bluuebunny/crossref_metadata_2025 huggingface dataset:
Current Constraints and Future Directions in Estimating Coextinction
Authors: MOIR MELINDA L. , VESK PETER A. , BRENNAN KARL E.C. , KEITH DAVID A. , HUGHES LESLEY , McCARTHY MICHAEL A.
Published: January 2010

Abstract:  Coextinction is a poorly quantified phenomenon, but results of recent modeling suggest high losses to global biodiversity through the loss of dependent species when hosts go extinct. There are critical gaps in coextinction theory, and we outline these in a framework to direct future research toward more accurate estimates of coextinction rates. Specifically, the most critical priorities include acquisition of more accurate host data, including the threat status of host species; acquisition of data on the use of hosts by dependent species across a wide array of localities, habitats, and breadth of both hosts and dependents; development of models that incorporate correlates of nonrandom host and dependent extinctions, such as phylogeny and traits that increase extinction‐proneness; and determination of whether dependents are being lost before their hosts and adjusting models accordingly. Without synergistic development of better empirical data and more realistic models to estimate the number of cothreatened species and coextinction rates, the contribution of coextinction to global declines in biodiversity will remain unknown and unmanaged.
Autonomic alterations and cardiac changes in epilepsy
Authors: Sevcencu Cristian , Struijk Johannes J.
Published: January 2010

Studies with heart rate variability have revealed interictal autonomic alterations in patients with epilepsy. In addition, epilepsy is frequently associated with ictal tachycardia or bradycardia, which sometimes precedes the onset of seizures. Ictal tachycardia is sometimes associated with electrocardiography (ECG) morphologic changes and ictal bradycardia often progresses to asystole. Such cardiac manifestations of seizures have been hypothesized as possible causes for sudden unexplained death in epilepsy (SUPEP). The present review relates to interictal and ictal cardiac manifestations of epilepsy with focus on heart rate, heart rate variability, and ECG changes. Aspects of the supporting mechanisms are discussed and attention is drawn to the interaction between central and peripheral effects, interictal autonomic conditions, ictal autonomic discharges, and administration of antiepileptic drugs in shaping the ictal cardiac changes. Because these interactions are complex and not totally understood, closer surveillance of patients and more experimental work is necessary to elucidate the mechanistic support of autonomic and cardiac changes in epilepsy, and to design better strategies to avoid their undesirable effects. It is also suggested that some of these changes could be used as predictors or markers for the onset of seizures.
Parental and physician beliefs regarding the provision and content of written sudden unexpected death in epilepsy (SUDEP) information
Authors: Gayatri Neti A. , Morrall Matthew C. H. J. , Jain Vivek , Kashyape Pawan , Pysden Karen , Ferrie Colin
Published: January 2010

Purpose:  The 2007 UK National Institute for Health and Clinical Excellence (NICE) guidelines for epilepsy recommend disclosing the risk of sudden unexpected death in epilepsy (SUDEP) to patients. This recommendation is not undertaken routinely, and considerable variation in individual physician practice exists. Literature indicates wariness of causing distress and anxiety, particularly to children/young people and their families through disclosing a nonpreventable risk. There has been no systematic pediatric study examining parent/guardian information needs and beliefs for risk of SUDEP and its impact on seizure management. It is important to first address these concerns before routinely imparting SUDEP information to parents following NICE recommendations.

Methods:  Two questionnaire surveys: a questionnaire examining the provision by pediatric neurologists of SUDEP information, and questionnaires examining parental beliefs and implications at two time points regarding SUDEP information provided in a leaflet. Participants were included in the study if their child had an established diagnosis of epilepsy. Factors for exclusion were single unprovoked seizure, absence seizures, patients in remission, and active discontinuation of treatment.

Results:  The majority (74%) of pediatric neurologists provided SUDEP information only to a select group of children with epilepsy and were uncertain about the effect such information would have upon the parent and child. Conversely, 91% of parents expected the pediatric neurologist to provide SUDEP risk information. The provision of this information did not have a significant immediate and longer‐term negative impact.

Discussion:  The majority of parents wanted to know about SUDEP and its associated risks. Whenever possible, SUDEP information should be given by the physician accompanied by an information leaflet.
Transient improvement after brief antiepileptic drug withdrawal in the epilepsy monitoring unit—possible relationship to AED tolerance
Authors: Azar Nabil J. , Lagrange Andre H. , Wang Lily , Song Yanna , Abou‐Khalil Bassel W.
Published: January 2010

Purpose:  A drug holiday seems to produce seizure interval prolongation (SIP) after reinstitution of antiepileptic drugs (AEDs). This effect was demonstrated mainly with carbamazepine. We evaluated SIP with newer AEDs and tested the relationship of SIP to history of AED tolerance.

Methods:  We prospectively studied patients with refractory epilepsy admitted to the Vanderbilt epilepsy monitoring unit (EMU) over a period of 12 months. We included only patients on levetiracetam, lamotrigine, or oxcarbazepine who had their AEDs withdrawn on admission and reinstituted without change upon discharge. We defined SIP as the interval from EMU discharge to first seizure minus the interval between the last two seizures before EMU admission.

Results:  A total of 43 patients completed the study; 15 were on monotherapy. SIP was greater than zero in this patient group (p < 0.0001), with a mean prolongation of 19.4 ± 28.0 days. The average SIP was higher (p = 0.01) in patients on monotherapy (29.7 ± 23.8 days) than patients on polytherapy (13.9 ± 29.0 days). SIP tended to be greater in patients with a prior history of AED tolerance (25.7 ± 36.8 days) compared to patient with no prior history of AED tolerance (14.0 ± 16.3 days).

Discussion:  SIP does occur after brief AED withdrawal. This effect is greater in patients on monotherapy and tends to be larger in patients with a history of AED tolerance. The SIP effect may be related to the phenomenon of tolerance, clinically seen as resistance to AED therapeutic effect.
Interactions between bipolar disorder and antisocial personality disorder in trait impulsivity and severity of illness
Authors: Swann A. C. , Lijffijt M. , Lane S. D. , Steinberg J. L. , Moeller F. G.
Published: January 2010

Swann AC, Lijffijt M, Lane SD, Steinberg JL, Moeller FG. Interactions between bipolar disorder and antisocial personality disorder in trait impulsivity and severity of illness.

Objective:  We investigated trait impulsivity in bipolar disorder and antisocial personality disorder (ASPD) with respect to severity and course of illness.

Method:  Subjects included 78 controls, 34 ASPD, 61 bipolar disorder without Axis II disorder, and 24 bipolar disorder with ASPD, by Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (DSM‐IV) (SCID‐I and ‐II). Data were analyzed using general linear model and probit analysis.

Results:  Barratt Impulsiveness Scale (BIS‐11) scores were higher in ASPD (effect sizes 0.5–0.8) or bipolar disorder (effect size 1.45) than in controls. Subjects with both had more suicide attempts and previous episodes than bipolar disorder alone, and more substance‐use disorders and suicide attempts than ASPD alone. BIS‐11 scores were not related to severity of crimes.

Conclusion:  Impulsivity was higher in bipolar disorder with or without ASPD than in ASPD alone, and higher in ASPD than in controls. Adverse effects of bipolar disorder in ASPD, but not of ASPD in bipolar disorder, were accounted for by increased impulsivity.
Attitudes of Italian dental and dental hygiene students toward tobacco‐use cessation
Authors: Pizzo G. , Licata M. E. , Piscopo M. R. , Coniglio M. A. , Pignato S. , Davis J. M.
Published: January 2010

Objective:  The aim of this study was to investigate the smoking habits of Italian dental and dental hygiene students and to assess their knowledge on the health effects of cigarette smoking and their attitudes toward tobacco‐use cessation (TUC) in dental practice.

Materials and methods:  Data was collected from 220 students attending the Dental and Dental Hygiene Schools (DS and DHS, respectively) at the University of Palermo (Italy).

Results:  The percentage of smokers amongst DS and DHS students was similar (32.78% vs. 32.5%) with 67.77% of DS students and 77.5% of DHS agreeing that the damages to health caused by smoking were covered in their didactic course work. A high percentage of DS (63.33%) and DHS (67.5%) students reported the relationship between smoking and a number of associated health conditions. Both DS and DHS students showed poor knowledge of TUC interventions. Both DS and DHS students reported to be conscious of their own role as a counsellor, with DHS students feeling more comfortable in approaching counselling in clinical practice. Although DS and DHS students reported a positive attitude toward TUC interventions, almost half of the students had some concerns about the effectiveness of smoking cessation activities.

Discussion:  The introduction of a comprehensive tobacco education curriculum in DS and DHS programs could further improve students’ perceptions and attitudes and provide knowledge and clinical experience which would lead to the incorporation of TUC into subsequent professional practice.
Problem‐based learning in postgraduate dental education: a qualitative evaluation of students’ experience of an orthodontic problem‐based postgraduate programme
Authors: Bearn D. R. , Chadwick S. M.
Published: January 2010

Introduction:  Problem based learning (PBL) has gained wide acceptance in undergraduate education, but less so in postgraduate education. Qualitative research methodologies can help us gain insight and understanding of the students’ experience in undertaking such programmes.

Aim:  To evaluate the experiences of postgraduate students undertaking a PBL based postgraduate programme.

Methods:  Focus groups and semi‐structured interviews were used to investigate students’ experiences. The qualitative data were coded, the codes were grouped into categories and a coding framework developed. From this a construct is proposed to give insight into students’ experiences. The validity of this construct was examined by reviewing the literature.

Results:  Students entered the programme with high expectations, but soon found they had challenges to overcome. They came to realise that they were on a journey, rather than undertaking a sequence of separate individual learning events. PBL led to significant tensions both within the individuals and the group, caused by the conflict between appreciating PBL as a ‘good thing’ and yet finding that `it just doesn’t seem to work’. The fear of failure in a high stakes setting only exacerbated these tensions. The literature review revealed an inconsistent approach to the use of PBL and its evaluation in a postgraduate/continuing medical education setting. However it did provide evidence of similar findings in qualitative studies, supporting the construct developed.

Conclusion:  We have proposed a construct to help in understanding the PBL experience for students undergoing a ‘high stakes’ orthodontic postgraduate programme with a core of PBL.
Proposed requirements for a European Doctorate in Dentistry: a discussion document prepared by a special interest group under the auspices of the Association for Dental Education in Europe
Authors: Kersten H. , Bearn D. , Gundersen S. , Holbrook P. , Kotsanos N. , Radnai M. , Virtanen J.
Published: January 2010

In the Bologna process a third cycle is distinguished at the doctoral level. In documents on the Bologna process it is advocated to harmonise the structure and requirements of the doctorate, which in Europe are characterised by a wide variety. Differences exist in all possible requirements between countries, and even between schools within one country differences can be seen. In this paper an inventory is made of these differences in the dental doctorate between European countries. Moreover, the need for necessary harmonisation of requirements for a European dental doctorate is strongly advocated and a proposal is presented.
The effects of digital image enhancement on the detection of vertical root fracture
Authors: Kamburoğlu Kıvanç , Murat Sema , Pehlivan Selcen Yüksel
Published: January 2010

Abstract –  Aim:  To determine the effects of digital image enhancement on observer ability to detect experimentally induced vertical root fractures (VRF).

Material and methods:  A total of 64 extracted human mandibular premolar teeth were used in this study. In 32 teeth, VRFs were created in the bucco‐lingual planes by gently tapping with screw‐type root‐canal pins. The remaining 32 intact teeth served as a control group. Digital images were obtained using a charge coupled device sensor. Three observers separately examined the original and four types of digitally enhanced images (enhanced using sharpness, zoom‐in, reverse‐contrast, and pseudo‐3D functions) at 1‐week intervals. All teeth were evaluated using a 5‐point scale for the presence/absence of VRF. Evaluations of each image set were repeated 1 month after the initial viewings. Kappa coefficients were calculated to investigate the degree of intra‐ and inter‐observer agreement. The areas under the receiver operating characteristic (ROC) curves (Az values) were calculated using the MedCalc statistical software. ROC values for each image type, observer and viewing were compared using t‐tests. A level of α = 0.05 was considered significant.

Results:  Kappa coefficients for intra‐observer agreement ranged from 0.304 to 0.679. Inter‐observer agreement kappa values ranged from 0.109 to 0.399 for the first reading and from 0.106 to 0.380 for the second reading. Statistical comparisons between Az values for each observer showed no significant differences (P > 0.05) among image types.

Conclusion:  There were no differences in diagnostic outcomes among differently enhanced images in the in vitro detection of VRF.
Root hypoplasia: an unusual sequela to primary tooth trauma
Authors: Tewari Nitesh , Pandey Ramesh Kumar
Published: January 2010

Abstract –  The traumatic injury to primary teeth has been associated with diverse consequences in permanent dentition. The root abnormalities in permanent teeth are relatively rare. An unusual and rare case of sequelae to primary tooth trauma has been presented here. The complexity of the impact which occurred at the age of 4 years and 8 months resulted in root hypoplasia in 11, 21, root duplication in 12 and avulsion of 22 tooth bud.
Impact energy absorption of three mouthguard materials in three environments
Authors: Lunt Darin R. , Mendel Deborah A. , Brantley William A. , Michael Beck F. , Huja Sarandeep , Schriever Scott D. , Grentzer Thomas H. , Alapati Satish B.
Published: January 2010

Abstract –  The objective of this study was to compare the impact energy absorption of three mouthguard materials in three environments. Thirty specimens with 12.7 cm × 12.7 cm × 4 mm dimensions were prepared for each material: ethylene vinyl acetate (EVA, T&S Dental and Plastics), Pro‐form™ (Dental Resources Inc), and PolyShok™ (Sportsguard Laboratories). Ten specimens of each material were conditioned for 1 h at 37°C in three environments: dry (ambient) condition, deionized water and artificial saliva. Specimens were impacted at 20 mph by a 0.5‐inch diameter indenter containing a force transducer (Dynatup Model 9250 HV, Instron Corp), based upon ASTM Standard D3763. Energy absorption was determined from the area under the force–time curve during impact (approximately 5 or 7 ms depending on the material). Groups were compared using anova and the Tukey test. Energy absorption values, normalized to specimen thickness (mean ± SD in J mm−1), were: (i) Dry: EVA 4.73 ± 0.27, Pro‐form™ 3.55 ± 0.25, PolyShok™ 6.32 ± 0.24; (ii) DI water: EVA 4.82 ± 0.40, Pro‐form™ 3.78 ± 0.33, PolyShok™ 5.87 ± 0.38; (iii) Artificial saliva: EVA 5.63 ± 0.49, Pro‐form™ 4.01 ± 0.54, PolyShok™ 6.37 ± 0.55. PolyShok™ was the most energy‐absorbent material in all three environments. EVA was significantly more impact resistant than Pro‐form™ in all three environments. EVA and Pro‐form™ performed significantly better after saliva conditioning than dry or water conditioned, but PolyShok™ did not show any difference in energy absorption when conditioned in any of the three environments. Characteristic deformation patterns from impact loading were observed with an SEM for each material. The superior energy absorption for PolyShok™ is attributed to the polyurethane additive.
The Divine Attributes
Authors: Everitt Nicholas
Published: January 2010

Focusing on God’s essential attributes of omnipotence, omniscience, being eternal and omnipresent, being a creator and sustainer, and being a person, I examine how far recent discussion has been able to provide for each of these divine attributes a consistent interpretation. I also consider briefly whether the attributes are compatible with each other.
Response Analysis of a General Asymmetric Rotor-Bearing System
Authors: Inagaki T. , Kanki H. , Shiraki K.
Published: January 2010

This paper presents an analytical method for the evaluation of the synchronous response of a general asymmetric rotor-bearing system. In the analysis, slightly asymmetric shaft stiffness in bending and shearing, which distribute along the rotor, and asymmetric transverse mass moment of inertia are considered. The dynamic properties of bearings and pedestals are assumed to be anisotropic and coupled in each direction. The equations of motion with periodic time dependent coefficients are solved by the Harmonic Balance Method and formulated to the transfer matrix. These solutions include the “Modified Holzer-Myklestad-Prohl Method by Lund & Orcutt” as a special case. The results of the analysis are confirmed by a simple model test and field measurements of large turbosets.
Criteria of Force Transmission for Linkages and Their Application for Synthesis
Authors: Litvin F. L.
Published: January 2010

A method is developed for the determination of force transmission criteria for spatial linkages of any structure. It is applied to a mechanism with seven links, to five-link RCRCR and RRSRR mechanisms, and four-link RCCC mechanisms. In addition there are presented (a) a mathematical indication of “dead positions”, (b) a means of bringing the synthesis solution into the space of those parameters for which a real mechanism may exist; (c) a means for the optimal synthesis of a mechanism with regard to favorable conditions of force transmission.
Shock Spectrum Ratios Applied to the Comparison of Pulse Signatures
Authors: Houghton J. R.
Published: January 2010

Two extensions of the shock spectrum technique are developed for use in pulse signature analysis. A shock spectrum ratio is proposed and compared to the Fourier transfer function for the detection of small perturbations on a larger pulse shape. The shock spectrum ratio is shown to have good sensitivity to the relative size of the perturbation. The shock spectrum ratio approach is extended to a new type of spectrum named “slot transform.” This specialized transform is shown to have several advantages with respect to the Fourier transform in the development of magnitude transfer functions. The transform was developed for analysis of digitized acoustic emission pulses where a rectangular time window is preferred. These two extensions of shock spectrum methods are tested on experimental data from high g shock tests and acoustic emission measurements from damaged and undamaged ball bearings. Deconvolution of the acoustic emission data was necessary before the shork spectrum, ratio was capable of indicating the relative damage of the bearings.
Time Domain Analysis of Machinery Vibration Signals Using Digital Techniques
Authors: Xistris G. D. , Boast G. K. , Sankar T. S.
Published: January 2010

The design and implementation of a general purpose processing system to analyze machinery vibration signals in the time domain are presented. The system comprises a data acquisition stage, where analog signals having a maximum frequency content up to 4 kHz and a dynamic range up to 72 dB, are converted into digital form and a processing stage, where modular software algorithms are employed to perform specific operations in an interactive environment. Processing capabilities encompass scaling, integration and the computation of statistical parameters such as means, RMS, standard deviation, maximum and minimum values. The input signal dynamic range and maximum frequency content are shown to be the governing criteria in the design and performance of the analysis system. The influence of hardware precision level and sampling rate on the overall accuracy of the obtained results is illustrated by digitizing standard waveforms under different processing parameters. Extraneous components introduced at the digitization and integration stages are identified and eliminated by employing a versatile digital filter algorithm. The performance of the system in processing acceleration signals from a 3 HP, 14000 RPM internal combustion engine is demonstrated and the different application aspects of such a facility in the machinery maintenance field are outlined.
Mechanical Reliability of Blood Sampling Tubes—Closure and Needle Forces Versus Pullout Risk
Authors: Percarpio E. P.
Published: January 2010

Mechanical factors relating to the operational reliability of blood-sampling tubes are discussed. A calculation procedure to determine the risk of premature closure pullout owing to excessive needle withdrawal force is given. Effects of closure/tube/process changes are discussed, and details of test parameters are given.
Chain Saw Kickback Dynamics
Authors: Koebke R. H.
Published: January 2010

An operational hazard of chain saws is the so called kickback phenomenon, a sudden difficult to control rearward and upward reaction of the saw. Kickback can occur when the saw chain on the top quadrant of the bar nose makes initial contact with an obstruction. In the present work some features of chain saw kickback are developed by consideration momentum principles and a certain kinematical assumption.
On a New Type of Vibrating Lift
Authors: Inoue J. , Araki Y. , Kubo S.
Published: January 2010

This paper investigates in detail the new vibrating lift made by utilizing the principle of the self-synchronization of mechanical vibrators. In a general way products ride up inclined way of the spiral trough of a vibrating lift, propelled by forces generated by two unbalanced rotors connected by the gear and driven by a motor, which are mounted on top of the structure in a horizontal position. This machine is a new type of vibrating lift. The axes of two unbalanced rotors are nonparallel and each driven by two asynchronous motors. One motor is positioned on the right hand side and the other is situated on the left hand side of the structure in a vertical position. In spite of the absence of any connection between two rotors, they rotate at the same speed and have the definite phase angle between them as the result of the phenomena of the self-synchronization under a certain condition. This phenomenon is also called entrainment. Accordingly, by the linear vibration in the direction of the axis of the structure and rotational vibration about the axis of the structure by two unbalanced rotors, products ride up inclined way of the spiral trough.
Normal Mode Uncoupling of Systems with Time Varying Stiffness
Authors: Benton M. , Seireg A.
Published: January 2010

This paper investigates the conditions for transforming coupled systems with time-varying stiffness to normal mode coordinates. The stability regions are determined from the normal mode equations and the effect of model damping on the width of these regions is investigated. An approximate method for uncoupling is also presented which can be used to give good practical solutions in situations where the theoretical necessary conditions are not met. The proposed method can provide a simple and effective tool for the analysis of parametric vibrations for systems with any number of degrees of freedom as in the case of high speed gear trains.
The Application of the Ritz Averaging Method to Determining the Response of Systems with Time Varying Stiffness to Harmonic Excitation
Authors: Benton M. , Seireg A.
Published: January 2010

Parametric vibrations occur in many mechanical systems such as gears where the stiffness variation and external excitations generally occur at integer multiples of the rotational speed. This paper describes a procedure based on the Ritz Averaging Method for developing closed form solutions for the response of such systems to harmonic excitations. Although the method is illustrated in the paper by the case of a linear system with harmonic stiffness fluctuation (defined by Mathieu’s equation) it can be readily applied to determine approximate solutions for systems with nonlinear characteristics and any periodic variations of parameters.
Damping and Hydrodynamic Mass of a Cylinder in Simulated Two-Phase Flow
Authors: Carlucci L. N.
Published: January 2010

This paper describes the results of experiments conducted to determine the damping and hydrodynamic mass characteristics of a fixed-fixed cylinder both in liquid and in simulated two-phase flows. It was observed that damping was significantly higher in two-phase flow than in single phase flow, and that, depending on the flow regime, it exhibited a maximum or maxima at void fractions of 30% to 60%. The hydrodynamic mass was observed to decrease with increasing void fraction but at a higher rate than that of the mixture density.
Relative Motion Between Ski and Boot Under Impact Testing of Ski Bindings
Authors: Diel M. , Mote C. D.
Published: January 2010

The relative translation and rotation of a snow ski and boot under lateral impact of the ski is critical to the function of the ski release binding. The binding couples the ski and ski boot during skiing and releases them under potentially excessive loading of the skier’s leg. A displacement transducer was developed to measure the general, two dimensional translation and rotation of the boot relative to the ski during laboratory impact tests of bindings. The requirement that the boot and ski separate upon release of the binding complicates the transducer design. Lateral impacts were applied with a pendulum at the “ski tip”, at the “ski tail” and at the “boot toe” positions on the ski. The model leg, ankle and ski response were recorded. Significant differences in leg-ski-binding system response were observed with two commercial bindings and with the impact locations on the ski.
Conductive Plastics Methods
Authors: Bradbury E. J. , Bigg D. M.
Published: January 2010

Plastics offer cost, maintenance, and density advantages over metals for many lowstrength applications. Low electrical and thermal conductivities, however, are major deficiencies for some applications. The addition of conductive fillers to the polymer will improve these deficiencies. The two filler parameters which most significantly affect the conductivity of the composite are volume loading and the shape. This paper discusses the effects of various filler types and shapes on the conducitivity of plastics.
A Method of Local Synthesis of Gears Grounded on the Connections Between the Principal and Geodetic Curvatures of Surfaces
Authors: Litvin F. L. , Gutman Y.
Published: January 2010

A spatial gear-mechanism with double curvature tooth surfaces is discussed. The following results are obtained: a) the relationship between the principal curvatures of the surfaces, b) the conditions under which the path of the contact point on the surface is a geodetic line in the local sense. A method of synthesis of mismatched gearing proposed here permits determination of optimal conditions of meshing in the vicinity of the main contact point.
Simulation of Hertzian Contacts Found in Spur Gears with a High Performance Disk Machine
Authors: Flamand L. , Berthe D. , Godet M.
Published: January 2010

A high performance disk machine capable of simulating both radii of curvature, rolling and sliding speeds of spur gears was built. The simulation program was conducted using both a gear rig and a disk machine. The point chosen for simulation is situated just below the pitch circle. The geometric and dynamic conditions at that point were reproduced. The damage observed in both cases for three different metallurgies and one loading program is presented. Qualitative results are most encouraging. Identical forms of damage are observed when, the mechanical parameters which define the contact condition (CMD), the gear and disk material, and the lubricants are the same.
Friction Between High Speed Gear Coupling Teeth
Authors: Calistrat M. M.
Published: January 2010

Under misalignment, the teeth of a coupling hub and sleeve slide over each other axially. This motion and the torque transmission generate friction forces. Although laboratory measurements indicated that the friction coefficients are very low, many a thrust bearing failure was blamed on coupling “lock-up”. This paper discusses the results obtained from an exhaustive test program in which the friction forces were measured as a function of many variables, including torque, axial velocity, misalignment and lubrication. Friction coefficients as large as .16 were computed when the coupling operated under adverse conditions. Lubrication proved to have the largest influence on the magnitude of the friction coefficients.
Calculation of Cylindrical Worm Gear Drives of Different Tooth Profiles
Authors: Winter H. , Wilkesmann H.
Published: January 2010

The formulae of classical hydrodynamics are not suitable for the calculation of load capacity and power loss of worm gear drives. Thus a theoretical basis had to be developed for the comparison of different tooth profiles, materials of worm and worm wheel and lubricants. The data obtained were compared with test results. It proved that the coefficient of friction is an important influence factor.
Methods of Synthesis and Analysis for Hypoid Gear-Drives of “Formate” and “Helixform”—Part 1. Calculations For Machine Settings For Member Gear Manufacture of the Formate and Helixform Hypoid Gears
Authors: Litvin F. L. , Gutman Y.
Published: January 2010

Methods for synthesis and analysis Hypoid gears generated by Helixform and Formabe methods are suggested. The article is a three-part one divided according to the considered stages of synthesis and analysis: (a) the determination of machine settings for the member-gear manufacture (after that tooth surface of the member-gear can be obtained); (b) machine setting calculations for the pinion on the base of the local synthesis for gears with approximate meshing; (c) methods for analysis (in the whole area of meshing) and optional synthesis for the mismatch gearing and its application for Hypoid gears.
On Functionality of a New Mechanical Hand
Authors: Rovetta A.
Published: January 2010

This paper deals with the functionality of a new mechanical hand, able to grasp objects of generic shape. In its morphology it is similar to the human hand; in its functionality it is adaptable as a robot extremity or, with some specific devices, as a prosthesis. This paper examines the mechanical aspects of this mechanism, in order to point out some basic characteristics. Its properties might be considered for a development of its adaptability to multiple functions, in robotics and maybe in orthopaedics.
Writing for “The Audience”
Authors: Cosgrove M. C.
Published: January 2010

Design technology transfer can be greatly facilitated by studying “the audience” expected to receive and act on the information. Before writing begins, knowledge of the audience should influence design of reports in the various choices made concerning technical level, vocabulary, organization, etc. During writing, audience awareness facilitates the writing of simple and direct prose. When writing is completed, it can be checked by reference to several mathematical formulas which will indicate its readability for a given audience.
Rating Gear Strength
Authors: Castellani G. , Castelli V. P.
Published: January 2010

Synthetic formulas are written suitable to represent and compare the AGMA and ISO Standards for rating gear tooth strength. The corresponding tooth form and stress correction factors are compared for different kinds of involute gear teeth. A unified procedure is given to enable computing of the root parameters for teeth generated by any kind of tool which completes the ISO method, extending it to the case of shaped teeth. Both AGMA and ISO methods are also applied to the calculation of the aforesaid factors for internal gear teeth. In this case reliability is checked by finite element method. The comparison shows that research is necessary to review some items relating to calculation of stress correction factors.
Design Sensitivity Analysis of Planar Mechanism and Machine Dynamics
Authors: Haug E. J. , Wehage R. , Barman N. C.
Published: January 2010

A method of formulating and automatically integrating the equations of motion of quite general constrained dynamic systems is presented. Design sensitivity analysis is carried out using a state space adjoint variable method that has been employed extensively in optimal control and structural design optimization. Both dynamic analysis and design sensitivity analysis formulations are automated and numerical solution of state and adjoint differential equations are carried out using a stiff numerical integration method that treats mixed systems of differential and algebraic equations. A computer code that implements the method is applied to two numerical examples. The first example concerns a relatively simple slider-crank mechanism. The second example treats a more complex agricultural trip plow that undergoes intermittent motion.
The Workspaces of a Mechanical Manipulator
Authors: Kumar A. , Waldron K. J.
Published: January 2010

A new theory and a resulting algorithm for tracing the bounding surfaces of mechanical manipulator workspaces is presented. The natures of the numerous singular configurations and means of accommodating them within the algorithm are also studied. In order to sort surfaces of interest from the large number of possible solutions, a numerically implementable labelling technique is also presented. The algorithm is applicable to all practicable manipulator configurations with three, or more, degrees of freedom.
Equations for Four-Bar Line-Envelopes
Authors: Hunt K. H. , Fichter E. F.
Published: January 2010

A line-equation (in tangential coordinates) is derived for the envelope of a general straight line attached to the coupler of a planar hinged four-bar linkage. Since a line can be identified with an axis of relative translation parallel to a sliding joint, the study of how lines move in a mechanism has practical potential. Nevertheless the emphasis here is on the geometry of the line-envelopes, and some envelopes are plotted both as samples of what can be obtained and to exemplify some of the properties which they possess. Towards the end of the paper all the other forms of planar four-bar linkage, namely those in which one or two sliding joints replace hinges, are examined, and their envelope-equations are presented.
The Optimization Problem With Optimal Tolerance Assignment and Full Acceptance
Authors: Michael W. , Siddall J. N.
Published: January 2010

The conventional optimization problem, where the nominal values of the design variables are of interest, is extended to include the optimal allocation of manufacturing tolerances. Thus the tolerances are also treated as design variables. The approach is illustrated by an example using a sequence of increasingly generalized formulations. Finally the solution is provided in general mathematical form. This paper limits the model to a production process with 100 percent acceptability. The method appears to offer a practical technique provided a satisfactory cost function can be defined.
The Generalized Coordinate Selection for the Dynamics of Complex Planar Mechanical Systems
Authors: Freeman R. A. , Tesar D.
Published: January 2010

This paper involves the most appropriate selection of the reference parameters (generalized coordinates) to develop the controlling equations for a large class of complex multi-degree of freedom planar mechanical systems. The selection of the reference parameter for the 1 DOF system is shown to be a simple matter since the modeling components can be transferred between reference parameters with a very simple set of equations. For multi-degree of freedom systems, the development of the controlling equations is shown to be direct as long as the structure is made up of two link Assur groups or dyads. The controlling equations remain transparent and therefore are ideal for treating the coupling and design questions for adjustable mechanisms as well as for robotic type systems.
Optimization of Cam-Follower Systems With Kinematic and Dynamic Constraints
Authors: Berzak N.
Published: January 2010

A general method for obtaining the optimum design of a cam-follower system is presented. This method, developed for polynomial output motions which satisfy prescribed terminal conditions, includes performance criteria related to kinematic, as well as dynamic properties of the system. The output motion and the performance coefficients are expressed as functions of independent parameters. Using a linear sum of the weighted performance coefficients, the optimum design is obtained by scanning a suitable family of polynomial output motions. The theory is illustrated by numerical examples for four-term polynomial output motions.
Kinematic Analysis of Plate Cam Profiles Not Analytically Defined
Authors: Di Benedetto A. , Vinciguerra A.
Published: January 2010

The kinematic analysis of the follower of a plate cam with a profile not analytically defined is a matter of practical and theoretical interest. Practical interest is stimulated by the possibility, on the whole, to consider the dynamic services of the mechanism. Theoretical interest is connected to the numerical derivative procedure that is required by the kinematic analysis. Consequently, in this paper a method of approximate calculus is proposed in order to determine velocity, acceleration and jerk values of translating followers by algorithms that are obtained by mathematical induction through Newton’s formulas for repeating integrations. A numerical example given at the conclusion shows the degree of reliability of the proposed method.
Analysis and Synthesis of Mechanical Error in Geneva Mechanisms—A Stochastic Approach. Part 2: Internal Geneva Mechanism
Authors: Rao S. S. , Gavane S. S.
Published: January 2010

Because of error of manufacture and assembly, the output kinematic characteristics of a Geneva mechanism will be different from the desired ones. In this paper an analysis procedure is developed to find the error in acceleration and jerk of internal Geneva mechanisms from the viewpoint of probability theory. A synthesis procedure, using nonlinear programming techniques, of distributing tolerances and clearances in the mechanism for specified maximum allowable errors in acceleration and jerk is discussed. The application of analysis and synthesis procedures is demonstrated by means of numerical examples.
A Mathematical Basis for the Random Decrement Vibration Signature Analysis Technique
Authors: Vandiver J. K. , Dunwoody A. B. , Campbell R. B. , Cook M. F.
Published: January 2010

The mathematical basis for the Random Decrement Technique of vibration signature analysis is established. The general relationship between the autocorrelation function of a random process and the Randomdec signature is derived. For the particular case of a linear time invariant system excited by a zero-mean, stationary, Gaussian random process, a Randomdec signature of the output is shown to be proportional to the auto-correlation of the output. Example Randomdec signatures are computed from acceleration response time histories from an offshore platform.
A Direct Integration Technique for the Transient Analysis of Rotating Shafts
Authors: Chu F. H. , Pilkey W. D.
Published: January 2010

The continuous space discrete time Riccati transfer matrix method is a new direct integration technique for transient analysis of structural members. This method is applied to rotating shafts with bearing systems containing masses. Numerical results are given for a rotor with isotropic bearings.
Finite Journal Bearing With Nonlinear Stiffness and Damping. Part 1: Improved Mathematical Models
Authors: Hashish E. , Sankar T. S. , Osman M. O. M.
Published: January 2010

Two mathematical models for the nonlinear hydrodynamic film forces in a finite bearing are developed including a practical adaptation of the cavitation phenomenon. Using the linearity of the Reynolds equation for incompressible film, the pressure components are effectively decomposed and the Reynolds equation is rearranged for general solution by a finite element program in which only the L/d ratio and the eccentricity ratio are to be specified. The different possibilities of partial film profile location in a general dynamic case are demonstrated. The two partial film models possess the required accuracy of the finite bearing approach with the simplicity of the known long and short bearing approximations which are shown as the upper and lower bounds for the present case. The finite bearing approach presented are particularly suitable for nonlinear dynamic analysis.
A Note on Critical-Speed Solutions for Finite-Element-Based Rotor Models
Authors: Childs D. W. , Graviss K.
Published: January 2010

An ordering scheme is introduced for the deflection variables in finite-element-based rotordynamics models which permits a direct numerical solution approach via symmetric matrix procedures for rotor critical speeds, providing the system stiffness matrix is symmetric. Previously published reports on finite-element formulations employ general Q-R algorithms operating on state-variable forms of the governing equations to obtain rotor natural frequencies at a specified running speed, with critical speeds determined from many such calculations.
Motion Simulation of an Articulated Robotic Arm Subjected to Static Forces
Authors: Patwardhan A. G. , Soni A. H.
Published: January 2010

A three-dimensional motion simulation model of an open-loop kinematically constrained mechanical system is developed to simulate the motion response of a robotic arm to externally applied static loads. The general system consists of N rigid bodies connected together by (N-1) kinematic pairs. The class and type of kinematic pairs may be selected from a set of twelve physically realizable kinematic pairs. Six equations of force equilibrium are written for an ith body. A variational method is used to linearize these equations for incremental values of displacement and to incorporate the generalized parameters of the kinematic pairs and characteristics of the internal driving forces. Five applications of the proposed simulation model are discussed.
Stress Sources and Critical Stress Combinations for Splined Shaft
Authors: Volfson B. P.
Published: January 2010

It is shown that there are three critical combinations of loads for a splined shaft tooth. For each combination, the possibility exists that three types of cracks may occur: transverse, inclined, and longitudinal. They are studied in this paper. As distinct from known approaches, when two stress factors are assumed to cause splined shaft fracture, the author considers five stress factors: shearing torsion stress, stress caused by contact force from torsion, normal bending stress, shearing bending stress, stress caused by contact force from bending.
Thermal Buckling of Initially Stressed Thick Plates
Authors: Chen Lien-Wen , Brunelle E. J. , Chen L. Y.
Published: January 2010

Equations of motion for a transversely isotropic thick plate with thermal effects in a general state of nonuniform initial stress where the effects of transverse shear and rotary inertia are included are derived. The method is to perturb the nonlinear equations of elasticity by an incremental deformation. The resulting equations are linearized and integrated through the thickness of the plate to obtain the thermal elastic plate equations. A reduced set of equations for a thick plate with thermal effects is also given. Finally, the thermal buckling problems are solved for a simply supported rectangular plate in a state of uniform compressive (or tensile) initial stress plus initial bending stress combined with uniform thermal compressive stress plus thermal bending stress. The effects of various parameters on thermal buckling loads are studied.
A Weibull Analysis of Wood Member Bending Strength
Authors: Liu J. Y.
Published: January 2010

The analysis of size effect on bending strength of rectangular wood beams based on Weibull’s theory of brittle failure has been expanded here to include tapered wood beams under arbitrary loading conditions. The mathematical formulations are expressed in terms of the two parameters in Weibull’s model. These parameters must be determined experimentally for each wood species. Numerical data for Douglas-fir beams are presented in graph form, where necessary, for easy application by the design engineer. Design procedures are demonstrated by numerical examples.
A Statistical Model for Estimation of Upper Tail Probabilities
Authors: Dargahi-Noubary G. R.
Published: January 2010

A relation is set up between the upper and lower tail probabilities for certain pairs of distributions. Using this and results presented in Wirsching, [3], a statistical model is obtained for estimation of upper tail probabilities.
Minimum Weight Design of a Car Trunk Deck-Lid Subject to Overall Stiffness Constraints
Authors: Du H. A. , Tang S. C.
Published: January 2010

A design procedure for a car trunk deck-lid using an approximate optimization technique is presented. Selecting the deck-lid gages and deck-lid inner panel configuration as design variables and overall stiffnesses as constraints, a possible weight reduction of 20 percent is demonstrated, compared with the base production deck-lid design. Although other practical design constraints might not allow one to achieve this goal, the potential value of optimization techniques is clearly demonstrated by this study. It is concluded that it could be useful to develop and apply such a procedure to components such as hoods, deck-lids, doors, and fenders, which are isolatable as structural components.
A Variational Formulation for the Dynamic Viscoelastic Finite Element Analysis of Robotic Manipulators Constructed from Composite Materials
Authors: Thompson B. S. , Sung C. K.
Published: January 2010

The operating speed and endpoint positional accuracy of existing industrial manipulators are limited by the inertial and stiffness characteristics of the articulating members of the robot’s mechanical linkage. This limitation may be overcome by developing members having high structural stiffness and strength with low mass, and this has been recognized for some time. These characteristics can be obtained by fabricating the moving members of manipulators in fiber-reinforced composite materials. In order to establish a basis for the dynamic analysis of robots fabricated in viscoelastic composites, a variational theorem is developed herein. A preliminary comparative study is then undertaken for manipulators manufactured in a graphite-epoxy composite material and also steel in order to demonstrate some of the advantages to be accrued from this proposed new design philosophy such as smaller deflections at the end-effector.