bluuebunny/crossref_metadata_2025 huggingface dataset:
Body sizes, cumulative and allometric degree distributions across natural food webs
Authors: Digel Christoph , Riede Jens O. , Brose Ulrich
Published: March 2011

The distributions of body masses and degrees (i.e. the number of trophic links) across species are key determinants of food‐web structure and dynamics. In particular, allometric degree distributions combining both aspects in the relationship between degrees and body masses are of critical importance for the stability of these complex ecological networks. They describe decreases in vulnerability (i.e. the number of predators) and increases in generality (i.e. the number of prey) with increasing species’ body masses. We used an entirely new global body‐mass database containing 94 food webs from four different ecosystem types (17 terrestrial, 7 marine, 54 lake, 16 stream ecosystems) to analyze (1) body mass distributions, (2) cumulative degree distributions (vulnerability, generality, linkedness), and (3) allometric degree distributions (e.g. generality – body mass relationships) for significant differences among ecosystem types. Our results demonstrate some general patterns across ecosystems: (1) the body masses are often roughly log‐normally (terrestrial and stream ecosystems) or multi‐modally (lake and marine ecosystems) distributed, and (2) most networks exhibit exponential cumulative degree distributions except stream networks that most often possess uniform degree distributions. Additionally, with increasing species body masses we found significant decreases in vulnerability in 70% of the food webs and significant increases in generality in 80% of the food webs. Surprisingly, the slopes of these allometric degree distributions were roughly three times steeper in streams than in the other ecosystem types, which implies that streams exhibit a more pronounced body mass structure. Overall, our analyses documented some striking generalities in the body‐mass (allometric degree distributions of generality and vulnerability) and degree structure (exponential degree distributions) across ecosystem types as well as surprising exceptions (uniform degree distributions in stream ecosystems). This suggests general constraints of body masses on the link structure of natural food webs irrespective of ecosystem characteristics.
Using sensitivity analysis to identify keystone species and keystone links in size‐based food webs
Authors: Berg Sofia , Christianou Maria , Jonsson Tomas , Ebenman Bo
Published: March 2011

Human‐induced alterations in the birth and mortality rates of species and in the strength of interactions within and between species can lead to changes in the structure and resilience of ecological communities. Recent research points to the importance of considering the distribution of body sizes of species when exploring the response of communities to such perturbations. Here, we present a new size‐based approach for assessing the sensitivity and elasticity of community structure (species equilibrium abundances) and resilience (rate of return to equilibrium) to changes in the intrinsic growth rate of species and in the strengths of species interactions. We apply this approach on two natural systems, the pelagic communities of the Baltic Sea and Lake Vättern, to illustrate how it can be used to identify potential keystone species and keystone links. We find that the keystone status of a species is closely linked to its body size. The analysis also suggests that communities are structurally and dynamically more sensitive to changes in the effects of prey on their consumers than in the effects of consumers on their prey. Moreover, we discuss how community sensitivity analysis can be used to study and compare the fragility of communities with different body size distributions by measuring the mean sensitivity or elasticity over all species or all interaction links in a community. We believe that the community sensitivity analysis developed here holds some promise for identifying species and links that are critical for the structural and dynamic robustness of ecological communities.
Clinical and hormonal status of infants with nonmosaic XXY karyotype
Authors: Lahlou Najiba , Fennoy Ilene , Ross Judith L , Bouvattier Claire , Roger Marc
Published: March 2011

Aim:  To compare our recent findings in a cohort of 77 nonmosaic XXY infants <2 years of age with clinical and biological features already reported.

Results:  The majority of reported XXY neonates had normal external genitalia. Only undescended testes and/or micropenis were identified reasons for referral. Delayed ambulation and speech skills were also indications for postnatally karyotyping. All subjects from our cohort (73 prenatally detected subjects, five postnatal diagnoses) had height and weight within the normal range, and were not dysmorphic. Insulin‐like‐peptide‐3 and testosterone secretion by Leydig cells appeared normally sensitive to luteinizing hormone. In reported studies, inhibin B levels were within normal range, anti‐Mullerian hormone levels were normal or high and follicle‐stimulating hormone (FSH) levels were significantly higher than control values, data consistent with a relative resistance to FSH.

Conclusion:  Early detection of Klinefelter syndrome is desirable for prospectively monitoring the apparition of developmental problems and the progressive decline in the tubular function of the testis, with the hope of designing future conservative interventions before germ cell degeneration is completed.
Tenascin‐C and Matrix Metalloproteinase‐9 Levels in Crevicular Fluid of Teeth and Implants
Authors: Özçakır‐Tomruk Ceyda , Chiquet Matthias , Mericske‐Stern Regina
Published: March 2011

Background: The role of and interaction between bacterial infection and biomechanical impact in the development of peri‐implant inflammatory processes is not clear.

Objective: To determine the amount and concentration of tenascin‐C (TNC) in gingival crevicular fluid (GCF) around teeth and in peri‐implant sulcus fluid from healthy implants and implants with peri‐implantitis, and to correlate it with matrix metalloproteinase‐9 (MMP‐9) levels.

Materials and Methods: Seven control individuals and 18 patients with 41 implants with/without peri‐implantitis were included. GCF was collected with filter strips and volumes were measured with a Periotron device. The amount of serum albumin per sample was quantified by densitometric analysis of Coomassie‐stained sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Relative activity of MMP‐9 was determined from the densitometry of zymograms. Amounts and concentrations of TNC were evaluated by ELISA.

Results: Relative MMP‐9 activity was increased in peri‐implantitis. A tendency was observed to measure higher TNC concentrations at teeth than at implants. The amount of TNC in GCF collected from healthy implant sites and the peri‐implantitis sites was significantly different. Based on immunoblotting, TNC in GCF seemed degraded. In contrast to TNC, MMP‐9 was significantly related to the PD and the volume of GCF.

Conclusion: TNC is known to be induced in inflammation. The increase found in peri‐implantitis was less than expected. In the context of peri‐implantitis, TNC might be a marker of bone remodelling rather than inflammation and infection. A possible proteolytic degradation of TNC during peri‐implantitis needs to be studied.
Preclinical Pharmacology and Safety of a Novel Avidin Derivative for Tissue‐Targeted Delivery of Radiolabelled Biotin
Authors: Petronzelli Fiorella , Anastasi Anna M. , Pelliccia Angela , Santapaola Daniela , Albertoni Claudio , Rosi Antonio , Leoni Barbara , Ferrari Liliana E. , Paganelli Giovanni , Gramiccioli Giancarlo , Pesce Daniela , Alfano Anna M. , Stasi Maria A. , De Santis Rita
Published: March 2011

Abstract:  We recently described an oxidized avidin variant, named AvidinOX®, which is a product that chemically links to tissue proteins while maintaining the capacity to uptake intravenously administered biotin. Such product proved to be successful in targeting radionuclide therapy in a mouse model of inoperable breast cancer. Here, we show that the uptake of a single or multiple doses of biotin (up to five times), by the tissue‐bound AvidinOX®, is stable for 2 weeks. Taking into account that oxidized avidin is the first chemically reactive protein to be proposed for clinical use, we evaluated its tolerability, immunogenicity and mutagenicity. Present in vitro data indicate that AvidinOX® (up to 10 μg/5 × 105 cells) does not affect cell viability or proliferation of PC3 human prostate cancer or 3T3 mouse fibroblast cell lines as well as primary mouse spleen cells. Safety pharmacology and toxicology studies were conducted using AvidinOX® up to the highest concentration compatible with its solubility (about 12 mg/mL), representing four times the product concentration intended for human use, and in the maximum administrable volume compatible with each study system. The intramuscular administration in rat and monkey induced a moderate to strong inflammatory response particularly after a second administration and consistently with the induction of an immune response. Interestingly, the intramuscular administration of AvidinOX® to rodents and monkeys exhibiting very high anti‐avidin antibody titres was well tolerated with no systemic symptoms of any kind. Intravenous administration of AvidinOX®, performed to mimic an accidental injection of the dose intended for a local administration (15 μL of 3.3 mg/mL solution), showed significant localization of the product into the spleen not associated with uptake of the radiolabelled biotin intravenously injected after 24 hr, thus suggesting rapid inactivation. No mutagenic activity was induced by oxidized avidin in prokaryotic and eukaryotic cells. Overall, the present data indicate that AvidinOX® is well tolerated in rodents and non‐human primates, thus supporting its clinical use within protocols of radionuclide therapy of inoperable tumour lesions.
Does the patch fit the stoma? A study on peristoma geometry and patch use in laryngectomised patients
Authors: van der Houwen E.B. , van Kalkeren T.A. , Post W.J. , Hilgers F.J.M. , van der Laan B.F.A.M. , Verkerke G.J.
Published: March 2011

Clin. Otolaryngol. 2011, 36, 235–241

Objective:  To determine the geometry of (peri)stomas of laryngectomised patients in relation to patch use. This data will enable improvement of tracheostoma interfaces, specifically addressing patients currently unable to use stoma patches. The low use of Heat‐and‐Moisture‐Exchange (HME) filters and (hands‐free) speech valves, although very important to the quality of life of laryngectomised patients, is mainly attributed to poor fit of the adhesive patches to the stoma site. Current patch shapes are not based upon an objective (peri)stoma geometry because this geometry is unknown.

Design:  Observational anthropometric study of the (peri)stoma of laryngectomised patients.

Setting:  Ten hospitals or institutes in eight countries.

Participants:  About 191 laryngectomised patients, at least 1 year post operative.

Main outcome measures:  (Peri)stomas were photographed and measured. Patients completed a questionnaire on patch‐use. Concavity of commercially available patches was measured.

Results:  In countries with a financial reimbursement system 58% of the patients use patches, compares to only 9% in other countries. Patches stay in situ for an average of 33.3 h. Patch and non‐patch users differ on five out of ten measured geometrical parameters. Most striking differences are that patch users have much shallower peristomas (13 versus 18 mm), and stomas far more parallel to the anterior neck plane. The deepest commercially available patch is only 7 mm deep.

Conclusions:  This study provides detailed (peri)stoma geometry data of a divers population, and for the first time in relation to patch‐use. It reveals a serious mismatch between patients and patches. With these data new patches can be developed that could dramatically improve rehabilitation after laryngectomy.
Imidazoline Antihypertensive Drugs: Selective I1‐Imidazoline Receptors Activation
Authors: Nikolic K. , Agbaba D.
Published: March 2011

Involvement of imidazoline receptors (IR) in the regulation of vasomotor tone as well as in the mechanism of action of some centrally acting antihypertensives has received tremendous attention. To date, pharmacological studies have allowed the characterization of three main imidazoline receptor classes, the I1‐imidazoline receptor which is involved in central inhibition of sympathetic tone to lower blood pressure, the I2‐imidazoline receptor which is an allosteric binding site of monoamine oxidase B (MAO‐B), and the I3‐imidazoline receptor which regulates insulin secretion from pancreatic β‐cells. All three imidazoline receptors represent important targets for cardiovascular research. The hypotensive effect of clonidine‐like centrally acting antihypertensives was attributed both to α2‐adrenergic receptors and nonadrenergic I1‐imidazoline receptors, whereas their sedative action involves activation of only α2‐adrenergic receptors located in the locus coeruleus. Since more selective I1‐imidazoline receptors ligands reduced incidence of typical side effects of other centrally acting antihypertensives, there is significant interest in developing new agents with higher selectivity and affinity for I1‐imidazoline receptors. The selective imidazoline receptors agents are also more effective in regulation of body fat, neuroprotection, inflammation, cell proliferation, epilepsy, depression, stress, cell adhesion, and pain. New agonists and antagonists with high selectivity for imidazoline receptor subtypes have been recently developed. In the present review we provide a brief update to the field of imidazoline research, highlighting some of the chemical diversity and progress made in the theoretical studies of imidazoline receptor ligands.
A Time Domain Inverse Method for Identification of Random Acoustic Sources at Launch Vehicle Lift-Off
Authors: Troclet B. , Alestra S. , Srithammavanh V. , Terrasse I.
Published: March 2011

In order to characterize the lift-off acoustic environment of launch vehicles, EADS has developed an inverse method via a time domain boundary integral equation approach using an optimal control method. An industrial application of the method is presented via the identification of acoustic sources of ARIANE 5 from lift-off in-flight measurements. As the lift-off acoustic field is random in nature, the optimization process is performed using the cross-correlation functions matrix measurement. After having characterized the sources from pressure measurements, the complete environment is rebuilt by an acoustic direct computation from the obtained acoustic sources. We finally estimate the loads created by the acoustic field by integrating the resulting pressures over all surfaces of the launchers.
Active Control of Vehicle Transient Powertrain Noise Using a Twin-FXLMS Algorithm
Authors: Duan Jie , Li Mingfeng , Lim Teik C. , Lee Ming-Ran , Vanhaaften Wayne , Cheng Ming-Te , Abe Takeshi
Published: March 2011

Powertrain noise is a major component of vehicle interior noise and thus has a significant effect on the overall sound quality. It is typically dominated by harmonics in the lower audible frequency range, which are directly related to the engine firing orders. In order to achieve a more comfortable environment and pleasing driving experience, an active noise control (ANC) applying advanced filtered-x least mean squares (FXLMS) algorithm is employed to reduce the vehicle interior noise by targeting these harmonics. The proposed ANC system is designed to control multiple orders of the engine noise response simultaneously. It is also uniquely formulated with a twin-FXLMS algorithm to prevent harmonic interference that often resulted in overshoot at some adjacent orders, especially at low engine speed range where the reference sinusoids are close together. In fact, the interference issue is one of the critical problems that previously plagued the use of the conventional FXLMS algorithm. The basic design of the twin-FXLMS algorithm splits the adaptive filter into two sets. This allows different sum of reference sinusoids to be fed into each adaptive filter in order to widen the frequency separation between two adjacent harmonics. Finally, the performances of proposed twin-FXLMS are validated by numerical simulations.
An Adaptive Multi-Objective Controller for Flexible Rotor and Magnetic Bearing Systems
Authors: Sahinkaya M. Necip , Abulrub Abdul-Hadi G. , Burrows Clifford R.
Published: March 2011

This paper considers two issues in the vibration of rotating machines, namely, control of rotor vibration and control of the forces transmitted to the base. An adaptive multi-objective method is developed to tackle these issues simultaneously using magnetic bearings. A two-stage weighting strategy is developed, involving base weightings calculated by using a singular value decomposition of the system’s receptance matrices and an adjustable single weighting parameter tuned automatically to shift the balance between the two objective functions in accordance with performance specifications. This new real-time controller does not require measurements in addition to those required for the open-loop adaptive strategy. Frequency and time domain simulations of an existing experimental rig are used to assess the effectiveness of the proposed multi-objective adaptive controller as a precursor to an experimental study.
A Simple Transversely Isotropic Hyperelastic Constitutive Model Suitable for Finite Element Analysis of Fiber Reinforced Elastomers
Authors: Brown Leslee W. , Smith Lorenzo M.
Published: March 2011

A transversely isotropic fiber reinforced elastomer’s hyperelasticity is characterized using a series of constitutive tests (uniaxial tension, uniaxial compression, simple shear, and constrained compression test). A suitable transversely isotropic hyperelastic invariant based strain energy function is proposed and methods for determining the material coefficients are shown. This material model is implemented in a finite element analysis by creating a user subroutine for a commercial finite element code and then used to analyze the material tests. A useful set of constitutive material data for multiple modes of deformation is given. The proposed strain energy function fits the experimental data reasonably well over the strain region of interest. Finite element analysis of the material tests reveals further insight into the materials constitutive nature. The proposed strain energy function is suitable for finite element use by the practicing engineer for small to moderate strains. The necessary material coefficients can be determined from a few simple laboratory tests.
Microstructure and Thermal Stress Distributions in Laser Carbonitriding Treatment of Ti–6Al–4V Alloy
Authors: Yilbas B. S. , Akhtar S. S. , Matthews A. , Karatas C. , Leyland A.
Published: March 2011

The results of experiments into laser assisted gas carbonitriding of a Ti–6Al–4V alloy are reported. The temperature and thermal stress fields were simulated using finite element analysis. Microstructural changes in the laser treated region were examined using scanning electron microscopy, energy dispersive X-ray, and X-ray diffraction. In the process, a carbon film was formed at the workpiece surface prior to laser processing and the laser scanning speed was kept constant during the process. It was found that the laser treated layer extended uniformly along the surface; the depth of the layer was about 55 μm. The formation of TiCxN1−x, TiN, and TiC in the surface region enhances the hardness significantly.
Solar Radiation on Horizontal Tubular Microalgae Photobioreactor: Direct Beam Radiation
Authors: Maor T. , Appelbaum J.
Published: March 2011

The solar irradiation on a photobioreactor plant for cultivating microalgae products such as dyes, vitamin, and biofuel is formulated, calculated, and verified. The outdoor solar plant consists of multiple horizontal tubes arranged in multiple vertical walls. The solar irradiation determines the growth rate of the algae; therefore, calculating the amount of solar radiation on the plant is important to estimate the production of microalgae. The incident direct beam irradiation on the tubes is calculated, taking into account tube and wall shading.
PDE-Constrained Gaussian Process Model on Material Removal Rate of Wire Saw Slicing Process
Authors: Zhao Hongxu , Jin Ran , Wu Su , Shi Jianjun
Published: March 2011

Thickness uniformity of wafers is a critical quality measure in a wire saw slicing process. Nonuniformity occurs when the material removal rate (MRR) changes over time during a slicing process, and it poses a significant problem for the downstream processes such as lapping and polishing. Therefore, the MRR should be modeled and controlled to maintain the thickness uniformity. In this paper, a PDE-constrained Gaussian process model is developed based on the global Galerkin discretization of the governing partial differential equations (PDEs). Three features are incorporated into the statistical model: (1) the PDEs governing the wire saw slicing process, which are obtained from engineering knowledge, (2) the systematic errors of the manufacturing process, and (3) the random errors, including both random manufacturing errors and measurement noises. Real experiments are conducted to provide data for the validation of the PDE-constrained Gaussian process model by estimating the model coefficients and further using the model to predict the overall MRR profile. The results of cross-validation indicate that the prediction performance of the PDE-constrained Gaussian process model is better than the widely used universal Kriging model with a mean of second order polynomial functions.
A Longitudinal Study of Remodeling in a Revised Peripheral Artery Bypass Graft Using 3D Ultrasound Imaging and Computational Hemodynamics
Authors: McGah Patrick M. , Leotta Daniel F. , Beach Kirk W. , Riley James J. , Aliseda Alberto
Published: March 2011

We report a study of the role of hemodynamic shear stress in the remodeling and failure of a peripheral artery bypass graft. Three separate scans of a femoral to popliteal above-knee bypass graft were taken over the course of a 16 month period following a revision of the graft. The morphology of the lumen is reconstructed from data obtained by a custom 3D ultrasound system. Numerical simulations are performed with the patient-specific geometries and physiologically realistic flow rates. The ultrasound reconstructions reveal two significant areas of remodeling: a stenosis with over 85% reduction in area, which ultimately caused graft failure, and a poststenotic dilatation or widening of the lumen. Likewise, the simulations reveal a complicated hemodynamic environment within the graft. Preliminary comparisons with in vivo velocimetry also showed qualitative agreement with the flow dynamics observed in the simulations. Two distinct flow features are discerned and are hypothesized to directly initiate the observed in vivo remodeling. First, a flow separation occurs at the stenosis. A low shear recirculation region subsequently develops distal to the stenosis. The low shear region is thought to be conducive to smooth muscle cell proliferation and intimal growth. A poststenotic jet issues from the stenosis and subsequently impinges onto the lumen wall. The lumen dilation is thought to be a direct result of the high shear stress and high frequency pressure fluctuations associated with the jet impingement.
Homogenization of the Reynolds Equation Governing Hydrodynamic Flow in a Rotating Device
Authors: Almqvist Andreas
Published: March 2011

In this paper, a method facilitating the analysis of the effects of surface roughness on the lubrication of a rotating device is presented. The analysis utilizes homogenization—a suitable technique for averaging the effects of roughness as modeled by the Reynolds equation. The originality of this work lies in a novel way of deriving the so called local problems, also known as microbearing problems. It is clearly shown how this increases the computational efficiency by eliminating the dependence of the global coordinates on the formulation of these local problems. This does not only speed up the computation, it also means that the derived flow factors or flow tensors require less storage space. To provide for good usability, alongside the flow factors for the averaged Reynolds equation, the correction factors for the averaged friction torque (and force) and the expression for averaged load carrying capacity are presented here.
Symplectic Elasticity: Theory and Applications
Authors: Lim C. W. , Xu X. S.
Published: March 2011

Many of the early works on symplectic elasticity were published in Chinese and as a result, the early works have been unavailable and unknown to researchers worldwide. It is the main objective of this paper to highlight the contributions of researchers from this part of the world and to disseminate the technical knowledge and innovation of the symplectic approach in analytic elasticity and applied engineering mechanics. This paper begins with the history and background of the symplectic approach in theoretical physics and classical mechanics and subsequently discusses the many numerical and analytical works and papers in symplectic elasticity. This paper ends with a brief introduction of the symplectic methodology. A total of more than 150 technical papers since the middle of 1980s have been collected and discussed according to various criteria. In general, the symplectic elasticity approach is a new concept and solution methodology in elasticity and applied mechanics based on the Hamiltonian principle with Legendre’s transformation. The superiority of this symplectic approach with respect to the classical approach is at least threefold: (i) it alters the classical practice and solution technique using the semi-inverse approach with trial functions such as those of Navier, Lévy, and Timoshenko; (ii) it consolidates the many seemingly scattered and unrelated solutions of rigid body movement and elastic deformation by mapping with a series of zero and nonzero eigenvalues and their associated eigenvectors; and (iii) the Saint–Venant problems for plane elasticity and elastic cylinders can be described in a new system of equations and solved. A unique feature of this method is that bending of plate becomes an eigenvalue problem and vibration becomes a multiple eigenvalue problem.
Laser Cutting of Small Diameter Holes Into Alumina Tiles: Thermal Stress Analysis
Authors: Yilbas B. S. , Akhtar S. S. , Karatas C.
Published: March 2011

Laser cutting of small diameter holes in alumina tiles is carried out. Temperature and stress fields are predicted numerically using the ABAQUS finite element code. The cut sections are examined by incorporating scanning electron microscope and optical microscope. The residual stress developed in the cutting section is determined using the X-ray diffraction technique. It is found that high residual stresses are formed in the cutting section, and predictions agree well with the experimental results. The laser cut edges are found to be free from the large cracks. However, interconnected shallow cracks are observed at the hole cut surface.
Supply-Chain Product Development Collaboration Using Configurable Product Platform Models
Authors: Wahl A. , Gedell S. , Johannesson H.
Published: March 2011

Collaborative product platform development in the supply chain faces problems not only with inefficient knowledge management and information exchange between collaborating partners, but also with configuration and carryover strategies — both of which result in large amounts of system variants to maintain, and restrained reuse. To address these problems, this article proposes a new, more system-oriented and abstract, knowledge-based approach to define and describe configurable product platforms. A new platform model concept with a new modeling procedure, consisting of linked, fully configurable generic and autonomous sub-systems, has been devised. The model has been implemented as a separate platform configuration (PFC) system within an envisioned product lifecycle management (PLM) system architecture. The PFC system is the common base for system configuration as well as for information and knowledge exchange between collaborating partners. The proposed platform model and collaborative modeling procedure have been partly verified and validated, in cooperation with the industrial partners participating in a joint research project.
Design, Simulation, and Implementation of an Electric Hybrid Motorcycle
Authors: Asaei Behzad , Seyed mohammadi Seyed Hosein , Yousefi koma Aghil , Habibidoost Mahdi , Aghnoot Roohollah , karimi Behzad , Pourhosseini Seyed Majid , Jalali Hamed
Published: March 2011

This paper presents a general integrated procedure of fabricating a Hybrid Electric Motorcycle (HEM). Firstly, a simple model designed and simulated using ADVISOR2002 and the proposed model is exported to MATLAB/SIMULINK. Secondly, the controller schematic and its optimized control strategy are described. In addition, the ratings of the components including the batteries, electric motor, and internal combustion engine (ICE) are calculated based on the design. A 125 cc ICE motorcycle is selected for conversion to HEM. A brushless DC (BLDC) motor assembled in front wheel as accessory propellant. The nominal powers are 8.2 kW at 8500 rpm and 500 W for the ICE and BLDC respectively. The original motorcycle has a Continues Variable Transmission (CVT) that is the best choice for the HEM power transmission because it can operate in automatic handling mode and has high efficiency. Moreover, by using CVT the ICE can be started while it is running at 15 km/h. Finally, the three operating modes of the HEM, the servo motors, and the LCD panel were explained.
An Approach for Acceleration Analysis of Lower Mobility Parallel Manipulator
Authors: Liu Haitao , Huang Tian , Chetwynd Derek G.
Published: March 2011

This paper presents an approach for velocity and acceleration analyses of lower mobility parallel manipulators. Based on the definition of the acceleration motor, the forward/inverse velocity and acceleration equations are formulated with the goal to integrate the relevant analyses under a unified framework based on the generalized Jacobian. A new Hessian matrix of serial kinematic chains (or limb) is developed in an explicit and compact form using Lie bracket. This idea is then extended to cover parallel manipulators by considering the loop closure constraints. A 3-PRS parallel manipulator with coupled translational and rotational moving capabilities is taken as example to illustrate the generality and effectiveness of this approach.
An Intelligent Exoskeleton for Lower Limb Rehabilitation
Authors: Ashrafiuon Hashem , Grosh Kent , Burke Kevin J. , Bommer Kathleen
Published: March 2011

A lightweight adjustable exoskeleton is designed to exercise human legs of varying size and weights. The exoskeleton is actuated by three DC motors at the hip, knee, and ankle. An experimental setup with motor controllers, power supplies, a controlled board, and a computer is developed for closed loop control. A sliding mode control law is designed and implemented to exercise an articulated mannequin leg. It is shown that the exoskeleton is able to adapt to external forces making it suitable to aid in the human leg rehabilitation process.
A Comparative Study of Life Cycle Cost Analysis of Pumps
Authors: Waghmode Laxman Yadu , Sahasrabudhe Anil Dattatraya
Published: March 2011

For a product to be commercially successful and increasingly competitive in this global market place, it is imperative that engineers must understand and design for each phase in the life cycle of a product. The life cycle cost (LCC) of any piece of equipment, such as a pump represents the total cost to procure, install, operate, maintain and dispose of that equipment. For sustainment dominated products or systems, the lifetime energy and/or maintenance costs dominate the life cycle cost as compared to its initial cost. The initial cost is only a fraction of the life cycle cost. Therefore, a due consideration to the life cycle cost issues at product design stage is quite essential. The LCC analysis is recommended only at the product design phase, as up to 80% of product LCC is committed at this phase. A better understanding of the cost components that make up the life cycle cost is expected to provide the product designers an opportunity to considerably reduce product LCC. In this paper, a methodology for LCC analysis based on reliability and maintainability principles has been applied to three different pumps and the results of analysis have been compared. For analysis purpose, two pumps have been selected from the literature and the data available therein is utilized. The third pump is selected from a well known pump manufacturer from India and the required data is obtained directly from the manufacturer. To model the maintenance and repair cost the concept of expected number of failures in a given time interval has been applied. The maintenance and repair cost is estimated for two different maintenance and repair strategies, the renewal/replacement upon failure strategy and minimal repair upon failure strategy and under the conditions of constant failure rate (exponential distribution) in first case and increasing failure rate (Weibull distribution) in the second case. The results obtained have been presented and compared at the end. The methodology presented in this paper is expected to help the pump designers to estimate and compare the life cycle cost of their different design alternatives.
Seeded Fault Testing of Military Ground Vehicles as a Pathway to Condition Based Maintenance
Authors: Hillegass Matthew J. , Rabeno Eric L.
Published: March 2011

The performance of military ground vehicle systems is being degraded due to high operation tempo and exposure to extreme environments while performing in-theater service. To address this issue, the US Army is implementing a policy of Condition Based Maintenance which is supported by the Army Material System Analysis Activity (AMSAA). The vision of this policy is to base the maintenance of systems upon the actual condition of the system and not upon time- or distance-based schedules. This capability will be enabled by the application of usage, diagnostic and prognostic processes executed on a Health and Usage Monitoring System (HUMS) installed on these vehicle systems. A thorough understanding of the ways in which the system condition is degenerated and the ability of the HUMS to detect, identify, and communicate all conditions that require maintenance in a timely manner are key requirements of these processes. Seeded Fault Testing is the critical means of fulfilling these requirements. A joint Seeded Fault Testing project between AMSAA and the US Army Aberdeen Test Center (ATC) has been initiated to gain a thorough understanding of ground vehicle system condition degeneration and HUMS implementation of products and processes that can accurately identify and communicate it. A military vehicle underwent exhaustive testing in support of this project. The vehicle was subjected to specific use scenarios while carefully controlled faults are induced in engine, transmission, and other key mechanical subsystems that would degrade vehicle performance and degenerate system condition. The vehicle’s induced faults included lowered coolant levels to simulate leakage, restriction of air flow across radiators and filters to simulate dust and debris accumulation, and lowered transmission and engine oil levels to simulate leakage and usage. The objective of this project was to use the results from the seeded fault tests to establish critical thresholds, trends, and patterns that will be the basis of the creation and implementation of real-time HUMS-based algorithms that predict faults, warn operators and maintainers of imminent failures, and provide a sound foundation for Condition Based Maintenance.
On the Expected Number of Failures and Maintenance Cost Prediction of Repairable Systems From Life Cycle Cost Modeling Perspective
Authors: Waghmode Laxman Yadu , Sahasrabudhe Anil Dattatraya
Published: March 2011

The objective of this paper is to provide some useful insights on how cost driving events are related to the characteristics of failure distributions and the product lifetime (design life) in case of repairable systems. Repairable systems are those that can be restored to their fully operational capabilities by any method, other than the replacement of the entire system. In case of repairable systems, the components can be repaired or adjusted rather than replaced, whenever a breakdown occurs and thus such systems experience multiple failures over their life span. For majority of repairable systems, the life time maintenance and repair costs dominate the life cycle cost. To predict the maintenance and repair cost, failure data, maintenance data and repair time data is needed which is not readily available at the system design stage. When a repairable system is put into service, how many times it will fail over its life span depends on its reliability. Similarly, how fast the system is restored to its working condition when it fails (maintainability), also affect the costs incurred. Thus, the expected number of failures, time lost in restoring the system after each failure and cost per failure are important from life time maintenance cost prediction viewpoint. The expected number of failures depends upon the time to failure distribution of the system components and the after repair state of the system. In this paper, a modeling methodology is suggested for prediction of life time maintenance and repair cost of repairable systems based on expected number of failures. The repairable system lifetime is modeled using a two parameter Weibull distribution. The expected number of failures are estimated for renewal process (as-good-as-new after repair state) and minimal repair process (as-bad-as-old after repair state). The expected maintenance and repair costs are also evaluated for six different failure distributions. The technique has been illustrated through a specific application, namely an industrial pump and the results are presented.
Design and Modelling of Spatial Compliant Parallel Mechanisms for Large Range of Translation
Authors: Hao Guangbo , Kong Xianwen , Meng Qiaoling
Published: March 2011

A new distributed-compliance module, which can be used as a building block, is proposed at first. A novel 3-DOF compliant parallel mechanism (CPM) and its improved configuration for large range of translation are then proposed using the new building blocks. The analytical models of the spatial modules and 3-DOF translational CPMs are then presented and analyzed. The proposed improved 3-DOF translational CPM has the following merits: (1) It is approximately decoupled and has a workspace of 0.1Lmm×0.1Lmm×0.1Lmm (L: the beam length in the module) with constrained parasitic error, maximal actuation isolation and minimal lost motion. (2) Its configuration is simple and compact, and it is actuated by three linear actuators directly. (3) The normalization strategy not only simplifies the representation and derivation of the equations, but also makes the compliance matrix reflect the displacement associated with each degree of freedom in a straightforward manner. The proposed analytical model for the improved 3-DOF CPM has been verified using FEA.
Balancing Energy to Estimate Damping in a Forced Oscillator With Compliant Contact
Authors: Liang Jin-Wei , Feeny Brian
Published: March 2011

This work identifies damping parameters from compliant-contact vibration systems using energy dissipation concept. To develop the identification algorithms, the energy loss as registered in the force-displacement relationship of the real system is balanced against that of a theoretical model incorporating with an idealized compliant contact. Two approaches, including one based on the harmonic response assumption and the other directly integrating the system responses, are developed. Numerical investigations are performed to illustrate the reliability of the identification algorithms.
Geometric, Spatial Path Tracking Using Non-Redundant Manipulators via Speed-Ratio Control
Authors: Ambike Satyajit , Schmiedeler James P. , Stanisˇic´ Michael M.
Published: March 2011

Path tracking can be accomplished by separating the control of the desired trajectory geometry and the control of the path variable. Existing methods accomplish tracking of up to third-order geometric properties of planar paths and up to second-order properties of spatial paths using non-redundant manipulators, but only in special cases. This paper presents a novel methodology that enables the geometric tracking of a desired planar or spatial path to any order with any non-redundant regional manipulator. The governing first-order coordination equation for a spatial path-tracking problem is developed, the repeated differentiation of which generates the coordination equation of the desired order. In contrast to previous work, the equations are developed in a fixed global frame rather than a configuration-dependent canonical frame, providing a significant practical advantage. The equations are shown to be linear, and therefore, computationally efficient. As an example, the results are applied to a spatial 3-revolute mechanism that tracks a spatial path. Spatial, rigid-body guidance is achieved by applying the technique to three points on the end-effector of a six degree-of-freedom robot. A spatial 6-revolute robot is used as an illustration.
Wheelbase Filtering and Characterization of Road Profiles for Vehicle Dynamics
Authors: Cao Dongpu , Khajepour Amir , Song Xubin
Published: March 2011

Random road profiles and wheelbase filtering, both of which strongly affect vehicle dynamic performance characteristics, have been explored in many studies. These studies invariably focused on either characterizing road roughness or vehicle dynamics considering wheelbase filtering effect. No effort, however, has been attempted to characterize road roughness profiles upon considering vehicle wheelbase filtering effect, and then to investigate their combined roles on vehicle dynamic responses. In this study, characteristics of different random road profiles are investigated upon considering wheelbase filtering effect. Two vehicle models, including quarter-car and pitch-plane models, are then employed to analyze the combined influence of random road roughness and wheelbase filtering on vehicle dynamics. The simulation results reveal the significant difference between the characteristics of random road profiles with and without wheelbase filtering effect. The results further demonstrate that wheelbase filtering has a positive effect on vehicle vertical ride, with a negligible or small compromise on suspension travel and dynamic tire deflection.
A Review of Joint Decisions on Marketing and Supply Chain in Product Planning and Design
Authors: Qian Li , Jiao Jianxin Roger
Published: March 2011

Manufacturers design and develop numerous product variants to address different customer preferences in the competitive market. One product could be characterized by a vector of attributes such as sale price, reliability, and functionality. The challenge is how to make decisions on product or product family planning and design, supply chain, and marketing in a concurrent and integrated manner. Research on integration and coordination of product design, supply chain configuration, and marketing decisions is receiving much attention recently and need further investigation. The paper provides a comprehensive review on recent research incorporating marketing, management and engineering considerations in product planning and design.
Algebraic Algorithm for the Kinematic Analysis of Slider-Crank/Rocker Mechanisms
Authors: Figliolini Giorgio , Conte Marco , Rea Pierluigi
Published: March 2011

This paper deals with the formulation of an algebraic algorithm for the kinematic analysis of slider-crank/rocker mechanisms, which is based on the use of geometric loci, as the fixed and moving centrodes, the cubic of stationary curvature and the inflection circle. In particular, both centrodes are formulated in implicit and explicit algebraic forms by using the complex algebra. Moreover, the algebraic curves representing the moving centrodes are also recognized and proven to be Jerˇa´bek’s curves for the first time. Then, the cubic of stationary curvature along with the inflection circle are expressed in algebraic form by using the geometric invariants. Finally, the proposed algorithm has been implemented in a Matlab code and interesting numerical and graphical results are shown along with some particular cases in which the geometric loci degenerate in lines and circles.
Service Information for Product Quality
Authors: Iino Kenji , Nakao Masayuki
Published: March 2011

Engineering products go through 4 stages of lifecycle; design, production, use, and disposal. Engineers have developed tools for avoiding design flaws that cause troubles in the later stages. Accidents and malfunctions, however, still happen and some are even catastrophic. Once in the market, products require service. Whether scheduled, or unexpected, service is mostly carried out by subsidiaries of the manufacturer or sometimes unrelated specialists. When product troubles occur, service companies tend to seek solutions within their own organization without going back to the design stage. This approach may prove less costly, however, quick fixes may lead to disasters. Industries currently lack effective ways of feeding service information back to design. We analyzed some real accidents that took place in Japan where hard work in the use stage triggered the events. Information from the use stage to design will prevent accidents and also improve design to closely model reality.
Homotopy Analysis Method for Multi-Degree-of-Freedom Nonlinear Dynamical Systems
Authors: Zhang W. , Qian Y. H. , Yao M. H. , Lai S. K.
Published: March 2011

In reality, the behavior and nature of nonlinear dynamical systems are ubiquitous in many practical engineering problems. The mathematical models of such problems are often governed by a set of coupled second-order differential equations to form multi-degree-of-freedom (MDOF) nonlinear dynamical systems. It is extremely difficult to find the exact and analytical solutions in general. In this paper, the homotopy analysis method is presented to derive the analytical approximation solutions for MDOF dynamical systems. Four illustrative examples are used to show the validity and accuracy of the homotopy analysis and modified homotopy analysis methods in solving MDOF dynamical systems. Comparisons are conducted between the analytical approximation and exact solutions. The results demonstrate that the HAM is an effective and robust technique for linear and nonlinear MDOF dynamical systems. The proof of convergence theorems for the present method is elucidated as well.
Weibull Distributed Stress-Dependent Strength Analysis of Aeroengine Alloy Using Lagrange Factor Polynomial
Authors: Wong Chun Nam , Huang Hong-Zhong , Xiong Jingqi , Hu Tianyou
Published: March 2011

In this paper, the unilateral dependency of strength on stress is taken into account. And the stress-dependent strength is represented by a discrete random variable that has different conditional probability mass functions under different stress amplitudes. Then the Lagrange factor polynomial technique is developed to generate the stress-strength interference model with stress-dependent strength. This model assumes that the strength probability mass function is Weibull distributed, while the stress probability mass function is Normal distributed. Accuracy of this method is investigated by an aeroengine bearing cage alloy. Structural reliabilities are computed as 0.796 to 0.986 under several operation modes, which are analyzed by varying the Weibull shape parameter from 1 to 6. Then probability mean function estimated by Lagrange factor polynomial has relatively low errors over most span of the stress dependent strength distribution. With this approach stress-dependent strength reliability of aeroengine structural systems can be established conveniently. Meanwhile the application range of the classical stress-strength interference model can be extended.