making.
Mandaeism in Antiquity and the Antiquity of Mandaeism
Authors: Häberl Charles G.
Published: May 2012

The evidence for a history of Mandaeism during the period of Late Antiquity (3rd–8th c. CE) and its evolution as a religious tradition prior to and immediately following the advent of Islam is surveyed. This evidence includes the Mandaean manuscript tradition, the testimony of outside witnesses, and the corpus of incantation texts from Late Antique Mesopotamia. It is noted that the study of this evidence has typically been subsumed under the study of related traditions, and that it could benefit from a reassessment. The issues addressed include Mandaeism’s relationship to other religions, such as Judaism, Zoroastrianism, Christianity, and Manichaeism, the antiquity and authenticity of its traditions, and the extent of Islamic influence upon them.
Prescribing the Families Own Dysfunctional Rules as a Therapeutic Strategy*
Authors: Andolfi Maurizio
Published: May 2012

The use of paradox‐strategy in therapy is motivated by the fact that many families request help but at the same time seem to reject all offers of help. The therapist may be drawn into a game in which every effort on his part to act as an agent of change is nullified by the family group. In systemic terms these contradictory attitudes derive from the dynamic equilibrium existing between the tendency toward change, which is implicit in the request for help at one level, and the tendency toward homeostasis which at another level imposes the repetition of the family's habitual rules of interaction. The coexistence of these forces can entangle the therapist in the family's paradoxical logic of “help me to change, but without changing anything.”

By accepting the contradiction facing him and by “uniting” himself with this within the family, the therapist puts himself into a position opposite to that which the family expects. His response to the family's paradoxical request is a paradox, or counterparadox, because it creates the contradictory communication typical of rigid family systems. By prescribing its own dysfunctional rules to the family, the therapist can stimulate the tendencies toward change present in the family system.
Why Are So Many (If Not Really All) People and Families Disturbed?*
Authors: Charny Israel W.
Published: May 2012

Many personal and family problems grow out of our not knowing how to process an intricate network of dualities, contradictions, dilemmas, paradoxes, and momentums that are intrinsic to the human condition rather than resulting from “disturbance” or pathology. What we have been learning in family therapy is that the processing of both “right” and “wrong” ways, or “good” and “bad” behaviors, is more likely to yield health and growth, whereas failures to process these dualities are far more the culprit of emotional disorders than bad or wrong behaviors as such. What really becomes important in family life is not the ability to stay out of trouble, but to get out of trouble, that is the ability to process conflicts and dilemmas and unfairness constructively. This way of looking at families helps us to account for and integrate many of the hard empirical findings that have been gathering now for twenty years in family therapy.
Family Versus Individual Therapy: Impact On Discrepancies Between Parents’ And Adolescents’ Perceptions Over Time
Authors: Guo Xiamei , Slesnick Natasha
Published: May 2012

This study examined the degree of disagreement between runaway adolescents and their primary caretakers, defined as informant discrepancies, on their view of their family. How these discrepancies changed over time and whether family therapy or individual therapy could impact that change were also explored. The current sample (N = 179 dyads) included adolescent substance abusers residing in a runaway shelter and their primary caretakers. Adolescent gender was examined as a correlate of change, and treatment attendance was controlled. The intraclass correlation coefficient was used to measure discrepancies between the individuals within a dyad. Results showed that among those receiving family therapy, but not individual therapy, informant discrepancies decreased significantly over time. Additionally, dyads with a male adolescent showed a significantly slower rate of improvement in discrepancy scores across time compared with dyads with a female adolescent. Previous research indicates that lower levels of discrepant perceptions are associated with better individual and relationship functioning. Therefore, this study’s findings support family therapy as superior to individual therapy for addressing parent–child discrepancies––possibly through its focus on improving family communication, perspective taking, and understanding.
Classroom Discourse in Foreign Language Classrooms: A Review of the Literature
Authors: Thoms Joshua J.
Published: May 2012

This article reviews studies that have investigated discourse in foreign language (FL) classroom contexts from the perspective of sociocultural theory. Sociocultural theory maintains that language learning and development in a classroom context are intimately tied to the discursive practices by which and through which learners interact with each other and their teacher. Furthermore, the research has shown that teachers play an important role in that the specific types of patterns created in their interactions with students are a fundamental source of learners’ competence in the FL. This review raises additional questions that remain to be addressed in future research that will potentially contribute to an evolving understanding of classroom discourse.
Beyond the Language‐Content Divide: Research on Advanced Foreign Language Instruction at the Postsecondary Level
Authors: Paesani Kate , Allen Heather Willis
Published: May 2012

This review examines research on advanced‐level foreign language (FL) teaching and learning in collegiate contexts with a particular focus on the merging of language and literary‐cultural content. The overarching question framing this review is: What is the relationship between language, literature, and culture, and how are they instantiated through FL curricula and instruction at the advanced level? To respond to this question, language and literary‐cultural content in advanced FL contexts are addressed from the perspective of three trends evidenced in published research: (1) conceptualizations of literature and culture within the advanced‐level curriculum, (2) integration of language and literary‐cultural content at the course level, and (3) incorporation of advanced language and content at the curricular level. The review concludes by identifying overarching themes and directions for future research.
A Review of High‐Leverage Teaching Practices: Making Connections Between Mathematics and Foreign Languages
Authors: Hlas Anne Cummings , Hlas Christopher S.
Published: May 2012

Recent discussions in the field of teacher education call for more practice‐based professional development as a way to provide pre‐service teachers with the necessary skills to significantly advance student learning. High‐leverage teaching practices (HLTP) are a core set of teaching practices that, when executed proficiently by accomplished novice teachers, are said to promote higher gains in student learning over other teaching practices. In this review, we define and identify possible practices within specific teaching domains against the backdrop of the history of HLTP in the field of mathematics education, a pioneer in this area. We then extend and apply the work in mathematics to foreign language (FL) education. Examining HLTP from the perspective of mathematics education provides a useful initial framework to the FL education community to identify and establish its own set of practices and ground future research in this area.
Learner Attitudes, Perceptions, and Beliefs in Language Learning
Authors: Wesely Pamela M.
Published: May 2012

This literature review examines recent research in the area of learner attitudes, perceptions, and beliefs about language learning and about themselves as language learners, together with the consequences of these perceptions on learning outcomes. After an overview of relevant definitions of these complex concepts, the review categorizes this research into three orientations: studies that have focused on how learner attitudes, perceptions, and beliefs relate to their traits and characteristics; studies that have examined how these notions relate to the learning environment; and studies that have looked at how these notions play out in the interaction between the learner and the environment. The review concludes with suggestions related to research design and research questions that would address current lacunae in the field.
Standards for Foreign Language Learning: Defining the Constructs and Researching Learner Outcomes
Authors: Troyan Francis J.
Published: May 2012

In an effort to articulate an agenda for learner outcomes research linked to the Standards for Foreign Language Learning in the 21st Century, this review examines the profession's current conceptualization of the National Standards in research on learner outcomes across various levels of instruction. The research literature reviewed reveals that, to date, empirical studies of learner outcomes have been conducted only on the Communication goal of the National Standards. Consequently, in the majority of the studies reviewed in the other goal areas have not conceptualized learner outcomes from a National Standards perspective, nor have they defined outcomes in the ways they are presented in the National Standards. Recommendations for future research are provided, which include the creation of design‐based research communities and partnerships in K–16 foreign language education. A primary goal for this research agenda is to expand the scope of the current research by (1) exploring the National Standards that have yet to be investigated in the research, (2) designing and investigating innovations related to those National Standards, and ultimately (3) deepening the understanding of learner processes, development, and outcomes related to the National Standards.
Experimental Study of Effects of Grooved Tip Clearances on the Flow Field in a Compressor Cascade Passage
Authors: Ma Hongwei , Zhang Jun , Zhang Jinghui , Yuan Zhou
Published: May 2012

This paper presents an experimental investigation of effects of grooved tip clearances on the flow field of a compressor cascade. The tests were performed in a low-speed large-scale cascade, respectively, with two tip-clearance configurations, including the flat tip and the grooved tip with a chordwise channel on the blade top. The flow field at 10% chord downstream from the cascade trailing edge was measured at four incidence angles using a mini five-hole pressure probe. The static pressure distribution was measured on the tip endwall. The results show that the pressure gradient from the pressure side to the suction side on the blade tip is reduced due to the existence of the channel. As a result, the leakage flow is weakened. The high-blockage and high-loss region caused by the leakage flow is narrower with the grooved tip. In the meantime, the leakage flow migrates to lower span-wise position. The combined result is that the flow capacity in the tip region is improved at the incidence angles of 0 deg and 5 deg with the grooved tip. However, the loss is slightly greater than that with the flat tip at all the incidence angles.
Persistence Filters for Estimation: Applications to Control in Shared-Sensing Reversible Transducer Systems
Authors: Sukumar Srikant , Akella Maruthi R.
Published: May 2012

We investigate state observer and feedback control design for systems with state- and time-dependent control or measurement gains. In this framework, we look at reversible transducers that are continually switched between the actuation and sensing modes at some prespecified schedule. Design and analysis of stable state-observers and feedback controllers for these classes of switched/hybrid systems are significantly complicated by the fact that, at any given instant of time, the overall system loses either controllability (during the sensing phase) or observability (during the actuation phase). In this work, we consider systems with scalar time-varying measurement gains and provide a novel observer construction that guarantees exponential reconstruction of state estimates to their true values. We go a step further to derive an exponentially stabilizing controller design that uses the state estimates resulting from our observer. This amounts to the establishment of a rather remarkable separation property of the control design. These developments hinge on a rather mild technical assumption, which can be interpreted for the reversible transducer problem as a persistent dwell time for both the sensing and actuation modes. An important feature here is that the convergence rate can be specified to any arbitrary value. Our theoretical results are validated through numerical simulations of challenging test-cases that include open-loop unstable systems. The paper also illustrates potential for nonlinear extensions of the observer based control design by considering an interesting special case.
Experimental Study of Nucleate Boiling Heat Transfer Using Enhanced Space-Confined Structures
Authors: Ma Xuehu , Yu Chunjian , Lan Zhong , Wang Donghui , Bai Tao
Published: May 2012

For narrow space boiling, it is difficult to release bubbles from the narrow space, especially on a large-area surface. To solve this problem, a new structure is designed in the present paper. An experimental study of pool boiling on the novel copper enhanced structure, with the separate ordinary confined spaces and the open channels between them, was conducted with water and ethanol. High-speed visualizations are performed to elucidate the bubble flow. The results show that the boiling performance of both water and ethanol can be enhanced effectively. The visualizations indicated that most active nucleation sites emerged in the confined channels and rarely appeared at the bare surfaces not covered by enhanced structures even at high superheat. The bubble diameter, the bubble departure frequency, and the numbers of nucleation sites are obtained using statistical methods. The results suggest that the magnitudes of bubble diameter of water are almost the same on the smooth and enhanced surfaces. The amount of nucleation sites on the enhanced surfaces is remarkably increased, indicating its key role in the boiling enhancement of water. The bubble departure frequency is increased on one of the enhanced surfaces while not increased on another, showing that it is also a significant factor for heat transfer enhancement under certain conditions. While for ethanol, all the three parameters are increased on the enhanced surfaces.
A New Approximation Algorithm of Fractional Order System Models Based Optimization
Authors: Meng Li , Xue Dingyu
Published: May 2012

This paper proposes a new approximation scheme which is an extension to the well-established Charef’s approximation method for fractional order systems. The method relaxes the constraints on the locations of the pole-zero pairs of the approximate system, which provides more flexibility and space for approximate system to approach the original system as close as possible. The approximate system based on an optimization process performs not only a good magnitude fitting but also a good phase fitting. The benefits from using the proposed scheme are illustrated by numerical examples in frequency domains.
Novel Experimental Power Curve Determination and Computational Methods for the Performance Analysis of Vertical Axis Wind Turbines
Authors: Edwards Jonathan M. , Angelo Danao Louis , Howell Robert J.
Published: May 2012

Through novel experimental and computational methods, this paper details a study into the performance aerodynamics of a small-scale vertical axis wind turbine (VAWT). A novel experimental method is first developed and validated before the results are compared to those of a computational fluid dynamics (CFD) study. The computational study is further validated by comparing the flow field to PIV data. The CFD simulations are then analyzed to explain the aerodynamics in further detail, including a discussion of the effect of the streamwise induction on the local angle of attack on the blade. The University of Sheffield’s three-bladed NACA0022 small-scale VAWT experimental rig is mounted within the University’s Low-Speed Wind Tunnel. Tests at tip speed ratios up to 5 were carried out, where the blade Reynolds number (based on rotational speed) ranged from 37,500 to 75,000. The same test conditions are simulated using unsteady computational fluid dynamics.
Operation of Gas Turbine Engines in an Environment Contaminated With Volcanic Ash
Authors: Dunn Michael G.
Published: May 2012

Airborne volcanic ash poses a significant threat to the safe operation of gas turbine powered aircraft. Recent volcanic activity in Iceland and other parts of the world have resulted in interruption of air traffic and in the case of the April 2010 eruption of the Eyjafjallajökull volcano in Iceland, the interruption resulted in a significant loss of revenue. Over the past 30 years there have been several events involving commercial aircraft that have suffered significant damage to the propulsion system as a result of ingesting volcanic ash during a flight event, but a relevant engine focused database to provide guidance for dealing with the problem has not been generally available until recently. In Sept. 2010 after the Iceland volcano activity, a body of data that had not been in the public domain was released and those measurements that are described in some detail herein can be helpful to the airlines, the aircraft manufacturers, the engine manufacturers, those responsible for flight operations, and hopefully to the flight crews. The intent of this paper is to describe some of the more notable aircraft/ash cloud events, the available data associated with those encounters and how those data can be used to effectively deal with this problem while maintaining safe flight operations. The paper specifically (a) illustrates the engine damage mechanisms, (b) estimates the potential operational life of a particular class of engines if the ash concentration is at a very low level, and (c) illustrates how this database is helpful in dealing with future interruptions of flight routes caused by volcanic eruptions. A section at the end of this paper provides the comments and concerns of the industry and government stakeholders regarding this general problem area.
Mechanical Behavior of Epoxy-Graphene Platelets Nanocomposites
Authors: Zandiatashbar A. , Picu R. C. , Koratkar N.
Published: May 2012

Various aspects of the mechanical behavior of epoxy-based nanocomposites with graphene platelets (GPL) as additives are discussed in this article. The monotonic loading response indicates that at elevated temperatures, the elastic modulus and the yield stress are significantly improved in the composite as compared to neat epoxy. The activation energy for creep is smaller in neat epoxy, which indicates that the composite creeps less, especially at elevated temperatures and higher stresses. The composites also exhibit larger fracture toughness. When subjected to cyclic loading, fatigue crack growth rate is smaller in the composite relative to neat epoxy. This reduction is important by at least an order of magnitude at all stress intensity factor amplitudes. Optimal property improvements in the monotonic, cyclic, and fracture behaviors are obtained for very low filling fraction of approximately 0.1 wt. %. Similar differences in the mechanical behavior are observed when the composite is probed on the local scale by nanoindentation.
Flexural Behavior of a Layer-to-Layer Orthogonal Interlocked Three-Dimensional Textile Composite
Authors: Zhang D. , Waas A. M. , Pankow M. , Yen C. F. , Ghiorse S.
Published: May 2012

The flexural response of a three-dimensional (3D) layer-to-layer orthogonal interlocked textile composite has been investigated under quasi-static three-point bending. Fiber tow kinking on the compressive side of the flexed specimens has been found to be a strength limiting mechanism for both warp and weft panels. The digital image correlation (DIC) technique has been utilized to map the deformation and identify the matrix microcracking on the tensile side prior to the peak load in the warp direction loaded panels. It has been shown that the geometrical characteristics of textile reinforcement play a key role in the mechanical response of this class of material. A 3D local–global finite element (FE) model that reflects the textile architectures has been proposed to successfully capture the surface strain localizations in the predamage region. To analyze the kink banding event, the fiber tow is modeled as an inelastic degrading homogenized orthotropic solid in a state of plane stress based on Schapery Theory (ST). The predicted peak stress is in agreement with the tow kinking stress obtained from the 3D FE model.
Energy Loss in Carbon Nanotube Beam Oscillators due to Anelastic Relaxation
Authors: Zhou Zhong , Vasudevan Vijay K. , Qian Dong
Published: May 2012

We present a semi-analytical approach to study the energy dissipation in carbon nanotube (CNT) beam oscillators under gigahertz excitation. The energy dissipation properties are quantified by the quality factor (Q factor) and associated anelastic properties. Our study reveals that the Q factor is related to the tube radius through an inverse relation for both single walled CNTs (SWCNTs) and multiwalled CNTs (MWCNTs) beam oscillators. At frequency close to the resonance range, significant energy dissipation is observed due to the activation of phonon modes that serve as a major mechanism for energy dissipation in SWCNTs. For MWCNTs, a registration dependent potential (RDP) is introduced to study the effect of intertube registration. Interlayer friction arising from the π bond overlap is shown to contribute significantly to the additional energy dissipation. Based on the extensive simulation studies, an analytical formula for estimating the Q factors of MWCNTs is proposed. Validation of the analytical prediction with the available experimental data yields a good agreement and quantifies the roles of different factors contributing to the energy dissipation through anelastic relaxation.
Stress Analysis and Structural Optimization of a Three-Layer Composite Cladding Tube Under Thermo-Mechanical Loads
Authors: Zhou S.-S. , Gao X.-L. , Griffith G. W.
Published: May 2012

A general solution for the stress and strain fields in a three-layer composite tube subjected to internal and external pressures and temperature changes is first derived using thermo-elasticity. The material in each layer is treated as orthotropic, and the composite tube is regarded to be in a generalized plane strain state. A three-layer ZRY4-SiCf/SiC-SiC composite cladding tube under a combined pressure and thermal loading is then analyzed and optimized by applying the general solution. The effects of temperature changes, applied pressures, and layer thickness on the mechanical behavior of the tube are quantitatively studied. The von Mises’ failure criterion for isotropic materials and the Tsai-Wu’s failure theory for composites are used, respectively, to predict the failure behavior of the monolithic ZRY4 (i.e., Zircaloy-4) inner layer and SiC outer layer and the composite SiCf/SiC core layer of the three-layer tube. The numerical results reveal that the maximum radial and circumferential stresses in each layer always occur on the bonding surfaces. By adjusting the thickness of each layer, the effective stress in the three-layer cladding tube under the prescribed thermal-mechanical loading can be changed, thereby making it possible to optimally design the cladding tube.
CAD-Based Calculation of Cutting Force Components in Gear Hobbing
Authors: Nikolaos Tapoglou , Aristomenis Antoniadis
Published: May 2012

Gear hobbing is a common method of manufacturing high precision involute gears. The thorough knowledge of the developed cutting forces and the wear of the cutting tool are of great importance in order to produce helical and spur gears as they influence the cost of the manufacturing process and the quality of the produced gear. A novel simulation code called HOB3D was created in accordance with the above. This code can simulate the complex movements involved in gear hobbing with the best available accuracy, which is achieved by embedding the developed algorithm in a commercial computer aided design (CAD) environment. The simulation code calculates and exports the total cutting forces as well as the cutting forces in every cutting edge involved in the cutting process.
Robust Adaptive Backstepping Control Design for a Supercavitating Vehicle Model
Authors: Mao Xiaofeng , Wang Qian
Published: May 2012

In this paper, robust adaptive backstepping control is applied for a supercavitating vehicle model to account for the unknown slope in the fin force of the vehicle model. In the benchmark supercavitating-vehicle model, which is widely used for control designs in the literature, the fin force was modeled as a linear function with respect to the fin angle of attack, and the slope of the fin force was considered to be a known constant for a fixed cavitation number. However, more realistic modeling for fin force shows that the fin force slope is a function of the fin deflection angle, fin sweepback angle and fin immersion. Additionally, noting that the cavity shape at the transom region determines immersion of the fins, the fin immersion and thus the slope of the fin force will also be impacted by the so-called memory effect due to cavity-vehicle interaction. In this paper, we consider the fin effectiveness parameter relative to the cavitator, which is used to compute the slope of the fin force, to be an unknown parameter. Then we design a parameter estimation law for this fin effectiveness parameter and an adaptive backstepping controller to stabilize the supercavitating vehicle model. We prove the boundedness of all the signals and convergence of vehicle state variables via Lyapunov stability theory. In addition, if the bound of the fin effectiveness parameter is known, a projection of the parameter adaptive law can be used and the resulting controller implementation will maintain the boundedness and convergence properties.
Screw Theory Applied to a Rigid Cylinder Moving on a Plane
Authors: Di´az-Gonza´lez James , Rosario Lourdes
Published: May 2012

In this work a mathematical model of the motion of a cylinder moving on a plane is deduced using screw theory. The linear Coulomb friction equations are applicable for the maximum static and kinetic friction forces. In the case of the rolling motion of a cylinder, the friction forces are not necessarily maxima. This paper describes the dynamic states of motion of a cylindrical part moving in three separate scenarios by the Euler dual equation. The first scenario is when the cylinder is moving on a horizontal static plane due to an external harmonic force proportional to the mass of the part. For this case, the sliding conditions are expressed as a function of the vibration parameters and generalized based on a harmonic dimensionless variable. The second and third scenarios are when the cylinder is moving by translational displacements on a horizontal and inclined plane.
Optimal MIMO PID Controllers for the MIMO Processes
Authors: Li Xian Hong , Yu Hai Bin , Yuan Ming Zhe , Zang Chuan Zhi , Wang Zhuo
Published: May 2012

This paper focuses on the design method of the optimal multiple inputs and multiple outputs (MIMO) proportional integral derivative (PID) controllers for the MIMO processes via using Lyapunov theorems. A hybrid augmented integral squared error (HAISE) is applied to design the optimal multi-loop PID controller for the MIMO plants. The optimal multi-loop PID control problem is transformed into a nonlinear constraint optimization (NLCO) problem. The optimal PID controller parameters are obtained from solving the NLCO problem. The design method is applied to devise the multi-loop optimal PID controller for different types of MIMO plants and the optimal PID controller under different control weight is shown in this paper. The performances of different PID tuning methods are studied too. The computer simulation results are presented to demonstrate the effectiveness of the design method and good performance and robustness of the optimal multi-loop PID controllers.
Optimal Asymptotic Entrainment of Phase-Reduced Oscillators
Authors: Zlotnik Anatoly , Li Jr-Shin
Published: May 2012

We derive optimal periodic controls for entrainment of a self-driven oscillator to a desired frequency. The alternative objectives of minimizing power and maximizing frequency range of entrainment are considered. A state space representation of the oscillator is reduced to a linearized phase model, and the optimal periodic control is computed from the phase response curve using formal averaging and the calculus of variations. Computational methods are used to calculate the periodic orbit and the phase response curve, and a numerical method for approximating the optimal controls is introduced. Our method is applied to asymptotically control the period of spiking neural oscillators modeled using the Hodgkin-Huxley equations. This example illustrates the optimality of entrainment controls derived using phase models when applied to the original state space system.
Output Feedback Control for Continuous-Time Switched Linear Systems Subject to Actuator Saturation
Authors: Duan Chang , Wu Fen
Published: May 2012

This paper is devoted to output feedback ℋ∞ control problem for continuous-time switched linear systems subject to actuator saturation. Using minimal switching rule, nonlinear output feedbacks, expressed in the form of quasi-linear parameter varying system are designed to satisfy a pre-specified disturbance attenuation level defined by the regional ℒ2 gains over a class of energy-bounded disturbances. The synthesis condition is further simplified and can be solved through efficient LMI optimizations. The proposed switched control approach is also illustrated by a simple example.
Dynamics of Cilia-Based Microfluidic Devices
Authors: Kongthon Jiradech , Chung Jae-Hyun , Riley James , Devasia Santosh
Published: May 2012

This article models the dynamics of cilia-based devices (soft cantilever-type, vibrating devices that are excited by external vibrations) for mixing and manipulating liquids in microfluidic applications. The main contribution of this article is to develop a model, which shows that liquid sloshing and the added mass effect play substantial roles in generating large-amplitude motion of the cilia. Additionally, experimental results are presented to show that (i) mixing is substantially improved with the use of cilia when compared to the case without cilia and (ii) mixing with cilia can be further enhanced by using an asymmetric excitation waveform when compared to sinusoidal excitation.
Modelling and Experimental Validation of a Novel Piezohydraulic Servovalve
Authors: Sangiah Dhinesh K. , Plummer Andrew R. , Bowen Christopher R. , Guerrier Paul
Published: May 2012

Servovalves are compact, accurate, fast flow modulating valves. However, cost reduction pressures exist, not least due to the electomagnetically actuated pilot stage. This paper describes a servovalve with a jet deflector pilot stage actuated by a multilayer piezoelectric bimorph. The electrical power and voltage requirements are relatively low (+/−30V), and mechanical spool feedback is used as opposed to the more complex electrical feedback alternative. A mathematical model of the valve is presented, which is used to simulate its performance. Finite element analysis is used to model the bimorph actuator and the feedback wire assembly to verify an Euler-Bernoulli beam analysis. A Moog 26 Series servovalve is used as a basis for the prototype. Experimental test results are in good agreement with the simulation results. The high order nonlinear model is also approximated by a first order transfer function to identify the parameters that dictate the main design tradeoffs.
A System Dynamics Modeling Methodology to Predict Transient Phenomena in Compressible Fluid Flow Systems
Authors: Follen Kenneth , Stockar Stephanie , Canova Marcello , Guezennec Yann , Rizzoni Giorgio
Published: May 2012

The prediction of dynamic phenomena in compressible fluids, such as the air path systems of Internal Combustion Engines (ICEs) has seen an enormous growth in the past years. Striving to improve engine performance, fuel economy and emissions has led to the understanding that significant gains can only be achieved if improvements in engine design can be matched by the ability to closely control engine breathing and combustion performance. The current state of the art in the modeling of ICEs air path systems presents two main approaches, namely the high-fidelity, computationally intensive numerical methods and the low-fidelity, calibration intensive lumped-parameter models. This paper introduces a novel approach for modeling unsteady phenomena in compressible fluids that combines the advantages of numerical methods (high accuracy and low calibration effort) with the limited computation time of lumped-parameter models based on ordinary differential equations (ODEs). The approach is here presented for the one-dimensional nonlinear Euler equations for compressible fluid flow systems, which are particularly relevant for modeling the air path systems of internal combustion engines.
Tuning of an Adaptive Neural Network Compensator for Position Control of a Pneumatic System
Authors: Dehghan Behrad , Taghizadeh Sasan , Surgenor Brian
Published: May 2012

The paper examines the potential of a novel adaptive neural network compensator (ANNC) for the position control of a pneumatic gantry robot. Previousl experimental results were disappointing, with only a 20% improvement in performance when ANNC was employed with a PID controller. The conclusion was that the level of improvement with ANNC did not warrant the extra effort required for implementation. However, when the tests were repeated after the system had been reconfigured, improvements on the order of 45% to 70% were achieved. This paper presents a tuning procedure for ANNC, confirms the adaptive nature and provides results that support the conclusion that ANNC can indeed provide a significant improvement in tracking performance.
Precision Position Tracking of MR-Compatible Pneumatic Piston-Cylinder Using Sliding Mode Control
Authors: Comber David , Barth Eric J.
Published: May 2012

This paper presents the nonlinear dynamics and sliding mode control design for a 1-DOF needle insertion robot. The robot actuator is an MR-compatible pneumatic piston-cylinder. A brief review of the dynamics for this type of actuator is provided. The reaction force of tissue on the needle remains an unknown for which our controller compensates. A sliding mode control law is formulated that relies solely on position and pressure measurements (no force sensor). Experimental implementation of the actuator and controller is described. The mean and maximum steady-state position errors for step reference positions were 0.018 mm and 0.028 mm, respectively.
Buoyant Fluorescent Particles as a Novel Sensing Technology for Field Observations of Water Flows
Authors: Tauro Flavia , Aureli Matteo , Porfiri Maurizio , Grimaldi Salvatore
Published: May 2012

In this paper, we investigate the feasibility of off-the-shelf buoyant fluorescent microspheres as particle tracers in turbid water flows. Microspheres’ fluorescence intensity is experimentally measured and detected in static aqueous suspensions of increasing concentrations of clay to simulate typical conditions of natural drainage networks. We conduct experiments by using photoconductive cells and image-based sensing methods. Results obtained with both approaches exhibit comparable trends and show that the considered particles are detectable in critically turbid water flows. Further information on the performance and integration of such microspheres in low-cost measurement instrumentations for field observations is obtained through experiments on a custom built water channel. Findings from this study show that the proposed technology may serve as a minimally invasive sensing system for hazardous events, such as pollutant diffusion in natural streams and flash flooding due to extreme rainfall.
Model-Based Control via Balanced Realization for Automotive Cold Start Hydrocarbon Reduction
Authors: Asami Satoshi , Cranmer Adam , Shahbakhti Mahdi , Hedrick J. Karl
Published: May 2012

High automotive hydrocarbon emission during cold start is a well recognized challenge with increasing importance in moving towards green vehicles. In this work the application of a linear model reduction technique on the design of a controller for a nonlinear system is discussed. A reduced order cold start model of an SI engine and aftertreatment system is realized using a balanced truncation technique. Sliding mode controllers, derived from a nonlinear physical model and the reduced order model, are designed to reduce tailpipe hydrocarbon emissions. The comparison results indicate the controller derived from the balanced truncated model performs better since it adjusts the control inputs such that it favors the certain desired trajectories which are more influential on the final control target.
Casimir Effect Influence on NEMS Cantilever Resonators
Authors: Caruntu Dumitru I. , Knecht Martin , Zapata Roberto J.
Published: May 2012

This paper investigates electrostatically actuated nanoelectromechanical (NEMS), to include Casimir effect, resonator response near natural frequency. Both electrostatic force and Casimir force are nonlinear. The method of multiple scales is used in a direct approach of the problem in the case of small actuation, damping, and Casimir effect. Two approximation problems resulting from the direct approach are solved. The phase-amplitude relationship is obtained. Numerical results for uniform NEMS cantilever resonators for possible sensing applications are provided.