bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitochondrial nucleoids maintain genetic autonomy but allow for functional complementation
Authors: Gilkerson Robert W. , Schon Eric A. , Hernandez Evelyn , Davidson Mercy M.
Published: June 2008

Mitochondrial DNA (mtDNA) is packaged into DNA-protein assemblies called nucleoids, but the mode of mtDNA propagation via the nucleoid remains controversial. Two mechanisms have been proposed: nucleoids may consistently maintain their mtDNA content faithfully, or nucleoids may exchange mtDNAs dynamically. To test these models directly, two cell lines were fused, each homoplasmic for a partially deleted mtDNA in which the deletions were nonoverlapping and each deficient in mitochondrial protein synthesis, thus allowing the first unequivocal visualization of two mtDNAs at the nucleoid level. The two mtDNAs transcomplemented to restore mitochondrial protein synthesis but were consistently maintained in discrete nucleoids that did not intermix stably. These results indicate that mitochondrial nucleoids tightly regulate their genetic content rather than freely exchanging mtDNAs. This genetic autonomy provides a molecular mechanism to explain patterns of mitochondrial genetic inheritance, in addition to facilitating therapeutic methods to eliminate deleterious mtDNA mutations.
Both daughter cells traffic and exocytose membrane at the cleavage furrow during mammalian cytokinesis
Authors: Goss John W. , Toomre Derek K.
Published: June 2008

Membrane trafficking during cytokinesis is not well understood. We used advanced live cell imaging techniques to track exocytosis of single vesicles to determine whether constitutively exocytosed membrane is focally delivered to the cleavage furrow. Ultrasensitive three-dimensional confocal time-lapse imaging of the temperature-sensitive membrane cargo protein vesicular stomatitis virus protein–yellow fluorescent protein revealed that vesicles from both daughter cells traffic out of the Golgi and into the furrow, following curvilinear paths. Immunolocalization and photobleaching experiments indicate that individual vesicles accumulate at the midbody and generate a reserve vesicle pool that is distinct from endosomal and lysosomal compartments. Total internal reflection fluorescence microscopy imaging provided direct evidence that Golgi-derived vesicles from both daughter cells not only traffic to the furrow region but dock and fuse there, supporting a symmetrically polarized exocytic delivery model. In contrast, quantitative analysis of midbody abscission showed inheritance of the midbody remnant by one daughter cell, indicating that cytokinesis is composed of both symmetrical and asymmetrical stages.
Oxford Journals' adventures in open access
Authors: BIRD Claire
Published: June 2008

In 2004, Oxford Journals began experimenting with an ‘author‐side payment’ open access model for its flagship molecular biology journal, Nucleic Acids Research (NAR). Since then, around 70 of its approximately 200 journals have adopted an open access model of some kind, providing a unique perspective on the practicalities involved and the potential impact of open access on established academic journals. Under NAR's full open access model, submissions and author satisfaction remain encouragingly stable, and most NAR authors are paying the open access charges. NAR's income per article declined in 2005, but increased once more in 2007. The journal remains financially viable under the new model. Uptake of the optional ‘Oxford Open’ model varies by discipline. It is highest in the life sciences: in the region of 17–25% for some molecular and computational biology journals. It is too soon to tell whether the ‘Oxford Open’ model will have an impact on subscriptions, usage, and citations, but further research is under way.
Author perceptions of journal quality
Authors: REGAZZI John J. , AYTAC Selenay
Published: June 2008

One of the most important issues facing scholarly communication today is what constitutes quality in the publishing and dissemination of research findings; the aim of this exploratory research study was to investigate author‐perceived quality characteristics of science, technology and medicine journals. We triangulated data from a small number of volunteer full‐time faculty members of Long Island University, using three different research techniques: (1) questionnaire survey, (2) focus groups, and (3) semi‐structured face‐to‐face interviews. The study identified some significant differences by discipline, gender, and tenure status. Overall, the three most important attributes were the reputation of the journal, the estimated length of time to article publication, and the readership of the journal. Our findings bring new insight into this area for the scholarly research community as a whole.
Giving new life to out‐of‐print books: when publishers' and libraries' interests meet
Authors: VANDOOREN Françoise , GASS Cécile
Published: June 2008

The Library of the Université Libre de Bruxelles and Editions de l'Université de Bruxelles (EUB), the University's publishing imprint, have recently agreed to collaborate to provide free online access to recent out‐of‐print books published by EUB. The e‐books are available on the Digithèque website, a collection of digital copies of printed books created by the Library. This initiative is valuable for the scientific community and the general public who can freely access the books online, for the authors whose books have been digitized and widely disseminated, and for the publisher whose collections become more visible on the Internet, thereby generating more traffic on its website and potentially increasing sales of its other books. Around 20 books have been made available online so far. This article describes the context of the agreement, how the collaboration operates, the options of file conversion vs. book scanning, issues relating to copyright and users' rights, how access is provided to the digital copies, and future collaborative projects of the Library and EUB.
Library systems in the electronic era
Authors: BLEY Robert
Published: June 2008

The ‘traditional’ academic library system model – i.e. a central system constructed around a common catalogue record that also dictated the end‐users' view – is breaking down. Systems that were constructed to handle the processing and lending of printed items are no longer capable, on their own, of dealing with the variety of different information resources handled by modern academic libraries. A great deal has been written about how end‐users expect more ‘Web 2.0’ features than library catalogues currently provide. New front‐end services have been designed by libraries and library system providers to cater for this need. However, not much has been written about the needs of internal library staff who struggle with processing, handling, and supporting the huge volume of electronic resources subscribed to by libraries. Electronic resource management systems have been developed to cater for these needs, and new standards for data interchange with such systems have been developed. Just as standards were important in encouraging electronic data interchange (orders, invoices, claims, etc.) between libraries, publishers, and agents in the last century, so new standards are evolving for such transactions in the electronic era.
Book Reviews
Authors: PETERS Paul
Published: June 2008

Developing Open Access Journals: A Practical Guide David Solomon. Chandos Publishing, 2008. 208 pp. ISBN 978‐1843343400, £57.00, hbk. ISBN 978‐1843343394, £39.95, pbk.
Book Reviews
Authors: OPPENHEIM Charles
Published: June 2008

Scholarship in the Digital Age: Information, Infrastructure and the Internet by Christine Borgman MIT Press, 2007, 335pp. ISBN 978 0 262 02619 8, £22.95, hbk.
PoooL: an efficient method for estimating haplotype frequencies from large DNA pools
Authors: Zhang Han , Yang Hsin-Chou , Yang Yaning
Published: June 2008

Motivation: Pooling DNA is a cost-effective alternative to individual genotyping method. It is often used for initial screening in genome-wide association analysis. In some studies, large pools with sizes up to several hundreds were applied in order to significantly reduce genotyping cost. However, method for estimating haplotype frequencies from large DNA pools has not been available due to computational complexity involved.

Methods: We propose a novel constrained EM algorithm, PoooL, to estimate frequencies of single-nucleotide polymorphism (SNP) haplotypes from DNA pools. A quantity called importance factor is introduced to measure the contribution of a haplotype to the likelihood. Under the assumption of asymptotic normality of the estimated allele frequencies and a system of linear constraints on haplotype frequencies the importance factor remains a constant in the iterative maximization process. The maximization problem in the EM algorithm is then formulated into a constrained maximum entropy model and solved by the improved iterative scaling method.

Results: Simulation study shows that our algorithm can efficiently estimate haplotype frequencies from DNA pools with arbitrarily large sizes. The algorithm works equally well for large pools with sizes up to hundreds or thousands and for pools with sizes as small as one or two individuals. The computational complexity of the PoooL algorithm is independent of pool sizes, and the computational efficiency for large pools is thus substantially improved over existing estimating methods. Simulation results also show that the proposed method is robust to genotype errors and population admixture.

Availability:  http://staff.ustc.edu.cn/~ynyang/poool

Contact:  zhanghan@mail.ustc.edu.cn; ynyang@ustc.edu.cn
Exploring the impact of polyproline II (PII) conformational bias on the binding of peptides to the SEM‐5 SH3 domain
Authors: Whitten Steven T. , Yang Huan‐Wang , Fox Robert O. , Hilser Vincent J.
Published: June 2008

The left‐handed polyproline II helical structure (PII) is observed to be a dominant conformation in the disordered states of protein and small polypeptide chains, even when no prolines are present in the sequence. Recently, in work by Ferreon and Hilser, the energetics associated with Ala and Gly substitutions at a surface exposed proline site were determined calorimetrically by measuring the binding energetics of Sos peptide variants to the C‐terminal Src Homology 3 domain of SEM‐5. The results were interpreted as a significant conformational bias toward the bound conformation (i.e., PII), even when the ligand is unbound. That study was not able to determine, however, whether the conformational bias of the peptides could be explained in terms other than that of a PII preference. Here, we test, using a computer algorithm based on the hard sphere collision (HSC) model, the notion of whether a bias in the unbound states of the peptide ligands is specific for the PII conformation, or if a bias to any other region of (φ, ψ) space can also result in the same observed binding energetics. The results of these computer simulations indicate that, of the regions of (φ, ψ) modeled for bias in the small peptides, only the bias to the PII conformation, and at rates of bias similar to the experimentally observed rates, quantitatively reproduced the experimental binding energetics.
Hyperbaric oxygen therapy for radiation‐induced hemorrhagic cystitis
Authors: Yoshida Takahiro , Kawashima Atsunari , Ujike Takeshi , Uemura Motohide , Nishimura Kensaku , Miyoshi Susumu
Published: June 2008

Abstract:  Hyperbaric oxygen (HBO) therapy has recently emerged as a potential primary option for the management of hemorrhagic cystitis. We review our experience treating hemorrhagic cystitis with HBO. Between January 2001 and May 2007, eight patients with radiation‐induced hemorrhagic cystitis underwent HBO therapy. There were five men and three women with a mean age of 64.3 years (47–73). Radiation was given for local disease, and the mean dosage delivered was 56.6 Gy (42–70). The mean duration between the onset of hematuria and the beginning of HBO therapy was 8.9 months (3–34). Mean follow‐up period was 15.5 months (2–31). Hematuria resolved completely in six of the eight patients, one of whom suffered recurrence of hematuria and was treated with HBO until the hematuria resolved again. The response rate was 75%, compatible with the previous reports, and no side‐effects of HBO were noted. HBO treatment should be attempted for radiation‐induced hemorrhagic cystitis.
Number, distribution and concentration of Australian veterinarians in 2006, compared with 1981, 1991 and 2001
Authors: Heath TJ
Published: June 2008

Objective  To determine the number, concentration and distribution of veterinarians working in Australia in 2006, and compare with data from 1981, 1991 and 2001.

Procedure  Data on each veterinarian who was registered, resident and apparently working in each Australian state and territory were obtained from relevant veterinary board lists, entered into an Excel spreadsheet and analysed with SAS System for Windows 8. Other data were obtained from the Official Australian Postcode Map, and the Australian Bureau of Statistics.

Results  A total of 7510 veterinarians, of whom 46% were female, were working in Australia in 2006. The rate of increase (230/year) between 2001 and 2006 was greater than for the previous 20 years. The number per million people (360) was 73% higher than in 1981, and more than 30% higher than in the USA and UK. With the establishment of three new veterinary schools the number of graduates, and the total number of veterinarians, will increase further. By 2011 the number of veterinarians is likely to be three‐fold greater, and the number per million people two‐fold greater than in 1981. The number of veterinarians per million dogs and cats will increase at a greater rate if dog and cat numbers continue to fall. As more than 75% of Australian veterinary work involves dogs and cats this has serious implications for the profession.

Conclusions  Progressively increasing numbers of veterinarians will compete for a constant or diminishing resource – the dogs and cats of Australia. It seems likely that overt signs of oversupply will appear before sufficient numbers of veterinarians enter alternative forms of employment.
Surgical treatment of uterine torsion using a ventral midline laparotomy in 19 mares
Authors: Jung C , Hospes R , Bostedt H , Litzke LF
Published: June 2008

Objective  To report on the outcome of surgical treatment of uterine torsion in preterm mares.

Design  Retrospective case series of pregnant mares with uterine torsion presented to the Clinic for Obstetrics, Gynaecology and Andrology of Large and Small Animals.

Methods  Hospital records of all pregnant mares that underwent ventral midline laparotomy for uterine torsion between 1998 and 2004 were reviewed. The signalment, history, clinical signs, results of diagnostic procedures, direction and degree of the uterine twist, treatment and outcome were retrieved from each case record.

Results  This study comprised 19 mares between months 5 and 11 of pregnancy (8.7 ± 1.9) and suffering from uterine torsion. In all cases ventromedian laparotomy was carried out under general anaesthesia. Gastrointestinal disorders were also present in 52.6% of horses. Postoperative complications included subcutaneous seromas (five mares), peritonitis (one mare) and abortion (two mares). In four mares (21%) the operation was unsuccessful (i.e. these mares had to be euthanased intra‐ or postoperatively). Of the surviving 15 mares, 13 (86.6%) gave birth to viable foals at full term. The foals developed normally. Only two mares aborted.

Conclusions  Because of its versatility the ventral midline approach should be considered for correction of uterine torsion. The approach has many advantages, including rapid and clear access to the abdominal cavity, safety, visual assessment of uterine wall viability, correction of concomitant gastrointestinal tract problems, and performance of hysterotomy or hysterectomy, if indicated. In this study, managing uterine torsion in this way resulted in a high percentage of cases (86.6%) in which pregnancy was maintained, with the birth of a viable, mature foal.
Spalling Fatigue Life Assessment of Surface Hardened Sintered Gears Based on Fracture Mechanics
Authors: Ohue Yuji , Yoshida Akira , Seki Masanori
Published: June 2008

In order to evaluate the surface durability of surface-hardened sintered gears, the fatigue lives of 5 kinds of sintered gears and 28 kinds of sintered rollers under sliding-rolling contact conditions were examined and estimated based on the fracture mechanics. The sintered gears and rollers were surface-hardened by induction-hardening and ion-nitriding. The fatigue tests were conducted using a power circulating gear testing machine and two cylinder testing machines. The pore distributions included in the sintered materials were observed and were analyzed statistically. The failure mode of the sintered gears and roller was mainly spalling. The stress intensity factor obtained by FEM analysis for the mode II under a condition of Hertzian contact became larger as the crack length became longer. The estimation of fatigue life of the sintered gears and rollers was attempted using the pore distributions and the fracture mechanics. The estimated fatigue lives were almost the same as the tested fatigue ones. Therefore, it could be said that the crack propagation of the sintered gears and rollers depended on the pore size and hardness.
Numerical Simulations of Timing Belt Camshaft Layout: Local and Global Behavior
Authors: Play Daniel , Fritsch Nicolas , Huot Ste´phane , Ayax Eric
Published: June 2008

Mechanical behaviors of power transmission systems have to be defined during preliminary design. Today, numerical simulations replace classical tests. General experimental validation of numerical results obtained with computer softwares was performed before. The design of timing belt camshaft layouts follows the same way. Meshing of timing belt on pulleys is related to local behavior of load transmission while dynamic response of a whole camshaft drive layout is related to global behavior. Because of the complex nature of phenomena that take place in such mechanical systems and due to practical requirements in Design Office concerning limitation of computer times for example, local and global analyses are made separately but results of the local analysis serve as inputs for the second analysis. The purpose of the local analysis is to optimize pulley groove profiles of pulleys in order to insure both smaller dynamic excitations and a larger timing belt fatigue life. Simulations of tooth meshing are made under non-linear FEM study. Tooth meshing is described step by step and both bending of inner timing belt cords and transmission error effects are defined in relation to specific shapes of pulley groove profiles. The quasi-static transmission error constitutes one of input data for global dynamic simulations through specific in-house software DSTD (Dynamic Simulation of Timing Drive). Dynamic loads and dynamic transmission error are obtained in relation with inertia, stiffness and damping of mechanical elements and with timing belt characteristics. Results are discussed in relation with design parameters of camshaft drive layout.
Analysis of Tooth Surface Distress Using AGMA 925 and Numerical Load Distribution Methods
Authors: Piazza Andrea , Bellino Gabriele
Published: June 2008

The AGMA document 925 is an important step toward the standardisation of the present knowledge of the surface distress mechanisms; specifically it provides a careful look onto two important phenomena as scuffing and wear on gears employing a wide set of experimental data provided by literature and AGMA members; but since the load distribution is calculated using simplified methods the obtained results may be limited to gear designs whose load distribution is similar to the one(s) of the test gearset(s) where the above data was collected, i.e. spur gears, mostly accurately designed to scuff and to test lubricants. The work summarizes the different effects of applying the cited document methodology using simplified load distribution and most sophisticated one(s) on classical test gears for lubricants and on helical designs. It is shown that using more sophisticated load distribution methods the results on helical gears may be strongly different with respect of simplified methods and may suggest, in some cases, a design review.
Improvement of the Load Capacity of Carburized Gears Through the Tooth Profile Optimization
Authors: Masuyama Tomoya , Inoue Katsumi , Sato Tetsu
Published: June 2008

Carburization greatly increases the load capacity of gears, while the defects such as oxides and inclusions reduce fatigue strength. Focusing on inclusions, the authors presented a simulation method to compute fatigue strength of carburized gears by specifying the principal defect, which limits gear strength at the lowest. This study applied the simulation method to tooth profile optimization for the purpose of the improvement of load capacity of carburized gears. The profile of corner of the ISO basic rack is optimized to reduce stress concentration at the fillet and increase load capacity. Maximum bending stress of the tooth, which is generated by the optimized basic rack, is thereby decreased 15% in comparison with the standard-profile tooth. Fatigue strength is computed by simulation and the load capacity is increased 12% on average, though the standard deviation of strength is slightly large. Simulation also gives a comparatively wide distribution of principal defects along the fillet; this may cause the similar distribution of tooth breakage position. To confirm simulation results by experiment, a new hob was produced based on optimization. Test gears were cut by this hob, then carburized to have effective case depth recommended by the AGMA. Computed strength and its distribution are evaluated based on fatigue test result.
Do Load Peaks Cause Breakage, Plastic Deformation or Cracks in Case-Hardened Gears?
Authors: Kage R. , Linke H. , Schlecht B.
Published: June 2008

Apart from the continuous load over the lifetime, load peaks are critical for the capacity of a gearing. This article focuses on the maximally bearable load peaks in case-hardened gears. The ISO 6336 calculation guideline assesses the load capacity at a low number of load alternations (N less than 100 to 1000). The criterion is crack initiation. However, industrial experience shows that unallowably high plastic deformation can occur even in case-hardened gears. In some cases the allowable deformation is reached at such low load levels that cracks do not yet occur. In order to investigate these problems and improve the calculation method, the institute of the authors carried out a research project in cooperation with the industrial research association “Forschungsvereinigung Antriebstechnik” (FVA; Frankfurt/Main, Germany). This article sums up the theoretical and practical work and a calculation procedure derived from the results. During the project it became evident that the current guidelines need to be amended. For the experimental analyses materials of varying core hardness were used. In addition, the load capacity was tested for a variety of addendum modifications and tooth root fillet radii. Analysis criteria were: breakage, cracking, and plastic deformation. A universal relationship between deformation limit and crack initiation was found.
Simulating Fatigue Crack Growth in Spiral Bevel Gears Using Computational Fracture Mechanics
Authors: Ural Ani , Wawrzynek Paul A. , Ingraffea Anthony R. , Lewicki David G.
Published: June 2008

Development of practical and accurate numerical tools for evaluating gear performance and life assists in the design of new and better gears. This paper summarizes new results for predicting crack trajectory and fatigue life for a spiral bevel pinion using the parallel finite element method (FEM) and computational fracture mechanics. The predictions presented are based on linear elastic fracture mechanics (LEFM) theories combined with FEM, and incorporating plasticity-induced fatigue crack closure and moving loads. The analyses are carried out using a parallel FEM solver, which calculates stress intensity factors (SIF) using the equivalent domain J-integral method. We show that we can simulate arbitrarily shaped fatigue crack growth in a spiral bevel gear more accurately and efficiently than with a previous boundary element based approach [1] using the parallel FEM along with a better representation of moving loads.
Gear Shaving: Simulation and Technological Studies
Authors: Klocke Fritz , Schro¨der Tobias
Published: June 2008

Due to its high economical efficiency, the gear shaving process is a widely-used process for soft finishing of gears in the gear manufacturing industry. The wear of the gear shaving tools in industrial practice is determined by the quality of the workpiece which can be achieved with a tool. After the tolerance limits of the gear quality are exceeded, the tool is considered to be worn and must be reground. So far, it has not been studied, what exactly causes the decrease in gear quality and what a worn shaving wheel looks like. Due to the technological peculiarities of the gear shaving process, the tool wear can be expected to appear in a very different way as in conventional machining processes with geometrically defined cutting edges. The knowledge of this tool wear is essential in order to find ways to increase the efficiency as well as the process reliability in gear shaving even further. Therefore, this paper explains the technological peculiarities of the gear shaving process by using a numerical process simulation. Furthermore, it shows examples of worn cutting edges in gear shaving and explains the effects of this tool wear on the quality of the shaved gears.
Evaluation of the Effect of Misalignment and Profile Modification in Face Gear Drive by a Finite Element Meshing Simulation
Authors: Barone Sandro , Borgianni Leonardo , Forte Paola
Published: June 2008

Face gear drives have many advantages over other cross axis transmissions especially in high performance applications. The lack of published design experience and design standards make their design difficult. This is mainly due to the complex geometries and to the lack of practical experience. For these reasons face gears have not been used for long. This work is aimed at investigating the behavior of a face gear transmission considering contact path under load, load sharing and stresses, for an unmodified gear set including shaft misalignment and modification on pinion profile. The investigation is carried out by integrating a 3D CAD system and a FEA code, and by simulating the meshing of pinion and gear sectors with three teeth, using contact elements and an automated contact algorithm. The procedures followed to create the 3D models of teeth in mesh are described and finite element analysis results discussed showing the differences between unmodified, modified and misaligned teeth. Results show the influence of load on theoretically calculated contact paths, contact areas, contact length and load sharing. The differences with respect to the ideal case are sometimes remarkable. Further developments are discussed.
Stress Analysis of Face Gear Tooth Subject to Distributed Load Using Global Local Finite Element Method (GLFEM)
Authors: Moriwaki Ichiro , Ogaya Syunpei , Watanabe Koji
Published: June 2008

The present paper describes a stress analysis of a face gear tooth subject to a distributed load. The distributed load was determined from an initial mismatch between meshing tooth flanks through geometrical analysis. A new global local finite element method was used for the analysis. In the global local finite element method, an analytical domain is divided into two parts; a global domain in which fields are defined by an analytical solution derived from a classical elastic theory, and a local domain in which fields defined by a finite element solution. Furthermore, tooth flank film elements, which enable boundary conditions on tooth flanks to be easily represented, are taken as the global domain. The calculations were performed for face gear pairs with various misalignments. Crowning modifications along lead were given to pinions, and the effect of the modifications on tooth stress distribution in a face gear tooth was discussed. As a result, both contact and bending stresses were not so large. When there are some misalignments, only contact stress increased. However, the crowning on a pinion tooth was effective for the reduction of the contact stress. Furthermore, face gear with linear profiles; i.e., approximated profiles, were also discussed. Then, it was confirmed that this profile is good approximation.
Simulation of Torsional Vibrations or Multibody Simulation: Which Technique Does the Wind Power Industry Need for Solving the Present-Day Problems?
Authors: Schlecht Berthold , Schulze Tobias , Demtro¨der Jens
Published: June 2008

For the simulation of service loads and of their effect on the whole turbine the wind turbine manufacturers use program systems whose particular strengths lie in the wind load simulation at the rotor, in the rotor dynamics as well as in the control-technological operation of the whole turbine. The complex dynamic behavior of the drive train, consisting of the rotor, the rotor shaft, the main gearbox, the brake, the coupling and the generator, is represented as a two-mass oscillator. This simplification, which certainly is necessary within the framework of the wind load simulation programs, is by no means sufficient for the exact description of the dynamics of the more and more complex drive trains with capacities up to 5 MW. At first, the extension to a multimass torsional vibration model seems to be useful for the exact determination of the torsional vibrations in the drive train. However, in the turbines of all manufacturers there have been found forms of damage on drive train components (high axial loads in bearings, high coupling loads, radial loads on generator bearings) that cannot be explained even on the basis of a torsional vibration analysis. Moreover, in measurements on drive trains natural frequencies in the signals occurred that can no longer be explained by the torsional vibration behavior alone. Consequently, a real multibody simulation becomes necessary, for which also radial and axial vibrations can be taken into account, in addition to torsion, since these influence the torsional vibration behavior considerably. These dependences become already clear in an analysis of natural frequencies. This is illustrated by the example of a 700-kW turbine as well as by a planetary gearing for a 3-MW turbine. Especially in the dimensioning of the off-shore turbines with several MW output power, which are being planned, the use of multibody simulation will be advantageous, since the testing of turbine prototypes of this order of magnitude under the corresponding operating conditions are surely more cost-intensive and risky than the virtual testing with well validated simulation models.
The Traveling Chain Transmission: A Novel Two-Speed Chain Drive
Authors: Bucknor Norman R. , Vahabzadeh Hamid
Published: June 2008

In an automatic transmission with planetary gearsets, several clutches are generally required to manage the speed-ratio transitions. Parasitic losses due to open clutches and the transmission pump reduce net transmission efficiency and negatively impact overall vehicle fuel economy. A novel dual-speed drive that does not require clutches to achieve a speed-ratio change has been devised as an alternative to the planetary gearset. In this paper we describe the basic drive concept and the design and testing of two prototypes that was undertaken at the General Motors R&D Center.
Product Model for Gear Units
Authors: Hoehn B.-R. , Steingroever K. , Jaros M.
Published: June 2008

During the last years it has become more and more common practice in the gear industry to exchange gear data electronically between the different parties. Up to now the format of the gear data is usually DXF, IGES or a company-specific format. A common format, which includes not only geometry data, but also load capacity and other gear-related data, was not available. Therefore a product model for gear units was developed at the FZG (Forschungsstelle fuer Zahnraeder und Getriebebau). The main goal was the realization of the data exchange between gear calculation programs, CAD-systems and a central storage of all gear data. This product model covers all kinds of gear data like gear geometry, load capacity data, lubricant data, manufacturing data, etc.. The product model for gear units is based on the application protocol AP 214 of ISO 10303 STEP. This application protocol was originally created to describe the design process of the automotive industry and does not have a sufficient definition of gear data. An extension of an existing application protocol causes time consumptive normative procedures. Therefore the structure of the product model for gear units is independent from ISO 1030-214. It consists of a mechanism, which defines a data structure acc. to ISO 10303-214, but adapted to the product model for gear units. The product model gives a description how to use ISO 10303-214 for the application of gear units. Meanwhile this product model for gear units is published as a VDMA-paper and therefore open to the public. The first successful application is the data exchange between gearcalculation programs of the FVA and CAD-systems. By this new format the data exchange of gear data is now extremely simplified.
An Intelligent Design System for Agile Design and Manufacturing of Mechanical Transmission Systems
Authors: Aziz El-Sayed , Chassapis C.
Published: June 2008

Product development is a process with complicated procedures, which incorporate many aspects of knowledge, experience and teamwork. Specifically, mechanical system design requires an iterative process to determine the desired component design parameters that would satisfy kinematic, performance and manufacturability requirements, which would result in an efficient and reliable operation of speed reduction units. This article describes an approach towards the development of intelligent design support environments for mechanical transmission systems, along with implementation details of a distributed knowledge-based gearing design and manufacturing system that is deployed over the Internet. The system embodies the various tasks of the design process, with modules that address: performance evaluation, process optimization, manufacturability analysis, and provides reasoning and decision-making capabilities for reducing the time between gear tooth creation, detailed design and final production. This methodology is highly desirable in that it is able to simulate real working conditions, evaluate and optimize the design effectively, prevent designers from time-consuming iterations and reduce long and expensive test phases. In an application example relating to process design of a forged gearing system, once a successful power rating is achieved within the design environment through FEA based techniques, the system automatically feeds input parameters into the manufacturing module which carries out all process design and planning stages. Estimation of the number of preforming stages, generation of detail die drawings, and forging load and energy requirements are calculated based on available material design databases, knowledge-based rules and feature-level calculations. Utilization of the World Wide Web, as a medium for the implementation of gear design and its agile manufacturing over the Internet is also being demonstrated. A combination of HTML, JavaScript, VRML, CGI Script and C++ based procedures is used to bring this capability to users distributed anywhere in the world. With the above developments, the problems of experience and expertise for the designers are overcome and unexpected design iterations that cause wastage of engineering time and effort, are avoided. The environment can be easily enhanced with other types of gearing systems.
Gear-Cutting Method of Parallel Depth Hypoid Gears
Authors: Homma Akira , Hirokawa Sumio , Yamamoto Akira
Published: June 2008

The purpose of this study is to develop a gear-cutting method of hypoid gears to achieve a good tooth bearing and good performance for practical use. In this report, the authors propose a new cutting method of parallel depth hypoid gears, which mesh with each other at one point keeping a constant angular velocity ratio, and describe the theory for the gear-cutting method. Next, the theory of the trace of the point contact mark is shown. One of the features of this method is that the designer can control the trace of the point contact mark on the tooth surface as desired. The third, the theory of the ellipse of tooth bearing is shown minutely. In order to confirm the validity of the method, some hypoid gears were designed and manufactured, and ellipse of tooth bearing on red lead corresponded to those of the theory.
Mesh Phasing Relationships in Planetary and Epicyclic Gears
Authors: Parker R. G. , Lin J.
Published: June 2008

Planetary and epicyclic gears (Figure 1) rely on symmetry to achieve the large torque-weight ratios and compactness that make them widely used in multiple applications. A desirable design objective is to divide the load equally such that the multiple sun-planet tooth meshes carry nearly equal load with the same load equality for the ring-planet tooth meshes. To achieve this, one seeks to have all sun-planet meshes be in-phase, that is, each sun-planet mesh nominally has identical mesh conditions (i.e., number of teeth in contact) at all times with similar conditions for the ring-planet meshes. Past research has shown, however, that differing mesh phasing between the sun-planet (and consequently ring-planet) meshes has powerful impact on the dynamic response and can have significant benefits in reducing vibration and noise [1–4]. In essence, designers have a variety of options and objectives in choosing the mesh phasing for a given application, and a clear understanding of the relations governing the mesh phasing is essential.
Development and Application of an Automatic Design System for Multi-Stage Gear Drives
Authors: Bae Inho , Chong Tae Hyong , Kubo Aizoh
Published: June 2008

This paper presents a design algorithm to automate the preliminary design of multi-stage gear drives. Since the design of multi-stage gear drives includes both the dimensional design of gears and the configuration design of the gear train, it is necessary to integrate the design processes in a formalized algorithm in consideration of the highly coupled nature of them. The proposed algorithm begins with splitting gear ratio and dimensional design of the gear pairs on the criteria of strength and durability. Then, it proceeds with a configuration design to position gear drive elements in an available space while minimizing gearbox size and satisfying spatial constraints. The design algorithm has been validated through the redesign example of a geared motor reduction drive. The design has been carried out for six different types of methods according to the ratio splitting algorithms and objective function formulations. The results have been compared with each other and with the existing design. All the designs showed considerably good results: it takes very short time to obtain a solution and the gearbox size reduced considerably while the amounts of constraints violation converged to negligible level. The proposed design algorithm may be used effectively to reduce time and cost for the practical design of multi-stage gear drives.
Gearbox Systems Dynamic Modelling for Diagnostic Fault Detection
Authors: Bartelmus Walter , Zimroz Radosław
Published: June 2008

The paper deals with mathematical modelling and computer simulation of a gearbox driving system with a double stage gearbox. Mathematical modelling and computer simulations are used for supporting diagnostic inference. Vibration is thought of as a signal of gear condition. It is stressed that vibration generated by gears is influenced by many factors. These factors are divided into four groups: design, production technology, operational, condition change. The condition change of a gearbox is given by gear faults that are divided into single faults such as a tooth crack or breakage or distributed faults as pitting, scuffing, and erosion. The faults are modelled in the case of a crack as a change of tooth stiffness in the case of distributed faults they are given multi-parameter functions. Simulated signals undergo signal analysis by spectrum, cepstrum, time-frequency spectrogram. It has been shown by computer simulation that single and distributed faults are identified by cepstrum. For explicit fault identification time-frequency spectrogram has to be additionally used. The computer simulation results are confirmed by analysis of measured vibration signals received from a gearbox wall/housing. The aim of mathematical modelling and computer simulation, besides finding the relationship between gear condition and vibration signal is in the future to give vibration signals for neural network training.
Kinematics of Meshing Surfaces Using Geometric Algebra
Authors: Miller Scott M.
Published: June 2008

As is well known, analysis of two surfaces in mesh plays a fundamental role in gear theory. In the past, special coordinate systems, vector algebra, or screw theory was used to analyze the kinematics of meshing. The approach here instead relies on geometric algebra, an extension of conventional vector algebra. The elegance of geometric algebra for theoretical developments is demonstrated by examining the so-called “equation of meshing,” which requires that the relative velocity of two bodies at a point of contact be perpendicular to the common surface normal vector. With surprisingly little effort, several alternative forms of the equation of meshing are generated and, subsequently, interpreted geometrically. Via straightforward algebraic manipulations, the results of screw theory and vector algebra are unified. Due to the simplicity with which complex geometric concepts are expressed and manipulated, the effort required to grasp the general three-dimensional meshing of surfaces is minimized.
Surface Damage Caused by Gear Profile Grinding and Their Effects on Flank Load Carrying Capacity
Authors: Klocke Fritz , Schlattmeier Heiko
Published: June 2008

Instances of damage to discontinuous form ground and surface-hardened gears, especially of large scale, have recently increased. This damage may be attributed partly to a faulty grinding process with negative effects on the surface zones and the surface properties. In addition to its high accuracy, discontinuous form grinding is characterized by high material removal because of the line contact between grinding wheel and tooth flank. The efficiency and reliability of the process are affected not only by the use of optimized grinding wheel specifications and machining parameters, but also by the risk of local surface zone damage in the form of grinding burn on the tooth flank. The location and onset of local grinding burn damage have seemed for a long time to be random and unpredictable, for which reason the feed rates and material removal rates have been increased only incrementally in procedures used in industrial practice. The studies reported in the paper are intended to contribute to the knowledge of the interrelationships between surface zone damage and the effects on flank load-carrying capacity for the case of profile grinding. Grinding tests have been conducted in order to investigate more closely the occurrence of surface properties in the form of grinding burn as a function of grinding parameters. Further studies of the flank load carrying capacity of case hardened gears subjected to different surface properties are intended to provide a more detailed analysis of the interrelationship between gear geometry and different surface properties during the grinding process in a first step.
Approach for Topological Synthesis of Hyperbolic Gear Drives
Authors: Garci´a-Masia´ Carlos , Pedrero Jose´ I.
Published: June 2008

In this work, new approaches for the dimensional synthesis of both tooth and operating basic surfaces for hyperbolic gear transmissions are presented. Both traditional worm-gearing hyperbolic transmissions (point contact) and non-traditional ones (line contact) are considered regarding constraints as the manufacturing method, the standardized tool modules and the limit normal of contact. For point contact, the location of the pitch point is done by chosen the parameters of the operating basic surfaces (the cone angle of the worm) and of the teeth basic surfaces (axial module and helix angle of the worm). For line contact, the given parameters of the operating basic surfaces are the cone angle and the worm radius at “zero plane”, and the axial module of the teeth basic surfaces. A comparative study of optimal synthesis, considering different solutions of traditional (point contact) hyperbolic transmissions and non-traditional (line contact) ones, is also included. The objective functions were the sliding velocity and the efficiency, and constrictions above were considered.
Contributions to the Study of Generation of the Flanks of the Generating Hook of Cylindrical Curved Gear in Oblong Cycloidal Arc
Authors: Sta˘na˘s¸el Iulian , Mihaila Ioan , Ghionea Adrian
Published: June 2008

The paper has proposed to determine the equation of flanks of generation hook with oblong cycloidal arc taking into account two types of cutting tool: a cutting tool that generates the hole of the tooth, respectively a cutting tool that generates the tooth. The curved cylindrical teeth with cycloidal flanks is generated by rolling with straight mobile line and continuous division by using a milling cutter with 1, 2, 3, 4 or 5 groups of knifes equidistantly placed, fixed on an adaptable device on a Phauter toothing machine. The two curves which defines the flank are simultaneously generated by correlated motions. In order to make the analytical study of motions and geometry of the flanks, several 3D coordinating systems were first defined, each of them being bounded by an element that participates in the generating process. There were established the equations of cutting edged of the tool in Ss system, the equations of the flanks of the generating hook are obtained by changing the reference system of edges of the tool from Ss to SCG. The line of the flanks is studied in the reference plane and in parallel plans with this, and. the profile of the flanks is determined in perpendicular plans on the workpiece axis. . It was made a calculation program in MATLAB, that allowed to obtain data, which were used to plot the line and the profile of the flanks of the generating hook. By analysing the obtained shape they result conclusions used for the manufacturing of the involute-tooth gear with curved oblong cycloidal arc.
Friction and Wear of Surface Modified Stainless Steel Gears and Rollers in High Vacuum
Authors: Fujii Masahiro , Yoshida Akira , Harano Tomoki
Published: June 2008

In this study the authors examined possibility of applying surface modification treatments frequently used under oil lubrication to gears in high vacuum. Friction and wear performance of surface modified spur gears and rollers made of stainless steel was investigated. A spur gear test and a two-cylinder test were carried out under non-lubricating condition in high vacuum to investigate friction and wear behaviors of surface modified gears in vacuum at room temperature. The gear test results were compared with the two-cylinder test results. Sulfurizing treatment, Sn plating with thermal diffusion, three kinds of electroless Ni based alloy platings, and two kinds of composite platings with dispersed particles were employed here. In case of the Ni-P alloy plated gear with dispersed PTFE particles, the wear was almost uniform along the tooth profile and the fluctuation of the dynamic load was small. In cases of the Ni-B alloy plating, the Ni-P-B alloy plating and the Ni-P alloy plating with dispersed BN particles, the wear of the gear pairs was large, while the wear of the rollers was rather small. Though the wear in the two-cylinder test was much smaller than that in the gear test, the average friction coefficients in both the two tests were almost the same with each other.