bluuebunny/crossref_metadata_2025 huggingface dataset:
Caries experience in rural Victorian adolescents
Authors: Soo Y. S. , Morgan M. V.
Published: May 2009

An oral health status survey was conducted on 818 adolescents aged 12 to 16 years in a non‐fluoridated area in rural Victoria. The prevalence and severity of dental caries experience was found to increase with age. The occlusal surface was the predominant surface affected by dental caries for all age groups. Filled surfaces represented the largest component of the DMFS index and were responsible for the increasing dental caries experience with age. Fewer fissure sealants were present with increasing age and second molars were sealed less often than the first molars. Although no difference was evident in the total caries experience between those with and without access to public dental services, a statistical difference was found to exist in unmet need between these two groups. Untreated caries levels were significantly higher in health card holders. The provision of preventive and dental treatment services to this group should be a priority in the future.
Dimensional changes of relined denture bases with heat‐cured, microwave‐activated, autopolymerizing, and visible light‐cured resins. A laboratory study
Authors: Sadamori Shinsuke , Siswomihardjo Widowati , Kameda Koji , Saito Atsushi , Hamada Taizo
Published: May 2009

The dimensional changes of relined denture bases were evaluated in a laboratory study. Heat‐cured resin, two autopolymerizing resins, microwave‐activated resin and a new visible light‐cured resin were used as relining materials in this study. The gaps between the metal die and the relined denture bases were measured immediately after the relining procedure and subsequently on the first day, first week, fourth week, and eighth week. The relined denture bases were stored in distilled water at 37°C between measurements.

It was shown that dimensional changes in relined denture bases were influenced by the relining materials and procedures, and that heat‐cured resin proved to have the smallest dimensional change as well as the greatest dimensional stability in comparison with the other relining materials and procedures.
Dental air turbine handpiece performance testing*
Authors: Dyson J. E. , Darvell B. W.
Published: May 2009

Air turbine handpieces are expected to continue to be widely used as the main means of carrying out dental cutting work and scope exists for further design improvements. An understanding of the theoretical principles governing the performance of these devices seems essential for the systematic development of better handpiece designs and methods of specification. Furthermore, for experimental work on cutting behaviour with air turbine equipment, this knowledge is required for appropriate characterization of the performance of the particular handpiece used with respect to actual rates of energy deposition.

The literature relating to air turbine handpiece performance is critically reviewed to assess currently available methods of measuring important variables such as speed, torque, and power. In this, consideration is given to the current state of knowledge of the influence on these variables of air pressure, flow and turbine design features. It is apparent that, although various measurement methods have been described and data for individual handpieces published, no attempt has yet been made to explore the functional relationships that exist between the variables.

It is concluded that there is a need to identify the factors influencing turbine performance, to develop measurement systems which would provide adequate accuracy and precision and then to investigate the functional relationships between these relevant variables.
The laryngeal mask airway for dental surgery—a review
Authors: Brimacombe J. , Berry A.
Published: May 2009

The ideal airway requirements for oral surgery are the provision of a stable, unobstructed airway, protection of the lungs from aspiration, minimal interference with the surgical field and a low complication rate. Neither the nasal mask nor endotracheal tube meet these requirements. The laryngeal mask airway (LMA), provides a third type of airway for consideration in oral surgery that offers some of the benefits of intubation and avoids many of the associated hazards. It can be inserted without use of a laryngoscope or muscle relaxants, and is designed to produce an airtight seal around the laryngeal inlet. It provides a secure airway suitable for spontaneous or controlled ventilation and acts as an airtight throat pack. Scavenging of waste gases is possible, and it is well tolerated during recovery. A modification, specifically designed for head, neck and dental anaesthesia, has recently become available. The purpose of this article is to provide a brief overview of the LMA with special emphasis on its use in oral surgery.
The effect of cement thickness on the fracture strength of all‐ceramic crowns
Authors: Tuntiprawon Morakot , Wilson Peter R.
Published: May 2009

The effect of increasing cement thickness on the fracture strength of aluminous porcelain jacket crowns was investigated in this study. Thirty‐three aluminous porcelain jacket crowns were divided into three groups. In Group 1, only platinum foil was used to provide cement space. In Group 2 two layers and Group 3 four layers of die spacer were painted onto the metal die before impression taking. Each crown was cemented onto a metal die with zinc phosphate cement and loaded until fracture. The maximum force to break each crown was recorded. The average fracture load was 408 N for Group 1,365 N for Group 2 and 324 N for Group 3. ANOVA (SPSS) found a significant difference (p < 0.05) between groups. A Scheffe Test revealed a significant difference between Groups 1 and 3. It was concluded that increasing the cement thickness above 70 μm reduced the fracture strength of porcelain jacket crowns.
The effect of the Myo device on the gingival health in orthodontic patients
Authors: Flannery G. M. , McCloud P. I. , West V. C.
Published: May 2009

The purpose of the present investigation was to determine the effectiveness of the Myo in reducing plaque and gingivitis development in orthodontic patients using a single‐blind, cross‐over design. Thirty subjects were randomly assigned to experimental and control groups. All subjects continued their customary oral hygiene procedures. In addition, the experimental group was instructed to chew on the Myo for four minutes, twice each day. Plaque Index and Gingivitis Index were assessed each time the subjects attended their scheduled orthodontic appointment. The patients failed to demonstrate any significant reduction in plaque and gingivitis development when the Myo was introduced as an additional oral hygiene measure. Some soft tissue injuries were found.
Supernumerary impactions of the mandibular cuspids and bicuspids. Case report
Authors: Yamaoka Minoru , Furusawa Kiyofumi , Okamoto Shigeo
Published: May 2009

A case involving the presence of supernumerary cuspids and bicuspids is described. The condition was probably an inherited one because of the family history and the bilateral incidence. The supernumerary teeth erupted because of alveolar resorption in which inflammatory factors probably played a role. Radiographic follow‐up of the site of supernumerary impacted teeth and alveolar resorption should be undertaken.
Comparison of silk sutures and n‐butyl‐2‐cyanoacrylate on the healing of skin wounds. A pilot study*
Authors: Giray C. B. , Sungur A. , Atasever A. , Araz K.
Published: May 2009

The synthetic tissue adhesive n‐butyl‐2‐cyanoacrylate (Histoacryl: Blue) and silk sutures were compared on the backs of guinea‐pigs as the means for closing skin incisions. On the post‐operative 3rd, 7th, 14th and 21st days, specimens from each group were obtained and evaluated under light microscopy. Sections were analysed for the degree of inflammation, giant cell reaction, fibroblastic and capillary ceil activity and were ranked statistically. The results showed that the silk sutures caused severe inflammatory and giant cell reaction when compared with Histoacryl and the healing process was slower than with n‐butyl‐2‐cyanoacrylate.
Oral submucous fibrosis. A review
Authors: Cox S. C. , Walker D. M.
Published: May 2009

Abstract— Oral submucous fibrosis (OSF) affects an estimated 2.5 million people, mostly in the Indian subcontinent. Limitation of oral opening resulting in difficulty in eating is the main presenting feature. Although nutritional deficiencies and immunological processes may play a part in the pathogenesis, the available epidemiological evidence indicates that chewing betel quid (containing areca nut, tobacco, slaked lime or other spices) is an important risk factor for OSF. Genetically determined susceptibility could explain why only a small fraction of those using betel quid develop the disease. In OSF there is an incidence of oral cancer of 7.6 per cent for a median 10 year follow‐up period. Risk markers for malignant transformation in OSF include epithelial dysplasia, silver binding nucleolar organizer region counts, and sister‐chromatid exchange frequencies; p53 tumour suppressor gene mutations may be involved in these potentially malignant changes.
Reverse smoking and palatal mucosal changes in Filipino women. Epidemiological features
Authors: Mercado‐Ortiz Georgiana , Wilson David , Jiang De‐Jun
Published: May 2009

Abstract— The habit of reverse smoking is practised in various parts of the world including the Philippines. In this pilot, community‐based, cross‐sectional study carried out in the region of Cabanatuan City in the Philippines, 61 Filipina reverse smokers and 30 Filipina conventional smokers were interviewed and clinically examined. Seven demographic variables and twelve habit variables were compared in the two study groups.

The majority (96.7 per cent) of reverse smokers exhibited palatal mucosal changes including leukoplakia, mucosal thickening, Assuring, pigmentation, nodularity, erythema and ulceration. In comparison, only 26.7 per cent of conventional smokers exhibited mucosal changes predominantly focal pigmentation and mild erythema. This difference was statistically significant at a X2 value of 47.28 (p<.001). Analysis of the other variables indicated that the two study groups differed significantly with regard to age (p<.05), educational attainment (p<.01), use of filtered versus non‐filtered cigarettes (p<.001) and duration of smoking in years (p<.01).
The place of fluoride supplements in caries prevention today
Authors: Riordan Paul J.
Published: May 2009

Abstract— There are very few scientifically good clinical trials of fluoride supplements, and those that can be considered methodologically adequate suggest that the contribution of fluoride supplements to caries prevention is slight. This may be partly a consequence of the fact that fluoride is much more widely available today than was the case a generation ago when fluoride toothpaste was not widely used and water fluoridation was not fully implemented. Although some families are conscientious in their use, compliance with fluoride supplement recommendations is generally poor over longer periods, making them a poor public health measure. There is substantial evidence that supplements cause dental fluorosis when used in accordance with recommendations for infants and small children. If the public becomes concerned about dental fluorosis as an aesthetic problem, all fluoride use may be put at risk. Supplements should no longer be recommended for caries prevention in children in areas with little fluoride in water but may be useful for persons with intractable caries risks. If supplements are recommended for children, a more cautious dosage schedule should be used. The fact that supplements have been recommended uncritically for many years on the basis of inadequate research raises questions about the standards of dental science.
Utilization of personal protective equipment in general dental practice
Authors: Lange P. , Savage N. W. , Walsh L. J.
Published: May 2009

The principles of universal precautions are central to infection control. These principles form the basis of current guidelines for the use of personal protective equipment (PPE) in dental practice. This study, which examined the patterns of use of PPE in general dental practice, was based on a postal survey of 260 dentists in Brisbane (41 per cent of the total private general practitioners in the region). Routine use of PPE was commonplace (gloves, 84.6 per cent; masks, 55.7 per cent; eyewear, 77.6 per cent), but complete compliance with current recommendations for glove handling and hand care had not been achieved. Potential problem areas in terms of attitudes to PPE were identified, as were inconsistencies in the use of PPE in both clinical and non‐clinical settings. These findings emphasize the need for further educational campaigns In practical infection control measures.
The nasal tooth: Case report
Authors: Nastri A. L. , Smith A. C.
Published: May 2009

A case of a supernumerary tooth presenting in the nasal cavity is reported. The literature is reviewed for nasal and other unusual ectopic sites of tooth eruption and other possible diagnoses for calcified intranasal masses are discussed.
Choosing Dentistry as a career ‐ A profile of entering students (1992) to the University of Sydney, Australia
Authors: Brand A. A. , Chikte U. M. E. , Thomas C. J.
Published: May 2009

The present study is an investigation of motives students have for wishing to become dentists. The study population comprised 85 first year dental students of the class of 1992 at the University of Sydney. A questionnaire which sought information on student demography, attitudes to dentistry, and motive rankings was administered. Demographic findings indicated that the majority of students came from countries in the Pacific rim and the male/female ratio was 62 to 38 per cent. Responses to the attitude questionnaire showed that Australian student motives for becoming dentists did not differ from those of students in other countries. The most predominant of these motives was to serve others, to become independent, to enjoy job satisfaction, and to acquire financial security. The least important motives were manual and communication skills, science and knowledge, and surprisingly, status and prestige. To attribute meaning and value to these motives, however, reflects inconsistencies which are expressed as contradictions between motive categories, between items within categories, and between motive categories and motive rankings.

When one considers the basis upon which career decisions are made, disparity in the findings may be attributable to a decision‐making process that rests on subjective rather than objective criteria.
Dentistry's role in obstructive sleep apnoea. Review and case report
Authors: Miles Peter G. , Nimkarn Yupares , De Leeuw Barry J.
Published: May 2009

Obstructive sleep apnoea (OSA) has been associated with many life‐threatening conditions but has only recently appeared in the dental literature. Dental appliances and orthognathic surgery are two strategies which are currently used in the treatment of sleep apnoea. This article provides a background on OSA and these treatment approaches, and discusses the potential risks and benefits of each. A case is reported to illustrate the use of a dental appliance in the treatment of OSA.
Factors affecting the amount of long‐term restorative dental treatment provided to 100 patients by 20 dentists in 3 Adelaide private practices
Authors: Hawthorne W. S. , Smales R. J.
Published: May 2009

Apart from the effects of the frequency of patient attendance for dental examination, and of a change of dentist, little is known of those factors which may influence the amount of treatment provided in dental practice. The present study investigated during 1992 the effects of seven factors on the amount of treatment provided for 100 adult patients treated by 20 male dentists over many years in three selected Adelaide private practices. The amounts of particular types of restorative treatments provided were significantly related to patient age, gender and frequency of attendance, and to practice location, change of dentist and number of changes of dentist, and to the experience or time since graduation of the dentist. These factors were of special significance for the number of crowns provided, most of which were placed in older patients by more experienced dentists. But, there was no evidence of increased numbers of direct placement restorations being received by patients who attended more frequently or who changed their dentists.
Oral conditions and their social impact among HIV dental patients
Authors: Coates Elizabeth , Slade Gary D. , Goss Alastair N. , Gorkic Ed
Published: May 2009

This study aimed to assess oral health status and the social impact of oral conditions among dental patients with HIV infection in comparison with general dental patients receiving public‐funded care in Adelaide, South Australia. DMFT and CPITN indices were recorded by one dentist at a clinic for HIV dental patients. The data were compared with information from an existing survey of general dental patients. Social impact was assessed using the Oral Health Impact Profile questionnaire and responses from HIV dental patients were compared with responses from a telephone interview survey of Adelaide residents. HIV patients were aged 21 to 49 years (median *** 34), 90.7 per cent were male and 29.6 per cent had stage 4 HIV infection. Oral candida was present among 32.0 per cent, hairy leukoplakia among 24.1 per cent, HIV gingivitis among 18.5 per cent, and HIV periodontitis among 33.3 per cent. The DMFT index and its components did not differ significantly between HIV and general dental patients, while CPITN scores were lower among HIV patients (p = 0.01). However social impact among HIV patients was frequent: 64.6 per cent reported toothache, 43.7 per cent avoided foods, and 16.7 per cent avoided going out because of dental problems. HIV patients reported significantly greater levels of social impact than the Adelaide sample (p < 0.01). Patients to this clinic frequently presented with severe and disabling oral conditions which were not adequately captured using standard clinical indices.
A comparison of patients attending general dental practices employing or not employing dental hygienists
Authors: Brown Louise Frances
Published: May 2009

Previous studies have shown that dental practices employing dental hygienists provide a more periodontally oriented mix of dental services. Little is known about differences in the characteristics of patients who attend these practices, and whether these reflect the orientation of service delivery. In this study, a comparison was made between patients attending private general dental practices employing hygienists and patients attending practices without hygienists in Adelaide, South Australia. A questionnaire was mailed to 2391 patients, and valid responses were received from 632 patients attending 12 practices employing hygienists, and 1052 patients attending 22 practices not employing hygienists. Bivariate analysis of the responses comparing the two groups of patients was conducted using ANOVA for continuous variables and chi‐square statistics for categorical variables. A multiple logistic regression model was developed to identify characteristics of patients attending practices with hygienists. Examination of significant (p<0.05) findings revealed that patients attending practices with hygienists had a higher socio‐economic status, had a more preventive pattern of use of services, had better knowledge of periodontally related topics and it was more likely that the dental profession was their main source of information on these topics. These findings indicate that patient profiles do reflect the orientation of service delivery within dental practices and raise the question of whether the denial practice alters the patient's knowledge and behaviour or whether certain patients selectively seek care from practices with hygienists.
Oral health and personnel needs in the Pacific
Authors: Finau Sitaleki A.
Published: May 2009

A regional review of oral health in the Pacific showed the major problems to be dental caries, periodontal diseases, poor dental health service management and lack of appropriate dental personnel. A strategy for training appropriate dentists to manage oral health services in the Pacific was suggested. Such a strategy must include training of ancillary and auxiliary dental health workers guided by dentists with clinical and managerial competencies. The training programme for dentists must be career‐ladder, problem‐based, and community‐oriented with competency‐based learning of a spiral of tasks with increasing sophistication. The curriculum content must contain about 50 per cent on public health and clinical aspects, respectively.
Burning mouth syndrome: Patient management
Authors: Savage Neil W.
Published: May 2009

Burning mouth syndrome is an underdiagnosed and often poorly managed oral sensory disturbance. This paper discusses the recognition of the condition and suggests clinical approaches to ensure a correct diagnosis and appropriate management. The expansion of the traditional dental rote of the dentist is reviewed in the context of overall oral and general health particularly with respect to the syndrome which demands an intensive workup, open discussions with the patient, and a carefully planned long‐term management strategy.
The use of low‐tack chewing gum for individuals wearing orthodontic appliances
Authors: Gray A. , Ferguson M. M.
Published: May 2009

A clinical study was carried out to determine the acceptability of a sugar‐free, low‐tack chewing gum by orthodontic patients undergoing fixed appliance treatment. Twenty‐five orthodontic and 25 non‐orthodontic control subjects were questioned on their preference between regular‐tack and low‐tack chewing gum. The orthodontic subjects showed a strong preference for the low‐tack gum compared with the regular‐tack gum. It was concluded that low‐tack, sugar‐free chewing gum can be used by orthodontic patients to increase saliva flow, with the potential to promote remineralization and help reduce white spot lesion formation related to fixed orthodontic appliances. This gum should also be of value in patients being treated for xerostomia who are wearing a partial denture.
Efficacy of arthroscopic surgery and midlaser treatments for chronic temporomandibular joint articular disc derangement following motor vehicle accident*
Authors: McNamara David C. , Rosenberg Ian , Jackson Peter A. , Hogben John
Published: May 2009

As a result of motor vehicle accident soft‐tissue injury, temporomandibular joint articular disc derangement may develop and persist despite symptomatic treatment and medication. This study reports the effectiveness of management directed at controlling the TMJ and masticatory neuromuscular pain dysfunction with a TMJ/interocclusal stabilization appliance, specific biofeedback and ultrasound therapy. Following these conservative measures residual articular disc derangement was present in some subjects who were offered arthroscopic surgery and infrared midlaser with TMJ/ocdusal stabilization.

Twenty subjects with residual disc derangement were randomly selected into two groups with and without arthroscopic surgery, and analyses of variance made before treatment, 12 months after conservative procedures, 3 months following arthroscopic surgery and midlaser therapy and 3 years since commencement of management. Dependent variables compared were pain‐discomfort, Clinical Dysfunction Index, articular disc derangement and maximal voluntary jaw opening. Conservative management alone provided significant reduction of pain‐discomfort and clinical dysfunction, while arthroscopic surgery resulted in significant reduction in articular disc derangement. The midlaser with TMJ/occlusal stabilization maintained significant improvement in the variables (p<0.01) for both groups. The common articular deviations in form found at arthroscopy were soft tissue alteration with hyperaemia, synovitis, synovial membrane and posterior attachment folding with connective tissue hyperplasia, and disc displacement with fibrous adhesions. The Global Status Score of pain behaviour compared with residual function, confirmed the presence of greater pain before treatment commenced.
Nonlinear Algebraic Reduction for Snap-Fit Simulation
Authors: Jorabchi Kavous , Suresh Krishnan
Published: May 2009

Snap-fits are often preferred over other traditional methods of assembly since they reduce part count, assembly/disassembly time, and manufacturing cost. A typical simulation of a snap-fit assembly entails two critical steps: contact detection and nonlinear deformation analysis, which are strongly coupled. One could rely on standard 3D contact detectors and standard 3D finite element analysis (FEA) to simulate the two steps. However, since snap-fits are slender, 3D FEA tends to be inefficient and slow. On the other hand, one could rely on an explicit 1D beam reduction for simulation. This is highly efficient for large deformation analysis, but contact detection can pose challenges. Moreover, for complex snap-fits, extracting cross-sectional properties for 1D formulation is nontrivial. We propose here a nonlinear algebraic dimensional reduction method that offers the “best of both worlds.” In the proposed method, a 3D model is used for contact detection. However, to speed-up deformation analysis, the 3D model is implicitly reduced to a 1D beam model via an algebraic process. Thus, it offers the generality of 3D simulation and the computational efficiency of 1D simulation, as confirmed by the numerical experiments and optimization studies.
Adaptive Piezoelectric Vibration Control With Synchronized Switching
Authors: Collinger J. C. , Wickert J. A. , Corr L. R.
Published: May 2009

An autonomous vibration controller that adapts to variations in a system’s mass, stiffness, and excitation, and that maximizes dissipation through synchronized switching is described. In the model and laboratory measurements, a cantilever beam is driven through base excitation and two piezoelectric elements are attached to the beam for vibration control purposes. The distributed-parameter model for the beam-element system is discretized by using Galerkin’s method, and time histories of the system’s response describe the controller’s attenuation characteristics. The system is piecewise linear, and a state-to-state modal analysis method is developed to simulate the coupled dynamics of the beam and piezoelectric circuit by mapping the generalized coordinates between the sets of modes for the open-switch and closed-switch configurations. In synchronized switching control, the elements are periodically switched to an external resonant shunt, and the instants of optimal switching are identified through a filtered velocity signal. The controller adaptively aligns the center frequency of a bandpass filter to the beam’s fundamental frequency through a fuzzy logic algorithm in order to maximize attenuation even with minimal a priori knowledge of the excitation or the system’s mass and stiffness parameters. In implementation, the controller is compact owing to its low inductance and computational requirement. The adaptive controller attenuates vibration over a range of excitation frequencies and is robust to variations in system parameters, thus outperforming traditional synchronized switching.
Parameter Estimation by Parameter Signature Isolation in the Time-Scale Domain
Authors: Danai Kourosh , McCusker James R.
Published: May 2009

It is shown that output sensitivities of dynamic models can be better delineated in the time-scale domain. This enhanced delineation provides the capacity to isolate regions of the time-scale plane, coined as parameter signatures, wherein individual output sensitivities dominate the others. Due to this dominance, the prediction error can be attributed to the error of a single parameter at each parameter signature so as to enable estimation of each model parameter error separately. As a test of fidelity, the estimated parameter errors are evaluated in iterative parameter estimation in this paper. The proposed parameter signature isolation method (PARSIM) that uses the parameter error estimates for parameter estimation is shown to have an estimation precision comparable to that of the Gauss–Newton method. The transparency afforded by the parameter signatures, however, extends PARSIM’s features beyond rudimentary parameter estimation. One such potential feature is noise suppression by discounting the parameter error estimates obtained in the finer-scale (higher-frequency) regions of the time-scale plane. Another is the capacity to assess the observability of each output through the quality of parameter signatures it provides.
Repetitive Control System Under Actuator Saturation and Windup Prevention
Authors: Sbarbaro D. , Tomizuka M. , León de la Barra B.
Published: May 2009

This work provides an analysis of the steady state response of a prototype repetitive controller applied to a class of nonlinear systems, i.e., systems with actuator saturation. First, it is shown that the steady state solution of the closed loop nonlinear system can be obtained by an iterative Picard process, which establishes the periodic nature of the steady state solution. Second, the conditions for obtaining bounded steady state responses are analyzed for a saturating nonlinearity commonly found in mechatronic applications. Valuable insight is provided into the effects of input signals and saturating actuators on the closed loop performance of a prototype repetitive controller. In order to improve the transient closed loop response, a simple antiwindup strategy tailored to repetitive controllers is proposed.
Kinematics and Dynamics of a Self-Stressed Cartesian Cable-Driven Mechanism
Authors: Behzadipour Saeed
Published: May 2009

A novel hybrid cable-driven mechanism with Cartesian motion is introduced. It consists of a rigid-link Cartesian mechanism and a cable drive system with stationary actuators to provide the motion. The cable drive system is self-stressed meaning that the tension in the cables required to keep them taut is provided internally and hence does not depend on either actuation redundancy or external sources such as gravity. This keeps the number of actuators at minimum and also eliminates the static loading of actuators as well as redundant work. The kinematic analysis of the mechanism is presented. The forward and inverse kinematic solutions are found and shown to be linear and pose independent. Also the stiffness of the mechanism induced by the compliance of the cable is analyzed to find the weakest stiffness. For this purpose, a parameter called “compliance length” is defined and used. Compliance length presents the stiffness of the mechanism by the length of the cable with the same stiffness. It makes the analysis independent from the design and the properties of the cable and can be quite useful in the design process. Finally, two dynamic models are given for the mechanism depending on whether or not the cable is stretchable and the properties of each model are discussed.
Determination of Basic Machine-Tool Settings for Generation of Spiral Bevel Gears From Blank Data
Authors: Fuentes Alfonso , Gonzalez-Perez Ignacio , Litvin Faydor L. , Hayasaka Kenichi , Yukishima Kenji
Published: May 2009

Many researchers and gear designers are applying their own methods to obtain appropriate machine-tool settings for each case of design, according to their own experience, manufacturing machines and type of generating process. In this paper, the analytical determination of basic machine-tool settings for generation of spiral bevel gears from blank data is proposed. Determination of gear machine-tool settings is carried out through an analytical procedure that will allow to obtain identities between gear machine-tool settings and blank data of the spiral bevel gear drive. In this work, the face-milling generation process has been considered. The blank data that have been considered are: number of teeth of the pinion and the gear, module, spiral and pressure angles, face width, shaft angle, depth factor, clearance factor, and mean addendum factor. These basic starting data are known or can be established following the directions of the Standard ANSI/AGMA 2005-D03. Once the basic gear machine-tool settings are determined, the existing approach of local synthesis is applied to determine the pinion machine-tool settings that provide the desired conditions of meshing and contact of the gear drive. The developed theory is illustrated with numerical examples.
An Alternative Method for Evaluating Gear Tooth Surface Geometry Based on Synchronous Average of Vibration of a Gear Pair
Authors: Ratanasumawong Chanat , Matsumura Shigeki , Houjoh Haruo
Published: May 2009

Low noise and vibration in the gearing operation is always required. Inspection by measuring gear tooth surface is a common way to investigate the source of noise and vibration. However many problems probably occur during assembling procedure, or are attributed to the bearing condition of the tooth pairs that certainly cannot be detected when inspecting each gear separately. In this paper, the newly developed method to evaluate gear tooth surface geometry based on vibration measurement is proposed. This method can be done in field. Moreover measured vibration also relates directly with the tooth bearing condition. In this method, vibration of the gear pair is measured and processed by the synchronous averaging technique to extract only the signal of interest. Then the system transfer function obtained experimentally is applied to the averaged-meshing vibration to estimate vibration excitation. Consequently tooth surface geometry directly relating with the vibration excitation can be inversely evaluated. The effectiveness of this method was verified by many experiments done by measuring the vibration of helical gears with various kinds of tooth surface forms at various operating conditions. The evaluated vibration excitations were plotted in the polar coordinate. The changes of amplitude and phase angle of the second order components were found to be suitable and could be used as an indicator to evaluate gear tooth surface form.
Housing Influence on Churning Losses in Geared Transmissions
Authors: Changenet C. , Velex P.
Published: May 2009

In a previous paper, a series of analytical formulas were presented enabling accurate predictions of churning losses for one gear which is typical of automotive transmission geometry. However, this formulation does not take into account the influence of flanges and deflectors. In order to extend the proposed methodology, a test rig has been set up in which several moveable walls can be inserted thus making it possible to modify the radial and axial clearances, i.e., the distances between the tested gear and the walls. Based on a qualitative evaluation of the various fluid flow regimes possible in gearboxes, the influence of the global volume of the oil sump on churning losses is analyzed. By considering a number of flange and deflector arrangements, the following conclusions are drawn: a) radial clearances have a weaker influence than axial clearances and, b) power losses can be minimized by properly chosen axial clearances.
An Experimental Investigation of the Influence of Manufacturing Errors on the Planetary Gear Stresses and Load Sharing
Authors: Ligata Haris , Kahraman Ahmet , Singh Avinash
Published: May 2009

In this paper, results of an experimental study are presented to describe the impact of certain types of manufacturing errors on gear stresses and the individual planet loads of an n-planet planetary gear set (n = 3 to 6). The experimental set-up includes a specialized test apparatus to operate a planetary gear set under typical speed and load conditions and gear sets having tightly controlled intentional manufacturing errors. The instrumentation system consists of multiple strain gauges mounted on the ring gear and a multi-channel data collection and analysis system. A method for computing the planet load sharing factors from root strain time histories is proposed. Influence of carrier pinhole position errors on gear root stresses are quantified for various error and torque values applied to gear sets having 3 to 6 planets. The results clearly indicate that manufacturing errors influence gear stresses and planet load sharing significantly. Gear sets having larger number of planets are more sensitive to manufacturing errors in terms of planet load sharing behavior.
Reliability Prediction of Gear Transmissions
Authors: Starzhinsky Victor E. , Soliterman Yuri L. , Goman Arcadi M.
Published: May 2009

Service life of any individual transmission gears is known to represent a stochastic value. The methods of predicting gearing reliability as a relation of the acting and permissible stress distributions are described. The probability of transmission gear non-failure service is considered with most characteristic failure modes such as the tooth breakage and plastic deformation of the tooth working surfaces under a short-term maximal dynamic loading and the bending and contact fatigue under prolonged service loads. The employment of different statistical distribution parameters for gear reliability prediction is considered. A practical example of gearing reliability prediction is given.
Composite Analysis Method of Tooth Contact Load Distribution of Helical Gear
Authors: Miyoshi Yoshikazu , Tobisawa Keiichiro , Saiki Kohei
Published: May 2009

As demand for the performance improvement of automotive transmission gears increases, gear design is required that achieves high strength, low noise and high efficiency simultaneously. In addition, for high performance it is important not only to select good gear dimensions, but also to improve the tooth contact load distribution which depends on the tooth flank shape and assembly error of the gear pair. Traditional analysis methods calculate the tooth contact load distribution with integral equations that consist of the effect function of bending deflection and that of compressive deformation caused by the contact of gear teeth. However, the complicated integral equations make it difficult to instantly obtain proper results for some tooth flanks distorted by heat treatment and repetition calculation may not converge especially in light load conditions. This paper proposes a new composite analysis method which quickly calculates the tooth contact load distribution of designed or manufactured tooth flanks of helical gears in any load condition. The analytical process consists of three stages: (1) for each flank shape of a gear pair, the three-dimensional relative tooth flank shape is calculated from the actual tooth flank shape and assembly error, and the equivalent tooth profile error of the three-dimensional relative tooth flank shape is obtained by the static deflection which depends on input torque, (2) the static deflection distribution and share load on each line of contact are calculated with the obtained equivalent tooth profile error and the variable stiffness of the involute tooth pair, (3) an integral equation that consists of bending deflection and compressive contact deformation of the gear teeth is solved to obtain the tooth contact load distribution. In practical applications, the tooth contact load distribution is used to output the tooth contact pattern, tooth contact and root bending stresses, and transmission error. The prediction of tooth contact stress and transmission error contributes to the improvement of the pitting strength and gear noise of several transmissions.
Determination of Parametric Resonances in Distributed Parameter Systems Using Frequency Analysis
Authors: Lee Yong-Kwan , Chechurin Leonid S.
Published: May 2009

Theoretical analysis of parametric instability for the control systems with distributed parameters shall be given. The approach to the solution of such systems can be composed of two parts, i.e. modeling and estimation of the distributed parameters and instability estimation of the periodical time-variant elements using parametric circumference. A control system with mechanical distributed parameters such as robot manipulators is introduced as an example. Theoretical analysis shows that the parametric instabilities occur by digital controllers or time-varying elements which excite the resonance regions of distributed parameters. An electro-mechanical transformer which consists of constant current motor and synchronous generator is applied as another example. Inductance between stator windings and rotor of the synchronous generator serves as a periodical time-varying parameter and long electrical line plays a role of an element with distributed parameters. Instability condition of the transformer rotation owing to the parametric resonance excitement was obtained.
Numerical Simulation and Experimental Research on Pedestal Looseness of a Rotor System
Authors: Ma Hui , Yao Hong Liang , Ren Zhao Hui , Wen Feng , Wen Bang Chun
Published: May 2009

The mechanical model of looseness of fastening bolt on the bearing pedestal is set up based on the project practice. Using the nonlinear oil-film model put forward by Adiletta, the dynamic characteristics were investigated by numerical Runge-Kutta method. At last, the experiment is performed to investigate the pedestal looseness by a test rig and the fault signals are analyzed by the spectrum cascade and reassigned wavelet scalogram. Numerical simulation and experiment all show that system motion state changes frequently with the increase of the rotating speed. And the experimental results coincide with the simulation results.
Optimisation of Periodic Structure Subject to Parametric Alteration
Authors: Chen Yu-Ming , Wu Teng-Yuan , Chen Lai-Sheng
Published: May 2009

The dynamic responses of repetitive system are relatively sensitive to modification where slight changes in the geometric parameters can destroy the structure symmetry. This paper treats antenna structure as a study example and investigates its vibration behaviors subject to parametric changes. An analytically derived computational model based on the Rayleigh-Ritz method for modeling the periodic structure is produced. This is particularly useful in treating continuous structure with non-uniform mass and/or stiffness properties. The antenna structure is represented by a number of cantilever beams elevated at an angle and built-in into a hub and coupled by springs. This work performs two optimizations separately: (a) by optimizing the location of equally weighted lumped masses along each cantilever beams and, (b) optimizing the location of springs. Effects of altering these parameters with the objective function of minimizing the structure vibration is addressed in this work.
Human Robot Collaboration: An Augmented Reality Approach—A Literature Review and Analysis
Authors: Green Scott A. , Billinghurst Mark , Chen XiaoQi , Chase J. Geoffrey
Published: May 2009

Future space exploration will demand the cultivation of human-robotic systems, however, little attention has been paid to the development of human-robot teams. Current methods for autonomous plan creation are often complex and difficult to use. So a system is needed that enables humans and robotic systems to naturally and effectively collaborate. Effective collaboration takes place when the participants are able to communicate in a natural and effective manner. Grounding, the common understanding between conversational participants, shared spatial referencing and situational awareness, are crucial components of communication and collaboration. This paper briefly reviews the fields of human-robot interaction and Augmented Reality (AR), the overlaying of computer graphics onto the real worldview. The strengths of AR are discussed and how they might be used for more effective human-robot collaboration is described. Then a description of an architecture that we have developed is given that uses AR as a means for real time understanding of the shared spatial scene. This architecture enables grounding and enhances situational awareness, thus laying the necessary groundwork for natural and effective human-robot collaboration.
Specialised Image Capture Systems for a DIET Breast Cancer Screening System
Authors: Hann Christopher E. , Chase J. Geoffrey , Berg Crispen , Brown Richard G. , Elliott Rodney B. , Chen XiaoQi
Published: May 2009

Digital Image-based Elasto-Tomography (DIET) is an emerging technology for non-invasive breast cancer screening. This technology actuates breast tissue and measures the surface motion using digital imaging technology. The internal distribution of stiffness is then reconstructed using Boundary Element or Finite Element Methods (FEM or BEM). However, obtaining accurate imaging at high frequency and high resolution in terms of numbers of pixels is challenging if enough accuracy is to be obtained in the motion sensing to deliver a useful result. The overall focus of such mechatronic and digitally centred systems is on providing a low-cost, radiation dose-free and portable screening system capable of screening numerous patients per day — in direct contrast to current low throughput, non-portable and high cost x-ray and MRI based approaches. Thus, DIET technology relies on obtaining high resolution images of a breasts surface under high frequency actuation, typically in the range of 50–100Hz. Off-the-shelf digital cameras and imaging elements are unable to capture images directly at these speeds. A method is presented for obtaining the required high speed image capture at a resolution of 1280×1024 pixels and actuation frequency of 100Hz. The prototype apparatus presented uses two imaging sensors in combination with frame grabbers and a dSpace™ control system, to produce an automated image capture system. The system integrates a precision controlled strobe lighting system to selectively capture sinusoids at different points in the sinusoidal cycle of response. The final working system produced images that enabled effective 3D motion tracking of the surface of a silicon phantom actuated at 100Hz. The surface of the phantom was strobed at pre-selected phases from 0 to 360 degrees, and an image was captured for each phase. The times at which image capture occurred were calculated for a phase lag increment of 10 degrees resulting in an image effectively every 0.00028s for the actuator cycle of 0.01s. The comparison of the actual trigger times and pre-selected ideal trigger times gave a mean absolute error of 1.4%, thus demonstrating the accuracy of the final system. Final validation is performed using this system to track motion in a silicon gel phantom. The motion is tracked accurately using a novel Euclidean Invariant signature method. Both cameras delivered similar results with over 90% of points tracked to within 1–2%. This level of accuracy confirms the ability to effectively accurately reconstruct the stiffness as validated in other related studies.
A Concept for a Material That Softens With Frequency
Authors: Prasad Jitendra , Diaz Alejandro R.
Published: May 2009

This work presents design concepts to synthesize composite materials with special dynamic properties, namely, materials that soften at high frequencies. Such dynamic properties are achieved through the use of a two-phase material that has inclusions of a viscoelastic material of negative elastic modulus in a typical matrix phase that has a positive elastic modulus. A possible realization of the negative stiffness inclusion phase is presented. A numerical homogenization technique is used to compute the average viscoelastic properties of the composite. The method and the properties of a composite material designed with it are demonstrated through an example.