bluuebunny/crossref_metadata_2025 huggingface dataset:
Intrauterine insulin resistance in fetuses of overweight mothers
Authors: Liu Bin , Xu Yun , Liang Jian‐ming , Voss Courtney , Xiao Huan‐yu , Sheng Wei‐yang , Sun Yan‐hong , Wang Zi‐lian
Published: June 2012

Aim:  To investigate the relationship between maternal overweight and fetal insulin resistance.

Material and Methods:  Nineteen overweight and 30 lean pregnant women were recruited in the present study. Maternal and fetal insulin resistance were determined by measuring sex hormone binding globulin (SHBG) concentrations in maternal venous or umbilical cord serum, respectively. Maternal age, gestational age, height, pre‐gravidity weight, pre‐partum weight, as well as fetal gender, birth weight, birth height, and head circumference were collected as clinical data.

Results:  Fetuses of overweight mothers had larger birth weight (3.58 ± 0.55 kg vs 3.32 ± 0.42, adjusted P = 0.006) and lower SHBG concentrations (26.64 ± 3.65 vs 34.36 ± 7.84, adjusted P = 0.007) than those of lean mothers after values were adjusted for potential cofactors. Fetal SHBG level was negatively correlated with pre‐gravidity body mass index (R = −0.392, adjusted P = 0.025) and weight gain during pregnancy (R = −0.332, adjusted P = 0.026) even with adjustment for potential cofactors. Among the 29 pregnant women with gestational diabetes mellitus, the overweight mothers had higher H1AC levels than their lean counterparts (6.47 ± 0.44 vs 5.74 ± 0.52, adjusted P = 0.004).

Conclusion:  Intrauterine insulin resistance is more prominent in fetuses of overweight mothers, an effect that is decreased by weight gain control during pregnancy.
Interparental Conflict in Kindergarten and Adolescent Adjustment: Prospective Investigation of Emotional Security as an Explanatory Mechanism
Authors: Cummings E. Mark , George Melissa R. W. , McCoy Kathleen P. , Davies Patrick T.
Published: June 2012

Advancing the long‐term prospective study of explanations for the effects of marital conflict on children’s functioning, relations were examined between interparental conflict in kindergarten, children’s emotional insecurity in the early school years, and subsequent adolescent internalizing and externalizing problems. Based on a community sample of 235 mothers, fathers, and children (Ms = 6.00, 8.02, 12.62 years), and multimethod and multireporter assessments, structural equation model tests provided support for emotional insecurity in early childhood as an intervening process related to adolescent internalizing and externalizing problems, even with stringent autoregressive controls over prior levels of functioning for both mediating and outcome variables. Discussion considers implications for understanding pathways between interparental conflict, emotional insecurity, and adjustment in childhood and adolescence.
LOCAL MODELS—THE KEY TO BOOSTING STABLE LEARNERS SUCCESSFULLY
Authors: Ting Kai Ming , Zhu Lian , Wells Jonathan R.
Published: June 2012

Boosting has been shown to improve the predictive performance of unstable learners such as decision trees, but not of stable learners like Support Vector Machines (SVM), k‐nearest neighbors and Naive Bayes classifiers. In addition to the model stability problem, the high time complexity of some stable learners such as SVM prohibits them from generating multiple models to form an ensemble for large data sets. This paper introduces a simple method that not only enables Boosting to improve the predictive performance of stable learners, but also significantly reduces the computational time to generate an ensemble of stable learners such as SVM for large data sets that would otherwise be infeasible. The method proposes to build local models, instead of global models; and it is the first method, to the best of our knowledge, to solve the two problems in Boosting stable learners at the same time. We implement the method by using a decision tree to define local regions and build a local model for each local region. We show that this implementation of the proposed method enables successful Boosting of three types of stable learners: SVM, k‐nearest neighbors and Naive Bayes classifiers.
Acute Hospital Use, Nursing Home Placement, and Mortality in a Frail Community‐Dwelling Cohort Managed with Primary Integrated Interdisciplinary Elder Care at Home
Authors: Rosenberg Ted
Published: June 2012

Objectives

To evaluate the effect of medical Primary Integrated Interdisciplinary Elder Care at Home (PIECH) on acute hospital use and mortality in a frail elderly population.

Design

Comparison of acute hospital care use for the year before entering the practice (pre‐entry) with the most‐recent 12‐month period (May 1, 2010–April 30, 2011, postentry) for active and discharged patients.

Setting

Community.

Participants

All 248 frail elderly adults enrolled in the practice for at least 12 months who were living in the community and not in nursing homes in Victoria, British Columbia.

Intervention

Primary geriatric care provided by a physician, nurse, and physiotherapist in participants' homes.

Measurements

Acute hospital admissions, emergency department (ED) contacts that did not lead to admission, reason for leaving practice, and site of death.

Results

There was a 39.7% (116 vs 70; P = .004) reduction in hospital admissions, 37.6% (1,700 vs 1,061; P = .04) reduction in hospital days, and 20% (120 vs 95; P = .20) reduction in ED contacts after entering the practice. Fifty participants were discharged from the practice, 64% (n = 32) of whom died, 20% (n = 10) moved, and 16% (n = 8) were admitted to nursing homes. Fifteen (46.9%) deaths occurred at home.

Conclusion

Primary Integrated Interdisciplinary Elder Care at Home may reduce acute hospital admissions and facilitate home deaths.
Atrial Fibrillation: An Independent Risk Factor for Nonaccidental Falls in Older Patients
Authors: SANDERS NATALIE A. , GANGULY JOYA A. , JETTER TAWNI L. , DACCARETT MARCOS , WASMUND STEPHEN L. , BRIGNOLE MICHELINO , HAMDAN MOHAMED H.
Published: June 2012

Background: Nonaccidental falls are often the result of a combination of factors including cardiovascular disorders such as orthostatic hypotension and unspecified cardiac arrhythmias. The objective of this study was to determine if there is an association between atrial fibrillation (AF) and nonaccidental falls.

Methods: We reviewed the records of 442 consecutive patients >65 years old who presented to the Emergency Department at the University of Utah Medical Center with a complaint of fall.

Results: Two‐hundred eleven patients presented with nonaccidental fall, 231 patients with accidental fall. Patients with nonaccidental fall were more likely to be older, have a history of hypertension and neurological disorders, and taking five or more medications when compared to patients with accidental fall. Despite a similar prevalence of sinus rhythm at presentation, the prevalence of a history of AF was significantly higher in patients with nonaccidental fall compared to patients with accidental fall (26% vs 15%; P = 0.003). After adjusting for clinically and statistically significant predictors with a multivariate logistic regression analysis, AF, neurological disorders, and age ≤81 years were independent predictors of nonaccidental fall. In patients ≤81 years old (median age), the risk of nonaccidental falls was 2.5 times greater in patients with a history of AF when compared to those without a history of AF (odds ratio = 2.53 [confidence interval 95% 1.3–5], P = 0.007).

Conclusion: AF is an independent risk factor for nonaccidental falls. Our results emphasize the need to screen for AF in patients presenting with nonaccidental fall.

(PACE 2012; 35:973–979)
Kinetic Analysis of Densification Behavior of Nano‐sized Tungsten Powder
Authors: Wang Hongtao , Zak Fang Zhigang
Published: June 2012

The densification behavior of nano‐sized tungsten powder is examined using both nonisothermal and isothermal methods, and the kinetics of densification is evaluated using conventional sintering theories. The results show that nano‐sized powder, similar to micrometer‐sized powder, experiences three stages of sintering: initial, intermediate, and final. The initial densification of nano‐sized powder increased linearly with increasing time. The rate of densification accelerated after the compact reached above 50% relative density. The initial densification (when relative density <50%) was found to be the result of particle coarsening induced particle rearrangement. The apparent linear initial densification behavior is postulated to be due to the linear kinetic behavior of coarsening. Furthermore, surface diffusion can contribute to the initial densification of nano‐sized powder indirectly by being the primary mass transport mechanisms of the coarsening at the beginning of the sintering. The intermediate and final stages of nano sintering have similar densification behavior to those of micrometer‐sized powders, during which grain‐boundary diffusion is the main mechanism of densification.
The first recombinant human coagulation factor VIII of human origin: human cell line and manufacturing characteristics
Authors: Casademunt Elisabeth , Martinelle Kristina , Jernberg Mats , Winge Stefan , Tiemeyer Maya , Biesert Lothar , Knaub Sigurd , Walter Olaf , Schröder Carola
Published: June 2012

Introduction

Since the early 1990s, recombinant human clotting factor VIII (rhFVIII) produced in hamster cells has been available for haemophilia A treatment. However, the post‐translational modifications of these proteins are not identical to those of native human FVIII, which may lead to immunogenic reactions and the development of inhibitors against rhFVIII. For the first time, rhFVIII produced in a human host cell line is available.

Aim

We describe here the establishment of the first human production cell line for rhFVIII and the manufacturing process of this novel product.

Methods and results

A human cell line expressing rhFVIII was derived from human embryonic kidney (HEK) 293 F cells transfected with an FVIII expression plasmid. No virus or virus‐like particles could be detected following extensive testing. The stringently controlled production process is completely free from added materials of animal or human origin. Multistep purification employing a combination of filtration and chromatography steps ensures the efficient removal of impurities. Solvent/detergent treatment and a 20 nm pore size nanofiltration step, used for the first time in rhFVIII manufacturing, efficiently eliminate any hypothetically present viruses. In contrast to hamster cell‐derived products, this rhFVIII product does not contain hamster‐like epitopes, which might be expected to be immunogenic.

Conclusions

HEK 293 F cells, whose parental cell line HEK 293 has been used by researchers for decades, are a suitable production cell line for rhFVIII and will help avoid immunogenic epitopes. A modern manufacturing process has been developed to ensure the highest level of purity and pathogen safety.
Adélie penguins and temperature changes in Antarctica: a long‐term view
Authors: MILLAR Craig D. , SUBRAMANIAN Sankar , HEUPINK Tim H. , SWAMINATHAN Siva , BARONI Carlo , LAMBERT David M.
Published: June 2012

During the summer months, Adélie penguins represent the dominant biomass of terrestrial Antarctica. Literally millions of individuals nest in ice‐free areas around the coast of the continent. Hence, these modern populations of Adélie penguins have often been championed as an ideal biological indicator of ecological and environmental changes that we currently face. In addition, Adélie penguins show an extraordinary record of sub‐fossil remains, dating back to the late Pleistocene. At this time, temperatures were much lower than now. Hence, this species offers unique long‐term information, at both the genomic and ecological levels, about how a species has responded to climate change over more than 40 000 years.
Quality indicators: a tool for quality monitoring and improvement
Authors: Vuk T.
Published: June 2012

Quality indicators are one of the quality management system (QMS) tools to monitor and control efficiency of the system key segments, while the results collected serve as a basis for implementation of corrective measures and continuous quality improvement. There are several classifications of quality indicators. According to the objectives of their establishment and utilization, they can be internal and external. In line with the tripartite quality model, quality indicators can be classified as structural indicators, process indicators and outcome indicators. Quality indicators should ideally possess a number of attributes. Besides objectivity (measurability), the most common requirements are as follows: importance and potential for use, reliability and validity. Quality indicators offer the possibility of fast and simple insight into the level of product and service quality and their pattern over time to the interested parties within and outside the institution. Although quality management has long been recognized as being of utmost importance in transfusion medicine, quality indicators as a QMS tool did not receive due attention until recently. Implementation of quality indicators is a complex process which requires scientific approach as well as testing and verification before routine usage. Quality indicators are defined on the basis of scientific concepts, own experiences, results of literature searches, discussion with experts within and outside the institution, etc. On setting quality indicators, the numerator and denominator should first be strictly defined. Quality indicators should be monitored continuously, including trend monitoring and detection of deviations. Whenever considered necessary, appropriate corrective measures have to be undertaken.
Effect of halogen light irradiation on hydrogen peroxide bleaching: an in vitro study
Authors: Liang S , Sa Y , Sun L , Ma X , Wang Z , Xing W , Jiang T , Wang Y
Published: June 2012

Background:  The aim of this study was to evaluate the effect of halogen light irradiation on hydrogen peroxide (HP) bleaching by assessing HP concentrations, tooth whitening efficacy, and temperature variations in bleaching agents and pulp chambers.

Methods:  Sixteen premolars were randomly divided into two groups: Group BL (bleaching agent with halogen light irradiation for 3 × 10 minutes) and Group B (bleaching agent alone). HP concentrations were tested before and after treatment. CIE L*a*b* values of specimens were obtained using a spectrophotometer. Temperatures of bleaching gels and pulpal chambers were recorded by a digital multimeter with K‐type thermocouple. Data were analysed using ANOVA and paired t‐test.

Results:  After treatment, HP concentration in group BL was slightly higher than that in group B. Paired t‐tests revealed significant differences of ΔE between groups BL and B in all time intervals except at day 35. The temperature rise of bleaching gels and pulpal chambers in group BL was significantly higher than that in group B.

Conclusions:  In‐office bleaching was effective for tooth whitening. The involvement of halogen light was beneficial for the immediate whitening effect but had little impact on the long‐term whitening effect.
Development of a Model
for the Prediction of Wheel and Rail Wear in the Railway
Field
Authors: Ignesti M. , Marini L. , Meli E. , Rindi A.
Published: June 2012

The wear prediction at the wheel-rail interface is a fundamental problem in the railway field, mainly correlated to the planning of maintenance interventions, vehicle stability, and the possibility of researching strategies for the design of optimal wheel and rail profiles from the wear point of view. The authors in this work present a model specifically developed for the evaluation of the wheel and rail wear and of the wheel and rail profiles evolution. The model layout is made up of two mutually interactive parts: a vehicle model for the dynamical analysis and a model for the wear estimation. The first one is a 3D multibody model of a railway vehicle where the wheel-rail interaction is implemented in a C/C++ user routine. Particularly, the research of the contact points between wheel and rail is based on an innovative algorithm developed by authors in previous works, while normal and tangential forces in the contact patches are calculated according to the Hertz and Kalker’s global theory, respectively. The wear model is mainly based on experimental relationships found in literature between the removed material by wear and the energy dissipated by friction at the contact. It starts from the outputs of the dynamical simulations (position of contact points, contact forces, and global creepages) and calculates the pressures inside the contact patches through a local contact model; then, the material removed by wear is evaluated and the worn profiles of wheel and rail are obtained. In order to reproduce the wear evolution, the overall mileage traveled by the vehicle is divided into discrete steps, within which the wheel and rail profiles are constant; after carrying out the dynamical simulations relative to one step, the profiles are updated by means of the wear model. Therefore, the two models work alternately until completing the whole mileage. Moreover, the different time scales characterizing the wheel and rail wear evolutions require the development of a suitable strategy for the profile update; the strategy proposed by the authors is based both on the total distance traveled by the vehicle and on the total tonnage burden on the track. The entire model has been developed and validated in collaboration with Trenitalia S.p.A. and Rete Ferroviaria Italiana (RFI), which have provided the technical documentation and the experimental results relating to some tests performed with the vehicle DMU Aln 501 Minuetto on the Aosta-Pre Saint Didier line.
Variational Integrators for Dissipative Systems With One Degree of Freedom
Authors: Iura Masashi
Published: June 2012

Variational integrators are developed for dissipative systems with one degree of freedom. The dissipation considered herein is of simple Rayleigh dissipation type. The present formulation is based not on the Lagrange-d’Alembert principle, but on Hamilton’s principle. A benefit for using variational integration techniques is stressed in this paper. The discrete algorithms are obtained by a stationary condition of action integral, in which the Lagrangian is directly discretized. Unlike the existing algorithms, a coupling term between mass and dissipation exists in the present algorithms. A mixed method, in which a velocity is independent on a position coordinate, is presented for dissipative systems. In order to investigate an accuracy of numerical integrators, we introduce a new parameter in addition to the energy decay. Numerical examples show that the present variational, integrators are available for not only highly but also weakly dissipative systems.
Design, Implementation, and Evaluation of Optical Low-Cost Motion Capture System
Authors: Chadda Abhinav , Zhu Wenjuan , Leu Ming C. , Liu Xiaoqing F.
Published: June 2012

This paper describes the design, implementation and evaluation of a low-cost motion capture system with support of interfaces for practically any types of cameras. We present the system’s software architecture design, development of software to implement and integrate several existing algorithms, and effective approaches to address practical issues such as object calibration and synchronizing the real-world and virtual-world coordinate frames. The motion capture system is developed to work with active markers and all the processing is done by the software on a mid-level workstation. With the Firefly MV cameras used, the developed system is capable of working at 60 frames per second, having the ability to simultaneously track the positions and orientations of five objects, with latency averaging about 15 ms, and with an average measurement error of about 0.65 mm between the distance of each pair of four LEDs mounted on a target that is placed 1.5–3.5 m from the cameras.
Time-Varying Initialization and Laplace Transform of the Caputo Derivative: With Order Between Zero and One
Authors: Lorenzo Carl F. , Hartley Tom T.
Published: June 2012

This paper derives the time-varying initialization function for the Caputo derivative with order between zero and one. The derivative is redefined to include this initialization function. Then, the Laplace transform for the redefined Caputo derivative is determined which corrects (supplants) that given for the derivative in the literature and properly accounts for time-varying initialization effects.
A Framework for Self-Realizing Process Models for Additive Manufacturing
Authors: Yim Sungshik , Rosen David W.
Published: June 2012

This research discusses a framework for automating process model realization for additive manufacturing. The models map relationships from design requirements to process variables and can be utilized for future process planning. A repository is employed to collect data and contains previous process plans and corresponding design requirements. The framework organizes data through a statistical clustering method and builds regression models using a multi-layer neural network. Hierarchical and k-means clustering methods are employed in series to manage the data. A two layer neural network and augmented training algorithm are employed to build process models. The framework has been tested with Stereolithography and Selective Laser Sintering process planning problems to demonstrate its usefulness.
Finite Element Modeling of Prestressed Concrete Crossties With Ballast and Subgrade Support
Authors: Yu Hailing , Jeong David , Choros John , Sussmann Ted
Published: June 2012

With the first major installation in North American railroads during the 1960’s, concrete ties were believed to last longer than timber ties and have the potential for reduced life cycle costs. However, their characteristic response to initial pretension release as well as dynamic track loading is not well understood. In North America, concrete ties have been found vulnerable to rail seat deterioration (RSD), but the mechanisms contributing to RSD failures are not well understood. To improve such understanding, a comprehensive computational study of the tie response to dynamic track forces is needed. This paper presents an initial research effort in this direction that models concrete crossties as heterogeneous media in three-dimensional finite element analyses, i.e., the prestressing strands, concrete matrix and the strand-concrete interfaces are represented explicitly. Damaged plasticity models are employed for the concrete material, and linear elastic bond-slip relations, followed by damage initiation and evolution, are adopted for the strand-concrete interfaces. Further, the ballast is modeled with an Extended Drucker-Prager plasticity model, and the subgrade is modeled as an elastic half space. All material parameters are obtained from the open literature. Currently the rail fastening systems are not included in modeling. Two loading scenarios are simulated: pretension release and direct rail seat loading. The modeling approach is able to predict the deformed tie shape, initial interface deterioration, the compressive stress state in concrete and residual tension in the strands upon pretension release. The transfer lengths of the prestressing strands can be readily calculated from the analysis results. Further predicted are the rail seat force-displacement characteristics and the potential failure mode of a concrete crosstie under direct rail seat loading. The responses of two railroad concrete crossties with 8-strand and 24-wire reinforcements, respectively, are studied using the presented modeling framework. The analyses indicate a potential failure mode of tensile cracking at the tie base below the rail seats. The results show that the 24-wire tie is better able to retain the pretension in the reinforcements than the 8-strand tie, resulting in slightly stronger rail seat force-displacement characteristics and higher failure load. The effects of the load application method and the subgrade modeling on the predicted tie response are further studied.
Multiscale Design and Multiobjective Optimization of Orthopaedic Cellular Hip Implants
Authors: Khanoki Sajad Arabnejad , Pasini Damiano
Published: June 2012

A multiscale design and multiobjective optimization procedure is developed to design a new type of graded cellular hip implant. We assume that the prosthesis design domain is occupied by a unit cell representing the building block of the implant. An optimization strategy seeks the best geometric parameters of the unit cell to minimize bone resorption and interface failure, two conflicting objective functions. Using the asymptotic homogenization method, the microstructure of the implant is replaced by a homogeneous medium with an effective constitutive tensor. This tensor is used to construct the stiffness matrix for the finite element modeling (FEM) solver that calculates the value of each objective function at each iteration. As an example, a 2D finite element model of a left implanted femur is developed. The relative density of the lattice material is the variable of the multiobjective optimization, which is solved through the non-dominated sorting genetic algorithm II (NSGA-II). The set of optimum relative density distributions is determined to minimize concurrently interface stress distribution and bone loss mass. The results show that the amount of bone resorption and the maximum value of interface stress can be reduced by over 70% and 50%, respectively, when compared to current fully dense titanium stem.
A Function-Behaviour Oriented Search for Patent Digging
Authors: Russo Davide , Montecchi Tiziano
Published: June 2012

Patents are an important source of technical knowledge which is increasing its fundamental role in supporting design activity. Analogical thinking, for example, is based on a fruitful and previously unnoticed analogy with an existing solution and patent in another area. Patents reveal solutions to technical problems, and they represent an inexhaustible source of information: more than 80 percent of man’s technical knowledge is described in patent literature [1]. Therefore automation of systems for patent retrieval, especially for commercial use, is in great demand. Manual extraction of desired patents is very costly and time consuming. This article proposes an inventive procedure to create a thesaurus, identifying the pool of keywords related to a given product based on a combination of creativity methods and a pre-built thesaurus of physical effects. Keywords are classified into a hierarchical tree diagram according to the FBS Function/Behaviour/Structure classification [2]. This classification, called KOM® - Knowledge Organizing Module [3], can be used for building a state of the art, problem solving activity support, carrying out technological transfer and forecasting activities. In this work, the algorithm for automatic patent digging aimed at building the state of the art of a system or of a technology is presented. Novel and key points are widely illustrated in this paper, together with an explanatory case study.
Explicit Fractional Model Order Estimation Using Unscented and Ensemble Kalman Filters
Authors: Romanovas Michailas , Klingbeil Lasse , Traechtler Martin , Manoli Yiannos
Published: June 2012

The article presents an approach for combining methods of recursive Bayesian estimation with models of dynamical systems with varying differentiation order. The work addresses the problem of explicit fractional order estimation and tracking by constructing an efficient Unscented Kalman filter, where the model order is directly estimated within an augmented state along with the variables of interest. The feasibility of the estimation method is assessed using a benchmark problem based on a simplified fractional neuron firing rate model and time-dependent differentiation order. The proposed technique is compared to an implicit method based on Interacting Multiple Model filtering and a computationally efficient method using a modification of the Ensemble Kalman filter. The performance with respect to different parameters and filter settings is analyzed and a corresponding discussion is provided.
Design Fixation in Physical Modeling: An Investigation on the Role of Sunk Cost
Authors: Viswanathan Vimal , Linsey Julie
Published: June 2012

Physical models are very commonly used as tools for engineering idea generation, yet the guidelines in literature about their implementation are conflicting. A prior study has shown that physical models have the potential to supplement designers’ erroneous mental models; whereas a few observational studies have shown that physical models can cause a high degree of fixation under certain circumstances. At the same time, a previous controlled study fails to show the presence of fixation in idea generation with physical models. This study hypothesizes that prior observed fixation in physical modeling is due to Sunk Cost Effect, which is the reluctance to choose a different path of action once significant money, time or effort is invested in present one. Consistent with the prior study, this study also hypothesizes that physical models supplement designers’ mental models. These hypotheses are investigated through a controlled between-subject experiment. The results show that cost of building plays a vital role in fixation and fixation is not likely inherent in physical representations. Results also show that physical models supplement designers’ mental models and lead them to higher quality ideas.
Analytical Approximation and Experimental Study of Bi-Stable Hybrid Nonlinear Energy Harvesting System
Authors: Karami M. Amin , Varoto Paulo S. , Inman Daniel J.
Published: June 2012

The paper presents modeling, analytical investigation and experimental study of a nonlinear hybrid energy harvesting system in the bi-stable configuration. Linear energy harvesters are frequency sensitive meaning they only generate reasonable power if they are excited accurately at their first natural frequency. Nonlinear effects can be used to increase the effective range of excitations frequency by broadening the frequency response. The proposed hybrid energy harvester uses Piezoelectric and Electromagnetic transduction mechanisms. Electromechanical coupling has been included in the study of the nonlinear dynamics of the harvester. The shooting method has been used to numerically calculate the limit cycles of the bi-stable system. The calculated limit cycles and the Poincare map of the system give the big picture of system vibrations due to the base accelerations. An approximation method is suggested using the method of multiple scales and verified by numerical integrations to find an equivalent forced, damped Duffing oscillator for the original harvesting system. The approximation results the equivalent mechanical system that acts similar to the coupled electromechanical harvester. The approximation is a function of the harvesting circuit so the back coupling is not overlooked. Meanwhile the amount of computations and the complexity of the problem are significantly reduced. The nonlinear vibration of the proposed nonlinear bi-stable harvester is also experimentally investigated. The study shows that the Limit Cycle Oscillations of the nonlinear system increase the power production by two orders of magnitude. The relations between the power output and the excitation level, the excitation frequency, and the electric loads are investigated.
Evaluation of Ring-Type Energy Harvesters
Authors: Hu S. D. , Li H. , Tzou H. S.
Published: June 2012

Piezoelectric materials can be used as electromechanical conversion mechanisms to transfer ambient vibration into electrical energy to power electronic devices. In this study, an elastic ring laminated with a piezoelectric layer on the inner surface is utilized as the basic structure for energy harvesting. The piezoelectric layer is uniformly segmented into several energy harvesting patches for practical applications. The generated electrical energy resulting from modal voltages is analyzed under the open-circuit condition. Two modal energy generations are evaluated: one is the energy induced by the membrane oscillation and the other is the energy induced by the bending oscillation. For practical design applications, energy generations are evaluated with respect to ring radius, piezoelectric layer thickness, ring thickness and segment size. The maximal energy of all harvester patches on the ring is calculated to determine the optimal patch locations with respect to various ring modes. By summing up energies generated from all harvesters on the ring, the overall energy is also evaluated Based on the normalizations and assumptions of parameters, results indicate that the larger the segment size is, the less the energy can be generated.
Integrated Power Control Analysis of DFIG Wind Turbines Considering Structural Flexibility
Authors: Chen Qiong-zhong , Bru¨ls Olivier
Published: June 2012

Doubly-fed induction generators (DFIGs) are commonly used in variable-speed wind turbines for more power extraction. Unlike previous research on DFIG wind turbines, which typically uses an equivalent lumped mass model of the drive train dynamics, but does not include detailed aerodynamic/mechanical representations, this paper investigates on the modelling and control of DFIG wind turbines by following a systematic approach based on a flexible multibody simulation software. The wind turbine structure, generator and control subsystem models are modularly developed for the S4WT package (Samcef for Wind Turbines), which is a user interface for the analysis of wind turbines. An extension of the finite element method is available in the flexible multibody dynamics solver, for the representation of the non-mechanical components, i.e., the generator and the control system, so that the coupled mechatronic system is simulated in a strongly coupled way. This integrated approach is less intricate and more robust than approaches based on an external DLL or co-simulation methods. The objective of this work is to analyze the control-generator-structure interactions in a wind turbine system. The power optimization control is elaborated in detail. A 2MW DFIG wind turbine prototype model is presented for validation. Dynamic analysis including the control effects and the influence of the structural flexibility is provided in an overall range.
Prediction Models for the Estimation of Soil Moisture Content
Authors: Gorthi Swathi , Dou Huifang
Published: June 2012

This paper provides a survey on different kinds of prediction models developed for the estimation of soil moisture content of an area, using empirical information including meteorological and remotely sensed data. The different models employed extend over a wide range of machine learning techniques starting from Basic Linear Regression models through models based on Bayesian framework, Decision tree learning and Recursive partitioning, to the modern non-linear statistical data modeling tools like Artificial Neural Networks. The fundamental mathematical backgrounds, pros and cons, prediction results and efficiencies of all the models are discussed.
A Spatial Spring-Loaded Cable-Loop-Driven Parallel Mechanism
Authors: Liu Hanwei , Gosselin Cle´ment , Laliberte´ Thierry
Published: June 2012

A novel architecture of spatial spring-loaded cable-loop-driven parallel mechanism is introduced in this paper. In this mechanism, cable-spool actuating systems and actuation redundancy are avoided. By attaching springs to the cable loops, three degrees of freedom for spatial displacement can be controlled using only three actuators. This paper presents the inverse kinematics, the static equilibrium equations and the workspace analysis. Because all these equations are obtained based on the cable segment lengths, many square roots appear in the equations. The boundary equations for different arrangements, i.e., preload, non-zero stiffness and external forces, are obtained separately in order to simplify the analysis. The boundary equations of each cable force for any situation can be obtained by combining the equations based on the matrix superposition principle. It is verified that the mechanism has a significantly large workspace within which the cables and the springs can be maintained in tension compared to a standard mechanism actuated with three motors.
Simulation of Differentials in Four-Wheel Drive Vehicles Using Multibody Dynamics
Authors: Virlez Geoffrey , Bru¨ls Olivier , Duysinx Pierre , Poulet Nicolas
Published: June 2012

The dynamic performance of vehicle drivetrains is significantly influenced by differentials which are subjected to complex phenomena. In this paper, detailed models of TORSEN differentials are presented using a flexible multibody simulation approach, based on the nonlinear finite element method. A central and a front TORSEN differential have been studied and the numerical results have been compared with experimental data obtained on test bench. The models are composed of several rigid and flexible bodies mainly constrainted by flexible gear pair joints and contact conditions. The three differentials of a four wheel drive vehicle have been assembled in a full drivetrain in a simplified vehicle model with modeling of driveshafts and tires. These simulations enable to observe the four working modes of the differentials with a good accuracy.
Checking Mobility and Decomposition of Linkages via Pebble Game Algorithm
Authors: Sljoka Adnan , Shai Offer , Whiteley Walter
Published: June 2012

The decomposition of linkages into Assur graphs (Assur groups) was developed by Leonid Assur in 1914 - to decompose a linkage into fundamental minimal components for the analysis and synthesis of the linkages. In the paper, some new results and new methods are introduced for solving problems in mechanisms, bringing in methods from the rigidity theory community. Using these techniques, an investigation of Assur graphs and the decomposition of linkages has reworked and extended the decomposition using the well developed mathematical concepts from theory of rigidity and directed graphs. We recall some vocabulary and provide an efficient algorithm for decomposing 2-dimensional linkages into Assur components using strongly connected decompositions of graphs and a fast combinatorial Pebble Game Algorithm, which has been recently used in the study of rigidity and flexibility of structures and in fast analysis of large biomolecular structures such as proteins. Working on a one degree of freedom mechanism, we apply our algorithm to give the Assur decomposition. The Pebble Game Algorithm on such a mechanism is presented, along with an overview of the key properties and advantages of this elegant algorithm. We show how the pebble game algorithm can be used in the analysis and synthesis of linkages to mechanical engineering community. Core techniques and algorithms easily generalize to 3-dimensional structures, and can be further adapted to entire suite of other (body-bar) types of kinematic structures.
Technology Characterization Models and Their Use in Designing Complex Systems
Authors: Parker Robert R. , Malak Richard J.
Published: June 2012

Prior research suggests that set-based design representations can be useful for facilitating collaboration among engineers in a design project. However, existing set-based methods are limited in terms of how the sets are constructed and in their representational capability. The goal of this research is to demonstrate more general set-based design methods that are effective for characterizing and comparing competing technologies in a utility-based decision framework. To demonstrate the methods and compare their relative strengths and weaknesses, different technologies for a power plant condenser will be compared. The capabilities of different condenser technologies will be characterized in terms of sets defined over the space of common condenser attributes. It will be shown that designers can use the resulting sets to explore the space of possible condenser designs quickly and effectively. It is expected that this technique will be a useful tool for system designers to evaluate new technologies and compare them to existing ones. We compare four representational methods by measuring the solution accuracy (compared to another optimization procedure’s solution), computation time, and scalability (how results change with different data sizes). The results demonstrate that a support vector domain description-based method provides the best combination of these traits for this example.
On Electrostatically Actuated CNT Bio-Sensors
Authors: Caruntu Dumitru I. , Salinas Trevino Cone S.
Published: June 2012

This paper deals with electrostatically actuated Carbon NanoTubes (CNT) cantilevers for bio-sensing applications. There are three kinds of forces acting on the CNT cantilever: electrostatic, elastostatic, and van der Waals. The van der Waals forces are significant for values of 50 nm or lower of the gap between the CNT and the ground plate. As both forces electrostatic and van der Waals are nonlinear, and the CNT electrostatic actuation is given by AC voltage, the CNT dynamics is nonlinear parametric. The method of multiple scales is used to investigate the system under soft excitations and/or weakly nonlinearities. The frequency-amplitude and frequency-phase behavior are found in the case of primary resonance. The CNT bio-sensor is to be used for mass detection applications.
Guidelines for Engineering Design Creativity: Design of Experiments
Authors: Rodriguez Salvador M. , Mendoza Miguel , Gonzalez Rafael , Vargas Hernandez Noe , Okudan Gu¨l , Schmidt Linda C.
Published: June 2012

Experiments in engineering design creativity have the general objective of increasing the understanding of the creative design process, for example, experiments on the use of brainstorming, or a new ideation method or software to increase idea generation. This type of experiments is most of the time difficult to perform. In general, the difficulty is derived from the nature of the experiment which involves human subjects in a creative process solving design problems. The subjects, creative process, method involved, and design problem, each brings an abundance of variables some of which are qualitative (e.g. subject’s personality). Based on the extensive experience running engineering design creativity experiments, the authors present a review of major issues related to the design of experiments (DOE) of engineering design creativity experiments. First, an overview of creativity experimentation is presented; this includes the identification of key elements: subject, design process, treatment, controls, output and environment. Second, an overview of the design of experiment (DOE) steps is presented: hypothesis, factors, responses, etc. Third, for each step in the DOE the authors identify typical issues related to engineering design creativity. Each issue is analyzed, referred to other experiments in the literature, and a series of practical recommendations are made. The scope of the paper is limited to engineering design creativity experiments, more specifically, when the assessment is performed on the outcome. Also, the focus is on the “conceptual model” (i.e. planning stage) of DOE. Future papers will focus on the execution of the experiment and the assessment process. The authors hope that these guidelines help designologists improve the relevance, significance, and accuracy of creativity experiments.
Selecting a Design-Stage Energy Estimation Approach for Manufacturing Processes
Authors: Weissman Alexander , Gupta Satyandra K.
Published: June 2012

Manufacturing is an energy-intensive process which could account for significant energy consumption worldwide. Reducing energy consumption on a product level, in addition to a process or facility level, is being seen as a more worthwhile endeavor in light of rising energy costs and environmental concerns. To accomplish this, it is necessary to consider the role of product design in energy consumption. It is possible to design a product such that its manufacture consumes less energy. However, this requires a good model of energy consumption based on the design parameters. A good model must be detailed enough to yield accurate results, but at the same time simple enough such that it can be applied easily and consistently in day-to-day design work. In this paper, we propose an approach for generating such a model by decomposing the manufacturing process into its energy-consuming components. For each component, the relevant design and manufacturing parameters can be elicited by performing sensitivity analysis through analysis and experimentation. Parameters which do not greatly contribute to variance in energy consumption can be held constant, thus simplifying the model. Thus, the simplest possible model can be derived for a specified level of accuracy. We illustrate that critical parameters from energy point of view can differ greatly from process to process by investigating representative manufacturing processes in four general categories: additive, subtractive, forming, and solidification. Finally, we present a case study for injection molding.
Using Lamina Emergent Mechanisms to Develop Credit-Card-Sized Products
Authors: Albrechtsen Nathan B. , Magleby Spencer P. , Howell Larry L.
Published: June 2012

The compactness and portability of credit-card-sized products create a strong motivation for their development. This paper proposes that lamina emergent mechanisms (LEMs) provide a means for expanding the capabilities of credit-card-sized mechanisms. LEMs are a type of compliant mechanism that is fabricated from sheet goods with motion that emerges from the sheet. A review of the current state-of-the-art in credit-card-sized mechanisms reveals that there are two primary types of mechanisms most commonly used in this form factor: rigid-body mechanisms and in-plane compliant mechanisms. The challenges of each of these mechanism areas and the LEM advantage corresponding to each challenge are described. Criteria are developed for determining if a product is a suitable candidate for using LEM technology to create a credit-card-sized mechanism. The credit-card-sized LEM advantages and suitability criteria are illustrated through an example product—a compact lancing device that could be used as a main component for a more portable epinephrine syringe.
Vision Based Fault Detection of Automated Assembly Equipment
Authors: Szkilnyk Greg , Hughes Kevin , Surgenor Brian
Published: June 2012

Machine faults and breakdowns are a concern for the manufacturing industry. Automated assembly machines typically employ many different types of sensors to monitor machine health and feedback faults to a central controller for review by a technician or engineer. This paper describes progress with a project whose goal is to examine the effectiveness of using machine vision to detect ‘visually cued’ faults in automated assembly equipment. Tests were conducted on a laboratory scale conveyor apparatus that assembles a simple 3-part component. The machine vision system consisted of several conventional webcams and image processing in LabVIEW. Preliminary results demonstrated that the machine vision system could identify faults such as part jams and feeder jams; however the overall effectiveness was limited as this technique can only detect faults known prior to creating the vision system. Future work to create a more robust system is currently underway.